Arteriovenous concentration gradient

Arteriovenous concentration gradient Uptake of soluble anesthetics into highly perfused tissues may decrease gas tension in mixed venous blood. This can influence the rate of onset of anesthesia, since achievement of equilibrium is dependent on the difference in anesthetic tension between arterial and venous blood. 

During the induction phase of anesthesia (and the initial phase of the maintenance period), the tissues that exert greatest influence on the arteriovenous anesthetic concentration gradient are those that are highly perfused (eg, brain, heart, liver, kidneys, and splanchnic bed). These tissues receive over 75% of the resting cardiac output. In the case of volatile anesthetics with relatively high solubility in highly perfused tissues, venous blood concentration will initially be very low, and equilibrium with the arterial blood is achieved slowly. 

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