ANSWERS

1. What is the purpose of pre-operative assessment?
   Pre-operative assessment is an essential consultation that should be undertaken with both patient and owner present; the purpose of which is to determine the animal's state of health and to minimise the risk of untoward events during anaesthesia and surgery. It is the responsibility of the veterinary surgeon to perform this assessment, but the veterinary nurse may assist in the following ways:
   • Recording data.
   • Ensuring that the consent form for anaesthesia and surgical procedure/s is signed (this is a legal requirement).
   • Restraint of the patient for examination
   • Performance of specific tasks under the direction of the veterinary surgeon such as pre-operative blood sampling and weighing the patient.
   • Liaison with the owner to ensure that it is known when to expect a progress report; reassure the owner by all means - but NEVER assume that everything is going to run smoothly; it must be appreciated that every anaesthetic possesses a degree of risk.
2. List useful equipment to have to hand during a pre-operative assessment.
   • Full patient history - particular care must be taken to note pre-existing medical conditions, current medication and any previous adverse drug reactions.
   • Scales - an accurate weight is essential in order to work out correct drug dosages.
   • Stethoscope - for mediate auscultation (listening to the heart).
   • Thermometer - for rectal temperature reading.
   • ECG machine - to record the electrical potential of the heart, if required.
   • Blood collection equipment - to enable relevant tests, for example blood urea and creatinine levels of a suspected renal case.
3. Describe briefly what is meant by a high risk case.
   A high risk case is a patient exhibiting pathological changes that exacerbate the effects of anaesthetic drugs; hence anaesthesia represents a greater danger than in a normal, healthy animal. Shocked or severely dehydrated animals are most at risk, while elderly patients pose certain degrees of risk due to medical conditions that commonly pre-exist such as renal dysfunction and obesity.
4. List the details that must be known prior to admission of a patient.
   • Owner's name.
   • Owner's address and telephone number.
   • An emergency contact telephone number if the owner is not at home (a work telephone number and/or mobile number are useful.
   • Species, breed, date of birth (this is more accurate than age), sex (including neutering status), colour and markings of the patient.
     Always take extensive details to avoid mistaken identities!
   • Vaccination status.
   • Insurance status; costs should not be an issue, but unfortunately in this day and age are important (if an estimate has been given, this should also be noted).
   • Details of any items left with the animal such as leads, collars, blankets and baskets.
   • Patient's weight; details of significant weight loss or gain should also be noted.
   • Date and time of anaesthesia and surgery.
   • Most importantly - precise details of the anaesthesia and surgery to be performed (anatomical diagrams can be most helpful).
   • Current therapy/medication (include any home remedies such as homeopathic medicines which are becoming increasingly popular).
   • Previous medical and anaesthetic history; any adverse reactions must be reported.
   • Time of last food/water intake.
   • Recent medical history as noted at the time of the pre-operative assessment; e.g. heart rate, respiratory rate, body temperature and blood parameters.
5. It is a legal requirement that a consent form is signed prior to anaesthesia and/or surgery; who may sign this form?
   • The owner of the patient providing that he or she is over the age of 18.
   • An agent acting upon behalf of the owner; this may be anyone from a friend, relative or neighbour to a solicitor or social worker.
6. When is the only time that anaesthesia and surgical procedures may be performed without the prior consent of the owner?
   Emergency cases where injuries are life-threatening; in such cases, the welfare of the animal is of paramount concern and emergency treatment may be performed without delay. A sadly only too common example are RTA cats brought to the surgery by a members of the general public where owners have not yet been identified.
7. List the 5 major emergencies that would indicate the need for immediate anaesthesia in order to perform surgery without regard to the condition of the patient.
   • Airway obstruction.
   • Uncontrollable haemorrhage.
   • Cardiac tamponade (impairment of the heart's function by haemorrhage or effusion into the pericardium).
   • Severe thoracic injuries.
   • Obstetrical emergencies where the neonates are at risk.
8. What considerations might affect the choice of drugs and dosage for premedication and anaesthesia?
   • Temperament, fitness and age of the patient.
   • Breed of patient; some breeds respond adversely to certain drugs, for example ACP causes syncope (fainting) in Boxers.
   • Anticipated complications.
   • Pre-existing conditions and concurrent medication.
   • Pain.
   • Type and duration of surgical procedure or examination to be undertaken.
   • Post-operative requirements; a patient may require immobilisation following a fracture repair and a smooth recovery is essential - Saffan which is commonly used in cats can cause a jerky response during recovery and an alternative induction agent might be preferable.
   • Facilities and assistance available.
