GA Flashcards
Which inhaled general anaesthetic has some significant metabolic degradation from CYP450 enzymes?
Halothane. Approximately 20% metabolised.
Which three inhaled anaesthetics are most likely to have liver toxicity (in descending order of likelihood)?
Halothane
Isoflurane
Desflurane
If you were seeking a more potent anaesthetic, would you want a smaller or higher MAC?
Smaller. If it’s a smaller concentration required to produce no response to surgical stimulus, that implies a higher potency.
Lipid solubility is directly proportional or inversely proportional to MAC?
Inversely proportional.
An increasing lipid solubility indicates a more potent anaesthetic, meaning less concentration for an effective dose, i.e. lower MAC.
What do gaseous anaesthetics do on a cellular level?
Stabilise the open state of the GABAA receptor and stabilise the closed or desensitised state of the nicotinic receptor.
How do fatty tissues affect anaesthesia?
It acts as a resevoir for the anaesthetic during recovery, lengthening the time of recovery.
How significant is metabolic degradation of inhaled anaesthetics?
It is very insignificant. It is more important to monitor induction/recovery and respirations to determine duration of action.
What is MAC?
Minimum alveolar concentration required to have 50% of humans to have no surgical response.
If a patient has mainly lean tissues, will they reach anaesthetic equillibrium quicker or slower?
Quicker.
What anaesthetics can cause a sympathetic discharge?
Nitrous oxide and ketamine.
Intravenous anaesthetics have a duration of action that is long or short?
Short.
Thiopentone: 5-10mins.
Propofol: 2-4mins
What are the stages of anaesthesia (Guedel’s signs)? What does each mean clinically?
- Induction (Pt doesn’t respond to questions)
- Excitement (Pt struggles, coughs, may experience bronchospasm and vomitting)
- Surgical anaesthesia
- Medullary depression (Leads to cardiorespiratory collapse - is a state of overdose)
Propofol and thiopentone, which one is the barbituate?
Thiopentone.
Name the five in-use inhaled general anaesthetics.
Nitrous Oxide Sevoflurane Haloflurane Isoflurane Desflurane
Low solubility (low blood/gas coefficient) indicates what about the rate of induction and what about the rate of recovery?
Fast rate of induction and fast rate of recovery.
High solubility (high blood/gas) coefficient indicates what for rate of induction and what for rate of recovery?
Slow rate of induction and recovery.
Regarding inhaled general anaesthetics, halogenation increases or decreases potencty?
Increases potency.
If a patient’s rate of ventilation is increased, what happens to the rate of induction?
It increases as well.
What are some effects on the CVS from inhaled anaesthetics?
Decreased heart contractility (halothane first, then D/I/S)
Decreased sympathetic activity (halothane and sevflurane)
Decreased systemic vascular resistance (des/iso/sev)
Arrythmias (halo, D/I/S)
Intravenous anaesthetics are not suitable for?
Maintaining anaesthesia.
What are the five aims of ‘balanced anaesthesia’?
LOC Amnesia Relaxation of skeletal muscle Analgaesia Blunting of ANS responses
Which of the intravenous anaesthetics has less chance of producing respiratory depression?
Ketamine.
Intravenous anaesthetics have a duration of action that is long or short?
Short.
Thiopentone: 5-10mins.
Propofol: 2-4mins
