injectable anesthetics

barbiturates- main uses

• anticonvulsant

• euthanasia

• in the past- induction and mainenance of anesthesia

barbiturates- general characteristics

• controlled substances

• not reversible

• no analgesia

• IV admin only

• highly lipid soluble

barbiturates- groups according to duration

• ultra short- methohexital, thiopental

• short- pentobarbital

• long- phenobarbital

phenobarbital

• long acting

  • onset following IV ~12 min

  • duration 6-12 hrs

• primary use- anticonvulsant

pentobarbital

• short acting

  • duration 1-3 hrs

• primary use- euthanasia solution

  • 2x the anestheisa dose

thiopental, methohexital

• ultra short acting

  • duration 10-20 min

• thiopental unavailable

barbiturates- CNS effects

• CNS depression

  • degree depends on dose and type of barbiturate

• anticonvulsants

• excitement during induction and recovery

  • prolonged stage II

barbiturates- other effects

• resp and cardio depressants

• tissue irritation

• increased potency/duration in sighthounds/lean animals

cyclohexamine - general characteristics

• controlled substances

• not reversible

• some analgesia - NMDA antag

• IV or IM admin

cyclohexamines- CNS effects

• CNS stimulation

  • disrupts NS pathways, “trance like” anesthesia

• increases CSF, ICP, IOP

• lowers seizure threshold

• increased sensitivity to sight, sound, touch

• emergence delirium

cyclohexamines- cardio effects

• tachycardia and increased BP

cyclohexamines- other effects

• apneustic respiration

• increased muscle tone (catalepsy)

• some reflexes may remain

• ptyalism

ketamine

• most common induction agent used

• can be used as sole agent for short procedures

• high doses can control seizures

ketamine- metabolized by

• dogs- liver

• cats- kidneys

ketamine- IV admin

• faster onset of action and recovery

  • onset 30-90 sec

  • duration 3-10 min

• smaller dose than IM

• no tissue irritation

ketamine- IM admin

• good for fractious animals

• longer duration

  • onset 2-4 min

  • duration dog- 20-30 min, cat- 30-60 min

ketamine combos

• common to mix with a tranquilizer or sedative

• most common combo- KetVal

  • ketamine and diazepam

  • can mix in same syringe

• new combo- ketafol

  • ketamine and propofol

tiletamine

• very similar to ketamine

• in telazol

  • tiletamine and zolazepam

  • IV or IM

propofol - general characteristics

• ultra short acting- rapidly metabolized

• not controlled

• no analgesia

• not reversible

• wide margin of safety

propofol- cardio effects

• hypotension immediately after injection

  • d/t vasodilation

  • give IV fluids to minimize

propofol- resp effects

• resp depression

  • transient apnea

propofol- onset/duration

• onset- <60 sec

• duration- 5-10 min

• complete recovery- 20-30min

propoflo vs propoflo 28

• propoflo- limited shelf life

  • no preservative

  • lasts 6 hrs after opening

• propoflo 28

  • contains benzyl alcohol

  • lasts 28 days

etomidate

• ultra short acting

• no analgesia

• not controlled

• not reversible

• wide margin of safety

etomidate- effects

• minimal cardio effect

• mild resp depression

• suppression of adrenal cortical axis

  • decreased cortisol and aldosterone production

etomidate- admin

• IV only- can experience pain on admin

  • give with fluids

• rapid loss of consciousness

• duration- 10-20min

alfaxalone- general characteristics

• ultra short acting

• controlled substance (C IV)

• IV admin or IM off label

alfaxalone- effects

• minimal dose dependent effects on cardio system

• minimal dose dependent effects on resp system

  • apnea can occur

alfaxan vs alfaxan multidose

• alfaxan

  • shelf life 6 hrs

• alfaxan multidose

  • shelf life 28 days

alternative kitty magic

• IM admin

• DTA

  • dexmedetomidine

  • tobugesic

  • alfaxan

guaifenesin

• muscle relaxant, not anesthetic

• given in large animal to help with induction/maintenance

pre- oxygenation

• mask or flow by

• increases oxygen saturation of hgb

  • desaturates in 90 sec without pre oxygenation