Alcohol and the body
Print this article
Calculations using blood alcohol curve
Using a blood alcohol curve it is possible to
estimate the following:
- blood alcohol level at a given time based upon an indicated
consumption scenario
- quantity of alcohol required to produce a known blood alcohol
level at a given time
- blood alcohol concentration at a time previous to sample collection
(retrograde extrapolation), or at a time subsequent to sample
collection (anterograde extrapolation)
To accurately estimate each of the above, knowledge
of certain factors is required. These may include:
- sex
- age
- height
- weight
- consumption start time and stop time
- pattern of drinking
- type of alcohol consumed including number of drinks, size
and alcohol content
- time for which BAC is being calculated (or BAC value(s) detected
if a retrograde or anterograde extrapolation is required)
- times meals eaten
- disease states
- any medications that were taken
This data combined with the empirical factors
derived from scientific studies, such as average rates
for alcohol absorption, distribution and elimination provides
the basis for the estimates noted above.
To approximate your blood alcohol level at a particular point in time use the Calculator.
BAC Reporting Conventions
The Criminal Code of Canada reports the legal
limit for alcohol as 80 milligrams of ethyl alcohol per 100 millilitres
of blood (80 mg%). This is also often expressed as 0.08 grams
of ethyl alcohol per 100 millilitres of blood.
In the clinical world, concentrations of substances
are reported using the Systeme Internationale system of measurement.
Hence, millimoles per litre. One millimole of ethyl alcohol per
litre of blood is equivalent to 4.61 milligrams of ethyl alcohol
per 100 millilitres of blood. As a result, 80 mg% is equivalent
to 17.3 millimoles of ethyl alcohol per litre of blood.
Mg%: Milligrams of ethyl alcohol in 100 millilitres
of blood.
Serum/Plasma versus Whole Blood
Hospital analysis of blood samples for ethyl
alcohol content is often based upon serum or plasma as the sample
matrix.
Plasma is the liquid portion of the circulating
blood (whole blood).
Serum is the liquid remaining after the red blood
cells are removed by some mechanical means, such as centrifugation.
Serum contains slightly more water than whole blood and hence
will have a slightly higher alcohol level than whole blood.
Scientific studies have shown that serum will
contain more alcohol than whole blood by a factor of 1.08:1 to
1.18:1, or on average, 1.12:1. As a result, a serum alcohol level
of 108-118 mg% would be equivalent to an alcohol level of 100
mg% in whole blood.
Disclaimer: The material on this site is not intended as legal advice. It merely conveys general information on legal issues commonly encountered by persons facing criminal charges in Canada. If you are charged with an offence, you should contact a criminal lawyer.
| 
