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. However, this treatment must be seen as a part of a comprehensive approach.
Plasmapheresis in the treatment of myasthenia gravis has led to disparate results when applied by different investigators because of considerable differences in the volume, number, and tempo of plasmaphereses and in the type and amount of concomitant immunosuppressive drug therapy. Used as short-term crisis intervention, plasmapheresis produces temporary clinical improvement and reduction in titer of antibody to acetylcholine receptor, even without accompanying drug therapy. When applied as long-term primary therapy under optimal conditions, plasmapheresis is capable of generating stable improvement in most patients. This response appears to result from a synergistic action with immunosuppressive drugs, since it is characterized by a sustained reduction in titer of antibody to acetylcholine receptor. Where clinical circumstances warrant cytotoxic immunosuppression in patients with myasthenia gravis, consideration should be given to the simultaneous employment of plasmapheresis, in order to maximize benefit to the patient from a given exposure to drug therapy.
It is surprising that a good controlled trial of plasmapheresis in MG has never been performed. The only randomised controlled trial did not show long-term benefit but methodological flaws prevented definitive conclusions. Improvement following plasmapheresis occurs within a few days, much faster than for other immunomodulating therapies. Plasmapheresis is an established therapy for patients in myasthenic crisis. It is also often used to improve strength (if necessary) in patients prior to undergoing thymectomy. Plasmapheresis is also used for the treatment of weak patients admitted to the hospital for initiation of corticosteroids. Infrequently, chronic, intermittent plasmapheresis is used in patients refractory to other therapies.
The effects of a course of plasmapheresis last only several weeks. The risks of a chronic indwelling catheter (pneumothorax in the short term and infection and thrombosis in the long term) make chronic plasmapheresis a relatively unattractive long-term treatment option. A course of plasmapheresis usually consists of four to six exchanges, removing 3 to 5 L of plasma each treatment, performed daily or every other day. There is no precise prescription governing the number, volume, and frequency of exchanges. The course of plasmapheresis is dependent to a large extent on how well a patient tolerates the procedure and how quickly and thoroughly the patient responds. Plasmapheresis produces large fluid shifts and patients are susceptible to hypotension and, in individuals at risk, myocardial infarction. It is rare to see it used on a chronic basis.
1.Is it considered standard of care for symptomatic myashtenia graviss?
Yes, as short term intermittent intervention while other approaches are being tried.
2.Is is standard of care for stable disease?
Gajdos P et al. Plasma exchange for myasthenia gravis. Cochrane Review. Cochrane Library, Issue 4, 2003.
De Feo LG, Schottlender J, Martelli NA, Molfino NA. Use of intravenous pulsed cyclophosphamide in severe, generalized myasthenia gravis. Muscle Nerve 2002;26:31-36