Whole body measurements of sodium turnover in offspring of patients with sustained essential hypertension

Blood pressure, cardiac output and systemic vascular resistance during rest, muscle work, cold pressure test and psychological stress. A study of male offspring from families with a history of essential hypertension for at least two generations

Haemodynamic changes in the early phases of hypertensive diseases have mainly been described in so-called borderline hypertensives. Their cardiac output (CO) has mostly been found to be elevated, but the peripheral vascular resistance (PRI) normal. In this study of the offspring (26 subjects) of hypertensive individuals, CO and intravascular pressures were measured during rest, muscular work, psychological stress and cold pressure test. For comparison, the same measurements were performed in a control group of healthy volunteers without known hypertension in their families. The offspring had higher blood pressure at rest than the controls throughout the study except during the cold pressure test and the highest dynamic work loads. Although there was no statistically significant difference between offspring and controls as regards PRI, the resistance was slightly higher in the group of offspring throughout the study. Arterial blood pCO2 in offspring was significantly lower at rest, during psychological stress and dynamic muscle work. Possible mechanisms behind this finding are considered.

Venous volume and blood flow in hand at rest and during psychological stress in male relatives to hypertensive patients

A total of 19 male relatives to hypertensive individuals were examined with regard to blood flow and venous volume in the hand at rest and during a psychological stress test. They were compared to 19 male controls without heredity for hypertension. There were no significant differences between the groups in hand blood flow or venous volume either at rest or during the test. The increase in vascular resistance during psychological stress was significantly higher in relatives than in controls. Possible mechanisms behind the differences in arterial vascular reactivity between the groups are discussed.

Sodium elimination rate and blood pressure during normal and high salt intake in subjects with and without familial predisposition to hypertension

We have assessed the elimination rate of 22Na (ER-22Na), total exchangeable sodium (NaE), blood pressure, plasma volume (PV), haematocrit, urinary noradrenaline (U-NA) and urinary 3-methoxy-4-hydroxymandelic acid (U-VMA) in normotensive men with (n = 17) and without (n = 15) familial predisposition to hypertension. All measurements were done during habitual salt intake and after four weeks of increased salt intake (ordinary intake + 12 g NaCl/daily). On ordinary salt intake, ER-22Na, NaE, blood pressure, PV, haematocrit, U-NA and U-VMA did not differ between the groups thus indicating a normal sodium turnover in both groups and a comparable activity of the sympathetic nervous system. After 10 days of high salt intake those without familial predisposition showed signs of volume expansion and decreased sympathetic activity and those with such predisposition showed insignificant changes in the same direction. After four weeks of increased salt intake, ER-22Na had increased significantly and equally in both groups, while blood pressure and NaE remained unchanged. This indicates that the predisposed individuals had a normal ability to cope with a prolonged increase in salt intake.

Efficacy of potassium and magnesium in essential hypertension: a double-blind, placebo controlled, crossover study

OBJECTIVE

To evaluate the antihypertensive activity of potassium given alone or in combination with magnesium in patients with mild hypertension.

DESIGN

A double blind, randomised, placebo controlled, crossover trial of 32 weeks' duration.

SETTINGS

Cardiology outpatient department, Sassoon General Hospitals, Pune, India.

PATIENTS

37 Adults with mild hypertension (diastolic blood pressure less than 110 mm Hg).

INTERVENTION

Patients received either placebo or potassium 60 mmol/day alone or in combination with magnesium 20 mmol/day in a crossover design. No other drug treatment was allowed.

MEASUREMENTS

Blood pressure and heart rate assessed at weekly intervals and biochemical parameters at monthly intervals.

RESULTS

Potassium alone or in combination with magnesium produced a significant reduction in systolic and diastolic blood pressures (p less than 0.001) and a significant reduction in serum cholesterol concentration (p less than 0.05); other biochemical variables did not change. Magnesium did not have an additional effect. Urinary potassium excretion increased significantly in the groups who received potassium alone or in combination with magnesium. The drug was well tolerated and compliance was satisfactory.

CONCLUSION

Potassium 60 mmol/day lowers arterial blood pressure in patients with mild hypertension. Giving magnesium as well has no added advantage.

Effect of magnesium on blood pressure

Twenty patients receiving long term diuretic treatment for arterial hypertension (18 patients) or congestive heart failure (two patients) received magnesium supplementation as aspartate hydrochloride 15 mmol/day for six months. Both systolic and diastolic pressures decreased significantly, by a mean of 12/8 mm Hg. No significant changes were recorded in plasma or urinary electrolytes except for magnesium, 24 hour urinary volumes, or body weight after treatment. The effect of magnesium on blood pressure may be direct or through influences on the internal balance of potassium, sodium, and calcium.