Cardiovascular effects of transcutaneous spinal stimulation in persons living with and without spinal cord injury

Case-control series.

To investigate the cardiovascular effects of transcutaneous spinal stimulation (TSS) during orthostatic challenge in persons with and without spinal cord injury (SCI).

Laboratory.

Eleven persons with cervical SCI and ten persons without SCI participated in this study. Baseline systolic blood pressure (SBP) and heart rate (HR) were measured during an orthostatic challenge (10 min horizontal, 10 min upright). This was repeated with TSS (cathode: T7/T8 or T11/T12) applied when upright, and subsequently for 2 min when horizontal. SBP and HR were compared across groups and experimental conditions with linear mixed models.

When upright without TSS, SBP increased in the non-SCI group but decreased in the SCI group (mean difference -19.8 mmHg [95% CI, -33.6 to -6.0]). When upright with TSS, SBP increased in the SCI group, similar to non-SCI group (T7/T8: -6.6 mmHg [-20.4 to 7.3], T11/T12: 2.5 mmHg [-11.3 to 16.3]; non-SCI - SCI). In participants with SCI and orthostatic hypotension (OH), TSS at T11/T12 limited the orthostatic drop by 25.8 mmHg [5.0 to 46.6]. When horizontal, TSS increased SBP in the SCI group (T7/T8: 24.7 mmHg [16.8 to 32.6], T11/T12: 27.2 mmHg [19.3 to 35.1]).

Spinal stimulation at T11/T12 improved OH in persons with SCI. However, it also increases SBP when applied in a horizontal position, a caution for its clinical use. Future studies in people with SCI should explore the potential mechanisms responsible for these TSS-induced SBP effects.