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

We determined regional cerebral blood flow (rCBF) using [125I]HIPDm [N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3-propanediamin e] and [125I]iodoantipyrine autoradiography under control and pathologic conditions (hypercapnia [acidosis], hypocapnia [alkalosis], and disrupted blood-brain barrier) conditions in 35 rats. In control rats, HIPDm rCBF (indicator fractionation method, n = 5) was lower than the corresponding IAP rCBF (diffusible indicator method, n = 4), most notably in the infratentorial regions and subcortical nuclei. In hypercapnia, rCBF increased by 100% and 37% in the HIPDm (n = 5) and IAP (n = 5) groups, respectively. In hypocapnia, IAP rCBF (n = 4) decreased 34% but HIPDm rCBF (n = 4) did not change. Following disruption of the blood-brain barrier by intracarotid infusion of mannitol in eight rats, both radiotracers (HIPDm n = 4, IAP n = 4) showed decreased rCBF to regions of disruption as defined by trypan blue extravasation. Our work indicates that modeling HIPDm uptake to quantify rCBF using the indicator fractionation method will underestimate blood flow and that HIPDm kinetics are influenced by compartmental pH dynamics that will limit the accuracy of this method in quantifying rCBF in pathologic conditions.
Stroke 1988 Nov
PMID:Comparison of [125I]HIPDm and [125I]iodoantipyrine in quantifying regional cerebral blood flow in rats. 318 25

The presence and distribution of a cerebrovascular cholinergic system were studied in goats. Regional cerebral blood flow was measured in the parietal cerebral cortex, caudate nucleus, and white matter by the hydrogen clearance technique in unanesthetized goats. Intravenous low doses of physostigmine, but not of neostigmine, significantly increased regional blood flow without changing mean arterial blood pressure or behavior. Increases of blood flow were greater in cerebral cortex and caudate nucleus than in white matter although the vasodilation induced by hypercapnia was similar in the three regions. Intracerebral microvessels were isolated from cerebral cortex, caudate nucleus, and white matter to evaluate choline acetyltransferase activity as a marker for perivascular cholinergic nerves. The enzyme level was higher in vessels from cerebral cortex and caudate nucleus than in vessels from white matter, which is in accordance with the functional data. These results suggest the presence of a cholinergic perivascular innervation system in intracerebral microvessels. Such innervation has a nonhomogeneous distribution throughout the brain and might be implicated in the local regulation of cerebral blood flow.
Stroke 1988 Jun
PMID:Regional differences in cerebrovascular cholinergic innervation in goats. 337 65

Cerebral blood flow and oxygen metabolism have been measured with the steady-state oxygen-15 technique and positron emission tomography in anesthetized dogs. Regional microembolization was induced by infusing Sephadex particles (diameter, 40 micron) into one of the common carotid arteries. In the first series of experiments, 2.5 mg Sephadex was infused, and the dogs were examined within 3-4 hours after embolization. In a second series 0.55 mg Sephadex was infused, and the dogs were examined either in the first 3-4 hours or 24-48 hours after embolization. Cerebral blood flow, oxygen extraction ratio, and cerebral oxygen utilization were measured at 3 PCO2 levels. In the acute experiments, cerebral oxygen utilization in the embolized hemisphere was 6 (0.55 mg Sephadex) and 25% (2.5 mg Sephadex) lower than on the contralateral side. While cerebral blood flow was symmetrically distributed in normocapnia and hypocapnia, it was 9 (0.55 mg Sephadex) and 35% (2.5 mg Sephadex) lower in the embolized hemisphere during hypercapnia. In normocapnia and hypocapnia the lower oxygen utilization in the embolized hemisphere was characterized by a lower oxygen extraction ratio, and in hypercapnia by an unchanged (0.55 mg Sephadex) or by a higher (2.5 mg Sephadex) extraction ratio. The different effect on oxygen extraction ratio in the control and embolized hemispheres resulted in images of uncoupling between perfusion and oxygen demand that varied according to the PCO2. The experiments also showed a fall in cerebral blood flow in the embolized hemisphere after 3-4 hours, indicating delayed hypoperfusion. After 24-48 hours, blood flow was about 10% higher in the embolized hemisphere, and this was observed at the 3 PCO2 levels, while the oxygen extraction ratio was systematically lower. Oxygen utilization in the embolized hemisphere was depressed to practically the same extent as in acute experiments. It can be concluded that between 4 and 24 hours after microembolization the cerebral microcirculation shows important changes, with installation of luxury perfusion in the face of an unchanging decreased oxygen metabolism.
Stroke
PMID:PET studies of changes in cerebral blood flow and oxygen metabolism after unilateral microembolization of the brain in anesthetized dogs. 349 88

