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

Intracranial haemodynamics were studied in 20 patients with diffuse and focal brain injury and experimental animals with acute intracranial hypertension by the use of TCD ultrasound. The mean flow velocity in the middle cerebral artery (MCA) commonly decreased on the side of the haematoma depending on intracranial pressure (ICP) elevation and cerebral perfusion pressure (CPP) reduction in focal injury. The decrease of the MCA flow velocity returned to normal after treatment. The flow velocities decreased bilaterally and there was no difference between the right and left side in diffuse injury. But the velocities increased in spite of ICP elevation when diffuse cerebral swelling developed. Cerebrovascular CO2 reactivity was impaired in two groups of patients with low Glasgow Coma Scale (GCS) scores. The mean velocity of the MCA and blood flow in the internal carotid artery exhibited flow patterns which changed correlatively depending on CPP reduction in experimental animals. Noninvasive study by use of TCD ultrasound can provide valuable information on variant haemodynamic phenomena in patients with diffuse and focal brain injury.
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PMID:Intracranial haemodynamics in diffuse and focal brain injuries. Evaluation with transcranial Doppler (TCD) ultrasound. 209 9

Endothelial cells modulate vascular tone by releasing endothelium-derived relaxing (EDRF) and contracting factors. An imbalance of these factors in hypertension could contribute to increased peripheral vascular resistance. Mesenteric resistance arteries of Wistar-Kyoto (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) were suspended in a myograph filled with physiological salt solution (37 degrees C; 95% O2-5% CO2). In WKY rings contracted with norepinephrine, acetylcholine (10(-9)-10(-4) M) evoked endothelium-dependent relaxations (88 +/- 2%, IC50 7.3 +/- 0.1; n = 31). Hemoglobin (10(-5) M) but not meclofenamate (10(-5) M) reversed the relaxations delineating EDRF as the mediator. Nitric oxide (3 X 10(-9)-10(-5) M) induced comparable relaxations as acetylcholine. In SHRSP, relaxations to acetylcholine but not those to nitric oxide were impaired (61 +/- 5%, IC50 greater than 6.6 +/- 0.4; n = 24; P less than 0.005). In SHRSP, meclofenamate but not the thromboxane synthetase inhibitor CGS 13080 normalized endothelium-dependent relaxations. Relaxations to sodium nitroprusside were enhanced in SHRSP both in rings with and without endothelium. Thus our results are compatible with the concept that endothelium-dependent relaxations in resistance arteries are mediated by nitric oxide. In SHRSP, endothelium-dependent relaxations are impaired because of a cyclooxygenase-dependent substance interfering with the release and/or action of EDRF.
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PMID:Impaired endothelium-dependent relaxations in hypertensive resistance arteries involve cyclooxygenase pathway. 210 97

To investigate the diagnostic value of carbon dioxide arteriograms in patients with peripheral vascular disease, ten patients in whom standard contrast arteriography was contraindicated underwent carbon dioxide digital subtraction arteriography. Lower extremity ischemia or severe hypertension with renal insufficiency were the indications for arteriography. Standard contrast arteriography was precluded by chronic nondialysis-dependent renal insufficiency, severe congestive heart failure or contrast hypersensitivity. All critical arterial segments were well visualized with the exception of the infrapopliteal arterial tree in three patients. Adequate imaging of this segment required the addition of 20 cc of dilute nonionic contrast. Guided by carbon dioxide digital subtraction arteriography, four percutaneous transluminal angioplasties and three reconstructive procedures were successfully performed. One patient did not have surgically reconstructible disease and two had renal arteries without critical stenoses. Renal function transiently deteriorated in one patient who received 20 cc of nonionic contrast. No adverse events occurred due to carbon dioxide. Clinically useful diagnostic arteriograms are possible using carbon dioxide as the contrast agent.
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PMID:Carbon dioxide digital subtraction arteriography: a pilot study. 212 Dec 15

In order to clarify the cerebrovascular response in Moyamoya disease, the autoregulation and CO2 response was investigated using the 81mKr continuous cerebral blood flow (CBF) measurement technique. A total of 32 measurements were made over the anterior and posterior circulation in 16 Moyamoya patients (seven adults, nine children). CBF measurements were made during four loading trials (hypertension, hypotension, CO2 inhalation and hyperventilation). Study was then made of the vascular response of the frontal lobe, perfused by the internal carotid artery (ICA), and the occipital lobe and cerebellum, perfused by the vertebral artery (VA). Deficits of autoregulation were more severe among the juvenile cases in response to hypotension than to hypertension in both the ICA and VA regions, but the deficits were mild. The CO2 response to hypercapnea in the juvenile cases tended to be abnormal in both the ICA and VA regions. Both adult and juvenile patients showed deficits in the ICA region in response to hyperventilation, some of whom exhibited paradoxial responses. Notable differences in the severity of the deficits of the vascular response in adult and juvenile cases were seen, with the deficits in the response being more severe among the juvenile cases. Moreover, significant regional differences in the deficits were also found.
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PMID:Cerebral blood flow in moyamoya disease. Part 2: Autoregulation and CO2 response. 212 2

