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

The effect of diazepam (0.15 and 0.5 mg/kg) and chlordiazepoxide (1.0 and 2.0 mg/kg) on the blood supply and cardiac action were investigated in experiments on cats anesthetized with urethan and chlorasol. Both these compounds were found to lower the vascular resistance to the blood flow, to bring down the coronary circulation rate and the oxygen intake of the heart. The preparations exert a marked influence on the work of the heart and the state of hemodynamics. Diazepam causes the development of an appreciable hypertension, bradycardia and reduces the cardiac ejection. Chlordiazepoxide produces a less pronounced fall of the arterial pressure, bradycardia and reduced the cardiac ejection. Unlike chlordiazepoxide diapezam reduces the contractibility of the myocardium, this being manifested in lessening the maximum acceleration of the blood flow in the aorta and in an increase of the systolic contraction time. Inhibition of the myocardium contractility occurring under the influence of diazepam may, to a certain degree, explain more pronounced hypotension observable on administration of this preparation.
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PMID:[Effect of tranquilizers (diazepam and chlordiazepoxide) on the blood supply and activity of the heart]. 122 3

A polystyrene-covered platinum electrode (100-150 mum diameter) has been used to measure cortical tissue oxygen tension in baboon brains. The method of preparation, calibration, and the importance of small residual current (less than 40 nA) as an attribute of a reliable electrode, are described. With electrodes of this size, there was a large (16 +/- 12nA/torr) and linear current output with pO2 changes. The effect of avrious gases in addition to oxygen is described; halothane inhalation increases the apparent pO2 and hydrogen, used for blood flow estimations, reduces the recorded pO2. In 48 separate electrode placements in 13 baboons, the mean cortical qo2 was 23.8 +/- 12 mm Hg, with a range from 1-79 mm Hg; following occlusion of one middle cerebral artery, 37 electrodes recorded a pO2 of less then 5 mm Hg pO2 Oscillations were invariably noted in control conditions, independent of blood pressure; these waves disappeared during MCA occlusion and appeared to be augmented following release of the clip. Blood pressure "spikes" produce immediate and synchronous changes in all electrodes entirely different from the spontaneous waves. Such blood pressure changes may mask the true effect of hypercapnia on tissue pO2 and, if ignored, may lead to erroneous assumptions regarding local neural control of the circulation, the increased pO2 secondary to hypertension being regarded as evidence of regional vasodilation. A SUdden change in inspired pO2-the "air test"-was performed in control conditions and following the ischaemic insult, and the rate of change of cortical pO2 compared. The gradient was significantly greater (P less than 0.05) following ischaemia, suggesting a changed ratio in the tissue's flow to oxygen requirements and/or a persisting vasodilatation.
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PMID:Measurements of oxygen tension in the cerebral cortex of baboons. 124 79

The pressure-rate product during anginal pain produced by right atrial pacing was studied in 12 patients before, during, and after an angiotensin infusion sufficient to produce a significant rise in blood pressure. During the infusion the pain occurred at a significantly lower heart rate (P less than 0.001). However, the pressure-rate product was similar during anginal pain before and during the angiotensin-induced hypertension and after it wore off. Our studies support the concept that in each individual there is a constant level of myocardial oxygen consumption, as expressed by the pressure-rate product, at which anginal pain occurs.
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PMID:Constancy of pressure-rate product in pacing-induced angina pectoris. 125 94

It is recognized that postoperative mortality, infarction and the need for inotropic support are increased following myocardial revascularization in highrisk patients. Operations were carried out in 57 such patients in whom one or more of the following factors were present: ventricular dysfunction-ejection fraction less than 0.4 (17), unstable (8) or preinfarction angina (29), evolving infarction (8), recent infarction (less than two weeks before) (5) and refractory ventricular tachyarrhythmia (4). Combined risk factors were present in nine patients. The following principles were utilized to minimize ischemic injury: (1) avoidance of prebypass hypertension and hypotension, (2) avoidance of extreme hemodilution, (3) avoidance of ventricular fibrillation, (4) maintenance of beating empty heart, when possible, (5) the limiting of ischemic periods to less than 12 minutes (hypothermia 32 degrees C) and (6) repaying myocardial oxygen debt with total (vented) bypass, when necessary. The following results were obtained: inotropic support was required in five patients (9 percent), "new" postoperative infarction occurred in five patients (9 percent) and one patient died (2 percent). These results are comparable to those reported in good-risk patients, and indicate that optimal myocardial protection will allow safe revascularization in a high-risk patient.
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PMID:Myocardial revascularization in high-risk coronary patients. 126 12

