Pre-medications and sedatives

Question 1

What are the ideal drug properties?

Answer 1

• Produce reliable sedation and anxiolysis
• Minimal effects on the CV and Resp system
• Provision of analgesia
• Reversibility

Question 2

Why do we premedicate?

Answer 2

• Provide anxiolysis
• Facilitate animal handling
• Contributes to a balanced anaesthesia and smooth and quiet recovery
• Counter algesia and side effects of other drugs

Question 3

What are the drugs used as pre-medication?

Answer 3

• Phenothalzines
• Alpha- 2 agonists
• Benzodiazepines
• Alfaxalone
• Anticholinergics
• Opioids

Question 4

What is an example of a phenothalzine?

Answer 4

• Acepromazine

Question 5

What are some examples of alpha-2 agonists?

Answer 5

• Dexmedetomidine
• Medetomidine
• Xylazine

Question 6

What are some examples of benzodiazepines?

Answer 6

• Diazepam
• Midazolam

Question 7

What are some examples of anticholinergics?

Answer 7

• Atropine
• Glycopyrronium

Question 8

What are some examples of opioids?

Answer 8

• Morphine
• Methadone
• Pethidine
• Hydromorphone
• Oxymorphone
• Buprenorphine
• Fentanyl
• Butorphanol

Question 9

How do phenothiazines work?

Answer 9

• Inhibits dopamine pathways, so calms patient this way
• Anti-emetic
• Reduces total anaesthetic dose by a third and protects against arrhythmias
• Has a sedation plateau
• Long duration of action (6 hours)

Question 10

Why should phenothiazines be avoided in liver disease?

Answer 10

• Drug is metabolised by the liver

Question 11

What does neuroleptanalgesia mean?

Answer 11

• Combination of an phenothiazine with an opioid

Question 11

What are the effects of phenothiazines on the cardiovascular system?

Answer 11

• Inhibits alpha-1 adrenoreceptors, which leads to peripheral vasodilation and a reduction in arterial blood pressure
• Sequesters RBC to the spleen reducing HCT by 20%

Question 12

What patients should be avoided when using phenothiazines?

Answer 12

• Liver disease
• Shock
• Cardiovascular disease
• Anaemic
• Having a splenectomy
• Epilepsy

Question 13

What are the effects of phenothiazines on the respiratory system?

Answer 13

• Neuroleptanalgesia overdoses can lead to respiratory depression

Question 14

What are the effects of phenothiazines on the body temperature?

Answer 14

• Associated with a decrease in body temperature due to resetting the thermoregulatory mechanism and peripheral vasodilation

Question 15

What are the effects of phenothiazines on the gastrointestinal system?

Answer 15

• Lowers the oesophageal sphincter and increases the risk of gastro-oesophageal reflux

Question 16

How do alpha-2 agonists work?

Answer 16

• Stimulate alpha-2 receptors found centrally and peripherally
• Reduces total anaesthetic dose of isoflurane by 70%
• Muscle relaxant
• When combined with opioids or benzodiazepines the sedative effect is synergistic and greater alowing reduced doses of A-2-A

Question 17

What are the effects of alpha-2 agonists on the cardiovascular system?

Answer 17

• Biphasic dose dependent on blood pressure; two phases
• Phase 1: vasoconstriction leading to increased BP leasing to a reduction in HR
• Phase 2: BP returns to normal, but HR remains low, which can lead to issues with cardiac output and blood pressure
• Heart rhythm can lead to ventricular premature complexes or bradycardia abnormalities

Question 18

What are the effects of alpha-2 agonists on the body temperature?

Answer 18

• Causes vasoconstriction, which minimises the heat loss

Question 19

What are the effects of alpha-2 agonists on the neurological system?

Answer 19

• Lowers cerebral blood flow, which reduces intracranial pressure

Question 20

What are the effects of alpha-2 agonists on the gastro-intestinal tract?

Answer 20

• Vomiting is frequently seen, so care with oesophageal obstructions, intraocular pressure, intracranial pressure and cervical disk disease

Question 21

What is the reversal agent for alpha-2 agonists?

Answer 21

• Use of atipamezole and alpha-2 antagonist

Question 22

Why alpha-2 agonist’s reversal agent administered IM and not IV?

Answer 22

• IV can cause excitability, tachycardia and very rapid recovery

Question 23

How do benzodiazepines work?

Answer 23

• Depress the sub-corticol levels of the CNS working on GABA receptors
• Anxiolytic
• Muscle relaxant
• Anticonvulsant
• Stimulates appetite
• Reduces total anaesthetic dose
• Used in combination with opioid for pre-meds and sick or compromised patients
• Minimal effects on CV and respiratory system

Question 24

What are the problems using benzodiazepines?

Answer 24

• Excitability
• Irritant
• Reacts with plastic syringes

Question 25

What is the reversal agent for benzodiazepines?

Answer 25

• Use of Flumazenil, which blocks the use of bendiazepines

Question 26

What are the differences between midazolam and diazepam?

Answer 26

• Midazolam is water soluble whereas diazepam is not
• Midazolam is metabolised by the liver into inactive metabolites, so shorter acting and less risk of accumulation whereas diazepam metabolised into active metabolites, so prolonged action when repeated and risk of accumulation

Question 27

How do anticholinergics work?

Answer 27

• Blocks the parasympathetic nervous system
• Prevents bradycardia
• Reduces respiratory secretions and salivation

Question 28

What are the problems using anticholinergics?

Answer 28

• Tachycardia
• Pupillary dilation
• Dry mouth

Question 29

When are anticholinergics used?

Answer 29

• Used in brachycephalic breeds
• Enucleations involving traction on the eyeball
• Possibly laryngeal surgery

Question 30

What are the differences between atropine and glycopyrrium?

Answer 30

• Atropine is able to cross the BBB whereas glycopyrriumn has limited diffusion across this
• Atropine causes dilated pupils, whereas glycopyrrium has no effect on pupils