Cardiovascular responses to stress after carotid baroreceptor denervation in humans

Iatrogenic bilateral denervation of carotid sinus baroreceptors may occur as a complication of carotid body tumor resection and radiation therapy of the neck. The acute phase of the resulting syndrome of baroreflex failure is characterized by a limited blood pressure buffering capacity against excessive rise or fall in response to emotional and physical stimuli like sexual arousal and cold. Paroxysms of severe hypertension and tachycardia, accompanied by excessive increments in sympathetic tone and catecholamine plasma levels, were ascribed to loss of tonic inhibitory influence of baroreceptors on sympathetic tone. Bilateral anesthetic blockade of baroreceptor afferent nerves was shown to result in a strong increase in muscle sympathetic nerve activity and disruption of its normal patterning. This chapter reviews our findings on the long-term effects of iatrogenic baroreflex trauma on the hemodynamic responses to pharmacological, physical, and emotional stress in the autonomic function laboratory as well as under daily life conditions. Chronic attenuation of baroreflex sensitivity after carotid body tumor resection and neck irradiation results in an increased blood pressure variability. However, unopposed sympathetic activation in response to physical and emotional stress appears to be limited to the acute phase of baroreflex failure.