Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. Intersalt Cooperative Research Group.

The relations between 24 hour urinary electrolyte excretion and blood pressure were studied in 10,079 men and women aged 20-59 sampled from 52 centres around the world based on a highly standardised protocol with central training of observers, a central laboratory, and extensive quality control. Relations between electrolyte excretion and blood pressure were studied in individual subjects within each centre and the results of these regression analyses pooled for all 52 centres. Relations between population median electrolyte values and population blood pressure values were also analysed across the 52 centres. Sodium excretion ranged from 0.2 mmol/24 h (Yanomamo Indians, Brazil) to 242 mmol/24 h (north China). In individual subjects (within centres) it was significantly related to blood pressure. Four centres found very low sodium excretion, low blood pressure, and little or no upward slope of blood pressure with age. Across the other 48 centres sodium was significantly related to the slope of blood pressure with age but not to median blood pressure or prevalence of high blood pressure. Potassium excretion was negatively correlated with blood pressure in individual subjects after adjustment for confounding variables. Across centres there was no consistent association. The relation of sodium to potassium ratio to blood pressure followed a pattern similar to that of sodium. Body mass index and heavy alcohol intake had strong, significant independent relations with blood pressure in individual subjects.     

Effect of tryptophan and 5-hydroxytryptophan on the blood pressure of patients with mild to moderate hypertension

Summary Chronic treatment with L-tryptophan (4 g/day) reduced mean blood pressure in 8 of 9 patients with mild to moderate essential hypertension. No significant side effects of treatment were observed. An additional group of 8 patients was treated chronically with L-5-hydroxytryptophan (800 mg/day), the immediate precursor of serotonin. Five of the 8 patients had a significant reduction in mean arterial pressure. No significant side effects of treatment were observed. The reduction of blood pressure accompanying treatment with L-5-hydroxytryptophan suggests that at least a portion of the antihypertensive effect of L-tryptophan is mediated via serotonin.     

Reduction in blood pressure with a low sodium,high potassium,high magnesium salt in older subjects with mild to moderate hypertension.

OBJECTIVE--To examine the effect of a reduced sodium and increased potassium and magnesium intake on blood pressure. DESIGN--Randomised double blind placebo controlled trial. SETTING--General population of a suburb of Rotterdam. SUBJECTS--100 men and women between 55 and 75 years of age with untreated mild to moderate hypertension. INTERVENTIONS--During 24 weeks the intervention group received a mineral salt (sodium: potassium: magnesium 8:6:1) and foods prepared with the mineral salt. Controls received common salt and foods. MAIN OUTCOME MEASURE--Change in blood pressure. RESULTS--Complete follow up was achieved for 97 of the 100 randomised subjects. Systolic blood pressure (mean of measurements at weeks 8, 16, and 24) fell by 7.6 mm Hg (95% confidence interval 4.0 to 11.2) and diastolic blood pressure by 3.3 mm Hg (0.8 to 5.8) in the mineral salt group compared with the controls, with a 28% decrease in urinary sodium excretion and a 22% increase in urinary potassium excretion. Twenty five weeks after the study the difference in blood pressure between the groups was no longer detectable. CONCLUSION--Replacing common sodium salt by a low sodium, high potassium, high magnesium mineral salt could offer a valuable non-pharmacological approach to lowering blood pressure in older people with mild to moderate hypertension.     

The BpTRU automatic blood pressure monitor compared to 24 hour ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension

Background

Increasing evidence suggests that ABPM more closely predicts target organ damage than does clinic measurement. Future guidelines may suggest ABPM as routine in the diagnosis and monitoring of hypertension. This would create difficulties as this test is expensive and often difficult to obtain. The purpose of this study is to determine the degree to which the BpTRU automatic blood pressure monitor predicts results on 24 hour ambulatory blood pressure monitoring (ABPM).

