A negative anion gap as a clue to diagnose bromide intoxication.

We report on a patient with bromide intoxication, presenting with confusion, disorientation, and auditory and visual hallucinations after taking a sedative medication containing bromide (mixture menopause; 15 ml containing 1 g potassium bromide) for 1 month. Blood chemistry showed a high chloride level (176 mEq/l) and a negative anion gap (-60 mEq/l). The spurious hyperchloremia was due to interference of chloride ion determination by the ion-selective electrode method with a high level of bromide in serum: 352 mg/dl (44 mEq/l). In this case the only striking abnormality which alerted the physician to the possibility of halide intoxication was the negative anion gap. Hence, a negative anion gap is an important clue which leads to the diagnosis of halide intoxication.