Low-flow Sevoflurane Compared with Low-flow Isoflurane Anesthesia in Patients with Stable Renal Insufficiency

BACKGROUND: Sevoflurane is degraded to compound A (CpA) by carbon dioxide absorbents containing strong base. CpA is nephrotoxic in rats. Patient exposure to CpA is increased with low fresh gas flow rates, use of Baralyme, and high sevoflurane concentrations. CpA formation during low-flow and closed circuit sevoflurane anesthesia had no significant renal effects in surgical patients with normal renal function. Preexisting renal insufficiency is a risk factor for postoperative renal dysfunction. Although preexisting renal insufficiency is not affected by high-flow sevoflurane, the effect of low-flow sevoflurane in patients with renal insufficiency is unknown. METHODS: After obtaining institutional review board approval, 116 patients with a stable preoperative serum creatinine concentration 1.5 mg/dl or greater were assessable. Patients were randomized to receive either sevoflurane (n = 59, 0.8-2.5 vol%) or isoflurane (n = 57, 0.5-1.4 vol%) at a fresh gas flow rate of 1 l/min or less. Use of opioids was restricted to a minimum, and Baralyme was used to increase CpA exposure. Inspiratory and expiratory CpA concentrations were measured during anesthesia. Renal function (serum creatinine and blood urea nitrogen, urine protein and glucose, creatinine clearance) was measured preoperatively and 24 and 72 h after induction. RESULTS: Demographic patient data did not differ between groups. Patients received 3.1 +/- 2.4 minimum alveolar concentration-hours sevoflurane or 3.8 +/- 2.6 minimum alveolar concentration-hours isoflurane (mean +/- SD). Durations of low flow were 201.3 +/- 98.0 and 213.6 +/- 83.4 min, respectively. Maximum inspiratory CpA with sevoflurane was 18.9 +/- 7.6 ppm (mean +/- SD), resulting in an average total CpA exposure of 44.0 +/- 30.6 ppm/h. There were no statistically significant changes from baseline to 24- and 72-h values for serum creatinine or blood urea nitrogen, creatinine clearance, urine protein, and glucose, nor were there significant differences between both anesthetics. CONCLUSION: There were no statistically significant differences in measured parameters of renal function after low-flow sevoflurane anesthesia compared with isoflurane. These results suggest that low-flow sevoflurane anesthesia is as safe as low-flow isoflurane and does not alter kidney function in patients with preexisting renal disease.