Dip AVN Cases

Dip AVN Case Study

Diane Wood — Sun, 09 Oct 2016 23:40:39 GMT

Current Revision posted to Dip AVN Cases by Diane Wood on 10/9/2016 11:40:39 PM

The Author
Geraldine Coles stumbled into the veterinary nursing profession, having previously trained as a geologist. She joined the PDSA as a trainee in 1994, qualifying as a VN in 1997. She gained the Diploma AVN in 2000, in the process winning the BVNA Award for the highest marks achieved in the examination. She currently works at the PDSA in Bow, where she enjoys the freedom that the charity gives her to practice her skills. In particular, she finds the extra responsibility, huge work load and variety both challenging and exciting.

Author's note
The following case studies are one example of the content and type of format acceptable to the examiners. There are, of course, other types of formats which are equally acceptable. Those that follow illustrate my own personal choice.

My own experience has shown me that it is not too advisable to write up all your cases too early, as you will probably find yourself re-writing them as your knowledge accumulates.

If you are like me though, you will probably rewrite them about five times anyway!

Good luck!

Publisher's Note
Please note that it has not been possible to reproduce the x-ray images that appear in the following case study to the same high standard as the originals. They are therefore for illustrative purposes only. We hope to be able to reproduce them more clearly in the future.

Our congratulations to Geraldine, and sincere thanks for allowing us to publish her work on this website.

Diploma

Anonymous — Thu, 13 Nov 2014 20:39:44 GMT

Current Revision posted to Dip AVN Cases by Anonymous on 11/13/2014 8:39:44 PM

Case 1. Pancarpal arthrodesis

Sam Young RVN MBVNA — Thu, 23 Sep 2010 16:46:37 GMT

Current Revision posted to Dip AVN Cases by Sam Young RVN MBVNA on 9/23/2010 4:46:37 PM

Pancarpal Arthrodesis Using Bone Graft From Proximal Humerus

OWNER:	FIELD	ANIMAL:	MAX
SPECIES:	DOG	BREED:	BORDER COLLIE
AGE:	6 YEARS	SEX:	MALE
WEIGHT:	25.6 KG	CONDITION:	GOOD

Clinical History
Max was presented unable to weightbear on the right foreleg, having jumped over a wall. The right carpus was swollen and painful on palpation. Radiographs were taken the following day, under general anaesthesia. Nothing abnormal was detected on the radiographs (see right) but on palpation it was found that the right carpus was unstable.

A dressing with gutter splints was applied for a total of 8 weeks. This proved to be unsuccessful and the dog still had a severe plantigrade stance at the end of this period. The options were discussed with the owners and it was decided that a pancarpal arthrodesis would be the best course of action. The owner was warned of the risks associated with general anaesthesia..

On 13/5/98 the dog was admitted for surgery, having been starved overnight with access to water until 3 hours prior to surgery. A pre-anaesthetic clinical examination revealed no cardiovascular or thoracic abnormalities. Temperature was 38.1 C, pulse 127, respiration 27 per minute.

The owner signed a consent form and premedication was given with 1mg acepromazine (ACP, C Vet) by subcutaneous route 35 minutes prior to general anaesthesia. Analgesia and antibiotics were also given at this time, with 4mg morphine sulphate (Evans) by intra- muscular route, 100mg carprofen (Zenecarp, C Vet) and 450mg ampicillin (Duphacillin, Solvay Duphar Vet) by subcutaneous route. A 19 gauge intra-venous catheter was placed aseptically into the left cephalic vein and a slow infusion of 1 litre of compound sodium lactate (Hartmann's, Intraven) was started.

Anaesthesia was induced using 300 mg thiopentone sodium 2.5% (Intraval Sodium, Rhone Merieux) by intra-venous route, followed by intubation with a 12 cuffed endotracheal tube. A parallel semi-closed Lack circuit with 4L nitrous oxide, 2L oxygen and halothane was used to maintain anaesthesia.

Pre-surgical preparation
The dog was placed in left lateral recumbency and the whole of the right foreleg, including shoulder, right of sternum and brisket was clipped as in the first paragraph of Appendix 1. The dog was moved to theatre and placed in left lateral recumbency, where preparation of the skin around the right proximal humerus was completed, as in the second paragraph of Appendix 1. Four drapes were applied in a quadrant, leaving access to the right lateral proximal humerus only, the rest of the dog being covered by the drapes.

A standard kit, as listed in Appendix 2, was laid out with additional instruments as listed in Appendix 3.

Surgical procedure - harvest of the bone graft
An incision was made across the lateral approach to the greater tubercle of the right humerus through the skin and fascia. The deltoideus muscle was retracted to expose the area of bone just distal to the greater tubercle. An electric drill, fitted with a 4.5 mm bit, was used to drill a hole into the cancellous bone. A Volkmann scoop was used to harvest the graft bone. A total of ten scoops were put onto a saline soaked swab, which was carefully wrapped and put to one side in a sterile bowl.

The wound was closed using 3.5m chromic catgut (Ethicon) in a simple continuous suture pattern for both the muscle and subcutaneous tissue, and the skin was closed with simple interrupted sutures using 3m multifilament polyamide (Supramid, BK Vet Products).

The dog was then placed in ventral recumbency with a large cradle supporting the thorax. The right leg was tied, by the digits, to a drip stand and the skin from the bandage on the digits to the proximal radius and ulna was prepared as in Appendix 1. The surgeon and assistant changed surgical gloves. A new size 10 scalpel blade and new swabs were exchanged for the contaminated ones. A nurse released the leg from the drip stand (only holding the bandaged digits) and then held the leg proximal to the elbow to allow the surgeon to wrap the digits with a sterile bandage.

A large drape was placed under the right leg covering all parts of the dog caudal to the right axilla, including all of the left leg. A second drape was placed overlapping the first on the left side and laying over the dorsal aspect of the proximal radius and ulna on the right side. A third drape was laid to overlap both the other drapes on the right side, forming a triangle through which the right leg protruded. The last drape was laid approaching from the cranial direction and wrapping round the proximal radius and ulna. All drapes were secured with towel clips. The only part of the dog left exposed was the right leg (distal to the proximal radius and ulna), which lay, dorsal aspect uppermost, on the drapes covering the ventral abdomen. This was followed by a fenestrated barrier drape through which the limb was passed. See Figure 1.

The surgeon instructed the theatre nurse to apply a tourniquet to the distal humerus and the time was noted, as the surgeon requested that the tourniquet should only remain in place for 20 minutes.

Surgical procedure - pancarpal arthrodesis
An incision through the skin and fascia was made on the mid-dorsal surface from the distal third of the radius, across the carpus to the distal third of metacarpal III. The incision was made lateral to the accessory vein, following the vein. Gelpi retractors were used to retract the accessory vein and the common digital extensor tendon. The joint was then exposed by incising through the deep fascia. At this time a scalpel was used to sever the proximal insertions of the tendons of the extensor carpi radialis at metacarpals II and III, and the tendon of the abductor pollicis longus muscle. The joint capsule was then cut using a scalpel. The carpus was then held in the flexed position to locate the joint spaces between the radiocarpal joint; middle carpal joint and the carpometacarpal joints. An osteotome was used to debride the articular cartilages in order to provide space for the bone graft material to be inserted. Holes were then drilled in the distal radius to promote vascularisation of the area.

The plate was placed in position for a trial fitting. The fifth hole (of the nine holes) was located over the radial carpal bone. The carpus joint was proud and therefore only the end of the plate was in contact with the metacarpal. Plate benders were used to bend the plate midway along it's length. Rongeurs were also used to debride tissue from the dorsal carpus. On a second fitting the plate made contact with bone along the entire length of the plate. NOTE - at this time the tourniquet was removed.

The plate was positioned and the first hole to be drilled was into the radial carpal bone as this was the smallest bone. A 2.7 mm bit was used and 3.5 mm x15 mm Sherman screws were used for holding the plate in place. The order in which the screws were fitted is as shown in Diagram 1. After the first three screws had been placed the bone graft material was packed in the joint spaces.

The ninth hole was left unscrewed, as it appeared that it was aligned over the carpo- metacarpal joint space. The incision was then closed using 3m Supramid with simple interrupted sutures. Post-operative radiographs were then taken to check the alignment of the plate, (see radiograph pictured left). These were satisfactory - See discussion.

Post-operative management.
A short palmar moulded cast was applied to the leg. This was achieved by applying a sterile, nonadherent dressing to the wound, followed by a layer of conforming bandage, a layer of cotton wool and a further layer of conforming bandage. Delta-lite 7.5 cm casting tape was used to form a cast from the mid radius/ulna to claws. The cast had set after 8 minutes and was then split medially and laterally with an oscillating saw. The dressing was then re-applied with cotton wool padding in between all the toes, (including dew claw), using the caudal half of the cast as a splint. Care was taken to ensure adequate padding was in place under all edges of the cast to avoid tissue damage.

Recovery from anaesthesia was uneventful. The dog seemed uncomfortable during the post-operative period and the morphine was repeated after four hours. The dog went home the following day with Zenecarp 50mg tablets, to be given one twice daily with food.

The tubercle graft site wound healed well after initial swelling and a small amount of serous discharge. The dressing on the carpus was changed every 3 days initially, followed by weekly changes and was taken off after four weeks due to the skin around the dew claw being sore, despite padding.

Five weeks after surgery some swelling appeared over the carpus and the dog appeared to be in pain. A subsequent radiograph showed osteolysis around the proximal screw. See radiograph no. 3 pictured right.

A five week course of clindamycin 150mg (Antirobe, Upjohn), one twice daily, resolved the infection and the dog was walking well. The plate was expected to stay in place for approximately one year, until complete fusion of the joint had taken place. Ten months after surgery the dog became lame again and was admitted for radiography, followed by removal of the plate. Radiography showed complete fusion of the carpometacarpal joint and partial fusion of the radiocarpal joint. See Radiograph no. 4 pictured above. On removal of the plate it was noted that the distal 5 screws were loose. A post-operative Robert Jones support dressing was applied for 3 weeks. The dog is walking well now and the carpus has remained stable.

Discussion
In this case, after failure to respond to conservative treatment, surgery was indicated to restore the dog's mobility and to alleviate pain. This was achieved and can therefore be considered as successful surgery.

Hamish R Denny FRCVS (JSAP 32:329, 1991) suggests that the skin incision should be made down the medial side of the leg, curving laterally over the distal metacarpals. This ensures that the skin closure does not occur over the plate. However, in this case healing of the wound did not appear to be compromised despite being located directly over the plate. He also stated that the tourniquet could be left in place for one hour.

Packing of the joint spaces with graft material, after placement of the plate, proved difficult as the plate obstructed access. Hamish Denny recommends packing the joint spaces before fitting of the plate, while the carpus is partially flexed. This would have enabled more material to be inserted throughout all the joint spaces, and could account for incomplete fusion of the joint. A barrier drape is essential during orthopaedic surgery to prevent bacterial strike through ocurring, due to wet drapes.

An attempt could possibly have been made to drill and screw the last hole as the post-operative radiograph showed that the hole was, in fact, aligned over the proximal end of the metatarsal, although this could have resulted in the screw working loose if there wasn't adequate bone present. External post-operative support is essential to protect the plate from excessive bending forces until fusion has begun, and the gutter splint dressing should have ideally stayed on for 6 - 8 weeks.

When the post-operative infection round the proximal screw was diagnosed, ideally a swab could have been taken for a bacterial culture and sensitivity test to ensure that an effective antibiotic was prescribed. However, Antirobe was selected and did prove to be effective in eliminating the infection.

The combination of Zenecarp and morphine was an adequate choice of analgesia for this procedure, as orthopaedic surgery is extremely painful. Morphine is an opiate and therefore a potent analgesic, especially useful during anaesthesia to reduce the amount of halothane used. It also provides good analgesia in the immediate post-operative period, which is very important when using thiopentone as it has an ant-analgesic effect for up to 7 hours (the elimination half-life of the drug in the dog). Morphine lasts only 4 hours and therefore had to be repeated. Zenecarp is a non steroidal anti-inflammatory drug (NSAID), and therefore not as potent as morphine, but is considered to be the most potent of the NSAID's and a good choice as a post-operative analgesic for the following reasons: Zenecarp injectionable lasts for 24 hours, is the only NSAID considered safe to be given peri-operatively as it does not reduce the body's production of prostaglandins (which play a part in the protection of the GI tract and inadequate perfusion within the kidneys), and Zenecarp tablets enable the owner to continue administering analgesia at home.

Post-operative nursing of this case involved 8 dressing changes, management of the leg to avoid sores, initial wound management to avoid infection, observation of the leg, checking temperature and general health of the dog and advice to the client on restriction of exercise, care of the dressing and suitable post-operative diet.

The role of the owner is extremely important in a case where long-term post-operative management is needed and this commitment must be fully understood by the client before this type of surgery is carried out. In this case, despite our best efforts, the owner did not follow our advice and during the first eight weeks after the initial injury the dog was presented every 3 to 4 days with a broken gutter splint due to the dog being allowed to run free with no restriction of exercise. Had the owner followed our repeated advice surgery may not have been necessary. Unfortunately, this attitude continued into the post-operative period and the consequence of this could well have been amputation. However, despite not presenting the dog at the correct time for dressing changes and not restricting exercise the leg eventually healed.

References:
Brinker, Piermattei; Small Animal Orthopedics & Fracture Treatment, W B Saunders & Co, 2nd Ed, p 530 - 535, 1990.
Journal Small Animal Practice, 32:329, 1991.
BSAVA Manual of Anaesthesia, 3rd Rev Ed, p 53, 1992.
Small Animal Surgery, Fossum, Mosby, p938 - 942, 1997.

Case 1. Splenectomy

Anne-Marie Lebis — Fri, 16 Apr 2010 20:45:17 GMT

Current Revision posted to Dip AVN Cases by Anne-Marie Lebis on 4/16/2010 8:45:17 PM

OWNER	PIERCE	ANIMAL:	JASPER
SPECIES:	DOG	BREED:	XB
AGE:	10 YEARS	SEX:	MALE NEUTER
WEIGHT	29 KG OBESE	CONDITION:	BRIGHT

Clinical History.
The dog was first presented for anal adenomas which were subsequently removed under general anaesthesia. A routine palpation of the abdomen whilst the dog was under anaesthesia revealed a mass which was diagnosed as a splenic tumour. As the owners had not given consent for this surgery the dog was booked in for removal of the spleen 2 weeks later, as the dog was not showing any clinical symptoms consistent with a splenic tumour. A blood sample to measure packed cell volume was taken pre-operatively and this was recorded at 0.47 L/L, which was normal. The owners were warned of the risks associated with general anaesthesia of an old, obese dog undergoing a splenectomy and were required to sign a consent form to allow general anaesthesia and surgery.

