RENAL CONCENTRATING FUNCTION WITH PROLONGED SEVOFLURANE OR ENFLURANE ANESTHESIA IN VOLUNTEERS

Background: Sevoflurane, a new inhalational anesthetic, is biotransformed, producing peak plasma inorganic fluoride concentrations that may exceed 50 mu M. We evaluated plasma inorganic fluoride concentrations with prolonged (> 9 MACh) sevoflurane or enflurane anesthesia in volunteers and compared renal concentrating function with desmopressin testing 1 and 5 days after anesthesia. Methods: Fourteen healthy male volunteers received either enflurane or sevoflurane (1-1.2 MAC) for more than 9 comb. Each volunteer was administered three tests of renal concentrating function, with intranasal desmopressin and urine collections performed 1 week before anesthesia and 1 and 5 days after anesthesia. Venous blood samples were obtained for plasma fluoride concentrations during and after anesthesia. Creatinine clearance was determined by 24-h urine collections 7 days before and 4 days after anesthesia. Urine samples were obtained before and 1, 2, and 5 days after anesthesia for determination of n-acetyl-beta-glucosaminidase and creatinine concentrations. Results: Prolonged sevoflurane anesthesia (9.5 MAC-h) did not impair renal concentrating function on day 1 or 5 postanesthesia, as determined by desmopressin testing. Maximal urinary osmolality on day 1 postanesthesia was decreased (<800 mOsm/kg) in two of seven enflurane-anesthetized volunteers; however, mean results did not differ from the those of the sevoflurane group. Mean peak plasma fluoride ion concentrations were 23+/-1 mu M 6 h postanesthesia for enflurane and 47+/-3 mu M at the end of anesthesia for sevoflurane (P<0.01). There were no changes in creatinine clearance or urinary n-acetyl-beta-glucosaminidase concentration in either anesthetic group. Discussion: Prolonged sevoflurane anesthesia did not impair renal concentrating function, as evaluated with desmopressin testing 1 and 5 days postanesthesia in healthy volunteers. Although with prolonged enflurane anesthesia, mean maximal osmolality values on day 1 postanesthesia did not differ from sevoflurane values, there was evidence in two volunteers at this time point of impairment in renal concentrating function, which normalized 5 days postanesthesia. These results occurred despite a higher peak plasma fluoride ion concentration and greater total inorganic fluoride renal exposure with sevoflurane anesthesia.