By Edwin T. Scallon, Copyright © 1990, 1995, 2008 All Rights Reserved
ACCIDENT RECONSTRUCTION AND BAC CALCULATION PROGRAMS
ABSORPTION OF ALCOHOL
As we have seen alcohol no that matter its source once it enters the human body, it eventually leaves, unless the person is dead. In this area we are concerned with how ethanol gets absorbed into the blood stream, how much actually gets absorbed, where it gets absorbed, where it goes upon absorption, and how much gets to the brain.
An interesting dissertation of a defense to DUI by David Anaise, MD JD, although targeted as a legal argument for defenses of Drunk Driving, it is noteworthy in any event since his research is accurate. He proffers the following:
Defense of a person arrested for DUI has long been an attack on the breath testing equipment. His challenge, thus is not on the accuracy of the breath-analyzer but rather on the theory that it is impermissible to admit such results as scientists agree that during the absorptive phase equilibration of alcohol has not yet occurred and the pulmonary vein blood alcohol (estimated by BrAC) does not reflect the alcohol levels in the brain.
The absorptive phase also has unique advantages in the defense of the accused because of the effect of first pass metabolism which effectively reduces by half the amount of alcohol circulating in the systemic circulation and the increase elimination of alcohol observed in the fed state. As a result, a much larger amount of alcohol is needed (almost twice) to intoxicate an individual in the fed state as compared to the fasting state. A scientific defense can thus be mounted to show that the breath analyzer in the fed state is grossly inaccurate because based on the amount of alcohol ingested in the accused it will be practically impossible for the BAC to reach the level of legal intoxication measured by Widmark's formula.
First Pass Metabolism is the difference between the quantity of alcohol that has reached the systemic circulation by intravenous route and the quantity that entered the circulation by the oral route. The amount of alcohol absorbed through the intestinal tract is only a faction of the alcohol dose provided assuming 100% absorption by the IV route.
Gentry, et al, at Dr. Charles S. Lieber's laboratory published a study on First Pass Metabolism (FPM),. They provided social drinkers with generous drink 300 milligrams per Kg dose of 10% wt/vol alcohol. When the subjects ingested alcohol with a standard meal, 28% of the alcohol drunk did not reach the systemic circulation. In some cases, only half the dose was absorbed. They argued that the site of the First Pass is the stomach, because when alcohol was given directly to the duodenum (small intestine just after the pyloric sphincter (opening from the stomach to the small intestine)), measured the same BAC as those given EtOH by the IV route rather than the oral route. In experiments where the pylorus of animals were ligated, only about a third of the alcohol reached the systemic circulation after four hours.
The enzyme ADH responsible for degradation of alcohol is most conspicuous but not the only enzymatic system capable of metabolizing -or more accurately absorbing - ethanol in the gastric mucosa. ADH is abundant in the mucus producing cells lining in the mucosa of the human stomach. The stomach ADH is efficient in eliminating alcohol because there are several iso-enzymes that allow for handling of alcohol at different concentrations.
Dr Michael Levitt from the Research Service Veteran Affairs Medical Center in Minnesota Medical School agreed with Dr. Gentry's analysis of First Pass Metabolism. He stated that at least 35% of alcohol does not reach the systemic circulation. Dr. Levitt argues however that the site of the destruction of alcohol is the liver. According to Levitt the fist pass metabolism is dependent on the rate for alcohol delivered to the the liver. Hence, absorption through the stomach is delayed, the liver very efficiently removes the low alcohol concentration at first pass and prevents alcohol from arriving at the systemic circulation. When the alcohol passes quickly into the small intestine, the liver is overwhelmed by the amount of alcohol provided and its capacity to remove a significant portion of alcohol from the systemic circulation is greatly diminished The importance of this observation is that the Widmark formula can not accurately calculate the BAC during First Pass during the fed state.
A.W.Jones, perhaps the most noted investigator of alcohol metabolism observed that when the subject was given .8 gram per Kg of alcohol on an empty stomach, the subject reached the intoxicating level of 10% at 40 minutes. When the same subject was fed breakfast, his blood alcohol level, at 49 minutes was less than .05 or half of the maximum BAC during the fasting. (Ed. Note: Breakfast and Alcohol?) In contrast to a peak of 40 minutes in the fasting state, the subject BAC after breakfast, peaked at two hours. (Ed. Note: Although FPM is important and the studies do support the slower absorption rate, for our purposes, total absorption will generally occur in 90 minutes from the oral ingestion of EtOH, based on MY INVESTIGATIONS.)
Dr. Jones explained his results by stating that the delayed absorption of alcohol in the fed state enhanced the FPM action. In the fed state the liver more efficiently removed alcohol from the circulation and the delay in stomach emptying provided more time for ethanol to be destroyed in the stomach by ADH. As more alcohol is destroyed by ADH in the stomach and more alcohol is destroyed by the liver less alcohol is absorbed into the systemic circulation. Dr. Jones opined: "A more prolonged absorption phase and a later occurring peak was frequently observed when alcohol was taken together with or after a meal compared with drinking on an empty stomach."
We will learn that although absorption is slower, the breath testing equipment tests the breath which contains alcohol given up in the lungs which obtained the breath EtOH from the blood capillaries in the lungs. The results are startling (See Breath Test Instruments in the web panel)
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