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Acute Heat Exposure Results in an Appropriate Initial Decrease in Core Body Temperature in Subjects with Higher Levels of Spinal Cord Injury, but the Thermal Homeostatic Response to More Prolonged Heat Exposure is Insufficient
Author(s) -
Kumar Nina S.,
Graham Marin,
Leung Patricia,
Tittley Tishina D.,
Tascione Oriana F.,
Bauman William A.,
Handrakis John P.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.592.4
Subject(s) - core temperature , spinal cord injury , medicine , heat illness , thermoregulation , spinal cord , hyperthermia , rectal temperature , anesthesia , physics , psychiatry , meteorology
Study Objective To determine the initial (30 minutes) and more prolonged (60 & 90 minutes) response to heat exposure in individuals with higher levels of spinal cord injury (Hi‐SCI; ≥thoracic level‐4). Methods Sixteen persons with Hi‐SCI (C4‐T4, AIS A‐B) and 16 age and body mass index‐matched AB controls were acclimated in a 27°C baseline (BL) room before being transitioned to a 35°C chamber for 90 minutes (Heat Challenge). Tcore (rectal temperature) was continuously measured throughout the Heat Challenge, and sweat rates of the upper extremities (SRUE) and lower extremities (SRLE) were measured at BL and then at 30‐minute intervals. Results At BL, the average Tcore of the Hi‐SCI group was lower than that of the AB group (36.8±0.45°C vs. 37.35±0.27°C; p=0.0003, respectively). From BL to 30 minutes of Heat Challenge, in both Hi‐SCI and AB groups, a significant decrease (p<0.001) in Tcore (Hi‐SCI and AB: 36.57±0.47°C; 37.07±0.20°C, respectively) was accompanied by increases in SRUE for both Hi‐SCI and AB groups (63.77±83.15%; p=0.008 and 202.98±412.47%; p=0.068, respectively). SRLE also increased in the AB group from BL to 30 minutes (138.25±227.96%; p=0.028). From 30–60 minutes of Heat Challenge in the Hi‐SCI group, SRUE increased significantly (32.34±54.53%; p=0.031), but SRLE did not. From 60–90 minutes of Heat Challenge in the Hi‐SCI group, SRUE and SRLE failed to increase, which was associated with progressive increases in Tcore to BL values at 60 minutes (36.74±0.45°C) and above BL values at 90 minutes (37.01±0.45°C vs. 36.8±0.45°C; p=0.01). In the AB group, both SRUE and SRLE incrementally and significantly increased at each 30 minute interval of Heat Challenge, and Tcore remained lower than the BL value at 90 minutes (37.17±0.23 vs. 37.35±0.27°C; p=0.003). Conclusions In the Hi‐SCI group, we speculate that during the first 30 minutes of Heat Challenge, residual sympathetic sudomotor control allowed for increased SRUE, which resulted in a dip in Tcore that was similar to the dip observed in the AB group. However, because of limited sympathetic integrity in the upper and lower extremities, persons with Hi‐SCI were unable to mount a meaningful increase in SRUE from 60–90 minutes or in SRLE from BL to 90 minutes. The insufficient thermal homeostatic response to more prolonged Heat Challenge in the Hi‐SCI group resulted in a Tcore rise above BL values. Thus, prolonged exposure (>60 minutes) to elevated ambient temperatures poses a risk to persons with higher levels of SCI. Support or Funding Information: Department of Veterans Affairs Rehabilitation Research and Development Service (I21RX001734). This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .