Pre-medication

Question 1

Name the 5 groups of premedication

Answer 1

Phenothiazine, Alpha-2-agonists, Benzodiazepines, Opioid Analgesics, Anti-muscarinics

Question 2

Name a Phenothiazine

Answer 2

Acepromazine (ACP)

Question 3

What patients are sensitive or resistant to ACP?

Answer 3

Large dogs are sensitive to ACP; Small dogs and Cats are resistant to ACP

Question 4

Describe the properties of phenothiazines?

Answer 4

Dopamine receptor antagonist

Sedative/tranquiliser, but has NO analgesia

Question 5

What are the advantages of Phenothiazines?

Answer 5

Anti-histamine
Anti-emetic
Anti-arrhythmic
Smooth muscle spasmolytic

Question 6

What are the disadvantages of phenothiazines?

Answer 6

Predisposes hypothermia
Hypotension
Peripheral vasodilation 
Decreased seizure threshold 
Slow onset (30-40minutes)
Long duration

Question 7

What are the properties of Alpha-2-agonists?

Answer 7

Bind to alpha 2 receptors in the brain
Provide sedation AND analgesia
For healthy animals

Question 8

Giver 2 examples of alpha 2 agonists

Answer 8

Medetomidine and Dexmedetomidine

Question 9

What are the advantages of alpha 2 agonist?

Answer 9

Provides analgesia 
Drug sparing effect
Muscle relaxation 
Reversible - using alpha 2 antagonist Atipamezole
Dose-dependant sedation

Question 10

What are the disadvantages of alpha 2 agonists?

Answer 10

Hypertension
Vasoconstriction 
Vomiting 
Impaired Thermoregulation 
CVS depression ( lowers CO and HR)
Respiratory Depression (can lead to apnoea)

Question 11

What are the properties of Benzodiazepines?

Answer 11

Binds to, and enhances GABBA neurotransmitter receptors in CNS.
It is a tranquiliser (reduces anxiety) but not really a sedative (which reduces consciousness)

Question 12

Give 2 examples of Benzodiazepines

Answer 12

Midazolam and Diazepam

Question 13

What are the advantages of benzodiazepines?

Answer 13

Reduces anxiety
Its safe (i.e. has a high therapeutic index)
Muscle relaxant
Minimal cardiopulmonary effects (safe for very sick patients)
Prolong and enhance effects of other anaesthetics
Anti-epileptic (diazepam)

Question 14

What are the disadvantages of benzodiazepines?

Answer 14

Causes excitement in healthy animals (when used alone)
Risk of liver necrosis
Unpredictable
Diazepam is painful IM

Question 15

What are the properties of opioid analgesics?

Answer 15

Binds to mu receptors in the brain

Can be reversed with Naloxone

Question 16

Give 2 examples of Opioid Analgesics? What type of agonist are they and what are they used for?

Answer 16

Buprenorphine - partial agonist - for mild to mod pain

Methadone - full agonist - for mod to severe pain

Question 17

What are the advantages of using opioid analgesics as pre-meds?

Answer 17

Can provide sedation in non-painful or very sick animals
Reduces the dose of induction drug required
Dose-dependant analgesia
CO remains good

Question 18

What are the disadvantages of using opioid analgesics as pre-meds?

Answer 18

Excitation in overdose
If overdose, can cause profound respiratory depression 
GI effects (e.g. vomiting)
Urinary retention 
Anti-tussive effect

Question 19

What are the properties of Anti-muscarinics?

Answer 19

Parasympathetic antagonist
Inhibit acetylcholine receptors
They increase HR - used in surgeries where there is pushing/pulling on things can trigger vagal reflex (which would decrease HR)

Question 20

Give examples of an Anti-muscarinic?

Answer 20

Atropine

Glycopyrrolate

Question 21

What are the advantages of Anti-muscarinics?

Answer 21

Controls intra-operative bradycardia
Reduces salivation and bronchial secretions (therefore reduces the risk of aspiration pneumonia)
Protects against bradycardia during reversal of NMBA

Question 22

What are the disadvantages of Anti-muscarinics?

Answer 22

Cause arrhythmias
Cause diminished GI activity
Pupil dilation leading to visual disturbance
Thickens bronchial secretions
Increases HR, Increases metabolic rate, Increases myocardial O2 consumptions