Potential toxicity from prolonged anesthesia: a case report of a thirty-hour anesthetic

Selection of anesthetics for prolonged administration must include consideration of potential toxicity resulting from extended exposure. This report deals with a patient undergoing a 30-hour anesthetic that included nitrous oxide (N2O) and isoflurane (9.7 MAC-hours). Serial serum inorganic fluoride levels obtained in the perioperative period demonstrated a peak fluoride level of 12.6 mumols occurring 27 hours after isoflurane was discontinued. Although higher than previously reported fluoride levels following isoflurane anesthesia in healthy adults (4 mumols), the current results are below those levels associated with renal abnormalities after prolonged enflurane anesthesia (34 mumols). In addition to outlining basic care guidelines for patients undergoing a prolonged anesthetic, this report discusses potential toxicity from prolonged exposure to both N2O and isoflurane. It concludes that isoflurane can be tolerated in doses up to 10 MAC-hours without fluoride toxicity but cautions against the use of N2O for periods longer than 24 hours.