Volume and pH of gastric contents were measured after anaesthetic induction in 99 in-patients undergoing general and vascular surgery scheduled for either morning (50) or afternoon (49) lists. Significantly fewer patients in the morning group had pH values below 2.5. The mean pH value of the morning group was significantly higher than that of the afternoon group. There was a positive correlation between duration of fast and pH (the longer the more alkaline) for the groups combined. No significant relationship could be shown for any factor with volume.
