Anaesthesia Flashcards
Name 5 inhalational agents.
- Sevoflurane
- Isoflurane
- Desflurane
- Nitrous oxide
- Xenon
Name 4 intravenous agents.
- Propofol
- Etomidate
- Barbiturates
- Ketamine
What properties are ideal for inhalational agents?
Non-flammable
Stable
High potency
Fast onset
What 3 factors are involved in the triad of balanced anaesthesia?
- Unconsciousness
- Analgesia
- Muscle relaxation
Why is a combination of agents normally used?
Safer than a large single dose.
-minimises side effects
How is potency measured in anaesthetics? (2)
- INHALED: Minimum Alveolar Concentration (MAC)
- IV: Cp50
What is the minimum alveolar concentration (MAC)?
Concentration of vapour in lungs needed to prevent movement in 50% of subjects.
What is Cp50?
Minimum plasma concentration needed to prevent movement in 50% of subjects.
What is the Meyer Overton theory?
Describes correlation between lipid solubility of anaesthetics & MAC.
» suggests anaesthesia occurs when sufficient molecules dissolve in the lipid cell membrane.
Now shown to be false.
How can neurobiological effects of anaesthetics be classified?
By effects on different receptors.
What are the clinical features of group 1 (etomidate, propofol, pentobarbital)?
- Strong hypnotics
- Strong amnestics
- Weak immobilisers
- Slow cortical EEG
What is the ratio of MAC-imob to MAC-awake for group 1 (etomidate, propofol, pentobarbital)?
4
What are the molecular targets of group 1 (etomidate, propofol, pentobarbital)?
GABAa receptors.
What are the clinical features of group 2 (NO, ketamine, xenon, cyclopropane)?
- Weak hypnotics
- Weak immobilisers
- Potent analgesics
- No EEG slowing
What is the ratio of MAC-imob to MAC-awake for group 2 (NO, ketamine, xenon, cyclopropane)?
1.5(N2O) - 2 (Xe)
What are the molecular targets of group 2 (NO, ketamine, xenon, cyclopropane)?
- NMDA receptors
- AMPA receptors
- Neuronal nAChRs
- 2 pore K+ channels
What are the clinical features of group 3 (Halogenated ethers & alkanes)?
- Strong hypnotics
- Strong amnestics
- Strong immobilisers
- Slow cortical EEG
What is the ratio of MAC-imob to MAC-awake for group 3 (Halogenated ethers & alkanes)?
2-3
What are the molecular targets of group 3 (Halogenated ethers & alkanes)?
- GABAa receptors
- Glycine receptors
- Glutamate receptors
- Neuronal nAChRs
- 2 pore K+ channels
What does low solubility of inhalation agents lead to?
Fast onset & quick recovery.
What are low solubility inhalation agents most commonly used for?
Maintenance.
What action do highly fat soluble agents have?
Slow equilibrium & perfusion in fat.
|»_space; accumulation (‘hangover effect’)
Which inhalation agent has a MAC value of 100%?
Nitrous oxide.
Which inhalation agent has a very high oil:gas ratio, and a slower recovery?
Halothane
What sort of action so IV agents have?
- Quick onset
- Short duration
What are IV agents most commonly used for?
Induction.
What are possible side effects of general anaesthetics? (3)
- Vasodilation
- Decrease cardiac contractility
- Can affect organ perfusion
What are possible side effects of inhalational agents?
- Malignant hyperthermia
- Hepatotoxicity
What are possible side effects of IV agents?
- Allergy
- Pain on injection
