[The influence of volume expansion with induced hypertension on vessel reactivities, blood-brain-barrier, cerebral edema and infarction].

Eighteen anesthetized cats were randomly divided into 3 groups. One group was treated with 10 ml/kg of 6% hydroxyethyl starch (HES). Another group was treated with 15 ml/kg, and there was a control group. There were six cats in each group. Cerebral pial arterial reactivities were measured by means of intravital microscopic observation through a cranial window. Middle cerebral artery (MCA) was clipped for 70 minutes using a transorbital approach. Five hours later, Evans blue dye was injected intravenously and then the animals were killed. Administration of HES or Ringer's solution (control) was started 15 minutes before clipping of MCA. Systemic arterial pressure was elevated by using dopamine at the same time as the MCA occlusion was carried out. Pial arteries dilated soon after the clipping of MCA in all three groups, but showed different patterns in each group after recirculation of MCA. In the control group, they returned to 20% of their dilated state first, but, after about 4 hours, they redilated by 45% at the end of experiment periods. In the group treated with 10 ml/kg of 6% HES, they remained in an almost resting state after MCA recirculation, but in the group with 15 ml/kg, they constricted by 10% at the end of the experiment periods. Regarding the Evans blue dye extravasation, cerebral edema and infarction, they were largest in the control group. But animals treated with 15 ml/kg of 6% HES showed significantly larger Evans blue dye extravasation and cerebral edema than that of animals with 10 ml/kg. However cerebral infarctions were almost the same sizes in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)