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

The hydrogen clearance method was used to measure local and total cerebral blood flow (CBF) in the rhesus monkey before and for five hours after a simulated subarachnoid hemorrhage (SAH). CBF remained stable after SAH unless SAH was associated with a fall in cerebral perfusion pressure. In addition, cerebrovascular resistance did not increase after SAH. These results suggest that vasoactive agents in fresh whole blood, and the arterial spasm they produce when added to cerebrospinal fluid (CSF), play only a limited role in the pathogenesis of ischemic encephalopathy that follows an SAH.
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PMID:The effect of a simulated subarachnoid hemorrhage on cerebral blood flow in the monkey. 0 Aug 20

Arteriolar diameters and venular erythrocyte velocities in the small pial vessels on the surface of the cat brain were measured by TV methods during induced epileptic seizures through a cranial window. Grand mal seizures maximally dilated arterioles and increased venular erythrocyte velocity up to 400%. High positive correlation existed between changes in CSF hydrogen ion concentration and pial arteriolar diameter, suggesting metabolic regulation of CBF through CSF/interstitial fluid hydrogen ion alterations during the seizure.
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PMID:Brain microvascular hemodynamic responses to induced seizures. 0 70

Myocardial cell pH was measured with 5, 5 dimethyl-2, 4-oxazolidinedione (DMO) in intact anesthetized dogs by a transient indicator dilution technique. Bolus injections of labeled DMO, vascular, extracellular and water indicators were made into the left anterior descending coronary artery, and blood samples were collected from the great cardiac vein. The steady state distribution of DMO between cells and plasma was calculated from the mean transit times of the indicator. Normal myocardial cell pH averaged 6.94 and changed by 58% of the concomitant alterations in plasma pH after infusions of acid or alkali. Myocardial ischemia induced by inflation of a balloon tip catheter in the left anterior descending coronary artery resulted in progressive decreases in cell pH to 6.59 by 1 hour. Infusions of sodium carbonate diminished intracellular acidosis. Hemodynamic studies during 4 hours of ischemia with blood pH at 7.55 to 7.60 indicated a significantly reduced left ventricular end-diastolic pressure and increased stroke volume by comparison with findings in animals given infusions of saline solution. Ventriculograms revealed improved wall motion in the ischemic segment after infusion of alkali. Precordial mapping showed a significant reduction in the number of leads with S-T segment elevation as well as in the sum of S-T segment elevations, but R wave amplitudes did not differ from those in control studies. Calculations of extracellular space, tissue water and cation content revealed a reduced gain of cell sodium ion and loss of cell potassium ion during ischemia after alkali treatment. The latter may account for the S-T segment responses, whereas enhanced ventricular performance may be related to reduced competition of hydrogen ion with calcium ion for binding sites on contractile protein.
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PMID:Myocardial ischemia and cell acidosis: Modification by alkali and the effects on ventricular function and cation composition. 0 59

A focal cryogenic lesion was made in the left superior frontal gyrus of the anesthetized macaque brain. Cerebral blood flow (CBF) was determined by the hydrogen clearance technique before and during the 4 hours following trauma. Local CBF in tissue adjacent to the lesion increased in the first half hour after the lesion was made and then decreased during the ensuing 3 1/2 hours. Local CBF in the contralateral superior frontal gyrus, as well as total CBF and oxygen consumption, were unchanged by cryogenic trauma. The spread of vasogenic edema into uninjured tissue probably accounts for the observed decrease in local CBF. This experimental model may assist in discovering therapy to alter favorably the spatial and temporal profile of pathologic CBF changes in tissue surrounding an acute lesion of the brain.
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PMID:Cerebral blood flow in the monkey after focal cryogenic injury. 10 Sep 8

The relationship between increase in water content in ischemic brain and levels of regional blood flow has been studied in 11 primates. Flows were recorded using the method of hydrogen (2-minute) clearance, from a total of 128 electrodes in cortex and white matter, and a gradation of ischemia was produced by middle cerebral occlusion transorbitally. The flows were reduced in the area of densest ischemia from control levels of 12.0 +/- 12.0 ml/100g/min to 7.0 +/- 5.4 ml/100g/min, with lesser decreases over the remainder of the ischemic hemisphere. Water content was measured in cortex and white matter, in regions topographically related to those of flow measurements, by densitometric assessment using precalibrated kerosene/bromobenzine columns. The average water content of cortex in regions remote from ischemia was 797.4 +/- 5.8 mg/gm and in white matter 708.5 +/- 8.2 mg/gm. Significant increases in water content (comparing corresponding regions of the two hemispheres) of up to 11.4 +/- 7.5 mg/gm were demonstrated in the most ischemic cortical areas. A gradient of water increase was evident in the ischemic hemisphere, increases water content being greatest in the opercular zone and least in the parasagittal area. Significant differences in white matter water content between the 2 hemispheres were demonstrated only in the most densely ischemic areas in the current experiments where ischemia was limited to 93 +/- 20 mins in the 11 animals without reperfusion. The relationship between ischemic density and water content increase showed that significant increases in water content occurred in regions where terminal flows had been below 20 ml/100g/min, indicating that accumulation of water in ischemic brain begins at flow values comparable to those associated with the failure of synaptic transmission, higher than those associated with failure of the ionic pump of the cell. Possible pathophysiological mechanisms are discussed.
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PMID:Ischemic brain edema following middle cerebral artery occlusion in baboons: relationship between regional cerebral water content and blood flow at 1 to 2 hours. 10 19

