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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to study if rapid elevation of blood pressure is associated with cerebral ischemia, anesthetized (70% N2O) and artificially ventilated rats were subjected to angiotensin-induced hypertension. After a 5 min hypertensive period, cerebral cortex tissue was frozen in situ for subsequent measurements of labile glycolytic metabolites, ammonia, and organic phosphates. The degree of hypertension induced, which gave evidence of blood-brain barrier damage in 7 of 8 rats, did not affect the tissue concentrations of labile metabolites. It is concluded that ischemia does not contribute to the barrier damage, nor is it likely to be the cause of the clinical symptoms that may occur in conscious rats in the same experimental model.
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PMID:Brain energy metabolism in angiotensin-induced acute hypertension in rats. 88 9

A prospective study of 80 patients presenting with amaurosis fugax was performed in an attempt to relate clinical features to angiographic findings in the internal carotid artery. Carotid bruit, transient cerebral ischaemic attacks, hypertension, and claudication were associated with a high prevalence of angiographic abnormality. Every patient who showed all these features had an operable lesion, as did 88% of those who had three features. In patients over 50 years of age carotid stenosis and atheromatous ulceration were occasionally found in the absence of bruit and transient cerebral ischaemia, but only one patient aged under 50 had an operable lesion and no associated features. Clinical features were therefore valuable in predicting the outcome of angiography, but it seems prudent to restrict angiography to patients aged over 50, who are most likely to benefit from surgery on the carotid artery.
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PMID:Amaurosis fugax and carotid artery disease: indications for angiography. 89 Mar 27

Repeatedly bred male rats which develop arteriosclerosis spontaneously were subjected to unilateral nephrectomy, 1% saline drinking water, and 2 mg subcutaneous injections of deoxycorticosterone acetate per animal weekly for 7 weeks to induce severe hypertension (+/- 175 mmHg systolic). Acute cerebral ischemia was induced by ligating one carotid artery. Two days later, experimental animals were subjected to acute myocardial ischemia by injecting them subcutaneously with a single dose of isoproterenol (25 mg/100 g body weight). All of the experimental animals died within 4 hours of the injection of isoproterenol. During this same period, blood pressure, body weight, thymus, kidney, and testicular weights were reduced, whereas heart and adrenal gland weights increased markedly. Serum enzymes (CPK, SGOT, and LDH), lipids (triglycerides and free fatty acids), glucose, BUN, and corticosterone rose progressively. Fatty infiltration of the liver, adrenal hyperplasia, myocardial thrombi, renal degenerative changes, and cerebral edema became progressively more severe. A hypothalamic-pituitary-adrenal axis component may be involved in the reaction to the stress of acute cerebral or myocardial ischemia, which is intensified when the two ischemias are combined, and chronic hypertension may exacerbate both.
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PMID:Acute cerebrovascular and myocardial ischemia superimposed upon chronically hypertensive and arteriosclerotic male Sprague-Dawley rats. 90 14

In five patients with chronic renal failure, rapid correction by dialysis of hypertension and/or high blood urea levels provoked acute neurological disorders, followed by slowly reversible neuropsychiatric disturbances. Focal EEG alterations were noted in three patients with normal carotid angiograms. Our cases differed from those usually described as suffering from the dialysis disequilibrium syndrome because of their duration, the severity of mental disturbances, and the asymmetrical pattern of EEG abnormalities. We propose that the symptoms observed could be due to cerebral ischemia. This possibility emphasizes the importance of limiting the duration and efficiency of the first dialyses in patients with severe hypertension and high nitrogen retention, especially if high performance dialyzers are used.
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PMID:Unusual aspects of the dialysis disequilibrium syndrome. 95 37

Deliberate hypotension can reduce major blood loss and indelicate operations can produce a drier field increasing the ease of surgery and the likelihood of a good result. The techniques used to induce hypotension can also be used to avoid dangerous hypertension during and after surgery. These benefits must be weighed against the risks of inadequate perfusion: especially cerebral, myocardial, or renal. In previously normotensive patients these risks are minimal when the arterial pressure is held above 80 torr systolic, and may be acceptably small even at mean pressure of 50 to 60 torr. Previously hypertensive patients show signs of cerebral ischemia at higher pressures; they should probably not be subjected to deliberate hypotension, but they also can be harmed by severe hypertension which can be avioded by the proper use of hypotensive agents. For most situations a balanced technique is suitable: after a stable anesthetic level has been achieved using halothane or enflurane, hypotension can be induced with sodium nitroprusside or trimethaphan camsylate. Longer-acting agents such as pentolinium are sometimes desirable, but the shorter-acting agents are easier to control. Careful monitoring with observation of intra-arterial pressure, electroencephalogram, electrocardiogram, and determination arterial blood gas tensions is likely to make for safer conduct. Close postoperative observation is essential. With careful preparation and monitoring deliberate hypotension can be a safe technique for reducing blood loss or facilitating delicate procedures.
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PMID:Deliberate hypotension. 110 15

