• General anaesthesia is a reversible & controlled state of unconsciousness used to provide adequate conditions for surgery

• General anaesthesia is produced by the administration of one or more of a group of drugs called the general anaesthetics

• The general anaesthetics act on the brain

• Two groups of general anaesthetics: intravenous; inhalational

• During unconscious state of general anaesthetics the patient is completely free of pain and immobile except for breathing

• Neuromuscular blockade by neuromuscular blockers instead of using deep anaesthesia maintains cardiorespiratory integrity intraoperatively

• Three phases of general anaesthesia: 1) Induction

2) Maintenance

3) Recovery

INDUCTION

- commencement of anaesthesia when patient is rendered unconscious

- anaesthesia is usually induced by IV anaesthetic or less commonly by inhalational anaesthetic

- if induction is slow the patient may pass through a stage of excitement [rigidity of limbs, coughing, struggling, urination etc] — may be precipitated by external stimulation

- Excitement phase occurs frequently during an inhalational induction which is slower

MAINTENANCE

- anaesthesia is maintained by an inhalational anaesthetic or less commonly by a continuous infusion of an intravenous anaesthetic

RECOVERY

- recovery takes place when the administration of the anaesthetic ceases