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POTS & Hypotension

Posted By Alan Hakim, June 9, 2013

POTS, Hypotension, Fatigue and Upset Bowel

The Autonomic Nervous System and Hypermobility Syndromes


The autonomic nervous system is a highly specialised network of nerves that regulate a number of important systems, automatically adjusting functions in the body and compensating for change.

Activity is driven and controlled from structures in the brain stem and spinal cord over which we have very limited control.  Highly intricate reflex reactions between organs and blood vessels of the body are constantly taking place without need for recourse to the brain.

The autonomic nervous system is made up of three parts:

  • the sympathetic
  • parasympathetic, and
  • enteric (bowel) nervous systems.

Essentially the sympathetic and parasympathetic systems work in opposition to each other, not in conflict, but in balancing the various functions they control.  For example, the sympathetic nervous system tends to speed up the heart, the parasympathetic system slowing it down. The sympathetic system will slow down bowel activity and the parasympathetic nervous system will speed it up.  When you are running for cover to avoid the rain your sympathetic system has switched on to give you energy and drive.  This term ‘Fight or Flight’ is used to describe this activity. When you sit down in the evening and relax with your favourite drink your parasympathetic system switches on; ‘Rest and Digest’.

The enteric nervous system is an ancient network of nerves that looks after itself and regulates various functions of the digestive system. Unlike the sympathetic and parasympathetic systems that use the chemical transmitters norepinephrine (noradrenaline) and acetylecholine to send signals along nerves and into organs, the enteric system also employs the chemicals dopamine, serotonin and nitric oxide.  It is interesting to note that all these chemicals are also found in the brain.

Given the intricacy of these systems and the fine balance they achieve it is perhaps not surprising that when they go wrong a person can suffer with quite considerable symptoms, many of which can be difficult for the individual to ‘put their finger on’.

Although there is large medical literature on the symptoms and clinical findings of autonomic ‘dysfunction’, it was not until the early part of the last decade that these problems became recognised as present in people who have Joint Hypermobility Syndrome (JHS).

The work of Dr Gazit based in Dr Jacobs lab in Haifa Israel (2003) was the first large study performed demonstrating the presence of symptoms and abnormalities of autonomic dysfunction in JHS. Since then much work has been undertaken by experts in the field (several of them Advisors to the HMSA). For example, it was shown in 2004 that up to 6 out of 10 patients with JHS / EDS-HM seen in clinic described some form of autonomic disturbance.

What are the common symptoms?

One of the most common concerns is the sensation of feeling dizzy or faint, or even passing out.  This happens most often when an individual changes position, sitting from lying, standing from sitting etc.  It is due to a drop in the blood pressure. We call this Orthostatic Hypotension (OH) or Orthostatic Intolerance (OI).

A similar problem, often relating to change in posture is palpitations.  Here, the heartbeat is much faster (Postural Orthostatic Tachycardia Syndrome (POTS)), and sometimes one can also experience shortness of breath and chest pain. One might experience both the fast heart beat and the drop in blood pressure.

Some people also experience abdominal symptoms such as bloating and pain. This may be associated with a change in bowel habit that fluctuates between constipation and diarrhoea.  This may be due to mechanical problems in the bowel or to autonomic problems.

Many will also feel fatigued, experience headaches, blurred or ‘tunnel vision’, and notice difficulty with their ability to concentrate (so-called ‘brain fog’).

Temperature regulation can also be affected. One can feel inappropriately hot or cold, experience flushing / redness of the skin, excessive sweating, or even lose the ability to sweat.

Why should a change in posture make a person feel faint or have palpitations?

When we sit at rest blood pools in large vessels in our legs and abdomen, the heart slows down, and our breathing becomes shallow.  The body, via the autonomic nervous system keeps close check on the small volume of blood flowing through the heart and up to the brain.  When we stand up the body has to react instantly to the fact that gravity is pulling all the blood away from the brain.  Blood vessels in the legs constrict, forcing blood back to the heart, and the heart pumps harder and faster, generating a blood pressure good enough to push blood into the brain. Sometimes these mechanisms are not as effective as they should be and blood pressure falls and/or the pulse races.

How do we measure POTS, OH and OI?

‘Postural’ or ‘Orthostatic Hypotension’ (OH) is defined by a drop in the blood pressure of more than 20 mmHg.

If the pulse rises by more than 30 beats per minute simply from changing posture (lying to sitting, or standing), the term POTS is used. This type of fast heart beat can also arise when just lying flat and often at night.

‘Orthostatic Intolerance’ (OI) occurs with sustained periods of a fast heart beat, or after a period of time standing. It may only become obvious after several minutes. Blood may  ‘pool’ in the leg veins making the legs swell, and the blood pressure falls.

All of these things can be recognised clinically by taking the blood pressure and feeling the pulse.  However, we have learned that for a lot of patients the clinical signs can be very subtle even though the symptoms are strong.