Pre-anaesthetic clinical examination and premedication.
The dog was admitted for general anaesthesia having been starved for 12 hours with access to water until 2 hours prior to premedication. A clinical pre-operative check revealed no thoracic or cardiovascular abnormalities. Pulse was 92 per minute, respiration 34 per minute and temperature recorded at 38.8 C. Mucous membranes (m/m) were pink and capillary refill time (CRT) was just under 1 second. Premedication was given with 0.6 mg of acepromazine (ACP C Vet) by subcutaneous route and 7 mg of morphine (Morphine Sulphate, Evans) by intramuscular route. A 20 guage intravenous catheter was placed aseptically into the right cephalic vein and an infusion of Hartmanns crystalloid was started at a rate of 10 mls/kg/hour. One hour later the premedication seemed to have had no effect. The dog was still excitable and quite aggressive, needing to be muzzled in order to carry out induction, having already bitten someone without warning whilst being taken out of the kennel.

Induction.
Induction was achieved with 110 mg of propofol (Rapinovet, Schering-Plough) by slow intravenous injection given to effect through the catheter, and a cuffed 12 mm endo- tracheal tube was used to intubate the dog. A semi-closed parallel Lack circuit with a 4L resevoir bag was used with flow rates of 4L nitrous oxide and 2L oxygen, and halothane was used as the inhalation agent. Additional analgesia was given after induction with 125 mg carprofen (Rimadyl, Pfizer) by subcutaneous route. Antibiotic cover was provided with 225 mg ampicillin (Norobrittin, Norbrook) by subcutaneous route.

Radiography.
A radiograph of the thorax in right lateral recumbency was taken to ensure that no metastases had occurred. The radiograph revealed no visible abnormalities and the dog was prepared for surgery and a total splenectomy was performed.

Maintenance of anaesthesia.
For a detailed account of general anaesthesia see attached anaesthetic record. Duration of anaesthesia was 150 minutes with the dog able to walk 40 minutes after the end of anaesthesia.

After induction the dog was placed in dorsal recumbency and it was noticed after a few minutes that the pulse oximeter reading had fallen to 82% (hypoxaemia) and that the mucous membranes (m/m) were beginning to appear red. This indicated that the dog was hypoventilating. Neither a Bains circuit or a ventilator was available so the nitrous oxide was turned off and the oxygen increased to 8 L. Intermittent positive pressure ventilation (IPPV) was carried out and the pulse oximeter rose to 97% and the m/m returned to pink. At the time of the first incision the heart rate rose to 158 bpm in response to the surgical stimulation. The halothane was increased to 2% and the nitrous oxide was put back on at the previous flow rates, and IPPV was continued for the duration of anaesthesia 5 times a minute to assist with the dog's spontaneous respiration. This kept the pulse oximeter readings above 90% (the level at which hypoxaemia occurs). The heart rate continued to be quite erratic throughout the anaesthetic, although the ECG showed normal complexes and rhythm. The halothane remained at 2% for most of the duration of anaesthesia. The respiration remained fairly constant around 30 to 35 per minute. Extubation took place 5 minutes after cessation of anaesthesia.

Post-operative recovery.
The dog was very excitable on recovery and only received 700 mls of the Hartmann's as it continually tied the giving set in knots. The morphine was repeated after 4 hours. A PCV taken the following morning recorded at 0.36 L/L and the dog had slightly pale m/m's. However, it was eating and temp was normal so it was sent home with 10 Rimadyl 50 mg tablets to be given one twice daily with food, and 10 Ampicillin capsules also to be given one twice daily to start immediately. A post-operative check two days later revealed a PCV of 0.37 L/L and the dog was very bright and eating well. Sutures were removed at 10 days and the PCV was last recorded at 0.42 L/L.

Discussion.
Anaesthetic protocols should always be planned to suit the animal's condition at the time of surgery and the procedure to be performed. In this case the dog was not collapsed, as the spleen had not ruptured prior to surgery. However, a splenectomy can result in several complications under general anaesthesia and special consideration should be given to anaesthetic protocols to minimise the risks. In addition this dog was obese which also adds to the possible anaesthetic risk. Firstly, a pre-operative PCV was taken to be able to compare with post-operative PCV's, as anaemia can be a post-operative complication. Also, anaemia would preclude the use of nitrous oxide (if severe). Anaemia would also affect the accuracy of the pulse oximeter, as it measures the levels of oxygen saturation of the haemoglobin, not whether there are enough red cells to carry sufficient oxygen to the tissues. ACP was given as a premedication but it probably would have been wise not to use it for two reasons. Firstly, one side effect of ACP is to produce hypotension, which in itself could be one of the complications of removing a spleen which contains a large volume of blood. The second reason for not using ACP is that it is not usually an effective sedative for aggressive animals. In fact it can release the inhibtions that prevent a dog from biting, which is what appeared to happen in this case. However, as the dog did not give any indication of aggression prior to premedication and the owner made no mention of this behaviour this was totally unforeseen. One advantage of ACP is that it protects the heart from catecholamines. Choice of induction agent and maintenance agent is important for splenectomies as they are at risk from premature ventricular contractions (PVC) during general anaesthesia. PVC's can result from drugs, hypoventilation, hypoxaemia, pulmonary and myocardial contusions following trauma, and inadequate depth of anaesthesia.Thiopentone sensitises the myocardium to catecholamines which increases the risk of PVC's, and also depresses the respiratory and cardiovascular systems, so this agent should be avoided. Although propofol also depresses the respiratory and cardiovascular systems it does not sensitise the myocardium as much as thiopentone, and would be preferred to thiopentone. Diazepam (0.25 mg/kg) could be given intravenously before the propofol, which would reduce the amount of propofol needed for induction. Or ketamine (5 mg/kg) and diazepam (0.25 mg/kg) in the same syringe could have been given intravenously as an alternative induction agent. The advantage of using ketamine is that it does not produce as much cardiovascular depression. One third to one half of the dose should be given, followed by titration to effect after 30 seconds to allow intubation of the trachea. The disadvantage of using ketamine is that monitoring of depth of inhalation anaesthesia cannot be assessed using eye position, and monitoring instruments would be necessary to avoid overdose. Thiopentone (a barbiturate) also causes congestion of the spleen with blood, which would increase the risk of hypovolaemia and hypotension when the spleen was removed, so this agent is unsuitable for this procedure. A disadvantage of using propofol as an induction agent is that elimination of the drug can occur quite suddenly and consequently the depth of anaesthesia can change rapidly. This did occur with this dog just prior to the first incision and, as the record shows, increased respiration and pulse rate indicated that the depth of anaesthesia at this point was not adequate. The halothane was increased to take the dog back down to a suitable depth of anaesthesia. Halothane, which was used as the inhalation agent also sensitises the myocardium to catecholamines and it would have been better to use isoflurane which does not. However isoflurane is not available at this practice due to cost. Another problem encountered early in the anaesthetic was hypoventilation, caused by placing the animal in dorsal recumbency, which resulted in hypoxaemia, due to obesity. When an obese animal is placed on it's back the abdominal contents impede the diaphragm's movement. A Lack circuit is not designed for prolonged IPPV as rebreathing expired gases can occur. To try and overcome this the flow rate was turned up to 8 L. Neither a Bains circuit or ventilator was available at the time. The inspiratory phase was kept short (1 - 1.5 secs) as venous return is impeded during the inspiratory phase. The pulse oximeter rose to 97% and the m/m returned to pink. Nitrous oxide is an analgesic and is usually used at a ratio of 2:1 with oxygen. Ten minutes oxygen time must be used after cessation of nitrous oxide to avoid diffusion hypoxia. Turning off the nitrous oxide would have contributed to the dog showing a pain response to surgical stimulation, so the nitrous oxide was put back on at the previous flow rates and IPPV assistance continued 3 - 4 times a minute to assist the dog's spontaneous breathing. This kept the pulse oximeter reading above 90% for the duration of anaesthesia. Respiration rates remained quite fast throughout anaesthesia and this was attributed to obesity. Because of the risk of PVC's it was important to use the ECG to monitor the heart. Lignocaine at 1mg/kg was available to treat any PVC's if necessary, ie more than 2 in a row occuring or any PVC's in conjunction with low blood pressure. It would be necessary to ascertain the cause of the PVC's before treating with lignocaine, ie if caused by hypoxaemia or inadequate depth of anaesthesia then rectifying those problems should resolve the PVC's. Also, stopping the halothane and using isoflurane might rectify the problem. If neither of these work then a bolus of lignocaine can be tried. Close observation on depth of anaesthesia should be kept when using lignocaine (particularly if an infusion is used) as it is an anaesthetic and can lead to deepening of the anaesthetic level.

It might have been better to give the Rimadyl at the same time as the premedication as this would have ensured that it was effective at the time of the first incision. Research shows that Rimadyl has a synergistic effect when given in conjunction with morphine (a pure opioid acting on the mu receptors). Rimadyl is the only Non-Steroidal Anti-Inflammatory analgesic considered safe to use peri-operatively due to the fact that it does not inhibit the body's production of prostaglandins which play a role in protection of the gut and maintenance of renal function. Capillary refill time increased from 1 second to 1.5 seconds during ligation of the spleen and Haemaccel was substituted for Hartmann's to support the circulation volume, as the tumour was very friable and started to rupture.

Haemaccel is a gelatin used as a plasma expander which will remain in the circulation for about 5 hours. Hartmann's crystalloid was used at an initial rate of 10mls/kg/hr as this is the recommended fluid and rate of infusion for general intra-operative use. The rate of infusion of the Haemaccel was speeded up at this point and after 20 minutes the CRT returned to 1 second. Haemorrhage was not severe in this case, but if it had been it would have been better to give whole blood.If blood loss is to replaced by Hartmanns, three times the amount of blood lost should be given. However, for this procedure it is really important to provide intravenous fluids as it will be expected that removing a spleen which contains a fairly large amount of blood will have an effect on the cardiovascular system. Peripheral pulses, ie lingual and carpal were present throughout. This would indicate that, together with pink m/m's and reasonable CRT, that blood pressure remained reasonable during anaesthesia. Ideally it would be best to be able to monitor blood pressure with either direct measurement via an arterial catheter or indirectly with a cuff and Doppler or Dynamap type of measurement. None of these are available at this practice.

Temperature loss was minimal (1.2C) despite the age, duration of anaesthesia and an open abdomen. This was mainly due to having a heated operating table and using warmed fluids. This would have contributed to the quick recovery. Analgesia was suitable for this procedure and, although morphine is reported to delay recovery, it didn't in this case which was actually a disadvantage as fluid infusion had to be abandoned after recovery due to excitability of the dog.

Overall, this was a successful anaesthetic in view of the possible complications which could have occurred. The two features of the anaesthetic which were least successful were the inadequate depth of anaesthesia at the time of the first incision and management of the hypoventilation. Unfortunately some limitations are set by the equipment available, and although not ideal the pulse oximeter readings were kept above 90% (the level at which hypoxaemia occurs) for the duration of the anaesthetic after 1 minute below 90%. All complications were discussed prior to induction and relevant treatment protocols also prepared in order that the surgeon would not have to concentrate on surgical and anaesthetic emergencies simultaneously.

References:
Small Animal Surgery, T Fossum. Mosby. p 450 1997
Anasethesia of the Critical Patient, C Trim. BSAVA Congress 1999
Principles of Anaesthesia. Cont Ed Course. BSAVA March 1999 L Hughes & R McMurphy

Case 1. Splenectomy

Anne-Marie Lebis — Fri, 16 Apr 2010 20:44:54 GMT

Revision 4 posted to Dip AVN Cases by Anne-Marie Lebis on 4/16/2010 8:44:54 PM

OWNER	PIERCE	ANIMAL:	JASPER
SPECIES:	DOG	BREED:	XB
AGE:	10 YEARS	SEX:	MALE NEUTER
WEIGHT	29 KG OBESE	CONDITION:	BRIGHT

Clinical History.xx
The dog was first presented for anal adenomas which were subsequently removed under general anaesthesia. A routine palpation of the abdomen whilst the dog was under anaesthesia revealed a mass which was diagnosed as a splenic tumour. As the owners had not given consent for this surgery the dog was booked in for removal of the spleen 2 weeks later, as the dog was not showing any clinical symptoms consistent with a splenic tumour. A blood sample to measure packed cell volume was taken pre-operatively and this was recorded at 0.47 L/L, which was normal. The owners were warned of the risks associated with general anaesthesia of an old, obese dog undergoing a splenectomy and were required to sign a consent form to allow general anaesthesia and surgery.

