This information is about platelet transfusions.
Platelets are tiny cells that are found in the blood. Their function is to help the blood to clot. Platelets are made in large numbers by the bone marrow (the spongy material inside the bones). Each platelet develops in the bone marrow and is then released into the bloodstream where it circulates around the body through arteries, veins and blood vessels. Platelets usually survive for 7-10 days before either being destroyed by the liver or spleen, or being used to clot the blood.
When a blood vessel is damaged - for example, by injury - platelets travel to the damaged area. They bind together tightly forming a clump. The platelets stimulate the formation of a substance called fibrin, which binds them together tightly to form a clot. They alsoand release chemicals to make the blood vessels narrower. These chemicals attract more platelets to the area, making the clump bigger. This reduces blood loss from the damaged blood vessel. The platelets also stimulate the formation of a substance called fibrin, which binds them together to form a clot.
Why platelet transfusions are given
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Sometimes the number of platelets in the blood is lower than normal. This may be because of illness such as cancer, leukaemia or certain blood disorders, or because of a side effect of chemotherapy treatment. If your bone marrow is not working normally, the number of platelets in your blood (known as the 'platelet count') may drop. How low the number of platelets gets depends on how much the illness or the chemotherapy has affected the cells in the bone marrow.
The normal platelet count in an adult is between 150 and 400. A slightly low platelet count won't usually cause any problems. The risk of bleeding increases as the platelet count drops, but it rarely happens unless the count is lower than 80-100. Signs of a low platelet count include nosebleeds, bleeding gums, heavy periods, bruising and tiny blood spots in the skin known as petecheia. You should tell your doctor straightaway if you have any of these symptoms.
Very rarely, more serious bleeding - for example, into the brain or the digestive system - can occur. Serious bleeding is very rare and usually only happens if the platelet count drops below 10. Although it may happen at higher levels (perhaps up to 30) if you also have a high temperature because of infection. It's important that you contact the hospital if you know that your platelets are low and you develop a temperature above 38°C (100.4ºF).
In hospitals, platelet transfusions are often used to prevent the platelet count from dropping too low. Your doctors will check your platelet count regularly and will be aware of when it’s falling. If you do have a low platelet count, it may be necessary to have a platelet transfusion. This is particularly important before certain procedures where there is a risk of bleeding, such as a lumbar puncture or bone marrow aspiration. The platelet transfusion will reduce the risk of any bleeding during or after the procedure.
Having a platelet transfusion
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The transfusion itself involves a small tube called a cannula being placed into a vein in your hand or arm. This is then connected to a drip. The platelets are run through the drip (infusion). Some people have a transfusion given through a larger tube put into a vein in the chest (central line) or the crook of their arm (PICC line).
The platelets are stored in small plastic bags that are kept at a low temperature. Each bag is called a ‘unit’ and contains about 100ml of yellow fluid.
The platelets will have been collected from blood donated by 3-5 people (donors). Sometimes the platelets are collected from a single person using a special machine that separates the platelets from the blood. The machine is called an apheresis machine and platelets collected in this way are referred to as apheresed platelets.
It takes 15-30 minutes to give each unit to you. Normally one unit is enough to prevent or stop bleeding. Occasionally two units are needed.
Despite having platelet transfusions, you may still notice problems with bleeding or bruising. It's important to let your doctors know about this, as other things can be done to help if this happens. As it only takes a short time to give the platelets, this treatment can be given in the day unit or outpatients department. Platelets can also be given before or after other treatments.
Severe side effects from platelet transfusions are rare. The more common side effects include itching, rashes, a high temperature and shivering. This is sometimes referred to as having a 'reaction'. A nurse will monitor you during the transfusion. If you do have any side effects, let the nurse or doctor know and they can give you medicines to help stop the reaction.
Having apheresed platelets reduces the risk of becoming sensitive to the platelets and having a reaction to the transfusion.
If you are having platelets frequently, it is possible for them to become less effective - this is known as becoming 'refractory' to platelets. This is rare and can occur for two reasons: non-immune causes and immune causes.
These include having a high temperature, as platelets are used up faster if you have a temperature. Some medicines such as antifungal drugs can also lower the platelet count. Or if the spleen is enlarged platelets can collect there instead of circulating in the bloodstream. The spleen may sometimes become enlarged because of the cancer or infection.
Platelets can become less effective when your immune system recognises the donated platelets as different from your own. Your body then produces antibodies (proteins produced by the body to fight a foreign substance). The antibodies quickly attack and destroy the platelets. This occurs most often in people who have had many blood and platelet transfusions.
If an immune reaction occurs, a blood test can be taken to check for antibodies, and the platelets you are given can be checked to make sure that they are similar to your own. This is known as cross-matching, and certain groups of proteins on the cell surface are looked at to make sure they are similar. Cross-matching should increase the effectiveness of the platelets that are given.
Having more than one transfusion
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Many people only need a few transfusions during their illness, while others need many. Platelets can usually be given repeatedly without causing any problems.
Are platelet transfusions safe?
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Some people worry that the platelets they are given may be infected by disease. People who donate blood are carefully screened to assess their risk of having an infection or virus, such as hepatitis or HIV. This is to make sure the blood and platelets they donate is as safe as possible.
Other precautions are also taken to minimise the risk of infection. All donated blood and platelets are tested in the laboratory for infection before they are given. Very occasionally these tests fail to find an infection, but the risk of being given infected blood or platelets is extremely small.
If you have any concerns about receiving a platelet transfusion, you can talk these over with your doctor or specialist nurse.
This section has been compiled using information from a number of reliable sources including:
Thanks to Professor Rajnish Gupta, Consultant Medical Oncologist, and all of the people affected by cancer who reviewed this information. Reviewing information is just one of the ways you can help when you join our Cancer Voices network.