Changes in urine osmolality and urine fluoride concentrations following methoxyflurane anaesthesia.

A study of 41 patients receiving methoxyflurane and 8 patients receiving halothane showed that on the first day after exposure to methoxyflurane there was a significant correlation between the reduction of urine osmolality and the dose of methoxyflurane. On the first and second days after exposure to methoxyflurane the patients who received a relatively large dose had significantly lower urine osmolality values than those who received a smaller dose. The patients who were exposed to large doses of methoxyflurane developed significantly decreased urine osmolality values on the second day after exposure compared with patients receiving halothane. In a study of 47 patients exposed to methoxyflurane a significant correlation was found between the dose of methoxyflurane and the urine fluoride concentration on the first and second days after exposure. These findings are taken as further evidence of a causal relationship between renal tubular dysfunction and the increased production of fluoride which follows methoxyflurane anaesthesia.