Anaesthetic Cases - Appendix

sabira mali — Fri, 24 Jul 2009 17:15:10 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:15:10 PM

Equipment available for anaesthesia

Piped gases from external bunker using 6800L Oxygen cylinders and 3400L Nitrous Oxide cylinders.
Active scavenging piped to outlet on roof.
Ex-hospital anaesthetic machines with low oxygen alarms, fitted with emergency E size oxygen cylinders and Fluotec Mark 3 vaporisers which are calibrated for use with Halothane.
Anaesthetic chamber, connected to scavenging system, for use with small animals.
ECG machine
Pulse oximeter
Respiration monitor (ap-Alert)
Heated operating table
Magill semi-closed circuit, used with various face masks.
Parallel Lack semi-closed circuits
Co-axial Bains semi-closed circuits
Ayre's T-Piece semi-closed circuits, all with Jackson Rees modification
Circle closed circuit
Oxygen tent for cats and small dogs
All sizes of cuffed and uncuffed endotracheal tubes
Laryngoscope
Oesophageal stethoscopes
Reservoir bags ranging from 2L to 5L

Drugs available for anaesthesia and premedication

Thiopentone Sodium (Intraval Sodium, Rhone Merieux) 2.5%
Propofol (Rapinovet, Coopers)
Halothane
Ketamine (Vetalar, Parke-Davis)
Pentobarbitone Sodium (Sagatal, RMB) - this is only used for fitting animals
Medetomidine (Domitor, SKB)
Atipamezole (Antisedan, SKB)
Xylazine (Rompun, Bayer)
Fentanyl/Fluanisone (Hypnorm, Janssen)
Atropine Sulphate 0.6 mg/ml (Atrocare, Animal Care)
Glycopyrrolate (Robinul, Robins)
Acepromazine 2mg/ml (ACP, C Vet)
Diazepam 10mg in 2mls (Valium, Roche)
Butorphanol 10mg/ml (Torbugesic, Willows Francis)
Morphine Sulphate 10mg/ml (Evans)
Pethidine 50mg/ml (CD)
Buprenorphine 0.3mg/ml (Temgesic, Reckitt & Coleman)
Adrenaline 1mg/ml (Phoenix)
Digoxin 0.5mg in 2mls (Lanoxin, Wellcome)
Naloxone hydrochloride (Narcan, Du Pont)
Doxapram hydrochloride 20mg/ml (Dopram V, Willows Francis)
Calcium gluconate 2.2 mmol/10mls (Phoenix)
Suxamethonium (Anectine, Wellcome)
Lidocaine hydrochloride 2% (Intubeaze, Arnolds) spray
Lidocaine hydrochloride 2% (Xylocaine Gel, Astra Pharm)
Dobutamine 12.5 mg/ml (Dobutrex)
Compound sodium lactate (Hartmanns)
Sodium chloride 0.9% (Saline)
Haemaccel 5L

Case 3. Bone marrow biopsy

sabira mali — Fri, 24 Jul 2009 17:14:23 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:14:23 PM

OWNER	ABBOTT	ANIMAL:	CINDY
SPECIES:	DOG	BREED:	G RETRIEVER
AGE:	8 YEARS	SEX:	FEMALE NEUTER
WEIGHT	27.5 KG	CONDITION:	BRIGHT

Clinical History.
The dog was presented with a subcutaneous mass just cranial to the right proximal humerus. A needle aspiration biopsy was taken and the mass proved to be a mastcell tumour. Complete surgical removal was considered to be impossible due to it's infiltrative nature. So a bone marrow biopsy was arranged, to check for metastases before the dog underwent radio therapy. The dog was prescribed 36 mg prednisolone once daily until the general anaesthetic. The owners were warned of the risks of general anaesthesia and signed a form giving permission for a general anaesthetic and surgery.

Pre-anaesthetic examination.
Bloods were taken for haematology and biochemistry profiles, the results of which were unremarkable. See anaesthetic record. Auscultation of the pulmonary and cardiovascular systems did not reveal any abnormalities. Temperature was 38.4 C, heart rate 96 per min and respiration 24 per min. The dog had been starved for 10 hours with access to water until 2 hours prior to induction.

Premedication.
Premedication consisted of 0.28 mg of glycopyrrolate (Robinul, Robins), 8.25 mg of butorphanol (Phoenix) and 55 mg diphenhydramine (Abbott) all by intramuscular route. The premedication worked extremely well and the dog was very quiet and sedate at the time of induction 20 minutes later. Prior to induction an 18 guage intravenous catheter was placed aseptically into the right cephalic vein.

Induction.
Induction was achieved using 13.8 mg diazepam (Elkins-Sinn), followed by titration of 129 mg of 2.5 % thiopentone sodium (Phoenix), both via the intravenous catheter. Intubation was performed with an 11 mm cuffed endotracheal tube and positioned by palpation of the uninflated cuff at the thoracic inlet. The tube was connected to a circle circuit with 2 L of oxygen. The cuff of the endotracheal tube was slowly inflated whilst the reservoir bag was very gently squeezed with the valve closed, and inflation was stopped when sounds of gas passing round the tube were no longer heard. An ECG monitor was connected to the dog, the electrodes being placed just proximal to the stifles and olecranons. An area just distal to the stopper pad on the palmar aspect of the left forelimb was clipped and a Doppler sensor taped on, after application of conducting gel, in order to monitor blood pressure. The dog was placed on a water heated pad for the duration of anaesthesia. See picture right.

Maintenance of general anaesthesia.
The valve on the circuit was opened and maintenance of anaesthesia was achieved using 1 L oxygen with isoflurane at 2% reducing to 1.5 % after 45 minutes. Lactated Ringers crystalloid was given at a rate of 10mls/kg/hr for the duration of anaesthesia. For a detailed account of anaesthesia see attached record sheet. The heart rate was recorded at between 70 and 75 bpm for the first 20 minutes, and then began to decrease steadily over the next 10 minutes to 50 bpm. The systolic blood pressure (BP) had only fallen slightly, to 115 mm Hg. A bolus of 0.137 mg of glycopyrrolate (Robinul, Robins) was given at this time by intravenous route. The ECG trace showed a second degree AV heart block for a duration of approximately 1.5 minutes, before returning to normal complexes. The heart rate peaked at 120 bpm 2 minutes after administration of the glycopyrrolate and the systolic BP rose to 160 mm Hg. The heart rate fell gradually over the next 20 mins and was recorded at 88 bpm on extubation. The systolic BP fell to 115 mm Hg and was recorded at 130 mm Hg at extubation. Respiration was spontaneous throughout anaesthesia, with good chest excursion, and recorded at between 20 - 30 per min. It was not considered necessary to ventilate the dog. The dog did not lose any temperature during the course of general anaesthesia. Duration of anaesthesia was 57 minutes.

Post-operative period.
The dog was extubated 5 minutes after the end of anaesthesia and the pulse at this time was 96 per min, respiration 36 per min and temperature 38.1 C. The bladder was reasonably full and was manually expressed before the dog was put into a recovery kennel. Sternal recumbency was achieved 10 minutes after extubation and recovery was quiet. The dog went home the following morning, to return in 3 days for a post-operative check and 10 days for sutures out and the biopsy results. This case was conducted in the University of Georgia and I was no longer present when the biopsy results were received.

Discussion.
The condition, age of the animal and the type of surgery being performed are all important when deciding on a suitable general anaesthetic procedure and the possible complications which could arise. All of this should be discussed prior to anaesthesia so that a fast, suitable course of action can be taken if a crisis occurs, and hopefully selecting the most suitable agents will reduce the risk of such crises occurring. An animal should always be weighed prior to anaesthesia, as correct dosing of drugs can be critical, especially in older animals which may not even need the full calculated dose. This was suspected in this case and a note made prior to induction to titrate the thiopentone slowly in order to avoid overdose. There are differing views as to when an animal should be classed as a geriatric, and there is also the 'real' age of the animal to be considered, ie whether the animal's general condition would lead to an assumption that it is older or younger than it's birth age. In this case the University of Georgia state that a dog of this breed over 7 years old is classed as an old dog and this dog's 'real' age would be even older due to it's condition. This would mean that it is more likely to suffer from hypotension, hypothermia and hypoventilation under anaesthesia and would probably need reduced anaesthetic doses.

Premedication consisted of butorphanol (a partial agonist opioid), for both the sedative and analgesic components. Butorphanol has an onset of 10 minutes after intramuscular injection and lasts for 1 - 1.5 hours in the dog. In the US it is widely used as an analgesic but in this country the general opinion is that despite being an excellent sedative and anti-tussant, it's use as an analgesic is very limited as it appears to have very little analgesic effect. The author must agree with this opinion and perhaps a more potent opioid such as pethidine or morphine could have been used. Carprofen (a non steroidal anti-inflammatory drug) could not be used as it is contraindicated for use in conjunction with corticosteroids (prednisolone). There are differing views as to whether parasympathetic antagonists should be routinely used in premedication for several reasons. Firstly, in some cases it does dry up the salivary secretions and in others it makes them viscous and even more likely to block the endo- tracheal tube. It is contraindicated for use in animals with pre-existing tachycardia. Cats that have been given atropine often seem agitated and the pupillary dilation seems to upset them or cause them to panic. Atropine is said to prevent acid reflux from the stomach which can cause oesophagitis. The anticholinergic used in this case was glycopyrrolate as this is reported to be favourable for use in older animals. It has less occular effects than atropine and causes less tachycardia. Bradycardia (below 60 beats per min) did occur during the general anaesthesia, thought to be the result of the depressant effects of the anaesthetic agents, and glycopyrrolate was given intravenously to treat this. After adminstration the ECG trace showed heart block for approximately 1.5 minutes. This is 'normal' after giving the anticholinergic and should only be temporary. For a copy of the ECG trace showing the heart block (see below). After this initial heart block the heart rate did peak at 120 bpm and then gradually fell. It is important to ascertain that the cause of the bradycardia is not hypoventilation before giving glycopyrrolate and assisted ventilation should be under- taken first.

Diphenhydramine (an anti-histamine) was also included in the premedication, as mast cell tumours release histamines (which lower the blood pressure) when manipulated.This would appear to have been successful, as although the anaesthetic agents caused bradycardia, the systolic blood pressue did not fall below 110 mm Hg (80 mm Hg being considered as hypotension). Diazepam (a benzodiazepine) was given at induction prior to thiopentone in order to reduce the amount thiopentone needed. This is important in ill or elderly animals as thiopentone produces both respiratory and cardiovascular depression, whereas diazepam has little effect. It was very successful in this case, as 330 mg was the calculated dose of thiopentone needed and only 129 mg was given in order to allow intubation. Diazepam can also be used in this way with other induction agents.

Isoflurane was used as the maintenance agent as recovery from this agent is faster than halothane, as much less is retained in the body to be metabolised by the liver. It is very expensive and therefore often used in conjunction with a closed circuit, as low flow rates reduce the amount vapourised and wasted via the scavenging system. In this case the flow rate through the circuit was 1L per minute (minute volume), but it is possible to reduce the minute volume in a circle circuit to 500 mls, but it is advisable never to use as a totally closed circuit.

Old animals have difficulty in maintaining body temperature during general anaesthesia so the dog was placed on a water heated pad. This proved successful and the dog did not lose any temperature during the anaesthetic. If this had been a problem a warm air blower was available to blow warm air via a hose placed under a towel which covers the animal. Towels heated in the microwave are also used to pack around the animal if, say, abdominal surgery is performed. Hypothermia will delay recovery from anaesthesia and will increase the potency of anaesthetic drugs during anaesthesia, due to slowed metabolism of drugs. After long anaesthetics, where possible, bladders are manually expressed before recovery from anaesthesia. This ensures that the animal does not soil itself with urine during recovery when it is still recumbent. This is especially important if dressings have been used. Failure to express a bladder will be reported to the ICU staff, so that they can take appropriate measures to avoid this problem.

Hartmann's is the crystalloid of choice for general operative fluids and 10mls/kg/hr is the accepted rate of infusion. Intra-operative fluids are important to maintain good renal perfusion, particularly in older animals whose renal function is likely to impaired. Monitoring instruments are very useful in anaesthesia, as long as the anaesthetist is able to interpret them and also accepts that instruments can give inaccurate readings due to poor connections etc. Observation is still the most important skill of a good anaesthetist.

This anaesthetic was well managed and, as the other cases also show, changes in an animal's status can occur very quickly and one person should be dedicated only to monitoring the anaesthetic and not required to do anything else. Unfortunately this does not always happen in general practice, due to lack of staff.

References:
Veterinary Anaesthesia, Hall & Clarke, Saunders, 9th Ed 1991
Manual of Anaesthesia, BSAVA 1992
Prof C Trim, BSAVA Congress 1999
Prof C Trim 1999 - visit to University of Georgia, USA

Case 2. Biopsy Mass

sabira mali — Fri, 24 Jul 2009 17:13:09 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:13:09 PM

OWNER	TWIST	ANIMAL:	CRICKET
SPECIES:	DOG	BREED:	AMERICAN SPITZ
AGE:	11 YEARS	SEX:	FEMALE
WEIGHT	9.3 KG AVERAGE	CONDITION:	DYSPNOEA

Clinical History.
The dog was first brought in by the owner for respiratory distress. Stridor was evident on inspiration, visual examination revealed an intra-oral mass occluding the glottis and palpation of the neck revealed a mass present in the caudal oropharyngeal area over the larynx, dorsal to the trachea and about 5 cms in diameter. Exopthalamus was also noted. There were no other clinical symptoms. The owner reported that the dog had become increasingly more dyspnoeic over the last 2 months. A general anaesthetic for radiography and a biopsy was arranged for the following morning, the owner having been warned of the risks of general anaesthesia and having signed a consent form.

Pre-anaesthetic examination.
Blood samples were taken for both biochemistry and haematology profiles, the results of which were unremarkable. See anaesthetic record sheet. A clinical examination revealed temperature of 38 C, heart rate of 100 per min and respiration rate of 20. There were no apparent abnormalities of the cardiovascular or respiratory system, other than the mass. The dog was kept overnight in an oxygen cage in the intensive care unit (ICU) and starved from 10 pm with access to water until 8 am. The dog was given a class 3 anaesthetic risk, ie a patient with severe systemic disease that is not incapacitating.

Premedication.
Premedication consisted only of 0.37 mg atropine sulphate (Phoenix) given by intra- muscular route 30 minutes prior to induction. After premedication the dog was monitored constantly until induction.

Induction.
As difficulty of intubation was expected, due to the occlusion of the glottis, equipment was available for a tracheotomy and also an endoscope for assistance with intubation. Five minutes pre-oxygenisation was given via a mask before induction. The dog was quite calm prior to and during induction. A 20 g intravenous catheter was placed aseptically into the right cephalic vein. A smooth induction was achieved using 74 mg propofol (Diprivan, Zeneca) given slowly through the catheter. Intubation was performed successfully using a 6.5 mm cuffed endotracheal tube. Correct placing of the ET tube was carried out by palpating the thoracic inlet area with one hand whilst moving the tube in and out slightly in order to feel where the uninflated cuff was positioned. Correct inflation of the cuff was achieved by one person slowly inflating the cuff and listening by the mouth whilst a second person closed the valve on the circuit (which had been connected to the tube and 2 L oxygen turned on) and very gently squeezing the resevoir bag until no sounds of gas passing round the cuff could be heard and pressure was felt squeezing the bag. The dog had been connected to a circle circuit with oxygen flow of 2 L per min which was reduced to 1 L after 20 minutes. Isoflurane was used as the maintenance agent with initial settings of 2%, being reduced to 1% after 35 mins. An infusion of lactated ringers was started at a rate of 10ml/kg/hr. An area just distal to the stopper pad on the palmar surface of the left foreleg was clipped, conducting gel applied and a Doppler sensor attached with tape. A cuff was applied to the left proximal foreleg in order to measure blood pressure (BP). 0.465 mg of oxymorphone (Numorphan, Du Pont) was given by intravenous route.

