Effects of sevoflurane anesthesia on plasma inorganic fluoride concentrations during and after cardiac surgery

Sevoflurane metabolism results in the production of inorganic fluoride, which is known to be nephrotoxic. Since marked changes in body temperature and hemodynamics in cardiac surgery affect sevoflurane metabolism, plasma inorganic fluoride concentrations may differ in this situation compared with other types of surgery. We therefore measured plasma inorganic fluoride concentrations during and after sevoflurane anesthesia in patients undergoing cardiac surgery.

Sixteen patients undergoing coronary artery bypass grafting or valve replacement were premedicated with 5-10 mg midazolam and 0.5 mg scopolamine injected intramuscularly. Anesthesia was induced with 5-10 mg midazolam, 0.5-1 mg fentanyl, and 0.12-0.15 mg.kg(-1) vecuronium. Following tracheal intubation, anesthesia was maintained with oxygen, sevoflurane, and fentanyl. At the onset of cardiopulmonary bypass (CPB), sevoflurane was discontinued, and additional fentanyl, midazolam, and pancuronium were administered. Plasma inorganic fluoride concentrations were measured before anesthesia, immediately before and after CPB, and at 0, 2, 6, 12, 24, and 48 h after anesthesia.

The individual maximum plasma inorganic fluoride concentration was 19.2 +/- 7.2 micromol.l(-1) (mean +/- SD; range, 9.2-36.7). The mean plasma inorganic fluoride concentrations increased during anesthesia, but the rate of increase decreased after the initiation of CPB. Concentrations peaked at 2 h after anesthesia and decreased thereafter. The concentrations in three cases continued to increase 2 h after anesthesia.

The plasma inorganic fluoride concentrations observed in patients undergoing cardiac surgery were below nephrotoxic levels. However, the decrease in mean fluoride concentration after anesthesia was slower than that in the previous study in general surgical patients.