Direct Visualization of Renal Hemodynamics Affected by Carbon Dioxide–induced Pneumoperitoneum

ObjectivesTo examine the direct renal hemodynamics during carbon dioxide pneumoperitoneum in both human and porcine models. Laparoscopic living donor nephrectomy has become widespread because of its minimally invasive nature. However, it has been clear that the renal hemodynamics and function are affected during carbon dioxide pneumoperitoneum.MethodsThe erythrocyte velocity in the cortical peritubular capillary (CPC) was monitored and measured during laparoscopic nephrectomy on human donors and laparoscopic partial nephrectomy on humans with renal cell carcinoma during carbon dioxide pneumoperitoneum (pressure of 8, 12, 15, 18, and 20 mm Hg). We used a direct imaging system of renal microcirculation by magnifying endoscopy, as previously described. We maintained the same pressure for 5 minutes. In the porcine model (6 pigs), we measured the erythrocyte velocity in the CPC using the same method during carbon dioxide pneumoperitoneum (pressure of 0, 5, 10, 15, 20, and 25 mm Hg).ResultsThe erythrocyte velocity in the renal artery did not change during increased carbon dioxide pneumoperitoneum. When the pneumoperitoneal pressure was 25 mm Hg, we found that >90% of the erythrocyte velocity in the CPC was nonflowing. In the human model, the erythrocyte velocity in the CPC decreased when the carbon dioxide pneumoperitoneum pressure was 12 mm Hg.ConclusionsThe erythrocyte velocity in the CPC decreased during carbon dioxide pneumoperitoneum in all kidneys in both the human and the porcine models. However, erythrocyte velocity in the renal artery did not change during carbon dioxide pneumoperitoneum. After stopping the pneumoperitoneum, the erythrocyte velocity in the CPC recovered immediately. The findings of our study have shown that the suitable carbon dioxide pneumoperitoneal pressure for renal microcirculation is <8 mm Hg for laparoscopic surgery.