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

The authors report the values of mean hemispheric blood-flow and cerebral arterial consumption they found in 34 neurosurgical comatous cases in acute state. In basal conditions, mean values of mean hemispheric bloodflow and oxygen consumption are lowered. There seems to be a relation between the values found and the comatous stage on one hand, the prognosis on the other hand. The cerebral response to hypercapnia (16 assays) allows to separate 2 groups, one with a noticeable improvement of cerebral bloodflow, the other with only a minimal response. There was no significant variation of cerebral oxygen consumption in both group. Cerebral response to CO2 seems to be clearly related to the stage of coma (low in the most severe cases) but pronostic incidence remained uncertain. A hypertensive test by means of Aramine (18 assays) allows to separate 3 groups : 1 group (8 cases) where the mean hemispheric bloodflow remained stable during hypertension as did the cerebral oxygen consumption -(autoregulation remained unchanged), 1 group (4 cases) where mean hemispheric bloodflow and cerebral oxygen consumption were lowered (excessive autoregulation), 1 group (6 cases) where mean hemispheric bloodflow increases clearly while under Aramine perfusion (loss of autoregulation). Those dynamic tests, either hypercapnic or hypertensive, allow, in comparing oxygen consumption variations with cerebral bloodflow variations, the distinction between : patients where metabolic autoregulation seems maintained (good prognosis) - (10 cases), patients where metabolic regulation is lost with either "luxury perfusion" (14 cases) - poor prognosis, or "insufficient perfusion" (10 cases). The authors are discussing the treatment concerning those last mentioned patients.
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PMID:[Value of cerebral metabolic exploration in post-traumatic coma states in the acute phase]. 1 86

Inhalation of a gas mixture : CO2, 25% -- O2, 37.5% -- N2, 37.5%, provokes regularly in the light anaesthetized rat, an increase of catecholaminemia of central origin, associated with systemic arterial hypertension.
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PMID:[Orthosympathetic stimulation after hypercapnia in the rat]. 9 25

Decompensation of brain injured patients during the night is common and has been attributed to the retention of CO2 during sleep. When CO2 is controlled, such nocturnal decompensation needs another explanation; consequently, the records of 21 consecutive patients with acute closed head injuries and increased intracranial pressure were reviewed. There were 185 separate episodes of intracranial hypertension (30 mm Hg or more for 10 minutes or more) in the 21 patients, 124 of which (67%) occurred between 4:00 a.m. and 9:00 a.m. (p less than 0.01). Intravenous pentobarbital (3 to 5 mg/kg) was effective in reducing the intracranial pressure (ICP) to normal levels during 104 of the 124 early morning episodes (84%), whereas mannitol was less effective (7 of 17; 41%). This suggests that an increase in brain blood volume directly related to diurnal rhythm is responsible for the increase in ICP. Severe bradycardia and systemic arterial hypertension were unreliable predictors of elevation in ICP. They preceded or accompanied less than one-fourth of the episodes.
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PMID:The influence of diurnal rhythms in patients with intracranial hypertension: implications for management. 21 32

Using previously inserted catheters, 11 dogs native to high altitude (7.5-23 kg bwt) were studied standing and unsedated in Cerro de Pasco, Peru at 4350 meters. Hemoglobin (Hb), hematocrit (Hct), O2 and CO2 contents, PO2, PCO2 and pH were measured in simultaneously obtained arterial and mixed venous blood samples. Blood pressures were measured in the pulmonary artery and the left ventricle and cardiac output (Q) was determined by dye dilution. Moderately higher values for Hb and Hct were found in these dogs. Hb-O2 affinity was no different than that found in sea level dogs: the P50 in the Andean dogs was 31.6 mm Hg at 38 degrees C and pH of 7.4. Because of the low barometric pressure at 4350 m (458 mmHg) the partial pressures of oxygen in inspired and in alveolar air were lower than at sea level: 84.3 and 56.4 mm Hg, respectively. PAO2 and PVO2, were 55.5 and 32.9 mm Hg while the SAO2 and SVO2 were 79.5 and 50.7%, respectively. Marked hyperventilation was observed (PACO2, 25.6 mm Hg) however, pH was normal. Cardiac output was normal (average 162 plus or minus 39 ml/min/kg). Moderate pulmonary arterial hypertension was observed in the presence of normal left ventricular end diastolic pressure suggesting increased pulmonary vascular resistance.
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PMID:Mechanisms of O2 transport in Andean dogs. 23 72