The possible advantages of pulsatile over continuous blood flow have intrigued cardiac surgeons for years. This issue may have clinical significance for moderate to long cardiopulmonary bypass procedures. In spite of aggressive investigation, this problem remains controversial. A system permitting perfusion of an isolated canine hind limb with constant flow, Pao2, Paco2, oxygen delivery, temperature, and pHa but variable stroke volume was established. Under stable conditions, oxygen uptake by the limb was constant over a wide range of stroke volumes. Regression equations relating oxygen uptake to stroke volume were calculated and found to have a near zero slope. When the hydrogen ion concentration of the blood perfusing tissue is held constant, the oxygen consumption of that tissue is independent of the pulsatile nature of the perfusing blood.
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PMID:The influence of pulsatile perfusion on oxygen uptake by the isolated canine hind limb. 23 95

It has been hypothesized that acute lesions of the brain enlarge through an autodestructive process. Serotonin (5HT), a potent cerebral vasoconstrictor, is believed by some to mediate the process by reducing cerebral blood flow (CBF) in tissue surrounding the lesion. The hypothesis was tested in cynomologus monkeys anesthetized with ketamine and nitrous oxide. Craniectomies, 7 mm in diameter, were performed in each parietal area. The dura was opened and polarographical electrodes of thin platinum wire were inserted into the parietal lobe cortex of each hemisphere. Mock cerebrospinal fluid (CSF) was irrigated continously onto the brain surrounding the electrodes, from which local CBF was determined repeatedly by the hydrogen-clearance technique. After baseline CBF was established, solutions of 5HT in mock CSF (in concentrations of 5 X 10(-7) M, 5 X 10(-5) M, and 5 X 10(-3) M) were irrigated onto one hemisphere while the opposite hemisphere served as control. 5HT failed to change CBF. Although 5HT is a potent vasoconstrictor, under physiologic conditions it apparently is unable to effect hemodynamically significant constriction of the peripheral cerebral vasculature of the anesthetized monkey brain.
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PMID:Effect of topically applied serotonin on local cerebral blood flow. 41 85

Twenty-seven patients undergoing open-heart surgery were divided into three groups, i.e., control, intermittent aortic crossclamping and coronary perfusion groups. Myocardial oxygen extraction, lactate extraction, arterial-coronary sinus hydrogen ion difference, potassium difference and glucose difference were determined during the operation, as well as, postoperative stroke and cardiac indices and comparisons were made. When the ascending aorta was not crossclamped, myocardial metabolism was well preserved during and after the perfusion at a flow rate of 2.0 L./min/m2. Intermittent aortic crossclamping for 15 minutes alternating with a period of perfusion for five minutes at 30 degrees C was sufficient to protect the myocardium from ischemia. Perfusion of the left coronary artery alone at a flow rate of six per cent of total body perfusion (150 to 200 ml per minute) at 30 degrees C was sufficient to protect the myocardium when the aorta was opened. Since intermittent perfusion of the left coronary artery may produce myocardial derangement, coronary perfusion should be continuous. Otherwise topical cardiac cooling or other means of myocardial protection should be used.
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PMID:Myocardial protection during open-heart surgery: intermittent aortic crossclamping versus coronary perfusion. 60 90

Cerebral cortical blood flow was measured in rabbits with the hydrogen clearance technique. The reactivity to CO2, tested by changing the end tidal CO2 (ETCO2) in steps from 2 to 6 volumes %, was highly dependent on the kind of anesthesia, being greatest under halothane and least under nitrous oxide. Reactivity to CO2 in halothane-anesthetized animals also depended on arterial blood pressure, being greatest when pressure was below 70 mm Hg. Intravenous atropine blocked the increase in reactivity in halothane-anesthetized animals at low blood pressures. Conversely, intravenous eserine (physostigmine) greatly increased the reactivity to CO2 in nitrous oxide-anesthetized animals. Precollicular decerebration considerably decreased CO2 reactivity of halothane-anesthetized rabbits, while partial brain stem lesions that spared midline structures had no effect on CO2 reactivity. It is concluded that a central neurogenic mechanism with a cholinergic link may be responsible, at least in part, for the cerebrovascular effect of CO2. Moreover, the cerebrovascular effects of halothane may result from stimulation of the same system.
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PMID:Cerebrovascular CO2 reactivity: role of a cholinergic mechanism modulated by anesthesia. 64 10

Cerebral hemispheric blood flow (HBF) and metabolism were measured before and after withdrawal of 20 to 30 ml of cerebrospinal fluid (CSF) over a 10-minute interval in eight patients with recent cerebral infarction and in four patients with Alzheimer's disease (AD). Immediately after CSF removal HBF decreased significantly in the AD group (-14%) but showed no significant change in the stroke group (-5%). There was rapid reduction in cerebral venous O2 content and some increase in cerebral venous PCO2 appearing within 60 seconds of CSF withdrawal, interpreted as a rapid reduction of cerebral blood flow (CBF) as judged by cerebral A-VO2 differences. The reduction in CBF was confirmed by the hydrogen clearance method. Reduction of CBF in response to lowering CSF pressure is presumably of neurogenic origin since it was rapid and occurred without changes in PaCO2 or MABP. Furthermore, measurement of HBF demonstrated that cerebral metabolism constant after CSF removal. It is postulated that in AD, reduction of HBF following CSF withdrawal is mediated by a disordered neurogenic veno-arterial vasoconstriction reflex which is stimulated by rapid reduction in CSF pressure (CSFP). In patients with stroke, when cerebral perfusion pressure is increased by lowering CSFP, CBF is maintained constant most likely by a physiological cerebral veno-arterial vasoconstrictive reflex. Apparently, this vasocontrictive reflex becomes excessive in Alzheimer's disease, possibly due to cerebral neurogenic imbalance.
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PMID:Effect of cerebrospinal fluid removal on cerebral blood flow and metabolism in patients with Alzheimer's disease versus recent stroke. 83 58


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