Secondary Bleeding During Acute Experimental Intracerebral Hemorrhage.

Background and Purpose- Mechanisms contributing to acute hematoma growth in intracerebral hemorrhage are not well understood. Neuropathological studies suggest that the initial hematoma may create mass effect that can tear vessels in the vicinity by shearing, causing further bleeding and hematoma growth. Methods- To test this in mice, we simulated initial intracerebral hemorrhage by intrastriatal injection of a liquid polymer that coagulates upon contact with tissue and measured the presence and volume of bleeding secondary to the mass effect using Hemoglobin ELISA 15 minutes after injection. Results- Secondary hemorrhage occurred in a volume-dependent (4, 7.5, or 15 μL of polymer) and rate-dependent (0.05, 0.5, or 5 μL/s) manner. Anticoagulation (warfarin or dabigatran) exacerbated the secondary hemorrhage volume. In a second model of hematoma expansion, we confirmed that intrastriatal whole blood injection (15 μL, 0.5 μL/s) also caused secondary bleeding, using acute Evans blue extravasation as a surrogate. Anticoagulation once again exacerbated secondary hemorrhage after intrastriatal whole blood injection. Secondary hemorrhage directly and significantly correlated with arterial blood pressures in both nonanticoagulated and anticoagulated mice, when modulated by phenylephrine or labetalol. Conclusions- Our study provides the first proof of concept for secondary vessel rupture and bleeding as a potential mechanism for intracerebral hematoma growth.