Rapid onset of vascular wall protein synthesis with increase in lability of blood pressure in rabbits

Circulatory effects of noise

Thirteen patients with mild essential hypertension, mean age 44 years (range 21-59), were studied during "stress" before and after postsynaptic alpha-adrenoceptor blockade and combined postsynaptic alpha- and non-selective beta-adrenoceptor blockade. Loud broad band noise (100 dBA for 10 min) was used as the stress stimulus. Exposure to noise caused a significant increase in systolic (7%, p less than 0.05), diastolic (9%, p less than 0.01) and mean arterial pressure (6%, p less than 0.01). The blood pressure elevation was caused by an increase in total peripheral resistance (12%, p less than 0.05). There was no significant change in heart rate, stroke volume or cardiac output. The blood pressure response during noise stimulation was not affected by postsynaptic alpha-adrenoceptor blockade (prazosin, 2 mg orally). The hemodynamic reaction pattern, however, was totally reversed. Thus, the cardiac output increased significantly (9%, p less than 0.05), while the total peripheral resistance tended to decrease. Combined postsynaptic alpha- and non-selective beta-adrenoceptor blockade (labetalol, 200 mg orally) inhibited the increase in systolic blood pressure caused by noise, while the diastolic and mean arterial pressures still increased significantly (5%, p less than 0.01). Labetalol effectively blocked the stress-induced increase in total peripheral resistance and there was no significant increase in cardiac output after combined alpha- and beta-adrenoceptor blockade. Exposure to noise caused a significant increase in circulating noradrenaline (20%, p less than 0.05). Plasma adrenaline and plasma renin activity were not affected by noise stimulation. These results suggest that blood pressure elevation is essential during "stress" but that the hemodynamic pattern causing blood pressure elevation may vary and may be affected by pharmacological blockade of various parts of the sympathetic nervous system.

Hemodynamic effects of loud noise before and after central sympathetic nervous stimulation

The hemodynamic effects of loud noise after central alpha 2-adrenoceptor stimulation were studied in 13 patients with mild (WHO 1) essential hypertension. The patients were randomized (double-blind) to treatment with either placebo or guanfacine 1-2 mg for four weeks and then crossed over and treated for another four weeks. All patients were exposed to a loud broad-band noise (105 dBA for 30 min) and all were studied both on placebo and guanfacine. Guanfacine significantly reduced the resting blood pressure from 141/92 to 134/88 mmHg (p less than 0.01) as well as heart rate at rest from 63 to 58 beats/min (p less than 0.05). Noise stimulation caused a significant increase in blood pressure and resistance in the placebo-treated group, while cardiac output decreased significantly. Pretreatment for one month with the central alpha 2-adrenoceptor stimulating agent guanfacine did not block the noise-induced pressor response nor the increase in peripheral resistance. A significant decrease in stroke volume was observed and cardiac output also tended to decrease in this group. It could be concluded that loud noise is a potent pressor stimulus which causes vasoconstriction and that the blood pressure response during noise could not be blocked by the centrally acting antihypertensive agent guanfacine. Since noise causes vasoconstriction it also induces an increased tone in the small arteries and, if the noise stimulus is sufficiently strong and repeated for a long time, it might cause structural changes in the resistance vessels and permanent arterial hypertension in humans.

The role of cold in ischaemic heart disease: a review

A review of the literature suggests that the geographical and social class distribution of ischaemic heart disease (IHD) could be partly explained by variations in degrees of cold exposure, which includes wind and rain as well as temperature, with frequent exposure to cold being more harmful than steady exposure. Blood pressure (BP) and serum cholesterol are raised in response to acute and chronic exposure to cold. Smoking and cold produce similar physiological changes which increase the risk of IHD, while regular exercise blunts the physiological effects of cold and other stresses. There are many acute responses to cold which could trigger a myocardial infarction (MI) and therefore cold is probably a major precipitating factor in many cases of MI. Public health measures to improve domestic housing and the working environment may produce a significant impact on the incidence of IHD.