Study in this area suggests that some of the problem with the autonomic dysfunction in lies in the peripheral veins.  Whether this is due to a change in the chemical transmitters mentioned earlier, tissue laxity in the veins, or even ‘de-conditioning’ of blood vessels and muscles because of poor mobility is unknown.

The Bowel

Some patients experience uncontrollable bowel symptoms such as constipation, diarrhoea, and abdominal pains. These are much like Irritable Bowel Syndrome.

With regard to the Autonomic Nervous System, this mechanism is more difficult to explain.  One theory is that there is some form of chemical imbalance between different nerve transmitters. One way of exploring chemical balance further may be to observe the effect of anti-depressant modifications on these symptoms.  Anti-depressants affect chemical balance of transmitters such as serotonin and dopamine in the brain.  They may have an effect on these chemicals in the bowel too.  It may be that other remedies work in a similar way. The common, evidence-based treatments used to manage IBS can be found on our ‘Bowel’ webpage (click here), some as self-management and some requiring medical advice and support.

One also needs to be cautious in that bowel symptoms may arise for a number of reasons not least due to hernias or a weak abdominal / pelvic floor due to tissue laxity, as well as medications such as pain killers.  One should likewise be aware that the heart and vascular symptoms described might also be side effects or certain medications.


We have also learned from studies that patients with symptoms of autonomic disturbance are 2 to 3 times more likely to report fatigue and night sweats than those who have no vascular or bowel symptoms.  The fatigue reported by some patients with HSD or hEDS is very similar to that reported in the Chronic Fatigue Syndrome (CFS).  We feel that there is considerable overlap between these conditions.  Interestingly, doctors and researchers have documented autonomic dysfunction in CFS as well.

More information on Fatigue can be found HERE

What can be done if you suspect autonomic symptoms?

If you are at all concerned about symptoms you should discuss this with your doctor.  They may be able to demonstrate changes in your pulse or blood pressure with you lying and then standing. In which case the diagnosis is obvious.

More subtle symptoms that cannot be demonstrated by simple tests will be difficult for your doctor to assess.  They may ask a cardiologist or a Neurologist to take a look at you.  These specialists can assess you with more sophisticated tests that monitor your heart rate and blood pressure closely, and they will have lifestyle advice, advice on fluid and salt intake, and specific medications available to treat the symptoms.

One of the simplest things to try is replacing water with isotonic drinks and to keep well hydrated – but not over-hydrated. Many Isotonic drinks have carbohydrate in them so be careful but there are commercial products that do not and are available to purchase over the internet. These typically contain Sodium, Potassium, Calcium and Magnesium. One sign that the balance in hydration is about right is to look at the colour of the urine – a pale straw yellow is right – too yellow or orange is too dehydrated, and colourless urine suggests one is over-hydrated.

Even if your symptoms cannot be completely corrected, the simplest of advice such as ‘stand up more slowly’ or ‘try to avoid having to stand in one position for too long’ can make all the difference!

Bowel symptoms are much more difficult for your doctor to assess.  Here one would advise that symptoms like irritable bowel that have not responded to simple measures such as ‘over the counter’ remedies or treatments prescribed by your GP should be looked into in more details by a Gastroenterologist.

As alluded to earlier, there may be a role for anti-depressant medicines here but this needs proper conducted clinical trials, albeit that patients may note a reduction in the bowel symptoms when they have been prescribed medication for depression.

Physical exercise should also improve autonomic symptoms and fatigue. The argument goes that if one improves muscle quality in the legs and abdomen one should improve blood flow through the body and reduce the problem of venous pooling.  Reducing venous pooling should lower the risk of OH and OI.

Endocrine (hormone) imbalances such as a low cortisol may also be present and require careful investigation before any medical treatments might be recommended.

Further Advice

More on POTS and its management can be found on the following website: To go to this website click HERE.

The articles referenced below are available to read by clicking HERE and then on the relevant title in catalogue of papers on the page.


Dr Alan J Hakim MA FRCP
Consultant Physician and Rheumatologist, Chief Medical Advisor and Trustess, HMSA

V.2. Updated March 2017. Planned date of review March 2018.



Fikree A, Chelimsky G, Collins H, Kovacic K, Aziz Q. 2017. Gastrointestinal involvement in the Ehlers–Danlos syndromes. Am J Med Genet Part C Semin Med Genet 175C:181–187.

Hakim A, O’Callaghan C, De Wandele I, Stiles L, Pocinki A, Rowe P. 2017. Cardiovascular autonomic dysfunction in Ehlers–Danlos syndrome—Hypermobile type. Am J Med Genet Part C Semin Med Genet 175C:168–174.

Hakim A, De Wandele I, O’Callaghan C, Pocinki A, Rowe P. 2017. Chronic fatigue in Ehlers–Danlos syndrome—Hypermobile type. Am J Med Genet Part C Semin Med Genet 175C:175–180.


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