Why Some SCI Patients Feel Dizzy When Standing? Orthostatic Hypotension after Spinal Cord Injury

Author:
Helena López (Clinical Manager), Carmen Arreola (Marketing Manager)

What is Orthostatic hypotension?

Orthostatic hypotension (OH) is a cardiovascular disorder characterised by a significant drop in blood pressure after a change of position, from a supine to an upright position (i.e. sitting or standing). It is defined as a decrease in systolic blood pressure (SBP) of at least 20 mmHg or diastolic blood pressure (DBP) of at least 10 mmHg within three minutes of changing the body position from lying down to standing or sitting, or even during a head-up tilt^1,2. This condition can lead to dizziness, lightheadedness, fainting, and an increased risk of falls, particularly in older adults and individuals with underlying neurological or cardiovascular disorders^1,2.

Symptoms

Most patients with OH are either asymptomatic or experience only mild, nonspecific symptoms, resulting in a significant number of undiagnosed cases^1,4. Symptoms tend to be worse in the morning, especially right after waking up, they can get worse with things like heat, not drinking enough water, alcohol intake or standing still for too long, because these can cause blood to stay in the legs and reduce blood flow to the brain¹. Some of the most common symptoms are:

Diagnosis

The diagnosis of OH involves measuring blood pressure in both supine and standing positions. A structured evaluation includes:

• Blood pressure measurement: After five minutes of rest in a supine position, followed by measurements at one and three minutes after standing⁵.
• Head-up tilt test: Used in specialised settings to evaluate autonomic function^1,4,5.
• 24-hour ambulatory blood pressure monitoring: Helps detect fluctuations in blood pressure throughout the day, including nocturnal hypertension^1,5.
• Autonomic function tests: The Valsalva maneuver and heart rate variability tests to determine if the condition is neurogenic⁵.

Causes

Orthostatic hypotension is classified into 2 different categories that are differentiated by its cause: neurogenic and non-neurogenic^1,4. In both cases, the OH is caused by an autonomic nervous system* failure:

• the neurogenic includes spinal cord injuries, traumatic brain injuries, neurogenetive disorders or diabetes,
• and the non-neurogenic, which are caused by external factors, mainly by medication use, dehydration or blood loss^1,4,5.

*The autonomic nervous system (ANS) is responsible for controlling involuntary physiologic processes, including blood pressure, heart rate, respiration, digestion, and sweating. This system is divided into sympathetic, which emerges in the thoracic area (T1) and terminates in the lumbar (around L2-3) area of the spinal cord; and parasympathetic originates in the craniosacral axes (which means it begins in the cranial nerves and in the sacral (S2-S4) area of the spinal cord).

OH in SCI

Spinal cord injury (SCI) can significantly disrupt the ANS, resulting in a range of issues, including:

• Cardiovascular dysfunction
• Temperature regulation problems
• Bowel and bladder control issues
• Potential development of autonomic dysreflexia

The neurological level of injury and severity is directly related to the severity of cardiovascular dysfunction in individuals with chronic SCI.

Moreover, reduced muscle function in the lower limbs limits the muscle pump effect, decreasing normal blood return to the heart. Other contributing factors to OH include: low blood volume, low blood sodium levels, and deconditioning of the heart and blood vessels due to prolonged bed rest⁶.

Prevalence of OH in SCI

Research has revealed a high prevalence of OH in SCI patients, with one study finding that 14 acute SCI patients experienced OH during mobilization therapy⁷. Additionally, one study demonstrated that higher complete injuries are more likely to experience OH than lower and incomplete injuries during the first month of rehabilitation⁸.

Treatments

There are different treatments whose main goal is to reduce the symptoms, such as falls^4,5. These treatments can be non-pharmacological as patient education, abdominal compression, bed elevation and more, and/or pharmaceutical, like midodrine or fludrocortisone^1,3,5,9,10.

However, not all treatments have been tested to show efficacy in managing OH symptoms in persons with SCI. The ones that have more evidence are the following:

Non-Pharmacological Treatments	Pharmacological Treatments
Functional Electrical Stimulation (FES): FES increases venous return by muscle-induced contractions. This helps reduce the blood pressure changes during postural changes11.	Midodrine: By activating some receptors, it increases the vascular tone and blood pressure, which helps in the management of OH symptoms in people with SCI13.
Exercise: It may improve the cardiovascular system and increase blood pressure, which might improve OH tolerance12

Role of Rehabilitation in OH

Rehabilitation plays a critical role in individuals with neurological conditions such as spinal cord injury^9,14. Physical therapy, strength training, and endurance exercises can help improve autonomic function and cardiovascular regulation, which can lead to reducing OH symptoms¹⁴. However, OH itself can be a challenge in rehabilitation programs, as patients may experience symptomatic drops in blood pressure during therapy sessions, which may lead to discouraging patients with SCI in their rehabilitation⁶.

