A Comparison of the Volume and pH of Gastric Contents of Obese and Lean Surgical Patients

Abstract

Obese surgical patients are typically considered to be more likely than lean patients to possess high-volume and low-pH (HVLP) gastric contents after a standard preoperative fast, based on a study of a population predominately consisting of patients receiving intramuscular preoperative sedation. We revisited this issue in a study population of 256 fasted surgical patients, of which 232 received no preoperative antacid or gastric prokinetic drug. Immediately after endotracheal intubation, an 18-French sump tube was placed, and gastric contents were withdrawn. Subjects' gastric contents were defined as HVLP if they exhibited a combination of a volume >25 mL and a pH <2.5. Obesity was defined as a body mass index >30. Among nonmedicated obese patients, the proportion with HVLP gastric contents was 20 of 75 (26.6%). The proportion of lean patients with HVLP gastric contents was 66 of 157 (42.0%). The difference between the HVLP proportions for these two groups was found to be significant (P < 0.05) using chi squared analysis. Obesity seems to be associated with a significantly decreased risk of HVLP gastric contents among surgical patients with no history of gastroesophageal pathology after a normal interval of preoperative fasting. Implications: Previous studies have shown that obese surgical patients have a greater volume of acidic stomach contents than lean patients, despite a routine preoperative fast. We have reexamined this issue and found that among otherwise healthy, fasted, obese surgical patients, there is a lower incidence of combined high-volume, low-pH stomach contents compared with lean patients.