Eighteen cases of mitral atresia with normal aortic valve plus 68 cases from the literature are analyzed. A new classification based on anatomical findings is proposed. Pulmonary stenosis or atresia is frequent in the type with transposition of the great arteries. The rare instances of normal or large left ventricle are due to a large ventricular septal defect, or to straddling or displaced tricuspid valve. The clinical, radiologic and electrocardiographic findings have been summarized and correlated with the different physiopathological situations. In our catheterized cases an oxygen saturation step-up was found in the right atrium together with left atrial hypertension. In seven cases mitral atresia was demonstrated by selective left atrial contrast injection. The average age at death was six months. Among the cases surviving one year or more, the association of atrial septal defects or pulmonary stenosis was frequent. Enlargement of the interatrial communication, accompanied by other palliative measures, is the only available surgical procedure.
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PMID:Mitral atresia with normal aortic valve: a study of eighteen cases and a review of the literature. 126 15

Patients with essential arterial hypertension demonstrate abnormal vasodilator capacity either during increased cardiac metabolic demand or during pharmacological vasodilation. Structural and functional damage to the coronary microcirculation has been proposed as one of the major causes of impaired coronary reserve in this disease. To assess the role of microvascular impairment in regional myocardial blood flow (MBF), 27 patients with essential hypertension were evaluated by dynamic positron emission tomography (PET) at rest, during atrial pacing and after dipyridamole infusion and compared with 13 healthy subjects. All patients had normal coronary arteries, 17 had moderate to severe hypertension and 10 had mild hypertension. Baseline mean MBF of 0.97 +/- 0.25 ml/min/g was significantly increased to 1.60 +/- 0.38 during atrial pacing and 2.35 +/- 0.95 after dipyridamole infusion (p < 0.01); however, mean flow during atrial pacing and after dipyridamole infusion was significantly lower than in healthy subjects (2.15 +/- 0.73 and 3.71 +/- 0.86 ml/min/g, p < 0.05 and p < 0.01, respectively). The MBF response to atrial pacing and dipyridamole infusion was similarly depressed in patients with mild and severe hypertension. The study was repeated after 6 months of antihypertensive treatment with the calcium antagonist verapamil or the angiotensin converting enzyme (ACE) inhibitor enalapril in a subgroup of 20 patients as part of a randomised, single-blind clinical trial. This study is still in progress; the initial 16 patients treated with verapamil or enalapril showed an obvious improvement in MBF values during atrial pacing and after dipyridamole infusion after 6 months of therapy (mean MBF: 2.10 +/- 0.64 and 2.99 +/- 1.63 ml/min/g, respectively, p < 0.05 vs pretreatment values). In conclusion, obvious impairment of MBF during atrial pacing and after dipyridamole infusion was observed in hypertensive patients with normal coronary arteries and this appeared unrelated to the severity of hypertension. Therapy with verapamil or enalapril improved coronary reserve and MBF response to an increase in myocardial oxygen demand.
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PMID:Regional myocardial blood flow and coronary reserve in hypertensive patients. The effect of therapy. 128 84

