BACKGROUND: Two results have been conflict regarding the pH of gastric contents in obese and lean surgical patients. Obese patients have been considered to have lower pH of gastric contents than lean surgical patients since the study by Vaughan, whereas Harter reported no significant difference in the pH's of obese and lean surgical patients. The author wanted to investigate whether gastric content pH differs or not between obese and lean surgical patients aged from 20 to 60 years.

METHODS: Forty patients scheduled for elective abdominal hysterectomy under general endotracheal anesthesia were studied. Group I (n = 20) was composed of lean patients whose body mass indices (BMIs) were between 20 and 25, whereas Group II (n = 20) was composed of obese patients whose BMIs were above 30. Every patient was fasted between 8 and 14 hours preoperatively. Within 10 minutes of endotracheal intubation, gastric contents were withdrawn with a 20 cc syringe connected to a 16F nasogastric tube placed in the stomach. pH and the incidences of pH < 2.5, and pH < 1.8 were compared.

RESULTS: No significant difference in pH (P = 0.199) or in the incidences of pH less than 2.5 (P = 0.23) or 1.8 (P = 0.52) were observed between obese and lean patients.

CONCLUSIONS: Obese and lean patients have similar fasting gastric pH's, as long as the obesity is not too severe (BMI under 40).