Chapter 9 Physiology of Alcohol and Poisons

Chapter 9—Physiology of Alcohol and Poisons

Introduction—Objectives

1.Describe the role of a forensic toxicologist.

2.Discuss the legal importance of blood alcohol levels.

3.Explain the effects of alcohol and specific drugs and poisons on the body.

4.Discuss chemical agents that may be used for bioterrorism.

5.Describe analytical techniques for detection and identification of alcohol, poisons, and toxins in bodily fluids.

Introduction—Vocabulary

depressant—a chemical that slows the heart rate and brain activity and causes drowsiness

Immunoassay—a test that relies on the antigen-antibody response

Nystagmus—involuntary jerking movement of the eyes

Poison—a chemical that can harm the body if ingested, absorbed, or breathed in sufficiently high concentrations

Tolerance—in response to prolonged, heavy intake of alcohol or other drugs, the body’s need for progressively larger amounts of a chemical to cause the same levels of intoxication

Toxin—a type of poison produced naturally by living things

Michael Jackson

June 25, 2009, an accidental homicide

Homicide—a person died at the hands of another person

An overdose of medicines prescribed by Jackson’s doctor, Conrad Murray

Coroner’s determination—the interaction of anesthetics and sedatives caused Jackson to stop breathing.

History (Obj 9.1)

Early 1700’s—first use of chemistry to detect poisons

Early 19th century—toxicology became a new scientific discipline

France in 1840—Charles Lafarge trial involved testing for arsenic

Forensic toxicologists—study the legal and medical aspects of alcohol, drugs, poisons, and toxins in bodily fluids.

Alcohol (Obj 9.2, 9.3)

In everyday speech, alcohol usually refers to the ethanol used in alcoholic beverages.

In chemistry, alcohols are a group of substances with a hydroxyl group.

All alcohols are toxic in sufficient quantities

As little as 30 mL of methanol can kill

Ethanol, ethyl alcohol, is a colorless liquid obtained from fermented grains or fruits

Initial reaction to alcohol is euphoria

Alcohol is actually a depressant

Alcohol in the Body

Alcohol diffuses through the stomach and small intestines

As alcohol concentration increases:

•ability to respond to stimuli decreases

•temporary euphoria results from depressing inhibitions

•lose coordination and become confused

•memory diminishes

The liver metabolizes alcohol with an enzyme called alcohol dehydrogenase (ADH)

Resulting product is acetaldehyde

More enzymes break this into CO2 and H2O

The body can metabolize 15 to 30 mL of alcohol per hour

Excess alcohol is distributed to body tissues

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Stages of Intoxication

A blood alcohol concentration of 0.08 means 8 g of alcohol per 10,000 mL of blood

Alcohol affects different people differently

Concentration / Behavior
0.01 to 0.05 / Normal behavior
0.03 to 0.12 / Euphoria begins
0.09 to 0.25 / Vision blurs, loss of balance, sleepiness
0.18 to 0.30 / Speech slurs, dizzy, disoriented, emotional
0.25 to 0.40 / Standing and walking is difficult
0.35 to 0.50 / Impaired respiratory and circulatory systems
Over 0.45 / Potentially fatal

Stages of Intoxication

Factors affecting alcohol absorption

•Body weight

•How much alcohol is consumed

•Over what time period

•Amount of food in the stomach

•Frequency of drinking alcohol

•Body fat percentage

•Medications and popular energy drinks

Tolerance

Metabolic tolerance—the body produces larger amounts of alcohol dehydrogenase

Functional tolerance—a person displays fewer visible symptoms of intoxication without affecting blood alcohol concentration

Field Sobriety Tests

Horizontal gaze nystagmus (HGN) test

•Nystagmus is the involuntary jerking of human eyes, which increases with intoxication

Divided-attention tests

Breath tests

•Direct correlation between alcohol in the breath and alcohol in the blood stream

•Ratio is 1:2100

Blood and Urine Tests

Toxicology labs use gas chromatography/ mass spectrometry (GC/MS)

Gas chromatography separates the sample into individual components

Poisons (Obj 9.3, 9.4)

Eaten (ingested)

•90% - at home, involving children

•household cleaners

Inhaled

•carbon monoxide

•sarin, a nerve gas

Injected

•heroin

Absorbed

•Poison sumac, mustard gas, ricin, anthrax

Drugs

Toxicological Testing (Obj 9.5)

Detect trace amounts of drugs in the blood, urine, and body tissues with

•thin layer chromatography,

•gas chromatography, and

•immunoassay techniques

Confirmation is achieved
using GC/MS.

Toxicological Testing

Reinsch test—for heavy metal poisoning

•Certain metals dipped in hydrochloric acid produce a silver-colored coating on copper

Emission spectroscopy or atomic absorption spectrophotometry—identifies the specific metal

Blood gas screenings—detects level of CO in the blood stream

Toxicological Testing

Immunoassay—measures the level of antibodies produced in response to antigens (poisons) entering the bloodstream

EMIT—enzyme-multiplied immunoassay technique

•Rapidly detects several drugs and their metabolites

Chapter Summary

Poisons are chemicals that harm the body if ingested, inhaled, or absorbed through the skin.

Forensic toxicologists investigate the legal and medical aspects of alcohol, drugs, poisons, and toxins in the body; also

•testifying as expert witnesses,

•collaborating with the medical examiner, and

•analyzing evidence.

The role of forensic toxicologist also includes:

•testing employees for drug use,

•screening athletes for drug use, and

•testing sexual assault victims for the presence of date rape drugs.

In everyday speech, alcohol usually refers to the ethanol used in alcoholic beverages.

In chemistry, alcohols are a group of substances with a hydroxyl group.

Alcohol is a depressant.

•Initially, it causes feelings of euphoria.

•When more is consumed,

•motor skills become impaired,

•brain function is depressed, and

•the person may even lapse into a coma and die.

The liver can metabolize about 15 to 30 mL of alcohol per hour. A person becomes intoxicated when consumption exceeds that.

When a driver is suspected of intoxication, several field sobriety tests are given

Presumptive tests

•horizontal gaze nystagmus and

•divided-attention tests

Conclusive test

•breath tests can determine blood alcohol levels.

How the poison enters the body determines its effect on the body

•inhaled poisons can cause asphyxia

•ingested poisons often target specific organs

Testing procedures

•Chromatography techniques, mass spectrometry, and immunoassay are used to detect various poisons and drugs in urine and blood

•Reinsch test detects heavy-metal poisoning

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