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The lowdown on Low Blood Pressure

What is a low blood pressure and why might this cause symptoms?

A low blood pressure is typically defined as readings below 90/60mm Hg. The upper reading is termed the systolic blood pressure, and the lower reading is termed the diastolic blood pressure. Think of the systolic blood pressure as the amount of pressure that heart generates with each contraction, to cause forward flow of blood through the major vessels in the body. The diastolic blood pressure, on the other hand, can be considered the ongoing pressure causing continued circulation when the heart has stopped contracting, and is generally thought to represent the stiffness of arteries, supplied by the heart.

We often look at high blood pressure much more frequently, with general advice to the public to immediately tackle it and seek medical advice. It is a very important condition which has long-term cardiovascular effects and is important to identify the conditions main causes and symptoms.

However, low blood pressures can be highly symptomatic causing symptoms which are generally related to inadequate blood flow to the brain, manifesting as dizziness, light-headedness, fainting, and other more unusual symptoms such as palpitations, chest pain, nausea and brain fog.

a medical professional measuring blood pressure on a patient

So how do I know that I might have low blood pressure?

Blood pressure measurement can be taken fairly easily. This can either be taken by your GPs, or you could buy an upper arm blood pressure cuff yourself. You can view a list of list of approved BP monitors here 1 . So if you have symptoms as described above, and want to know if low blood pressure could be causing the symptoms, consider purchasing the blood pressure monitor.

However, it is important to understand that blood pressure fluctuates throughout the day, and people with symptoms of low blood pressure may not necessarily have the symptoms on a constant basis. As such, it may be even more important to document your blood pressure at the time that you might be experiencing the symptoms of dizziness, light-headedness or nausea, which will give a contemporaneous reading at the time of your maximum symptoms.

In my experience, patients present frequently with low blood pressure symptoms, and often do not record blood pressures below the hypotensive reading threshold of 90/60mm Hg. Instead, it is most common to record low normal blood pressures, anywhere between 90/60 to 120/70, with most of my patients having systolic blood pressure readings <110mm Hg. This is in itself an indication of a low normal blood pressure state, which should be considered healthy, unless you are frequently symptomatic with low blood pressure states.

If you are able to record your blood pressure when feeling unwell, then please do so and you may be surprised how variable the blood pressure readings can be, for example with postural change (when standing up, compared to sitting down).

One simple test you can do, particularly if your symptoms worsened consistently while standing, is to:

  • Take your blood pressure three times while seated with your legs shoulder width apart, resting calmly on a chair
  • Follow this by standing fairly abruptly with legs shoulder width apart, without fidgeting and with your arms by your side,  taking a further 5 to 7 recordings repeatedly, over the course of the next 5 to 10 minutes.
  • Document this data including your systolic blood pressure, diastolic blood pressure, and pulse rate, with a further column indicating your symptoms at every minute or recording.

Often, this simple chart of 7 to 10 readings of blood pressure and heart rate during an “active stand” test, may offer your consultant sufficient evidence to suggest that the problem may reside in a low blood pressure state.

What are some of the other investigations that can be done to low blood pressure?

If we suspect that you have frequent debilitating symptoms as a direct result of low blood pressure, we would like to confirm this usually by observing the blood pressure directly whilst you are having symptoms. If an active stand doesn’t show this, a different kind of test, termed the tilt table test 2, may be performed, where patients are hooked up to continuous beat-to-beat monitoring of blood pressure and heart rate, and tilted in a bed with supportive foot rests, upright to 60° angle for approximately 20 minutes. During tilt table test, sublingual nitrate (GTN: a drug given underneath the tongue as a spray that creates pooling in the blood vessels), may be given to provoke a low blood pressure state to see if the symptoms can be reproduced and correlated to changes in blood pressure and heart rate. This test is harmless, but can be very helpful in elucidating a clear mechanism of symptom onset in relation to blood pressure and heart rate changes.

Your doctor may also perform a 12 lead ECG, and ambulatory 24 hour blood pressure monitor, and other blood tests to rule out causes of low blood pressure states.

Image 1 – Normal Tilt test:

Normal Tilt test

Image 2: Tilt test positive for low blood pressure state causing syncope (loss of consciousness)

How do I treat low blood pressure symptoms?

If you have been given a very clear diagnosis of low blood pressure, causing a tendency to fainting and/or light-headedness and dizziness, then there are a few key simple conservative steps to take to manage this better. It may be worth visiting this useful resource here 3, to understand how and why a low blood pressure state can lead to various symptoms which would otherwise be difficult to explain including: dizziness, light-headedness, nausea, chest pain, palpitations, insomnia, agitation, hot and sweaty, and tingling in your extremities, as well as gut disturbances (diarrhoea and/or constipation). The reason low blood pressure states can cause this variety of symptoms, is that it could be a marker of disorder in the autonomic nervous system, the area of the nervous system that controls involuntary (sub-conscious) functions of the body.

Top tips to manage low blood pressure include:

  • Increase fluid intake, minimising caffeinated drinks, aiming for 2 ½-3L per day
  • Increase salt intake, aiming for 6-10g a day (1 to 2 teaspoons) – but only do this if you know that your blood pressure is low, or low normal.
  • Consider wearing compression stockings, which aim to compress the lower limb vessels, squeezing the blood collecting in the vessels when you stand up, back to the heart. These should be grade 2 graded compression and ideally should reach your waist, or upper thigh.
  • If your symptoms worsen immediately after eating, then you may have excessive pooling in your gut blood vessels – to combat, try taking smaller meals with less carbohydrate and also consider an abdominal binder (a thick elastic band around your abdomen, that exerts pressure into your abdomen again squeezing the blood back to the heart)
  • Taking early evasive action such as sitting down or lying down and elevating your feet when you recognise that you are about to faint because of  warning symptoms such as dizziness, light-headedness, feeling hot and sweaty, and nausea.
  • Perform isometric counter pressure manoeuvres, such as squeezing your gluteal muscles (buttocks), quadriceps (thighs) and calves to push the blood collecting in your lower limbs backup into the heart to improve blood pressure.
  • Avoid triggers of low blood pressure states, such as hot crowded environments and always carry a bottle of water especially when travelling.
  • Pre-hydrate, ideally before exercise, and first thing in the morning, when you are likely to be the most dehydrated, having not consumed any fluids overnight, as well as losing fluids by sweating (and evaporating) under the sheets, and producing all-night (most people have a full bladder in the morning!).
  • Avoid copious alcohol and if you are drinking, try to chase down each unit of alcohol with half to 1 pint of water to maintain adequate hydration.

Get in touch today

If you would like to speak to one of our specialists about your own blood pressure, or any other concerns you might have regarding your heart health, please do not hesitate to get in touch with us today. You can easily book online, or simply contact us through our online form or via telephone.

References:

  1. https://stridebp.org/
  2. https://www.imperial.nhs.uk/our-services/cardiology/syncope
  3. www.stopfainting.com

Written by Dr Boon Lim, Consultant Cardiologist at OneWelbeck Heart Health, specialising in heart rhythm disturbances including atrial fibrillation, pacing and syncope.