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

The influence of an instantaneous increase in afterload on the hemodynamics and regional myocardial function was studied in five anesthetized dogs before and after occlusion of the left anterior descending coronary artery. By inflation of an intaaortic balloon during single ejections, an instantaneous increase in afterload was obtained. From biplane cineventriculograms, the following parameters were calculated: left ventricular volumes (EDV, ESV), stroke volume (SV), ejection fraction (EF). Mean circumferential fiber shortening (V CF) was calculated in three ventricular diameters in the RAO projection. Simultaneously PLV, PLVED, PAo, and LV dp/dt were obtained. In the control ventriculograms, an increased afterload (delta PLV 16.4 +/- 8 mm Hg) caused only a minor decrease of SV (2.6 +/- 2.5 ml), EF (4.2 +/- 2.4%), and V CF (0.20 circ . s -1). After coronary occlusion (delta PLV 14.5 +/- 6.7 mm Hg),the reduction of SV (5.9 +/- 2.7 ml) and EF (8.2 +/- 2.6%) was more pronounced. This was caused mainly by a significant reduction of V CF in the center of ischemia (delta V CF -93%). For the evaluation of regional myocardial function by ventriculography, the marked influence of afterload in ischemic areas must be taken into consideration. This is of special interest in comparative ventriculograms, such as those before and after coronary bypass surgery.
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PMID:[The influence of afterload on the normal and ischemic myocardium in the dog]. 71 34

Computed tomography has proved to be the most effective mode of evaluating cerebral infarction in 143 documented cases. This was especially true when multiple focal infarcts were present. The incidence of contrast enhancement in acute infarcts was 88%. Concomitant acute and old infarcts were observed in 20% of cases. In the acute stage of stroke, radionuclide studies are preferable to contrast angiography since the latter may aggravate the pre-existing focal ischemia. Follow-up CT and radionuclide scans were extremely useful in confirming the diagnosis and demonstrating various postinfarction sequelae.
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PMID:Evaluation of cerebral infarction by computed tomography with special emphasis on microinfarction. 74 Jan 60

We measured cerebral oxygen extraction, cerebral blood flow(CBF), and cerebral metabolic rate (CMRO2) in comatose patients during the first 60 hours after resuscitation from cardiac arrest. Each patient was studied 2 or 3 times. CBF was determined by a modification of the Kety-Schmidt method using inhaled Xenon133. Over the study period jugular venous oxygen tension and saturation rose, while the oxygen content difference between arterial and jugular venous blood fell, indicating a progressive increase in the ratio of CBF to metabolism CBF and CMRO2 measurements confirmed this. Between 2 and 6 hours after resuscitation both measurements were severely but proportionately depressed to less than 50% of normal. After 6 hours CBF was increased disproportionately to CMRO2 so that a relative hyperemia developed and persisted for the duration of the study. Although regional inhomogeneity of flow and regional ischemia cannot be ruled out, we have found no evidence for global cerebral ischemia between 2 and 60 hours post-resuscitation as an explanation for failure of recovery. In man following cardiac arrest restoration of levels of global cerebral blood flow, which can be considered adequate relative to the depressed metabolic state of the tissue, is achieved within 2 hours of resuscitation.
Stroke
PMID:Cerebral blood flow and metabolism in man following cardiac arrest. 74 88

Compression ischemia of the central nervous system (CNS) in heparinized dogs caused areas of diminished cerebral blood flow measured by 14C-antipyrine autoradiography. Intravenous infusion of indomethacin (1.5 or 4.0 mg/kg) approximately 1 hour before ischemia eliminated the circulatory defects. Prophylactic inhibition of prostaglandin synthetase may promote postischemic perfusion of the CNS by preventing vasoconstriction and by anti-hemostatic effects on blood.
Stroke
PMID:Indomethacin prevents impaired perfusion of the dogs's brain after global ischemia. 74 93

With corticosteroids and diuretics, glycerol treatment may be an effective therapy of early edema accompanying focal brain ischemia. The suggested regimen for intravenous infusion is 500 ml of 10% glycerol solution during at least 2 h, twice a day, starting as soon as possible after stroke onset and continuing thereafter for 5--7 days.
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PMID:Therapy of ischemic brain edema. 75 28

In the majority of apoplexy patients the absence of a primary haemorrhage points to acute vascular occclusion with regional ischemia as the initiating event. Yet, in many such cases in particular with transient symptoms, no occlusions can be found angiographically. This along with other evidences suggest that early lysis of the occlusion is frequent. The critical levels of 20 and 10 ml/100 g/min of ischemia are discussed along with the therapeutic inferences. It is concluded that only by emission tomography--the radioisotopic counterpart to CT scanning--will a quantitation of ischemia and of metabolic integrity of tissue areas be possible as a prerequisite for rational therapy.
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PMID:Cerebral blood flow in cerebral ischemia. A review (with 1 color plate). 75 36

