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Health Knowledge and Encyclopedia
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Blood is made up of four components, which each perform a different function:
Plasma is the largest component of blood, making up about 55% of its overall content. It is mainly made up of water and surrounds the blood cells, carrying them around the body.
Plasma also stores body fluids, helps maintain blood pressure and regulates body temperature. It contains a complex mix of substances that are used by the body to perform important functions. These substances include:
Three important proteins are found in plasma:
These are described in more detail below.
Albumin cleans the blood, carries substances around the body and helps to maintain the correct amount of fluid circulating in the body.
Human albumin solution can be used as a treatment to help people with severe burns or with liver or kidney disease.
Clotting (coagulation) factors help to control bleeding and work together with blood platelets to ensure that the blood clots effectively.
Fresh frozen plasma and clotting factor concentrates can be used to treat blood clotting disorders such as haemophilia, where an inherited lack of a specific clotting factor can cause prolonged bleeding.
Immunoglobulins are part of the immune system (the body’s natural defence against illness and infection).
Immunoglobulins are antibodies that the body produces to fight unwanted viruses and bacteria. For example, they are used to fight health conditions such as:
Normal human immunoglobulins can be used to support people who are having cancer treatment when their immune system is having difficulty producing antibodies.
Plasma is the source of anti-D immunoglobulin, a substance that is often given by injection to pregnant women with a rhesus negative blood group (RhD negative) and whose unborn baby may have a rhesus positive blood group (RhD positive).
This treatment prevents the mother becoming sensitised to the baby’s blood and stops immune anti-D developing. Immune anti-D can cause Rhesus disease in subsequent pregnancies, which is a potentially fatal condition.^^ Back to top
When plasma and plasma products are used
Plasma products can be used to help prevent health problems occurring in conditions such as Rhesus disease, and to prevent bleeding in patients who suffer with haemophilia (a lack of clotting substances).
Plasma can also be given as a transfusion when a patient has lost a lot of blood.
A plasma transfusion is where whole blood is taken from one person, known as a donor, and the plasma is separated from the red cells and then frozen until it is needed, when it is thawed and given to another person.
For example, a patient may be given a plasma transfusion if they are bleeding after a serious accident or following major surgery where clotting factors need replacing as well as red blood cells.
Before someone is able to donate blood for the production of plasma for transfusion, they have to comply with a strict set of guidelines about their medical, travel and sexual history. This ensures that their blood is safe to be transfused. As with whole blood, plasma is always checked for viruses to make sure it is safe to use.
Plasma transfused to patients who were born after January 1 1996 comes from donors outside the UK. It has been treated with a chemical called methylene blue, which is an additional step that was introduced to make plasma safer.
See the topic about Blood transfusions for more information about the process.
Plasma products made by fractionation
Many of the components that are found in plasma can be refined and extracted so they can be used to treat specific problems.
Plasma donations are pooled and then subjected to a number of different heat and chemical treatments, before the various proteins are separated out in a complex process that is known as fractionation. Fractionation can take up to five days.
All blood donations that are used to make plasma pools for fractionation have to be checked for viruses to make sure they are safe to use. In addition, the pooled plasma is carefully filtered and "cleaned" using heat, detergents and solvents to remove any viruses that may be present.
After the fractionation process has been completed, the plasma products are either freeze-dried as a powder for reconstitution before use or kept as a liquid. They are then bottled ready for distribution to clinics, surgeries and hospitals.
Some patients, such as those with haemophilia, have their own supply of plasma products so they are able to treat themselves at home.
There are hundreds of plasma products that can be created, but the three main ones are:
See Plasma products – Introduction for more information about these three plasma products.
Plasma exchange, also known as plasmapheresis, is a procedure where a special machine (see below) is used to separate plasma from the other components of a patient’s blood.
During the procedure, the plasma is removed and replaced with a substitute (usually human albumin solution) and the red cells, white cells and platelets are returned to the patient.
Plasma exchange is often used to treat a number of rare blood conditions. These are briefly outlined below.
Thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura is a rare disorder of the blood coagulation system, where microscopic blood clots damage organs and red blood cells.
Plasma exchange removes the antibody that is responsible for causing the condition, as well as replenishing blood levels of a vital enzyme using fresh frozen plasma.
