Abstract
Background/PurposeThis study compares heart rate variability (HRV) and systolic blood pressure (SBP) changes of spinal cord injury (SCI) patients during urodynamic study (UDS) with able-bodied controls.MethodsTwenty four complete suprasacral SCI patients (12 tetraplegia and 12 paraplegia) and 12 age-matched able-bodied volunteers received BP and HRV evaluation throughout urodynamic examination. We chose seven time points during the examinations: resting, Foley catheter insertion, start of infusion, and infused volume reaching 1/4, 2/4, 3/4 and 4/4 of maximal capacity. At each time point, electrocardiogram with a duration of 5 min was used for power spectral density analysis of HRV.ResultsOnly control subjects displayed significant elevation of SBP during Foley catheter insertion compared to resting values. Both control and tetraplegic groups experienced significant elevation of SBP at maximal bladder capacity compared to resting values. Tetraplegic values were also significantly greater than the other two groups. Control subjects displayed significant elevation of low frequency/high frequency (LF/HF) ratios during Foley catheter insertion and when approaching maximum bladder capacity. These findings were not seen in the paraplegic and tetraplegic groups. However, subgroup analysis of tetraplegic subjects with SBP elevation >50 mmHg demonstrated a similar LF/HF response to the able-bodied controls.ConclusionTetraplegic patients experienced BP elevation but did not experience significant changes in HRV during bladder distension. This finding may imply that different neurological pathways contribute to AD reaction and HRV changes during bladder distension. However, profound AD during UDS in tetraplegic patients was associated with corresponding changes in HRV. Whether HRV monitoring would be beneficial in SCI patients presenting with significant AD, it needs further studies to elucidate.
Highlights
Autonomic dysfunction frequently accompanies spinal cord injuries (SCI)
Tetraplegic patients experienced Blood pressure (BP) elevation but did not experience significant changes in heart rate variability (HRV) during bladder distension. This finding may imply that different neurological pathways contribute to autonomic dysreflexia (AD) reaction and HRV changes during bladder distension
Profound AD during urodynamic study (UDS) in tetraplegic patients was associated with corresponding changes in HRV
Summary
Autonomic dysfunction frequently accompanies spinal cord injuries (SCI). Strong correlations between the level of injury and the severity of autonomic dysfunction have been reported[1]. Almost all SCI patients suffer from neurogenic lower urinary tract dysfunction (NLUTD) and urodynamic study (UDS) is essential for these patients in order to assess the bladder function during their initial rehabilitation period and the following lifelong surveillance[3]. European Association of Urology guidelines on NLUTD demonstrate grade A recommendation for the necessity of UDS to document the dysfunction of lower urinary tract[4]. Several studies, including our previous report, have documented the presence of AD with noticeable SBP increase during UDS in SCI patients [5,6,7]
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