The increase in urinary alanine aminopeptidase excretion associated with enflurane anesthesia is increased further by aminoglycosides

Urinary excretion of alanine aminopeptidase (AAP) is an extremely sensitive indicator of drug-induced renal tubular damage. The urinary excretion of AAP was determined in patients after enflurane anesthesia with or without concurrent aminoglycoside administration to determine if enflurane enhances the nephrotoxic potential of aminoglycosides. Twenty-two patients with normal renal function were studied. Ten received enflurane alone, eight received enflurane plus gentamicin or tobramycin, and four patients who underwent nitrous oxide and narcotic anesthesia were the control group. Preoperative values ranged from 1010 to 2461 μU/24 hour. Urinary AAP excretion increased significantly in both enflurane groups 2 days postoperatively (P < 0.025). Patients who received both enflurane and aminoglycosides had significantly greater urinary AAP excretion on postoperative day 2 than did patients given enflurane alone: 21,342 ± 4074 μU/24 hour and 6336 ± 1496 μU/24 hour, respectively (mean ± SEM, P < 0.005). There was no change in AAP excretion in the control group compared to baseline; on day 3 AAP was 1412 ± 710 μU/24 hour. No changes in blood urea nitrogen or serum creatinine levels were observed. These data suggest that enflurane increases the renal tubular effects of aminoglycosides, possibly increasing the risk of aminoglycoside renal toxicity.