Blood is one of the more important components of the body because it transfers oxygen and nutrients throughout the body as well as white blood cells, which are needed for the immune system. The parts of the blood that are free of cells are also important, however, and procedures involving plasma, which is the liquid part of the blood, can be used to treat several different diseases.
Plasma Composition
Plasma has a number of compounds dissolved in it, such as proteins, hormones and special chemicals called clotting factors, which stimulate the body's ability to form blood clots. Plasma transfusions represent one form of blood-product transfusions in which certain components of the blood are given to a patient.
Plasma Transfusion Indications
The main purpose behind giving a plasma transfusion is to increase the levels of clotting factors in a patient's blood. Clotting factors are part of a signaling pathway that enables the body to form blood clots in response to an injury. Plasma transfusions can be used for patients with a genetic deficiency that causes them to make too little or inactive versions of these clotting factors. They can also be used to treat people who are about to undergo surgery or who have liver damage that causes the liver to no longer make these vital chemicals.
Preparation
Plasma is created from whole blood by centrifuging it, which involves placing the sample in a machine that spins very rapidly. This causes the blood cells (which are more dense than the plasma) to accumulate at the bottom of the container. The plasma can then be siphoned off from the top and stored. One advantage of plasma is that it can be frozen for later use (unlike whole blood, which cannot be frozen and used later).
Effects
The Puget Sound Blood Center explains that one "unit" of plasma generally has a volume of between 200 and 250 ml. In a 70 kg patient (approximately 155 pounds), four units of plasma will increase the levels of clotting factors by 10 percent, which is considered to be the minimum threshold to see a therapeutic effect. Consequently, approximately 1 liter of plasma is needed per patient to have a noticeable effect on the patient's health.
Plasmapheresis
A different kind of plasma treatment is called plasmapheresis. As the National Multiple Sclerosis Society explains, plasmapheresis involves taking some of the patient's blood and separating it into plasma and cellular parts. The patient's plasma is then replaced with donor plasma and mixed back with the cellular part of the blood, which is then transfused back into the patient. This type of procedure is useful for diseases such as multiple sclerosis because they can be caused by abnormal immune proteins (called antibodies) attacking the patient's healthy cells. Replacing the patient's plasma removes these proteins and can help treat the disease.
