Antacid anticholinergic regimens in patients undergoing elective caesarean section

The pH and volume of gastric contents were examined in 60 patients undergoing elective Caesarean Section under thiopentone, nitrous oxide-oxygen, succinylcholine anaesthesia. All patients received Gelusil 30 ml per os preoperatively, while 20 were given atropine 7 microgram X kg-1 and another 20 glycopyrrolate 4 microgram X kg-1 intramuscularly along with Gelusil. Following tracheal intubation, gastric fluid was sampled through an orally placed 18 French Salem Sump tube. After Gelusil alone, the mean gastric fluid pH was 4.54 +/- 2.45 (SD) while it was significantly higher following the combined use of antacid and atropine (6.78 +/- 1.20) or antacid and glycopyrrolate (6.42 +/- 1.72), (P less than 0.01). Differences in gastric fluid volume between the groups were insignificant. All three regimens produced a gastric pH greater than 2.5 when given less than 75 minutes before sampling. When the premedication to sampling interval exceeded 75 minutes the addition of atropine or glycopyrrolate decreased the incidence of gastric pH less than 2.5 from 47 per cent in patients given Gelusil alone to 6 per cent and 14 per cent, respectively. In comparison to Gelusil alone, this difference was significant with atropine (P less than 0.05) but not with glycopyrrolate. Atropine and glycopyrrolate respectively produced 6 per cent and 7 per cent incidences of pH lower than 2.5 combined with gastric volume greater than 25 ml, which were significantly lower than was observed with Gelusil alone (P less than 0.05). This study demonstrates that the addition of atropine or glycopyrrolate to Gelusil premedication provides additional protection against the consequences of aspiration, especially when the premedication to anaesthetic induction period is prolonged.