Intra-Abdominal Pressure and the Morbidly Obese Patients: The Effect of Body Mass Index

Abstract

Abdominal compartment syndrome and intra-abdominal hypertension cause morbidity and mortality. Body mass index (BMI) may affect intra-abdominal pressure (IAP). Knowledge of the baseline IAP in the obese and the effect of BMI are not clearly defined. IAPs were measured in 37 morbidly obese patients undergoing elective gastric bypass. Measurements were obtained via bladder pressure using a standard technique. IAP was measured after intubation (P1) and postoperatively after extubation (P2). Data collected included age, gender, BMI, previous surgeries, comorbidities, IAP, and laparoscopic versus open procedure. Mean BMI was 47.7 kg/m (range, 37-71.8 kg/m), and mean age was 45 years (range, 32-64 years). P1 mean was 9.4 mm Hg +/- 0.6 mm Hg, and P2 mean was 10.0 mm Hg +/- 0.6 mm Hg. Laparoscopic versus open procedure was unrelated to postoperative IAP. Previous surgeries and comorbidities were unrelated to IAP. P1 increased as BMI increased. For each unit increase of BMI, IAP increased by 0.14 mm Hg +/- 0.07 mm Hg (p = 0.05). Higher BMI and age were independent predictors of increased P2, with IAP increased 0.23 mm Hg +/- 0.07 mm Hg for each unit BMI (p = 0.0015) and 0.20 mm Hg +/- 0.06 mm Hg for each year increase in age (p = 0.0014). Baseline IAP in the obese is greater than normal weight population (0-6 mm Hg), but not in range of intra-abdominal hypertension (>12 mm Hg). Postoperative status is unrelated to IAP. Elevated BMI does impact IAP, but the incremental value is small. Markedly increased IAP should not be attributed solely to elevated BMI and should be recognized as a pathologic condition.