The effects of increased intra-abdominal pressure (IAP) on hepatic perfusion were studied in five anesthetized pigs. Doppler flow probes were used to measure hepatic artery blood flow (HABF) and portal venous blood flow (PVBF), and laser Doppler flowmetry was used to assess changes in hepatic microvascular blood flow (HMVBF). Hepatic blood flow responses to 10, 20, 30 and 40 mm Hg increases in IAP were assessed while the mean arterial BP (MAP) was maintained at baseline levels with IV crystalloid infusions. Although cardiac output and MAP were normal, HABF and HMVBF fell significantly with 10 mm IAP, and at 20 mm Hg IAP, HABF was 45% of the control value, PVBF was 65% of the control value, and HMVBF was 71% of the control value (p less than 0.05). At 30 and 40 mm Hg, hepatic blood flow was reduced even more. Thus, modest increases in IAP can cause significant impairment of hepatic perfusion despite a normal BP and cardiac output