Choosing a premed Flashcards
Duration
- ACP
- alpha 2 agonist
- 4 hours, sometimes longer
- 1-3 hours
Reversibilty
- ACP
- alpha 2 agonist
- no
- yes; atipamezole
Sedative effect
- ACP
- alpha 2 agonist
- generally mild, slightly unpredicatble
- dose dependent; may be marked
Effect on BP
- ACP
- alpha 2 agonist
- decreases
- increases then stabalises: stimulates alpha2 receptos: causes vasoconstriction: very pale MM. This causes hypertension. Baroreceptors then kick in; stimulating vagus decreasing HR. (can’t act upon vascular tone) goes from hyper to normotensive
Effect on HR
- ACP
- alpha 2 agonist
- variable; may increase or decrease
- decreases!
Effect on ventilation
- ACP
- alpha 2 agonist
- minimal
- usually slows rate but blood gases are well maintained (: they have a lower RR but oxygenation is higher than normal)
analgesia
- ACP
- alpha 2 agonist
- none
- moderate
Bensodizipine pharmacological effects
- minimal effects on CV and respiratory systems
- paradoxical excitement in healthy animals but good in already ‘sick’ (depressed) patients
Benzodiazepine options
diazepam – preferably IV only
midazolam – any route (water soluble)
- None licensed for vet
Antimuscurinics (anticholinergics)
- use
- options (2), their onset and duration and liscensing
Treatment of vagally induced bradycardia only (very unpleasant side effects: dry mouth, dilated pupils.)
atropine
- fast-onset, short duration
- licensed in dogs and cats
glycopyrrolate (glycopyrronium)
- slow onset, long duration
- not licensed in animals
Antimuscurinics side effects
tachycardia
mydriasis
‘dryness
when would you use a partial alpha 2 agonist?
minor / relatively non-painful procedure
when would you use a full opioid agonist (alpha 2)
moderate to severely painful procedure, or where you’re unsure (never wrong to give it)
Why would you combine ACP and alpha 2 agonist?
- synergistic effects
- improved sedation with lower doses of each
- lesser cardiopulmonary depression
2y/o healthy lab considerations?
- will get excited is a BZP
- As size of dog increases, size of CNS does not necessarily increase with it: give bigger dose but not double!
8 m/o bull dog considerations?
- BOAS (brachycephalic obstructive airway syndrome): want as light as possible
- think about the fact that alpha 2 provides a deep sedation but will recover faster (so if choosing alpha 2 use a low dose)
15 y/o collie cross considerations?
- potential organ impairment (heart, liver, kidneys)
- increased CNS drug sensitivity
- slower drug metabolism
7 year old GSD with ruptured splenic mass. considerations?
- hypovolemic? give fluids first!
- ACP: NO animal is vasoconstricted to maintain BP and this will cause them to vasodilate
- Alpha2: will drop CO
- BZP best choice!
8 year old CKCSp. considerations?
- consider what effect premedicants will have on underlying heart disease?
- Prone to mitral endocardiosis
- BZP probably not best
- Alpha2: cause vasocontriction and make sit harder for blood to pump into aorta which increases regurgitation fraction
- ACP: will vasodilate a bit which improves blood flow. Also antiarrhythmic
- Opioid: partial is adequate
2 commonly used drug combinations in cats
midazolam 0.2mg/kg
ketamine 5-10mg/kg
mixed, given IM (stings!!)
provides effective sedation in cats
medetomidine at up to 80g/kg butorphanol at 0.2mg/kg ketamine at up to 5mg/kg mixed, given IM (stings!!) provides effective sedation (bordering on anaesthesia) in cats
Ketamine
- use
- why is it less commonly used in dogs?
- Can be useful in combination with other drugs for sedation/premedication
- less use in dogs as more predisposed to CNS excitation than cats; more likely to seizure
