Effect of Intravascular Volume Expansion on Renal Function During Prolonged CO2 Pneumoperitoneum

Living donor renal transplantation has achieved a high level of acceptance from the general public and is the ideal renal replacement therapy for those with end-stage renal disease. Living donor nephrectomy has been proven safe and is associated with minimal complications and a negligible death rate. 1 The recipient benefits of living donor renal transplantation are multiple: superior patient and graft survival, no prolonged waiting time, decreased incidence of delayed allograft function, and a shorter hospital stay. 2 These superior results and the current shortage of cadaver kidneys provide an incentive to increase the frequency of living donor transplantation. However, a significant disincentive is the invasive nature of the donor nephrectomy and its relatively long postoperative recovery period. Recent reports of laparoscopically assisted living donor nephrectomy have shown that this less invasive approach results in reduced postoperative pain, a shorter hospital stay, and a more rapid return to the work for the donor. 3–6 In addition, decreased donor discomfort and a shorter convalescence have resulted in a substantially increased rate of consent to living donation and may help to alleviate the ongoing transplant organ shortage. A critical analysis with regard to the rate of donor complications and death and the status of the procured kidney is needed before laparoscopic living donor nephrectomy can be fully accepted by the transplant community. In particular, the excellent immediate renal allograft function usually obtained with standard open donor nephrectomy must be reproduced with the laparoscopic technique. A major concern regarding laparoscopic living donor nephrectomy is compelling evidence demonstrating that the prolonged CO2 pneumoperitoneum during laparoscopy decreases renal blood flow and contributes to postoperative renal dysfunction in the recipient. 7,8 The combination of prolonged CO2 pneumoperitoneum and an ischemic period during organ procurement may expose these grafts to an increased risk of early posttransplant renal dysfunction. The purported adverse effects of pneumoperitoneum on renal function have been supported by the initial reports of laparoscopic donor nephrectomy, which suggest either a decrease in urine output during the donor operation or early renal allograft dysfunction. 3,5,6 Gaseous pneumoperitoneum has been found to induce significant systemic hemodynamic alterations that appear to depend on the type of gas, the magnitude of intraabdominal pressure, the baseline hemodynamic function, and intravascular volume status. The cardiovascular effects most frequently associated with CO2 pneumoperitoneum are tachycardia, increased total peripheral resistance, and decreased stroke volume. 8–10 Some investigators have also reported a decrease in cardiac output, but previous studies from our laboratory showed that cardiac output decreased only in hypovolemic animals. 11,12 The effects of intravascular volume expansion on renal blood flow and function during prolonged CO2 pneumoperitoneum remain unknown. Hypertonic saline volume expansion has been shown to improve renal blood flow in other animal models of hypovolemia. 13,14 The use of hypertonic saline solution for volume expansion may provide protection to the kidneys without significant fluid overload to the donor. The objectives of this study were to test the hypothesis that intravascular volume expansion would improve renal blood flow and function during prolonged CO2 pneumoperitoneum, and to compare the beneficial effects of volume expansion on renal hemodynamics using isotonic (normal saline) and hypertonic (2400 mOsm NaCl) solutions.