A spinal cord injury (SCI) is most often characterized by a loss of sensation or the inability to control limb movements, either in the lower extremities (paraplegia) or inferior to the neck (tetra/quadriplegia). There are currently roughly 450,000 SCI patients in the U.S. alone, with about 10,000 new injuries occurring each year. Cardiovascular disorders as a group are one of the most common causes of death in SCI patients.
Prolonged bed rest and inactivity following an accident or injury are some of the reasons for a decline in cardiovascular health, also known as cardiovascular deconditioning. Researchers tested the cardiac systems of SCI volunteers by simulating the electrical impulses that would be generated by an able-bodied skeletal muscular system. Differentiating between the SCI patients’ system and that of a standing able-bodied person, they found marked decreases in heart rate, cardiac output, stroke volume and peripheral resistance in the SCI patient, which explains why many suffer from orthostatic hypotension.
The autonomic nervous system is commonly impaired, as well as the sympathetic nervous system. SCI patients can suffer from bouts of autonomic dysreflexia (also called autonomic hyperreflexia) (AD), which is a condition characterized by a sharp increase blood pressure or a slowing of the heart rate, along with many other seemingly unrelated physiological symptoms. AD is generally caused by pain, disease or injury below the SCI site, where non-functioning nerve cells are not transmitting information to the patient about an acute health issue such as a bladder infection or infected pressure ulcer.
People living with an immobilizing SCI have an increased risk of developing circulatory issues, due to the inherent lack of voluntary limb movement which would normally assist in venous return. Muscle movement helps the valves pump blood, so edema can easily occur when those muscles no longer engage. An SCI can result in permanent swelling of the extremities. Blood clots in leg veins and pulmonary arteries are frequent, life-threatening concerns for SCI patients, most often in the acute phase, and must be monitored and (usually) medicated.
Sources:
Claydon, V. E., J. D. Steeves, and A. Krassioukov. “Spinal Cord – Orthostatic Hypotension following Spinal Cord Injury: Understanding Clinical Pathophysiology.” Nature Publishing Group: Science Journals, Jobs, and Information. Nature Publishing Group, 22 Nov. 2005. Web. 07 Oct. 2011. <http://www.nature.com/sc/journal/v44/n6/full/3101855a.html>.
Staff, Mayo Clinic. “Spinal Cord Injury – MayoClinic.com.” Mayo Clinic. 23 Oct. 2009. Web. 07 Oct. 2011. <http://www.mayoclinic.com/health/spinal-cord-injury/DS00460>.
Understanding Spinal Cord Injury. Shepherd Center, Christopher & Dana Reeve Foundation, et al., 2011. Web. 09 Oct. 2011. <http://www.spinalinjury101.org/>.
