Carotid baroreceptor function in hypertensive patients

Abstract

Carotid baroreceptor function has been studied in twenty-five patients with essential hypertension and in ten normotensive control subjects of corresponding age. The carotid baroreceptors were stimulated by increasing the transmural pressure over the carotid arteries by the application of negative pressure in a box enclosing the neck. Stimulation elicited significant decreases in intra-arterial blood pressure, heart rate and cardiac index in both hypertensive and normotensive subjects. Both groups also showed a significant decrease in stroke index and a significant increase in total peripheral vascular resistance index. The response to carotid sinus stimulation did not differ significantly between the two groups. In fourteen of the hypertensive subjects, carotid baroreceptor function was studied after 4 months of saluretic therapy, mefruside, and in nine of these patients after additional treatment with a beta-receptor blocking drug, alprenolol, for another 4 months. Both mefruside and alprenolol induced a significant decrease in mean arterial blood pressure but the response to the carotid baroreceptor stimulation was not significantly altered. The findings indicate that the carotid baroreceptor is re-set to the actual blood pressure level, with little or no change in gain in hypertensive subjects both without and during hypotensive therapy.

Circulatory effects of carotid sinus stimulation and changes in blood volume distribution in hypertensive man

“…Both blood pressure and heart rate responses to sinusoidal neck suction decreased with increasing mean arterial blood pressure. With regard to the blood pressure response the results differ from previous studies in which (static) neck suction led to unchanged (Wagner, Wacherbauer & Hilger 1968, BevegArd, Castenfors & Danielsson 1977 or even enhanced responses (Mancia et al 1978) in hypertensive compared to normotensive subjects. With regard to the heart rate response the results correspond to those studies in which the arterial baroreceptors were stimulated either by brief (seconds) periods of neck suction (Eckberg 1979), or by transient drug induced blood pressure increases (Gribbin et al 1971, Korner et al 1974, Takeshita et al 1975, Randall et al 1976, Simon et al 1977, Mancia et al 1978.…”

Effect of Mental Stress on Baroreceptor-Mediated Changes in Blood Pressure and Heart Rate and on Plasma Catecholamines and Subjective Responses in Healthy Men and Women

“…In contrast, studies using sustained neck suction to change afferent baroreceptor activity have detected no indication of reduced baroreceptor responses (28)(29)(30). Thus, regarding both hypertension and mental stress, analogous discrepancies between results are obtained in studies analyzing baroreceptor responses to transient as opposed to sustained changes in blood pressure.…”

Carotid baroreflex testing using the neck collar device

“…Babaev et al [2] found that there was a negative correlation between the vasodepressor response to neck suction and the incidence of hypertensive crises. The effects of hypertension on the cardiac responses to neck suction seem less consistent with reports of augmented [55], blunted [79,80] and no differences in the responses [6]. To investigate further the involvement of the baroreflex in hypertension a number of studies have examined the effects of anti-hypertensive drugs.…”

“…Mancia et al [56], however, found no change in response to baroreceptor stimulation (although cardiac responses were measured using the phenylephrine method) but augmented responses to baroreceptor deactivation. Mefruside, alprenolol and clonidine have all been shown to have no effect on the responses to baroreceptor stimulation [6,53].…”

“…Due to their location, carotid baroreceptors are thought to be of particular importance in the maintenance of normal cerebral blood flow during changes in body position. Abnormal baroreflex function has been shown to be associated with several disease states including hypertension [2, 6,55] and coronary heart disease [38,39,63]. Studies of specific baroreceptors in humans have concentrated almost exclusively on those in the carotid sinus, situated close to the bifurcation of the internal and external carotid arteries, because of the relative ease of manipulation.…”