ANAESTHESIA - Anaesthetic Risk and Pre-Anaesthetic Assessment

Question 1

What is the ASA grading scale?

Answer 1

The ASA grading scale is a tool that vets use to assess a patient’s health status and assess the the risks associated with anaesthesia. This helps vets tailor anaesthetic protocols accordingly for each patient

Question 2

Describe a patient with an ASA score of one

Answer 2

Healthy patient

Question 3

Describe a patient with an ASA score of two

Answer 3

Patient with mild, fully compensated systemic disease

e.g. controlled diabetes, mild heart disease

Question 4

Describe a patient with an ASA score of three

Answer 4

Patient with severe systemic disease functionally affecting the patient

e.g. uncontrolled diabetes, anaemia

Question 5

Describe a patient with an ASA score of four

Answer 5

Patient with severe systemic disease which is a constant threat to life

e.g. shock, uncontrolled heart failure

Question 6

Describe a patient with an ASA score of five

Answer 6

Patient is moribund, not expected to live for more than 24 hours without and possibly even with treatment

e.g. shock, severe trauma

Question 7

What is meant by the addition of the letter ‘E’ to an ASA score?

Answer 7

The addition of an ‘E’ indicates this is an emergency case

Question 8

(T/F) Most anaesthetic related deaths occur post-operatively

Answer 8

TRUE.

Question 9

According to mortality studies, what is the primary cause of anaesthetic related death in small animals?

Answer 9

Cardiorespiratory failure

Question 10

According to mortality studies, what is the primary cause of anaesthetic related death in equids?

Answer 10

Post-anaesthetic injuries (such as fractures and myopathies)

Question 11

According to veterinary evidence, identify ten risk factors that can increase anaesthetic risk

Answer 11

Patient ASA grade
Procedural urgency
Major procedures
Duration of procedure
Patient signalement (age, breed, body weight/conditon)
Concurrent disease
Fluid therapy in cats
Endotracheal intubation in cats
Mask inductions
Level of monitoring and degree of intervention by anaesthetist

Question 12

How can fluid therapy increase anaesthetic risk in cats?

Answer 12

Excessively high volume fluid rates in cats increases the risk of volume overload

Question 13

How can endotracheal intubation increase anaesthetic risk in cats?

Answer 13

There are more complications associated with endotracheal intubation in cats such as laryngeal spasm due to mechanical manipulation of the larynx, tracheal collapse and pressure necrosis due to overinflation of the cuff

Question 14

How can mask induction increase anaesthetic risk?

Answer 14

Mask induction is often unpleasant and stressful for the patient which triggers the sympathetic nervous system resulting in catecholamine release which results in tachycardia. Severe tachycardia can result in decreased cardiac output as the heart does not have time to refill with blood - which can contribute to increased anaesthetic risk

Question 15

What is the aim of a pre-anaesthetic assessment?

Answer 15

A pre-anaesthetic assessment aims to identify any disorders which may increase anaesthetic risk

Question 16

What should you carry out during a pre-anaesthetic assessment?

Answer 16

Take a thorough history
Clinical exam

Question 17

Which three main factors should you consider when determining anaesthetic risk?

Answer 17

Patient signalement (age, breed, body condition/weight)
Disease processes affecting the patient
Type of procedure taking place

Question 18

Why do geriatric patients have a higher anaesthetic risk?

Answer 18

Geriatric patients have reduced physiological reserves, may have concurrent disease and are more prone to hypothermia

Question 19

Why do paediatric patients (animals less than 12 weeks old) have a higher anaesthetic risk?

Answer 19

Paediatric patients are still physiologically immature and are more prone to hypothermia

Question 20

Why do brachycephalic breeds have a higher anaesthetic risk?

Answer 20

Brachycephalic breeds have small collapsible airways that are prone to obstruction and severe respiratory impairment

Question 21

Why do greyhounds have a higher anaesthetic risk?

Answer 21

Greyhounds have a very low body fat percentage which can lead to the faster absorption and elimination of anaesthetic drugs as well as affect drug distribution. Some drugs also have a longer duration of action in Greyhounds due to impaired drug metabolism by the liver

Question 22

Why do some herding dog breeds have an increased anaesthetic risk?

Answer 22

Herding dog breeds often have a genetic mutation in the ABCB1 gene that allows certain drugs to cross the blood brain barrier (BBB) and accumulate in the brain

Question 23

How can obesity increase anaesthetic risk?

Answer 23

Obesity increases the pressure on the cardiorespiratory system, the excess fat can affect drug distribution and duration of action and wound healing is impaired in obese animals

Question 24

Which eight questions should you consider before putting your patient under anaesthesia?

Answer 24

1. Has anything significant been identified in the history and/or clinical exam?
2. Do any abnormalities warrant further investigation?
3. Can any abnormalities be stabilised prior to anaesthesia?
4. What complications are anticipated during anaesthesia?
5. How can these complications be managed?
6. Would the patient benefit from pre-medication?
7. How will any pain associated with the procedure be managed?
8. How will anaesthesia be induced and maintained?

Question 25

When are pre-op blood tests most useful?

Answer 25

Pre-op blood tests are most useful in geriatric patients to check for and monitor any disease trends

Question 26

When are pre-op blood tests unnecessary?

Answer 26

Evidence suggests that in patients below the age of seven with an ASA score of one, pre-op bloods are unnecessary

Question 27

Other than the patient themselves, which five factors can also influence patient safety while under anaesthesia?

Answer 27

Organisation
Technology available
Medications and delivery systems available
The veterinary team
The individual monitoring the anaesthetic