The role of intra-abdominal pressure on splanchnic and pulmonary hemodynamic and metabolic changes during carbon dioxide pneumoperitoneum

Background and Methods: To find an intra-abdominal pressure (IAP) range for laparoscopic procedures that elicits only moderate splanchnic and pulmonar y hemodynamic and metabolic changes, including hepatic and intestinal tissu e pH and superficial hepatic blood flow, we installed an IAP of 7 and 14 mm Hg each for 30 minutes in 10 healthy pigs (30 +/- 4 kg). Results: In parallel with the increase of IAP, the mean transmural pulmonar y artery pressure increased (from 25 +/- 3 to 27 +/- 4 at 7 mm Hg IAP and 3 0 +/- 6 mm Hg at 14 mm Hg IAP, p < 0.05); the pulmonary artery-to-pulmonary capillary wedge pressure gradient also increased (from 17 +/- 2.7 to 21 +/ - 3 mm Hg at 7 mm Hg IAP and 24 +/- 4.2 mm Hg at 14 mm Hg IAP, p < 0.01), a nd the arterial oxygenation decreased (p < 0.005). Relevant changes at an I AP of 14 mm Hg were observed in right atrial pressure during inspiration (f rom 7 +/- 2 to 12 +/- 3 mm Hg, p < 0.0001) and in abdominal aortic flow (fr om 1.43 +/- 0.4 to 1.19 +/- 0.3 L/min, p < 0.01). However, transmural right atrial pressure and cardiac output remained essentially unchanged. Portal and hepatic venous pressure increased in parallel with the IAP (portal: fro m 12 a 3 to 17 a 3 at 7 mm Hg IAP and 22 +/- 3 mm Hg at 14 mm Hg IAP, p < 0 .01; hepatic venous: from 8 +/- 3 to 14 +/- 6 at 7 mm Hg IAP and 19 +/- 6 m m Hg at 14 mm Hg IAP, p < 0.005), but the transmural portal and hepatic ven ous pressures decreased (p < 0.01), indicating decreased venous filling. Po rtal flow was maintained at 7 mm Hg but decreased at 14 mm Hg from 474 +/- 199 to 395 +/- 175 mL/min (p < 0.01), whereas hepatic arterial Flow remaine d stable. Hepatic superficial blood flow decreased during insufflation and increased after desufflation. Tissue pH fell together with portal and hepat ic venous pH (intestinal: from 7.323 +/- 0.05 to 7.217 +/- 0.04; hepatic: f rom 7.259 +/- 0.04 to 7.125 +/- 0.06, both p < 0.01) at 14 mm Hg. Conclusion: The hemodynamic and metabolic derangement in the pulmonary and splanchnic compartments are dependent on the extent of carbon dioxide pneum operitoneum. The effect of low IAP (7 mm Hg) on splanchnic perfusion is min imal. However, higher IAPs (14 mm Hg) decrease portal and superficial hepat ic blood flow and hepatic and intestinal tissue pH.