Plasmapheresis is a non-selective method of removing toxic mediators from the circulation. Several reports have been published on the use of plasmapheresis in severe sepsis but these have been inconclusive. Plasma is removed from the circulation and replaced with donor fresh frozen plasma during plasmapheresis. The first prospective randomised controlled trial of plasmapheresis in septic shock has come from a Russian-Norwegian collaboration. They looked at 106 consecutive patients with severe sepsis or septic shock and randomised them to receive either standard therapy or add-on treatment with plasmapheresis. The patients had equivalent APACHE III scores at entry. The main endpoint was 28-day mortality: 333% (18/54) patients in the plasmapheresis group died compared with 538% (28/52) in the control group. This represented an absolute risk reduction of 20 5% with plasmapheresis. The number needed to treat was 49 patients with severe sepsis to prevent one death. Plasmapheresis appeared to be a safe procedure. However, the study population was heterogeneous with respect to the cause of sepsis. The authors concluded that a large multicentre prospective randomised controlled trial is needed to confirm these positive results.
Plasmapheresis lowers circulating endotoxins and cytokines, but replacement of donor plasma may also replenish deficiencies in immunoglobulins and clotting factors. There are immunological similarities between severe sepsis and thrombotic thrombocytopenic purpura (TTP) in which endothelial injury results in the release of multiple mediators and the presence of a large von Willebrand factor fragment. Plasmapheresis has lowered mortality in this condition from 90 to 10%. Patient selection may be important when using plasmapheresis in severe sepsis - but data on this are awaited. At the moment plasmapheresis is sometimes considered in patients with septic shock who are not responding to conventional therapy on the ICU.
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