Radiography.
The dog was radiographed which showed a mass consistent in size and position as described in the clinical examination. A biopsy was then taken through an incision in the right lateral neck.

Maintenance of anaesthesia.
For a detailed account of anaesthesia see attached anaesthetic record. Duration of anaesthesia was 60 minutes. General anaesthesia was unremarkable until 30 minutes into anaesthesia when a haemorrhage occurred at the incision site and the carotid artery was ligated. The systolic BP went up from 115 to 280 mm Hg. At this point the dog was connected to an ECG and within 1 minute premature ventricular contractions (PVC's) started intermittently. They then began to occur in ventricular bigeminy (every second complex was a PVC) and after a further 30 seconds were occurring in strings of 10 followed by one or two normal complexes. At this time a bolus of 9.3 mg of lidocaine (Abbott) was given by intravenous route. This had no effect and a further repeat bolus was given 1 minute later. At this time the isoflurane was reduced to 1%. See above right, where the PVCs can just be seen on the monitor. The PVC's then became intermittent again and a further 9.3 mg was given 10 minutes later, just before the cessation of anaesthesia. The systolic BP remained around 250 mm Hg and heart rate around 150 per minute. Little blood loss had occurred.

Recovery from anaesthesia.
Five minutes after cessation of isoflurane the larynx was swabbed, the oxygen had remained on and the ET tube was removed with the cuff partially inflated, and when the dog was in sternal recumbency. The dog initially seemed to have difficulty breathing and the tongue was extended and a pulse oximeter attached. The readings showed 72% (hypoxaemia) and an oxygen mask applied was immediately. The dog, at this time, became uncontrollable and disorientated, despite now being able to breath easily. It was impossible to maintain the oxygen mask over the face and the dog was taken straight through to the ICU where an intravenous bolus of 2.4 mg of diazepam (Elkins-Sinn) was given. This calmed the animal enough for telemetry pads to be attached whilst oxygen was administered and then the dog was put into an oxygen cage with the Doppler still attached. See the picture above, taken 15 minutes after being put in the oxygen cage. An hour later the dog was still showing signs of dyspnoea and had a systolic BP of 220 mm Hg, which was still high. The telemetry monitor showed that although the PVC's had stopped the T waves were large.

Post-operative progress.
Two hours after recovery the telemetry started showing abnormal traces and a cardiologist was called to interpret the trace. His recommendation was that the dog be monitored at all times, but that treatment was not necessary at this time. The dog remained in an oxygen cage for 48 hours, by which time the ECG trace had returned to normal and the dog was showing less dyspnoea than when it was first admitted. It was sent home the following day after being out for exercise and not showing any signs of dyspnoea. The owners were advised to restrict the dog to lead exercise and return in 3 days and 10 days for suture removal and biopsy results. It was not clear at this stage whether a tumour was present or whether the mass was in fact an aneurysm. If the results showed a tumour the dog would have radiotherapy as it was not possible to remove any more tissue. As this case was conducted in the University of Georgia, USA I was no longer present when the biopsy results came back.

Discussion.
The protocol for this general anaesthetic was discussed prior to induction and drugs were chosen to suit the animal's condition at the time of surgery. Possible complications were also discussed and provision made for dealing with these, ie the tracheotomy site was prepared and all equipment ready to use. This is very important as quick action needs to be taken and time is wasted making decisions after the crisis has occurred. The animal's life may also be at risk if necessary equipment is not at hand. However, this anaesthetic also proved that no matter how much planning takes place emergencies can always happen unexpectedly despite all possible precautions, ie the anaesthetic implications of ligating the carotid artery, which was also not expected. Only atropine was given as premedication, as there was concern that any sedative would cause further respiratory distress before an airway was secured. Atropine is an anticholinergic drug which was given to inhibit secretion of saliva and protect against bradycardia. Anticholinergics are standardly included in pre- medications in the University of Georgia, but other views held are that it should only be given if necessary, ie for bradycardia or if surgery might provoke a vagal response. Respiratory depression was also the reason that the oxymorphone was not given until after the dog was intubated, as although oxymorphone is ten times stronger than morphine, but has less effect as a depressant on the respiratory system, there is still some depression.

Oxymorphone can also be given quickly by intravenous route and has an onset time of about 3 minutes. When anaesthetising any dyspnoeic or very sick animal oxygen should always be given prior to induction so that the tissues are saturated, to cover the period of intubation when hypoxia can easily occur.

Propofol was used as the induction agent as recovery from this drug is rapid, which is very important when any surgery or problems with the upper respiratory tract are involved. This is because the swallow reflex and cough reflex need to present as soon as possible when consciousness returns, to avoid any aspiration or obstruction of the airway. Propofol would also be the choice of induction agent for otherwise healthy brachycephalic breeds, who anatomically have a predisposition for upper airway obstruction on recovery.

Correct placement of the ET tube is very important, and palpation of the cuff within the thoracic inlet ensures that the tube does not pass down into one bronchus which would be detrimental to the animal and would also mean difficulty in maintaining anaesthesia. Correct inflation of the cuff is also important, as it has to be inflated enough to provide a seal to stop wastage of gas and pollution by gases escaping into the theatre. Over inflation of the cuff can cause damage to the tissues with serious implications due to the nature of the site. The correct size of ET tube should, of course, be selected to suit the animal. The tube in this instance was placed correctly but could have been trimmed shorter, as the end of the tube should be by the nostrils, in order to keep the amount of mechanical dead space as small as possible. In this case the tube extended 5 cms beyond the nostrils. See the picture above, taken just prior to extubation.

A circle circuit with the valve opened slightly was used to maintain anaesthesia. The advantage of this is to save money on gases and maintenance agents. Also, if intermittent positive pressure ventilation (IPPV) is needed, and no ventilator available, it is easier to do this on a circle than a semi-closed circuit such as the Bains. The subject of whether nitrous oxide should be used in a circle system is controversial. In this country, generally, there is concern that nitrous oxide will build up within the system to harmful levels and that it should not be used unless inspired oxygen levels can be measured. However, in the US it is used frequently, as after extensive monitoring at the University of Georgia they found that using 1L of oxygen and 1 L nitrous oxide to be quite safe to use with the valve partially open, but would not recommend any higher percentage of nitrous oxide to be used without monitoring devices. Isoflurane was used as the maintenance agent, as it does not sensitise the myocardium to catecholamines which can lead to PVC's, (as halothane does). So it was an advantage that isoflurane was used in this case as, although the dog suffered severe PVC's, it probably would have been more of a problem if halothane had been used. Recovery from isoflurane is faster than halothane as less is retained in the body for metabolism, which was also needed in this case for reasons previously explained. The disadvantage usually with isoflurane is that it lowers blood pressure more than halothane, (when used at the correct dosage). However, in this case this was a distinct advantage as hypertension was a problem. Propofol also has less of an effect on sensitising the myocardium than, say, thiopentone so again this was another advantage of using propofol. It was not known if hypertension existed prior to anaesthesia, as it was not measured, although exopthalmus was noted during the clinical examination.

The hypertension was thought to be partly the cause of the extreme hyperactivity of the dog after extubation, however it was decided not to use acepromazine to sedate the dog and reduce the blood pressure, as it was unclear at this time as to the cause of the hypertension and how long it might last and the concern was that if the BP were to return to normal suddenly the added effect of the acepromazine might take the BP too low too quickly for the body to compensate. This is why diazepam was selected, although in healthy dogs it can actually increase excitement. However, the dog did become calmer and less dyspnoeic. Excitement with struggling or distress in an already dyspnoeic animal can easily lead to death and should always be avoided if possible or treated with drugs. In this case dyspnoea and hypoxia were the main concern on extubation and all monitoring other than the telemetry and visual observation was suspended for one hour to allow the dog's oxygen status to improve.

The other important feature of this general anaesthesia were the PVC's which started to occur 30 minutes after induction when the carotid artery was ligated which affected the baroreceptors present in the artery. PVC's can also be caused by anaesthetic drugs, hypoxia, interfering with certain tumours or organs, such as the pancreas, which then release catecholamines, inadequate depth of anaesthesia leading to stimulation of the sympathetic nervous system, hypoventilation and pulmonary and myocardial contusions caused by trauma to the chest. All of the above sensitise the myocardium to the effects of catecholamines, which can result in PVC's occurring. PVC's should be treated with drugs if the cause is not attributed to hypoxia or inadequate depth of anaesthesia, (both of which can be corrected by appropriate actions), if changing from halothane which sensitises the heart to isoflurane (which does not) has no effect, if the PVC's occur in conjunction with low BP or occur more than two in a row. The drug of choice is lidocaine which can be given at 1 to 2 mg per kg as a bolus or as an infusion. In this case 3 boluses were used to control the PVC's and an infusion was not necessary. The isoflurane was turned down to 1% after administration of lidocaine, as it is an anaesthetic and can affect the depth of anaesthesia (more usually when using an infusion). However, it was important to monitor the heart post-operatively to ensure that they did not recur. Telemetry was used for this purpose as it has several advantages over normal ECG monitoring. Firstly it is impractical to have ECG electrodes connected to a conscious animal for obvious reasons of disconnection problems. Telemetry involves putting electrode pads on the animal and plugging them into a small transmitter box, which fits into a pouch and tied round the animal. The ECG trace is radio transmitted and picked up by an aerial in the ceiling and the trace is displayed on a central monitor visible from anywhere in the ICU. Up to 8 animals can be displayed at one time. Two hours into the post-operative period the ECG trace showed several irregularities and the consultant cardiologist was called. The large T waves were attributed to myocardial hypoxia and, on examination of the other abnormalities, it was stated that interference with, or ligation of the carotid artery will often cause the hypertension, PVC's and other abnor- malities seen on the ECG trace. Stimulation of the vagal nerve is also involved. This is of importance for the anaesthetist to be warned in advance by the surgeon of any surgery which will interfere with the carotid artery or which will involve ligation of the artery. Fossum, Small Animal Surgery, Mosby 1997 recommends ligation of the carotid artery during a maxillectomy, but there is no mention of the possible anaesthetic implications associated with this procedure. Human literature states that even temporary occlusion of the carotid artery can cause permanent brain damage due to lack of oxygen. This hypoxia (shown by the pulse oximeter and large T wave) may have been the cause of the disorientation displayed by the dog after extubation. As to whether permanent brain damage occurs in animals when the carotid artery is ligated, animals may not show this as readily as humans or owners may notice changes in the behaviour of the animal but not relate it to the anaesthesia, and therefore not mention it. The chemoreceptors and baroreceptors are also involved in the oxygen/carbon dioxide homeostasis of the body and it would be difficult to tell whether, in this case, the hypoxia was caused by the reaction to the ligation or the original upper respiratory obstruction. At the time that the hypertension started the dog's temperature also rose and finished a little higher than prior to induction. Respiration remained constant, apart from a period of panting which is common after administration of oxymorphone, with a good tidal volume and it was not judged necessary to ventilate the dog. Lactated Ringers (Hartmann's) is the preferred intra-operative crystalloid to use and was infused at the correct rate. Post-operative analgesics were withheld due to concern over any respiratory depression being detrimental. This is a view that widely differs within the veterinary profession. It is understandable to have concern about opioids and their sedative and repressive effect, but injectible carprofen (a NSAID) could possibly have been used, as it is considered safe to use peri-operatively, due to it's lack of inhibition of the body's prostaglandin production which plays a role in renal function and protection of the gut lining. Although this procedure would not seem to be one of the most painful surgeries it would be considered unacceptable to withdraw analgesia if this procedure were carried out on a human. Carprofen is still relatively new in the US and is not yet often used peri-operatively.

Overall, this was a complicated general anaesthetic which was well planned and managed, which demonstrated the usefulness of monitoring devices for identifying complications.

References:
Veterinary Anaesthesia, Hall & Clarke, 9th Ed, 1991
Manual of Anaesthesia, BSAVA 1992
Small Animal Surgery, T Fossum. Mosby 1997
Prof C Trim, Head of Sm & L An Anaes, University of Georgia, US. Aug 99
BSAVA Congress Anaesthesia Lectures, C Trim. 1999

Case 3. Excision arthroplasty of left hip

sabira mali — Fri, 24 Jul 2009 17:08:01 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:08:01 PM

OWNER	ALI	ANIMAL:	TOM
SPECIES:	CAT	BREED:	DSH
AGE:	1 YEAR	SEX:	MALE (N)
WEIGHT	4.1 KG	CONDITION:	GOOD

Clinical History
The cat was presented not able to weight bear on it's left hind leg, the owner having reported the cat coming in lame that morning. A clinical examination revealed a wound on the stifle, but palpation of the limb was not possible due to the cat's discomfort. A clinical examination of the cardiovascular and respiratory systems revealed no abnormalities and the cat was admitted for radiography under general anaesthesia. The cat had not eaten that morning, but the owners were warned of the risks of general anaesthesia and signed a consent form for general anaesthesia and possible surgery. The cat was premedicated with 0.16 mg acepromazine (ACP C VET) and 7.5 mg pethidine (Pethidine, Arnolds), both by intra- muscular route, 40 minutes prior to induction.

Radiography
Induction was achieved using 50 mg thiopentone sodium (Intraval, Rhone Merieux) by intra-venous route and an uncuffed 5 mm endo-tracheal tube used to intubate. Maintenance of anaesthesia was achieved using an Ayres T piece with flow rates of 2 L nitrous oxide and 1 L oxygen with halothane as the volatile agent. Antibiotic cover was provided with 100 mg ampicillin LA (Amfipen LA, Intervet) and additional analgesia with 15 mg carprofen (Rimadyl, Pfizer), both by subcutaneous route.

Radiographs of the pelvis were taken in both right lateral and ventrodorsal projections, and on examination the ventrodorsal projection showed that the left femoral neck had fractured with the femoral head remaining in the acetabulum. See Radiograph 1. The surgeon decided to perform an excision arthroplasty and the owners were contacted to advise them of the necessary surgical procedure.

