EXCESS SERUM OSMOLALITY GAP AFTER INGESTION OF METHANOL - A METHODOLOGY ASSOCIATED PHENOMENON

A patient intentionally ingested an unknown amount of methanol and was admitted to the hospital 6 h later. On admission, the methanol concen tration in blood was estimated as similar to 134 mmol/L, based on the calculation of the osmolal gap. Intravenous ethanol administration and hemodialysis were promptly started. During hemodialysis, several bloo d samples were collected for determination of methanol and ethanol con centrations. Initially, we used gas chromatography with split-mode inj ection of pretreated serum samples; however, methanol concentrations t urned out to be significantly lower than expected, based on calculated osmolal gap values. Because no explanation for the excess serum osmol al gap was apparent, we reanalyzed samples, using head-space gas chrom atography. The methanol concentrations measured were significantly hig her and osmolal gap values were no longer excessive.