Quantification of damage to striated muscle after normothermic or hypothermic ischemia.

Muscular ischemia of different duration was induced by use of a tourniquet applied to the rear left leg of rabbits under normothermic or hypothermic conditions, and variations in serum creatine kinase, lactate dehydrogenase, K+, Ca2+, and lactate were determined at various intervals after blood flow was restored. A monocompartmental model analysis applied to the activities of the two enzymes in the serum demonstrated that: (a) the total enzyme activity leaked into the blood is proportional to the duration of normothermic but not of hypothermic ischemia; (b) this enzyme leakage persists until at least the third day after blood flow is restored; (c) a substantial part of the ischemic damage seems to occur as a consequence of re-perfusion, not of the ischemia itself; and (d) hypothermia greatly minimizes the ischemic damage. The data we obtained for K+ and for lactate confirm the protective effect of hypothermia.