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Can the study of individuals with autonomically complete spinal cord injuries help clarify the role of sympathetic nerves in cerebrovascular reactivity?
Author(s) -
Inskip Jessica,
Ravensbergen Rianne H.J.C.,
O'Connor Shawn M.,
Claydon Victoria E.
Publication year - 2013
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.27.1_supplement.925.8
Subject(s) - medicine , supine position , hyperventilation , blood pressure , cardiology , hypocapnia , anesthesia , middle cerebral artery , respiratory system , hypercapnia , ischemia
Cerebral blood vessels are richly innervated by sympathetic nerves; however, their role in the control of the cerebral vasculature remains controversial. Individuals with spinal cord injury (SCI) provide a unique opportunity to study cerebrovascular control in the absence of sympathetic control. Here we studied cerebrovascular reactivity to CO 2 in individuals with cardiovascular autonomically complete and incomplete SCI, and neurologically intact controls. Cardiovascular autonomic completeness was assessed on the basis of supine plasma noradrenaline levels, blood pressure variability and lesion level. Supine beat‐to‐beat blood pressure and middle cerebral artery velocity (MCAv) were continuously recorded, as were breath‐by‐breath partial pressures of end‐tidal O 2 and CO 2 (P ET CO 2 ), during manipulation of P ET CO 2 . Low levels of P ET CO 2 were obtained by voluntary hyperventilation, and high levels by hypoventilation with increased inspired CO 2 , during normoxia (controlled on a breath‐by‐breath basis using dynamic end‐tidal forcing). MCAv reactivity was significantly different between groups (control 11.2±2.4; autonomically incomplete SCI 5.8±0.6; autonomically complete SCI 6.2±0.7 %/mmHg, p=0.025, mean±sem). These preliminary data suggest that there is impaired cerebrovascular reactivity in individuals with SCI that is independent of injury to cardiovascular autonomic pathways. This research is supported by the Heart and Stroke Foundation of B.C. and Yukon (V.E.C).