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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Measurement of regional cerebral blood flow (rCBF) was performed in 6 healthy baboons during ventilation with 35% stable xenon in artificial air. rCBF was measured with the intraarterial xenon-133 method. EEG was recorded continuously. All CBF areas of interest over one hemisphere reacted in the same way. Mean flow increased during short-term exposure to stable xenon and decreased if stable xenon inhalation was continued for at least 24 minutes. EEG showed a decrease of alpha- and beta-wave patterns a short time after the start of stable xenon inhalation without further changes over the period when rCBF finally decreased. CO2 reactivity increased in most animals, and autoregulation to mild arterial hypotension was significantly impaired with increased flow. It is concluded that 35% stable xenon in artificial air increases rCBF after short-term exposure and decreases rCBF after longer exposure. EEG changes were noted after short-term exposure. rCBF and EEG recovered rapidly after the end of stable xenon inhalation.
Stroke
PMID:Effect of stable xenon in room air on regional cerebral blood flow and electroencephalogram in normal baboons. 359 Feb 58

Regional cerebral blood flow (rCBF) was measured with the xenon-133 inhalation technique in 15 patients with unilateral cerebral infarction and 12 matched controls. Measurements were performed during a standard resting baseline condition and during the performance of standardized verbal analogies and spatial line orientation tasks. Resting and activated CBF were lower in patients than in controls, and there were differences in the hemispheric pattern of activated CBF. Control subjects replicated earlier findings of asymmetric increase in CBF for the cognitive tasks, whereas patients showed abnormalities in lateralized CBF changes consistent with side of infarction. These findings underscore the utility of cognitive challenges in the study of rCBF in stroke. This can lead to an experimental paradigm in clinical studies of the relation between behavioral deficits and regional brain dysfunction and may also improve the utility of CBF measurements in clinical settings.
Stroke
PMID:Regional cerebral blood flow in stroke: hemispheric effects of cognitive activity. 360 4

Autoregulation of cerebral (CBF) and cerebellar blood flow (CeBF) was studied before, during and after acutely induced cerebral ischemia in spontaneously hypertensive rats. Cerebral ischemia of the supratentorial portion was induced for one hour by bilateral carotid artery ligation (BCL). The animals were artificially ventilated and the blood flow was measured with a hydrogen clearance technique. To test the autoregulation, the blood pressure was stepwise lowered by bleeding and maintained at a new level, i.e. 15% or 30% lower than the baseline values before, during and after cerebral ischemia. At the preischemic state, CBF and CeBF were 52.1 +/- 6.2 and 58.9 +/- 4.6 ml/100 g/min (mean +/- SEM), of which autoregulations were normally preserved. Following BCL, CBF was markedly decreased to about 10% of control value while CeBF was minimally reduced to 46.9 +/- 8.6 ml/100 g/min (80%). At the ischemic state, CBF became almost zero flow during hypotension. CeBF was also reduced to 74% and further to 58% of the resting value by 15% and 30% decrease in the blood pressure, respectively, indicating impaired CeBF autoregulation. At the 30 min post-ischemic state, CBF was recovered to 48.0 +/- 4.9 and CeBF to 53.9 +/- 5.4 ml/100 g/min. Autoregulation of CBF was still abolished, whereas CeBF was kept constant by 15% fall of blood pressure and slightly reduced to 84% by 30% hypotension, indicating almost recovery of CeBF autoregulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Stroke
PMID:Cerebral and cerebellar blood flow autoregulations in acutely induced cerebral ischemia in spontaneously hypertensive rats--transtentorial remote effect. 381 Jul 34

