Symptomatic hyponatraemia due to inappropriate antidiuretic hormone secretion following minor surgery

A rare case of the syndrome of inappropriate antidiuretic hormone secretion occurring after minor surgery is presented. A ten-year-old, previously healthy boy underwent general anaesthesia for detorsion and right orchiopexy. Throughout the operations, which lasted for one hour, he received 120 ml Ringer's lactate solution. The immediate postoperative period was uneventful. Twenty-two hours postoperatively he was found unconscious with generalized tonic-clonic seizures. Simultaneously obtained serum sodium concentration (121 mEq.L-1) serum osmolarity (265 mEq.L-1), urine sodium concentration (87 mEq.L-1) and urine osmolarity (525 mEq.L-1) suggested inappropriate antidiuretic hormone secretion which was confirmed by an elevated serum arginine-vasopressin (AVP) level of 14.5 pcg.ml-1 (normal 1-5 pcg.ml-1) measured by radioimmune assay. He was treated with a single iv dose of 30 mg furosemide and fluid restriction, which produced a gradual increase of his serum sodium concentration to normal within two days. He was well during the remainder of his hospitalization.