The effects of hypoxia and superimposed hypercapnia or hypertension during hypoxia on brain tissue water content, pH, and electric activity were studied in Sprague-Dawley and stroke-prone spontaneously hypertensive rats. Auditory brainstem responses and sensory evoked potentials were recorded during the experiment as the indices for cerebral oxygen metabolism. The brains were removed immediately, 1 day, and 2 days after hypoxic insult for gravimetric study. The brain water content increased in all groups on the 1st and 2nd days after hypoxia. The percentage change from the control water content increased only on the 1st day in hypoxic rats. In contrast, it increased on both the 1st and 2nd days after hypoxia in hypercapnic or hypertensive rats. The evoked potentials of hypoxic and hypercapnic-hypoxic rats showed that peak latencies were prolonged significantly during hypoxia and recovered 1 and 2 days after hypoxia. The brain tissue pH decreased during hypoxia and recovered after hypoxia. This study suggests that brain edema develops within 2 days of hypoxic insult and that superimposed hypercapnia or hypertension promotes the brain edema.
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PMID:The effect of hypoxia on brain edema--the promoting effect of superimposed hypercapnia or hypertension. 128 17

Studies were undertaken to evaluate the fundamental conditions for a low-intensity voluntary wheel running model in rats and its chronic effects on health indexes. Male Fischer rats (SPF) 5 weeks of age were housed in individual sedentary conditions or in individual wheel-cage units which allowed free access to voluntary wheel running for 8 months. Voluntary running averaged 640 +/- 198 m/day, reached a peak (965m) at the 2nd month and waned over time, reaching a plateau after the 6th month (about 400-500m). Exercising rats consumed more food (+23%), but exhibited decreased body weight gains (-9%), suggesting a remarkable lowering of fat. A lowering effect on resting blood pressure (-5%) was also recognized. In addition, preventive effects on oxygen toxicity and effective bactericidal activity of neutrophils and pulmonary alveolar macrophages (PAM) were suggested. Although the amount of exercise in this study was the smallest of the other preceding ones conducted with a voluntary wheel running model, many potential health benefits were recognized. Such health promoting and protective effects by low-intensity voluntary exercise and the harmfulness of forced exercise in rats have been reported in researches on cancer, lowering fat and hypertension. Therefore it is important to set up conditions for low-intensity voluntary running. It was also demonstrated by this study that strictly controlled environmental conditions, such as room temperature and humidity, a 12-hr light-dark cycle and prevention of infection and psychological stress to rats, as well as using male rats, which are more inactive, were important factors to establish this model.
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PMID:[Conditions for low-intensity voluntary wheel running in rats and its chronic effects on health indexes]. 128 62

The use of microelectrode techniques for studying oxygen distribution and blood flow in the eye of a physiologically well maintained rat provides a very convenient model in which to study oxygen supply to the retina. The availability of rat models of vascular disease such as diabetes and hypertension, and the existence of several models of retinal degeneration, make studies of oxygen supply in the rat eye of particular relevance. The experiments reported in this paper demonstrate changes in oxygen distribution and blood flow very early in STZ induced diabetes. Thus, we have established a preparation in which the role of changes in oxygen supply can be correlated with the pathological events that are apparent later in the disease.
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PMID:Oxygen tension and blood flow in the retina of normal and diabetic rats. 128 5

The division of the venous circulation in to two sectors, one constituted by the superficial and deep venous trunks (macrocirculation) and the other by the capillaries and precapillary venules (microcirculation), is surely schematical but aids the comprehension of many hemodynamic effects connected to hampered venous return and to the incompetence of the valvular devices. In fact many of the effects of stasis and venous hypertension (oedema, red cell diapedesis, skin dystrophies) cannot be explained merely by hydraulic mechanisms but require a primary alteration of the microvascular wall associated with structural changes of the perivascular connective tissue. The alterations that occur in microcirculation are of the utmost importance in the formation of the venules ulcerations. The passage of fibrinogen through large pores in the venules of the patients affected by venous hypertension derived from venous insufficiency creates a pericapillary fibrin deposition that cannot be removed because of inadequate blood and tissue fibrinolysis. This accumulation acts as a barrier to the diffusion of oxygen and other nutrients, determining a stasis dermatitis that may lead to tissue necrosis and ulceration. The more precise knowledge of the phenomena connected with the venous stasis at the level of microcirculation (pericapillary fibrin deposition, endothelial ischemia, blocked lymphatic drainage) will not only allow a deeper comprehension of the clinical signs but hopefully will lead to a more effective treatment of the postphlebitic syndrome.
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PMID:[Physiopathology of venous stasis at the microcirculation level]. 129 20


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