Renal oxalosis and azotemia after methoxyflurane anesthesia

Renal biopsies performed in seven patients after methoxyflurane anesthesia followed by renal failure disclosed a striking degree of oxalate precipitation. The extent of the precipitation paralleled, but could not fully account for, the corresponding degree of azotemia. Urinary oxalate, determined in six patients, was elevated (96 to 480 mg per 24 hours). Methoxyflurane thus appears to cause secondary hyperoxaluria, and intrarenal oxalate precipitation may occur when renal function is compromised for any reason during or immediately after surgery. Oxalate deposition, when extensive, may contribute to the severity of the renal failure.