Cardiovascular autonomic control after spinal cord injury: Comprehensive investigations into classification and care

Over 86,000 Canadians live with the consequences of a spinal cord injury (SCI). Injury to spinal autonomic pathways can lead to profound cardiovascular autonomic dysfunction. Key areas of concern identified by individuals living with SCI relate to continence and cardiovascular dysfunction. Conditions that result from autonomic dysfunction, such as autonomic dysreflexia (sudden extreme hypertension) are of particular concern. This thesis examined the cardiovascular autonomic consequences of SCI and their relationship to bowel care, the most potent stimulus for dysreflexia, and a key factor that negatively impacts quality of life after SCI. To assess cardiovascular autonomic control, first a quantitative marker of autonomic dysfunction following SCI had to be identified. In Aim 1 (Chapter 3), cardiovascular dysfunction during, and beyond, the first year of injury (n=63) was assessed using a novel quantitative non-invasive marker of cardiovascular autonomic control. From here, a randomized double-blind placebo-controlled crossover clinical trial to determine the effect of topical afferent blockade (lidocaine) on dysreflexia severity during bowel care was conducted (n=13). Aim 2 (Chapter 4) provides evidence that, contrary to current clinical guidelines, topical lidocaine prolongs bowel care, worsens dysreflexia, and increases cardiovascular symptoms. Despite bowel care concerns, past research shows that individuals do not change bowel care practices, highlighting knowledge translation gaps concerning evidence-based bowel management strategies. To address this, in Aim 3 (Chapter 5), semi-structured interviews (n=13) were used to examine the barriers and facilitators to changing bowel care. The largest influences on changing bowel care and potentially relevant intervention options were identified. Finally, during dysreflexia profound sympathetic stimulation may increase risk for cardiac arrhythmia. Aim 4 (Chapter 6) evaluated susceptibility to arrhythmia in a rodent-model of SCI, the impact of the sympathomimetic drug dobutamine on arrhythmia risk, and the potential mitigating effect of exercise training. SCI increased susceptibility to cardiac arrhythmia, with dobutamine further increasing susceptibility in high-level SCI. Exercise training ameliorated markers of arrhythmia risk during dobutamine. The research conducted in this thesis uses a translational and patient-orientated approach to bridge the gap between physiological understanding and meaningful improvement in the clinical setting for individuals living with cardiovascular and continence implications of SCI.