Operative intervention remains controversial for patients with transient nonhemispheric symptoms with occlusive disease of both the anterior and posterior cerebral circulations. In addition to the standard evaluation of these patients, we have used stable xenon-enhanced computed tomographic mapping of cerebral blood flow (Xe/CT CBF). This relatively new and potentially widely available CBF methodology, by measuring approximately 30,000 CBF values within each of three CT levels, provides a readily interpretable means of evaluating extremes of hemodynamic compromise within any or all vascular territories. In the past 30 months, Xe/CT CBF studies in 300 patients with occlusive vascular disease have identified nine patients with global low flow and nonhemispheric symptoms (vertigo, lightheadedness, and/or blurred vision). Blood pressures determined by ocular pneumoplethysmography of Gee were markedly abnormal with reduced ocular/brachial ratios. Each patient had a combination of both segmental carotid and vertebrobasilar occlusive disease. Each patient had a flow-augmenting procedure performed on the anterior circulation in an attempt to improve global flow: carotid endarterectomy (two patients), subclavian-external carotid bypass (one patient), and superficial temporal artery-middle cerebral artery bypass (six patients). In each case disabling transient symptoms were relieved. There were no operative deaths, but one stroke occurred, probably as a result of a brief period of postoperative hypotension. Postoperative Xe/CT CBF studies show a long-term improved global CBF in all patients.
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PMID:Relief of nonhemispheric symptoms in low flow states by anterior circulation revascularization: a physiologic approach. 382 Apr 2

A group of 51 neurologically normal, middle-aged and elderly volunteers (aged 35-86 years; mean age 63.24 years) with and without risk factors for stroke were given annual tests of cerebral vasomotor reactivity to assess any changes in the cerebral vascular capacitance associated with advancing age that might alter cerebral vasomotor reactivity. Cerebral vasomotor reactivity was estimated as the difference in bihemisphere gray matter CBF measured by the 133Xe inhalation method in the steady state breathing room air, followed by a second measurement during inhalation of 100% oxygen. There were significant and progressive reductions in cerebral vasomotor reactivity during the 4-year longitudinal study. Positive linear correlations were apparent between initial steady-state mean bihemisphere gray matter CBF levels and degrees of vasomotor reactivity, suggesting that the Law of Initial Value plays an important role. This should be borne in mind when analyzing scores of cerebral vasomotor reactivity. In the present communication, analysis of covariance was used to correct for influences of initial CBF levels on vasomotor responses tested while breathing pure oxygen.
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PMID:Age-related reductions in cerebral vasomotor reactivity and the law of initial value: a 4-year prospective longitudinal study. 391 37

Xenon 133 inhalation CBF studies of one hundred patients with ischemic cerebrovascular disease in the territory of the carotid artery were compared in an attempt to gain more insight into the collateral capacity, especially in those with a stenosis or occlusion of one of the major arteries. Asymmetry of the ISI values for the two hemispheres was expressed as a ratio. High ratios (greater ISI asymmetries) were found for patients with an occlusion of the internal carotid or middle cerebral artery, especially--but not exclusively--those with the more severe clinical symptoms. It also appeared that even when the patient is in a good clinical condition, an elevated ratio reflects insufficiency of the collateral supply to the affected side. The ISI values for individual patients seem to be less useful, partly due to the variable age dependency of this flow parameter.
Stroke
PMID:ISI values and interhemispheric differences in patients with ischemic cerebrovascular disease; correlations with clinical and angiographic findings. 394 84

Alterations in local CBF (LCBF) were assessed autoradiographically in the rat at several time points following photochemically induced cortical infarction. Cortical infarction of consistent size and location was produced by irradiating the brain with green light through the intact skull for 20 min following the systemic injection of rose bengal. A consistent pattern of altered LCBF was recorded in both ipsilateral and contralateral brain regions over the course of the study. At 30 min, a severely ischemic zone surrounded by regions of cortical hyperemia was apparent. LCBF was also depressed relative to control values in ipsilateral cortical regions remote from the irradiated area, while contralateral cortical structures were mildly hyperemic. By 4 h, the zone of severe ischemia had enlarged and its margins were no longer hyperemic. Ipsilateral cortical and some subcortical structures demonstrated significantly depressed levels of LCBF. At 5 days, LCBF throughout both ipsilateral and contralateral cortices was depressed compared with control values. By 15 days, LCBF had returned to control levels in most brain structures shown histopathologically not to be irreversibly damaged. The temporal sequence and magnitude of these hemodynamic alterations are consistent with findings in clinical studies in which repeated measurements of CBF have been carried out in patients with acute stroke. The ability to produce a cortical infarct that results in a consistent pattern of altered CBF should facilitate the investigation of stroke mechanisms responsible for these hemodynamic abnormalities.
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PMID:Photochemically induced cortical infarction in the rat. 1. Time course of hemodynamic consequences. 395 63

