What is normal intra-abdominal pressure?

The causes and effects of increased intra-abdominal pressure and abdominal compartment syndrome have been well documented. However, there have been no large series to determine normal intra-abdominal pressure in hospitalized patients. The purpose of this study was to determine normal intra-abdominal pressure in randomly selected hospitalized patients and to identify factors that predict variation in normal intra-abdominal pressure. A total of 77 patients were prospectively enrolled between September 1998 and July 1999. Data obtained included patient demographics (i.e., age, gender, height, weight, and body mass index), reason for hospitalization and bladder catheterization, previous and current surgical status, comorbidities, and intra-abdominal pressures. Intra-abdominal pressure readings were obtained through an indwelling transurethral bladder (Foley) catheter. Data were analyzed by analysis of variance and multiple regression analysis. There were 36 females and 41 males with a mean age of 67.7 years. Average weight, height, and body mass index were 79.6 kg, 1.70 m, and 27.6 kg/m2, respectively. Mean intraabdominal pressure was 6.5 mm Hg (range 0.2-16.2 mm Hg). Body mass index was positively related to intra-abdominal pressure (P < 0.0004). Gender, age, and medical and surgical histories did not significantly affect intra-abdominal pressure. However, using multiple regression analysis, a relationship between intra-abdominal pressure, body mass index, and abdominal surgery was discovered. Intra-abdominal pressure is related to a patient's body mass index and influenced by recent abdominal surgery. Thus, the normal intra-abdominal pressure can be estimated in hospitalized patients by using the derived equation. Knowledge of the expected intra-abdominal pressure can then by used in recognizing when an abnormally high intra-abdominal pressure or abdominal compartment syndrome exists.