Cerebrovascular function is preserved during mild hyperthermia in cervical spinal cord injury

Abstract

Study design Experimental study. Objectives 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. Methods 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. Results 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]. Conclusions 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.

Evidence for temperature‐mediated regional increases in cerebral blood flow during exercise

“…increases in regional CBF) may be achieved with moderate-level passive heat stress; as such, these findings may provide support for passive heat stress as a novel exercise alternative for clinical populations with impaired cerebrovascular health and/or inability to participate in aerobic exercise (e.g. spinal cord injury, cerebral palsy, multiple sclerosis) (Phillips et al 2017;Metzger et al 2018;Coombs et al 2019); however, future research on exercise in the heat is required for these clinical groups. Favourable blood flow patterns (e.g.…”

“…; Coombs et al . ); however, future research on exercise in the heat is required for these clinical groups. Favourable blood flow patterns (e.g.…”

The effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta‐analysis

“…Likewise, the beneficial effects of Waon therapy include reductions in blood pressure and cardiac‐related hospitalization for patients with chronic heart failure (Conceição et al., 2018; Ye et al., 2020). Narrative reviews, commentaries (Cheng & MacDonald, 2019; Coombs & Tremblay, 2019; Tipton, 2018) and primary investigations have reported broad beneficial effects among a range of health conditions, on leg vascular function (Engelland et al., 2019, 2020; Romero et al., 2017), skeletal muscle capillarization (Hesketh et al., 2019), glucose metabolism (Kimball et al., 2018; Leicht et al., 2019), insulin sensitivity (Hesketh et al., 2019), blood circulating factors (Brunt et al., 2018; Kojima et al., 2018) and cerebral function (Bailey et al., 2016; Coombs et al., 2019; Lee et al., 2014; Low et al., 2009). With ageing populations and the rising prevalence of CVD, there has been increased focus on the benefits of heat therapy for vascular function.…”