Four-day sedation using sevoflurane: fluoride and renal function

Introduction

Volatile anesthetics for sedation in the ICU are currently undergoing a revival, mainly due to the recent availability of a novel delivery system, the anesthetic conserving device (ACD). Cytochrome P450 metabolic degradation of isoflurane and sevoflurane leads to the generation of inorganic fluoride and hexafluoro isopropanol. Historically, data derived from methoxyfluorane defined a fluoride nephrotoxicity threshold of 50 μmol/l. Therefore, we investigated the feasibility and safety, focusing on kidney function, of 4-day sevoflurane-ACD sedation.

Methods

Approval of the State Ethics Committee was obtained. Visceral surgical patients either received sedation via sevoflurane-ACD (n = 20) or were intravenously sedated (sufentanil, propofol, n = 20). Serum fluoride, renal, liver, pulmonary, cardiovascular function and depth of sedation were measured.

Results

Serum fluoride concentrations increased significantly during sevoflurane-ACD sedation (Figure 1). Renal function parameters and urinary output did not indicate deterioration of kidney function. Catecholamine support and pulmonary function were not different between the groups at equivalent depths of sedation.

Figure 1

Conclusions

Inhalational sevoflurane sedation subsequently leads to a transient, marked increase of serum fluoride concentrations. The methoxyflurane fluoride nephrotoxicity threshold was largely surpassed without apparent deleterious effect on renal volume regulation and detoxification. The sedational use of the volatile anesthetic sevoflurane up to 4 days is safe and feasible.