Critically evaluate the role of plasmapheresis in Intensive Care patients.
Plasmapheresis is used for a wide variety of conditions but predominantly immunologic, neurologic or haemopoietic diseases. It is used to remove large molecules unable to be removed by less expensive techniques (eg. autoantibodies, immune complexes etc.), that are thought sufficiently toxic to require immediate removal. Replacement for plasma removal is either using large volumes of plasma (eg. especially in Thrombotic Thrombocytopenic Purpura [TTP]) and/or albumin. Plasmapheresis is associated with a variety of potential problems including those related to the procedure (eg. hypotension, dyspnoea, dilutional coagulopathy, immuno-suppresssion and infection), the replacement fluid (eg. hypocalcaemia, metabolic alkalosis), and the access catheters (eg. mechanical and infective).
Adverse reactions are more common using plasma as a replacement fluid (including paraesthesia, muscle cramps, and allergic reactions). These risks must be balanced against any potential/purported advantages.
The American Association of Blood Banks (AABB) and the American Society For Apheresis have published acceptable evidence based indications (Smith Transfusion 2003). Category I indications are defined as “conditions where plasmapheresis is standard and acceptable, either as primary therapy or as a first-line adjunct to other initial therapies. Efficacy is based on controlled or well-designed clinical trials or a broad base of published experience”. Relevant Category one conditions in ICU include: Guillain-Barre and Acute and chronic inflammatory demyelinating polyradiculoneuropathy, Anti-GBM disease (Goodpasture’s syndrome), TTP and post-transfusion purpura.
Plasmapheresis is discussed in the answer to Question 21 from the first paper of 2013, and in even greater detail in Question 14 from the first paper of 2010. Between these two answers, the advantages and disadvantages of plasma exchange are well covered.