Clinical sedation + premedication Flashcards
When would you premedicate?
Prior to anaesthesia
Why sedate?
- Relieve patient anxiety
- Facilitate handling of patient
- Provide analgesia
- Provide muscle relaxation
- To enable procedures or interventions to be carried out
Why premedicate?
- 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)
What qualities would the perfect premed/sedative have?
- 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
With nervous patients what could you give them - pre-appointment?
horses?
Cats + dogs?
- Equine
- acepromazine oral gel, detomodine
oromucosal gel
- acepromazine oral gel, detomodine
- Dogs and cats
- Gabapentin: 2 hours before appointment
- Trazadone
What are the different opioids you could use?
- Butorphanol - kappa
- Buprenorphine - partial Mu
- Methadone
- Fentanyl
- (morphine) - not licenced
Other drug options - categories and drugs within categories?
- Phenothiazines
* Acepromazine - Alpha 2 receptor agonists
* Xylazine, detomidine, romifidine,
medetomidine, dexmedetomidine - Benzodiazepines
* Diazepam, midazolam - Adjuncts
* Propofol, alfaxalone, ketamine
What are the pros/cons of opioids?
- May be adequate alone (mild sedation)
- Often good sedation if the animal presents
very painful or critically ill - Respiratory depression (methadone,
morphine, fentanyl)
Pros/cons of acepromazine?
- 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
Cons of acepromazine?
- 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
Pros of Alpha-2-agonists?
- 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%)
Cons of Alpha-2-agonists?
- 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
Pros of benzodiazepines?
- Useful for
* very young
* very old
* very sick - Minimal Side effects
- Antagonist: flumazenil
Cons of benzodiazepines?
- Unreliable sedation (paradoxical excitation)
- No analgesia
- Moderate MAC sparing effect
- Not suitable
* farm animals (not licensed)
Opioids administration?
- intravenous - rapid onset
- intramuscular
- subcutaneous - less reliable
- transcutaneous (fentanyl)
Acepromazine administration?
- intravenous - smaller dose needed
- intramuscular - detomidine only
- subcutaneous
- oral (gel: horses, tablets: dogs, cats) - less reliable
Alpha-2-agonist administration?
- intravenous - faster onset + smaller dose
- intramuscular
- subcutaneous - less reliable
- transmucosal
Benzodiazepines administration?
- intravenous - faster onset + smaller dose -
can cause paradoxical effect - intramuscular (midazolam) - less reliable
- oral (diazepam, not cats)
- rectal
What must a drug have for food producing animals?
- Specified withdrawal period
- Maximum residue limit
What sedatives can be used for food producing animals?
-butorphanol
-xylazine
-detomidine
-(azaperone for pigs)
Why do we need to be careful administering xylazine to ruminants?
Very sensitive to the drug
give 1/10 the dose you would give a horse
What is a reliable sedative in adult horses?
- Alpha-2 agonists reliable sedation of adult horses
With horses what would you administer first and what after?
- Administer alpha-2 agonist first, opioid 5 minutes later
What other drug would you also use and why? for horses
- Add acepromazine to smooth recovery and ↓anaesthetic mortality
* NOT colic cases
What’s a reliable sedative in cats and dogs?
- Alpha 2 receptor agonists very reliable
What can be used to calm animals for a long duration? (cats+dogs)
- Acepromazine
What would you use in very old, very sick, very young cat/dog?
Benzodiazepines
