Clinical sedation + premedication

Question 1

When would you premedicate?

Answer 1

Prior to anaesthesia

Question 2

Why sedate?

Answer 2

• Relieve patient anxiety
• Facilitate handling of patient
• Provide analgesia
• Provide muscle relaxation
• To enable procedures or interventions to be carried out

Question 3

Why premedicate?

Answer 3

• Smooth the induction of general anaesthesia
• Smooth maintenance phase of general anaesthesia
• Smooth recovery from general anaesthesia
• Reduce required dose of induction/ maintenance agent
• Anaesthetic (MAC) sparing effect
• Not always necessary (particularly in small animals)

Question 4

What qualities would the perfect premed/sedative have?

Answer 4

• Relieve fear and anxiety
• Safe, reliable and predictable effect
• Quick onset, appropriate duration of action
• Easy to administer (route, volume, non-irritating)
• Minimal cardiovascular, respiratory and other side effects
• Provide analgesia
• Can be antagonised

Question 5

With nervous patients what could you give them - pre-appointment?
horses?
Cats + dogs?

Answer 5

• Equine
  
  • acepromazine oral gel, detomodine
    oromucosal gel
• Dogs and cats
  
  • Gabapentin: 2 hours before appointment
  • Trazadone

Question 6

What are the different opioids you could use?

Answer 6

• Butorphanol - kappa
• Buprenorphine - partial Mu
• Methadone
• Fentanyl
• (morphine) - not licenced

Question 7

Other drug options - categories and drugs within categories?

Answer 7

• Phenothiazines
  * Acepromazine
• Alpha 2 receptor agonists
  * Xylazine, detomidine, romifidine,
  medetomidine, dexmedetomidine
• Benzodiazepines
  * Diazepam, midazolam
• Adjuncts
  * Propofol, alfaxalone, ketamine

Question 8

What are the pros/cons of opioids?

Answer 8

• May be adequate alone (mild sedation)
• Often good sedation if the animal presents
  very painful or critically ill
• Respiratory depression (methadone,
  morphine, fentanyl)

Question 9

Pros/cons of acepromazine?

Answer 9

• Useful for
  * mitral valve disease cases
  * Patients with brachycephalic
  obstructive airway syndrome
  * laryngeal paralysis/ upper respiratory
  tract disease
  * In combination with alpha-2 agonist for
  background calming effect
  * ↓ anaesthetic mortality in horses
• Side effects: ↓contractility → Hypotension
• Onset: 20-40 minutes
• Mild to moderate sedation

Question 10

Cons of acepromazine?

Answer 10

• No analgesia
• No antagonist available
• Long duration of action (4-6 hours)
• Moderate anaesthetic sparing effect (around 40%)
• Not suitable for
  * very young (<3 months)
  * hepatic impairment
  * haemorrhage (actual or anticipated)
  * anticipated hypotension during general
  anaesthesia
  * sepsis

Question 11

Pros of Alpha-2-agonists?

Answer 11

• Useful for
  * Almost all adult horses
  * Almost all farm animals
  * Most (but not all) dogs and cats
• Onset: depends on route of administration (IV almost immediate)
• Very reliable sedation (moderate to profound) and some analgesia
• Analgesia
• Specific antagonist: Atipamezole (licensed in dog and cats)
• Large anaesthetic sparing effect (up to 90%)

Question 12

Cons of Alpha-2-agonists?

Answer 12

• Side effects
  * peripheral vasoconstriction then reflex
  bradycardia
  * Increased urine production
• Not suitable
  * Advanced mitral valve disease
  * very young (<3 months)
  * resulting bradycardia may be a problem
  * urinary obstruction

Question 13

Pros of benzodiazepines?

Answer 13

• Useful for
  * very young
  * very old
  * very sick
• Minimal Side effects
• Antagonist: flumazenil

Question 14

Cons of benzodiazepines?

Answer 14

• Unreliable sedation (paradoxical excitation)
• No analgesia
• Moderate MAC sparing effect
• Not suitable
  * farm animals (not licensed)

Question 15

Opioids administration?

Answer 15

• intravenous - rapid onset
• intramuscular
• subcutaneous - less reliable
• transcutaneous (fentanyl)

Question 16

Acepromazine administration?

Answer 16

• intravenous - smaller dose needed
• intramuscular - detomidine only
• subcutaneous
• oral (gel: horses, tablets: dogs, cats) - less reliable

Question 17

Alpha-2-agonist administration?

Answer 17

• intravenous - faster onset + smaller dose
• intramuscular
• subcutaneous - less reliable
• transmucosal

Question 18

Benzodiazepines administration?

Answer 18

• intravenous - faster onset + smaller dose -
  can cause paradoxical effect
• intramuscular (midazolam) - less reliable
• oral (diazepam, not cats)
• rectal

Question 19

What must a drug have for food producing animals?

Answer 19

• Specified withdrawal period
• Maximum residue limit

Question 20

What sedatives can be used for food producing animals?

Answer 20

-butorphanol
-xylazine
-detomidine
-(azaperone for pigs)

Question 21

Why do we need to be careful administering xylazine to ruminants?

Answer 21

Very sensitive to the drug
give 1/10 the dose you would give a horse

Question 22

What is a reliable sedative in adult horses?

Answer 22

• Alpha-2 agonists reliable sedation of adult horses

Question 23

With horses what would you administer first and what after?

Answer 23

• Administer alpha-2 agonist first, opioid 5 minutes later

Question 24

What other drug would you also use and why? for horses

Answer 24

• Add acepromazine to smooth recovery and ↓anaesthetic mortality
  * NOT colic cases

Question 25

What’s a reliable sedative in cats and dogs?

Answer 25

• Alpha 2 receptor agonists very reliable

Question 26

What can be used to calm animals for a long duration? (cats+dogs)

Answer 26

• Acepromazine

Question 27

What would you use in very old, very sick, very young cat/dog?

Answer 27

Benzodiazepines