special subjects
Alcohol Toxicity and Withdrawal
Pathophysiology of Alcohol Toxicity and Withdrawal
One serving of alcohol (one 12-oz can of beer, one 6-oz glass of wine, or 1.5 oz of distilled liquor) contains 10 to 15 g ofethanol. Alcohol is absorbed into the blood mainly from the small bowel, although some is absorbed from the stomach. Alcohol accumulates in blood because absorption is more rapid than oxidation and elimination. The concentration peaks about 30 to 90 minutes after ingestion if the stomach was previously empty. About 5 to 10% of ingested alcohol is excreted unchanged in urine, sweat, and expired air; the remainder is metabolized, mainly by the liver, where alcohol dehydrogenase convertsethanolto acetaldehyde. Acetaldehyde is ultimately oxidized to CO2 and water at a rate of 5 to 10 mL/hour (of absolute alcohol); each milliliter yields about 7 kcal. Alcohol dehydrogenase in the gastric mucosa accounts for some metabolism; women have lower gastric alcohol dehydrogenase activity than men. Alcohol exerts its effects by several mechanisms. Alcohol binds directly to gamma-aminobutyric acid (GABA) receptors in the central nervous system, causing sedation. Alcohol also directly affects cardiac, hepatic, and thyroid tissue. Tolerance to alcohol develops rapidly; similar amounts cause less intoxication. Tolerance is caused by adaptational changes of central nervous system cells (cellular, or pharmacodynamic, tolerance) and by induction of metabolic enzymes. People who develop tolerance may reach an incredibly high blood alcohol content (BAC). However,ethanoltolerance is incomplete, and considerable intoxication and impairment occur with a large enough amount. But even people who have developed tolerance may die of respiratory depression secondary to alcohol overdose. Alcohol-tolerant people are susceptible to Alcoholic Ketoacidosis , especially during binge drinking. Alcohol-tolerant people are cross-tolerant to many other central nervous system depressants (eg, barbiturates, nonbarbiturate sedatives, benzodiazepines). The physical dependence accompanying tolerance is profound, and Withdrawal has potentially fatal adverse effects. Chronic heavy alcohol intake typically leads to liver disorders (eg, fatty liver, Pathology , Chronic heavy intake also commonly causes the following: Overview of Gastritis None Overview of Pancreatitis None Overview of Cardiomyopathies , often accompanied by arrhythmias and hypertension Peripheral Neuropathy None Brain damage, including Wernicke Encephalopathy , Certain cancers (eg, liver, head and neck, esophageal), especially when drinking is combined with smoking Indirect long-term effects include Overview of Undernutrition , particularly vitamin deficiencies. 1 to 2 drinks/day) may decrease the risk of death due to cardiovascular disorders ( Pathophysiology reference ). Numerous explanations, including increased high density lipoprotein (HDL) levels and a direct antithrombotic effect, have been suggested. Nonetheless, alcohol should not be recommended for this purpose, especially when there are several safer, more effective approaches to reduce cardiovascular risk. Young children who drink alcohol are at significant risk of hypoglycemia because alcohol impairs gluconeogenesis and their smaller stores of glycogen are rapidly depleted. Women may be more sensitive than men, even on a per-weight basis, because their gastric (first-pass) metabolism of alcohol is less due to lower activity of alcohol dehydrogenase in the gastric mucosa. Drinking during pregnancy may result in Fetal Alcohol Syndrome . 1.Piano MR: Alcohol's effects of the cardiovascular system.Alcohol Res38(2):219–241, 2017. 