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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The handling of patients with cerebral ischemia is reviewed, taking into consideration recent concepts regarding etiopathogenesis along with new diagnostic and therapeutic methods. A particularly important new diagnostic method is computerized axial tomography. The subject is divided into four sections in order to present a practical outline. The first section deals with the arterial circulatory system. Evaluation of patients with arteriosclerosis of the vessels in the neck and/or intracranial are reviewed in some detail, according to whether the clinical manifestation was transitory ischemia, progressive cerebral infarction, or complete cerebral infarction. Emphasis is placed on the proper selection of diagnostic tests and application of therapy in each case. The second part is a discussion of the changes in arterial blood pressure in the etipathogenesis of stroke. Arterial hypertension is an important factor in production of small infarctions. In the third section a review is made of the role of the heart in transitory ischemia and as a cause of cerebral infarctions. Lastly, the hematologic factors which might contribute to the development of cerebral ischemia, along with the other causes, are mentioned.
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PMID:[Practical considerations in dealing with cerebral ischemia (author's transl)]. 47 Apr 90

PGBx, a new polymeric derivative of PGB1, previously was shown to (a) restore oxidative phosphorylation to degraded isolated rat liver mitochondria in vitro and (b) to reverse the effects of cardiogenic ischemia in monkeys and cerebral ischemia in rabbits. This report describes in detail the synthesis and purification of PGBx via PGB1, starting with azelaic acid. Details of the in vitro mitochondrial assay are also reported. Purified PGBx exhibiting maximal reactivation of mitochondrial phosphorylation has a mean molecular weight of 2350. Yield of PGBx based on azelaic acid is 4% and based on PGB1 is 25%.
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PMID:Studies on PGBx, a polymeric derivative of prostaglandin B1: I. Synthesis and purification of PGBx. 48 83

Earlier results are reviewed suggesting that transient pronounced, incomplete cerebral ischemia could be more deleterious for the recovery of brain tissue energy state than a complete interruption of the blood flow. Measurements of respiratory function of brain mitochondria, isolated after 30 min of either complete or incomplete ischemia, demonstrated a similar inhibition of respiratory activity and maximal phosphorylation rates in both situations. This inhibition was totally normalized during recirculation after complete ischemia while a further deterioration was found after incomplete ischemia. The in vivo alterations of the cortical tissue distribution of redox states during transient, incomplete ischemia (15--60 min) were measured using a flying spot fluorometer, which gives a real-time and on-line display of the tissue distribution of NADH and oxidized flavoprotein. A reoxidation in both systems was demonstrated during the recirculation period and the distribution of redox states showed no further heterogeneity in the postischemic period as compared to the preischemic distribution. It is concluded that reoxygenation of the brain tissue is possible even after long periods of incomplete ischemia. The normal distribution of redox states during recirculation suggests that mechanisms other than an impaired or inhomogeneous oxygen delivery during the postischemic period are responsible for the failure in recovery of mitochondrial function and tissue energy state.
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PMID:Cerebral energy state, mitochondrial function, and redox state measurements in transient ischemia. 48 72

Progressive cerebral ischemia was induced by blood pressure (BP) reduction in rats during status epilepticus, and the sequence of cerebral functional (EEG, extracellular K+ activity) and metabolic (levels of high energy phosphates, glucose, glucose-6-phosphate, lactate, pyruvate, alpha-ketoglutarate) changes were determined. Very moderate reductions of BP were accompanied by tissue lactate accumulation and a decrease of the rate of re-uptake of K+ extruded during discharges. These changes were pronounced at BP about 50 mm Hg, when also the energy state showed some deterioration, and the EEG activity changed from one of bursts and suppressions into single spikes. At BP about 30 mm Hg EEG activity was abolished, but not until a slightly lower BP level was there a severe energy depletion and a massive K+ release, indicating generalized membrane depolarization. The results show an increased susceptibility to ischemia during seizures with changes of membrane pump function, and energy metabolism appearing at moderate reductions of BP. Concomitant decrease of seizure activity delayed to some extent the development of massive energy failure and membrane depolarization.
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PMID:Effects of reduced cerebral blood flow upon EEG pattern, cerebral extracellular potassium, and energy metabolism in the rat cortex during bicuculline-induced seizures. 49 17

Twenty-three instances of internal carotid artery occlusion occurring with minimal neurological deficit in 22 patients are described. Although each of these patients was referred to the neurosurgical service for evaluation for an extracranial-intracranial microvascular bypass procedure, complete arteriographic evaluations of their cerebrovasculature suggested that alternative methods should be the treatment of choice. For each patient reported the ipsilateral external carotid artery was demonstrated by angiography to be an important source of collateral blood supply to the cerebral hemispheres or retinae distal to the occluded internal carotid arteries. Ten patients with no significant atherosclerotic narrowing or ulceration of the external carotid artery have remained free of symptoms of cerebral ischemia for 6 to 40 months. In twelve patients who developed delayed recurrent cerebral or retinal ischemia ipsilateral to their internal carotid artery occlusion, there were found obstructive and/or ulcerative plaques involving the common and/or external carotid arteries. Thromboendarterectomy in 11 of these patients gave complete relief of ischemic symptoms during the 4 to 36 months of postoperative follow up. One of these 12 patients refused operation and went on to develop a major cerebral infarction. Angiographic identification of a functionally important external carotid artery ipsilateral to an internal carotid artery occlusion carries considerable prognostic and therapeutic significance.
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PMID:External carotid artery in internal carotid artery occlusion. Angiographic, therapeutic, and prognostic considerations. 50 84

