Blood plasma contains many vital proteins including fibrinogen, globulins and human serum albumin. Sometimes blood plasma may contain viral impurities which must be extracted through viral processing. A simple way to separate plasma from blood cells in a blood sample is by centrifugation.
Plasmapheresis (from the Greek plasma, something molded, and apheresis, taking away) is the removal, treatment, and return of (components of) blood plasma from blood circulation. It is thus an extracorporeal therapy. During plasmapheresis, blood is initially taken out of the body through a needle or previously implanted catheter. Plasma is then removed from the blood by a cell filter.
Each method has its advantages and disadvantages. After plasma separation, the blood cells are returned to the person undergoing treatment, while the plasma, which contains the antibodies, is first treated and then returned to the patient in traditional plasmapheresis. (In plasma exchange, the removed plasma is discarded and the patient receives replacement donor plasma or saline with added proteins.) Medication to keep the blood from clotting (an anticoagulant) is generally given to the patient during the procedure. Plasmapheresis is used as a therapy in particular diseases. It is an uncommon treatment in the United States, but it is more popular in Europe and particularly Japan.
What is plasmapheresis?
Plasmapheresis is a process in which the fluid part of the blood, called plasma, is removed from blood cells by a device known as a cell separator. The separator works either by spinning the blood at high speed to separate the cells from the fluid or by passing the blood through a membrane with pores so small that only the fluid part of the blood can pass through. The cells are returned to the person undergoing treatment, while the plasma, which contains the antibodies, is discarded and replaced with other fluids. Medication to keep the blood from clotting (an anticoagulant) is given through a vein during the procedure.
What's involved in a plasmapheresis treatment?
A plasmapheresis treatment takes several hours and can be done on an outpatient basis. It can be uncomfortable but is normally not painful. The number of treatments needed varies greatly depending on the particular disease and the person's general condition. An average course of plasma exchanges is six to 10 treatments over two to 10 weeks. In some centers, treatments are performed once a week, while in others, more than one weekly treatment is done.
A person undergoing plasmapheresis can lie in bed or sit in a reclining chair. A small, thin tube (catheter) is placed in a large vein, usually the one in the crook of the arm, and another tube is placed in the opposite hand or foot (so that at least one arm can move freely during the procedure). Blood is taken to the separator from one tube, while the separated blood cells, combined with replacement fluids, are returned to the patient through the same tube.