EFFECTS OF INTRAABDOMINAL PRESSURE ON RENAL TISSUE PERFUSION DURING LAPAROSCOPY

An animal model was established to study the effects of elevated intra -abdominal pressure (IAP) on systemic and renal hemodynamics during la paroscopy. In a pilot study in five dogs, we simultaneously recorded c arotid artery blood flow (CABF), carotid artery blood pressure (CABP), inferior vena caval pressure (IVCP), renal parenchymal blood now, and IAP. The renal parenchymal blood now was measured by a laser Doppler flowmetry (LDF) needle probe and the renal artery blood flow by an ult rasonic Doppler probe, both placed through laparotomy. The reliability and reproducibility of these two measurements at different renal perf usion pressures were documented. The established method was then used to assess the effects of increased IAP on renal hemodynamics during la paroscopy in six pigs. Pneumoperitoneum was achieved by insufflating t he abdominal cavity with air. The LDF needle probe was inserted into t he renal parenchyma laparoscopically. An increase in IAP from 0 to 40 mm Hg did not influence CABP. However, significant decreases in CABF w ere seen from 190.8 +/- 59.5 mL/min at 0 mm Hg IAP to 169 +/- 43.6 mL/ min at 15 mm Hg. The CABF decreased in a linear fashion as IAP was inc reasing (correlation coefficient R = 0.976). Renal cortical blood flow (RCBF) decreased from 50.1 +/- 17.7 mL/min per 100 g at 0 mm Hg to IA P to 21.2 +/- 9.6 mL/min per 100 g of tissue at 15 mm Hg. There was an exponential correlation between IAP and RCBF (R = 0.897). Renal medul lary blood flow (RMBF) demonstrated two patterns: an increase from 8.8 +/- 3.3 mL/min per 100 g at 0 mm Hg IAP to 25.0 +/- 15.1 mL/min per 1 00 g of tissue at 20 mm Hg and then a drop to 15.3 +/- 4.2 mL/min per 100 g at 40 mm Hg IAP. Elevation of the IVCP by occlusion of the intra thoracic IVC resulted in a minimal influence on the renal parenchymal perfusion. Manual compression over the left ventricle decreased equall y CABF and RCBF. Thus, three factors contribute to the renal hemodynam ic changes under elevated IAP: the local compressing effect of the pne umoperitoneum, decreased cardiac output, and impaired venous return. A shunting mechanism within the parenchymal vasculature may be the expl anation for the hemodynamic changes in the renal medullary region. Fin ally, because elevation of the IVCP and decreased cardiac output produ ced only mild effects on renal parenchymal perfusion, the local compre ssing effect is likely to be the most important factor affecting renal hemodynamics during pneumoperitoneum.