What causes low blood pressure?

Blood pressure measuring

I suffer from low blood pressure, which means I often feel dizzy. What causes this and what are the treatments?

Dr Paolo Tammaro says:

High blood pressure (hypertension) is a major medical concern. If untreated, it can lead to heart attacks, strokes, kidney damage and even premature death. Low blood pressure might therefore seem desirable. However, excessively low blood pressure (hypotension) can cause light-headedness, blurred vision, weakness and difficulties in concentration.

If it causes issues, low blood pressure can be treated with different medicines, depending on the underlying cause

Thinking about a hosepipe is an easy way to understand how your blood pressure is regulated. Opening the tap increases water pressure in a hosepipe; in the body, increased heart activity pumps more blood into circulation, which raises blood pressure.

Narrowing the pipe increases pressure (if you have a smaller nozzle or you put your fingers partly over the end of the hose, the water comes out with greater force). The same thing happens in blood vessels when fatty deposits make them narrower.

The kidneys control blood volume, so are also involved in regulating blood pressure.

Low blood pressure can have various causes. For example, it may occur when you stand up (postural hypotension), or after eating, when blood flow to your digestive system increases (this is most likely to occur if you have a disease of the nervous system, such as Parkinson's). The body should respond by increasing your heart rate and the narrowing blood vessels, so that enough blood gets back to the heart – if not, blood pressure falls.

Some medical emergencies such as septic shock and anaphylactic shock will also cause dangerously low blood pressure.

If it causes issues, low blood pressure can be treated with different medicines, depending on the underlying cause. Beta-agonists make the heart beat faster, while alpha-agonists narrow the blood vessels.

With the help of BHF funding, my lab is studying how to use drugs to control the width of arteries and therefore blood pressure

Drugs such as fludrocortisone, a steroid that makes your kidneys retain water and salt, increasing your blood volume, can also be used. Not all patients respond well to these treatments or tolerate the side effects – pharmacologists and other scientists are looking for new drugs.

With the help of BHF funding, my lab is studying how to use drugs to control the width of arteries and therefore blood pressure.

In particular, we are looking at the tiny channels in the artery wall that allow charged ions to go in and out of the artery cells, causing small electrical impulses.  Drugs acting on these channels have the potential to control the width of arteries and could offer new ways to control low and high blood pressure.

Dr Paolo TammaroMeet the expert

Dr Paolo Tammaro is Associate Professor in Pharmacology at the University of Oxford.

 

 

More useful information