9. The general demeanour of a patient offers a beneficial insight as to the risks representative of anaesthesia; explain how depression and excitement affect anaesthesia.
   • Depression may be indicative of intracranial pathologies, systemic disease or cardiovascular impairment; depression increases sensitivity to anaesthetics.
   • Excitement (including nervousness and aggression) may mean that profound sedation is required.
10. List visual observations that are helpful in the assessment of a patient prior to anaesthesia and explain their significance.
    • Signs of age, such as thickened skin and greying of the coat - elderly patients may have less efficient kidneys thus increasing their anaesthetic risk.
    • Sunken eyes and marked skin tenting - these are classic signs of dehydration; a severely dehydrated patient needs correction of electrolyte balance prior to anaesthesia, dehydration is often associated with shock which is contraindicated by anaesthesia.
    • Dental disease - severe dental disease may result in toxins circulating in the blood stream which may impair the uptake of oxygen by the blood cells.
    • Pale mucous membranes - another indication of shock and/or impaired circulation.
    • Respiratory distress - coughing may indicate the presence of airway secretions, while breathless may precede other signs of respiratory and cardiac failure by many months.
    • Obesity - this represents a serious risk factor to anaesthesia since it impairs both respiratory and cardiac function.
11. Palpation is very useful in pre-operative examinations; list areas that are commonly assessed by palpation.
    • Dryness of the mucous membranes, particularly the mouth = assessment of hydration status.
    • Skin turgor = assessment of hydration status.
    • Lymph node enlargement = assessment of the lymphatic system and endocrinology.
    • Pulse = assessment of the cardiovascular system.
    • Chest movement = assessment of the respiratory system.
    • Thrills (tremors detected by palpation) = assessment of the cardiovascular system.
    • Position of the cardiac apex beat = the beat of the heart against the chest wall which can be felt during systole.
    • Response to pain = assessment of the demeanour of the patient.
12. Define percussion and auscultation and explain why these techniques are an important part of a pre-operative examination.
    • Percussion = a method of diagnosis performed by tapping with the fingers or a light hammer in order to gain information as to the condition of underlying organs; useful in comparison of resonance over the chest wall.
    • Auscultation = examination of internal organs by listening to the sounds produced (directly via the ear or mediate via a stethoscope); the heart and respiratory system are commonly assessed in this way. Heart murmers due to valvular defects, patent ductus arteriosus or ventricular septal defects may be detected.
13. List cardiovascular and respiratory conditions that may be detected by percussion and auscultation.
    • Bradycardia = decreased heart rate; may be indicative of heart block (impairment of conduction in heart excitation.
    • Tachycardia = increased heart rate; may be indicative of fear, pain, fever or myocardial weakness.
    • Diastolic murmers = always indicative of heart disease.
    • Venous distension = elevated right atrial or ventricular pressure; may be indicative of chronic lung disease.
    • Rales = abnormal respiratory rattling sounds; indicative of fluid in the bronchi.
    • Rhonchi = wheezing sounds caused by partial obstruction of the bronchi; may be due to fluid, oedema or spasm.
14. Why does acquired heart disease represent more of a risk to anaesthesia than congenital heart disease?
    Aquired heart disease is more serious since it tends to affect both the myocardium and the heart valves. Examples include pericarditis (inflammation of the serous membrane covering the heart) and cardiomyopathy (dilated - involving thinning of the heart muscle, or hypertrophic - involving thickening of the heart muscle).
15. In addition to pre-operative haematology and biochemistry blood profiles, what other diagnostic techniques may provide the veterinary surgeon with important information?
    • Blood pressure monitoring.
    • Central venous pressure measurements
    • Radiography.
    • Electrocardiography.
    • Ultrasound.
    • Urine analysis.
16. Explain why an animal suffering hypoalbuminaemia is a high risk case.
    Low volumes of circulating blood albumin is likely to be indicative of liver or renal disease. Drugs such as thio-pentone are "albumin bound" and the lower the albumin levels, the more free thio-pentone is available. This decreases the oncotic pressure of the plasma thus promoting oedema and increasing the diffusion distance for gases in the lungs.
17. Why are diabetic patients considered high risk anaesthetic cases?
    A diabetic patient requires a strict feeding regime which may interfere with the usual starvation requirements prior to anaesthesia. In addition, an unstable diabetic may suffer hyperglycaemia or hypoglycaemia which may be more difficult to detect and treat during anaesthesia.
    Pre-operative soluble insulin or intravenous dextrose solutions may be necessary.
18. Why might anaemia prove to be a problem in an anaesthetised patient?
    Low haemoglobin levels may mean that oxygen flux is inadequate once compensatory changes are depressed. Treatment of the underlying cause or a blood transfusion may be necessary.
