Cardiovagal baroreflex gain relates to sensory loss after spinal cord injury

Auton Neurosci, 2020 · DOI: 10.1016/j.autneu.2020.102667 · Published: July 1, 2020

Spinal Cord Injury Cardiovascular Science Neurology

Simple Explanation

Spinal cord injury (SCI) can damage the autonomic nervous system, particularly affecting sympathetic control of blood vessels and the heart. This can lead to low blood pressure, especially with higher-level injuries. The study investigated whether the baroreflex gain (the body's ability to regulate blood pressure through heart rate) is different in individuals with SCI compared to able-bodied individuals, and if it relates to the level of injury. The researchers used the neck chamber technique to assess baroreflex gain by applying pressure changes to the neck and measuring the resulting changes in heart rate.

Study Duration

4 to 24 months since injury

Participants

29 SCI (neurological level C1-T10, sensory zone C4–S4/5) and 14 able-bodied

Evidence Level

Not specified

Key Findings

1
Average baroreflex gain tended to be higher in able-bodied individuals compared to those with SCI, particularly at lower input stimuli.
2
In individuals with SCI, baroreflex gain was not related to the neurological level of injury but was related to the sensory zone of partial preservation and resting RR-interval.
3
Individuals with higher sensory zone of partial preservation (less sensory loss) had lower baroreflex gain compared to both able-bodied individuals and those with lower sensory zone of partial preservation.

Research Summary

This study investigated baroreflex gain in individuals with SCI compared to able-bodied individuals, considering the neurological level and sensory zone of partial preservation. The findings indicated that able-bodied individuals tended to have higher baroreflex gain than those with SCI, and sensory zone of partial preservation was more predictive of baroreflex gain than neurological level of injury. The researchers suggest that the lower baroreflex gain in individuals with higher sensory level injuries might be related to reduced cardiac sympathetic innervation and vagal-sympathetic interactions.

Practical Implications

Clinical Assessment

Sensory zone of partial preservation may be a more relevant measure than neurological level when assessing autonomic function in SCI.

Therapeutic Strategies

Understanding the relationship between sensory loss and baroreflex function may inform targeted interventions to improve cardiovascular control in SCI.

Future Research

Further investigation into vagal-sympathetic interactions is warranted to better understand baroreflex regulation in SCI.

Study Limitations

1
The study could not assess beat-to-beat blood pressure regulation in individuals with spinal cord injury.
2
The brief carotid baroreceptor distention during neck chamber application doesn't provide enough data to assess feedforward effects of cardiac output changes on blood pressure.
3
Assessment of beat-to-beat blood pressure regulation would require measures of vascular sympathetic outflow, given that individuals with low level sensory injuries might have maintained sympathetic outflow to the vasculature.

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