American journal of hypertension
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Comparative Study
Altered Mayer wave and baroreflex profiles in high spinal cord injury.
Spinal sympathetic neurons are distributed in cord segments from Th1 to L3. High spinal cord injury demonstrates severe orthostatic hypotension, but not lower cord injury. It remains to be clarified as to where is the critical spinal level disturbing neural cardiovascular regulations in response to orthostatic stress. ⋯ The low-level injury group and the control group demonstrated essentially similar autonomic nervous responses to postural shift, ie, a significant increase in Mayer wave power and an insignificant decrease in baroreflex sensitivity. On the contrary, the high-level injury group showed opposite responses, ie, an insignificant decrease in Mayer wave power and a significant increase in baroreflex sensitivity in response to postural shift. We conclude that spinal cord injury at Th3 or above eliminates normal neural cardiovascular responses to mild orthostatic stress in humans.