Surgical preparation
A 22 g intra-venous catheter was placed aseptically into the right cephalic vein and an infusion of Hartmanns was started at a rate of 10mls/kg/hr. The left hind leg was clipped and prepared as in the first paragraph of Appendix 1, to include an area extending from the hock to the whole hip area, the incision site being over the greater trochanter of the femur. The cat was then moved to the theatre and final preparation of the skin took place as in the second paragraph of Appendix 1.

Surgery
The limb was lifted up by the nurse (holding the foot). The surgeon placed the first drape under the limb, lying along the ventral abdomen and left groin. A second drape was held under the limb and the nurse released the foot onto the drape. This drape was then wrapped around the distal limb and held in place with a towel clip. A third and fourth drape were placed to leave the proximal limb, including the hip exposed. See above.

The instruments used for this procedure included a standard kit, as described in Appendix 2. Additional instruments included Gelpi retractors, a Hohman retractor, an osteotome, an orthopaedic hammer and a disarticulator. Sterile saline was also used for flushing the surgical site.

An incision was made through the skin 5 cms in length over the greater trochanter, proximally just short of the dorsal midline and distally following the cranial border of the femur. The skin was undermined and retracted with the subcutaneous tissues. An incision was made in the superficial leaf of the of the fascia lata and the insertion of the tensor fascia lata muscle, following the cranial border of the biceps femoris muscle.

The biceps femoris was retracted caudally, and the fascia lata and tensor fascia lata retracted cranially, after separation of the tensor fascia lata from the middle gluteal muscle. Blunt dissection along the neck of the femur with the finger tip allowed visualisation of the deep gluteal muscle. The middle gluteal muscle was retracted caudally and partial tenotomy of the caudal two thirds of the deep gluteal muscle was performed. The joint capsule was incised and a Hohman retractor used to elevate the neck of the femur, whilst rotating the stifle outwards. An osteotome, with the orthopaedic hammer, was used to excise the neck of the femur. The excision site was checked to ensure that there were no sharp edges. The disarticulator was then used to sever the round ligament and remove the femoral head from the acetabulum. The area was flushed with sterile saline and the gluteal muscles coapted with 3 m chromic catgut (Ethicon) using mattress sutures. The fascia lata muscles were repaired as above and the subcutaneous tissues closed using 3 m catgut in a simple continuous pattern. The skin was closed using 2 m polyamide (Nylonamide, Animus) in a simple interrupted suture pattern. A total of 200 mls of Hartmanns was infused for maintenance, as no major haemorrhage had occurred. The endotracheal tube was removed within 3 minutes of the cessation of anaesthesia.

Post-operative progress.
The cat was in sternal recumbency within 15 minutes after extubation. Analgesia was repeated after 6 hours with 0.8 mg of morphine (Morphine Sulphate, Evans) by intra-muscular route.

The animal was sent home in the afternoon with instructions to the owner that the cat should be confined to house rest, and that revisits were necessary in 4 and 10 days for a post- operative check and sutures out. The cat was prescribed Rimadyl 20 mg tablets to be given half daily with food for 4 days, starting the following day, and Amfipen 50 mg tablets to be given one twice daily for 2 days, starting in two days.

The post-operative check was satisfactory - the cat was weight bearing on the limb, and sutures were removed after 10 days. Within 4 weeks the cat was using the limb normally.

Discussion
Excision arthroplasty is regarded as a salvage procedure to aleviate pain and restore a reasonable motility of the limb. Cats and small dogs, due to their light weight, seem to do well after the procedure and most have a wide range of movement of the limb. Large dogs (over 25 kg) can have problems with this treatment and other types of repair should be considered.

Complications that can occur from this procedure include damage to the sciatic nerve, resulting in possible paralysis, or chronic post-operative pain due to sharp edges being left on the femoral neck. There are several approaches to the hip joint, this one being considered to have the best exposure of the femoral neck. Post-operative care includes use of the limb, on a restrictive basis and active animals tend to have a quicker recovery than obese lethargic animals, as do animals that have suffered acute trauma (as in this case) rather than chronic conditions. It is particularly important to maintain the highest possible aseptic technique during any orthopaedic surgery. The drapes for this procedure did not quite cover the whole cat, and drapes of adequate size to cover the whole animal should always be provided, in order that the surgeon can give total concentration to the procedure without having to think about any risk of contamination. Ideally, a barrier drape should be used in order to avoid any bacterial strike through occurring when drapes get wet due to blood loss or flushing. On this occasion a drape, wrapped round and secured with a towel clip, was used to cover the distal limb. When manipulation of the limb during surgery is required a sterile bandage wrapped round and tied is probably less likely to slip, allowing contamination of the surgeon. Pethidine, an opiate, was chosen for the analgesic as the procedure was a painful one and inclusion in the premedication ensured that it was active at the time of the first incision. Carprofen, a non steroidal anti-inflammatory drug, was given after induction to ensure it was active during recovery which is very important when using thiopentone which has an antanalgesic effect during recovery. Pethidine is a short acting opioid, about 2 hrs in the cat, and analgesia was repeated after 2 hours using 0.8 mg of morphine by intra-muscular route. Morphine is a more potent analgesic than pethidine and also remains active for longer, ie 6 - 8 hours in the cat, so could have been used initially in the premedication instead of pethidine. However, analgesia was satisfactory for this procedure and the cat was comfortable post-operatively.

With regard to the use of suture materials, being a publicly funded clinic, cost will always play an important part in choice between any two suitable suture materials. Chromic catgut often causes an inflammatory tissue reaction and polyglactin 910 (Vicryl) could have been used as an alternative suture material. When catgut is used it should be rinsed in sterile saline after removal from the package, as the solution it is stored in is an irritant to tissues. Polyamide is the standard material used for skin closure at this practice, but monofilament nylon or Vicryl could have been used. Hartmanns was a good choice of fluids for general maintenance under anaesthesia. Plasma expanding fluids might have been necessary had there been haemorrhage during surgery. The owners were told to put an elizabethan collar on the cat to stop removal of sutures. However, generally speaking if an animal removes sutures it is usually because they are irritant, ie too tight, or underlying catgut is causing a tissue reaction. The sutures in this case were placed quite loosely to allow for any swelling of tissues and the owners stated that they found it unnecessary to use a collar.

References:
Atlas of Surg Approaches to Bones of Cat & Dog, Piermattei, Greeley. 2nd Ed Saunders 1979
Sm An Orthopaedics, Brinker, Piermattei, Flo. 2nd Ed. Saunders 1990
Sm An Surg Nursing, D Tracy, 2nd Ed. Mosby 1994

Case 1. Pancarpal arthrodesis

sabira mali — Fri, 24 Jul 2009 17:07:26 GMT

Revision 6 posted to Dip AVN Cases by sabira mali on 7/24/2009 5:07:26 PM

Pancarpal Arthrodesis Using Bone Graft From Proximal Humerus

OWNER:	FIELD	ANIMAL:	MAX
SPECIES:	DOG	BREED:	BORDER COLLIE
AGE:	6 YEARS	SEX:	MALE
WEIGHT:	25.6 KG	CONDITION:	GOOD

A standard kit, as listed in Appendix 2, was laid out with additional instruments as listed in Appendix 3.

Case 4. Bilateral Thyroidectomy

sabira mali — Fri, 24 Jul 2009 17:06:52 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:06:52 PM

OWNER	THEOBALD	ANIMAL:	CANDY
SPECIES:	CAT	BREED:	DSH
AGE:	10 YEARS	SEX:	FEMALE
WEIGHT	3.4 KG	CONDITION:	FAIR

Clinical History
The cat was first presented for episodes of collapse and ataxia. An ECG revealed a heart rate of 260, sinustachycardia. A radiograph showed massive cardiomegaly. Systolic blood pressure measured at 178 - borderline hypertensive. The left thyroid was enlarged on palpation. Blood samples showed thyroxine > 300 nmol/l ( normal 19 - 65), elevated ALT and Alk Phos, and urea and creatinine normal. The cat was prescribed carbimazole 5 mg (NeoMercazole, Roche) one tab every 8 hrs, and propranolol 10 mg (Inderal, Zeneca), a quarter of a tablet three times daily.

The cat initially responded to medical treatment with a heart rate of 175 and systolic blood pressure falling to 142, and a weight gain of 0.1 kg in 3 weeks. However, the cat continued to be polyphagic and no further improvement was seen. In view of this and that the cat was only 10 years old it was decided to try surgical treatment. The cat was booked for a unilateral left thyroidectomy. The owners were warned of the risks of a general anaesthetic and of possible post-operative complications, and signed a consent form before surgery was undertaken.

Surgical preparation
Premedication consisted of 0.5 mg of morphine (Morphine Sulphate, Evans) by intramuscular route 1 hour prior to surgery. A 22 g intravenous catheter was placed aseptically into the right cephalic vein and an infusion of 200 mls of Hartmann's was started at a rate of 10mls/kg/hr. Induction was achieved using 1.5 mg diazemuls, followed by 20 mg propofol (Rapinovet, Schering Plough) given to effect, both by intravenous route.

The cat was intubated with a 5 mm uncuffed endotracheal tube and anaesthesia was maintained using a semi-closed Ayre's T piece with a Jackson Rees modification. Flow rates of 2L of nitrous oxide and 1L of oxygen were used, with halothane as the inhalation agent. Additional analgesia was given with 10 mg of carprofen (Rimadyl, Pfizer) by sub- cutaneous route and antibiotic cover was provided with 85 mg ampicllin LA (Amfipen LA). The ventral neck was clipped and prepared as in paragraph 1 of Appendix 1, extending caudally to the cranioventral thorax and cranially to include all the ventral neck.

The cat was moved to theatre and placed in dorsal recumbency with the abdomen supported in a bubble wrap lined cradle. The neck was extended and a sand bag placed underneath. The forelimbs were extended and tied caudally. The skin was then prepared as in paragraph 2 of Appendix 1. Four drapes were placed to leave a rectangular window, leaving the surgical site as the only part of the cat exposed. See figure 1 on the right. A standard kit was laid out as listed in Appendix 2. Additional instruments included iris scissors and fine rat tooth forceps.

Surgery
An incision through the skin was made from the larynx, on the ventral neck, extending for 5 cms. The sternohyoid and sternothyroid muscles were bluntly separated to expose the left thyroid gland. The right gland was not visible at this point as it was located behind the trachea, which explains why it was not clinically palpated despite also being large. A decision was made at this point to perform a bilateral thyroidectomy. Using iris scissors and fine rat toothed forceps the thyroid gland was removed from both the caudal and cranial parathyroid glands by careful sharp and blunt dissection. Both the cranial and caudal thyroid blood vessels were preserved and did not need ligating. All the visible thyroid tissue was removed from the parathyroids. The process was repeated with the left side and although no ligating was necessary there was suspicion that the caudal parathyroid might be damaged. The muscles were closed using 3 m chromic catgut (Ethicon) using a simple continuous suture pattern and the skin was closed with 2 m polyamide (Nylonamide, Animus) using simple interrupted sutures. The cat had an uneventful recovery and went home the same day, with instructions to the owner regarding post-operative complications. The cat was seen two days later and was eating well and had no signs of hypocalcaemia. Sutures were removed after 10 days and there were still no signs of hypocalcaemia. Three weeks after surgery the cat had increased it's weight by 0.3 kg and a further blood test showed T4 levels at 7.6 nmol/l (slightly low). Heart rate was 172 p min and systolic blood pressure down to 130.

Discussion
Hyperthyroidism usually occurs in cats over 8 years old, with an average age of 13 years. Symptoms can include weight loss, polyphagia, tachycardia, lethargy, rough coat, change of character, and it is often associated with cardiac abnormalities, hypertension and renal failure. Blood tests will show elevated T4 levels. The condition can be treated medically, surgically, or with Iodine 131. The type of treatment selected will depend on the renal function, age, cardiac function and owner preference. Owners need to be advised of the possible post-operative complication of hypocalcaemia, more commonly occurring when bilateral thyroidectomies have been performed. Removal or disruption of the parathyroids which are closely associated with the thyroids can result in an inability to increase calcium levels in the body, leading to ataxia, tremors, coma and death. This is likely to occur within the first few days and the cat should be kept inside for observation and the owners should phone immediately if symptoms appear, as the cat may need intravenous calcium gluconate. Other surgical complications include Horner's syndrome, hypothyroidism, laryngeal paralysis and recurrence of hyperthyroidism. The draping of this patient was good, with no possibility of contamination of the surgeon by any part of the cat. Analgesia was good in the choice of an opioid and non steroidal and the cat was quite comfortable post-operatively. Pre- operative use of drugs are important for this surgery. The Inderal is given to reduce the blood pressure and for management of sinustachycardia and the NeoMercazole is given to reduce the levels of T4 production. Both of these help reduce the risks of general anaesthesia whilst performing the surgery. There are two techniques for performing a thyroidectomy in the cat. The intracapsular technique and the modified extracapsular technique. In this case the surgeon used a slight variation on the modfied extracapsular method. The surgeon feels that each thyroidectomy is different and that the technique she chooses will depend on a visual inspection of the glands. The post-operative T4 levels were slightly low but this is usually transitory and does not need treatment. Removal of both thyroids can be undertaken unilaterally 6 weeks apart. This does result in the cat having two anaesthetics and if surgery is performed competently the risks of bilateral surgery should be minimal. With regard to the antibiotics used, there was no evident pre-existing infection so a single dose of antibiotics should be adequate. Ideally the antibiotics should be working at the time of surgery and could have been given with the premedication. Placement of a sandbag under the neck assists with the surgery by moving the glands into a more accessible position. Placing the cat in a bubblewrap lined cradle and giving warmed fluids helps to preserve body temperature during general anaesthesia, particularly as this procedure is usually performed on very thin cats with little or no body fat. Alternative suture materials could have been used for this procedure, such as polyglactin 910, but cost of materials is important in a charity clinic and the surgeon has never encountered a tissue reaction using catgut for this particular procedure or had a problem with polyamide in the skin, so feels that it is not imperative to use other suture materials when performing thyroidectomies.

