Relationships between injury years and thermoregulatory responses during heat stress in spinal cord injury persons.

Abstract

Thermoregulatory responses via sympathetic nerve activity during heat stress are absent or impaired in persons with spinal cord injury. However, relationships between their injury years and responses of sweating and cutaneous vasodilation to increased core temperature remained unknown. Six of cervical (CSCI; N=6; level of C5‐7; injury years of 1–22 yrs) and 8 thoraciolumbal (SCI; N=8; Th4‐L1; 1–24 yrs) spinal cord injury persons and 10 healthy subjects (AB; able‐body) were recruited. They wore water‐perfused suits with taking a supine position and 33‐degree C water was perfused into the suits to make a whole body thermoneutral condition, while all devices were applied. After 10‐min measurements during thermoneutral condition, heat stress was performed with infusion of 47‐degree C water until esophageal temperature (thermocouples) increased by 1 degree C. Mean arterial pressure (MAP; the brachial artery; Korotkoff's method), mean skin (Tsk) and local chest temperatures (Tchest; thermocouples), sweat rate (SR; capacitance hygrometry) and skin blood flow (SkBF; laser‐Doppler velocimetry) on the chest. Cutaneous vascular conductance (CVC) were calculated as SkBF divided by MAP. Tsk was about 35 degree C in all groups and increased by 3 degree C. Tchest increased by 1.4 degree C during heat stress. CVC increased by 4 times as baseline in AB, 3 times in SCI during heat stress, but no increase was observed in CSCI. Patterns of SR in all groups were similar to CVC. Maximal response of CVC [control/degrees] was tended to be negatively correlated, but that of SR [mg/cm2/min] was positively correlated with injury years. In conclusion, thermoregulatory responses to increased core temperature were absent in CSCI and impaired in SCI. In SCI, sweating response on the chest, where sympathetic nerve activity is intact, is possibly enhanced to compensate for reduced cutaneous vasodilation with increased injury year.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.