False hyperchloremia in bromism.

Plasma chloride concentration measured by an ion-specific electrode can be interfered by other ions. The authors experienced a case of phantom limb pain with a marked hyperchloremia (251 mEq. l(-1)) which was measured by the ion-specific electrode method. The patient was diagnosed as bromide intoxication due to chronic ingestion of analgesic tablets which contain bromvalerylurea. A toxic level of plasma bromide concentration supported the diagnosis. Elevated plasma chloride and bromide concentrations were normalized in three weeks after discontinuation of the analgesic intake. Laboratory study revealed that fluoride ion did not affect chloride concentration measured by an ion-specific electrode. Bromide and iodide ions, however, interfered with the electrode and produced a large overestimation of chloride concentration. Hyperchloremia should be interpreted carefully when chloride was measured by an ion-specific electrode method.