Methods

A quantitative analysis comparing blood pressure measured by the BpTRU device with the mean daytime blood pressure on 24 hour ABPM. The study was conducted by the Centre for Studies in Primary Care, Queen's University, Kingston, Ontario, Canada on adult primary care patients who are enrolled in two randomized controlled trials on hypertension. The main outcomes were the mean of the blood pressures measured at the three most recent office visits, the initial measurement on the BpTRU-100, the mean of the five measurements on the BpTRU monitor, and the daytime average on 24 hour ABPM.

Results

The group mean of the three charted clinic measured blood pressures (150.8 (SD10.26) / 82.9 (SD 8.44)) was not statistically different from the group mean of the initial reading on BpTRU (150.0 (SD21.33) / 83.3 (SD12.00)). The group mean of the average of five BpTRU readings (140.0 (SD17.71) / 79.8 (SD 10.46)) was not statistically different from the 24 hour daytime mean on ABPM (141.5 (SD 13.25) / 79.7 (SD 7.79)). Within patients, BpTRU average correlated significantly better with daytime ambulatory pressure than did clinic averages (BpTRU r = 0.571, clinic r = 0.145). Based on assessment of sensitivity and specificity at different cut-points, it is suggested that the initial treatment target using the BpTRU be set at <135/85 mmHG, but achievement of target should be confirmed using 24 hour ABPM.

Conclusion

The BpTRU average better predicts ABPM than does the average of the blood pressures recorded on the patient chart from the three most recent visits. The BpTRU automatic clinic blood pressure monitor should be used as an adjunct to ABPM to effectively diagnose and monitor hypertension.     

Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. Intersalt Cooperative Research Group.

OBJECTIVES--To assess further the relation in Intersalt of 24 hour urinary sodium to blood pressure of individuals and populations, and the difference in blood pressure from young adulthood into middle age. DESIGN--Standardised cross sectional study within and across populations. SETTING--52 population samples in 32 countries. SUBJECTS--10,074 men and women aged 20-59. MAIN OUTCOME MEASURES--Association of sodium and blood pressure from within population and cross population multiple linear regression analyses with multivariate correction for regression dilution bias. Relation of sample median daily urinary sodium excretion to difference in blood pressure with age. RESULTS--In within population analyses (n = 10,074), individual 24 hour urinary sodium excretion higher by 100 mmol (for example, 170 v 70 mmol) was associated with systolic/diastolic blood pressure higher on average by 3/0 to 6/3 mm Hg (with and without body mass in analyses). Associations were larger at ages 40-59. In cross population analyses (n = 52), sample median 24 hour sodium excretion higher by 100 mmol was associated with median systolic/diastolic pressure higher on average by 5-7/2-4 mm Hg, and estimated mean difference in systolic/diastolic pressure at age 55 compared with age 25 greater by 10-11/6 mm Hg. CONCLUSIONS--The strong, positive association of urinary sodium with systolic pressure of individuals concurs with Intersalt cross population findings and results of other studies. Higher urinary sodium is also associated with substantially greater differences in blood pressure in middle age compared with young adulthood. These results support recommendations for reduction of high salt intake in populations for prevention and control of adverse blood pressure levels.     

Effect of stress management on blood pressure in mild primary hypertension.

