ABSTRACT
The fluoride ions resulting from metabolism are nephrotoxic at plasma concentrations of 50-90 µmol/L or greater. Methoxyflurane was withdrawn because of its high metabolism and generation of fluoride ions which are highly nephrotoxic (Figure 33.24). After methoxyflurane anaesthesia, some patients developed high-output renal failure which often went unnoticed because there was no oliguria. This occurred because inorganic fluoride ions produce resistance to the action of antidiuretic hormone (vasopressin) in the distal convoluted tubule of the kidney. This led to the concept of the maximum number of tolerable MAC hours of anaesthesia at a given MAC.
