Purpose: Blood lactate concentration does not correspond well to oxygen transport variables during circulatory shock. Prolonged washout of lactate from tissues during shock has been reported. This study was designed to test the hypothesis that the discrepancy between serum lactate and oxygen metabolism is caused by the failure of lactate to wash out from the tissues and that tissue lactate may reflect the oxygen metabolism better.
Methods: Using a canine model of hemorrhagic shock, lactate concentration measured in a muscle biopsy specimen and in arterial blood was compared with the cumulative deficit in oxygen consumption.
Result: The cumulative deficit in oxygen consumption correlated with the concentration of lactate in muscle (r= 0.67,P<0.01) but not with that in blood. During shock, all muscle lactate levels were greater than those in serum, and a linear relationship was demonstrated between arterial(X) and muscle(Y) lactate levels (Y=2.45X-2.72,r=0.82,P<0.001). The muscle/serum lactate concentration ratio increased from 1 to 2.5 as the blood volume decreased.
Conclusion: In the setting of experimental hemorrhagic shock, only tissue lactate levels reflected the true deficit in oxygen metabolism. The difference between lactate levels in muscle and serum represented the severity of the shock.
Keywords: Cumulative deficit in oxygen consumption; Hemorrhagic shock; Lactate concentration; Muscle/serum lactate concentration ratio; Washout of lactate.