INTERPRETATION OF LOW POSTMORTEM CONCENTRATIONS OF ETHANOL

The interpretation of postmortem blood ethanol concentrations (BAC), e specially those less than 0.05 g/dL can be complicated by postmortem e thanol formation. One method used by the toxicologist to respond to th is possibility is to analyze multiple specimens for ethanol. Two usefu l specimens to analyze are vitreous humor and urine, because they are less susceptible to the putrefaction process. A negative vitreous humo r and/or urine ethanol would suggest that the measured ethanol resulte d from postmortem formation. Data were collected from the Office of th e Chief Medical Examiner, State of Maryland and the Armed Forces Insti tute of Pathology on blood specimens with ethanol concentrations less than 0.05 g/dL to develop a reasonable threshold for interpretation in the absence of other specimens. A total of 381 cases with a BAC betwe en 0.01 and 0.04 g/dL were studied over a 2 year period. Urine and vit reous humor specimens were tested where available. At a BAC of 0.01 g/ dL, 54% of the cases were associated with a positive vitreous humor an d/or urine ethanol concentration. This percentage increased to 63% whe n BAC equals 0.02 g/dL. Seventy-three percent and 92% of the cases had a positive alternate specimen if the BAC was 0.03 g/dL and 0.04 g/dL, respectively. In addition, 90% of the cases where both vitreous humor and urine were analyzed showed consistent results, that is both speci mens were positive or negative. This suggests that in the absence of a dditional information, a BAC of 0.04 g/dL or higher probably resulted from ethanol consumption.