Abstract
Re: Thierauf A, Kempf J, Eschbach J, Auwarter V, Weinmann W, Gnann H. A case of a distinct difference between the measured blood ethanol concentration and the concentration estimated by Widmark's equation. Med Sci Law 2013; 53: 96–99.
Thierauf et al. raise an interesting point in their case report of a 75-year-old man who consumed 281 mL of vodka (40% v/v alcohol) within an hour and obtained a peak blood alcohol concentration (BAC) of 1.83 g/kg rather than the calculated BAC (according to Widmark and Watson) of 1.2 g/kg. The authors suggest that the high BAC was due to age-related decrease in total body water. 1 Two other factors may also have contributed.
One is that the authors used a “resorption” (i.e. absorption) deficit of 20% and assumed, not unreasonably, that 20% of the alcohol consumed would not be absorbed. The absorption deficit is not employed in the classic Widmark or Watson equations and could result in a 20% higher BAC.
The other factor is that rapid drinking of a higher concentration alcoholic beverage such as vodka may cause an “overshooting” of BAC as the amount of alcohol absorbed into the blood initially is greater that can be distributed to rest of the body. 2 Redistribution is eventually re-established and results in a “diffusionssturz” or rapid drop in BAC. 3
The rapid rise in BAC is known to produce the severe symptoms of intoxication as shown by this subject. 4
The authors raise a valid and useful cautionary tale in this case report of the limitations of relying solely on Widmark or Watson's equations, without qualifications, to calculate BACs, especially for court purposes.