The units used to report blood alcohol levels for clinical and forensic purposes are expressed either by mass per unit volume (e.g. g/l, mg/ml or g/100 ml) or by mass per unit mass (e.g. g/kg or mg/g). In most countries, mass/volume units are used, although, for historical reasons, in Germany and the Nordic countries, blood alcohol level is defined as mass for legal purposes. Given that the average whole blood density is 1.055, 100 mg/100 ml of blood is close to 95 mg/100 g of blood (Dettmeyer et al., 2014). In most U.S. jurisdictions, the prima facie case of the influence of alcohol on the operation of a motor vehicle is 80 mg/dl. In hospital clinical laboratories, alcohol is determined in plasma or serum samples, not in whole blood. This must be taken into account when using clinical laboratory results in criminal cases such as drunk driving. Since the water content of serum and plasma (~92% w/w) is higher than in an equal blood volume (~80% w/w), ethanol concentrations are also higher.
Direct measurements have shown that the average ethanol distribution ratio between serum (plasma) and whole blood is 1.15:1, with a range of 1.10:1 to 1.20:1 (Charlebois et al., 1996). In addition, clinical laboratories report ethanol concentrations in mmol/L, where 21.7 mmol/L = 100 mg/100 mL, or 0.1% w/v. Significant deficiency can occur with an alcohol level < 100 mg / dl. Deterioration in driving skills can occur at concentrations of <50 mg/dl, and manoeuvres to avoid an accident, such as steering and braking, can be impaired at concentrations of about 30 mg/dl. Legal limits for intoxication are not uniform in the United States. The majority of states have set legal limits at 100 mg/dL, while others have lowered the limit to 80 mg/dL. The legal intoxication value of Kansas and Missouri is 100 mg/dL. More than 90% of ethanol is oxidized in the liver, mainly by the enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Metabolism to high concentrations of alcohol follows zero-order kinetics (regardless of time and concentration of the drug). In the initial metabolic pathway, DHA breaks down alcohol into the toxic metabolite acetaldehyde.
Small amounts of DHA are also found in other organs such as the stomach. This metabolite is further degraded to acetate by ALDH. Acetate is introduced into the Krebs cycle and eventually broken down into water and carbon dioxide. [11, 12, 13] The required sample is an SST blood tube. The venipuncture site should be cleaned with benzalkonium chloride or aqueous povidone iodine and NOT alcohol. Using an alcohol swab can wrongly increase blood levels. The serum should be immediately separated from the red blood cells and analyzed within 4 hours if taken without preservatives. Samples should be kept sealed as ethanol is volatile. Serum or plasma can be kept frozen. A legal blood alcohol level is often expressed as a percentage by weight (i.e.
grams of ethanol in 100 ml of blood). Clinical laboratories generally report the concentration of ethanol in mg per dl of blood. Lab values can be converted to blood alcohol levels by moving the three-digit comma to the left. For example, 135 mg/dl is 0.135% weight./vol. This value is then shortened to two digits to 0.13% by weight/vol or 0.13 g/dl. Teens and young adults have a higher risk of binge drinking, which can lead to alcohol poisoning. Binge drinking is a pattern of alcohol consumption that increases blood alcohol levels in a short period of time. Although it varies from person to person, binge drinking is generally defined as four drinks for women and five drinks for men over a two-hour period. Blood alcohol levels depend on many factors, including the number of drinks, gender (women have a higher blood alcohol level than men when they consume equal amounts of alcohol when body weights are comparable) and body weight. In addition, the maximum blood alcohol level is lower when alcohol is consumed with food and when alcohol is drunk instead of being consumed quickly. The presence of food not only reduces the blood alcohol level, but also stimulates its excretion from the liver.
The alcohol is first metabolized to acetaldehyde by the enzyme alcohol dehydrogenase, then to acetate by aldehyde dehydrogenase. The acetate eventually breaks down into carbon dioxide and water. With higher alcohol consumption, liver CYP2E1 plays a role in alcohol metabolism. Other names: alcohol test, ethanol test, ethyl alcohol, table of alcohol content in the blood. Effects of alcohol on blood alcohol concentration* (opens the table in a new window) Your report can provide blood alcohol test results in different ways, depending on the lab processing the test. The results are usually expressed as a percentage of blood alcohol level (BAC) – for example, 0.03% BAC. They can also be expressed in grams per milliliter (g/ml). This test result would be 0.03 g/100 ml. Household products have the following ethanol content: Blood alcohol level results can be reported in a variety of ways, including blood alcohol level (BAC). Typical results are below. Medically legal samples require proof of identity and ethanol is measured in a whole blood sample.
To determine recent intake. Because estimates of ethanol levels in breath samples are inaccurate, a blood sample may be required (e.g. when assessing a possible drug overdose and altered consciousness after trauma). Methods used for blood alcohol analysis can also be used to determine the amount of ethanol in urine samples. The quantitative relationship between urine alcohol concentration (UAC) and blood alcohol level has been extensively studied by Jones.14,15 In addition to the higher water content in urine (≈99%) compared to whole blood (≈80%), concentration-time curves are shifted in time. In an interesting study of the same group16, the UAC/BAC ratio was determined after volunteers drank a standard dose of ethanol (0.85 g/kg body weight) as clean whisky for 25 minutes on an empty stomach. The subjects emptied their bladders of any residual urine before starting to drink, and more cavities were collected every 60 minutes for 8 hours. Temporal variations in the UAC/BAC ratio were measured, and the mean ratio was less than the 60-minute vacuum unit, while after 120 minutes (the post-absorption phase) and all subsequent periods, the UAC/BAC ratio was 1.25 or higher (a ratio equal to 3.6 after 8 hours). After 360 minutes after drinking, when the blood alcohol level fell below 0.5 g/kg, the average CAU/BAC increased significantly and continued to increase as the blood alcohol level approached zero.
Therefore, if the time between the alleged crime and the blood sample is more than 8 hours, or if the blood alcohol level is close to 0 g / kg, it is recommended to take a urine sample and determine the urinary alcohol (ethanol). Storage: Samples should be kept sealed as ethanol is volatile. Serum or plasma can be kept frozen. In general, the legal driving limit is 0.05%, or 11 mmol / L or 0.05 g / 100 ml. In some areas, it is “0.08%”, or 18 mmol/L or 0.08 g/100 mL. The table below shows the most common effects seen at different blood alcohol levels, although there is wide variation between individuals and symptoms overlap between different blood alcohol levels. Urinary ethanol levels vary widely and do not correlate well with blood alcohol levels (and cannot be used to determine the degree of intoxication, according to Wallach; see more below). [5, 6] Alcohol poisoning initially affects the frontal lobe region of the brain, causing disinhibition, impaired judgment, and cognitive and problem-solving difficulties. With blood alcohol concentrations between 20 mg and 99 mg%, as well as increasing mood and behavior changes, the effects of alcohol on the cerebellum can lead to motor coordination problems.
At a blood alcohol level of 100 to 199 mg, there is neurological involvement with prolonged reaction time, ataxia and impaired coordination. Blood alcohol levels of 200 to 399 mg% are associated with nausea, vomiting, pronounced ataxia and hypothermia.
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