Effect of preoperative fasting time on gastric volume and pH

In order to asses the effect of preoperative fasting time on gastric volume and pH, sixty elective surgical patients, ASA physical status I or II, were divided into group A (NPO less than 10 h) and group B (NPO more than 10 h). No premedication was given. Immediately following induction and intubation, the residual gastric fluid was obtained by suction using a No. 16 Sakem samp tube and its volume and pH measured. Residual gastric fluid volumes showed no statistically significant differences between the two groups (Group A: 31.76 +/- 21.51 mL Group B: 25.93 +/- 13.51 mL; T = 1.236, T less than T 0.05 = 1.96). Values for pH between the groups were also similar (Group A: 1.65 +/- 1.12; Group B: 1.52 +/- 0.73; T = 0.53, T less than T 0.05 = 1.96). Our study suggests that a significant number of patients are at risk for aspiration of acidic gastric contents and that this risk is not lowered by additional preoperative fasting time in excess of 10 h.