Venous distensibility in essential hypertension has been reported to be unchanged or decreased; its pathophysiologic role is uncertain. In 27 male hypertensive patients and 21 normotensive control subjects, forearm venous distensibility and capillary filtration rate at 30 cm of H2O distending pressure were measured by strain gauge plethysmography. Plasma renin activity (PRA), plasma volume (PV) by the Evans blue dye dilution technique, mean arterial pressure (MAP) by cuff, and cardiac output (CO) by the CO2 rebreathing method were also measured. Compared to values in normotensive control subjects, forearm venous distensibility in hypertensive subjects was decreased (P less than 0.05); the forearm venous pressure-volume curves (deflation phase) were shifted in the direction of the pressure axis (P less than 0.02); and the capillary filtration rate was increased (P less than 0.05). Venous distensibility changes in hypertensive subjects were unrelated to PRA, MAP, PV, CO, stroke volume, and total peripheral resistance. These findings confirm previous reports of decreased venous distensibility in hypertension and provide direct evidence for increased capillary filtration rate. In view of the lack of significant correlation between venous distensibility and the measured hemodynamic parameters, a patho-physiologic role for venous distensibility in hypertension could not be established.
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PMID:Decreased venous distensibility in essential hypertension: lack of systemic hemodynamic correlates. 37 15

Sequential changes of regional cerebral circulation and effects of spontaneous recanalization of occluded artery on cerebral circulation were observed in 50 patients with cerebral infarction. 1) Luxury perfusion was predominantly recognized in the recanalized patients within 16 days after onset. 2) Impairment of vasomotor responses was almost the same in the recanalized patients and the occluded patients. 3) CO2 response tended to recover about 3-4 weeks after onset, but disautoregulation to induced hypertension persisted up to 2 months after onset. Some clinical problems are discussed.
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PMID:Sequential changes of regional circulation in cerebral infarction. 74 Jan 78

Twelve patients with gross vascular occlusions and with infarcts demonstrated in CT were examined with regard to their hemodynamic situation. Angiography and rCBF with intra-arterial and inhalation techniques were performed. Response to increased arterial hypertension and to CO2 inhalation was tested. It is concluded that one technique alone does not provide enough information for the selection of patients suitable for EIAB operation.
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PMID:Neurocirculatory analysis of potential EIAB patients. 74 Jan 82

The CO2 rebreathing method, a noninvasive indirect Fick procedure, has been previously validated in normal subjects at supine rest and during exercise. In the present study 29 nearly simultaneous measurements of cardiac output were made by CO2 rebreathing and dye dilution in 17 patients with cardiovascular disease, 11 with hypertension, and six with congestive heart failure. Cardiac output at supine rest averaged 5.52 +/- 0.31 L. per minute by CO2 and 5.62 +/- 0.32 L. per minute by dye dilution (r = 0.93). Successive cardiac output measurements by rebreathing varied 6.0 +/- 1.1 per cent (r = 0.96) and by dye dilution, 6.5 +/- 0.9 per cent. Changes in cardiac output during exercise or after beta-adrenergic blockade were reflected by the CO2 method. It is concluded that the CO2 method provides reliable measurements of cardiac output both at rest and during exercise in patients with hypertension or congestive heart failure. Further validation of the method is needed in various disease states before it can be widely applied.
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PMID:Validation of the CO2 rebreathing method for measuring cardiac output in patients with hypertension or heart failure. 78 59

In industrial countries the symptoms "headache" has an incidence of about 10%, and hypertension between 20 and 25%. Both terms are summary and may be pointers to and warning signals of the most varied disease processes. While, in malignant hypertensions, and pheochromocytoma, headache is a cardinal symptom, its causal connection with permanently raised blood pressure in the "benign" forms is viewed with scepticism. The observation that hypertensives frequently complain of headaches with a maximum intensity in the early hours of the morning is connected with the fall in blood pressure with accumulation of CO2 in shallow breathing. Headache as a symptom characteristic of hypertension is frequently only facultative in nature and must be classified among the series of symptoms of sequelae. But it offers a sufficient reason to institute a selective examination programme, especially as hypertension is still the most common cause of death even today.
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PMID:[Headache associated with hypertension from the internist's and neurologist's point of view (author's transl)]. 81 25

Using specific anesthetic agents, permanent segmental occlusion of the proximal middle cerebral artery (MCA) causes ischemic infarction limited to the putamen and other deep hemispheral structures in primates. Using this model, 25 rhesus monkeys were subjected to acute arterial hypertension before, during and up to 5 days after onset of MCA occlusion in order to reevaluate the possible role of the ischemic process in pathogenesis of cerebral hemorrhage. Norepinephrine infusion induced prompt rapid rise in mean arterial pressure (MAP) and intracranial pressure (ICP) limited to the duration of infusion. This procedure produced acute ischemic lesions which were totally bland but topographically more extensive than untreated controls; in chronic lesions, however, deep nuclear masses showed hemorrhagic infarction. Animals given 5% CO2 air had slowly progressive elevation in ICP and MAP. Acute specimens showed intact, widely-dilan hypercarbia was induced 5 days after MCA occlusion, animals developed intracerebral hematoma involving putamen, external capsule and claustrum, occasionally dissecting through to ipsilateral ventricle. In acute cerebral ischemia, elevated MAP produced only quantiative changes in lesion size. In the vasoproliferative stages of mature infarction, MAP elevation induced by a cerebral vasoconstrictor caused hemorrhagic infarctions while cerebral vasodilation caused intracerebral hematomas.
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PMID:Primate model of cerebral hematoma. 82 36


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