Hemodynamic responses to head-up tilt after spinal cord injury support a role for the mid-thoracic spinal cord in cardiovascular regulation.

Abstract

Data showing a role for the mid-thoracic spinal cord (SC) in the control of hemodynamic changes is scarce despite existing evidence for its involvement in autonomic regulation. On the basis of the open label prospective series comparing three groups. To determine whether the mid-thoracic SC has a role in hemodynamic regulation during head-up tilt (HUT). Spinal Research Laboratory, Loewenstein Rehabilitation Hospital. A total of 13 healthy control subjects, 10 patients with T(4)-T(6) paraplegia and 11 with C(4)-C(7) tetraplegia were examined during supine rest and during HUT. Heart rate (HR), blood pressure (BP), HR spectral components (lower frequency fluctuation (LF), higher frequency fluctuations (HF) and LF/HF) and cerebral blood flow velocity (CBFV) were continuously measured or calculated. BP response to HUT differed among these groups (P<0.02). During HUT, BP decreased markedly in the tetraplegia group (from a mean value of 81.65 to 67.69  mm Hg), and increased in the control groups (from 92.89 to 95.44 mm Hg) and in the T(4)-T(6) paraplegia group (from 96.24 to 97.86 mm Hg). Significant correlation was found in the control and tetraplegia groups between increases in HR LF/HF and HR at HUT (r>0.7; P<0.01). No such correlation was found in the paraplegia group. HUT effect on HR and CBFV was significant in all groups (P<0.001), but group differences were statistically non-significant. Findings were generally compatible with those of comparable previously published studies, but they also support a role for the mid-thoracic SC in hemodynamic regulation, which should be considered in clinical setting and in research.