The Effect of Hypervolemic Hemodilution with and without Hypertension on Cerebral Blood Flow Following Middle Cerebral Artery Occlusion in Rats Anesthetized with Isoflurane

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Abstract
The effect of hypervolemic hemodilution or hypervolemic hemodilution with dopamine-induced hypertension on cerebral blood flow (CBF) was investigated during 1.2 MAC isoflurane anesthesia in rats (n = 24) subjected to middle cerebral artery occulsion (MCAO). Prior to MCAO each animal was randomized to one of the following groups: 1) control, mean arterial pressure (89 .+-. 10 mmHg [mean .+-. SD]), blood volume, and hematocrit (46 .+-. 1) were not manipulated; 2) hypervolemic hemodilution (HH), 30 min before MCAO, 5% albumin was administered to reduce the hematocrit to 29-32%; or 3) hypervolemic hemodilution/dopamine hypertension (HH/Dop), hemodilution was accomplished and dopamine (10 .mu.g .cntdot. kg-1 .cntdot. min-1- was infused during the ischemic period to acheive a mean arterial pressure of 111 .+-. 10 mmHg (mean .+-. SD). Ten minutes after occlusion of the left middle cerebral artery, CBF was determined using 14C-iodoantipyrine. Five coronal brain sections were analyzed to determine the area within each grain section with CBF ranges of 0-15 ml .cntdot. 100 g-1 and 15-23 ml .cntdot. 100 g-1 .cntdot. min-1. The area of 0-15 ml .cntdot. 100 g-1 min-1 CBF was less in both the HH and HH/Dop groups compared with control (P < 0.05). The area of 15-23 ml .cntdot. 100 g-1 min-1 CBF was less in the HH group but not the HH/DOP group compared with control. In a section through the center of middle cerebral artery distribution, the area of the hemisphere ipsilateral to MCAO with CBF of 0-15 ml .cntdot. 100 g-1 .cntdot. min-1 (mean .+-. SD) was 32 .+-. 6% in the control group, 8 .+-. 3% in the HH group, and 11 .+-. 4% in the HH/Dop group. The area with CBF of 15-23 ml .cntdot. 100 g-1 .cntdot. min-1 was 31 .+-. 6% in the control group, 18 .+-. 5% in the HH group, and 24 .+-. 6% in the HH/Dop group. In summary, hypervolemic hemodilution reduced the area of hypoperfusion during focal cerebral ischemia. The addition of dopamine (10 .mu.g .cntdot. kg-1 .cntdot. min-1) did not further reduce the area of hypoperfusion. CBF in the hemisphere contralateral to MCAO was not altered by therapy in any group.