In order to gain more insight into the pathophysiology of extracerebral cerebrovascular occlusion, the cerebral hemodynamic behaviour after uni- or bilateral carotid occlusion was investigated. In Wistar rats, acute occlusion of one common carotid artery leads to a moderate bilateral lowering of the resting hemispheric brain blood flow; no interhemispheric perfusion asymmetry is observed. During hypercapnia, however, a manyfold increase of the hemispheric blood flow is seen at the intact side, whereas blood flow increase at the side of the occlusion is suppressed indicating that the cerebrovascular reserve at the side of the occlusion is largely used to preserve resting hemispheric perfusion. During the days (1, 5, 15 and 30) following the occlusion, resting hemispheric blood flow is progressively restored rather rapidly (bilateral normalization on the fifth day) whereas restoration of the cerebrovascular reserve (hemispheric blood flow increase in hypercapnia) proceeds more slowly and a nearly normal hypercapnic response is reached on day thirty. Spontaneously Hypertensive Rats (SHR) show structural abnormalities of their blood vessels during the development of hypertension, leading to impaired adaptation possibilities of the cerebral vasculature after unilateral common carotid occlusion. This is indicated by the striking comparability of the compensation of hemispheric cerebral blood flow (in normo- and hypercapnia) of SH rats five days after unilateral carotid occlusion with the cerebral hemodynamic status of normotensive animals already seen 24 hours after the same occlusion. Consecutive bilateral common carotid occlusion shows that survival rate increases by increasing the interval between both occlusions. This survival relation is much more unfavorable in SH rats. The parallelism between the restoration of the measured CO2-reactivity of the blood flow in the involved hemisphere after unilateral carotid occlusion and the evolution of survival rate after consecutive bilateral carotid occlusion indicates that the response of the hemispheric circulation to CO2 offers a good estimate of true cerebrovascular reserve after cerebrovascular accidents of this kind. In cats, acute bilateral occlusion of the carotid arteries leads to a moderate decrease of resting cerebral blood flow in the anterior parts of the brain (cerebrum); the hypercapnic response of this region is, however, completely abolished. In the posterior brain regions (medulla oblongata and cerebellum) resting blood flow and its increase under hypercapnia are preserved. The experiments indicate that the relative preservation of resting cerebral blood flow in the cerebrum of the cat after acute bilateral carotid occlusion is at the expense of its complete hemodynamic reserve. Posterior brain regions are better protected in these conditions.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Hemodynamic adaptations in proximal cerebrovascular occlusion]. 212 47

Response to CO2 and autoregulation of cortical cerebral blood flow (CBF) during isoflurane anesthesia were studied in 10 patients undergoing neurosurgery. The patients were anesthetized with 0.5 to 1.2% end-tidal isoflurane and 66% nitrous oxide in oxygen. The CBF was measured by thermal diffusion using a flow probe with a Peltier stack. PaCO2 was controlled to produce hypocarbia, normocarbia and hypercarbia by changing tidal volume and respiratory rate. Arterial blood pressure was altered. Hypotension was achieved by intravenous infusion of trimetaphan and hypertension was induced by intravenous administration of metaraminol. During isoflurane anesthesia the response to CO2 of CBF was kept at PaCO2 between 27.8 and 53.9 mmHg. The following relationship was obtained. CBF = 2.54 x PaCO2-53.0, r = 0.59, n = 131 The autoregulation of CBF was evaluated in 7 patients, and in 2 patients, the autoregulation of CBF was abolished.
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PMID:[Response to CO2 and autoregulation of cortical cerebral blood flow during isoflurane anesthesia]. 212 31