19. Why are polycythaemic patients high risk?
    Polycythaemia is an abnormal increase in the number of erythrocytes in the blood. This makes the blood hyperviscous and can cause it to sludge in the capillaries thus reducing the efficiency of the cardiovascular system. It may be indicative of dehydration or cardio-pulmonary disease.
20. Why do pyrexic animals require particular care during anaesthesia?
    Pyrexia increases the patient's metabolic rate and therefore oxygen and glucose consumption are raised. Carbon dioxide production is considerably greater and thus it must be ensured that the animal is sufficiently oxygenated and that adequate means for carbon dioxide removal are employed.
    Maintenance of anaesthesia by gas inhalation via a mask or closed circuit would not be suitable; a semi-closed circuit reliant upon high fresh gas flow rates would provide the best option since expired carbon dioxide is flushed from the circuit so that it cannot be rebreathed at the next breath.
21. List 6 drug categories that may produce undesirable side-effects following interaction with anaesthetic drugs.
    • Corticosteriods = steroids depress adrenal cortical function and produce signs of atrophy; the adrenal cortex may not be able to secrete sufficient steroid to meet the requirements associated with the stress of anaesthesia and surgery.
    • Antibiotics = some antibiotics can contribute to respiratory insufficiency under general anaesthesia.
    • Digitalis = Can cause intra-operative arrhythmias; it is recommended that drugs from this group (e.g. Digoxin) are discontinued one to two days prior to anasethesia.
    • Endocrine supplements = Insulin and thyoxine are examples of this drug group whose effects upon metabolism may affect general anaesthesia.
    • Beta blockers = Drugs such as Propranolol may interact with anaesthetic drugs blocking the pressor responses of hypercapnia.
    • Pre-medicant drugs = Some breeds may have a profound response to some drugs, e.g. Boxers to phenothiazine (ACP).
      Other drugs to note are: non-steroidal antiinflammatories, organophosphorous compounds, anticonvulsants, diuretics, ACE inhibitors, antihistamines, antitissusives, bronchodilators and sex hormones.
22. Why should a patient be starved pre-operatively, and under what circumstances might the usual recommendations be adjusted?
    Pre-operative starvation is advisable in order to prevent a full stomach from pressing upon the diaphragm and thus restricting respiratory movement and to prevent vomiting during induction or recovery from anaesthesia. Food is generally withheld 6-8 hrs prior to anaesthesia although some veterinary surgeons recommend a period of up to 12 hours. Water should be available up to 30 minutes prior to surgery. If the animal is polydipsic, polyuric or known to have renal disease; water intake must not be restricted. A diabetic patient must always have food immediately after insulin administration. In addition, very hot weather may necessitate additional water requirements.
23. If an animal has eaten a large meal pre-operatively, what could be done to reduce the risks associated with anaesthesia and a full stomach?
    Vomiting may be induced with morphine, although it is generally considered safer to postpone surgery if possible. The procedure may be delayed until the end of the surgical list or rescheduled for another day. If the owner of the patient has particular difficulty starving their animal; e.g. multi-pet households or known scavengers, it may be wise to hospitalise the patient overnight prior to surgery.
24. Hypovolaemia and dehydration are serious risk factors to anasethesia; explain their significance.
    Hypovolaemia, and indeed all types of shock may result in a sudden fall in blood pressure leading to lack of oxygen in the tissues. This in itself is detrimental during anaesthesia. In addition, the capillary walls possess greater permeability resulting in loss of fluid. Chronic fluid losses may cause electrolyte and pH imbalances further increasing the risks. Ideally, a shocked or dehydrated animal should be stabilised prior to anaesthesia.
25. Define polydipsia and polyuria and explain their significance in an animal due to be anaesthetised.
    Polydipsia (increased thirst), and polyuria (increased micturition) may indicate renal pathology. Water should not be restricted in such cases and parenteral fluids may be required since the patient may be unable to concentrate its urine. Urine specific gravity and blood urea and creatinine levels should be monitored in order to assess the severity of the problem prior to anaesthesia.
26. Finally, list 10 signs of shock.
    • This is a commonly asked question in the oral examination, and is included here due to its significance in anaesthesia.
    • Pale, dry mucous membranes
    • Slow capillary refill time (normally less than 2 seconds.
    • Tachycardia
    • Tachypnoea.
    • Rapid, feeble pulse.
    • Cold extremities
    • Depressed demeanour.
    • Skin tenting and sunken eyes if dehydration present.
    • Shivering.
    • Convulsions if the brain becomes hypoxic as a result of severe haemorrhage.