Experimental subarachnoid hemorrhage (SAH) was induced in baboons by repeated injections of autologous blood into cisterna chiasmatis and cisterna magna, a total of 14-33 ml being injected over 3-4 days. Cerebral blood flow (CBF; 133xenon clearance) and cerebral metabolic rate of oxygen (CMRO2) were measured before, and 7 days after, the first blood injection. The effect of the calcium channel blocker, nimodipine, used in a commercially available form for clinical application, was studied following continuous i.a. infusion (0.1 microgram X kg-1 X min-1) for an interval of 45 min, and also 20 and 60 min after intrathecal administration of 1 microgram X kg-1. During the infusion experiments, CBF was increased by 25-30% both before and after the cisternal blood injection. CMRO2 was also enhanced, but much less. Nimodipine in doses given did not alter systemic blood pressure. Following intrathecal application, CBF and CMRO2 slightly increased at 20 min only before experimental SAH.
Stroke
PMID:Changes in cerebral blood flow and metabolism following intraarterial or local administration of nimodipine, before and after experimental subarachnoid hemorrhage in baboons. 396 30

The effects of Nimodipine on the global and regional cerebral blood flow were studied in 42 patients with cerebrovascular disorders. In 25 patients with focal deficits such as transitory ischemic attack (TIA), prolonged reversible ischemic neurological deficit (PRIND), and minor stroke due to arteriosclerosis, and in eleven patients with cerebral vasospasm after subarachnoid hemorrhage, the cerebral blood flow was measured by 133Xenon inhalation technique 60 min after oral administration of 40, 60, or 80 mg Nimodipine. In 6 patients with vasospasm the effects of Nimodipine i.v. were examined. The result in twelve patients with minor stroke who were only given placebo (lactose; "test-retest") was identical regional (rCBF) and global (CBF) cerebral blood flow before and 60 min after; placebo, blood pressure, and arterial pCO2 remained constant as well. After Nimodipine, however, the CBF increases, the increase after vasospasm being significant when taking the pCO2 in the Wilcoxon test into account. The rCBF increases much more in the regions with low perfusion rates than in well-perfused areas. This is also observed in the patients with TIA, PRIND, or minor stroke, most clearly after oral administration of 60 mg, whereas regions with normal perfusion rates show little reaction. The blood pressure was lowered, depending on the initial pressure. There was no evidence of a steal phenomenon.
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PMID:[Effect of the Ca antagonist nimodipine on global and regional cerebrovascular circulation]. 397 74

This study examines the effect of fibrinogen and consequent blood viscosity reduction on cerebral blood flow and cellular injury following severe cerebral ischemia for 30 minutes in 78 Wistar rats. In half of these rats 10 to 15 cc's of blood was removed and replaced with a mixture of 5% albumin and autologous red blood cells maintaining a constant hematocrit but resulting in a 30% decrease in fibrinogen and corresponding reduction in viscosity. Fibrinogen reduction in a slight increase in baseline CBF and the elimination of post-ischemic hyperemia at 24 hours. Both study and control animals showed a similar decrease in CBF at 30 minutes and 2 hours. There was no significant difference in the severity of ischemic cellular change between the fibrinogen reduction group and controls, although there was a significant inverse relationship between the amount of viscosity change and severity of cellular injury within the treatment group. Fibrinogen reduction alone cannot significantly ameliorate ischemic injury in this model. Viscosity reduction therapy should include reduction of hematocrit and alteration of red cell deformability.
Stroke
PMID:Fibrinogen, blood viscosity, and cerebral ischemia. 397 56


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