OBJECTIVE--To establish whether stress management had a larger effect than a control treatment on resting blood pressure, ambulatory blood pressure, and left ventricular mass. DESIGN--A 12 week baseline period of habituation to measurement of blood pressure was followed by randomisation to either stress management or mild exercise for six months and follow up six months later. SETTING--General practice, district general hospital, and medical school. PATIENTS--Of the 184 patients aged under 60 with mild primary hypertension who entered the baseline habituation period, 88 were excluded because they failed to meet the entry criteria or they withdrew from the study. The remaining 46 men and 50 women underwent treatment. INTERVENTIONS--10 clinical sessions and daily practice at home of either stress management based on relaxation or non-aerobic stretching exercises. Mildly stressful 15 minute interviews before and after treatment. MAIN OUTCOME MEASURES--Diastolic and systolic blood pressure in the clinic and during 12 hours of ambulatory recording, and left ventricular mass measured by echocardiography. RESULTS--The patients'' blood pressure fell during habituation (systolic pressure from 152 mmHg to 140 mmHg, diastolic pressure from 98 to 93 mm Hg), but neither resting nor ambulatory blood pressure was changed by the treatments. Left ventricular mass was also unchanged. Blood pressure rose during the stressful interview, but this rise was reduced by stress management (systolic pressure rose by 7.4 mmHg before treatment and by 3.7 mmHg after treatment). CONCLUSION--Stress management of a type advocated for treating mild primary hypertension is ineffective in lowering blood pressure in patients who are well habituated to measuring blood pressure.     

苯磺酸左旋氨氯地平在治疗老年轻中度高血压中的作用

目的：观察探讨苯磺酸左旋氨氯地平治疗老年轻中度高血压患者的临床疗效和安全性。方法：160例老年轻中度高血压患者随机分为研究组与对照组,研究组给予苯磺酸左旋氨氯地平;对照组给予苯磺酸氨氯地平,治疗过程中进行24h血压监测,总治疗8周为一疗程。结果：研究组4周末和8周末的总有效率分别为78.75%和96.25%,显著高于对照组的53.75%和86.25%,差异有统计学意义（P〈0.05）。治疗前后两组的舒张压和收缩压均有明显降低,其中研究组收缩压平均下降（29.0±3.2）mmHg,舒张压平均下降（15.3±2.3）mmHg,对照组则分别下降（18.5±2.8）mmHg和（9.0±2.5）mmHg,差异具有统计学意义（P〈0.05）。治疗8周末的24h、白昼和夜间的收缩压和舒张压均有明显降低,差异有统计学意义（P〈0.05）,但治疗组下降更明显,与对照组比较差异有统计学意义（P〈0.05）。治疗后两组的脉压均有明显降低,差异具有统计学意义（P〈0.05）,但研究组下降更明显。结论：苯磺酸左旋氨氯地平治疗老年轻中度高血压临床疗效好,不良反应少,且对心脏具有保护功能。     

苯磺酸左旋氨氯地平在治疗老年轻中度高血压中的作用

目的:观察探讨苯磺酸左旋氨氯地平治疗老年轻中度高血压患者的临床疗效和安全性。方法:160例老年轻中度高血压患者随机分为研究组与对照组,研究组给予苯磺酸左旋氨氯地平;对照组给予苯磺酸氨氯地平,治疗过程中进行24h血压监测,总治疗8周为一疗程。结果:研究组4周末和8周末的总有效率分别为78.75%和96.25%,显著高于对照组的53.75%和86.25%,差异有统计学意义(P<0.05)。治疗前后两组的舒张压和收缩压均有明显降低,其中研究组收缩压平均下降(29.0±3.2)mmHg,舒张压平均下降(15.3±2.3)mmHg,对照组则分别下降(18.5±2.8)mmHg和(9.0±2.5)mmHg,差异具有统计学意义(P<0.05)。治疗8周末的24h、白昼和夜间的收缩压和舒张压均有明显降低,差异有统计学意义(P<0.05),但治疗组下降更明显,与对照组比较差异有统计学意义(P<0.05)。治疗后两组的脉压均有明显降低,差异具有统计学意义(P<0.05),但研究组下降更明显。结论:苯磺酸左旋氨氯地平治疗老年轻中度高血压临床疗效好,不良反应少,且对心脏具有保护功能。     

Importance of the renal medullary circulation in the control of sodium excretion and blood pressure

