Relationship between postmortem blood and vitreous humor ethanol levels.

The relationship between the blood to vitreous humor ethanol ratios (B/V) and the corresponding urine to blood ethanol ratios (U/B) of 200 postmortem cases were found to be bimodal in nature. Using the U/B ratio of 1.20 as a demarcation below which early absorption prevails, the results in the early absorption phase gave an average B/V ratio of 1.29, a range from 0.71 to 3.71, and a relatively large standard deviation of 0.57, whereas the results in the other phases (late absorption and elimination) gave an average B/V ratio of 0.89, a spread from 0.32 to 1.28, and a standard deviation of 0.19. It would appear that the blood ethanol levels can be estimated using B = 1.29 V for early absorption phase cases and B = 0.89 V for cases in subsequent phases. The former relationship would underestimate the blood ethanol levels in cases of very early absorption phase and the later overestimate the levels of late elimination cases. The ethanol distribution results in cases of fatal road traffic accidents and suicides by falling, in which 69% of the deceased sustained some form of head injury, were found to be similar to those of other postmortem cases. The observations reflect that vitreous humor, being reasonably protected, is likely to survive certain traumatic deaths and be available for postmortem ethanol investigation. The U/B ethanol ratios recorded in this work had an average of 1.29, a range from 0.19 to 5.19, and a standard deviation of 0.48.