Intact blood pressure, but not sympathetic, responsiveness to sympathoexcitatory stimuli in a patient with unilateral carotid body resection

Despite rapidly growing interest in the therapeutic resection of the carotid body ( CB ) chemoreceptors, few physiologic studies exist on the consequences of unilateral CB resection. We present a case of an otherwise healthy postmenopausal female who underwent unilateral CB resection for a paraganglioma. Approximately 4 years postoperatively, she underwent analysis of her sympathetic and hemodynamic responses to hypoxia, lower body negative pressure, cold pressor test ( CPT ), and ischemic hand grip exercise and postexercise ischemia ( IHE / PEI ). Hypoxic ventilatory response and baroreflex sensitivity were relatively normal. Hemodynamic responses to IHE / PEI and CPT showed characteristic increases in cardiac output (from 3.9 L/min to 5.2 L/min [IHE/PEI] and 4.9 L/min [ CPT ]) and blood pressure (from 126/72 mmHg to 161/87 mmHg [ IHE / PEI ] and 171/93 mmHg [ CPT ]). However, muscle sympathetic nerve activity (microneurography of the peroneal nerve) decreased from baseline during IHE / PEI and CPT (burst incidence nadir of 45% and 40% of baseline, respectively) and there was no observable change in total peripheral resistance (from 24 mmHg*min/L to 22 mmHg*min/L [ IHE / PEI ] and 25 mmHg*min/L [ CPT ]). These findings illustrate intact blood pressure responsiveness despite attenuated sympathoexcitation, possibly due to an increase in cardiac output and/or adaptive inhibitory effect of the baroreflex on peripheral sympathetic activity.