16)General anaesthesia Flashcards
1
Q
General Anaesthesia
A
- State characterised by ⇢ Unconsciousness, analgesia, amnesia, skeletal muscle relaxation + loss of reflexes
Balanced anaesthesia:
- Produced by mixture of drugs often including both inhaled + IV agents
2
Q
Preanesthetic medication
A
- Anticholinergic drugs ⇢ Atropine
- Antihistamines ⇢ Promethazine
- Benzodiazepines ⇢ Diazepam/Lorazepam
- Neuromuscular blockers ⇢ Pancuronium bromide
- Hydrogen blockers ⇢ Famotidine
3
Q
Mechanism of action
A
- Excitatory NTs ⇢ Glutamate, ACh, serotonin ⇢ inhibited by GA
- Inhibitory NTs ⇢ GABA + Glycine ⇢ Potentiated by GA
4
Q
Classification - Inhalation
A
N2O - nitrous oxide
Volatile liquids:
- Halothane
- Enflurane
- Isoflurane
- Desflurane
5
Q
Classification - IV anaesthetics
A
- Barbiturates
- Dissociative anaesthetics
- Propofol
- Benzodiazepine’s
6
Q
Minimal alveolar concentration
A
Alveolar anaesthetic conc at which 50% of patients fail to respond to standard surgical stimuli
- Indicated potency of an anaesthetic
- Important for inhaled anaesthetics
- N2O MAC > 100%
7
Q
N2O
A
- Low potency ⇢ must be combined
- Rapid induction + recovery
- Good analgesic properties
- ⇣ Toxicity
Side effects
- Post-operative nausea + vomiting
- Prolonged exposure of N2O ⇢ Oxidises vitamin B12 ⇢ Reversible anaemia
8
Q
Halothane
A
- Widely used agent w/potent anaesthetic activity
- No analgesic properties
Side effects:
- Hypotension
- 30% metabolised in liver ⇢ Repeated use = hepatotoxicity
- Bradycardia
- Cardiac arrhythmias
9
Q
Barbiturates/Thiopental
A
- Ultra-short acting
- High lipid solubility
- Rapid action
- Accumulates in fat
- No analgesic properties
- Narrow therapeutic stage
- Bind to B-subunit of GABAa receptor + potentiates inhibitory action of GABA
10
Q
Propofol
A
- Rapidly metabolised
- ⇣ Blood pressure
- Used for day-case surgery
- FOS-propofol = water soluble derivative
- Propofol interacts w/ beta-containing GABAa-ergic receptors
