Determining gastric contents during general anaesthesia: evaluation of two methods

Two methods used to measure the volume of gastric contents were evaluated in 24 supine anaesthetized adults. Methods compared were: (1) aspiration of stomach contents through a large, vented, multi-orificed gastric tube, and (2) indirect determination by a dye dilution method using polyethylene glycol (PEG) as the marker. The volumes determined by these methods (Vasp and Vpeg respectively) were compared to the total volume (Vtot) present in the stomach, determined by direct inspection of the gastric pouch by the surgeon at the beginning of surgery. The results show that the volume of aspirated gastric fluid, using this type of tube, is a very good estimate of the total volume of gastric residue. The PEG dilution method yields similar results. However, correlation between Vpeg and Vtot was not as close-fitting as the correlation between Vasp and Vtot. PEG dilution is more complicated, time-consuming and offers no advantage over aspiration.