Evaluation of Cardiovascular Autonomic Function during Inpatient Rehabilitation following Traumatic Spinal Cord Injury

Abstract

Assessment of the degree of impaired autonomic nervous system (ANS) function is not part of routine clinical practice during inpatient rehabilitation following traumatic spinal cord injury (SCI). The goal of this investigation was to determine the utility of the International Standards for Neurologic Classification of SCI (ISNCSCI) and the recently revised International Standards to document remaining Autonomic Function after SCI (ISAFSCI) in documenting cardiovascular ANS impairment during inpatient rehabilitation following traumatic SCI. Beat-to-beat recording of supine heart rate (HR) and blood pressure (BP) were collected at the bedside for estimation of total cardiovascular ISAFSCI score, cardio-vagal modulation (i.e., high frequency HR variability [HF_HRV]) and sympathetic vasomotor regulation (i.e., Mayer wave component of systolic BP [SBP_mayer]). A total of 41 participants completed baseline testing, which was conducted 11 ± 5 days from the admission ISNCSCI examination. There were no differences in supine HR or BP based on the ISNCSCI or ISAFSCI assessments. The HF_HRV was generally lower with more distal lesions (r² = 0.15; p = 0.01), and SBP_mayer was significantly lower in those with American Spinal Injury Association Impairment Scale (AIS) A compared with AIS B, C, D (Cohen's d = -1.4; p < 0.001). There were no significant differences in HF_HRV or SBP_mayer in patients with or without ISAFSCI evidence of cardiovascular ANS impairment. These preliminary data suggest that neither the ISNCSCI nor the ISAFSCI are sensitive to changes in ANS cardiovascular function following traumatic SCI. Bedside assessment of HR and BP variabilities may provide insight, but are not readily available in the clinical setting. Further research is required to evaluate methods that accurately assess the degree of ANS impairment following traumatic SCI.

Keywords: blood pressure; heart rate; paraplegia; tetraplegia; variability.

FIG. 1.

Supine heart rate (A), systolic blood pressure (BP; B) and diastolic BP (C) presented by the neurologic level of injury (NLI) as assessed by the International Standards for Neurologic Classification of Spinal Cord Injury examination as: cervical (C3-T1: gray circles), high thoracic (T2-T4: open squares) and low thoracic (T6-T12: black triangles). There were no significant differences in supine hemodynamics by the NLI. Dashed lines indicate the International Standards to document remaining Autonomic Function after Spinal Cord Injury definitions of impairment.

FIG. 2.

Supine heart rate (A), systolic blood pressure (BP; B), and diastolic BP (C) presented by the American Spinal Injury Association Impairment Scale (AIS) classification as assessed by the International Standards for Neurologic Classification of Spinal Cord Injury examination as: AIS A (gray circles), AIS B, C, D (open squares). There were no significant differences in supine hemodynamics by the AIS classification. Dashed lines indicate the International Standards to document remaining Autonomic Function after Spinal Cord Injury definitions of impairment.

FIG. 3.

Supine HF_HRV (A) presented by the neurologic level of injury as assessed by the International Standards for Neurologic Classification of Spinal Cord Injury (ISNCSCI) examination as: cervical (C3-T1: gray circles), high thoracic (T2-T4: open squares) and low thoracic (T6-T12: black triangles) and supine Mayer wave component of systolic blood pressure (SBP_mayer; B) presented by the American Spinal Injury Association Impairment Scale (AIS) classification as assessed by the ISNCSCI examination as: AIS A (gray circles), AIS B, C, D (open squares). HRHF was significantly reduced in the low thoracic group compared with the cervical (**p < 0.01) and high thoracic (*p < 0.05) groups. SBPmayer was significantly reduced in those with AIS A compared with those with AIS B, C, D lesions (**p < 0.01).