Serum osmolality in acute intoxication: a prospective clinical study.

The authors prospectively performed simultaneous determinations of serum delta osmolality (delta-Osm), enzymic (alcohol dehydrogenase [ADH]) quantitation of serum ethanol (EtOH), and urine drug screens on 339 acutely intoxicated patients. In addition, the authors established reference ranges for measured and calculated serum osmolalities in a group of 55 healthy volunteers. The authors determined the clinical utility of the combined delta-Osm/ADH procedure for detecting the presence of EtOH or other low molecular weight (Mr) volatiles. In the reference population, the measured osmolality (M-Osm) and calculated osmolality (C-Osm) was 285.1 +/- 4.3 (SD) mOsm/kg and 287.4 +/- 5.1 (SD) mOsm/kg, respectively. The correlation between delta-OsM and serum EtOH was 0.968 in 151 patients in whom EtOH was detected. The presence of drugs in 67 (44%) patients or absence of drugs in 84 (55.6%) patients was shown to have no significant effect on the delta-Osm. The delta-Osm/ADH method failed to detect a volatile other than EtOH in only two cases (0.6%) or in addition to EtOH in three cases (0.9%). The concentrations of these volatiles were not clinically significant. The sensitivity for detecting EtOH by means of the delta-Osm calculation was 98.1% with a specificity of 98.2%. A disparity (delta-Osm greater than 10 mOsm/kg) between delta-Osm and the EtOH determination suggested a volatile other than EtOH in five cases (1.5%), which was confirmed by head-space gas chromatographic (GC-HS) analysis. A volatile in addition to EtOH in seven cases (2.1%) was suggested but not confirmed by GC-HS analysis. The delta-Osm/ADH procedure provides an efficient, rapid, and readily available method to evaluate the acutely intoxicated patient for the presence of EtOH and/or other low Mr volatiles.