Hypervolemic-hemodilution and hypertension during temporary middle cerebral artery occlusion in rats: the effect on blood-brain barrier permeability.

The effect of hypervolemic-hemodilution, with and without hypertension, on blood-brain barrier permeability was investigated in rats, after 180 minutes of middle cerebral artery occlusion (MCAo), and 60 minutes of reperfusion. One of the following conditions was maintained during MCAo: 1) Control--hematocrit and blood pressure were not manipulated; 2) Hypervolemic-Hemodilution/Normotension--the hematocrit was decreased to 30%; 3) Hypervolemic-Hemodilution/Hypertension--the hematocrit was decreased to 30% and mean arterial pressure increased by 30 mmHg with phenylphrine. In all groups, Evans Blue was administered, and its concentration determined by spectrophotometric assay. Evans Blue (micrograms (g-1 of brain tissue [mean +/- SD]) was greater in the Hypervolemic-Hemodilution/Hypertension group (71 +/- 20) versus the Control (13 +/- 9) and Hypervolemic-Hemodilution/Normotension (17 +/- 10) groups (p less than 0.05). No other differences were present. These results support the hypothesis that during MCAo, hypervolemic-hemodilution/hypertensive therapy effects an increase in blood-brain barrier permeability in the early period of reperfusion.