Studies were carried out to examine the relationship between blood pressure lowering using the Ca2+ channel blocker verapamil, and regression of ventricular hypertrophy, in the spontaneously hypertensive rat (SHR). Untreated male SHR showed rapidly developing hypertension (systolic pressure 194 +/- 2 mm Hg, 109 days of age) and moderate ventricular hypertrophy. Verapamil (Calan-SR, G.D. Searle Co.) treatment for 30 days at maximum doses of 18.7 and 49.9 mg/kg per day supplied in the food, lowered blood pressure maximally 37 mm Hg. The drug had no effect on heart rate. Decrease in the mass of the left ventricle plus interventricular septum was positively correlated with the verapamil-induced decrease in blood pressure (r = 0.69, P less than 0.001). SHR exposed continuously to 500 ppm carbon monoxide (CO) for 30 days showed a similar decrease in blood pressure (33.0 mm Hg). Such SHR, however, displayed increases in mass of the left ventricle plus septum and right ventricle, and of hematocrit, nearly identical to same age Sprague-Dawley rats similarly exposed to CO. Neither verapamil nor CO treatment altered myocardial water content. The results suggest that a modest lowering of blood pressure with verapamil in the SHR produces a relatively rapid decrease in left ventricular mass. It also shows that even when afterload is reduced in the SHR, as with CO, substantial ventricular hypertrophy develops, probably because of augmented preload, and that it is comparable to that produced in non-hypertensive rats.
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PMID:Effects of verapamil and carbon monoxide on blood pressure and heart mass in the spontaneously hypertensive rat. 214 23

This study was designed to determine the cytoplasmic pH (pHi) profile of lymphocytes from a rat model of genetic hypertension that is well suited for study before and after the development of spontaneous hypertension. For this purpose, pHi was measured in thymic lymphocytes obtained from spontaneously hypertensive rats (SHR) and from age-matched Wistar-Kyoto (WKY) control rats using 2',7'-bis carboxyethyl-5,6-carboxyfluorescein (BCECF), a pH-sensitive fluorescence probe. At the age of 16-20 weeks, pHi of lymphocytes suspended in a HCO3-free HEPES-buffered solution, was markedly lower in the SHR than in the WKY rats (7.07 +/- 0.02, n = 16 and 7.22 +/- 0.01, n = 15, respectively, p less than 0.001), whereas systolic blood pressure was higher in SHR than in WKY rats (175 +/- 5.0 and 105 +/- 3.0 mm Hg, respectively, p less than 0.001). In rats less than 5 weeks of age, pHi was also lower in SHR than in WKY rat lymphocytes (7.12 +/- 0.04, n = 11 and 7.23 +/- 0.04, n = 11, respectively, p less than 0.05), although at this age systolic blood pressure was not different between the two groups (87 +/- 4.0 and 85 +/- 3.0 mm Hg, respectively). In lymphocytes suspended in a more physiological HCO3/CO2-buffered solution, pHi was again lower in the adult SHR than in the WKY rat (7.18 +/- 0.02, n = 16 and 7.31 +/- 0.02, n = 16, respectively, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1990 Jan
PMID:Reduced intracellular pH in lymphocytes from the spontaneously hypertensive rat. 215 99

The amplitude of respiratory sinus arrhythmia (RSA) while breathing quietly was measured in 32 mildly hypertensive subjects and in 28 normotensive controls. In 35 subjects, the RSA amplitude in response to rebreathing carbon dioxide was also measured. The RSA amplitude while breathing quietly was smaller in the hypertensive group, particularly in the subjects having the highest levels of diastolic blood pressure. The breathing rate was greater and the heart period (R-R interval) shorter in the hypertensive subjects. After adjusting for differences in the breathing rate, the RSA amplitude was similar in both groups, but the heart period remained shorter in the hypertensive subjects. These findings suggest that breathing style may contribute to a reduction in parasympathetic cardiac control in mild hypertension.
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PMID:Parasympathetic cardiac control in mild hypertension. 216 Apr 96

In order to evaluate the hemodynamic effect of a carotid artery obstruction, the CO2-reactivity was determined and the systolic carotid artery pressure was measured in 34 patients with a stenosis (20) and/or an occlusion (17) of the internal carotid artery. In 19 patients this was done bilaterally and in 15 unilaterally, a total of 53 observations. A decreased CO2-reactivity was found in 49% (26/53). With a carotid artery blood pressure of less than or equal to 90 mmHg the reactivity Index was diminished in 86% (12/14), with greater than 90 mmHg in 36% (14/39) of cases. It is assumed that in the first mentioned situation the autoregulation tends to be exhausted owing to a fall in perfusion pressure while in the last mentioned the explanation may be ischemic damage or shift of the lower limit of autoregulation towards a higher value as a result of (chronic) hypertension.
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PMID:Cerebral perfusion pressure and CO2-reactivity in the evaluation of carotid obstructions. 216 95


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