Effect of intravascular volume expansion on renal function during prolonged CO2 pneumoperitoneum

Abstract

Objective: To evaluate whether intravascular volume expansion would improve renal blood flow and function during prolonged CO2 pneumoperitoneum.

Summary background data: Although laparoscopic living donor nephrectomies have a considerably reduced risk of complications for the donors, significant concerns exist regarding procurement of a kidney in the altered physiologic environment of CO2 pneumoperitoneum. Recent studies have documented adverse effects of CO2 pneumoperitoneum on renal hemodynamics.

Methods: Renal and systemic hemodynamics and renal histology were studied in a porcine CO2 pneumoperitoneum model. After placement of a pulmonary artery catheter, carotid arterial line, Foley catheter, and renal artery ultrasonic flow probe, CO2 pneumoperitoneum (15 mmHg) was maintained for 4 hours. Pigs were randomized into three intravascular fluid protocol groups: euvolemic (3 mLkg/hour isotonic crystalloid), hypervolemic (15 mL/kg/hour isotonic crystalloid), or hypertonic (3 mL/kg/hour isotonic crystalloid plus 1.2 mL/kg/hour 7.5% NaCl).

Results: In the euvolemic group, prolonged CO2 pneumoperitoneum caused decreased renal blood flow, oliguria, and impaired creatinine clearance. Both isotonic and hypertonic volume expansions reversed the changes in renal blood flow and urine output, but impaired creatinine clearance persisted.

Conclusions: Intravascular volume expansion alleviates the effects of CO2 pneumoperitoneum on renal hemodynamics in a porcine model. Hypertonic saline (7.5% NaCl) solution may maximize renal blood flow in prolonged pneumoperitoneum, but it does not completely prevent renal dysfunction in this setting. This study suggests that routine intraoperative volume expansion is important during laparoscopic live donor nephrectomy.

Figure 1. The euvolemic group demonstrated a progressive and significant decrease in renal blood flow during the 4 hours of pneumoperitoneum that was prevented with isotonic volume expansion. Hypertonic volume expansion using 2,400 mOsm NaCl solution initially enhanced renal blood flow (P = .02 vs. baseline).

Figure 2. Pneumoperitoneum resulted in significant oliguria in the euvolemic group. Both isotonic and hypertonic saline volume expansion reversed pneumoperitoneum-induced oliguria (A). All three groups showed a marked decrease in creatinine clearance associated with pneumoperitoneum (B). However, these changes were significant only in the euvolemic and hypertonic groups (P < .05 vs. baseline).

Figure 3. Progressive tachycardia was observed throughout pneumoperitoneum in the euvolemic group, consistent with a simulated hypovolemic state (A). The euvolemic animals showed no decrease in cardiac index, presumably secondary to the compensatory tachycardia seen above (B). The hypertonic group did show a significant increase in cardiac index at 1 hour (P < .01 vs. baseline); otherwise, no significant changes were observed.

Figure 4. All groups demonstrated an increase in mean arterial pressure at 1 hour (P < .01) compared with baseline. However, there were no differences between study groups throughout the pneumoperitoneum period (A). The isotonic volume expansion demonstrated appropriate and significant increases in pulmonary artery wedge pressure. Neither the euvolemic nor the hypertonic saline group showed any change in pulmonary artery wedge pressure (B).

Figure 5. A pattern of progressive and significant increase in serum electrolyte concentration in the euvolemic group, with essentially no change in either volume-expanded group, was observed for sodium, potassium, chloride, and bicarbonate (P < .001 for Na⁺ and K⁺ vs. baseline;P < .01 for Cl⁻ and HCO⁻³ vs. baseline).