Acute impairments due to alcohol consumption
Alcohol is easily absorbed in the bloodstream. The direct effects on the central nervous system (brain, spinal cord and the nerves originating from it) are the most noticeable. In the first place alcohol depresses the central nervous system. This is to say that after having consumed low quantities of alcohol, social inhibition starts to get less stringent and one begins to act and feel more emotional. However, cognitive, visual, and motor functions also begin to deteriorate after small quantities of alcohol have been consumed. Even with BAC as low as 0.3 g/l, most people can divide their attention less adequately and are less vigilant than without alcohol. With BAC just above 0.5 g/l, most people also start to get perception problems; start to perform less well on cognitive tasks and tracking tasks. Also reaction times get longer. Motor impairment can be observed in most people with a BAC of 1.5 g/l and higher. Especially on young people, alcohol has a strong motivational and emotional impact. They get more euphoric, more impulsive and start to show off with more risk-taking behavior. After consuming large quantities of alcohol people can become aggressive. High doses of alcohol lead to alcohol poisoning which can cause brain damage and death. There are not only acute effects because of brain dysfunctions due to alcohol, but also other parts of the body get affected. An important acute effect in relation to road safety is that the muscles weaken. This means that in case of a crash, the injuries will be more severe if a road user has consumed alcohol.
How strong the acute impacts of alcohol are depends on weight and sex. If a heavy but not fat man consumes the same quantity of alcohol as a light woman (and both are no regular drinkers), the man will be slightly less adversely affected than the woman. The reason for this is that alcohol dilutes itself in the water volume of the body and muscle tissue contains more water than fat tissue. On average men have more muscle and less fat than women.
Absorption of alcohol from a healthy adult body occurs at an average rate of about 8 grams per hour. This means that it takes about one hour and thirty minutes for one consumed glass of wine (12%) or one consumed glass (275 ml) of beer (5%) to be absorbed.
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The maximum BAC-level a person has after having consumed alcohol can roughly be estimated with the help of 'Widmark formula'. This formula can be given as follows:
BAC-level (in g/l)= (Alcohol dose in grams) / (Body weight in kilograms x R)
R = the whole body alcohol distribution ratio:
R= 0.55 for females
R= 0.68 for males
Example: A man that weights 80 kilograms has consumed three cans of beer in a short period of time. Each beer can contains 33 cl beer and the volume percentage of alcohol in that beer is 5%. What would his maximum BAC-level be?
Calculation: The man has consumed (3x33cL) 1 L beer. As the alcohol concentration of that beer is 5 %, he has consumed 50 ml pure alcohol. 1ml alcohol = 0.789 grams alcohol. Thus the man has consumed (50 x 0.789) 39.45 grams alcohol. His maximum BAC-level now is: 39.45/(80 x 0.S68) = 0.9 g/l
The formula can be refined by also taking the rate of absorption of alcohol from the body in time into account. It must be stressed that the 'Widmark formula' is a rough indicator only
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Even if the alcohol has completely disappeared from the body, there still can be acute effects. If alcohol has been consumed excessively, this will lead to a hangover. A hangover is the result of dehydration, low blood sugar, and poisoning. The symptoms of a hangover are: headache, thirst, vertigo, nausea, insomnia, and fine tremors of the hand. The psychological symptoms include: acute anxiety, guilt, depression, irritability, and extreme sensitivity.
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