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Blood transfusion

Published by Bupa's health information team, July 2008.

This factsheet is for people who are planning to have a blood transfusion, or who would like information about it.

A transfusion is when blood or some of its components are given straight into the bloodstream through a small tube (cannula) put into a vein, usually in your arm.

Your care will be adapted to meet your individual needs and may differ from what is described here. So it's important that you follow your doctor's advice.

About your blood
Why do I need a blood transfusion?
Blood groups
What happens during a transfusion?
Where does the blood come from?
What are the risks?
Further information
Questions and answers
Related topics
Sources

About your blood

Your blood is made up of many components including:

red blood cells - these contain haemoglobin, which carries oxygen around your body
white blood cells - these are part of your immune system, fighting viruses and bacteria
platelets - these help with blood clotting
plasma - this is the fluid that carries the cells around your body

Why do I need a blood transfusion?

You may need a blood transfusion if you are lacking blood or certain components of blood. Common reasons for having a blood transfusion include having surgery or an injury that involves significant blood loss, or anaemia.

Blood loss during surgery

You have about five litres of blood in your body. You can usually cope with losing up to a litre and a half of this without too many symptoms. The lost fluid can be replaced through a saline (salt water) drip. After an operation, your body will make new red blood cells over the next few weeks. However, if larger amounts of blood are lost, a blood transfusion may be needed to replace blood more quickly.

Surgeons and anaesthetists work together to make sure as little blood as possible is lost during an operation. The aim is to avoid the need for a blood transfusion. But there are some operations, for example open heart surgery, that often require a blood transfusion, either during or after surgery.

Certain medicines, such as aspirin and warfarin, can increase the amount of bleeding. Your surgeon will usually ask you to stop taking these before an operation. Always follow your surgeon's advice about taking your medicines before and after surgery. If you are unsure about taking your medicines, please contact the hospital.

Anaemia

Anaemia is a condition in which the blood can't carry enough oxygen to meet the needs of your body. This may be because you have fewer red blood cells than usual, or the amount of haemoglobin in each cell is less than normal.

Anaemia can be caused by many things, including poor diet, excessive bleeding, illness or chemotherapy. Most types of anaemia can be treated without the need for blood transfusion.

Blood groups

You will have a blood sample taken before you have a blood transfusion. The sample is tested to see what blood group you are, and then stored safely.

Your red blood cells carry hundreds of different markers on their surface. These are called antigens, which act as 'identity tags'. Your blood group depends on which antigens are present on your red blood cells.

The two blood grouping systems that are most important for matching blood for transfusion are the ABO system and the Rhesus (RhD) system. There are other minor blood group systems, but usually they are less important for blood transfusion.

The ABO system

If you are blood group A then you have A antigens (tags) on your red blood cells. Blood group B means you have B antigens. Group AB has some of each, and blood group O has neither.

There are naturally-occurring antibodies in your blood, which defend the body against foreign antigens. For example, if you are blood group A, you will have anti-B antibodies. If you are then given group B blood in a transfusion, your natural defences (the anti-B antibodies) will attack the donated blood. This is very serious and can be fatal.

The Rhesus (RhD) system

If your blood group is RhD positive then you have RhD antigen on your red blood cells. RhD negative means you don't have it. So if your doctor tells you that you are A positive, it means your blood group is A, and you are RhD positive.

If you are RhD negative you shouldn't be given RhD positive blood, and this is especially important if you are a woman and could become pregnant in the future.

Cross-matching

For operations where a blood transfusion is very likely, your blood is cross-matched with donor blood in the laboratory, to make sure there is no reaction. A certain number of cross-matched bags of blood are kept on standby for you.

What happens during a transfusion?

A cannula is inserted into a vein usually in your arm. This is attached by plastic tubing to a bag of blood, which hangs on a stand beside you. It usually takes two to four hours hours to have one unit of blood (half a litre), although it can be given more quickly if needed.

While you are having the transfusion, a nurse will check on you regularly to make sure you are feeling well, and to measure your blood pressure, temperature and heart rate.

Where does the blood come from?

In the UK, blood is collected from healthy, unpaid volunteers. Some people donate blood regularly. The blood is screened for infectious diseases and stored carefully by the National Blood Service, which is part of the NHS.

There are two options that don't involve donated blood.

Cell salvage - blood lost during or after the operation is collected in a bag, processed and given back to you.
Autologous pre-donation or pre-deposit - for a planned operation, you may be able to donate a few units of your own blood in advance so that it can be given back to you during or after your operation.

The advantage of having your own blood given back to you is that the small potential risk of infection and transfusion reactions are minimised. However, not all patients or operations are suitable for autologous pre-donation or cell salvage. Your surgeon will explain whether they are appropriate for you.

What are the risks?

Blood transfusion is commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications of this procedure.

Side-effects

These are the unwanted but mostly temporary effects of a successful procedure.

During a blood transfusion, you may get a slight temperature or an itchy rash. If this happens, you may be given paracetamol to lower your temperature, and antihistamine or steroid medicine to relieve the rash. Also, the rate at which the blood is being transfused may be slowed.

Complications

This is when problems occur during or after the procedure. Most people having a blood transfusion are not affected.

Serious complications of blood transfusion are very rare but can include those listed here.

Immediate reaction to the donor blood - this can happen if the wrong type of blood is given accidentally. However, great care is taken in checking identities and labelling bags correctly when collecting and transfusing blood. You will be very closely monitored, and if a reaction does occur, the blood transfusion will be stopped and the symptoms treated.
Fluid collecting in your lungs - the transfusion will be slowed or stopped and the symptoms treated.
Getting an infectious disease from the donor blood - the chance of this happening is very low. All blood donors are tested for several known infectious diseases every time they give blood. Once blood is collected, it's carefully tested for hepatitis B, hepatitis C and HIV and destroyed if an infection is found.

The exact risks are specific to you and differ for every person, so we have not included statistics here. Ask your doctor to explain how these risks apply to you.

Further information

National Blood Service
08457 711 711
www.blood.co.uk