In summary, this was successful surgery as there were no post-operative complications and the aim of the surgery had been accomplished, ie the cat is no longer polyphagic or suffering weight loss and the T4 levels did return to the normal range after 2 months.

References:
Small Animal Surgery, T Fossum, Mosby. 1997

Case 5. Ovariohysterectomy due to pyometra

sabira mali — Fri, 24 Jul 2009 17:05:53 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:05:53 PM

OWNER	LATHAM	ANIMAL:	CASSIE
SPECIES:	DOG	BREED:	BULL MASTIFF
AGE:	10 MONTHS	SEX:	FEMALE
WEIGHT	34 KG	CONDITION:	BRIGHT

Clinical History
The dog was presented with a purulent vaginal discharge which the owner reported had been present for 1 week, following the bitch's first oestrus. The dog was inappetant, not polydipsic, had no vomiting, recorded a temperature of 38.6 C, had pink mucous membranes and a capillary refill time of 1 second. Generally the dog was fairly bright. Nothing abnormal could be palpated in the abdomen and a white blood cell count showed a high count of 38.2 10 9/L. The dog was admitted and put on a slow infusion of 1 litre of compound sodium lactate (Hartmann's, Ivex) overnight, and given an antibiotic injection of 225 mg of ampicillin (Norobritten, Norbrook) by subcutaneous route. The owners signed a consent form for any necessary surgery and general anaesthesia. A pre-anaesthetic clinical check revealed no respiratory or cardiovascular abnormalities.

Radiography
The following morning the dog was sedated with 0.6 mg acepromazine (ACP, C VET) and 0.3 mg buphrenorphine (Temgesic, Schering Plough) by intramuscular route and a right lateral radiograph of the abdomen was taken under sedation. The radiograph confirmed the diagnosis of a pyometra. See radiograph 1 right.

The dog which had been starved overnight was started on a further infusion of Hartmann's, and one hour later was given a general anaesthetic in order to perform an ovario- hysterectomy.

Surgical preparation
General anaesthesia was induced with 180 mg propofol (Rapinovet, Schering Plough) by slow intravenous injection, given to effect. Endotracheal intubation was achieved using an 11 mm cuffed tube. The dog was connected to a semi-closed parallel Lack circuit with a 4L resevoir bag. Flow rates of 4L nitrous oxide and 2L oxygen were used, together with halothane as the inhalation agent, in order to maintain anaesthesia. Further analgesia was given with 13 mg of carprofen (Rimadyl, Pfizer) by subcutaneous route. The antibiotics were also repeated. The dog was placed in sternal recumbency and an area was prepared (as in the first paragraph of Appendix 1) extending from the vulva to the ziphisternum, and 4 cms lateral to the mammary glands on either side. The bladder was expressed manually and the dog was moved into theatre, where it was placed in dorsal recumbency with the thorax supported in a cradle. The hind legs were extended and tied caudally and the surgical site was prepared as in the second paragraph of Appendix 1. See Figure 1 above.

A standard kit (as listed in Appendix 2) was laid out, with 6 additional spey forceps and 8 additional swabs.

Surgery
The surgeon draped the surgical site using 4 drapes arranged to leave a rectangular area exposed, over the midline. A swab count was taken before surgery commenced and a written tally was recorded as 10 swabs. An incision through the skin and subcutaneous tissue was made along the midline just caudal to the umbilicus, extending cranially for approximately 9 cms. This exposed the linear alba, which was grasped and elevated whilst a stab incision was made through it into the abdomen. Blunt Mayo scissors were used to extend the incision to the length of the skin incision, exposing the abdominal contents. The bladder was lifted out of the abdomen and reflected caudally. Both horns and body of the uterus were then lifted out of the abdomen and the body reflected caudally. See Figure 2 above.

The suspensory ligament of the left ovarian pedicle was identified and carefully broken, to allow better exteriorization of the ovary. An assistant gently applied caudal and medial traction to the uterine horn in order to allow the surgeon to apply a ligature, using 4 m polyglactin 910 (Vicryl, Ethicon), 2 cms proximal to the ovary around the ovarian pedicle. A second ligature was placed 1 cm proximally to the first. Then 2 pairs of large spey forceps were used to clamp the ovarian pedicle, both placed distal to the ligatures but proximal to the ovary. The ovarian pedicle was then transected between the two forceps. The forcep remaining on the stump was left in place, and the uterine horn broken away from the remaining ligament and reflected caudally. The process was repeated with the right ovarian pedicle which lies further cranially resulting in the access to this pedicle being more restricted. Cranial traction was then applied to the body of the uterus and a transfixation ligature was placed cranial to the cervix around the body of the uterus. A second, circumferential, ligature was placed nearer to the cervix both with 4 m Vicryl. Two large forceps were placed cranial to the ligatures and the uterine body transected between the two clamps. All three stumps, in turn, had small artery forceps attached to the edge and the large clamps released so that any haemorrhage could be observed. All three had slight oozing and a third ligature was applied to each one. This proved satisfactory and all stumps were replaced into the abdomen. A swab count at this time only showed 9 swabs accounted for. After a recheck the abdomen was searched and the swab was found in the abdomen. The midline was closed with 3 m polydioxanone (PDS II, Ethicon) using interrupted cruciate sutures. The fascia and linear alba were included in the suture, but not the peritoneum. Subcutaneous tissue was closed with 3 m PDS using a simple continuous pattern. Skin was closed with 3 m polyproplene (Ethilon, Ethicon) using a continuous Ford Interlocking suture pattern. Both ovaries were examined after surgery and found to be enlarged, the left having cyst like structures present. Post-operative recovery was uneventful and the dog went home the same day with 10 Rimadyl 50 mg tablets to be given one twice daily with food and 20 Ampicillin 250 mg capsules to be given two twice daily, both to start the following day. If the owners are allergic to penicillin themselves they must wear gloves to administer the capsules.They were advised to get an Elizabethan collar and only to give lead exercise for 5 days. They were also warned to watch the dog's weight after the post-operative period as neutered dogs have a tendency to put on weight. A post-operative check two days later was satisfactory and the sutures were removed after 10 days.

Discussion
Pyometras usually occur in middle aged bitches, and 10 months is quite unusual for this condition. Pyometras can be either open (discharging from the vulva) or closed with no discharge. Generally the latter are usually more likely to be showing more severe symptoms. Medical treatment rarely works and surgery is the option for relieving this condition, which is fatal if left untreated. Although a very common surgical procedure there are several life threatening complications associated with the surgery, coupled with the fact that the animal is quite often very toxic and often collapsed. Incorrect placing of the ligatures on the uterus can lead to them slipping off post-operatively, leading to fatal haemorrhage. Quite often the tissues are very friable and can rupture when being handled, again either leading to serious haemorrhage or contamination of the abdomen with pus which can lead to peritonitis. The bladder was expressed prior to surgery to reduce it's size as much as possible to allow better access within the abdomen. A male dog would also have the risk of passing urine into the abdominal cavity.

With regard to choice of suture materials, despite correct placing of the ligatures all three stumps were oozing after ligation and had to have a third ligature placed on each. Discussion of this point with the surgeon revealed that this was a problem which sometimes occurred when using Vicryl, but not when using chromic catgut. This would imply that it is more difficult to tighten the ligature using Vicryl and that chromic catgut might be a more suitable ligature material. PDS was used to close the subcutaneous tissue in this case, which is more suitable than chromic catgut, as the catgut can provoke a tissue reaction. With regard to suture patterns, simple interrupted could have been used instead of cruciate sutures for the midline but cruciate sutures were considered quicker and are equally efficient. The skin was closed using a continuous Ford Interlocking pattern for speed, but the disadvantages of this type of suture pattern is that it is more difficult and therefore more stressful to remove them. Secondly, if the animal chews at the wound a break in any part of the suture pattern can result in the whole wound opening whereas if an interrupted suture is removed there will only be a small gap in wound closure. This is especially important in an abdominal wound. The importance of conducting a swab count was well demonstrated in this case. Had the number of swabs not been recorded the missing swab would have gone unnoticed and remained within the abdomen, with serious consequences post-operatively.

Draping was carried out with cloth drapes and ideally should have also had a barrier drape to prevent bacterial strike through occurring when the drapes got wet. Analgesia was adequate for the procedure by combining a partial agonist with a non steroidal, although the non steroidal could have been given at the time of premedication to achieve the maximum analgesia during surgery. Rimadyl was a good choice of post-operative analgesia as it can be continued at home and only needs to be given every 24 hours. It is important to warn owners that penicillin can be absorbed through the skin as they have testified, several times, that they have been quite ill after disregarding this advice. Penicillin would appear to be an adequate antibiotic for this procedure and rarely needs a further course to restore the animal to full health. The first injection was given 15 hours prior to surgery and was therefore active during surgery. The outcome of this surgery was successful and the dog did not need to revisit after suture removal.

References:
Anatomy of the Dog, Miller. Saunders 2nd Ed.
1979 Small Animal Surgery, T Fossum. Mosby. 1997

Case 2. Cystotomy & removal of uroliths

sabira mali — Fri, 24 Jul 2009 17:03:52 GMT

Current Revision posted to Dip AVN Cases by sabira mali on 7/24/2009 5:03:52 PM

OWNER	MERTENS	ANIMAL:	BECK
SPECIES:	DOG	BREED:	JACK RUSSELL
AGE:	7 YEARS	SEX:	FEMALE
WEIGHT	11 KG	CONDITION:	OBESE

Clinical History
The dog was presented with dysuria and haematuria for a duration of two weeks. On palpation of the bladder numerous stones could be felt. The owner was warned that surgery would be needed and the risks of general anaesthesia in an obese animal were explained. The dog was booked for radiography and surgery the following day and was given a course of tablets containing trimethroprim 80mg and sulphamethoxazole 400mg (Co-Trimoxazole, Regent), to be given half a tablet twice daily.

Radiography
On 23/12/98 the dog was admitted for a general anaesthetic, having been starved over night with access to water two hours prior to surgery. A pre-anaesthetic check revealed no thoracic or cardiovascular abnormalities. Temperature was 38.2 C, pulse 114 per minute and respiration 31 per minute. The owners signed a consent form and the dog was premedicated with 0.6 mg acepromazine (ACP, C VET) by subcutaneous route, 45 minutes prior to surgery.

Induction was achieved using 175 mg thiopentone sodium 2.5% (Intraval Sodium, Rhone Merieux) and a cuffed size 7.5 endo-tracheal was used to intubate. The dog was placed on a semi-closed parallel lack circuit with flow rates of 4 litres of nitrous oxide and 2 litres of oxygen and 1.5% halothane. A 23g intravenous catheter was placed aseptically into the cephalic vein and a slow infusion of 500 mls Hartmann's was started. Analgesia was given with 3 mg morphine sulphate by intra-muscular route. Antibiotic cover was provided with 165 mg trimethoprim-sulphadiazine 7.5% (Borgal, Hoescht Roussel) given intra-venously.

A radiograph of the abdomen in right lateral recumbency was taken to confirm the location of the uroliths, including the kidneys. The radiograph revealed that all the uroliths were located in the bladder. See radiograph 1 above.

Surgical preparation
The ventral abdomen was prepared, as in the first paragraph of Appendix 1, covering an area from the ziphisternum cranially to the vulva caudally, and laterally 10 cms either side of the midline. The dog was moved to theatre and placed in dorsal recumbency (supported by a cradle) with both hind legs extended and tied out. The ECG electrodes were attached on the limbs just proximal to the stifle and olecranon. Skin cleansing took place as described in the second paragraph of Appendix 1.

Surgery
The area of the incision site was then draped by the scrubbed surgeon using four barrier drapes arranged in a quadrant, leaving only the midline exposed. See figure 1 on the right.

The instruments in this procedure included two standard surgical kits, as described in Appendix 2. In addition to this a sterile bowl, two 20 ml syringes, a 23 g needle, sixteen swabs and 0.9 % saline were used.

An incision was made through the skin and subcutaneous tissue along the midline, starting 2 cms cranial to the pubic symphysis and extending for 10 cms. Blunt dissection revealed the abdominal wall which was grasped with rat toothed forceps and lifted. A stab incision was made through the tissue and blunt mayo scissors were used to lengthen the incision to the extent of the skin incision. The bladder was located and lifted out of the abdomen, reflected caudally and laid on swabs. A stay suture using 3 m monofilament nylon (Monilon, Arnolds) was placed in the cranial bladder. Other swabs were then packed in the abdominal wound to minimise contamination by the bladder contents. Cystocentesis was performed with a 20 ml syringe and 23 g needle to remove as much urine as possible. A 2 cm incision was made into the dorsal aspect of the bladder, taking care to avoid the visible blood vessels. Numerous uroliths, ranging from 1 mm to 1.4 cms, were removed from the bladder. See Figure 2 below.

The bladder was then flushed using a sterile 20 ml syringe and sterile saline to ensure all uroliths had been removed. The bladder was closed with 2 m polyglactin 910 (Vicryl, Ethicon) on a round bodied needle using a double layer of simple interrupted sutures, the first layer including the mucosa and submucosa and the second including the muscularis and serosa.

All used swabs were removed and counted, the bladder replaced within the abdomen and the abdominal cavity was flushed with 0.9% saline. At this time the surgeon changed surgical gloves and a fresh surgical kit was used to close the abdominal wound. The abdominal wall was closed using 3 m polydioxanone (PDS II, Ethicon) on a cutting needle with simple interrupted sutures. The subcutaneous tissue was closed with 3.5 m chromic catgut (Ethicon) on a cutting needle using a simple continuous suture. Skin was closed with 3 m polyamide (Nylonamide, Animus) on a cutting needle using horizontal mattress sutures.

Post-operative period.
Recovery was uneventful, the dog being in sternal recumbency within 30 minutes of the end of anaesthesia. On recovery the dog was given 24 mg of ketoprofen (Ketofen 1%, Rhone Merieux) by intramuscular route. The dog was sent home later in the day with 2 Ketofen 20 mg tablets, half to be given daily with food, to start the following day. The owners were advised to watch for urination and revisit in the morning if the dog could not urinate. They were also told to expect haematuria and that they should finish the course of antibiotics previously prescribed for the dog. The calculi were sent off for analysis to the Minnesota Urolith Centre, University of Minnesota, USA. The dog returned 3 days later for a satisfactory post-operative check and the sutures were removed after 10 days. The owners were then told to revisit when the results of the calculi analysis returned.

