ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Studies in unanaesthetized animals have reported that section of the carotid sinus and aortic nerves is accompanied by an increased blood pressure variability but not by a sustained blood pressure rise, thus questioning the role of arterial baroreceptors in the long term control of mean blood pressure values. However, sino-aortic denervation (SAD) does not produce denervation of all baroreceptor areas, and it has been suggested that aortic baroreceptor fibres in the vagus and cardiopulmonary vagal afferents that restrain sympathetic vasoconstrictor tone prevent blood pressure from permanently rising. In unanaesthetized cats we recorded blood pressure intra-arterially for 8-12 h when baroreflexes were intact, 7 days after SAD and 1-2 days after additional bilateral cervical vagotomy. Blood pressure signals were analysed by computer to provide means and coefficients of variation (CV, variabilities) for each recording period. In intact cats, mean blood pressure was 99 ± 7 mmHg (average ± s.e.) and CV 6 ± 1%. SAD did not alter mean blood pressure but markedly increased CV (12 ± 2%;P<0.01). Additional vagotomy did not alter mean blood pressure (104 ± 6 mmHg), nor did it alter the increased CV observed after SAD alone. Vagotomy failed to affect mean blood pressure and CV even when performed in cats with intact carotid and aortic nerves. The lack of effect of vagotomy did not depend on simultaneous section of afferent and efferent fibres, because selective blockade of the latter by atropine also failed to affect mean blood pressure and CV. These data show that neither arterial baroreceptors nor cardiopulmonary receptors have a prolonged effect on mean blood pressure and that not even a combined denervation of these reflexogenic areas can produce sustained blood pressure elevation. A prolonged effect of this denervation is a marked increase in blood pressure variability. This is exclusively due to arterial baroreceptor denervation, as cardiopulmonary receptors do not appear to exert any buffering action on blood pressure variability.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Determinations of central venous pressure, cardiac haemodynamics and rapid volume expansion using iso-oncotic dextran were made in 49 men with sustained, uncomplicated essential hypertension and compared with those in 27 normotensive subjects of the same age and sex. In the hypertensives, central venous pressure was significantly increased in basal conditions while the cardiac index was normal and total blood volume was reduced. There was a positive and significant correlation of central venous pressure with age, arterial pressure and pulmonary wedge pressure. After rapid volume expansion, the slope of the curve relating cardiac output to central venous pressure was within the normal range, while the slope of the curve relating blood volume to central venous pressure was significantly reduced. The study provided evidence that in hypertensives: (1) central venous pressure as well as arterial pressure is increased, (2) the elevated central venous pressure is not due to an alteration in the cardiac 'pump function' or to hypervolaemia but rather to a decrease in the compliance of the venous bed or the left ventricle or both, and (3) the strong correlation with age of the venous disturbances is similar to that found for the arterial side of the circulation.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Evidence has been produced that average 24-h or day-time blood pressure (BP) values provide a better diagnosis of hypertension and a better prediction of its risk than BP values provided by one or few isolated measurements. This has led to a number of attempts to simplify the time-consuming procedure necessary to obtain this information and to identify short periods during the 24 h when average BP might closely reflect the 24-h or day-time average values. In 40 ambulant subjects BP was recorded intra-arterially for 24 h using the Oxford method. The BP signal was analysed beat-to-beat by a computer to obtain the average 24-h mean BP values. This value was compared with the mean BP average values obtained by beat-to-beat analysis of subperiods of the same recording, ranging from 30 min to 12 h in duration. For each duration the analysis was performed on 48 different subperiods, each shifted by 30 min from the preceding one, so that every time interval within the 24 h was considered. Throughout the 24-h period the average mean BP values obtained by the analysis of the 30-min subperiods showed very marked differences compared to the 24-h mean BP average. The differences between the subperiod and 24-h values showed a progressive reduction as the subperiod duration was increased. Their magnitude, however, was still marked for subperiods of 2 and 4 h, and only showed a clear-cut attenuation when the subperiods encompassed 12 h. The magnitude and the sign of all the subperiod and 24-h differences showed a large variability among subjects. Similar results were observed when the comparisons were between day-time subperiods and the corresponding day-time average value. These findings demonstrate that average BP values obtained by monitoring BP over a period of a few hours during the day or night cannot provide a precise estimate of the 24-h or the day-time average BP. This rules out the possibility of shortening the procedure necessary to obtain this important information.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

