Anaesthesia induction and lower oesophageal sphincter pressure.

The effects of some drugs generally used in premedication for and induction of anaesthesia on the lower oesophageal sphincter (LOS) pressure were investigated in 30 dogs, using the modern oesophageal manometric technique. In thiopental-induced anaesthesia, a distinct pressure gradient was noted between the LOS and gastric pressure. Atropine eliminated this pressure gradient almost completely. Metoclopramide increased the LOS pressure significantly, and subsequent atropine administration was unable to bring it down. Metoclopramide administered after atropine was unable to elevate the LOS pressure reduced by atropine. Succinylcholine had no observable lasting effect on the LOS pressure. The present findings seem to indicate that of the drugs generally used in premedication for and induction of anaesthesia, atropine significantly reduces the LOS competence, thereby creating favourable conditions for gastro-oesophageal reflux (GOR) and consequent postoperative pulmonary complications. Use of metoclopramide in premedication for or induction of anaesthesia to eliminate the depressant effect of atropine on the LOS pressure appears to be indicated.