Potential for postmortem formation of ethanol in vitreous humor

Interpretation of ethanol results in postmortem blood samples has well-known limitations. After death, ethanol can form in the blood if sufficient glucose and microorganisms are present to facilitate the fermentation process. The potential for postmortem formation of ethanol has led to the widespread practice of verifying blood ethanol concentrations in a secondary matrix, typically vitreous humor when available. This study examined underlying trends and causes of postmortem ethanol formation in vitreous humor. Postmortem casework from 1 January 2022 to 31 December 2024 was investigated for cases where ethanol was reported in vitreous humor but not detected in a paired blood sample. Volatile analysis was performed by headspace gas chromatography on a dual column with a flame ionization detector. Ethanol, methanol, isopropanol, and acetone were screened in both blood and vitreous humor at reporting limits of 10, 10, 5.0, and 5.0 mg/dL, respectively. During this timeframe, 858 cases were identified with vitreous humor ethanol concentrations ranging from 10 to 624 mg/dL (mean 49 mg/dL, median 20 mg/dL). Of those identified, 683 cases (79%) had low-range vitreous ethanol concentrations (10-49 mg/dL). Possible biomarkers of ketoacidosis were also assessed in the 858 cases, with 464 cases (54%) reporting positive acetone and/or isopropanol. Additionally, elevated levels of beta-hydroxybutyric acid (BHB) (≥ 250 µg/mL) in either the blood or vitreous humor, were detected in 92% of cases (n = 140) tested for BHB; elevated levels of glucose (≥ 200 mg/dL) in vitreous humor were detected in 37% of cases (n = 458) tested for glucose. The results of this study highlight the importance of testing multiple matrices for ethanol in postmortem casework and the potential for postmortem ethanol formation in unpreserved specimens.