Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: John P. Laurent x
  • By Author: Simeone, Frederick A. x
Clear All Modify Search
Restricted access

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.

Restricted access

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.

Restricted access

Frederick A. Simeone, John P. Laurent, Peter J. Trepper, Daniel J. Brown and John Cotter

✓ Intermittent occlusion of the descending aorta just below the origin of the brachiocephalic vessels by a preformed balloon passed via the femoral artery is capable of significantly increasing the pressure and flow in the common carotid artery. Regional cerebral blood flow determination by the krypton-85 washout technique measured maximum increases of over 40% of the controls, which could easily be achieved and maintained. This technique apparently takes advantage of the finite delay in autoregulatory response to the increased arterial pressure before the onset of maximal autoregulation. Dogs were “pumped” in this way for up to 18 hours and survived in good health. Principal problems with this technique were the development of cerebral edema in the presence of diffuse established cerebral anoxia, and a shock-like cardiovascular response if the intermittent aortic occlusion was discontinued too abruptly. The clinical application of this technique to cerebral ischemia secondary to postoperative vasospasm may not require the extremes of hyperperfusion used in these experiments.