The left cerebral hemisphere of Mongolian gerbils was used to elucidate the mechanisms of brain edema which develop during cerebral ischemia and after restoration of cerebral blood flow following temporary ischemia. Water content was measured by the tissue-drying method. Sodium and potssium ion concentration was measured by flame photometry. Passage of 131I-albumin (RISA) from blood to the cerebral parenchyma was measured on a gamma scintillation counter. Our findings indicate that pure cytotoxic edema develops during ischemia and during a short period after restoration of cerebral blood flow. Vasogenic edema, which is accelerated by the leakage of plasma constitutents from blood due to blood-brain barrier damage, developed after restoration of the cerebral blood flow. After less than 1 hr of ischemia, restoration of the cerebral blood flow drastically reduced the degree of brain edema. However, restoration of the cerebral blood flow greatly worsened the brain edema following more than 3 hr of ischemia.
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PMID:Brain edema during ischemia and after restoration of blood flow. Measurement of water, sodium, potassium content and plasma protein permeability. 50 96

It has been reported that incomplete cerebral ischemia with cerebral blood flow less than 10% of control may be more damaging than an equal period of complete ischemia. In this study, the effects of severe, incomplete cerebral ischemia on neurological outcome and cerebral metabolism were studied in dogs anesthetized with nitrous oxide. The results were compared with those of a previous study concerned with the effects of complete ischemia. Dogs could sustain only 8 to 9 minutes of complete ischemia with return of normal neurological function, whereas maintenance of a cerebral blood flow rate less than 10% of control extended this limit to 10 6o 12 minutes. Following a 10-minute exposure, only dogs undergoing incomplete ischemia regained a normal cerebral oxygen consumption within 90 minutes; similarly, animals subjected to incomplete ischemia enjoyed a faster return of EEG activity than dogs exposed to complete ischemia of the same duration. Cerebral metabolite levels did not prove to be a good index of return of neurological function. Within periods of cerebral ischemia in which meaningful neurological recovery might be expected, we conclude that some blood flow is better than no flow.
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PMID:Incomplete versus complete cerebral ischemia: improved outcome with a minimal blood flow. 51 35

A total of 289 carotid endarterectomies were performed in 204 patients. A decision to place a temporary shunt during carotid endarterectomy in this series was made entirely on the basis of intraoperative EEG monitoring. Retrospectively, the correlation between stump pressures and the results of intraoperative EEG monitoring in each case was determined. Evidence of ischemia developed in 6% of the total series on intraoperative EEG monitoring despite a stump pressure of greater than 50 mm Hg. The degree of disagreement between stump pressure and EEG varied according to clinical category in this series. In those endarterectomies performed for completed stroke, all cases requiring shunting had stump pressures less than 50 mm Hg. In those cases performed for symptoms of vertebral basilar insufficiency, however, 77% of the cases requiring an intraoperative shunt had stump pressures greater than 50 mm Hg. A review of the complication rate in the various study groups indicates that the use of intraoperative EEG is a safe indicator of cerebral ischemia during carotid endarterectomy regardless of stump pressure.
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PMID:Failure of carotid stump pressures. Its incidence as a predictor for a temporary shunt during carotid endarterectomy. 53 56

The results of a retrospective study of patients undergoing carotid endarterectomy for hemispheric and/or nonhemispheric symptoms of transient ischemic attacks are presented. During an approximately 3-year period of follow-up observation, recurrent cerebral ischemia following carotid endarterectomy was two to three times more frequent among patients with nonhemispheric transient ischemia than among those with hemispheric transient ischemia. Patients with symptoms of both hemispheric and nonhemispheric transient ischemia had the highest frequency of transient ischemic attacks and stroke during the follow-up period and also had the greatest surgical morbidity and mortality. The results of this study suggest that carotid endarterectomy has little or no therapeutic value in treating patients with vertebral-basilar ischemia.
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PMID:The value of carotid endarterectomy in treating transient cerebral ischemia of the posterior circulation. 55 76

Human studies indicate that transient platelet abnormalities accompany acute cerebral ischemia. Although these abnormalities may precipitate the ischemi process, ischemia could also alter platelet function. Platelets were therefore studied in gerbils subjected to 1 hour of unilateral carotid artery occlusion. Venous blood from five clinically affected gerbils contained more aggregated platelets (37.8% +/- 6.4) than did blood from eight unaffected animals (11.1% +/- 3.0; p less than 0.01). Platelets labeled with 3H-serotonin were increased in ischemic brain; the ratio of radioactivity in the ipsilateral versus contralateral hemisphere was greater in eight affected (1.09 +/- 0.03) than in 19 unaffected (1.00 +/- 0.01; p less than 0.02) animals. The radioactive serotonin was located predominantly within blood vessels. Cerebral ischemia thus stimulated the formation of platelet aggregates, a response which could contribute to the ischemic process.
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PMID:Experimental cerebral ischemia produces platelet aggregates. 57 98


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