Fibrinolytic activity in experimental intracerebral hematoma

In an attempt to investigate the role of tissue fibrinolytic activity in the resolution of intracerebral hematoma, an experimental model of intracerebral hematoma was developed in the rat. The fibrinolytic activity was studied using a histochemical fibrin slide technique. A total of 59 adult male rats were studied. Twenty-nine rats were used for developing the intracerebral hematoma model via injection of autologous whole blood into the left frontal lobe; in the remaining 30 rats, the intracerebral hematomas were studied sequentially. Intracerebral hematoma formation was unsuccessful in six (21%) of 29 rats. Four rats died in the immediate postoperative period and two showed no intraparenchymal clot. Intense fibrinolytic activity was demonstrated in the blood vessel walls of the normal brain, especially in the meninges, choroid plexus, and ependymal cell layer. In the initial stages of hematoma resolution, fibrinolytic activity was not seen in the hematoma or parenchyma except in the preexisting blood vessels. However, 3 to 5 days later, fibrinolytic activity was observed in the capillary buds surrounding the hematoma and among the infiltrating mononuclear cells. This activity increased for 7 to 10 days following formation of the hematoma and decreased after 21 to 28 days. It is concluded that tissue fibrinolytic activity associated with newly formed blood vessels appears to be important in lysis of intracerebral hematomas.