The control of renal medullary perfusion and the impact of alterations in medullary blood flow on renal function have been topics of research interest for almost four decades. Many studies have examined the vascular architecture of the renal medulla, the factors that regulate renal medullary blood flow, and the influence of medullary perfusion on sodium and water excretion and arterial pressure. Despite these studies, there are still a number of important unanswered questions in regard to the control of medullary perfusion and the influence of medullary blood flow on renal excretory function and blood pressure. This review will first address the vascular architecture of the renal medulla and the potential mechanisms whereby medullary perfusion may be regulated. The known extrarenal and local systems that influence the medullary vasculature will then be summarized. Finally, this review will present an overview of the evidence supporting the concept that selective changes in medullary perfusion can have a potent influence on sodium and water excretion with a long-term influence on arterial blood pressure regulation.     

Hypoxic modulation of systolic blood pressure and urinary sodium excretion in spontaneously hypertensive rats after carotid body denervation

To explore the role of arterial chemoreceptors, the effect of hypobaric hypoxia on urinary sodium excretion and systolic blood pressure was investigated in conscious spontaneously hypertensive rats (SHR) with carotid body denervation (CBD) or after sham-operation (SO). Denervation of the carotid bodies was performed by section of the carotid sinus nerves. Exposure to hypobaric hypoxia equivalent to high altitude of 4000 m led to a more pronounced decrease in systolic blood pressure in CBD-rats than in SO-rats. The pattern of urinary sodium excretion observed on the first two days of hypoxia in both groups was not affected by the chemodenervation. It is being suggested that arterial chemoreceptors do not play a critical role in blood pressure and natriuretic responses to hypobaric hypoxia in conscious SHR.     

Renal reflexes in the regulation of blood pressure and sodium excretion

The rich innervation of the kidney is distributed to all structures of renal parenchyma thus providing important anatomical support to the functional evidence that the renal nerves can control kidney functions and send signals on the kidney environment to the central nervous system. Efferent renal nerve fibres are known to influence renal haemodynamics by modifying arteriolar vascular tone, renin release by a direct action on juxtaglomerular cells, and the excretion of sodium and water by changing tubular reabsorption of sodium and water at the different tubular levels. Mechano- and chemo-receptors have been shown in the kidney. Afferent fibres connected with renal receptors convey signals to the central nervous system both at spinal and supraspinal levels. The central areas receiving inputs from the kidney are those involved in the control of cardiovascular homeostasis and fluid balance. Activation of renal receptors by the electrical stimulation of renal afferent fibres were found to elicit both excitatory and inhibitory sympathetic responses. Although the existence of excitatory renorenal reflexes has been suggested, electrophysiological and functional data demonstrate that neural renorenal reflexes exert a tonic inhibitory influence on the tubular sodium and water reabsorption and on the secretion of renin from the juxtaglomerular cells.     

Effect of normal and high sodium diet on the sodium outflow rate through lymphocyte cell membrane and lymphocyte sodium level in patients with mild primary hypertension]

An effect of normal and high sodium diet on the rate of sodium outflow rate through lymphocyte cell membranes was evaluated in patients with mild primary hypertension with normal value of Na+ outflow rate index. It was found that high sodium value does not increase the value of this index in patients with mild primary hypertension but it does increase Na+ levels in lymphocytes. However, high sodium diet increases the value of this parameter in patients with mild primary hypertension with normal value of Na+ outflow rate through lymphocyte cell membranes and does not effect sodium level in the lymphocytes. According to the authors, high sodium diet in patients with normal renal function does not affect serum sodium levels.     

