WHAT CAUSES THE FALSELY ELEVATED CHLORIDE?
All of the current laboratory techniques for measurement of serum chloride concentration can potentially result in a falsely elevated value. However, the degree of pseudohyperchloremia will depend on the specific assay used for measurement. The ion-selective electrode method used by many common laboratory analyzers appears to have the greatest interference on chloride measurement in the presence of bromide. This is simply due to the molecular similarity of bromide and chloride.
Conversely, the coulometry method, often used as a reference standard, has the least interference of current laboratory methods.3 This is because coulometry does not completely rely on molecular structure to measure concentration; rather, it measures the amount of energy produced or consumed in an electrolysis reaction. Iodide, another halide compound, has also been described as a cause of pseudohyperchloremia, whereas fluoride does not seem to have significant interference.4
HOW ARE PATIENTS EXPOSED TO BROMIDE SALTS?
Bromide salts, specifically sodium bromide, are infrequently used to treat seizure disorders but are generally reserved for patients with epilepsy refractory to other, less toxic anticonvulsant medications. During the era when bromide salts were more commonly used to treat epilepsy, bromide intoxication, or bromism, was frequently observed.
Bromism may manifest as a constellation of nonspecific neurologic and psychiatric symptoms. These most commonly include headache, weakness, agitation, confusion, and hallucinations. In more severe cases of bromism, stupor and coma may occur.3,5
Although bromide salts are no longer commonly prescribed, a number of products still contain brominated ingredients. Symptoms of bromide intoxication can occur with chronic use of a cough syrup containing dextromethorphan hydrobromide, as well as the brominated vegetable oils found in some soft drinks.5
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