Comparison of renal function under deliberate hypotension during epidural plus light-enflurane anesthesia and during enflurane anesthesia.

We compared the effects of deliberate hypotension induced with trimethaphan on renal function and renal tubular damage under combined epidural and light-enflurane anesthesia (epidural group) and enflurane anesthesia alone (enflurane group). The mean arterial blood pressure was maintained at 50-55 mm Hg for 2.5 h in both groups using continuous infusion of trimethaphan. The urine volume and free water clearance were significantly greater in the epidural group than in the enflurane group [1.8±1.8 (SD)vs 0.4±0.3 ml·kg-1·h-1 and 0.81±1.30vs -0.15±0.22 ml·min-1, respectively] (P<0.05). The creatinine clearance and fractional sodium excretion rate did not differ significantly between the two groups. Urinary excretion of norepinephrine was significantly less in the epidural group than in the enflurane group (P<0.05); however, epinephrine excretion did not differ. Urinary excretion ofN-acetyl-β-D-glucosaminidase was significantly less in the epidural group than in the enflurane, group (4.2±2.5vs 12.2±4.6 U·g-1 CR) (P<0.01). The plasma antidiuretic hormone concentration was significantly lower in the epidural group compared to the enflurene group (13±23vs 57±42 pg·ml-1) (P<0.05). No significant difference in plasma atrial natriuretic peptide concentration was found between the groups. We conclude that renal function during trimethaphan-induced hypotension is better maintained under epidural plus light-enflurane anesthesia than under enflurane anesthesia alone.