RAPID ALCOHOL DISPOSITIONAL METABOLISM
Witnesses reported that the decedent (D) was drinking beer during his 7-12 p.m. shift as a cook. The restaurant owner denied knowledge of drinking during the shift and testified that (D) did not appear to be intoxicated when she departed the restaurant at 11:00 p.m.. After midnight, (D) remained in the restaurant parking lot drinking beer until 2:30 a.m. when he departed in the company truck. He was authorized to use the vehicle on occasion to obtain supplies. (D) was a restrained driver in a one-car roll over accident shortly after 3:00 a.m.. The whole blood equivalent alcohol was 0.197 Gm% one hour after the accident and 0.092 Gm% at the time of death 2.25 hours after the accident, resulting in a whole blood alcohol dispositional rate of 0.04 Gm% per hour.
PLAINTIFF POSITION: Survivors sued, alleging the employer provided alcohol while (D) was on the job; should have recognized he was alcohol-impaired at 11:00 p.m.; allowed him to continue to drink beer on the premises; and should not have permitted him to drive the company automobile under the influence of alcohol.
DEFENSE POSITION: Personnel policies specifically prohibited drinking alcoholic beverages while at work; (D) appeared unimpaired at 11:00 p.m.; and (D) did not have permission to use the company truck.
DISCUSSION: Two alcohol analyses were performed, each in duplicate by two different laboratories, permitting a rare opportunity to calculate dispositional rate of alcohol in whole blood, one of three mechanisms of tolerance. With several weeks of frequent alcohol use, the body adapts to metabolize alcohol more rapidly, resulting in lower blood levels for the same quantity of alcohol ingested. (D) could drink approximately two beers per hour without accumulating an elevated blood alcohol, illustrating one problem with the use of drink counts to estimate blood alcohol. As demonstrated in the notes, (D) had ingested approximately 21 to 22 12-ounce cans of beer prior to the accident. Since nine hours had passed between 7:00 p.m. and 4:00 a.m., the average accumulation per hour was 0.022 Gm%.
At 11:00 p.m., blood alcohol would be approximately 0.09 Gm% or less if disproportionally more alcohol were ingested while in the parking lot after midnight than while working. At this concentration, signs of impairment would not be apparent, supporting the testimony of the employer that (D) did not appear impaired when seen at 11:00 p.m.. The relative probability of responsibility for a fatal crash increases exponentially with increase in blood alcohol concentration and exceeds 70 when blood alcohol is over 0.19% (AMA Council, 1986).
The odds ratio that this accident was alcohol-related exceeds 70. The risk of an accident when blood level is approximately 0.2 Gm% is increased more than 70 times.
Settlement for an undisclosed amount was reached before trial.
Eric G. Comstock, M.A., M.D., DABMT, FACMT, FAACT, FACOEM, expert
for the defense (9307). Attorney for the Defense, Joseph Segrato, Corpus Christi, Texas
If you have any questions please
let me know.
ALCOHOL CONTENT OF BODY AT TIME OF DEATH:
Body weight 185 lbs = 84 Kg.
Volume of distribution of alcohol = Volume of body water or 60% for a male of average stature = 84 x 0.6 = 50.4 liters
Blood alcohol = 0.9 Gm/Liter of whole blood
Since Blood is approximately 80% water then concentration in body water = 0.9/0.8 = 1.12 Gm/Liter
Total body alcohol content = 50.4 x 1.12 = 56.7 Gms.
ALCOHOL METABOLIZED
Alcohol dispositional rate per hour = 0.4 Gm/0.8 liters = 0.5 Gm/Liter of body water/hr.
Total alcohol metabolized per hour = 0.5 Gm/Liter of body water x 50.4 liters = 25.2 Gms.
Total alcohol metabolized between 7:00 p.m. and 4:00 a.m. = 9 x 25.2 Gm = 226.8 Gms.
Minimum total alcohol consumed = 56.7 + 226.8 = 283.5 Gms = 283.5/0.8 ml = 354.3 ml of ethanol.
If beer contained 4.5% alcohol by volume then 354/0.045 = 7866 ml/30 ml = 262 oz/12 = 21.8 cans.
Parameters: (1) Known body weight, height and age; (2) dispositional metabolic rate; (3) accident occurred at 3:00 a.m.. Assumed: (1) Blood alcohol zero at 7:00 p.m.; (2) drinking started at 7:00 p.m. and continued to 2:30 a.m.; (3) blood alcohol never dropped below 0.01 during the drinking interval; (4) ingestion stopped at 2:30 a.m.; (5) per cent body water 60; (6) volume of distribution = 0.6 x body weight in kilograms = liters; (7) beer contained 4.5% alcohol by volume; (8) dispositional metabolic rate remained constant. Not considered: first pass metabolism.
Alternative assumptions will yield different numbers but moderate variation in any parameter will not change the outcome qualitatively.
DISPOSITIONAL METABOLISM OF ALCOHOL
After alcohol is absorbed into the blood stream, the principle mechanism of detoxification is metabolism. At high concentrations, the rate of metabolism is accelerated; at midrange concentrations, the rate remains constant; and at low concentrations, the rate of metabolism is slowed. The major factor determining the rate of metabolism is alcohol drinking experience. For purposes of extrapolation, the best data is derived by the direct measurement using two or more points in time to calculate directly this parameter. In the vast majority of cases, this data is not available and assumptions must be made. Since most cases involve alcohol concentrations within the range of 0.01 Gm% and 0.3 Gm%, zero order kinetics apply, and the rate of disappearance from the blood is constant.
Determination of zero order kinetics should not be confused with the amount of alcohol which can be metabolized per hour since this involves additional variables such as volume of distribution.
Alcohol tolerance is influenced by alcohol metabolic rate since the more rapidly alcohol is cleared from the body, the greater will be the amount of alcohol which can be consumed per hour without accumulation in the body and the more rapidly sobriety is achieved upon cessation of drinking. Dispositional tolerance is not a measure of the relationship between blood alcohol concentration and impairment.
The range of dispositional metabolism commonly quoted is 0.014 to 0.040 Gm% in whole blood per hour. The lower limit would apply to a healthy teenager with no drinking experience and the upper range applies to a frequent user of multiple drinks per episode. A social drinker using several times a week but able to remain alcohol free for several days without withdrawal would be expected to have a dispositional rate of about 0.020 Gm% per hour. Other factors which could influence dispositional metabolism are discussed by Baselt and Danhof, 1988.
REFERENCES:
AMA Council on Scientific Affairs. Alcohol and The Driver. JAMA 255(4):522-527, Jan 24/31, 1986.
Baselt RC, Danhof IE. Disposition of Alcohol in Man. In: Medicolegal Aspects of Alcohol Determination in Biological Specimens; James C. Garriott, Editor, 1996; Chap. 3, pp.65-78.
Hobbs WR, Rall TW, Verdoorn TA. Ethanol: Absorption, Fate and Excretion. In: Goodman & Gilman's The Pharmacological Basis of Therapeutics, Ninth Edition, 1996; Chap. 17, Hypnotics and Sedatives, pp.389.
Widmark EMP. Principles and Applications of Medicolegal Alcohol Determination, 1981, Biomedical Publications.
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