Forensic 2 Flashcards
alcohol is a CNS _____
depressant
sources of alcohol
wine, beer, liquor, cooking wine, mouthwash, after-shave lotion
what is the legal limit for driving?
80mg% BAC
what can we test for alcohol?
- blood or urine (living or dead)
- vitreous humour, CSF, bile (dead only)
- breath (living only)
Advantages of alcohol breath analysis?
- noninvasive
- convenient
Breath test equipment relies on _____ law
henry’s
What is Henry’s Law
The concentration of a gas dissolved in a liquid phase is directly proportional to the partial pressure of that gas in a gaseous phase that is in equilibrium with the liquid
What does henry’s law mean?
concentration of ethanol in blood / concentration of ethanol in alveolar air = r
r = constant = 2100
Describe pass, alert and fail results of the screening device
pass: between 0-49mg%
alert: 50-99mg%
fail: above 100mg%
Consumption = ?
absorption + elimination
Where does absorption of alcohol happen?
30% stomach
70% small intestine (more absorbed here due to increased surface area)
how is rate of absorption affected by food in the stomach
-get more absorption of alcohol on an empty stomach (15-20 mins on empty stomach, 2-3 hours on full stomach)
**also fats/carbs delay absorption more so than protein
how does drinking alcohol with carbonated beverages affect absorption?
carbonated beverages open pyloric sphincter longer which allows alcohol to go more quickly into the small intestine which increases absorption
how does speed of consumption affect rate of absorption?
speed increases rate of absorption
rate of absorption is also affected by _____ of alcohol
concentration
What are the approximate concentrations of alcohol in wine, liquor and beer?
beer: 5%
wine: 10%
liquor: 40%
what can rate of absorption also be affected by?
- drugs (nicotine and caffeine slow rate of absorption of alcohol)
- disease (trauma affects it)
- emotional state (get best absorption in a relaxed state)
what is the widmark hypothesis
alcohol is distributed in the body in proportion to the water content of the tissues
- i.e. liver and brain will have higher concentration bc they have higher water content
- bone and fat have less alcohol distribution bc of lower water content
what is the widmark factor (r)
r = conc of body alcohol / conc of blood alcohol
what is R for males and females
males: 0.7
females: 0.6
what does BAC depend on?
- body size (weight)
- body fat (body type)
- gender
would a person weighing 160lbs or 240lbs have higher BAC if they drank the same
the smaller one (160 lbs)
if 2 people weighed the same (but one had higher fat content), and had the same number of drinks, who would have higher BAC?
fat guy
if a man and woman weighing the same had the same drinks, who has higher BAC
woman bc they tend to have higher fat content
What is the formula for absorption?
Absorption = BAC x weight x 0.022
x 6/7 for females
describe the metabolism of alcohol
90-98% occurs in the liver
alcohol -> acetaldehyde -> acetate -> cO2 and H2O
how is metabolism of alcohol affected if you are an alcoholic
if you are an alcoholic, you will eliminate it a little bit faster
describe excretion of alcohol
2-10% is eliminated unchanged (breath, urine, faces, sweat, tears, saliva)
What does elimination = ?
elimination = metabolism + excretion
Formula for elimination?
elimination = weight/70 x 25 x T
T = hours since first drink
if wine or beer are involved, how do you account for this?
if it’s beer, you do 40/5
mL beverage = 40 / conc of alcohol in beverage x mL liquor
What is the rate of elimination in mg%/hour?
15mg%/hour
(average 10-20mg%/hour)
- regardless of height, weight, gender or amount of fatty tissue
- alcoholics can have 25mg%/hour
how can we use 1 BAC to calculate another BAC
BAC1 = BAC2 = (T x 15)
T = elapsed time from measured BAC
