Helping Patients with Spinal Cord Injury: A Thermostat for Blood Pressure

Written by: Melinda Li '22
Edited by: Katiana Soenen '24

If you’ve ever felt dizzy or faint after standing up quickly, you’ve probably experienced a brief instance of orthostatic hypotension, commonly known as a “head rush”. Although the unpleasant effects of a head rush only last for a few seconds, orthostatic hypotension is a serious problem for spinal cord injury patients, many of whom are not able to maintain a stable blood pressure when switching positions (1). ​

Beyond short-term dizziness and fainting, orthostatic hypotension can lead to higher risk of stroke and cardiovascular disease, which are two of the chief causes of death for patients with spinal cord injury. 

But there might be an exciting solution on the horizon: a neuroprosthetic device that can simulate the body’s baroreflex, the ability to respond to and stabilize changes in blood pressure (2). On January 27th 2021, researchers at the University of Calgary and the Swiss Federal Institute of Technology published their study on this device in Nature, one of the world’s leading scientific journals (3). Just a few centimeters in length, the device emits electrical pulses which trigger neural responses that affect blood pressure. When it senses a drop in blood pressure, it sends a signal to sympathetic neurons to increase pressure accordingly. 

Aaron Phillips, one of the lead scientists on the research team, compares the device to a thermostat, except the “home” environment it regulates is the body itself (4). This is especially helpful in treating patients with spinal cord injuries, who often have a severance in connection between their reflexive neurons that sense blood pressure and their sympathetic nervous system that keeps blood pressure at a steady level. 

The efficacy of the device has been successfully tested in the lab on rat and monkey models. In 2019, the researchers were even able to implant the device in a patient with chronic spinal cord injury and severe orthostatic hypotension, whose conditions improved drastically and no longer needed to take blood pressure medications (3).

These preliminary results are extremely promising, and Phillips and his colleagues are planning subsequent clinical trials to further test the device’s safety and efficacy. If proven successful, the device could even have secondary effects for spinal cord injury patients, including pain alleviation and improvement in bladder function. Phillips’ team hopes to have the device available to patients within the next five years, although there are major regulatory and research requirements that will have to be met before that can happen (4).

References
1.  How do spinal cord injuries affect the body? [Internet]. University of Iowa Hospitals & Clinics. 2018 [cited 2021 Feb 14]. Available from: https://uihc.org/health-topics/how-do-spinal-cord-injuries-affect-bodyhttps://www.statnews.com/2021/01/27/spinal-cord-injury-orthostatic-hypotension/
2. Klabunde R. Arterial Baroreceptors [Internet]. [cited 2021 Feb 14]. Available from: https://www.cvphysiology.com/Blood%20Pressure/BP012
3.  Squair JW, Gautier M, Mahe L, Soriano JE, Rowald A, Bichat A, et al. Neuroprosthetic baroreflex controls haemodynamics after spinal cord injury. Nature. 2021 Feb;590(7845):308–14.
4.  Gaffney T. A thermostat for blood pressure could help patients with spinal cord injuries [Internet]. STAT. 2021 [cited 2021 Feb 14]. Available from: https://www.statnews.com/2021/01/27/spinal-cord-injury-orthostatic-hypotension/
[Image Citation] Freeman R. Neurogenic Orthostatic Hypotension. N Engl J Med. 2008 Feb 7;358(6):615–24.