Measuring gastric contents during general anaesthesia: evaluation of blind gastric aspiration

Various medications have been reported to decrease gastric content volume and thus risk for pulmonary aspiration. The majority of studies have used blind gastric tube aspiration of stomach contents as the method of measuring the volume of gastric contents. This study evaluated the accuracy of this method by first measuring gastric content volume using blind gastric aspiration and then aspirating residual content in the stomach, using a visually guided flexible fiberoptic gastroscope. Ten obese patients undergoing elective surgery were studied. Gastric contents were collected using a multi-orificed gastric tube and blind aspiration. Immediately after this was completed, residual gastric volume was collected using a visually guided gastroscope. The sum of these two aspirate volumes (true total gastric volume) was statistically compared with the blind aspirate volume. The blind aspirate volume underestimated true total gastric volume by an average of 14.7 ml and was significantly different from true total gastric volume (p less than 0.05). Blind gastric aspiration was thus demonstrated only to approximate true gastric volume. Its use to measure precisely gastric volume cannot, therefore, be recommended.