Showing papers by "Giuseppe Mancia published in 1980"

Blood pressure variability in man: its relation to high blood pressure, age and baroreflex sensitivity

Abstract: 1. Intra-arterial blood pressure and heart rate were recorded for 24 h in ambulant hospitalized patients of variable age who had normal blood pressure or essential hypertension. Mean 24 h values, standard deviations and variation coefficient were obtained as the averages of values separately analysed for 48 consecutive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation aations and variation coefficient were obtained as the averages of values separately analysed for 48 consecurive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for heart rate were smaller. 3. In hypertensive subjects standard deviation for mean arterial pressure was greater than in normotensive subjects of similar ages, but this was not the case for variation coefficient, which was slightly smaller in the former than in the latter group. Normotensive and hypertensive subjects showed no difference in standard deviation and variation coefficient for heart rate. 4. In both normotensive and hypertensive subjects standard deviation and even more so variation coefficient were slightly or not related to arterial baroreflex sensitivity as measured by various methods (phenylephrine, neck suction etc.). 5. It is concluded that blood pressure variability increases and heart rate variability decreases with age, but that changes in variability are not so obvious in hypertension. Also, differences in variability among subjects are only marginally explained by differences in baroreflex function.

Methyldopa and neural control of circulation in essential hypertension.

Abstract: The effects of methyldopa on hemodynamics at rest and on neural control of circulation were studied in subjects with essential hypertension. Blood pressure (recorded intraarterially), heart rate, cardiac output (thermodilution) and total peripheral resistance were measured before and after 15 to 20 days of continuous administration of the drug (500 to 750 mg twice daily). Methyldopa reduced mean arterial pressure (17 percent) and peripheral resistance (25 percent) without signlficantly affecting heart rate and cardiac output. The various cardiovascular responses to stimuli such as dynamic and isometric exercise and exposure to cold were un-changed by treatment with methyldopa, but the peak blood pressure values during these stimuli were lowered by methyldopa because of reduction of baseline values. Stimulation of carotid sinus baroreflexes (by negative air pressure in a sealed chamber enclosing the neck) also caused the same decrease in arterial pressure, peripheral resistance, heart rate and cardiac output before and during methyldopa treatment; on the other hand, the increase in arterial pressure and peripheral resistance caused by inactivation of baroreflexes (positive air pressure in the neck chamber) was somewhat reduced, although not abolished, by therapy with methyldopa. It is concluded that (1) the hypotensive effect of methyldopa is due to systemic vasodilatation; (2) this drug does not interfere with the cardiovascular responses to various neural excitatory stimuli; and (3) it reduces the ability of the carotid baroreflex to compensate for a decrease in blood pressure. Reduction of this pressor response may explain why methyldopa has a greater antihypertensive effect when patients are standing.

Regulation of circulation during antihypertensive treatment with prazosin

Abstract: &NA; Seven patients with uncomplicated essential hypertension were treated with increasing doses of prazosin until a significant reduction of blood pressure was achieved in each of them, and then the effective dose (2‐5 mg, t.i.d) was maintained for 10‐15 days. The effect of prazosin on circulation regulation was studied by comparing haemodynamics at rest, during dynamic and isometric exercise, during cold exposure, and during transient stimulation and inactivation of the carotid sinus baroreflex. Prazosin reduced both mean arterial pressure and peripheral resistance at rest without affecting heart rate and cardiac output. Neurally mediated changes in arterial pressure, cardiac output, and peripheral resistance during the various stimuli employed and during manipulation of the baroreflex were unaffected by the drug, although all blood pressure and peripheral resistance values reached during the various tests were significantly lower during them before treatment because of the lowering of resting values by prazosin. These data indicate that clinically effective doses of prazosin reduce arterial pressure without affecting circulatory homeostasis.