Blood pressure (orthostatic hypotension)

Your heart beats to pump blood around your body. One of the functions of blood is to carry oxygen from the lungs to other organs, including your brain. Blood pressure is a measure of how forcefully your heart is pumping blood around your body.

Low blood pressure (hypotension)

Low blood pressure – also known as hypotension - is pressure so low it causes symptoms such as light-headedness, dizziness, loss of balance or fainting. If this happens when someone stands up after lying down, then it is known as orthostatic or postural hypotension.

Generally low blood pressure is recognised as being below 90/60. However, what may be low for one person may not be low for another. The important thing is whether symptoms such as dizziness arise at a particular level of blood pressure.

Symptoms vary from person-to-person but commonly include:

  • dizziness or light-headedness, sometimes leading to a loss of balance or fainting
  • changes in eyesight, for example blurring, darkening or ‘closing in’ of vision
  • weakness or fatigue
  • pain around the neck and shoulders
  • passing more urine at night
  • reduced mental alertness.

These symptoms are most likely to occur when there are more demands on the circulation during periods of activity, for example:

  • first thing in the morning, particularly after lying down for several hours, and because more urine is generally passed during the night which reduces the volume of blood in the body
  • during physical exertion, as blood is diverted to the muscles leaving a reduced amount of blood in the rest of the circulation
  • if you are constipated, or if effort is required to pass urine, or when coughing - all these can reduce blood pressure
  • if you are dehydrated. A lack of fluids and salt in your body makes it harder for your autonomic nervous system to regulate your blood pressure
  • if the position of the body is quickly changed as the mechanisms to regulate blood flow may be slow to respond
  • after meals, as the level of blood is lower as more is diverted to the digestive system
  • when sitting in a warm room, in a hot bath or in hot weather, as blood vessels dilate which can lead to a drop in blood pressure
  • after a period of inactivity or bed-rest
  • as a result of anxiety as this can cause over-breathing which reduces blood pressure
  • as a result of any illness, particularly if dehydration results.

Low blood pressure is not generally dangerous, unless it causes you to faint or black out which could injure you if you fall, but it can be unpleasant and may cause mild confusion temporarily. It can also affect your ability to drive safely and you may need to inform your car insurance company. Always talk with your doctor if you drive and have low blood pressure.

Low blood pressure is also more likely in those who are older, have diabetes, have medically-treated high blood pressure, or in men with prostate problems who take medication to make it easier to pass urine. You should always tell your doctor about any medications you are taking, even if they are not related to your Parkinson’s, as these may be contributory factors to lowering blood pressure.

How is blood pressure controlled?

Blood pressure goes up and down naturally during the day. It goes up if you are stressed or doing physical activity and goes down when you are resting.

There are sensors in the main artery in your neck that report your blood pressure to your brain. This is part of the autonomic nervous system (ANS), which includes the brain, nerves and spinal cord. The ANS controls a number of automatic functions (things your body does without you thinking about them), including your heart rate and blood pressure. As there is only a certain amount of blood in your body, the supply has to be managed so you brain monitors your blood pressure and sends messages to your heart and blood vessels to adjust it as needed.

During certain activities, some parts of the body need more blood than others. For example, during exercise your blood pressure increases so that your muscles can get more oxygen. Or, if you have eaten recently, more blood goes to your stomach to allow it to digest food, reducing blood pressure elsewhere.

Your body also senses when you stand up and stops blood pooling in your legs (due to gravity). It does this by increasing your heart rate and squeezing or contracting your blood vessels, to move blood around your body.

If blood does pool in your veins when you stand, less blood returns to the heart and as a result, less blood reaches the brain. This can cause dizziness or fainting. This is called postural hypotension and can be a problem for people with Parkinson’s.

How is blood pressure measured?

Blood pressure is measured by listening to your pulse in your arm, using a stethoscope with an inflated arm cuff. Two readings are taken from each beat.

The first reading is a measure of the highest pressure when your heart pumps blood around your body (systolic pressure). The second is a measure of the lowest pressure when your heart is resting between beats (diastolic pressure). By taking the two readings, you are getting a maximum and minimum blood pressure.

The readings are given as two numbers, both measures of pressure called ‘mm Hg’. For example, if your systolic pressure is 120mm Hg and your diastolic pressure is 70mm Hg, your blood pressure is written as 120/70. Blood pressure will vary throughout the day and from person to person but a normal blood pressure reading is one between 90/60 and 140/90. Any readings outside of this range are classed as low or high.

Low blood pressure and Parkinson's

Low blood pressure is sometimes caused by Parkinson’s itself. This is because Parkinson’s affects the autonomic nervous system – the system that regulates blood pressure. The medicines used to treat Parkinson’s can also lower blood pressure.

