Plasma Exchange (PLEX or plasmapheresis)
Plasma Exchange (PLEX) is a procedure whereby blood is filtered into two components, the cells (which include the blood and immune cells) and the plasma (which contains proteins, antibodies, fats, and everything else). After filtration, the machine removes the plasma and returns the cells. PLEX is a way of filtering out the inflammatory mediators out of the bloodstream during an inflammatory attack. Because NMO attacks are initiated in the blood, PLEX works well to quell relapses.
There are a few studies supporting PLEX in the acute treatment of NMO relapses. Most of these studies are retrospective subject to bias, but our experience at Johns Hopkins with over 100 NMO relapses over the past 8 years is that PLEX works > 80% of the time in cases where steroids alone has not been effective.
In order to filter the blood, a large catheter must be placed in the neck or chest to access a large vein. Each PLEX session takes about 2 hours and a full course of PLEX requires 5 sessions. Because of the risks associated with moving lots of blood in and out of the body, sessions are spaced apart every other day. There are three main risks associated with PLEX. First is blood clots related to the large catheter. Second is infection. Third is blood volume shifts which can stress the heart, kidneys and placenta (should not be done in pregnant women).
Following a 5-session PLEX course for an acute NMO relapse, most patients are transferred to rehabiltiation facility to begin a physical therapy program. In general, if there is some recovery during the PLEX sessions, the long term outcome is better. But even if there is no improvement at the end of the PLEX sessions, there is likely to be some healing in the next weeks to months.
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