Serum fluoride ions and hepatorenal effect of prolonged low-flow sevoflurane anesthesia

Backgroung: Sevoflurane is partly degraded by carbon dioxide absorbents to compound A, whose concentration increases in the anesthesia circuit with low fresh gas flow. The nephrotoxic threshold of compound A in humans is uncertain, also there is a possible hepatotoxicity of compound A. Aim of this work is the assessment of the amount of free fluoride ions production with low and high flowsevoflurane, also comparison of the effects of prolonged low flow sevoflurane anesthesia on renal and hepatic functions with high flow sevoflurane. METHODS: Sixesty hospitalized patients undergoing elective prolonged ( 5 hours) orthopedic or plastic operations. All patients were ASA: I or II, there ages were between 18 – 50 Years. Patients had given fully informed written consent after the nature and purpose of the study had been fully explained. The systolic and diastolic blood pressures, heart rate were recorded throughout the procedure, Blood samples were collected intraoperatively (3 and 5 hours from induction) and at 6, 12 hours postoperatively for measuring serum inorganic fluoride. Also blood samples and 24 hours urine samples were collected 24, 48 and 72 hours postoperatively for measuring serum inorganic fluoride and for total bilirubin, Alkaline phosphates, AST, ALT., B.U.N., Serum creatinine, Lactate dehydrogenase, Prothrombin time. A 24 hours urine sample was collected from each patient for: Creatinine clearance, Urine albumin, Urine specific gravity, and other routine laboratory works were done. RESULTS: Regarding serum fluoride ions, renal and hepatic functions, no significant differences were detected between the two groups at the preoperative period (T0) or at any time in the post operative period. The changes of the serum fluoride ions through the whole study in each of the two groups were the same and were highly significant. Regarding renal functions in group I ; for serum creatinine, blood urea nitrogen, creatinine clearance and urine specific gravity, the changes were not significant, while for urine albumin the changes were highly significant. Regarding hepatic functions both groups had the same results, the changes of the serum A.ST, serum A.L.T, serum lactate dehydrogenase and total bilirubin through the whole study were highly significant, while the changes of the serum alkaline phosphatase and prothrombin time were not significant. Conclusion: We concluded that prolonged anesthesia with low flow sevoflurane has similar effects on hepatorenal functions as prolonged anesthesia with high flow sevoflurane.