Plasmapheresis (plasma exchange) is a process that allows undesirable agents to be removed from the body. Patients with myasthenia gravis, for example, often have high levels of antibodies for a chemical receiver called the acetylcholine receptor. These antibodies destroy the receptor and keep acetylcholine from carrying messages from nerves to muscles. Without the message, muscles cannot function properly and weakness occurs. When the antibodies are removed, weakness often improves.

Plasma exchange may be recommended before patients with myasthenia gravis have any type of surgery, so that the body's muscles will be stronger during the procedure. This process may also be used short term to treat periods of severe weakness. It is not a long-term treatment for myasthenia gravis.

The average adult has about four to six liters (4.2 - 6.3 quarts) of blood, depending on gender and size. During plasma exchange, a special machine is used to exchange about two to three liters of blood.

The plasma exchange procedure begins with the placement of a needle into each of two veins. In some cases, only one vein may be used. The veins at the elbows are often used. If the arm veins are too small, a doctor may place a special indwelling catheter into a large vein in the shoulder or groin. The needles are then connected to the plasmapheresis machine.

Plasmapheresis, or plasma exchange, replaces the patient's blood with a mixture of the patient's own red blood cells and artificial plasma -- the liquid portion of blood that contains the antibodies for the acetylcholine receptor.

In this painless procedure, blood is removed from the body via a needle connected to the plasma exchange machine. After the patient's red blood cells are collected, the plasmapheresis machine spins the blood very fast. The cells form what appears to be a solid substance, which is then collected and mixed with artificial plasma. The mixture is then returned to the body via another needle.

The procedure takes place in a clinic and can last between one and three hours. The length of time required depends on the amount of blood that is exchanged. Nurses who have received special training in plasmapheresis monitor patients throughout the procedure.

Most patients require several plasma exchange treatment sessions. In general, patients have two or three sessions per week for two weeks.

Plasmapheresis is an expensive procedure. In many cases, it is covered by health insurance. However, it is always a good idea for patients to check with their insurance company before the first session. In some cases, the doctor's office checks for insurance coverage on the patient's behalf. Patients may want to contact their doctor's office before contacting the insurance company.

Most patients have significant improvement in symptoms after plasma exchange. However, this improvement often lasts only three to four months. In cases in which drugs are also given to suppress the immune system, the effects may last longer. Patients can also have side effects from plasma exchange. These side effects include low blood pressure, clotting within a blood vessel, bleeding, infection, low levels of calcium, and reactions to the artificial plasma. Some of these side effects improve with time while others may require additional medical treatment.

The Cochran Review, which reviews the scientific evidence for various treatments, found that there were no adequate randomized controlled studies of plasma exchange therapy for MG patients, but noted that many case studies reported benefits. The reviewers concluded that the relative benefits of plasma therapy were still unconfirmed, and recommended further research.

References

First published April 1, 2000
Last updated November 25, 2002
Copyright © 2000 Accordant Health Services, Inc. All Rights Reserved.

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