effect of cigarette smoking in non-per os period on gastric fluid volume and ph

background: we investigated the effects of cigarette smoking in non-per os (npo) period on volume and ph of gastric contents in smoker male patients. methods: in a prospective cohort study, 86 male smoker patients undergoing elective non-abdominal surgery under general anesthesia, were surveyed. they were npo for at least 8-12 hrs. prior to surgery without direction to smoking. then they were divided in two groups in the operation room based on smoking during npo period. the study was continued until 43 patients entered in each group. after induction of anesthesia, gastric contents were aspirated by ng tube then volume and ph of gastric contents were measured. there were no significant differences in basic characteristics of patients such as age and weight between two groups. results: the ph of gastric content was significantly lower in the smokers group (1.57±0.74 vs 3.12±1.90 p=0.001). the mean volume was significantly higher in the smokers’ group (34.60±20.90 vs 19.86±14.72 ml, p=0.001). conclusion: smoking during npo period in habitual smokers before elective surgery increases the volume and acidity of gastric contents and probably increases risk of acid pulmonary aspiration.