ObjectiveIncreased intra-abdominal pressure (IAP) compromises cardiopulmonary function and visceral perfusion. Our goal was to characterize acute changes in these subsystems associated with operative abdominal decompression.Patient Population25 mm Hg).Main Outcome MeasuresStudied hemodynamic variables included pulmonary artery occlusion pressure (PAOP), right ventricular end-diastolic volume index (RVEDVI), and cardiac index (CI). Pulmonary variables included shunt fraction (Qs/Qt) and dynamic compliance (Cdyn). Visceral perfusion was assessed using hourly urine output 4 hours before and after decompression (UOP) and gastric intramucosal pH (pHi). Mean values before and after decompression were compared using the paired t test. Linear regression and Fisher's z transformation were used to evaluate the relationships between RVEDVI, PAOP, CI, and IAP. IAP was transduced via bladder pressures. Significance was defined as p < 0.05. Data are expressed as means +/- SD.ResultsIAP decreased with decompression (49 +/- 11 to 19 +/- 6.8 mm Hg; p < 0.0001). RVEDVI improved independent of CI and correlated better (p < 0.01) with CI (r = 0.49, p = 0.04) than PAOP did (r = -0.36, p = 0.09). PAOP correlated significantly with IAP (r = 0.45, p = 0.04). Decompression resulted in significant improvements in Qs/Qt, Cdyn, UOP, and pHi.ConclusionAbdominal decompression in patients with increased IAP improves preload, pulmonary function, and visceral perfusion. Elevated IAP has important effects on PAOP, which makes the PAOP an unreliable index of preload in these patients.