Induction of anaesthesia Flashcards
anaesthetic agents - injectable
Propofol Alfaxalone Ketamine thiopentone/ Thiopental Etomidate
anaesthetic agents - inhalational
Isoflurane Sevoflurane Halothane Desflurane Nitrous oxide (N20) Xenon
choice of induction - depends on
Species and temperament of animal Underlying medical conditions Nature of procedure Available drugs, equipment & conditions Personal preference & experience
general anaesthetic side effects
Cardiovascular depression - decr CO, Vasodilation, decr BP when monitoring
Respiratory depression- Decr respiratory rate, tidal volume, minute volume
Dose-dependent
pharmacokinetics
Uptake - Time to reach adequate blood and brain levels, Effect of route of administration
Distribution into tissues - Depends on blood flow, May be influenced by disease, Lowers blood levels
Metabolism - Species variable, Influenced by disease
Elimination
dosages for induction
depends on species, temper, pre-existing conditions, age
Amount of premedication/ sedation
Doses provided here are GUIDELINES
Generally administer slowly and to effect
propofol
phenol
Must be given i/v
induction and maintenance of anaesthesia
White emulsion: containing lipid
Rapid onset after injection
Blood levels decrease by redistribution
Rapid metabolism - Hepatic and extra-hepatic
Cardiovascular depression Vasodilation, decreased blood pressure
Respiratory depression
give slowly to effect
propofol and cats
Cats lack the enzymes to conjugate glucuronides - Metabolism of propofol is quite slow
Also have problems metabolising triglycerides
Recovery is slower than in the dog
Cumulative
Toxic effects more likely with repeated use
Repeated anaesthesia with propofol in cats may cause oxidative injury and Heinz body production.
propoclear
Propofol in a nano-droplet micro emulsion form
Clear, colourless liquid
Preservatives: 28 day shelf life
Introduced recently then rapidly withdrawn from market due to high incidence of painful reactions on injection
propofol plus
No pain on injection was observed
Gives dogs and cats the smooth, rapid inductions + recoveries like propofol.
Is designed to help reduce anaesthetic waste (*Once broached use within 28 days).
Has a familiar milky white appearance, allowing for easy visual identification.
Rarely causes local tissue reaction with inadvertent perivascular administration
benzyl alcohol
preservative
Benzyl alcohol toxicity may lead to prolonged recovery + hyperkinesia in cats
neurological signs - tremors in dogs and fatalities in both species.
no specific antidote; supportive treatment should be given.
alfaxalone
steriod
Poorly soluble in water so marketed with a solubilising agent (cyclodextrin)
Can be given i/v or i/m
Can be used for induction and maintenance of anaesthesia
Rapid onset of action, short duration
Can see excitement on recovery if not adequately sedated
Less cardiopulmonary depression than propofol
ketamine
Dissociative anaesthetic
analgesic actions at sub-anaesthetic doses
Can be given i/m or i/v
Can be used for induction and maintenance of anaesthesia
Excitation if given alone - always combined with other sedative agents
ways to use ketamine
“triple combination” - aggressive cats, i/m, onset of action 5 mins
Horses - After profound sedation with α-2 agonist
ketamine - effects
CNS effects: Reflexes preserved (eg palpebral reflex), jaw tone, swallowing
Cardiovascular system: stimulation of sympathetic nervous system
Mild hypertension and tachycardia
Some direct CV depression
Mild respiratory depression
Analgesia
