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

Abstract

Background: 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. Study design: On the basis of the open label prospective series comparing three groups. Objective: To determine whether the mid-thoracic SC has a role in hemodynamic regulation during head-up tilt (HUT). Setting: Spinal Research Laboratory, Loewenstein Rehabilitation Hospital. Methods: 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. Results: BP response to HUT differed among these groups (Po0.02). 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 (r40.7; Po0.01). No such correlation was found in the paraplegia group. HUT effect on HR and CBFV was significant in all groups (Po0.001), but group differences were statistically non-significant. Conclusion: 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.

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

“…The angle of the table can be altered in situations when 60 ° may be difficult to sustain, for example when evaluating orthostatic intolerance in spinal cord injured populations. In such cases, tilting to 30-35 ° may be more appropriate and tolerable [54][55][56] . If desired, the protocol may be shortened in specific populations by stopping after completion of LBNP at -20 mmHg -individuals who reach the end of this phase essentially have a normal OT ( Table 1).…”

Insulin resistance in tetraplegia but not in mid-thoracic paraplegia: is the mid-thoracic spinal cord involved in glucose regulation?

“…The additional tests, detailed elsewhere, [11][12][13][14] include the HUT examinations performed before and after the meal. The HUT could have confounded the effect of the liquid meal, but it was not found to influence glucose or insulin levels, before or after the meal, irrespective of group, consistent with former observations in healthy men.…”

“…In the present experiments, which were part of a larger study, [11][12][13][14] we compared glucose and insulin responses to a standard meal and head-up tilt (HUT) in a group of patients with mid-thoracic, below T 4 , SCI, with responses of patients with cervical SCI and of healthy subjects. We also compared the insulin response to meal with post-prandial changes in low frequency (LF)/high frequency (HF) ratio, the LF/HF heart rate (HR) variations power values.…”

Cardiovascular control during head-up tilt test in spinal cord injury patients

“…We read with interest the paper by Bluvshtein et al 1 on hemodynamic responses to head-up tilt (HUT) after spinal cord injury. The idea of selecting specific categories of patients (tetraplegics and T4-T6 paraplegics) is interesting, as we know that cardiovascular changes directly depend on the level of lesion.…”