HEMODILUTION AND HYPERTENSION EFFECTS ON CEREBRAL-HEMORRHAGE IN CEREBRAL-ISCHEMIA IN RATS

We determined the effect of hemodilution and hypertension on cerebral hemorrhage and brain injury in 32 rats subjected to 180 minutes of middle cerebral artery occlusion and 120 minutes of reperfusion. We divided the rats into four groups. In the control group (n=8) neither hematocrit nor blood pressure was manipulated during occlusion, in the hemodilution group (R=8) 5% albumin was administered to maintain a hematocrit of 30% during occlusion, in the hypertension group (n=8) mean arterial blood pressure was increased to 30 mm Hg above baseline during occlusion with phenylephrine, and in the hemodilution/ hypertension group (n=8) albumin and phenylephrine were employed simultaneously during occlusion. We assessed the amount of cerebral hemorrhage (as concentration of extravasated hemoglobin) spectrophotometrically and the extent of ischemic injury (as percentage of the hemisphere with deficient staining) histochemically using 2,3,5-triphenyltetrazolium chloride. Mean±SD hemoglobin concentration in the hemisphere ipsilateral to the occlusion in the hemodilution/ hypertension group (71±14 μg/g brain tissue) was significantly (p<0.05) greater than that in the hemodilution and hypertension groups (25±5 and 29±7 μg/g, respectively), hemoglobin concentrations in these two groups were in turn significantly (p<0.05) greater than that in the control group (2±3 μg/g). Mean±SD percentage of the ipsilateral hemisphere with deficient staining was significantly (p<0.05) less in the hypertension and hemodilution hypertension groups (8±3% and 11±6%, respectively) than in the control and hemodilution groups (26±8% and 26±7%, respectively). Our results are consistent with the hypothesis that, although hypertension decreases ischemic brain injury, it increases the risk of intraparenchymal hemorrhage in the injured area.