What are the principles (goals) of general anesthesia?
- Unconsciousness (hypnosis)
- Analgesia
- Muscle relaxation
- Lack of movement in response to surgical stimulus
TIVA
Total intravenous anesthesia–induction and maintenance of anesthesia using only intravenous agents
PIVA
Partial intravenous anesthesia–induction and maintenance of anesthesia using both intravenous and inhalant agents
What is ‘balanced anesthesia?’
A combination of techniques to achieve induction and maintenance anesthesia (always used now)
Comparison of inhalation and TIVA
- Inhalation
- Equipment demanding
- No cummulation
- Easier to monitor and control anesthetic depth
- Safe airways, 100% O2 mechanical ventilation
- TIVA
- Easier technique
- Drugs may cummulate
- More difficult to monitor and control anesthetic depth
- Airways??
T/F: TIVA does not mean that you don’t give O2
TRUE–Intubation and administration of 100% O2 is beneficial for every anesthetized patient regardless of anesthetic technique and agent of choice!
What are the 2 drug administration strategies for induction of anesthesia?
- Classical–give half the calculated dose slowly IV then top it up with small boluses to effect
- Bolus dosing–give only small boluses up to effect as needed; a single bolus is not expected to be ‘harmful’
What types of systems are the classical and bolus administration techniques?
- Classical = analogue system
- Bolus = digital system
What are the advantages/disadvantages of the digital system?
- Advantages
- Only need to know 1 dose
- May induce anesthesia with smaller doses
- Disadvantages
- First bolus may be too little
- May give double dose initially if indicated
Context-sensitive half-life
- Elimination half-life of an agent after long CRI
- Depends on the duration of the CRI
What are the characteristics of an ideal agent for TIVA?
- Short acting
- Short context sensitive 1/2 life (not cummulating)
- Does not have active metabolite
- Has wide therapeutic window
- Provides smooth recovery, etc.
Propofol-fentanyl TIVA (general)
- Most common in small animal anesthesia
- Give loading dose before
- Start CRI higher, reduce rate later on
Alphaxalone TIVA (general)
- Does not cummulate if CRI is not too long
- Excessive doses may lead to prolonged recovery and dysphoria, especially in cats
- Should combine with opioid analgesics!
Etomidate TIVA
- Quick metabolism, no cummulation
- Almost ideal agent except for one thing:
- Inhibition of cortisol secretion
- Patients died in human ICR after 2-3 days of etomidate CRI
- NOT AN OPTION FOR TIVA
Ketamine based TIVA
- Cumulates after large or repeated doses causing delayed and rough recovery
- Triple dip: anesthetic mixture for horses
- Guaifenesin
- Xylazine (may substitute other alpha2)
- Ketamine
- Suitable for field procedures
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Intro15
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Machine46
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Breathing systems52
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Inhalant anesthesia68
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Patient evaluation45
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Principles of monitoring44
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Monitoring the anesthetized patient37
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Premedication70
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Induction24
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Injectable anesthetics15
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Blood gas analysis34
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Recovery38
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Mechanical ventilation37
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Neuromuscular blocking drugs21
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Ruminant anesthesia52
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Swine anesthesia36
