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By Jennifer Pisarek
This is a summary of a paper published by ICORD researchers from Vancouver, Canada in The Spine Journal.
Original article: Alan et al. (2010). Recurrent autonomic dysreflexia exacerbates vascular dysfunction after spinal cord injury. The Spine Journal, 10 (12), 1108. http://www.ncbi.nlm.nih.gov/pubmed/21094471
Autonomic Dysreflexia (AD) is a potentially life threatening complication of spinal cord injury (SCI). Individuals with SCI at the mid-thoracic level or above are more susceptible to AD. This process occurs when the body receives a painful or uncomfortable stimulus below the level of injury. In response to the stimulus, an individual’s blood pressure rises to alarming levels while their heart rate drops. If left untreated, AD may lead to stroke or possibly death. Symptoms of AD include a pounding headache, perspiration, facial flush, and nasal congestion.
A study conducted by ICORD researchers examined how blood pressure control is interrupted after SCI and how blood vessels respond when chronic AD is present. Researchers investigated the sensitivity of blood vessels post-injury to a stimulus that caused the vessels to constrict. They also examined the extent to which the blood vessels constricted when presented with the signal. By examining these two variables, researchers were able to see how blood vessels adapt after SCI in response to persistent AD.
What was the most important finding?
The results demonstrated that the blood vessels actually became more sensitive to the signal that caused them to constrict but that when presented with that signal they constricted less. This shows that the blood vessels became accustomed to the signal over time indicating that persistent AD has enduring effects on the function of these blood vessels. These results raise some important questions that need to be addressed. Namely, what mechanism is causing the blood vessels to become accustomed to the stimulus?
What are some things we need to consider?
We need to take in consideration that this study was investigated in an animal model and different results may emerge when it is translated to the human condition. Additionally, this study examined an extreme model of AD where a major attack occurred on a daily basis.
Further research needs to be conducted to answer the questions proposed by this study. For example, further investigation is needed to explain why the blood vessels that were previously exposed to AD evoked a smaller response in comparison to those that were not. What causes the blood vessels to become more sensitive to the constrictive signal but still constrict less? In theory, if the blood vessel is more responsive to the stimulus then the response should be greater! The mechanism that is modulating the signal such that it induces a weaker response clearly needs to be identified.
What does this mean for people with SCI?
This study’s results show that blood vessels in individuals with SCI can become accustomed over time to a contractile stimulus; this demonstrates that there is an unknown long-term process that produces changes beyond the short-term effects of AD. Further research is required to gain a better understanding of the mechanisms underlying this process, out of which a possible treatment could emerge. However, this potential treatment may not become a reality in the near future.
For the time being it is imperative that individuals with SCI educate themselves with regard to the signs and symptoms of AD. As well as, remaining vigilant of behaviours that can help to prevent or alleviate AD, such as proper self-care.
For further resources addressing AD refer to the BC Spinal Cord Injury website – http://sci-bc.ca/.