Dantrolene sodium acts primarily by affecting calcium flux across the sarcoplasmic reticulum of skeletal muscle. Recently, dantrolene has been used very successfully in the treatment of several rare hypercatabolic syndromes which have previously been associated with high mortality rates. In malignant hyperthermia, where early diagnosis and treatment usually with intravenous dantrolene in association with other supportive measures (and often subsequent dantrolene therapy) is performed, recovery is seen in virtually 100% of patients. There is a rapid resolution of hyperthermia, dysrhythmias, muscle rigidity, tachycardia, hypercapnia, mottled or cyanotic skin, and metabolic acidosis, and a slower normalisation of myoglobinuria and elevated serum creatine phosphokinase levels. In patients with family history or previous episodes of malignant hyperthermia, prophylactic treatment with dantrolene prior to anaesthesia prevents the syndrome occurring in most cases. Where malignant hyperthermia has developed patients have been successfully treated with further dantrolene therapy. Dantrolene has also been used successfully in the treatment of a few cases of heat stroke and the neuroleptic malignant syndrome--both of which have many similarities to malignant hyperthermia. Dantrolene is well established in the treatment of patients with muscle spasticity where it generally improves at least some of the components of spasticity (i.e. hyper/hypotonia, clonus, muscle cramps and spasms, resistance to stretch and flexor reflexes, articular movement, neurological and motor functions and urinary control). However, in some patients, particularly those with multiple sclerosis, dantrolene may not be effective, and in many cases muscular strength may diminish. Long term dantrolene therapy has been associated with hepatic toxicity and may cause problems in patients treated for disorders of muscle spasticity. Thus, dantrolene offers a unique advance in the therapy available for the treatment of hypercatabolic disorders and is also useful in the treatment of muscle spasticity of various aetiology.
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PMID:Dantrolene. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in malignant hyperthermia, the neuroleptic malignant syndrome and an update of its use in muscle spasticity. 352 59

Due to methodologic difficulties, few investigations have been made on the blood flow velocity in the cerebral microcirculation. Using a newly developed video camera method, we simultaneously measured the blood flow velocity and diameter of pial arteries during hemorrhagic hypotension, after blood pressure recovery, and during CO2 inhalation in cats. When the mean arterial blood pressure was lowered from 129.7 +/- 6.6 to 71.5 +/- 4.1 mm Hg, the blood flow velocity inevitably decreased from 36.6 +/- 5.3 to 27.0 +/- 3.9 mm/sec (p less than 0.001). The calculated blood flow rate [pi X (diameter/2)2 X flow velocity] was preserved in cases with concomitant vasodilation. Conversely, the blood flow velocity increased from 25.3 +/- 5.1 to 31.0 +/- 5.4 mm/sec (p less than 0.001) after mean arterial blood pressure recovery from 67.1 +/- 3.7 to 129.8 +/- 5.8 mm Hg. The blood flow rate was again preserved in vessels with a vasoconstrictive response. Each pial artery apparently dilated or constricted in proportion to the decrease or increase in flow velocity during blood pressure changes, maintaining a constant cerebral blood flow. This indicated the importance of the pial arteries in the mechanisms of cerebral blood flow autoregulation. During 5% CO2 inhalation, the blood flow velocity increased markedly from 25.4 +/- 4.6 to 37.2 +/- 10.0 mm/sec (p less than 0.05), while the pial artery diameter (85.0 +/- 13.7 microns) increased by 9.6 +/- 1.5% (p less than 0.01). The increased flow velocity might be attributable to preferential dilatation of small arterioles or intraparenchymal vessels during hypercapnia.(ABSTRACT TRUNCATED AT 250 WORDS)
Stroke
PMID:Quantitative measurement of blood flow velocity in feline pial arteries during hemorrhagic hypotension and hypercapnia. 356 4

A thermal clearance technique for measuring cerebral blood flow is described and compared with the radiolabelled microsphere technique. The thermal technique involves measurement of the rewarming curve generated after bolus infusion of 4-5 ml of ice-cold saline into the common carotid artery with a subdural thermistor placed on the parietal cortex. Evaluation of the biexponential decay curves obtained with this technique demonstrated a close correlation with total hemispheric, parietal, and parietal gray blood flow determined by simultaneous microsphere measurement. Despite significant correlations (p less than 0.001), scatter in the data produced a broad 95% confidence interval, thus making interpretation of blood flow with the thermal clearance technique impossible. Furthermore, instrumentation with the thermal probe, which required opening of the dura, blunted the cerebral blood flow response to hypercapnia. We conclude that the major limitations of the thermal clearance technique include: nonhomogeneous clearance function, significant variability, and depression of CO2 reactivity. These limitations must be addressed before this technique can be used reliably in the laboratory.
Stroke
PMID:Comparison of thermal clearance measurement of regional cerebral blood flow with radiolabelled microspheres. 359 Feb 53