Discussion
There are many causes of urolithiasis, including genetics, diet, obesity, inactivity, infectious agents or systemic disease. Therefore surgical removal of uroliths is not a cure. The owner was warned that, as uroliths reform in 1 in 4 dogs, (Hills Pet Products Data Sheet), permanent dietary management would be necessary for the dog. In this particular case, despite the bladder being full of calculi, the radiograph showed none in the urethra and the bitch was still able to pass urine with difficulty. Male dogs are more susceptible to obstruction of the urethra by calculi due to natural constrictions in the urethra - the most important being at the site of the os penis.

Results from Minnesota showed that the chemical composition of the uroliths was comprised of both calcium phosphate and magnesium ammonium phosphate. Some types of calculi, eg struvite (magnesium ammonium phosphate) can be dissolved by dietary management and treatment with antibiotics of the urinary tract infection which usually precedes formation of struvites (Minnesota Urolith Centre).Therefore it would be advisable to send off a urine sample for bacterial culture to ensure the correct antibiotic was used. This type of treatment would be suitable for male cats after placement of a urinary catheter due to obstruction by calculi. Manufacturers, eg Hills, produce a diet called s/d which is low in protein, magnesium, phosphate, high in sodium and produces acid urine. This diet is intended for short term use for the dissolution of struvite calculi. Struvites form in alkaline urine but become highly soluble in acid urine below pH 6.4. Hills also produce a long term maintenance diet which is called c/d to maintain acidity of the urine, to prevent struvites reforming. Other diets are available for different types of calculi. There is no dissolution diet available for calcium phosphate. Dissolution was not an option in this dog's case due to amount and size of calculi and condition of the dog.

Complications of this type of surgery include contamination of the abdomen, which could result in peritonitis. Therefore great care has to be taken to avoid spillage of urine into the abdominal cavity. Another post-operative complication is failure to remove all calculi, resulting in further obstruction. Prior to closure of the bladder the urethra should be flushed with sterile saline to ensure removal of all calculi. Other considerations in this type of surgery which involves large amounts of flushing with saline involve bacterial strike through via wet drapes and hypothermia of the patient due to excessive wetting of the skin, causing temperature loss through evaporation. Barrier drapes are essential to avoid both of these from ocurring. Also, saline should be heated to body temperature before flushing as this will help preserve body temperature. Water heated pads are not available in this clinic but bubble wrap was used to wrap limbs prior to surgery in order to conserve body temperature.

With regard to analgesia, carprofen would have been the choice of non steroidal anti- inflammatory drug, as it is the only one of the group which is considered safe to use peri-operatively due to its lack of effect on the body's prostaglandin production. However, due to a manufacturing problem it was not available at the time of surgery and ketoprofen was used as the NSAID. This could not be administered peri-operatively due to its adverse effects on prostaglandin production, possibly causing renal failure or ulceration of the GI tract. Therefore morphine was selected for intra-operative use, in conjunction with nitrous oxide. It would have been preferable for the morphine to be given in the premedication to allow it to be active at the time of the first incision. The only disadvantage of giving morphine pre-operatively is that vomiting can occur shortly after administration - this is rarely a problem in a conscious animal.

A blood sample was taken to check the function of the parathyroid gland, as this is recommended in cases of calcium phosphate calculi, as excess levels of calcium are thought to be the precursor to these calculi. However, the results of the blood sample showed normal levels of calcium (2.4 mmol/l). Therefore the owner was told to feed Hills s/d exclusively for 2 months and then to change to Hills c/d diet permanently. The owner could also have been told to check the pH of the dog's urine daily and to revisit if the urine showed alkalinity for more than 2 days. (Manual of Canine and Feline Nephrology and Urology, BSAVA).

References:
Anatomy of the Dog, Miller, Saunders 2nd Ed 1979, Ch 9.
Current Techniques in Sm An Surg, Bojrab, 3rd Ed, Lea & Febiger 1990.
Clinical Management of Canine & Feline Urolithiasis, Hills 1991.
Minnesota Urolith Centre, Clinical Data Sheet Rev 1996.
Manual of Can & Fel Nephrology & Urology, BSAVA 1996, p 216,217.

Case 1. Splenectomy

sabira mali — Fri, 24 Jul 2009 17:01:16 GMT

Revision 3 posted to Dip AVN Cases by sabira mali on 7/24/2009 5:01:16 PM

OWNER	PIERCE	ANIMAL:	JASPER
SPECIES:	DOG	BREED:	XB
AGE:	10 YEARS	SEX:	MALE NEUTER
WEIGHT	29 KG OBESE	CONDITION:	BRIGHT

Anaesthetic Cases - Appendix

Arlo Guthrie — Wed, 22 Apr 2009 11:38:58 GMT

Revision 1 posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:38:58 AM

Equipment available for anaesthesia

Piped gases from external bunker using 6800L Oxygen cylinders and 3400L Nitrous Oxide cylinders.
Active scavenging piped to outlet on roof.
Ex-hospital anaesthetic machines with low oxygen alarms, fitted with emergency E size oxygen cylinders and Fluotec Mark 3 vaporisers which are calibrated for use with Halothane.
Anaesthetic chamber, connected to scavenging system, for use with small animals.
ECG machine
Pulse oximeter
Respiration monitor (ap-Alert)
Heated operating table
Magill semi-closed circuit, used with various face masks.
Parallel Lack semi-closed circuits
Co-axial Bains semi-closed circuits
Ayre's T-Piece semi-closed circuits, all with Jackson Rees modification
Circle closed circuit
Oxygen tent for cats and small dogs
All sizes of cuffed and uncuffed endotracheal tubes
Laryngoscope
Oesophageal stethoscopes
Reservoir bags ranging from 2L to 5L

Drugs available for anaesthesia and premedication

Thiopentone Sodium (Intraval Sodium, Rhone Merieux) 2.5%
Propofol (Rapinovet, Coopers)
Halothane
Ketamine (Vetalar, Parke-Davis)
Pentobarbitone Sodium (Sagatal, RMB) - this is only used for fitting animals
Medetomidine (Domitor, SKB)
Atipamezole (Antisedan, SKB)
Xylazine (Rompun, Bayer)
Fentanyl/Fluanisone (Hypnorm, Janssen)
Atropine Sulphate 0.6 mg/ml (Atrocare, Animal Care)
Glycopyrrolate (Robinul, Robins)
Acepromazine 2mg/ml (ACP, C Vet)
Diazepam 10mg in 2mls (Valium, Roche)
Butorphanol 10mg/ml (Torbugesic, Willows Francis)
Morphine Sulphate 10mg/ml (Evans)
Pethidine 50mg/ml (CD)
Buprenorphine 0.3mg/ml (Temgesic, Reckitt & Coleman)
Adrenaline 1mg/ml (Phoenix)
Digoxin 0.5mg in 2mls (Lanoxin, Wellcome)
Naloxone hydrochloride (Narcan, Du Pont)
Doxapram hydrochloride 20mg/ml (Dopram V, Willows Francis)
Calcium gluconate 2.2 mmol/10mls (Phoenix)
Suxamethonium (Anectine, Wellcome)
Lidocaine hydrochloride 2% (Intubeaze, Arnolds) spray
Lidocaine hydrochloride 2% (Xylocaine Gel, Astra Pharm)
Dobutamine 12.5 mg/ml (Dobutrex)
Compound sodium lactate (Hartmanns)
Sodium chloride 0.9% (Saline)
Haemaccel 5L

Case 3. Bone marrow biopsy

Arlo Guthrie — Wed, 22 Apr 2009 11:35:37 GMT

Revision 1 posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:35:37 AM

OWNER	ABBOTT	ANIMAL:	CINDY
SPECIES:	DOG	BREED:	G RETRIEVER
AGE:	8 YEARS	SEX:	FEMALE NEUTER
WEIGHT	27.5 KG	CONDITION:	BRIGHT

Clinical History.
The dog was presented with a subcutaneous mass just cranial to the right proximal humerus. A needle aspiration biopsy was taken and the mass proved to be a mastcell tumour. Complete surgical removal was considered to be impossible due to it's infiltrative nature. So a bone marrow biopsy was arranged, to check for metastases before the dog underwent radio therapy. The dog was prescribed 36 mg prednisolone once daily until the general anaesthetic. The owners were warned of the risks of general anaesthesia and signed a form giving permission for a general anaesthetic and surgery.

Pre-anaesthetic examination.
Bloods were taken for haematology and biochemistry profiles, the results of which were unremarkable. See anaesthetic record. Auscultation of the pulmonary and cardiovascular systems did not reveal any abnormalities. Temperature was 38.4 C, heart rate 96 per min and respiration 24 per min. The dog had been starved for 10 hours with access to water until 2 hours prior to induction.

Premedication.
Premedication consisted of 0.28 mg of glycopyrrolate (Robinul, Robins), 8.25 mg of butorphanol (Phoenix) and 55 mg diphenhydramine (Abbott) all by intramuscular route. The premedication worked extremely well and the dog was very quiet and sedate at the time of induction 20 minutes later. Prior to induction an 18 guage intravenous catheter was placed aseptically into the right cephalic vein.

Induction.
Induction was achieved using 13.8 mg diazepam (Elkins-Sinn), followed by titration of 129 mg of 2.5 % thiopentone sodium (Phoenix), both via the intravenous catheter. Intubation was performed with an 11 mm cuffed endotracheal tube and positioned by palpation of the uninflated cuff at the thoracic inlet. The tube was connected to a circle circuit with 2 L of oxygen. The cuff of the endotracheal tube was slowly inflated whilst the reservoir bag was very gently squeezed with the valve closed, and inflation was stopped when sounds of gas passing round the tube were no longer heard. An ECG monitor was connected to the dog, the electrodes being placed just proximal to the stifles and olecranons. An area just distal to the stopper pad on the palmar aspect of the left forelimb was clipped and a Doppler sensor taped on, after application of conducting gel, in order to monitor blood pressure. The dog was placed on a water heated pad for the duration of anaesthesia. See picture right.

Maintenance of general anaesthesia.
The valve on the circuit was opened and maintenance of anaesthesia was achieved using 1 L oxygen with isoflurane at 2% reducing to 1.5 % after 45 minutes. Lactated Ringers crystalloid was given at a rate of 10mls/kg/hr for the duration of anaesthesia. For a detailed account of anaesthesia see attached record sheet. The heart rate was recorded at between 70 and 75 bpm for the first 20 minutes, and then began to decrease steadily over the next 10 minutes to 50 bpm. The systolic blood pressure (BP) had only fallen slightly, to 115 mm Hg. A bolus of 0.137 mg of glycopyrrolate (Robinul, Robins) was given at this time by intravenous route. The ECG trace showed a second degree AV heart block for a duration of approximately 1.5 minutes, before returning to normal complexes. The heart rate peaked at 120 bpm 2 minutes after administration of the glycopyrrolate and the systolic BP rose to 160 mm Hg. The heart rate fell gradually over the next 20 mins and was recorded at 88 bpm on extubation. The systolic BP fell to 115 mm Hg and was recorded at 130 mm Hg at extubation. Respiration was spontaneous throughout anaesthesia, with good chest excursion, and recorded at between 20 - 30 per min. It was not considered necessary to ventilate the dog. The dog did not lose any temperature during the course of general anaesthesia. Duration of anaesthesia was 57 minutes.

Post-operative period.
The dog was extubated 5 minutes after the end of anaesthesia and the pulse at this time was 96 per min, respiration 36 per min and temperature 38.1 C. The bladder was reasonably full and was manually expressed before the dog was put into a recovery kennel. Sternal recumbency was achieved 10 minutes after extubation and recovery was quiet. The dog went home the following morning, to return in 3 days for a post-operative check and 10 days for sutures out and the biopsy results. This case was conducted in the University of Georgia and I was no longer present when the biopsy results were received.

Discussion.
The condition, age of the animal and the type of surgery being performed are all important when deciding on a suitable general anaesthetic procedure and the possible complications which could arise. All of this should be discussed prior to anaesthesia so that a fast, suitable course of action can be taken if a crisis occurs, and hopefully selecting the most suitable agents will reduce the risk of such crises occurring. An animal should always be weighed prior to anaesthesia, as correct dosing of drugs can be critical, especially in older animals which may not even need the full calculated dose. This was suspected in this case and a note made prior to induction to titrate the thiopentone slowly in order to avoid overdose. There are differing views as to when an animal should be classed as a geriatric, and there is also the 'real' age of the animal to be considered, ie whether the animal's general condition would lead to an assumption that it is older or younger than it's birth age. In this case the University of Georgia state that a dog of this breed over 7 years old is classed as an old dog and this dog's 'real' age would be even older due to it's condition. This would mean that it is more likely to suffer from hypotension, hypothermia and hypoventilation under anaesthesia and would probably need reduced anaesthetic doses.

References:
Veterinary Anaesthesia, Hall & Clarke, Saunders, 9th Ed 1991
Manual of Anaesthesia, BSAVA 1992
Prof C Trim, BSAVA Congress 1999
Prof C Trim 1999 - visit to University of Georgia, USA

Case 2. Biopsy Mass

Arlo Guthrie — Wed, 22 Apr 2009 11:31:21 GMT

Revision 2 posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:31:21 AM

OWNER	TWIST	ANIMAL:	CRICKET
SPECIES:	DOG	BREED:	AMERICAN SPITZ
AGE:	11 YEARS	SEX:	FEMALE
WEIGHT	9.3 KG AVERAGE	CONDITION:	DYSPNOEA

Clinical History.
The dog was first brought in by the owner for respiratory distress. Stridor was evident on inspiration, visual examination revealed an intra-oral mass occluding the glottis and palpation of the neck revealed a mass present in the caudal oropharyngeal area over the larynx, dorsal to the trachea and about 5 cms in diameter. Exopthalamus was also noted. There were no other clinical symptoms. The owner reported that the dog had become increasingly more dyspnoeic over the last 2 months. A general anaesthetic for radiography and a biopsy was arranged for the following morning, the owner having been warned of the risks of general anaesthesia and having signed a consent form.