In the presence of regional myocardial ischemia, a 20% decrease in systemic arterial pressure following nitroprusside caused a 25% decrease in coronary perfusion pressure in animals with normal left ventricular end-diastolic pressures. This pressure decrement resulted in a significant decrease in the shortening of the regionally ischemic segment during the ejection phase of systole. A comparable arterial pressure drop of 21% with nitroprusside infusion during ischemia in the animals with elevated diastolic pressures caused a similar 28% decrease in coronary perfusion pressure, but resulted in a simultaneous increase in regional shortening. For the entire group there was no significant change in stroke volume. Even in the 11 animals where stroke volume increased, systolic regional shortening increased in only 4. An increase in stroke volume cannot be used to infer a parallel increase in the performance of a regionally ischemic segment. Nitroprusside appears to improve regional performance only in the presence of severe failure.
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PMID:Effects of sodium nitroprusside on function of regional ischemic myocardium. 75 85

A survey of the currently available methods for the measurement of cerebral blood flow in man is given. Many of the clinically important brain diseases such as tumors, stroke, brain trauma or epilepsy entail focal or regional flow alterations. Therefore a special emphasis is placed on methods allowing measurements of regional cerebral flow, rCBF. The intra-arterial 133Xenon injection method is now widely used as a standard method for rCBF measurement. It affords a good two-dimensional resolution when using a suitable dynamic gamma camera which allows a high counting rate to be recorded. But, due to the superposition of tissues the three-dimensional resolution is limited. This, in particular, means that smaller areas of ischemia (low flow) tend to be overlooked whereas local hyperemia is readily discerned. The 133Xenon inhalation method is less accurate, contaminated by extra-cerebral uptake, and insensitive both for detecting regional ischemia and regional hyperemia. The spatial resolution is also much more limited. For these reasons great caution must be exercised in interpreting the results. Methods yielding three-dimensional rCBF data will be needed in order to gain more precise information both on spatial localization and, especially, on ischemic areas. The most promising is computer-assisted axial tomography with freely diffusible radioactive isotopes or with x-rays using an intra-arterial injection of contrast. But, the available techniques are still too slow: in order to measure blood flow one "exposure" must be taken every second. Only a few methods give quantitative information of the blood flow in the human brain. This is mainly due to the inaccessibility of the brain within the skull and to the complexity of the cerebral arterial and venous systems. Before reviewing the various methods used in man, it should be mentioned, that much of the fundamental knowledge has been gained by methods only applicable to animals. Measurements of the diameter of the small arteries on the surface of the brain antedates even the classical studies of Roy and Sherrington (1890). This technique continues to be useful, modern technical improvements consisting of the use of micropipettes and a stereo microscope in combination with an image splitter and a television camera which allows the accurate assessment of diameter variations of a few percent [22]. Autoradiography of brain slices using diffusible indicators is the best quantitative method for measuring local blood flow in a great many parts of the brain [7, 45]. Microspheres are also being used, but it is still not quite clear that this technique gives reliable quantitative data in small masses of tissue [34, 41, 50].
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PMID:Methods for measurement of cerebral blood flow in man. 77 75

Regional cerebral blood flow (CBF) was measured (intra-arterial injections of 133Xe) and electroencephalograms (EEG) were recorded periodically before, for two hours during, and for one and one-fourth hours after middle cerebral artery (MCA) occlusion in 20 squirrel monkeys (Saimiri sciureus). A CBF-Paco2 response curve for these animals under barbiturate anesthesia was created from CBF values prior to MCA occlusion and during the time a steady state was being achieved. The animals were subdivided into four groups (five monkeys in each) on the basis of Paco 2 values: 20, 36, 40, and 60 mm Hg. CBF values from this study were compared to previous results obtained with 85Kr. The phenomenon of "look through" and the importance of recognizing this artifact and its significance in analyzing CBF results in areas of focal ischemia are discussed. The present results were correlated with cerebral ATP and lactate concentrations in ischemic regions determined in previous studies using this preparation at these Paco2 values and at comparable time intervals before, during, and after MCA occlusion. The EEG appears to reflect the state of ischemic brain accurately. However, CBF measured by the 133Xe method can be misleading in regard to the true degree of ischemia resulting from occlusion of an intracranial vessel and cannot be relied on to demonstrate accurately "steal" or "reverse steal" due to changes in Paco2.
Stroke
PMID:Blood flow measurements and the "look through" artifact in focal cerebral ischemia. 80 30

Postictal transient focal neurological deficits, i.e., Todd's paralysis, at times are correlated with early veins and/or vascular stain angiographically. Radionuclide gamma camera images show that they also may be accompanied by a relative flow hyperperfusion and a cortical rim static image uptake. Using these observations some portion of Todd's paralysis may be explained as the result of focal epileptic discharges that lead to local vasomotor and/or metabolic changes. The functional arterial venous shunting that results could contribute to cortical ischemia and the subsequent clinical deficits.
Stroke
PMID:Todd's paralysis: A cerebrovascular phenomenon? 80 98


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