DM1 Pt2-3 Pharmacology of Premedication Drugs

Question 1

Does acepromazine provide analgesia?

Answer 1

Acepromazine provides sedation but is not generally considered to provide analgesia, although some data suggest it may in cats.

Question 2

What are the cardiovascular effects of acepromazine?

Answer 2

Acepromazine causes vasodilation, which can lead to hypotension, especially in cats with cardiovascular disease or hypotension.

Question 3

Why is acepromazine usually avoided in ASA 4 and 5 cats?

Answer 3

Due to its vasodilatory effects, it can cause marked hypotension in severely compromised cats.

Question 4

What are the key effects of alpha 2 agonists like dexmedetomidine?

Answer 4

Alpha 2 agonists provide dose-dependent sedation and analgesia but have profound cardiovascular effects like reduced heart rate and cardiac output.

Question 5

How does dexmedetomidine affect blood pressure?

Answer 5

It causes an initial increase in blood pressure due to vasoconstriction, followed by a return to normal levels after 20-30 minutes.

Question 6

What is the main advantage of dexmedetomidine over medetomidine?

Answer 6

Dexmedetomidine is more specific for the alpha 2 receptor and does not require levomedetomidine, potentially reducing biological load.

Question 7

How does dexmedetomidine reduce the need for other anaesthetic drugs?

Answer 7

It significantly reduces the dose of induction and maintenance agents like propofol, lowering drug concentrations by up to 50%.

Question 8

What is the benefit of using atipamezole with dexmedetomidine?

Answer 8

Atipamezole reverses the effects of dexmedetomidine, reducing recovery time, but also reverses its analgesic effects, requiring other analgesics.

Question 9

Why must anaesthetic agents be administered slowly after dexmedetomidine?

Answer 9

Dexmedetomidine slows blood-brain circulation, increasing the time to peak effect and raising the risk of anaesthetic overdose if not administered carefully.

Question 10

Why should dexmedetomidine be avoided in cats with cardiovascular disease?

Answer 10

It reduces cardiac output, and cats with cardiovascular disease have reduced cardiac reserve, leading to poor organ perfusion and arrhythmias.

Question 11

Why is dexmedetomidine not recommended for geriatric cats?

Answer 11

Geriatric cats have reduced cardiovascular reserve, making them more vulnerable to the effects of dexmedetomidine on cardiac output.

Question 12

Why should dexmedetomidine be avoided in cats with liver disease?

Answer 12

It decreases liver blood flow, which can further compromise liver function.

Question 13

In which cats is vomiting after dexmedetomidine undesirable?

Answer 13

Cats with raised intraocular or intracranial pressure, or those with a gastrointestinal foreign body, should avoid dexmedetomidine due to its emetic effect.

Question 14

Why should dexmedetomidine be avoided in cats with severe systemic disease (ASA 3 or higher)?

Answer 14

Cats with severe systemic disease have reduced compensatory mechanisms to maintain cardiac output under the effects of dexmedetomidine.

Question 15

What are the differences between diazepam and midazolam?

Answer 15

Diazepam can cause thrombophlebitis, has active metabolites, and longer duration, while midazolam is water-soluble, shorter-acting, and less painful to inject.

Question 16

Why are benzodiazepines combined with ketamine for sedation in cats?

Answer 16

Benzodiazepines alone can cause excitation in healthy adult cats, but when combined with ketamine, they produce reliable sedation.

Question 17

Why is ketamine always co-administered with another sedative?

Answer 17

Ketamine can cause central nervous system excitation when administered alone, so it’s combined with sedatives like dexmedetomidine or midazolam.

Question 18

How does ketamine affect the cardiovascular system?

Answer 18

Ketamine is generally cardiovascularly stable, mildly stimulating the sympathetic nervous system, but it can cause myocardial depression in sick cats.

Question 19

In which cats should ketamine be avoided?

Answer 19

Ketamine should be avoided in cats with hypertrophic cardiomyopathy, as it can increase heart rate and exacerbate myocardial oxygen imbalance.

Question 20

What is alfaxalone used for in premedication?

Answer 20

Alfaxalone is used in anxious cats needing heavy sedation, especially when ketamine or dexmedetomidine is unsuitable, but it causes short-duration cardiovascular and respiratory depression.

Question 21

Why should buprenorphine not be administered subcutaneously in cats?

Answer 21

Absorption from the subcutaneous route is slow, reducing its analgesic efficacy.

Question 22

Which opioid is recommended for more invasive procedures in cats?

Answer 22

Methadone, a full µ opioid agonist, is recommended for more invasive procedures like limb amputation or exploratory laparotomy.

Question 23

Why is pethidine not ideal for premedication in cats?

Answer 23

Pethidine is short-acting (90 minutes), requires large volumes for IM injection, and cannot be given IV due to histamine release.

Question 24

Why is fentanyl unsuitable for premedication in most cats?

Answer 24

Fentanyl is very short-acting (20 minutes after IV administration), but can be combined with midazolam for haemodynamic stability in ASA 4 or 5 cats.