Serum formate concentrations in methanol intoxication as a criterion for hemodialysis

To evaluate the utility of serum formate concentrations, four patients were studied after ingestion of a methanolic copying fluid. All patients were initially intoxicated. Twelve to twenty-four hours later, signs and symptoms included nausea, abdominal pain, hypokalemia, acidosis (three patients), and pathologic ocular findings (two patients). All patients were treated with ethanol and folate. The two patients with ocular signs and acidosis had high serum formate concentrations (75 and 55 mg/dL, respectively). One of the two patients had a high methanol concentration (222 mg/dL) and required hemodialysis; the other patient did not (methanol concentration, 24 mg/dL). In the other two patients without ocular signs, initial formate concentrations were undetectable (limit of detection, 0.5 mg/dL); however, one patient required hemodialysis because the methanol concentration was 72 mg/dL. Formate is the mediator of ocular injury and acidosis. In these patients formate concentrations correlated with the clinical condition but methanol concentrations did not.