Pre-anaesthetic examination.
Blood samples were taken for both biochemistry and haematology profiles, the results of which were unremarkable. See anaesthetic record sheet. A clinical examination revealed temperature of 38 C, heart rate of 100 per min and respiration rate of 20. There were no apparent abnormalities of the cardiovascular or respiratory system, other than the mass. The dog was kept overnight in an oxygen cage in the intensive care unit (ICU) and starved from 10 pm with access to water until 8 am. The dog was given a class 3 anaesthetic risk, ie a patient with severe systemic disease that is not incapacitating.

Premedication.
Premedication consisted only of 0.37 mg atropine sulphate (Phoenix) given by intra- muscular route 30 minutes prior to induction. After premedication the dog was monitored constantly until induction.

Induction.
As difficulty of intubation was expected, due to the occlusion of the glottis, equipment was available for a tracheotomy and also an endoscope for assistance with intubation. Five minutes pre-oxygenisation was given via a mask before induction. The dog was quite calm prior to and during induction. A 20 g intravenous catheter was placed aseptically into the right cephalic vein. A smooth induction was achieved using 74 mg propofol (Diprivan, Zeneca) given slowly through the catheter. Intubation was performed successfully using a 6.5 mm cuffed endotracheal tube. Correct placing of the ET tube was carried out by palpating the thoracic inlet area with one hand whilst moving the tube in and out slightly in order to feel where the uninflated cuff was positioned. Correct inflation of the cuff was achieved by one person slowly inflating the cuff and listening by the mouth whilst a second person closed the valve on the circuit (which had been connected to the tube and 2 L oxygen turned on) and very gently squeezing the resevoir bag until no sounds of gas passing round the cuff could be heard and pressure was felt squeezing the bag. The dog had been connected to a circle circuit with oxygen flow of 2 L per min which was reduced to 1 L after 20 minutes. Isoflurane was used as the maintenance agent with initial settings of 2%, being reduced to 1% after 35 mins. An infusion of lactated ringers was started at a rate of 10ml/kg/hr. An area just distal to the stopper pad on the palmar surface of the left foreleg was clipped, conducting gel applied and a Doppler sensor attached with tape. A cuff was applied to the left proximal foreleg in order to measure blood pressure (BP). 0.465 mg of oxymorphone (Numorphan, Du Pont) was given by intravenous route.

Radiography.
The dog was radiographed which showed a mass consistent in size and position as described in the clinical examination. A biopsy was then taken through an incision in the right lateral neck.

Post-operative progress.
Two hours after recovery the telemetry started showing abnormal traces and a cardiologist was called to interpret the trace. His recommendation was that the dog be monitored at all times, but that treatment was not necessary at this time. The dog remained in an oxygen cage for 48 hours, by which time the ECG trace had returned to normal and the dog was showing less dyspnoea than when it was first admitted. It was sent home the following day after being out for exercise and not showing any signs of dyspnoea. The owners were advised to restrict the dog to lead exercise and return in 3 days and 10 days for suture removal and biopsy results. It was not clear at this stage whether a tumour was present or whether the mass was in fact an aneurysm. If the results showed a tumour the dog would have radiotherapy as it was not possible to remove any more tissue. As this case was conducted in the University of Georgia, USA I was no longer present when the biopsy results came back.

Discussion.
The protocol for this general anaesthetic was discussed prior to induction and drugs were chosen to suit the animal's condition at the time of surgery. Possible complications were also discussed and provision made for dealing with these, ie the tracheotomy site was prepared and all equipment ready to use. This is very important as quick action needs to be taken and time is wasted making decisions after the crisis has occurred. The animal's life may also be at risk if necessary equipment is not at hand. However, this anaesthetic also proved that no matter how much planning takes place emergencies can always happen unexpectedly despite all possible precautions, ie the anaesthetic implications of ligating the carotid artery, which was also not expected. Only atropine was given as premedication, as there was concern that any sedative would cause further respiratory distress before an airway was secured. Atropine is an anticholinergic drug which was given to inhibit secretion of saliva and protect against bradycardia. Anticholinergics are standardly included in pre- medications in the University of Georgia, but other views held are that it should only be given if necessary, ie for bradycardia or if surgery might provoke a vagal response. Respiratory depression was also the reason that the oxymorphone was not given until after the dog was intubated, as although oxymorphone is ten times stronger than morphine, but has less effect as a depressant on the respiratory system, there is still some depression.

Overall, this was a complicated general anaesthetic which was well planned and managed, which demonstrated the usefulness of monitoring devices for identifying complications.

References:
Veterinary Anaesthesia, Hall & Clarke, 9th Ed, 1991
Manual of Anaesthesia, BSAVA 1992
Small Animal Surgery, T Fossum. Mosby 1997
Prof C Trim, Head of Sm & L An Anaes, University of Georgia, US. Aug 99
BSAVA Congress Anaesthesia Lectures, C Trim. 1999

Case 2. Buiopsy Mass

Arlo Guthrie — Wed, 22 Apr 2009 11:31:07 GMT

Revision 1 posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:31:07 AM

OWNER	TWIST	ANIMAL:	CRICKET
SPECIES:	DOG	BREED:	AMERICAN SPITZ
AGE:	11 YEARS	SEX:	FEMALE
WEIGHT	9.3 KG AVERAGE	CONDITION:	DYSPNOEA

Overall, this was a complicated general anaesthetic which was well planned and managed, which demonstrated the usefulness of monitoring devices for identifying complications.

Case 1. Splenectomy

Arlo Guthrie — Wed, 22 Apr 2009 11:25:42 GMT

Revision 2 posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:25:42 AM

OWNER	PIERCE	ANIMAL:	JASPER
SPECIES:	DOG	BREED:	XB
AGE:	10 YEARS	SEX:	MALE NEUTER
WEIGHT	29 KG OBESE	CONDITION:	BRIGHT

Clinical History.
The dog was first presented for anal adenomas which were subsequently removed under general anaesthesia. A routine palpation of the abdomen whilst the dog was under anaesthesia revealed a mass which was diagnosed as a splenic tumour. As the owners had not given consent for this surgery the dog was booked in for removal of the spleen 2 weeks later, as the dog was not showing any clinical symptoms consistent with a splenic tumour. A blood sample to measure packed cell volume was taken pre-operatively and this was recorded at 0.47 L/L, which was normal. The owners were warned of the risks associated with general anaesthesia of an old, obese dog undergoing a splenectomy and were required to sign a consent form to allow general anaesthesia and surgery.

Pre-anaesthetic clinical examination and premedication.
The dog was admitted for general anaesthesia having been starved for 12 hours with access to water until 2 hours prior to premedication. A clinical pre-operative check revealed no thoracic or cardiovascular abnormalities. Pulse was 92 per minute, respiration 34 per minute and temperature recorded at 38.8 C. Mucous membranes (m/m) were pink and capillary refill time (CRT) was just under 1 second. Premedication was given with 0.6 mg of acepromazine (ACP C Vet) by subcutaneous route and 7 mg of morphine (Morphine Sulphate, Evans) by intramuscular route. A 20 guage intravenous catheter was placed aseptically into the right cephalic vein and an infusion of Hartmanns crystalloid was started at a rate of 10 mls/kg/hour. One hour later the premedication seemed to have had no effect. The dog was still excitable and quite aggressive, needing to be muzzled in order to carry out induction, having already bitten someone without warning whilst being taken out of the kennel.

Induction.
Induction was achieved with 110 mg of propofol (Rapinovet, Schering-Plough) by slow intravenous injection given to effect through the catheter, and a cuffed 12 mm endo- tracheal tube was used to intubate the dog. A semi-closed parallel Lack circuit with a 4L resevoir bag was used with flow rates of 4L nitrous oxide and 2L oxygen, and halothane was used as the inhalation agent. Additional analgesia was given after induction with 125 mg carprofen (Rimadyl, Pfizer) by subcutaneous route. Antibiotic cover was provided with 225 mg ampicillin (Norobrittin, Norbrook) by subcutaneous route.

Radiography.
A radiograph of the thorax in right lateral recumbency was taken to ensure that no metastases had occurred. The radiograph revealed no visible abnormalities and the dog was prepared for surgery and a total splenectomy was performed.

Maintenance of anaesthesia.
For a detailed account of general anaesthesia see attached anaesthetic record. Duration of anaesthesia was 150 minutes with the dog able to walk 40 minutes after the end of anaesthesia.

Post-operative recovery.
The dog was very excitable on recovery and only received 700 mls of the Hartmann's as it continually tied the giving set in knots. The morphine was repeated after 4 hours. A PCV taken the following morning recorded at 0.36 L/L and the dog had slightly pale m/m's. However, it was eating and temp was normal so it was sent home with 10 Rimadyl 50 mg tablets to be given one twice daily with food, and 10 Ampicillin capsules also to be given one twice daily to start immediately. A post-operative check two days later revealed a PCV of 0.37 L/L and the dog was very bright and eating well. Sutures were removed at 10 days and the PCV was last recorded at 0.42 L/L.

Discussion.
Anaesthetic protocols should always be planned to suit the animal's condition at the time of surgery and the procedure to be performed. In this case the dog was not collapsed, as the spleen had not ruptured prior to surgery. However, a splenectomy can result in several complications under general anaesthesia and special consideration should be given to anaesthetic protocols to minimise the risks. In addition this dog was obese which also adds to the possible anaesthetic risk. Firstly, a pre-operative PCV was taken to be able to compare with post-operative PCV's, as anaemia can be a post-operative complication. Also, anaemia would preclude the use of nitrous oxide (if severe). Anaemia would also affect the accuracy of the pulse oximeter, as it measures the levels of oxygen saturation of the haemoglobin, not whether there are enough red cells to carry sufficient oxygen to the tissues. ACP was given as a premedication but it probably would have been wise not to use it for two reasons. Firstly, one side effect of ACP is to produce hypotension, which in itself could be one of the complications of removing a spleen which contains a large volume of blood. The second reason for not using ACP is that it is not usually an effective sedative for aggressive animals. In fact it can release the inhibtions that prevent a dog from biting, which is what appeared to happen in this case. However, as the dog did not give any indication of aggression prior to premedication and the owner made no mention of this behaviour this was totally unforeseen. One advantage of ACP is that it protects the heart from catecholamines. Choice of induction agent and maintenance agent is important for splenectomies as they are at risk from premature ventricular contractions (PVC) during general anaesthesia. PVC's can result from drugs, hypoventilation, hypoxaemia, pulmonary and myocardial contusions following trauma, and inadequate depth of anaesthesia.Thiopentone sensitises the myocardium to catecholamines which increases the risk of PVC's, and also depresses the respiratory and cardiovascular systems, so this agent should be avoided. Although propofol also depresses the respiratory and cardiovascular systems it does not sensitise the myocardium as much as thiopentone, and would be preferred to thiopentone. Diazepam (0.25 mg/kg) could be given intravenously before the propofol, which would reduce the amount of propofol needed for induction. Or ketamine (5 mg/kg) and diazepam (0.25 mg/kg) in the same syringe could have been given intravenously as an alternative induction agent. The advantage of using ketamine is that it does not produce as much cardiovascular depression. One third to one half of the dose should be given, followed by titration to effect after 30 seconds to allow intubation of the trachea. The disadvantage of using ketamine is that monitoring of depth of inhalation anaesthesia cannot be assessed using eye position, and monitoring instruments would be necessary to avoid overdose. Thiopentone (a barbiturate) also causes congestion of the spleen with blood, which would increase the risk of hypovolaemia and hypotension when the spleen was removed, so this agent is unsuitable for this procedure. A disadvantage of using propofol as an induction agent is that elimination of the drug can occur quite suddenly and consequently the depth of anaesthesia can change rapidly. This did occur with this dog just prior to the first incision and, as the record shows, increased respiration and pulse rate indicated that the depth of anaesthesia at this point was not adequate. The halothane was increased to take the dog back down to a suitable depth of anaesthesia. Halothane, which was used as the inhalation agent also sensitises the myocardium to catecholamines and it would have been better to use isoflurane which does not. However isoflurane is not available at this practice due to cost. Another problem encountered early in the anaesthetic was hypoventilation, caused by placing the animal in dorsal recumbency, which resulted in hypoxaemia, due to obesity. When an obese animal is placed on it's back the abdominal contents impede the diaphragm's movement. A Lack circuit is not designed for prolonged IPPV as rebreathing expired gases can occur. To try and overcome this the flow rate was turned up to 8 L. Neither a Bains circuit or ventilator was available at the time. The inspiratory phase was kept short (1 - 1.5 secs) as venous return is impeded during the inspiratory phase. The pulse oximeter rose to 97% and the m/m returned to pink. Nitrous oxide is an analgesic and is usually used at a ratio of 2:1 with oxygen. Ten minutes oxygen time must be used after cessation of nitrous oxide to avoid diffusion hypoxia. Turning off the nitrous oxide would have contributed to the dog showing a pain response to surgical stimulation, so the nitrous oxide was put back on at the previous flow rates and IPPV assistance continued 3 - 4 times a minute to assist the dog's spontaneous breathing. This kept the pulse oximeter reading above 90% for the duration of anaesthesia. Respiration rates remained quite fast throughout anaesthesia and this was attributed to obesity. Because of the risk of PVC's it was important to use the ECG to monitor the heart. Lignocaine at 1mg/kg was available to treat any PVC's if necessary, ie more than 2 in a row occuring or any PVC's in conjunction with low blood pressure. It would be necessary to ascertain the cause of the PVC's before treating with lignocaine, ie if caused by hypoxaemia or inadequate depth of anaesthesia then rectifying those problems should resolve the PVC's. Also, stopping the halothane and using isoflurane might rectify the problem. If neither of these work then a bolus of lignocaine can be tried. Close observation on depth of anaesthesia should be kept when using lignocaine (particularly if an infusion is used) as it is an anaesthetic and can lead to deepening of the anaesthetic level.

References:
Small Animal Surgery, T Fossum. Mosby. p 450 1997
Anasethesia of the Critical Patient, C Trim. BSAVA Congress 1999
Principles of Anaesthesia. Cont Ed Course. BSAVA March 1999 L Hughes & R McMurphy

Anaesthetic Case Reports

Arlo Guthrie — Wed, 22 Apr 2009 11:25:14 GMT

Current Revision posted to Dip AVN Cases by Arlo Guthrie on 4/22/2009 11:25:14 AM

Please use the navigation on the right to navigate to the case reports.