Formate Concentrations in Plasma from Patients Poisoned with Methanol

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Abstract
Formate and methanol were quantified in blood samples from 11 untreated methanol-poisoned subjects. The range for whole blood methanol concentrations was 0-137 mmol/l and for plasma formate concentrations 0.4-17.1 mmol/l. Simultaneously determined acid-base status and serum electrolyte concentrations allowed assessment of the relative importance of formate accumulation for acidosis. The plasma formate concentration was highly correlated to the calculated anion gap (r = 0.833), the bicarbonate concentration (r = -0.852) and the negative base excess (r = 0.865). The accumulation of formate fully accounted for the increase in the anion gap and the fall in plasma bicarbonate; the negative base excess values were .apprx. 22% higher than the plasma formate concentration. Formate accumulation was the main or only reason for acidosis in the early, uncomplicated stages of methanol poisoning. Lactate may have appeared at more advanced stages.