Anesthetic induction review Flashcards
SA Induction Agents
- Propofol
- Alfaxalone
- Ketamine:Benzodiazepine ¡ Midazolam or diazepam
- Inhalant (mask/tank induction)
- Barbiturate–Thiopental
- Opioid and Benzodiazepine
¡ In very critical cases
÷ ASA 3;4-5
¡ Will not work in healthy patient
propofol onset speed, when to top up
Rapid onset 10-20 sec; top up in 10-20 sec
propofol onset speed in sick patient or heavily sedate
Patient circulation time may be slower in this situation
¡ 20-30 seconds to effect
¡ Give additional boluses in 20-30 seconds
Propofol Advantages
-Titration to effect possible
- High therapeutic index
- Rapid onset; short duration
- can be given as sedative
- non-irritant if injected perivascular (no tissue slough)
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- Can use in liver or kidney disease
¡ No significant direct effects on hepatic or renal function
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- Can use in neonates
¡ With immature liver and renal function
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- Can use if brain disease or seizuring
¡ Lowers cerebral metabolic rate of oxygen use (CMRO2)
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- Not currently scheduled
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- Cardiorespiratory effects can be minimized
¡ When used properly and titrated to effect
¡ Stabilized patients
Propofol Disadvantages
Potential negative CV and Resp effects
¡ Higher doses – rapid administration or unstabilized patients
¡ Apnea, reduced minute ventilation and PaO2
¡ Reduced HR and blood pressure
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- Heinz body formation with repeated daily use in cats
¡ >5 consecutive days for maintenance
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- Large volumes in larger animals
¡ cost
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- Open bottles must be used within 6 hours ÷ Discard unused volumes at end of clinic day
how fast does Ketamine:Benzodiazepine work?
Takes 30 seconds to work, not as fast acting to produce unconsciousness
Ketamine:Benzodiazepine (KV) advantages
- Can titrate to effect
- Can be used as sedative
- Sympathomimetic effects of ketamine maintains
or increases HR, BP (cardiac output)
¡ When sympathetic hormones still in animal for neurotransmission then this increase in sympathetic tone overrides direct negative effects
¡ Advantages of this tone in mildly compromised or healthy cases on induction
Ketamine:Benzodiazepine disadvantages
- Sick animals see direct myocardial depression ¡ Reduced blood pressure and cardiac output
¡ When sympathetic stores depleted
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¡ arrhythmia potential
¡ increase in HR to tachycardic levels possible
÷ Tachycardia not ideal as not as much time for venous return to
heart
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Salivation
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Scheduled –abuse potential
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Limit dose or use in chronic kidney disease (CKD)
¡ cats
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Limit dose in cases with significant liver disease
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Increased muscle tone
¡ Ketamine behaviour in recovery
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Neurologic brain cases not ideal as may increase CMRO2
¡ Diseased brain already has high CMRO2 and further increase not ideal
alfaxalone speed of effect
Rapid effect with first bolus -10-20 sec
÷ Arouse quickly! Watch transfer to inhalant!
Alfaxalone Advantages
-Titration to effect is possible -High therapeutic index
-Rapid onset /Short duration
-Can be used as TIVA
-Can be given IM in cats for sedation (1-3 mg/kg)
¡ Not irritating if injected peri-vascularly
-Not scheduled; no additional recording required
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Can use in liver or kidney disease
¡ No significant effects on hepatic or renal function
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Can use in neonates
¡ With immature liver and renal function
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Cardiorespiratory effects can be minimized
¡ When used properly and titrated to effect
¡ Stabilized patients
Alfaxalone Disadvantages
Dose dependent cardio-respiratory changes
¡ Decrease BP
¡ Decrease RR and minute ventilation
¡ HR change varies in species
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÷ Pre-med required to prevent recovery excitement
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Most common side effect
¡ Apnea
¡ Excitement - Quiet recovery area ideal
