Effect of intra-abdominal pressure on abdominal wall blood flow

Adverse effects of increased intra-abdominal pressure (IAP) on cardiac, pulmonary, and renal function have been well described. Abdominal wound healing complications seen in the massively injured patient may also be associated with IAP. The effects of IAP on abdominal wall blood flow, however, have not been documented. This study examines rectus sheath (RS) blood flow in a porcine model of increased IAP. Seven domestic swine were anesthetized with pentobarbital and maintained with isoflurane. Swan-Ganz and femoral arterial catheters were placed for measurement of mean arterial pressure (MAP), cardiac output (CO), and pulmonary capillary wedge pressure (PCWP). A midline incision was performed for placement of laser flow probe on the RS and for placement of catheters to raise and measure IAP. Intra-abdominal pressure was then increased by installation of lactated ringers (LRs) into the peritoneum. Mean arterial pressure was maintained throughout the procedure with intravenous LR. Hemodynamics and RS blood flow data were obtained at baseline, 10, 20, 30, and 40 mm Hg IAP. Analysis of data was done by paired t-test with level of significance at P less than 0.05 and linear regression. Rectus sheath blood flow was significantly reduced at all pressure levels when compared to baseline and negatively correlated (r = -0.82) with increasing IAP. Since indices of systemic perfusion were maintained with increasing IAP, the decreased RS blood flow is most likely due to increased compartmental pressure within the abdomen.