The routine investigations in patients with cerebral ischaemia are considered. Surgical treatment of the extracranial carotid and subclavian arteries is still advocated in the management of selected patients with transient cerebral ischaemia. Little fundamental advance has been made in the treatment of acute cerebral infarction. The role of hypertension in cerebrovascular disease is considered and the value of treating associated hypertension is stressed.
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PMID:The treatment of cerebral vascular disease. 110 39

Cerebral blood flow, electrical activity, and neurological function were studied in rabbits subjected to either 15 minutes of oligemia (20 torr cerebral perfusion pressure) or complete cerebral ischemia produced by cisterna magna infusion. During oligemia, flow was reduced from 68.4 +/- 4.2 ml/100 gm/min to 26.3 +/- 4.4 (p less than .01), and during ischemia animals had no proven flow. By 5 minutes after oligemia or ischemia significant symmetrical hyperemia occurred and there was no evidence of the no-reflow phenomenon. The electroencephalogram became isoelectric significantly later and returned significantly sooner in oligemia than in ischemia. Oligemic animals had earlier and better return of neurological function than their ischemic counterparts, although postinsult hypocapnia improved functional recovery in both groups. These experiments do not support the concept that oligemia is a more severe insult than complete ischemia. In intracranial hypertension produced by this model, the no-reflow phenomenon does not occur.
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PMID:Experimental cerebral oligemia and ischemia produced by intracranial hypertension. Part 1: Pathophysiology, electroencephalography, cerebral blood flow, blood-brain barrier, and neurological function. 115 66

Regional cerebral blood flow (rCBF) was measured in three patients after relief of elevated intracranial pressure and restoration of normal cerebral perfusion pressure. Two patients, studied within 4 hours after closed head injury were found to have marked impairment of cortical blood flow and elevation of cerebrovascular resistance. We suggest that this picture is indicative of impending brain death, and may be the result of a long period of severe cerebral ischemia. The third patient, who had a shorter period of intracranial hypertension occurring during anaesthetic induction, responded to reduction of ICP quite differently with a transient relative hyperaemia. The physiopathological explanations for these two different types of flow response and their possible clinical significance are discussed.
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PMID:rCBF in impending brain death. 118 10

Seventy-seven carotid endarterectomies performed on fifty-nine patients, using induced systemic hypertension during carotid artery clamping, were reviewed. The risk of cerebral ischemia is reduced to a minimum by this technic. The measurement of the internal carotid artery stump pressure is an excellent guideline for the need of additional brain protection. An internal shunt is rarely necessary. Thromboembolic phenomena contributed to the major neurologic complications encountered (two deaths and one stroke). Extreme gentleness and careful surgical technic cannot be overemphasized.
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PMID:Carotid endarterectomy: Is a shunt necessary? 120 Feb 96

Between 1968 and 1970, 226 patients with acute cerebral ischaemia were treated with vasodilator drugs. In the subsequent three years (1971 to 1973) 202 patients were instead treated with dextran (Rheomacrodex) infusions. tin the latter period the death-rate was 35%, 19% less than during the preceding period of vasodilator treatment. In the dextran group among patients over 65 years the death-rate was 42%, 21% less than in the vasodilator group of the same age. Dextran treatment caused complete disappearance of neurological signs in 25%, compared with 7.5% in the vasodilator group. Dividing patients into those with normal blood pressure, hypertension and diabetes gave corresponding differences among the two groups. The death-rate during the period of dextran treatment was significantly less in all the sub-groups than in the vasodilator years. The results of this retrospective study provide important pointers to the effectiveness of dextran infusion in the treatment of acute cerebral ischaemia.
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PMID:[Treatment of acute cerebral ischaemia with low-molecular dextran: results of a retrospective study (author's transl)]. 124 5


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