Compromised cerebrovascular function likely contributes to elevated neurological risk in spinal cord injury (SCI). Passive heating offers many cardiovascular and neurological health benefits; therefore, we aimed to determine the effects of an acute bout of heating on cerebrovascular function in chronic SCI.
Persons with cervical SCI (n = 15) and uninjured controls (CON; n = 15) completed 60 min of lower limb hot water immersion (40 °C). Assessments of middle cerebral (MCA) and posterior cerebral artery (PCA) velocities, pulsatilities, and neurovascular coupling (NVC) were performed using transcranial Doppler ultrasound. Duplex ultrasonography was used to index cerebral blood flow via the internal carotid artery (ICA), and carotid-femoral pulse-wave velocity (PWV) was measured using tonometry. The NVC response was quantified as the peak hyperemic value during 30-s cycles of visual stimulation.
Mean arterial pressure changed differentially with heating [mean (standard deviation); SCI: +6(14) mmHg, CON: −8(12) mmHg; P = 0.01]. There were no differences in any intracranial artery measures (all P > 0.05), except for small (~10%) increases in MCA conductance in CON after heating vs. SCI (interaction P = 0.006). Resting ICA flow was greater in SCI vs. CON (P = 0.03) but did not change with heating in either group (interaction P = 0.34). There were also no between-group differences in the NVC response (ΔPCA conductance) pre- [SCI: 29(19)% vs. CON: 30(9)%] or post-heating [SCI 30(9)% vs. 25(9)%; interaction P = 0.22].
Mild acute heating does not impair or improve cerebrovascular function in SCI or CON. Thus, further study of the effects of chronic heating interventions are warranted.
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The individual datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.
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We thank the participants for volunteering their time for this study.
This study was supported in part by a Seed Grant from ICORD supported by the Blusson Integrated Cures Partnership (PNA), Canada Research Chairs program (PNA), and University of Calgary Start-up funds (AAP).
We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during the course of this research.
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Coombs, G.B., Vucina, D., Caldwell, H.G. et al. Cerebrovascular function is preserved during mild hyperthermia in cervical spinal cord injury. Spinal Cord 57, 979–984 (2019). https://doi.org/10.1038/s41393-019-0321-1