Multiple myeloma and Waldenström's macroglobulinaemia
Multiple myeloma and Waldenström's macroglobulinaemia are both rare types of bone marrow cancer where abnormal bone marrow cells create large amounts of a protein called a paraprotein (immunoglobulin).
If the protein levels in the blood become too high, the blood can thicken, which is known as hyperviscosity. The symptoms of hyperviscosity include:
Plasma exchange reduces the amount of abnormal protein in the blood, which helps to relieve the symptoms. However, the process does not prevent the production of immunoglobulin. Other treatments, such as chemotherapy, may be required to achieve this.
Plasma exchange procedure
During plasma exchange, a machine called a cell separator will be used to separate the plasma from your blood. A needle will be inserted into a vein in your arm, and blood taken from your vein will be passed through the cell separator.
The plasma will be separated from the rest of your blood and a plasma substitute added, before the blood is returned through a needle in a vein in your other arm.
Plasma exchange takes about two hours to perform. During the process, only a small amount of blood (less than 100ml) will be outside your body at any one time. This is because the blood being extracted will be returned at the same rate.
The amount of plasma that is exchanged will depend on factors such as:
The number of plasma exchanges that you will need will depend on your symptoms, how much protein there is in your blood and how well you are responding to your other treatments.
Faintness and light-headedness are both possible side effects of a plasma exchange. If you feel faint or light-headed you should tell the healthcare professional who is treating you. The symptoms can usually be effectively treated by changing to a lying down position. Ensuring that you have something to eat on the day of the procedure will also help you to avoid feeling faint and light-headed.
During a plasma exchange, you may also experience numbness or a tingling sensation around your nose and mouth and in your fingers. This is caused by a substance called citrate, which is added to your blood while it is outside your body to prevent it clotting (thickening). The citrate may affect the levels of calcium in your blood.
Let the healthcare professional who is treating you know if you experience numbness or tingling sensations. They may stop the plasma exchange for a few minutes until your body adjusts to the increased citrate levels in your blood, or they may increase the level of calcium in your blood by giving you a milky drink. Eating foods that contain calcium, such as dairy products, before you have the procedure may also help.^^ Back to top
Adverse reactions to plasma products
Plasma and plasma products
Adverse reactions that you could experience after you receive a plasma transfusion include:
The risk of developing an infection after receiving plasma is very small. All blood donations that are used to make plasma have to be carefully screened for viruses to make sure they are safe.
However, as is the case with most medical procedures, there are some possible risks associated with receiving plasma. These are briefly outlined below.
Transfusion-related acute lung injury (TRALI)
Transfusion-related acute lung injury (TRALI) is a reaction that can occasionally occur in someone who receives a plasma transfusion. The person will have breathing difficulties during or shortly after the transfusion, which can sometimes be severe.
The reaction is thought to occur because the donated plasma contains antibodies (proteins produced by the donor's immune system), called HLA antibodies, that react with the recipient's white blood cells. The plasma will have been donated by a female who has been pregnant in the past and whose immune system produced the antibodies as a response to the pregnancy.
Antibodies are normally produced by the immune system to fight organisms in the blood that the body regards as "foreign", such as bacteria, but in pregnancy they have a protective role.
To minimise the risk of TRALI occurring, plasma from male donors is usually used to make fresh frozen plasma and other plasma-containing blood products that are used for transfusion.
Pooled plasma for transfusion and fractionated plasma products do not cause TRALI.
Variant Creutzfeldt-Jakob disease (vCJD)
Variant Creutzfeldt-Jakob disease (vCJD) is the human form of bovine spongiform encephalopathy (BSE), which is commonly known as mad cow disease. First identified in 1996, vCJD is a rare, neurological illness that causes brain damage. It occurs as a result of eating the meat of cattle that are infected with BSE.
The risk of developing vCJD after having a blood transfusion is very small, but there is currently no test available to screen blood for the prion protein that causes vCJD.
Each year in England and Wales, over two million units of blood are transfused. To date, there have only been a few cases where patients are known to have become infected with vCJD after having a blood transfusion.
However, to minimise the risk further, the NHS has put a number of further precautions in place. These include:
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