Cardiovascular Effects of Direct Stimulation of the Carotid Sinus Nerve in Man.

Abstract

Summary. Direct stimulations of the carotid sinus nerve have been performed in man during operations of tumours in the neck. Definite reflex responses were obtained already at low stimulation rates, with maximal effects around 40–60 impulses per sec. A reflex bradycardia and a blood pressure fall with a decreased pulse amplitude was obtained. Concomitantly there was a marked fall in resistance to blood flow within the forearm vascular bed. The fall in pulse pressure is in all probability due to a decreased stroke volume, secondary to a reduced venous return when the capacity vessels are widened, and to an dimination of the positive inotropic effect on the heart, as a consequence of the generalized reflex inhibition of sympathetic tone. Stimulation of the cranial sympathetic trunk gave no evidence of any activation of the carotid baroreceptors, secondary to increased intramural tension, as has been reported in some animal species.