A post-mortem blood alcohol concentration (BAC) of 120 mg/dL is reported. The forensic pathologist notes that the gastric mucosa shows submucosal haemorrhages and hyperaemia but the liver shows no fatty change. In post-mortem toxicology, which major confounding factor must be considered when interpreting blood ethanol levels?
- A Post-mortem redistribution and post-mortem synthesis of ethanol by microorganisms ✓
- B Haemolysis causing falsely low ethanol levels
- C Isopropanol formation from decomposition products
- D Ethanol binding to albumin reducing free plasma concentration
Explanation
Post-mortem blood alcohol levels are notoriously unreliable due to two competing processes: (1) post-mortem redistribution — ethanol in vitreous humour and stomach diffuses into adjacent blood compartments; central blood (cardiac/subclavian) shows the greatest artefactual elevation over peripheral blood (femoral vein), and (2) post-mortem synthesis by fermentation — microorganisms (Candida, Enterobacteriaceae) in decomposing bodies generate endogenous ethanol from glucose, yielding BAC values as high as 300 mg/dL even in non-drinkers. Vitreous humour ethanol is considered more reliable as it is less susceptible to both redistribution and fermentation due to anatomical isolation.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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Written and medically reviewed by the StethoPrep medical team.