Determination of ethanol

Ethyl alcohol (ethanol, C ₂ H ₅ OH) has a sedative-hypnotic effect. When ingested, ethanol, as well as methanol, ethylene glycol and other alcohols, is easily absorbed from the stomach (20%) and the small intestine (80%) due to its low molecular weight and lipid solubility. The rate of absorption depends on the concentration: for example, in the stomach it is maximal at a concentration of approximately 30%. Ethanol vapor can easily be absorbed into the lungs. After taking ethanol on an empty stomach, the maximum concentration in the blood is reached after 30 minutes. The presence of food in the intestine delays absorption. The distribution of ethanol in the body tissues occurs quickly and evenly. More than 90% of the ethanol supplied is oxidized in the liver, the remaining is released through the lungs and kidneys (within 7-12 hours). The amount of alcohol oxidized per unit time is approximately proportional to body weight or liver mass. An adult can metabolize 7-10 g (0.15-0.22 mole) of ethanol per hour.

The metabolism of ethanol is mainly carried out in the liver with the participation of two enzyme systems: alcohol dehydrogenase and microsomal ethanol oxidizing system (MEOS).

The main pathway of ethanol metabolism is associated with alcohol dehydrogenase - a Zn ²⁺ -containing cytosolic enzyme that catalyzes the conversion of alcohol to acetaldehyde. This enzyme is found mainly in the liver, but is present in other organs (for example, in the brain and stomach). In men, a significant amount of ethanol is metabolized by alcohol gastric dehydrogenase. The MEOS includes oxidases with a mixed function. The intermediate product of ethanol metabolism with the participation of the MEOS is also acetaldehyde.

It is believed that when the alcohol concentration in the blood is below 100 mg% (22 nmol / l), its oxidation is mainly carried out by alcohol dehydrogenase, whereas at higher concentrations, the MEOS begins to play a more significant role. At present, it has not been proven that alcohol alcohol dehydrogenase activity increases with chronic alcohol consumption, but it is reliably established that the activity of MEOS increases. More than 90% of acetaldehyde, formed from ethanol, is oxidized in the liver to acetate with the participation of mitochondrial aldehyde dehydrogenase. Both reactions of ethanol conversion are NAD-dependent. Deficiency of NAD as a result of its consumption during alcohol intoxication can block the aerobic metabolism and limit the conversion of the final product of the glycosylation of carbohydrates and amino acids - lactic acid. Lactate accumulates in the blood, causing metabolic acidosis.

The mechanism of action of alcohol on the central nervous system is unknown. At the same time, it has been established that non-physiological concentrations of ethanol inhibit ion pumps responsible for the generation of electrical nerve impulses. As a result, alcohol suppresses the functions of the central nervous system, like other anesthetics. Alcohol intoxication develops typical effects of a sedative-hypnotic overdose along with cardiovascular effects (vasodilation, tachycardia) and gastrointestinal irritation. The relationship between the concentration of ethanol in the blood and the clinical manifestations of intoxication is presented in Table. 11-2. The lethal dose of ethanol in a single dose is from 4 to 12 g per 1 kg of body weight (an average of 300 ml of 96% ethanol in the absence of tolerance to it). Alcoholic coma develops at a concentration of ethanol in the blood above 500 mg%, and death - above 2000 mg%.

The relationship between the concentration of ethanol in the blood and urine, and the clinical manifestations of intoxication

Concentration of ethanol, mg%		Stage of alcoholic intoxication	Clinical manifestations
Blood	Urine
10-50	10-70	Sober state	Weak influence on most people
40-100	30-140	Euphoria	Decrease in self-control and reaction time (by 20%)
100-200	75-300	Excitation	Violation of coordination, loss of criticism, lengthening reaction time (by 100%)
200-300	300-400	Confusion of consciousness	Disorientation, vague speech, impaired sensitivity, memory loss
300-400	400-500	Stupor	Impaired ability to stand or walk
More than 500	More than 600	Coma	Disturbance of breathing, suppressed all reflexes
More than 2000	More than 2400	Death	Respiratory paralysis

Instability of gait, indiscriminate speech and difficulty in performing simple tasks become apparent when the concentration of ethanol in blood plasma is approximately 80 mg%. In this regard, in a number of countries this value serves as a boundary for prohibiting the management of motor vehicles. The mastery of the driver is reduced, even at lower ethanol concentrations.

When determining the concentration of ethanol in blood serum, it should be borne in mind that it is 10-35% higher than in blood. When using the method of determining ethanol with alcohol dehydrogenase, other alcohols (for example, isopropanol) can serve as substrates and cause interference, which leads to false positive results.

The degree of intoxication depends on three factors: the concentration of ethanol in the blood, the rate of rise in the level of alcohol and the time during which an increased level of ethanol in the blood is stored. The nature of consumption, the condition of the gastrointestinal mucosa and the presence of drugs in the body also affect the degree of intoxication.

To assess the level of ethanol in the blood, the following rules should be used.

• The peak concentration of alcohol in the blood is reached after 0.5-3 hours after taking the last dose.
• Every 30 grams of vodka, a glass of wine or 330 ml of beer increase the concentration of ethanol in the blood by 15-25 mg%.
• Women absorb alcohol faster than men, and its concentration in the blood is 35-45% higher; During the premenstrual period, the concentration of ethanol in the blood rises faster and to a greater extent.
• Taking oral contraceptives increases the concentration of ethanol in the blood and increases the duration of intoxication.
• The concentration of ethanol in urine is not very well correlated with its level in the blood, therefore it can not be used to assess the degree of intoxication.
• In older people, intoxication develops faster than in young people.

The respiratory tests currently used to determine alcohol have their own peculiarities and limitations. The concentration of ethanol in the exhaled air is approximately 0.05% of the blood concentration, i.e. 0.04 mg% (0.04 mg / L) at a blood concentration of 80 mg% (800 mg / l), which is sufficient to detect it respiratory tests.

The time of detection of ethanol by respiratory tests

Type of alcohol	Dose, ml	Detection time, h
Vodka 40 °	50	1.5
Vodka 40 °	100	3.5
Vodka 40 °	200	7th
Vodka 40 °	250	9
Vodka 40 °	500	18
Cognac	100	4
Champagne	100	1
Cognac and champagne	150	5
Port wine	200	3.5
Port wine	300	4
Port wine	400	5
Beer 6 °	500	0.75
Beer below 3.4 °	500	Not determined

[1], [2], [3], [4], [5],