Intravascular volume depletion in a 24-hour porcine model of intra-abdominal hypertension.

Background: The purpose of the study was to examine hemodynamic parameters and intravascular volume in a porcine model in the presence of intra-abdominal hypertension (IAH) lasting for 24 hours.

Methods: Twelve pigs (52.5 +/- 4.9 kg) were studied over a period of 24 hours. In six animals, the intra-abdominal pressure was increased to 30 mm Hg via carbon dioxide-pneumoperitoneum. The others served as controls. Using the double-indicator dilution technique, intrathoracic blood volume (ITBV), total circulating blood volume, and cardiac output (CO) were measured. Standard parameters (e.g., central venous pressure [CVP]), were also recorded.

Results: In the presence of IAH, ITBV and total circulating blood volume were significantly reduced to 55% and 67% of control values. CO decreased to 27% and CVP increased fourfold.

Conclusion: IAH leads to significant intravascular volume depletion that is not reflected by the CVP. Assessment of CO and ITBV in the presence of a critically increased intra-abdominal pressure is therefore recommended.