Effect of Bilateral Carotid Body Resection on Cardiac Baroreflex Control of Blood Pressure During Hypoglycemia

Abstract

Hypoglycemia results in a reduction in cardiac baroreflex sensitivity and a shift in the baroreflex working range to higher heart rates. This effect is mediated in part by the carotid chemoreceptors. Therefore, we hypothesized hypoglycemia-mediated changes in baroreflex control of heart rate would be blunted in carotid body resected patients when compared with healthy controls. Five patients with bilateral carotid body resection for glomus tumors and ten healthy controls completed a 180-minute hyperinsulinemic, hypoglycemic (~3.3 mmol.L−1) clamp. Changes in heart rate, blood pressure, and spontaneous cardiac baroreflex sensitivity were assessed. Baseline baroreflex sensitivity was not different between groups (p>0.05). Hypoglycemia resulted in a reduction in baroreflex sensitivity in both groups (Main effect of time, p<0.01) and responses were lower in resected patients when compared with controls (Main effect of group, p<0.05). Hypoglycemia resulted in large reductions in systolic (−17±7 mmHg) and mean (−14±5 mmHg) blood pressure in resected patients that were not observed in controls (Interaction of group and time, p<0.05). Despite lower blood pressures, increases in heart rate with hypoglycemia were blunted in resected patients (Interaction of group and time, p<0.01). Major novel findings from this study demonstrate that intact carotid chemoreceptors are essential for increasing heart rate and maintaining arterial blood pressure during hypoglycemia in humans. These data support a contribution of the carotid chemoreceptors to blood pressure control and highlight the potential widespread effects of carotid body resection in humans.

Variable role of carotid bodies in cardiovascular responses to exercise, hypoxia and hypercapnia in spontaneously hypertensive rats

“…) and that of others (Limberg et al . ), unilateral carotid body ablation lowered arterial pressure in some patients, which was well maintained at 3 and 6 months of follow‐up with some showing a relapse by 12 months; the relapse may reflect compensation from the contralateral carotid body. Nevertheless, preservation of the contralateral carotid body may be necessary to preserve protection against hypoxia in these patients, especially during sleep.…”

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

“…Afterwards, she performed isometric hand grip exercise and postexercise ischemia (IHE/PEI) and cold pressor test (CPT) as sympathetic stimuli (Victor et al 1987). Measures of heart rate (HR), blood pressure (BP), minute ventilation, and muscle sympathetic nerve activity (MSNA, microneurography of the peroneal nerve) were obtained during these tests (Limberg et al 2015). Measures of HR variability (HRV), cardiac output (CO), and total peripheral resistance (TPR) were calculated using three lead electrocardiography, finger photoplethysmography, and off-line analysis with custom software (WinCPRS, Version 1.163, Absolute Aliens Oy, Turku, Finland) (Limberg et al 2016).…”

Role of the carotid body chemoreceptors in glucose homeostasis and thermoregulation in humans

“…Other work by our group in bilaterally resected patients has shown that although resting baroreflex function is relatively normal, significant impairments in baroreflex sensitivity are uncovered during stress (hypoglycaemia) (Limberg et al . ). Together these data suggest there may be unforeseen autonomic consequences of CB resection, even in relatively healthy adults.…”