A study was carried out to evaluate the relationship between blood pressure, plasma renin activity, serum aldosterone and patterns of urinary sodium and potassium excretion rates in urban Zulus, rural Zulus and Indians in order to explain the high prevalence of hypertension in the urban adult Zulu (25%) compared to the rural adult Zulu (10%). Urinary sodium and potassium were not significantly different between urban and rural Zulus. There was no association between sodium excretion and blood pressure. Urinary potassium correlated negatively with blood pressure in rural Zulus and Indians but not in urban Zulus. The urinary sodium:potassium ratio was significantly lower in rural Zulus than in urban Zulus. The sodium:potassium ratio of Indians was not significantly different from that of Zulus. Plasma renin activity levels were significantly lower in urban than in rural Zulus. This difference is an enigma but may be due to an environmental factor. Serum aldosterone correlated positively with plasma renin activity and negatively with the urinary sodium:potassium ratio.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Hypertension withdiabetes mellitushas been associated with suppression of the renin-angiotensin-aldosterone system. We have studied the effects of the converting enzyme inhibitor, captopril, on blood pressure, plasma renin activity (PRA) and plasma aldosterone in 10 stable hypertensive diabetic subjects and 10 age-matched patients with essential hypertension. There was no clinical evidence of complication in the diabetic subjects and their diabetic treatment remained unchanged throughout the study. Mean captopril doses used were similar in both groups. In the diabetics and the essential hypertensives, treatment resulted in a significant and similar decrease in blood pressure. Pre-treatment basal and stimulated PRA and the change of PRA with captopril were also similar. Pre-treatment stimulated plasma aldosterone and the response of aldosterone to postural stress was significantly lower in the diabetic group, suggesting an impaired adrenal responsiveness to stress. Despite this, our findings indicate that the hypotensive action of captopril is at least as effective in hypertension associated with otherwise uncomplicateddiabetes mellitusas in essential hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Factory workers aged 16-64 years were screened for ethnic differences in blood pressure. The 78% response rate was evenly spread between whites (439 men; 164 women), black West Indians (173 men; 101 women) and Asians (172 men). Mean systolic and diastolic pressures by age decade in men were similar in all three groups, but there was a modest excess of both higher and lower blood pressures in blacks and Asians. Older black women had higher blood pressures than whites, but body mass indices were 2-5 kg/m2greater. Multiple regression analysis revealed no significant effect of ethnic group on either systolic or diastolic blood pressure variance and that the higher pressures in black women were accounted for by differences in age and body mass index. The influence of body mass index was more marked on diastolic than systolic pressure. In men, alcohol intake and a family history of hypertension had small independent positive effects on systolic pressure. The lack of black/white difference in blood pressure differs from the United States results and may be due to the similarity in social class of participants. This should be confirmed in further population samples with larger numbers of black (and Asian) subjects.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

We have previously shown that rats housed in individual metabolism cages develop arterial hypertension and that this can be prevented by adrenalectomy. In the present work the influence of adrenalectomy on blood pressure, heart rate and on fluid and electrolyte balance was investigated in rats with established isolation-induced hypertension. Seven days after adrenalectomy, systolic blood pressure was reduced to levels similar to those seen before the induction of hypertension; the fall in blood pressure was accompanied by tachycardia. It is likely that the reduction in blood pressure was partly due to volume depletion, since adrenalectomized rats showed reductions in fluid, sodium and potassium balance during the first week after operation. Over the following 3 weeks, blood pressure and heart rate returned to pre-operative hypertensive levels, associated with increasingly positive balances for fluid and sodium. Maintenance of elevated blood pressure in isolated rats following adrenalectomy is likely to have been aided by activation of the renin-angiotensin system, since infusion of saralasin caused profound hypotension in these circumstances, whereas it had a slight pressor effect in intact rats with isolation-induced hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1985

数据来源: OVID