Mechanisms of edema formation after intracerebral hemorrhage - Effects of extravasated red blood cells on blood flow and blood-brain barrier integrity

Background and Purpose-Red blood cell (RBC) lysis contributes to brain edem a formation after intracerebral hemorrhage (ICH). and RBC hemolysate (oxyhe moglobin) has been implicated to be a spasminogen in subarachnoid hemorrhag e. Whether cerebral ischemia contributes to brain edema formation after ICH remains unclear, however. The aims of this study were to test whether extr avasation of RBCs induces cerebral ischemia and/or blood-brain barrier disr uption in a rat ICH model characterized by perihematomal brain edema. Methods-In this study. 87 pentobarbital-anesthetized Sprague-Dawley rats we re used. In each animal, saline, packed right caudate nucleus. Sham injecti ons served as controls. Regional cerebral RBCs, or lysed RBCs were injected into the right caudate nucleus. Sham injections served as controls. Region al cerebral blood flow, brain water and ion contents, blood-brain barrier i ntegrity, and plasma volume were measured. Results-Intraparenchymal infusion of lysed RBCs caused severe brain edema b y the first day but did not induce ischemic cerebral blood flows. In contra st, blood-brain barrier permeability increased during the first day after i nfusion of lysed RBCs (a 3-fold increase) and 3 days after infusion of pack ed RBCs (a 4-fold increase). Conclusions-These results suggest that ischemia is not present at 24 or 72 hours after hematoma induction by injection of intact or lysed RBCs. RBC co nstituents that appear after delayed lysis, however. increase blood-brain b arrier permeability. which contributes to edema formation.