Blood gas coefficient
The Blood Gas Partition Coefficient is also known as Ostwald coefficient for
blood–gas. A partition coefficient is the ratio of the concentrations of a
compound in one solvent to the concentration in another solvent at equilibrium.
The blood/gas partition coefficient describes how the gas will partition itself
between the two phases after equilibrium has been reached. For example:
Enflurane has a blood/gas partition coefficient of 1.7. Therefore, if the gas is in
equilibrium the concentration in blood will be 1.7 times higher than the
concentration in the alveoli. Thus, it makes sense that a gas with a higher blood
gas coefficient will require higher uptake of gas into the blood and induction will
be slower.
Key points:



Higher partition coefficient = higher lipophilicity = higher potency = higher
solubility
High solubility = more anesthetic needs to be dissolved = slower onset
MAC decreases as blood gas partition coefficient increases, generally
speaking