Differences between the measured blood ethanol concentration and the estimated concentration by Widmark's equation in elderly persons

Abstract

BackgroundThe Widmark's equation (C [BAC]=A/p×r) is the most commonly used formula in legal medicine to estimate the blood alcohol concentration (BAC) from the amount of ingested ethanol and vice versa. Within a drinking experiment with a target BAC of 1.2g/kg, a 75-year-old participant reached a maximum BAC of 1.83g/kg and showed signs of severe ethanol intoxication, while the other nine subjects (age: 19–31 years) had BACs close to the target BAC. This incident brought up the question, if the Widmark's equation is an appropriate tool for aged persons. MethodsA drinking experiment with 50 elderly voluntary test persons (22 males, 28 females, mean age and range [males]: 69.7 years, 60–84 years, mean age and range [females]: 68.5 years, 61–78 years) was performed. The amount of ethanol leading to a BAC of 0.6g/kg was estimated individually using the Widmark's equation (used Widmark factors: 0.7 for males, 0.6 for females). After drinking, the blood ethanol concentrations were measured using headspace gas chromatography/flame ionization detection. ResultsThe measured maximum BACs of the elderly participants were significantly higher (α=0.01) than the target BAC (mean maximum BAC and range: 0.627g/kg, 0.3–0.81g/kg, for males: 0.616g/kg, 0.32–0.78g/kg, for females: 0.635g/kg, 0.3–0.81). The calculated Widmark factors showed a high coefficient of variation (for males: 0.7±0.138 [0.55–1.2, CV: 19.7%], for females 0.59±0.119 [0.46–1.08, CV: 20.2%]). ConclusionThe results demonstrate that BAC calculations by Widmark's equation in elderly individuals may be complicated by a high variation of Widmark factors. There is a tendency to an elevation of the actual BAC with increasing age.