Effect of Pneumoperitoneum on Regional Hemodynamics

Increased IAP and the head-up position result in lower limb venous stasis.^{[96] [100] [114] [115]} Femoral vein blood flow decreases progressively with increasing IAP and no adaptation to the reduced femoral venous outflow occurs, even during prolonged procedures.^[115] These changes may predispose to the development of thromboembolic complications. Although cases of thromboembolism have been reported in the literature, their actual incidence does not seem to be increased by laparoscopy.^{[116] [117] [118] [119]}

The effect of CO₂ pneumoperitoneum on renal function has also been investigated.^{[120] [121] [122] [123]} Urine output, renal plasma flow, and glomerular filtration rate decrease to less than 50% of baseline values during laparoscopic cholecystectomy and are significantly lower than those during open cholecystectomy.^[120] Urine output significantly increases after desufflation.

Controversy persists with regard to the effect of CO₂ pneumoperitoneum on splanchnic and hepatic blood flow. A significant reduction was reported in animals^{[122] [124] [125]} and humans.^{[126] [127] [128] [129]} However, others have not observed any significant changes.^{[130] [131] [132] [133]} Blobner and coworkers,^[131] comparing CO₂ pneumoperitoneum and air pneumoperitoneum in pigs, observed a reduction in splanchnic blood flow during air pneumoperitoneum but not CO₂ pneumoperitoneum. They suggest that the direct splanchnic vasodilating effect of CO₂ may counteract the mechanical effect of increased IAP. The rarity of reports of mesenteric ischemia after laparoscopy^{[134] [135]} suggests that the effects of pneumoperitoneum on the splanchnic circulation are not clinically significant.

Cerebral blood flow velocity increases during CO₂ pneumoperitoneum in response to the increased PaCO₂ .^{[136] [137]} When normocarbia is maintained, pneumoperitoneum combined with the head-down position does not induce harmful changes in intracranial dynamics.^[138] Intracranial pressure nevertheless rises during CO₂ pneumoperitoneum independently of changes in PaCO₂ in pigs with preoperatively induced intracranial hypertension or normal intracranial pressure^{[139] [140] [141]} and in children with ventriculoperitoneal shunts. ^[142] Intraocular pressure is not affected by pneumoperitoneum in women with no preexisting eye disease.^[143] In an animal model of glaucoma, pneumoperitoneum only slightly increases intraocular pressure.^[144]