The most common blood pressure problem in Parkinson’s is orthostatic or postural hypotension which happens when you stand up after lying down.

If you stand up after a period of lying down, blood tends to collect in the legs and abdomen and so the heart has to work hard to quickly pump blood to the brain. At the same time the tone of small arteries and capillaries increases. Both of these mechanisms help to control blood flow and regulate blood pressure, but in Parkinson’s these adjustments can be much slower or may not happen at all and so blood pressure can fall sharply and be slow to return to normal. Maintaining adequate blood pressure can also be affected by Parkinson’s medications, particularly levodopa and dopamine agonists.

In a rare type of Parkinsonism called multiple system atrophy (MSA) low blood pressure is common. This is because the autonomic nervous system is more severely affected than in Parkinson’s.

It’s unlikely that you’ll experience any serious problems from postural hypotension if your Parkinson’s medication is built up gradually, your blood pressure closely monitored and you follow the suggestions given in the How can I help myself section? below.

Remember, it is important to take your medication as prescribed. Postural hypotension alone may not be a reason to change drugs. If you are worried about your symptoms, speak to your specialist or Parkinson’s nurse about changing your medication. But remember not to stop taking your medication, because this can be dangerous.

What about high blood pressure (hypertension)?

High blood pressure is much more common in the general population than low blood pressure. It can lead to serious conditions such as stroke and heart attacks, but prompt treatment can avoid such complications.

Parkinson’s does not cause high blood pressure, although people may have it as an unrelated condition. It can be effectively treated, but a careful balance has to be found so that low blood pressure does not result.

Treatment and management

For many people simply being cautious and sensible, for example getting up slowly, not changing position quickly and responding sensibly when a drop in blood pressure is more likely, is sufficient treatment. But if problems continue talk to your doctor as they will be able to advise on strategies to help or may alter your Parkinson’s or other medications. An additional medication such as fludrocortisone may also be prescribed to increase blood volume. Your doctor will refer you to a cardiovascular specialist if necessary.

Before starting any treatment, your doctor will measure your blood pressure when you are lying down and then when you are standing. Your ongoing blood pressure should be closely monitored if any of your medication is changed or a new medication added.

If you faint you should remain flat on the ground for a while afterwards so that blood can return to your brain more easily. You may temporarily be confused due to a lack of blood in the brain but this should improve as your blood pressure returns to normal.

How can I help myself?

There are many simple steps you can take to help cope with low blood pressure. Over time, you will learn to recognise the warning signs and triggers so that you can minimise the risk of problems occuring. You might be helpful to keep a diary to monitor symptoms and triggers.

You may find the following suggestions helpful:

  • Avoid standing still unnecessarily for long periods. If possible, sit to get dressed or do other tasks and do things in stages.
  • If you have to stand for a prolonged period try to move a little by stepping on the spot or rocking forwards onto your toes then back onto your heels. It may be helpful to alternate activities to avoid the same posture for a long time.
  • Avoid sudden changes in posture, especially when getting out of a chair – get up slowly and wait for a minute before moving away. When getting out of bed let your feet dangle to the floor for a few minutes before standing up.
  • If you have to bend down or reach out, always do so slowly and try to hold onto something.
  • Try doing some gentle leg exercises, either standing, sitting or lying down. A physiotherapist will be able to suggest suitable exercises such as ankle lifts or rotations or marching gently on the spot.
  • Avoid unnecessary physical activity if it is hot and do not sit for a long time in the sun, a hot room or bath. Always make sure you drink plenty of fluid to reduce the risk of dehydration when it is hot. If you cannot avoid the heat, use a fan to cool you down.
  • Small, frequent meals, avoiding caffeine at night and alcohol, may help. Ask your doctor or a dietician if an increase in your salt intake could be beneficial. Do not increase salt intake without checking first.
  • If you feel dizzy or faint, lie down or sit down preferably with your head between your knees. Get up slowly only when the dizziness has completely passed.
  • A small drink of water before you get up may also help.
  • Raise the head of your bed using bed blocks, a wedge to hold the mattress up or an electric mattress so that your head is already above the rest of your body before getting up.
  • Check with your doctor how your medication should be taken. Certain medications may make the problem worse if taken on an empty stomach.

Important! It is important to be aware that blood pressure can significantly drop when taking medication to lower blood pressure at the same time as some Parkinson’s medications. Discuss all medications with your doctor so that he or she can decide whether medication to lower blood pressure should be adjusted.

Acknowledgement 

Our thanks to Parkinson’s UK for permission to use the following source:

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