Robotic exoskeletons assist in rehabilitation by promoting functional ambulation and maintaining an upright posture¹⁵, but they are not universally suitable for all individuals with OH. In some cases, OH may serve as exclusion criteria for exoskeleton use, as the condition could increase the risk of dizziness and falls during training. Additionally, exoskeleton-assisted gait training may trigger episodes of OH in susceptible individuals, necessitating careful monitoring and individualised adjustments to rehabilitation plans.

References

1. Gibbons, C. H., & Freeman, R. (2015). Orthostatic hypotension: Epidemiology, prognosis, and treatment. Journal of the American College of Cardiology, 66(7), 848–860. https://doi.org/10.1016/j.jacc.2015.06.1084
2. SCIRE Project. (n.d.). Orthostatic Hypotension – Introduction. Retrieved from https://scireproject.com/evidence/orthostatic-hypotension/introduction/
3. Freeman, R., Wieling, W., Axelrod, F.B. et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin Auton Res 21, 69–72 (2011). https://doi.org/10.1007/s10286-011-0119-5  
4. Kim, M. J., & Farrell, J. (2022). Orthostatic Hypotension: A Practical Approach. American family physician, 105(1), 39–49.
5. Gibbons, C.H., Schmidt, P., Biaggioni, I. et al. The recommendations of a consensus panel for the screening, diagnosis, and treatment of neurogenic orthostatic hypotension and associated supine hypertension. J Neurol 264, 1567–1582 (2017). https://doi.org/10.1007/s00415-016-8375-x 
6. SCIRE Project. (n.d.). Orthostatic Hypotension. Retrieved from https://scireproject.com/evidence/orthostatic-hypotension/
7. Illman, A., Stiller, K., & Williams, M. (2000). The prevalence of orthostatic hypotension during physiotherapy treatment in patients with an acute spinal cord injury. Spinal cord, 38(12), 741–747. https://doi.org/10.1038/sj.sc.3101089 
8. Sidorov, E., Townson, A., Dvorak, M. et al. Orthostatic hypotension in the first month following acute spinal cord injury. Spinal Cord 46, 65–69 (2008). https://doi.org/10.1038/sj.sc.3102064 
9. Sarafis, Z.K., Monga, A.K., Phillips, A.A. and Krassioukov, A.V. (2018), Is Technology for Orthostatic Hypotension Ready for Primetime?. PM&R, 10: S249-S263. https://doi.org/10.1016/j.pmrj.2018.04.011
10. Juan J. Figueroa, MD, Jeffrey R. Basford, MD, PhD & Phillip A. Low, MD. Preventing and treating orthostatic hypotension: As easy as A, B, C. Cleveland Clinic Journal of Medicine May 2010, 77 (5) 298-306; DOI: https://doi.org/10.3949/ccjm.77a.09118 
11. SCIRE Project. (n.d.). Effect of Functional Electrical Stimulation (FES) on OH. Retrieved from https://scireproject.com/evidence/orthostatic-hypotension/non-pharmacological-management-of-oh/effect-of-functional-electrical-stimulation-fes-on-oh/
12. Otsuka, Y., Shima, N., Moritani, T., Okuda, K., & Yabe, K. (2008). Orthostatic influence on heart rate and blood pressure variability in trained persons with tetraplegia. European journal of applied physiology, 104(1), 75–78. https://doi.org/10.1007/s00421-008-0783-x
13. SCIRE Project. (n.d.). Pharmacological Management of OH in SCI. Retrieved from https://scireproject.com/evidence/orthostatic-hypotension/pharmacological-management-of-oh-in-sci/
14. Nas, K., Yazmalar, L., Şah, V., Aydın, A., & Öneş, K. (2015). Rehabilitation of spinal cord injuries. World journal of orthopedics, 6(1), 8–16. https://doi.org/10.5312/wjo.v6.i1.8 
15. Karelis, A. D., Carvalho, L. P., Castillo, M. J., Gagnon, D. H., & Aubertin-Leheudre, M. (2017). Effect on body composition and bone mineral density of walking with a robotic exoskeleton in adults with chronic spinal cord injury. Journal of rehabilitation medicine, 49(1), 84–87. https://doi.org/10.2340/16501977-2173