Blood alcohol content

Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes.

BAC is expressed as mass of alcohol per volume of blood. 

For example, a BAC of 0.10 (0.10% or one tenth of one percent) means that there is 0.10 g of alcohol for every 100 mL of blood.

A BAC of 0.0 is sober. 

The  limit of detection to 0.08%.

BAC levels over 0.08% are considered impaired; above 0.40% is potentially fatal.

Blood alcohol concentration, blood ethanol concentration, blood alcohol level, blood alcohol.

As BAC increases with consumptionmption, the short-term effects of alcohol become more perceptible. 

At low levels of impairment, with BAC 0.01–0.05%, people may experience mild relaxation and reduced social inhibition, along with impaired judgment and coordination. 

At moderate levels of impairment (BAC 0.06–0.20%), effects can include emotional swings, impaired vision, hearing, speech, and motor skills. 

Beginning at a BAC greater than 0.2%, people may experience urinary incontinence, vomiting, and symptoms of alcohol intoxication. 

At a BAC greater than 0.3%, people may experience total loss of consciousness and show signs of severe alcohol intoxication. 

A BAC of 0.4% or higher is potentially fatal and can result in a coma or respiratory failure.

Blood samples for BAC analysis are obtained by taking a venous blood sample.

The amount of alcohol on the breath can be measured, without requiring drawing blood, by blowing into a breathalyzer, resulting in a breath alcohol content (BrAC). 

The breath alcohol content specifically correlates with the concentration of alcohol in arterial blood, and its correlation with the standard BAC found by drawing venous blood is less strong.

A breathalyzer test is the most common method for measuring alcohol concentrations in most jurisdictions.

Explanations for the gender difference in blood alcohol content are quite varied and include liver size, secondary effects of the volume of distribution, and sex-specific hormones.

Eating food in proximity to drinking increases elimination rate of alcohol significantly.

United States standard drinks of beer, malt liquor, wine, and spirits contains about 14 grams or 17.7 mL of ethanol.

A standard drink is 0.6 fluid ounces (14 g or 17.7 mL) of ethanol, whereas other definitions exist, for example 10 grams of ethanol.

Individuals can learn to discriminate their BAC, to within a mean error of 9 mg/100 mL (0.009% BAC).

Vitreous eye fluid provides an accurate account of blood alcohol concentration in cadavers.

The National Institute on Alcohol Abuse and Alcoholism (NIAAA) define the term “binge drinking” as a pattern of drinking that brings a person’s blood alcohol concentration (BAC) to 0.08 grams percent or above. 

This typically happens when men consume five or more drinks, and when women consume four or more drinks, in about two hours.

BAC is is a fraction of weight of alcohol per volume of blood, with a coherent unit of grams per liter.

The US presents BAC as a percentage, such as 0.05%. 

This would be interpreted as 0.05 grams per deciliter of blood.

In pharmacokinetics, it is common to use the amount of substance, in moles, to quantify the dose. As the molar mass of ethanol is 46.07 g/mol, a BAC of 1 g/L is 217.06 mmol/L.[36]

Blood alcohol content is used to define intoxication and provides a rough measure of impairment. 

Although the degree of impairment may vary among individuals with the same blood alcohol content.

The alcohol level at which a person is considered legally impaired to drive varies by country.

Soon after death, the body begins to putrefy, a biological process which produces ethanol, making it difficult to conclusively determine the blood alcohol content in autopsies, particularly in bodies recovered from water.

The rate of elimination in the average person is commonly estimated at 0.015 to 0.020 grams per deciliter per hour (g/dL/h), which can vary from person to person and in a given person from one moment to another. 

Metabolism can be affected by body temperature, the type of alcoholic beverage consumed, and the amount and type of food consumed.

Alcohol is absorbed throughout the gastrointestinal tract, but more slowly in the stomach than in the small or large intestine. 

For this reason, alcohol consumed with food is absorbed more slowly, because it spends a longer time in the stomach.

Alcohol dehydrogenase is present in the stomach lining. 

After absorption alcohol passes to the liver through the hepatic portal vein, and there it undergoes a first pass of metabolism before entering the general bloodstream.

Alcohol is removed from the bloodstream by a combination of metabolism, excretion, and evaporation. 

Alcohol is metabolized mainly by six enzymes collectively called alcohol dehydrogenase. 

These convert the ethanol into acetaldehyde, which is an intermediate more toxic than ethanol.

The enzyme acetaldehyde dehydrogenase then converts the acetaldehyde into non-toxic acetic acid.

Typical doses of alcohol actually saturate the enzymes’ metabolic capacity, so that alcohol is removed from the bloodstream at an approximately constant rate. 

This alcohol metabolic rate varies considerably between individuals. 

There is a sex-based difference is in the elimination of alcohol, women are slower to metabolize alcohol.

People under 25, women, or people with liver disease may process alcohol more slowly. 

Falsely high BAC readings may be seen in patients with kidney or liver disease or failure, due to impaired acetaldehyde dehydrogenase, which causes acetaldehyde levels to peak higher, producing more severe hangovers and other effects such as flushing and tachycardia. 

Ethnicities that traditionally did not use alcoholic beverages have lower levels of alcohol dehydrogenases and sober up very slowly but reach lower aldehyde concentrations and have milder hangovers. 

The rate of alcohol detoxification can be slowed by certain drugs which interfere with the action of alcohol dehydrogenases, notably aspirin, fumes of certain solvents, many heavy metals, and some pyrazole compounds. 

Cimetidine, ranitidine, and acetaminophen are also suspected of slowing alcohol detoxification.

The only known substance that can increase the rate of alcohol metabolism is fructose:  a 100 g dose of fructose has been shown to increase alcohol metabolism by an average of 80%. 

Fructose also increases false positives of high BAC readings in anyone with proteinuria and hematuria, due to kidney-liver metabolism.

The peak of blood alcohol level or concentration of alcohol is reduced after a large meal.

There have been reported cases of blood alcohol content higher than 1%.

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