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John P. Laurent, Pablo Lawner, Frederick A. Simeone and Eugene Fink

✓ Barbiturates were administered to normal dogs, establishing an isoelectric electrocorticogram. Cortical cerebral blood flows (CBF) and deeper CBF's were respectively measured by krypton-85 (85Kr) and xenon-133 (133Xe). Following barbiturate administration, the two methods of measuring CBF showed a poor coefficient of variation (r = 0.12, p < 0.05). The cortical flows decreased less than the fast compartment flows. A shifting of percentage contribution of flow to the slow compartment (60% increase, p < 0.001) was observed after barbiturate infusion. A selective shunting of blood flow to the slower areas may explain the lowering of intracranial pressure and protection of the deep white matter observed by many authors who use barbiturates in clinical and experimental situations.

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Hypervolemic hemodilution in experimental focal cerebral ischemia

Elevation of cardiac output, regional cortical blood flow, and ICP after intravascular volume expansion with low molecular weight dextran

James H. Wood, Frederick A. Simeone, Eugene A. Fink and Michael A. Golden

✓ Cerebrovascular and cardiac alterations evoked by intravascular volume expansion with low molecular weight dextran (LMD, molecular weight 40,000), an advocated adjunct in the clinical prevention or therapy of acute stroke and cerebral vasospasm, were studied in splenectomized dogs. Clipping of the right distal internal carotid artery and the proximal middle cerebral artery (MCA) in eight dogs decreased regional cortical blood flow (rCoBF) by 58% without changing cardiac output (CO), and caused 10% ± 5% (SE) hemispheric infarction. Ten other dogs underwent similar cerebral arterial occlusion and were infused twice with LMD within 2 hours; each infusion equaled 20% of the respective dog's total blood volume. Both CO and rCoBF in the territory of the occluded MCA increased significantly by 119% ± 13% and 42% ± 6%, respectively, following the two LMD infusions. Although the mean arterial blood pressure was unaltered, the hematocrit decreased significantly and the intracranial pressure (ICP) increased significantly. The mean hemispheric infarction in these 10 treated dogs was 4% ± 2%. Another nine dogs underwent arterial manipulation without clipping. Two hemodiluting LMD infusions, similar to those in the 10 dogs, significantly elevated CO and ICP but not rCoBF. These data suggest that hypervolemic hemodilution with LMD effectively elevates collateral perfusion to ischemic regions of brain distal to occluded MCA segments and concomitantly raises the CO and ICP.

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Pablo M. Lawner, John P. Laurent, Frederick A. Simeone and Eugene A. Fink

✓ Ninety-three mongrel dogs underwent intracranial carotid and middle cerebral artery occlusions. They were then randomized into four groups: 1) the untreated control group (no surgical or medical therapy) showed significant neurological deficit, 16% mortality, and 17% mean hemisphere infarction; 2) in the bypass group (superficial temporal to middle cerebral artery (STA-MCA) anastomosis completed within 3 hours of occlusion), neurological deficit was diminished, mortality was 7%, and mean infarction 5.66%; 3) in the pentobarbital group (single dose of pentobarbital, 35 mg/kg administered intravenously 30 minutes after occlusion), neurological deficit was essentially the same as in the previous group, there was no mortality, and mean infarction was 5.52%; and 4) in the pentobarbital/bypass group (pentobarbital dose plus STA-MCA bypass), neurological deficit was slightly lower than in previous treatment groups, there was no mortality, and mean hemisphere infarction was 1.78%. Extracranial-intracranial bypass produced an immediate 31.6% increase in regional cortical blood flow. The combination of pentobarbital postocclusive therapy and early extracranial-intracranial bypass showed beneficial synergism.