Anaesthesia for sicker patients

Question 1

ASA category II

Answer 1

Mild systemic disease, well-compensated.

Question 2

ASA category III

Answer 2

Severe systemic disease for which the animal cannot fully compensate.

Question 3

ASA category IV

Answer 3

Severe systemic disease for which the animal poorly compensates.

Question 4

ASA V

Answer 4

A moribund animal not expected to survive without the procedure. Without intervention, expected to die in next 24 hrs.

Question 5

How could you stabilise a patient with cardiovascular disease prior to anaesthetising?

Answer 5

• If possible, drain the ascites/pleural effusion
• Start the patient on meds e.g. pimobendan, frusemide
• Pre-oxygenate the patient

Question 6

How might congestive heart failure affect time taken for the anaesthetic to have an effect?

Answer 6

• Congestive heart failure → may have poor peripheral perfusion
• → Longer time taken for drugs to take effect when given IM/IV

Question 7

In a patient with reduced cardiac output, what might you have to be careful of regarding inhalational anaesthetics?

Answer 7

Reduced cardiac output → faster increase in plasma concentration of anaesthetic

Take care the patient does not become too deep!

Question 8

Why might drug effects be less predictable in a patient with cardiovascular disease?

Answer 8

• With large effusions, volume of distribution is altered
• This means water soluble drugs are more likely to leave blood plasma quickly and enter fluid-filled spaces

Question 9

How might severe effusion in a patient with heart failure affect albumin levels?

What might this mean for drug doses?

Answer 9

• Severe effusion → low albumin
• Therefore more unbound, active drug
• May need to use lower doses

Question 10

How might cardiovascular disease affect hepatic drug metabolism? What might we thus need to consider?

Answer 10

• Cardiovascular disease → potentially reduced blood flow to liver
• More time taken for the same amount of drug to be metabolised
• Longer duration of action
• Consider dosing intervals carefully

Question 11

Why is it important to reduce the volume of volatile agent (where pos) in a patient with cardiovascular disease?

How can we achieve this?

Answer 11

• Inhalational agents depress myocardial function
• In an already compromised patient, need to preserve this as much as possible
• Use balanced anaesthesia to minimise volatile agent needed

Question 12

Why is it important to reduce the volume of volatile agent (where pos) in a patient with cardiovascular disease?

How can we achieve this?

Answer 12

• Inhalational agents depress myocardial function
• In an already compromised patient, need to preserve this as much as possible
• Use balanced anaesthesia to minimise volatile agent needed

Question 13

When should you give alpha-2 agonists or ACP to a patient with cardiovascular disease?

Answer 13

Only for patients which are relatively well compensated.

Question 14

What would be a possible drug protocol for a patient with severe cardiovascular disease?

Answer 14

• Midazolam + opioid

OR

• Alfaxalone + opioid (provides good cardiovascular stability)

Question 15

True/false: a patient with cardiovascular disease should be pre-oxygenated and intubated quickly.

Answer 15

True

• Need to maintain oxygen delivery as far as possible; perfusion is likely to be poor in these patients

Question 16

True/false: you should always give patients with cardiovascular disease fluid therapy.

Answer 16

False

• Be careful with fluid therapy - don’t want to create more work for the struggling heart!
• Give no fluids/a small amount and monitor carefully for signs of fluid overload

Question 17

Why is it important to provide adequate analgesia to patients with cardiovascular disease?

Answer 17

• These patients are especially vulnerable to stress
• Nociception under anaesthesia can cause catecholamine release
• Catecholamine release can worsen hypercapnia