The relationship between alcohol elimination rate and increasing blood alcohol concentration—Calculated from two consecutive blood specimens

Abstract

In the period 1991–2005, a blood–alcohol concentration (BAC) analysis was carried out at the Institute of forensic medicine in Novi Sad including 2023 two consecutive blood specimens using the Headspace Gas Chromatography method. Cases with no alcohol concentration values, as well as cases where blood samples were taken within 1 h after the criminal act, were not taken into consideration. Following this rule, 1198 cases were considered in this study and all samples were grouped in 29 ranges of BAC 1 of Δ BAC = 0.1 g/kg, starting from 0.1–0.19 g/kg to 2.9–2.99 g/kg of absolute alcohol. Gathered results and elimination curve differ from the zero-order model of elimination proposed by Widmark and point to an elimination process similar to a well-known Michaelis-Menten elimination kinetics model and its variants. Results reported in this study show dependence of alcohol elimination rate ( β-slope) and BAC value. The analysis of β 60-slope versus BAC shows that a correlation between β 60 ( y) and BAC ( x) has a logarithmic trend line. The value of alcohol elimination rate shows a slight increment with increase of BAC alcohol, with the mean value of β 60 = 0.221 ± 0.075 g/kg. Differences in values of β 60 among consecutive intervals of Δ BAC = 0.1 g/kg are not significant ( p > 0.05). When obtained samples were grouped into ranges of 0.5 g/kg each in these intervals β 60 had the following values by range: 0.1–0.49 g/kg = 0.139 g/kg ± 0.035; 0.5–0.99 g/kg = 0.184 g/kg ± 0.043; 1–1.49 g/kg = 0.213 g/kg ± 0.052; 1.5–1.99 g/kg = 0.239 g/kg ± 0.058; 2–2.49 g/kg = 0.265 g/kg ± 0.073; 2.5–2.99 g/kg = 0.306 g/kg ± 0.096. Differences in values of beta slope among consecutive intervals of Δ BAC = 0.5 g/kg are significant ( p < 0.01). The elimination curve in the BAC interval 0.5–2.5 g/kg has a linear trend, while beta-slope ( y)/BAC ( x) correlation is given as β 60 = 0.15 g/kg + (0.05 g/kg × BAC). Retrograde calculation of the blood alcohol concentration in tempore criminis (BAC tc) based on the determined alcohol concentration in the blood specimen (BAC t ) shows a statistically significant difference between BAC tc calculated using a standard zero-order model versus corrected methodology. The higher the BAC t and the longer the calculation time, the greater and statistically more significant ( p < 0.01) is the difference between the calculated values of BAC tc.