Forensic Pathology for Police - Brainshare Public Online Library

270 11 Drug-Related and Toxin-Related Deaths
the “blood alcohol concentration” (BAC). The units are expressed in weight/volume
of whole blood, so the BAC can actually be written in many forms, including percent
(%), grams per 100 mL whole blood (g/100 mL), grams per deciliter (g/dL),
milligrams per deciliter (mg/dL), milligrams percent (mg%), or grams per liter
(g/L). The appropriate equivalent values for each of these is as follows: 0.10 % =
0.1 g/100 mL = 0.10 g/dL = 100 mg/dL = 100 mg% = 1.0 g/L. The usually
legal limit within the US is 0.08–0.10%, depending on the jurisdiction. The ratio
between blood and breath ethanol percentage is constant, at 1 to 2100. This number
allows the “breathalyzer” analysis to convert to an equivalent BAC. Of note regarding
autopsy specimens is the fact that, in many laboratories, a postmortem blood
alcohol level is actually performed on serum (the liquid part of blood, without the
blood cells), rather than whole blood. The serum ethanol level is typically 12–18%
higher than that of whole blood.
The usual route of administration of EtOH is via GI absorption after oral ingestion.
The EtOH is absorbed predominantly in the small intestines. Food may slow
absorption. A vast majority of EtOH is metabolized within the liver by enzymes
that convert EtOH to acetaldehyde and then acetic acid. A small percentage of
EtOH within the blood is excreted in the urine, sweat, and breath. The average
non-alcoholic person’s ability to eliminate EtOH is about two thirds to one drink
per hour.
Although the legal limit is established by statute, it is well documented that in
many individuals physiologic impairment occurs at levels less than the legal limit.
As the BAC increases, a person becomes more and more intoxicated, displaying various
signs and symptoms, including slurring of speech, incoordination, and slowed
responses, among others. In persons who are chronic abusers of EtOH, it is common
for “tolerance” to occur, such that the individual may actually appear sober
with BACs that would make most people obviously drunk. In non-tolerant individuals,
BAC levels at or above 4.0 g/dL can be considered lethal; however, some argue
that levels as low as 3.0 g/dL can be lethal. In living chronic alcoholics, it is not
unusual to see levels higher than 4.0 g/dL.
The toxic effects of EtOH encompass a spectrum of changes within numerous
organ systems. Within the CNS, EtOH has a depressant effect. Wernicke−Korsakoff
encephalopathy, cerebellar vermis atrophy, contral pontine myelinolysis (CPM),
and seizures can occur. The liver changes include steatosis (fatty change), hepatitis
(inflammation), and cirrhosis (scarring) (Fig. 11.16). GI system effects include portal
hypertension, esophageal varices, peptic ulcer disease, gastritis, Mallory−Weiss
syndrome (lacerations of esophagus from vomiting), and pancreatitis (inflammation
of the pancreas). EtOH is considered a cardiac irritant, with intoxicated persons
being at increased risk of an arrhythmia. In addition, chronic use can result in a
dilated cardiomyopathy. Chronic alcoholics tend to be malnourished, have vitamin
deficiencies (especially thiamine), and are prone to electrolyte disturbances, such as
occurs in the low-salt vitreous electrolyte pattern. Deaths related to chronic alcoholism,
without accompanying acute intoxication, should be ruled as natural deaths.
This includes deaths related to alcohol withdrawal (delirium tremens).