Expert: Dr Ian Jackson - please note UK based - 12/5/2006

Question
Can you give me an example of how simple math (arithmetic, multiplication, division, basic algebra, and geometry) is used day to day in the field of anesthesiology? Thank You. -Sean

Answer
Hi Sean
This sounds a bit like homework to me!
Most drugs in anaesthesia are given on the basis of complicated pharmacokinetics which is basically based on what our bodies do to drugs.
So these are calculated on volunteers and we end up with dosage regimen based on milligrams per kg or micrograms per kg or even micrograms per kg per minute.
How drugs are removed from the body is also imprtant to us
Elimination half life (t1/2): the time taken for plasma concentration to reduce by 50%.
FACT
After 4 half lives, elimination is 94% complete.

It can be shown that the kel = the log of 2 divided by the t1/2 = 0.693/t1/2.

Likewise, Cl = kel x Vd, so, Cl = 0.693Vd/t1/2.

And t1/2 = 0.693 x Vd / cl

Confused?
Then have a look at http://www.4um.com/tutorial/science/pharmak.htm for a working example.

Now geometry I struggle to see a link!
Hope this helps a bit
Ian