August 1, 1978Open Access
View Full PaperBaroreceptor reflexes in human hypertension.
Structured PICO
How do carotid and extracarotid baroreceptor reflexes controlling arterial pressure and heart rate differ between hypertensive and normotensive humans?
P
Population
46 humans, comprising 35 with hypertension and 11 normotensive controls.
I
Intervention
Alteration of carotid sinus transmural pressure using a variable pressure neck chamber; a subset also received phenylephrine and trinitroglycerine injections to vary extracarotid baroreceptor activity.
C
Comparator
Normotensive controls (n=11).
O
Outcome
Arterial pressure response to graded alterations in carotid sinus transmural pressure.surrogate
This physiological study demonstrates that in hypertension, the carotid baroreflex shifts to favor antihypertensive (depressor) responses, while extracarotid baroreceptor reflexes are significantly diminished.
Abstract
We studied the control of arterial pressure by the carotid sinus baroreceptors in 35 hypertensive humans, using a variable pressure neck chamber to alter carotid sinus transmural pressure in a graded fashion. The results were compared with those obtained from 11 normotensives. As in normotensives, reduction in carotid transmural pressure caused a linearly related pressor response and vice versa. However, whereas in normotensives the pressure response was greater than the depressor, the reverse was the case in hypertensives. Furthermore, the pressor response decreased and the depressor response increased progressively with an increase in severity of the hypertension. Thus while in normotensives the carotid baroreflex is more effective in protecting against hypotension, in hypertensives the antihypertensive function of the reflex is favored. Similar differences between hypertensives and normotensives were found with respect to the carotid baroreceptor control of heart rate. In eight hypertensives, reflex changes in heart rate also were studied by injection of phenylephrine and trinitroglycerine to vary not only carotid baroreceptor activity, but also activity of extracarotid baroreceptors. The results were compared with results of similar studies on eight normotensives. These comparisons suggest that, whereas the carotid baroreceptor reflex remains active in hypertension, reflexes stemming from extracarotid baroreceptor areas are much diminished.