Comparison of the antihypertensive efficiency of nitrendipine, metoprolol, mepindolol and enalapril using ambulatory 24-hour blood pressure monitoring

In a randomized 6-month study of 201 patients, the antihypertensive efficiency of the calcium antagonist nitrendipine, the beta 1-selective blocker metoprolol, mepindolol, the beta blocker with intrinsic activity and the angiotensin-converting enzyme inhibitor enalapril were compared as monitored by 24-hour ambulatory blood pressure (BP) measurements. The study was designed so that a comparable decrease in casual BP values was obtained with all 4 drugs. If normotension was not achieved with monotherapy, a diuretic also was administered. Pretreatment casual BP and mean 24-hour ambulatory BP values did not differ between the 4 groups. Normotension as assessed by casual BP measurements was observed in all 4 groups after 6 months of therapy, there being no significant differences between the groups. However, significantly more diuretics were required in the mepindolol (n = 14) and in the enalapril (n = 20) groups compared to the nitrendipine (n = 5) and metoprolol (n = 7) groups. Despite comparable casual BP control, the 4 groups differed significantly in their mean 24-hour measurements. The greatest systolic and diastolic BP decreases were seen in the metoprolol group. Metoprolol was also the most effective drug in decreasing the frequency of systolic pressure peaks greater than 180 mm Hg. Both beta blockers and enalapril significantly decreased the morning BP increase compared to the values before treatment, while nitrendipine did not. These data show that casual BP measurement is not a good predictor of 24-hour BP in patients taking hypertensive therapy. Despite an equal degree of "office" BP control, different antihypertensive regimens do not confer the same degree of "nonoffice" BP control.

Efficacy of four antihypertensive drugs (clonidine, enalapril, nitrendipine, oxprenolol) on stress blood pressure

The impact of 4 antihypertensive drug regimens on blood pressure (BP) during everyday life stress and on BP during experimental stress in the laboratory was examined in an open clinical study. Sixty middle-aged men with mild-to-moderate essential hypertension never previously treated were treated either with low-dose clonidine (n = 10), oxprenolol (n = 20), nitrendipine (n = 20) or enalapril (n = 10). Before therapy, all 4 groups did not differ in age, weight, degree of obesity, BP at work site and casual BP measured in the outpatient clinic. After 6 months of effective therapy (casual BP within the normotensive range), casual diastolic BP was identical among the 4 groups, whereas systolic BP was lower in patients treated with clonidine or oxprenolol than in those who received enalapril. A disparate pattern of antihypertensive efficacy among the 4 groups emerged when stress BP was compared, with average ambulatory BP higher in patients receiving clonidine or enalapril than in those who had oxprenolol or nitrendipine. During ambulatory BP monitoring, patients treated with oxprenolol had the lowest level at each level of physical activity and self-reported emotional arousal. During bicycle exercise, patients receiving clonidine had the highest increase in systolic BP and those administered oxprenolol the lowest, whereas the BP response during mental stress was similar among all 4 therapeutic groups. The analysis of the hemodynamic response pattern during mental stress unmasked further disparities. Oxprenolol provoked an abnormal hemodynamic response during mental stress tests (increase in total peripheral resistance), whereas nitrendipine and enalapril preserved the physiological hemodynamic profile (decrease of total peripheral resistance).(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory blood pressure monitoring: practical considerations

Ambulatory blood pressure monitoring (ABPM) allows one to evaluate the blood pressure (BP) profile over a 24-hour period in the patient's natural environment. Casual pressure measurements in the physician's office can be affected by alarm reactions, thus causing "white coat" hypertension. ABPM allows one to evaluate these reactions and determine the average pressure and variability of BP along with the effects of physical activity and emotional arousal on BP patterns while at work, at home, and during sleep. Average pressures determined by ABPM are more predictive of target organ involvement and cardiovascular complications of hypertension than casual monitoring of BP in the clinic. The absence of physiologic decline in arterial pressure during sleep is associated with increased prevalence of atherosclerotic complications and left ventricular hypertrophy as well as impairment of the autonomic nervous system. Although further prospective studies are needed to confirm the benefits of home pressure readings and ABPM, ABPM can be helpful in the diagnosis and determination of prognosis and therapeutic responses in a select group of patients.