Endoscopic sympathectomy impairs forearm cutaneous vascular conductance and sweating responses during passive whole body heat stress

Hyperhidrosis is characterized by excessive sweating, typically in the palmar and axillary regions. Individuals with severe cases of hyperhidrosis can be treated surgically via endoscopic thoracic sympathectomy to disrupt the neural connection between the spinal cord and the affected regions, thereby attenuating sweating in the hyperhidrotic regions. However, the effects of this procedure on skin blood flow and sweating responses to whole body heat stress in regions not targeted by the sympathectomy, such as the forearm, are unknown. We tested the hypothesis that surgical sympathectomy attenuates the increase in forearm cutaneous vascular conductance and sweating during whole body heat stress. Before and 7 ± 1 wk following bilateral thoracic surgical sympathectomy, forearm skin blood flow (laser-Doppler imaging) and local sweat rate (capacitance hygrometry) were assessed during whole body passive heat stress sufficient to elevate core temperature by ∼1°C (P = 0.74 between trials) in 10 subjects (27 ± 3 yr; 7 females). The mean increase in forearm cutaneous vascular conductance was attenuated following sympathectomy (Δ3.67 ± 1.34 flux·mmHg⁻¹ vs. Δ1.62 ± 1.19 flux·mmHg⁻¹; P < 0.01). Similarly, mean sweat rate was attenuated in the palmar (Δ0.68 ± 0.42 mg·min⁻¹·cm⁻² vs. Δ0.20 ± 0.25 mg·min⁻¹·cm⁻²; P = 0.015) and forearm (Δ0.62 ± 0.31 mg·min⁻¹·cm⁻ vs. Δ0.24 ± 0.26 mg·min⁻¹·cm⁻²; P = 0.03) regions following sympathectomy. These data suggest that the increase in forearm cutaneous vascular conductance and sweat rate in response to whole body heat stress is attenuated by ∼50% after surgical sympathectomy. However, the implications of these responses on whole body thermoregulation remain unknown.NEW & NOTEWORTHY Thoracic surgical sympathectomy is often performed to attenuate sweating in the palmar and axillary regions in individuals with hyperhidrosis. However, the effect of this procedure on efferent thermoregulatory responses to heat stress is unknown. We show that the increase in forearm cutaneous vascular conductance and local sweat rate is attenuated during whole body passive heating following a surgical sympathectomy.