In people with spinal cord injuries, the paralysis affects the control of the vegetative nervous system. Orthostatic1 dysregulation can occur in the case of paralysis at a high level, in particular.
Blood pressure is self-regulating in healthy people. There is disruption to this regulation, which is controlled by the vegetative nervous system, in people with spinal cord injuries. When changing from a lying to a sitting position, a sudden sharp drop in blood pressure can occur, orthostatic hypotonia.
Symptoms of this drop in blood pressure are dizziness, weakness, flickering vision or light-headedness. In extreme cases, the person affected loses consciousness.
What causes this reaction?
In healthy people, blood pressure is regulated by the correct control of the blood vessels and the cardiac function by the vegetative nervous system. In people with spinal cord injuries (with injuries above T6), the sympathetic nervous system loses the ability to control the blood vessels correctly. In addition, the muscular pump effect is lost in people with spinal cord injuries. This normally helps to regulate blood pressure by applying pressure to the blood vessels. If the muscles now no longer contract and the vegetative nervous system is unable to respond, the blood settles in the blood vessels of the legs, resulting in a rapid drop in blood pressure. People with tetraplegia, in particular, often pass lots of urine at night in order to counteract this disrupted circulatory function. The absence of fluid means that they frequently experience blood pressure difficulties in the mornings.
Many drugs increase orthostatic hypotonia, in particular diuretics2 such as Lasix®, neuroleptics such as Haldol® or Quetiapin®, blood pressure drugs and medication to treat prostate enlargement.
What can be done about it?
A preventative effect can be achieved by wearing compression stockings. The stockings exert pressure on the blood vessels, performing some of the role of the muscular pump action in the legs. Wearing a stomach belt may be helpful in some cases, although there is no scientific proof that it helps to prevent a drop in blood pressure. However, a stomach belt can help to raise seating stability or be used as respiratory support. Functional electrical stimulation of the leg muscles, active or passive movements of the legs or sport are very effective.
As blood pressure checks in people with spinal paralysis often only works slowly, people affected should change position slowly. If orthostatic hypotonia occurs, it often helps to raise the legs briefly immediately after transferring into the wheelchair.
It may be helpful to have the top of the bed slightly raised during the night to counteract excessive micturition overnight. Drinking a half litre of water or some beef tea before moving can help to prevent dizziness. Some people with tetraplegia also experience an improvement after raising their salt intake.
Drugs which stimulate the sympathetic nervous system can also be used for treatment or prevention. Gutron® (midodrine) is the drug to choose; Effortil® (etilefrine) which is frequently administered is generally not very effective. The water balance which is disrupted in tetraplegics in particular can be corrected by administering Florinef® (fludrocortisone), which increases water retention.
Do I have to wear compression stockings for the rest of my life?
The length of time you have to wear compression stockings varies from one person to the next. Most people who are affected by spinal cord injuries wear them during the first 6 months or so of initial rehabilitation.The body often gets used to the new situation and, over time, the compression stockings can generally be discarded. Other people affected are repeatedly affected by drops in blood pressure and, therefore, wear compression stockings for a long time.
Will the orthostatic hypotonia improve over time?
Yes, orthostatic hypotonia improves within months or years in the case of many people with spinal cord injuries. Firstly, the blood vessels become constricted in the paralysed area, which means that less blood flows in the veins; secondly, the vegetative nervous system also becomes used to the paralysis over time. Not least of all, you will learn how to adapt your own behaviour.
Is orthostatic hypotonia dangerous?
Brief drops in blood pressure lasting a few minutes do not have any lasting impact on the health of organs.
1 with the body posture upright
2 drugs for expelling excessive fluid in the body