The lower oesophageal sphincter and the anaesthetist.

Pulmonary aspiration of gastric contents during induction of, or emergence from, anaesthesia poses hazards for both surgical and obstetric patients requiring urgent operations. Little emphasis has been placed on the importance of the lower oesophageal sphincter in relation to regurgitation and aspiration. This is especially important since anaesthetic drugs have been known to both decrease and increase lower oesophageal sphincter (LOS) tone. Any drug that will decrease tone will increase the incidence of gastric oesophageal reflux while drugs that increase tone may decrease this hazard. This review outlines the problem of acid aspiration in relation to the LOS and the various drugs which may influence LOS pressure.