Reperfusion injury

When there is an infarction to a particular tissue it is necessary to reestablish the perfusion to that tissue as soon as possible. When the perfusion is reestablished sometimes the tissue damage can be recovered and the tissue starts to function normally. But the reperfusion itself can cause tissue damage. This is against the general public idea held by many people that reperfusion does no cause any injury. When an artery is blocked by a thrombus various drugs (Streptokinase) are given to dissolve this clot and re establish the circulation. But when the circulation is reestablished free radicals can be formed in the ischemic tissue and can cause tissue damage. This may be due to the fact that functions of the organelles of the many ischemic cells are impaired and these organelles produce free radicals. For an example when streptokinase is given to a patient with a myocardial infarction sudden spike of CPK enzyme level can be seen in the CPK enzyme test.