Alcohol is a depressant drug and, as such, at high enough blood alcohol concentrations can cause death due to alcohol poisoning by severe depression of the central nervous system, most probably the respiratory center, which causes the poisoned person to stop breathing.
At what BAC death occurs can be a matter of controversy. Some heavy drinkers, alcohol abusers or alcoholics can develop a high tolerance to the poisoning effects of alcohol and survive at BACs of > 0.400 g/100mL or higher, while operating a motor vehicle. This is seen in my earlier blog (Drinking and Driving- Not Just a Night Thing! posted October 1st, 2013) Two studies by Jones and Holmgren addressed this issue as follows:
Jones, A.W., and Holmgren, P., “Comparison of Blood Ethanol Concentrations in Deaths Attributed to Acute Alcohol Poisoning and Chronic Alcoholism”, Journal of Forensic Sciences, 48: 874-879, 2003 (2 tables, 3 figures, 50 references), WOA70405
And
Jones, A.W., and Holmgren, P., “Urine/Blood Ratios of Ethanol in Deaths Attributed to Acute Alcohol Poisoning and Chronic Alcoholism”, Forensic Science International, 135: 206-212, 2003 (2 tables, 4 figures, 3 references), WOA70408
In the first study, Jones and Holmgren compared the postmortem femoral BAC of 693 victims of acute alcohol poisoning and 825 victims who died of chronic alcoholism. The following table summarizes a comparison of the 2 groups.
The lower UAC/BAC ratio found in acutely alcohol-poisoned victims tends to indicate that death occurred before absorption and distribution were complete, near or just before the peak BAC was obtained. Also, note there is an overlap in the BAC ranges of acutely poisoned victims and those who die of other causes. Some individuals are poisoned at relatively low BACs. And others with high tolerance to alcohol survive high BACs.
Reasons for Alcohol Poisoning at Low BACs
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Age, Gender, Health
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Tolerance (Drinking Experience)
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Resuscitation/Hospital Treatment
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Aspiration of vomitus
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Positional asphyxia
Conclusion
Perper, Twerksi and Wienand, 1986 (WOA50612), I feel conclude and issue a caveat about at what BAC alcohol does kill as follows:
From a medico-legal point of view, the interpretation of a high blood alcohol concentration as an indicator of incapacitation, manifest drunkenness, or as an exclusive cause of death is unreliable. Therefore, for example, a bartenders who serves a chemically intoxicated person (that is, having ispso facto a high BAC) should not be accused of serving alcohol to an obviously clinically intoxicated individual.
One should not, however, conclude that apparent clinical sobriety in chemically intoxicated alcoholics reflects safe or acceptable driving capabilities. Driving combines a complex array of physical and mental activities that require anticipatory judgments, estimates of distance, peripheral vision and short reaction time to unexpected hazards, all of which are known to be adversely affected by alcohol.
