SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

P47
INTERPRETATION OF POSTMORTEM ALCOHOL CONCENTRATIONS: A CASE STUDY
Curtis Caylor, B.S.,* Ruth Luthi, B.S. and Sarah Kerrigan, Ph.D.
New Mexico Department of Health, Scientific Laboratory Division, Toxicology Bureau, PO Box 4700,
Albuquerque, NM 87196-4700.
Our laboratory performs drug and alcohol testing on approximately 2800 medical examiner cases each
year. The preferred specimen for alcohol analysis was blood, and until recently, additional specimens were
not routinely tested unless the submitting agency requested additional analyses. A new policy required that
all positive blood alcohol measurements in postmortem cases were confirmed using an alternative
specimen. Although this resulted in a 43% increase in alcohol casework, these analyses provided important
interpretive information and also identified a number of unusual results that would not have been otherwise
identified.
Postmortem blood and vitreous alcohol concentrations were determined in a total of 295 alcohol-positive
cases. The vitreous alcohol concentration (V AC) exceeded the blood alcohol concentration (BAC) in 209
cases (71%). Blood alcohol concentrations exceeded vitreous concentrations in 81 cases (27%) and the
concentrations were equivalent in 5 cases (5%). Samples that were negative in both specimens were
excluded, as were cases where the confirmatory test was performed using a specimen other than vitreous
fluid (e.g. urine, liver, blood from an alternative source). In casework where the VAC>BAC, linear
regression analysis indicated an R2 value of 0.958 (n=295) and a V AC approximately 18% higher than the
BAC. The VACIBAC ratio was more variable at lower BACs «0.1 glIOOmL). Although VACIBAC ratios
were more consistent at concentrations of0.1 gllOOmL and above, the overall ratio ranged from 1.01-2.20.
Ofthe 81 cases where the BAC>VAC, a total of24 cases indicated no vitreous alcohol. The range ofblood
alcohol concentrations among these cases was widely variable (0.01 to 0.30 glIOOmL). All analyses were
conducted using dual column gas chromatography with flame ionization detection (GC-FID) with a
reporting limit of0.0 1 g/l00mL for postmortem samples.
A series of case studies are used to demonstrate postmortem interpretive issues and the benefits associated
with multiple specimen analysis. Cases include in-situ contamination of specimens due to trauma,
postmortem production of ethanol, death during the absorptive phase among others. Actual case studies
involving other volatile organic compounds are also discussed including isopropanol and acetone from
endogenous and exogenous sources. These cases studies highlight the importance of analyzing multiple
specimens in postmortem casework.
Keywords: ethanol, postmortem, blood, vitreous fluid
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