Effect of temperature and preservative on neo-ethanol formation in postmortem whole blood samples

Abstract

Objective: To determine the association of temperature, time duration, and preservatives with ethanol neo-genesis in postmortem whole blood samples. Study Design: Observational cross-sectional study. Place and Duration of Study: Department of Chemical Pathology and Toxicology, Armed Forces Institute of Pathology, Rawalpindi, in collaboration with Combined Military Hospital, Rawalpindi from August 2020 to January 2021. Methodology: Whole blood samples were obtained from cardiac chamber of an autopsy case with aseptic measures and were drawn into six tubes (3 x EDTA tubes and 3 x NaF tubes). These six tubes were stored at 4°C, 25°C, and 37°C. All samples were analysed along with internal standard, on head space gas-chromatography on Day-0, Day-07, Day-14, Day-21, and Day-28 of sampling. Results: A total of 60 samples out of 10 autopsies, were analysed. Blood alcohol concentrations of all samples were negative on 1st day (Day-0) of analysis. Samples stored at 4°C did not produce any ethanol at any day of analysis, regardless of preservatives used. Neo-ethanol levels of blood samples stored in EDTA preservative were significantly raised (p <0.001) as compared to samples stored in NaF preservative. Samples stored at 37°C showed significant increase in neo-ethanol concentration (p <0.001) in comparison with samples stored at 4°C and 25°C. Neo-ethanol levels increased with duration of storage till 14th day of analysis. Conclusion: Sodium fluoride (NaF) should be used as preservative to avoid ethanol neo-genesis during storage and transportation of blood samples for alcohol analysis. Cold chain maintenance is of pivotal importance to exclude false positive blood alcohol results.