Our previous experiments have shown that thromboxane A2 is a strong contractor of cerebral arterial smooth muscle strips. The objective of these experiments was to determine if U 46619, a stable thromboxane A2 mimetic, affects the cerebral microcirculation in vivo. Pial arteriole diameter in rabbits and rats was measured with a microscope using the closed cranial window technique. Topical application of 10(-11) to 10(-6) M U 46619 induced dose-dependent arteriole vasoconstriction in both species. In rabbits and rats the maximum vasoconstriction was 9.7 +/- 1.3% (mean +/- SEM) and 14.0 +/- 0.5%, respectively. In rats, 10(-7) and 10(-6) M U 46619 induced intravascular platelet aggregation accompanied by a further decrease in diameter and transient occlusion of the arterioles and venules. U 46619 had no significant effect on rabbit pial arterioles that were predilated by hypercapnia or hypercapnia plus hypoxia. Our data suggest that in animals with a normal vasculature, thromboxane A2 may be a moderate constrictor of cerebral arterioles and that this constrictor effect is prevented by hypercapnia and hypoxia.
Stroke
PMID:Effect of the thromboxane A2 mimetic U 46619 on pial arterioles of rabbits and rats. 360 7

Acute respiratory acidosis results in increases in cardiac output and in systemic and pulmonary arterial blood pressures. The aim of this investigation was to determine if isoflurane modifies these effects. Nine patients (ASA II or III) scheduled for major surgery took part in the investigation. After the induction of general anesthesia, CO2 was added to the inspiratory gas mixture. After 15 min, ventilation with addition of CO2 (PaCO2 8-9 kPa) isoflurane (3%) was added. Hemodynamic measurements were made to study the effects of acute hypercapnia and the effects of isoflurane during hypercapnia. The addition of carbon dioxide resulted in increases in cardiac output, systemic and pulmonary arterial blood pressures, and right and left ventricular stroke work. The addition of isoflurane during hypercapnia decreased systemic arterial blood pressure, but pulmonary arterial blood pressure was unaffected, cardiac output and stroke volume did not change, and left but not right ventricular stroke work decreased. In conclusion, acute pulmonary hypertension induced by hypercapnia was not affected by isoflurane but, despite increased right ventricular stroke work, there were no signs of right ventricular failure.
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PMID:Circulatory effects of isoflurane during acute hypercapnia. 368 95

Measurement of intracranial arterial blood flow velocity is a new technique with potentially a number of very useful applications. This study validates the technique by comparing it to cerebral blood flow (CBF) measured using intravenous Xenon133 and extracranial clearance recording. We have measured the middle cerebral artery (MCA) blood flow velocity in 17 symptomatic patients with the EME TC 264 transcranial Doppler velocimeter and compared these measurements to the ipsilateral hemispheric cerebral blood flow measured with an intravenous Xenon133 technique (Novo Cerebrograph 10A). Measurements were made at rest and during hypercapnia. The absolute measurement of MCA velocity and hemispheric CBF showed a poor correlation (r = 0.424, p less than 0.01) due to wide between-patient variations at rest but the blood flow response to hypercapnia, expressed as a reactivity index, showed a good correlation (r = 0.849, p less than 0.001). Thus changes in MCA velocity reliably correlate with changes in cerebral blood flow but the absolute velocity cannot be used as an indicator of CBF.
Stroke
PMID:Transcranial Doppler measurement of middle cerebral artery blood flow velocity: a validation study. 376 63

To test the hypothesis that the putative noradrenergic innervation of intraparenchymal cerebral blood vessels from the nucleus locus ceruleus mediates the vasodilatory response to hypercapnia, regional cerebral blood flow was measured by iodo-[14C]antipyrine autoradiography in awake and restrained rats with unilateral 6-hydroxydopamine lesion of the nucleus locus ceruleus and in unlesioned control rats. Hypercapnia, induced by the inhalation of 5% or 8% CO2 in air for 8 minutes caused a 2 to 5-fold increase in regional cerebral blood flow. However, despite a marked reduction of about 90% in cortical norepinephrine levels ipsilateral to the lesion, blood flow to the frontal and parietal cortex, hippocampus, striatum and cerebellum increased to the same extent in ipsilateral and contralateral regions. Thus, lesion of the locus ceruleus and the resultant depletion of endogenous cortical and hippocampal norepinephrine, does not influence the cerebrovascular response to hypercapnia.
Stroke
PMID:Increased cerebral blood flow during hypercapnia is not affected by lesion of the nucleus locus ceruleus. 381 Jul 25


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