Gastric volume and pH in out-patients.
We measured the volume and pH of the gastric content of 21 out-patients and 21 in-patients under general anaesthesia. Gastric tubes were inserted after induction of anaesthesia, and gastric fluids were withdrawn for pH determinations. Gastric volumes were measured by a dilution technique using polyethylene glycol as the indicator and also by measurement of the volume aspirated through a gastrict tube. Out-patients had a mean gastric volume of 69 +/- 17 ml while in-patients had a mean volume of 33 +/- 4 ml. The average gastric pH for the out-patients was 1.8 +/- 0.2 and for the in-patients 2.0 +/- 0.3. Four out-patients had more than 75 ml of gastric fluid of pH less than 2.0. Aspiration through a gastrict tube did not empty the stomach completely and the volume thus obtained gave a falsely low estimate of the gastric volume.
D000328:Adult; D000553:Ambulatory Care; D000768:Anesthesia, General; D005215:Fasting; D005260:Female; D005745:Gastric Acidity Determination; D005750:Gastric Juice; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013270:Stomach / Q000502:physiology*; D013514:Surgical Procedures, Operative