Effects of captopril and enalapril on sodium excretion and blood pressure in sodium-deficient dogs

Inhibition of angiotensin I-converting enzyme (ACE) (kininase II) provides a powerful new method for evaluating the role of the renin-angiotensin-aldosterone and kallikrein-kinin systems in the control of aldosterone secretion, renal function, and arterial blood pressure. This study compares the effects of long-term administration of a sulfhydryl inhibitor, captopril, with a nonsulfhydryl inhibitor, enalapril (1-[N-[1-(ethoxycarbonyl-3-phenylpropyl]-L-alanyl]-L-proline), in conscious sodium-deficient dogs. Plasma aldosterone concentration (PAC), plasma renin activity (PRA), urinary sodium excretion (UNaV), arterial pressure (AP), blood kinins (BK), urinary kinins (UK), and urinary kallikrein activity (UKA) were determined during long-term inhibition of ACE in sodium-deficient dogs. In response to captopril administration (20 mg/(kg . day], PAC decreased from 38.9 +/- 6.7 to 14.3 +/- 2.3 ng/dl, PRA increased from 3.58 +/- 0.53 to 13.7 +/- 1.6 ng/(ml . h), UNaV increased from 0.65 +/- 0.27 to 6.4 +/- 1.2 meq/day, AP decreased from 102 +/- 3 to 65 +/- 2 mm Hg, BK increased from 0.17 +/- 0.02 to 0.41 +/- 0.04 ng/ml, UK increased from 7.2 +/- 1.5 to 31.4 +/- 3.2 micrograms/day, and UKA decreased from 23.6 +/- 3.1 to 5.3 +/- 1.2 EU/day. Quantitatively similar changes in AP, UNaV, and PAC were observed in sodium-deficient dogs in response to long-term enalapril administration (4 mg/(kg X day]. In sodium-deficient dogs maintained on captopril or enalapril for several days, angiotensin II (AngII) infusion (3 ng/(kg X min] restored PAC, UNaV, and AP to levels observed in untreated sodium-deficient dogs. These data indicate that the long-term hypotensive and natriuretic actions of inhibitors of ACE are mediated by inhibition of AngII formation and that the renin-angiotensin system plays an essential role in regulating aldosterone secretion, renal function, and AP during sodium deficiency.     

Effects of essential fatty acids on mild to moderate essential hypertension

A double-blind placebo-controlled study with a crossover design was conducted on 25 non-obese black patients with mild-moderate uncomplicated essential hypertension. They were randomly assigned into two groups. After having received placebo capsules for 4 weeks, they received dietary supplementation with either Efamol-marine (containing desaturated n-6 and n3 essential fatty acids), or sunflower seed and linseed oil capsules for 12 weeks. Thereafter a second 4 weeks placebo phase and a subsequent second 12-week active phase were entered into during which a crossover of the dietary supplementation of the groups was brought about. The mean systolic blood pressure of patients receiving Efamol-marine was significantly lowered after 8 and 12 weeks, while those receiving sunflower/linseed oil supplementation had no significant reduction of blood pressure. This observation may indicate that defective desaturation of the essential fatty acids by the enzyme delta-6-desaturase, could play an important role in the etiology of essential hypertension.     

Effect of mild essential hypertension on control of forearm blood flow during exercise in the heat

Six essential hypertensive (resting mean arterial pressure, MAP greater than 110 mmHg) and eight normotensive (resting MAP less than 95 mmHg) men, aged 30-58 yr, were tested during 1 h of dynamic leg exercise in the heat. Environmental conditions were fixed at 38 degrees C dry-bulb temperature and 28 degrees C wet-bulb temperature; exercise intensity was preset to approximate 40% of each subject's maximal aerobic capacity (actual range 38-43%). Forearm blood flow (FBF) was measured by impedance plethysmography. The intergroup difference in arterial pressure was maintained but not increased or decreased during exercise in the heat. FBF increased in both groups, but the increase was significantly less for the hypertensive subjects. FBF showed a significant linear correlation (different from 0) with core temperature in seven of eight control subjects but in none of the hypertensive subjects. The magnitude of FBF increase was inversely proportional to resting MAP (r = -0.89). It was concluded that essential hypertensive subjects respond to exercise in the heat with a diminished FBF response related to an alteration in control relative to central (core temperature) influences. This may be due to an imbalance between thermal and nonthermal (baroreflex) mechanisms controlling cutaneous blood flow.