Monitoring Periods & Planes Of Anaesthesia - Answers

Arlo Guthrie — Tue, 21 Apr 2009 11:39:44 GMT

Current Revision posted to Revision Guide For Student Nurses - Part 2 by Arlo Guthrie on 4/21/2009 11:39:44 AM

ANSWERS

How frequently should an anaesthetised animal be checked?
At least every 5 minutes (the results should be recorded on an anaesthetic chart).
What instrument is used to find out the tidal volume of a patient?
Wright's resprometer.
List instruments useful in the monitoring of the anaesthetised animal.
- Stethoscope (ideally an oesophageal stethoscope).
- Thermometer.
- Pulse-oximeter.
- ECG machine.
- Blood pressure monitor.
- Respiratory monitor.
- CVP (central venous pressure) manometer.
- Blood-gas analysis equipment (to monitor C02 levels).
Under general anaesthesia, the respiratory rate should be similar to the resting rate in a conscious animal. What might cause a reduced respiratory rate under anaesthesia?
- Increasing depth of anaesthesia.
- Induction by barbiturates.
Why is it essential to ensure that cardiac output is maintained during anaesthesia?
In order to provide adequate perfusion of tissues and vital organs including the brain, heart and kidneys.
When monitoring pulse rate and depth, why is it advisable to palpate a peripheral pulse (such as the labial or sublingual) rather than a central pulse (such as the femoral)?
Peripheral pulses are more sensitive to changes in the circulation and thus abnormalities will be detected more promptly.
Blood pressure measurement provides a clear indication of the peripheral circulation. Describe 2 methods of monitoring blood pressure.
- Directly - by arterial cannulation connected to a pressure transducer.
- Indirectly - using an occlusive cuff and Doppler detector or machine.
What might pale mucous membranes be indicative of?
- Hypotension.
- Hypovolaemia.
What might cyanotic (blue) mucous membranes be indicative of?
Hypoxia (inadequate oxygenation).
List 4 conditions that may be indicated by an increased capillary refill time.
- Hypotension.
- Hypovolaemia.
- Toxaemia.
- Haemorrhage.
Why is the measurement of urine output useful in the monitoring of an anaesthetised patient?
A urine output in excess of 1ml/kg/hr represents adequate renal perfusion and therefore is an indicator of vital organ performance. Catheterisation of the urinary bladder is performed and collected urine weighed (1ml of urine = 1g).
How are reflexes used to assess the depth of anaesthesia?
As the level of anaesthesia deepens, muscle tone is lost.
List reflexes commonly used to assist in the assessment of the level of unconsciousness.
- Jaw tone.
- Pedal withdrawal reflex.
- Palpebral reflex (blinking).
A patient is under anaesthesia; the pupils are dilated and the eyes are in a normal position. What is this indicative of?
Very deep anaesthesia.
Describe the position of the eye under moderately deep anaesthesia.
The eye rotates downwards and medially.
Why do patients become hypothermic during anaesthesia?
Anaesthesia depresses the hypothalamus which in turn depresses temperature regulation.
List the 5 categories of the anaesthetic period.
- Pre-operative/preparation period.
- Pre-anaesthetic/pre-medication period.
- Induction.
- Maintenance.
- Recovery.
List methods in which the correct body temperature may be maintained during anaesthesia.
- Warm ambient environment.
- Environment free from draughts.
- The use of heat pads.
- Careful surgical preparation of the patient including the avoidance of creating overlarge clipped areas and the use of cold wet drapes.
- Provision of blankets during recovery.
List actions taken during the pre-operative/preparation period.
- Thorough clinical examination of the conscious patient.
- Administration of drugs to control pre-existing conditions if necessary.
- Checking of equipment prior to use.
The pre-anaesthetic/pre-medication period involves the administration of premedicant drugs. List common reasons for the use of pre-meds (see Module 3).
- Sedation - in order to relax the patient (particularly during induction) which may prove traumatic).
- Analgesia - to provide pain relief.
- Anaesthetic sparing effect.
- Reduction of undesirable side effects of anaesthesia such as salivation and vomiting.
List the 4 stages of anaesthesia.
- Voluntary excitement.
- Involuntary excitement.
- Surgical anaesthesia (of which there are 3 planes).
- Overdosage.
Briefly describe the stage of voluntary excitement.
- INDUCTION UNTIL UNCONSCIOUSNESS PRESENT.
- Apprehension and resistance - generalised sympatho-adrenal response to threat.
- Disorientation.
- Pulse and respiratory rate increased.
- Pupil dilated.
- Skeletal muscle activity.
- Hyper-reflexia.
- Possible breath holding, vocalisation, salivation, urination, defecation.
Briefly describe the stage of involuntary excitement.
- ONSET OF UNCONSCIOUSNESS TO RHYTHMIC BREATHING.
- Cranial nerve reflexes present - possibly hyperactive.
- Eyes initially wide open and pupils dilated, later rotate to ventromedial position.
- Brisk response to pedal reflex.
- Irregular breathing and gasping becomes regular.
Describe the planes of surgical anaesthesia.
- Regular, deep respiration with minute volume proportional to surgical stimulation. Light anaesthesia of a depth only suitable for superficial surgery.
- Muscle relaxation more apparent. Suitable depth for most surgery.
- Intercostal lag between inspiration and expiration. Deep anaesthesia suitable for all procedures.
Describe signs of anaesthetic overdose.
- Progressive respiratory failure eventually resulting in the cessation of diaphragmatic function.
- Very rapid or very slow pulse rate which becomes impalpable.
- Eyes open in central position with maximally dilated pupils and dry corneas.
- Mucous membranes cyanotic, finally turning grey.
- Prolonged CRT.
- Accessory respiratory activity representing agonal gasping ( indicated by throat twitching).
Why should excess levels of anaesthesia be avoided?
- Recovery is prolonged.
- Causes unnecessary cardio-pulmonary depression.
- Limits organ perfusion which may result in post-operative organ failure.
- May cause cardiac arrest.
Why is it essential to maintain an adequate depth of anaesthesia?
- To prevent the animal from waking up during a surgical procedure.
- Movement of the patient may compromise surgery.
- The animal may extubate itself or bite through the endotracheal tube.
- Arrythmias and cardiac arrest may result from catecholamine release.
- The uptake of anaesthesia may be impaired by tachypnoea.