Heparin-induced coagulopathy associated with staphylococcal protein A immunoadsorption treatment columns: an in vitro and in vivo analysis

BACKGROUND: The staphylococcal protein A (SPA) column used to treat refract ory autoimmune and alloimmune thrombocytopenia and rheumatoid arthritis pat ients is primed with heparin to prevent possible fibrin clot formation when the patient's plasma is passed through the column. A BMT patient with refr actory alloimmune thrombocytopenia had prolonged activated partial thrombop lastin times (aPTTs) at the end of SPA column treatments. This observation led to in vivo and in vitro analysis of the kinetics of heparin elution fro m the SPA column. STUDY DESIGN AND METHODS: Two patients with refractory rheumatoid arthritis , who were treated on five occasions with the SPA column (as a part of a na tional trial) primed with 5000 U of heparin, were monitored for aPTT and he parin in their plasma. In addition, two in vitro analyses were performed wi th FFP for heparin elution from the SPA column. RESULTS: The in vivo studies showed the presence of 0.3 to 1.5 U per mi of heparin in patients' plasma at the end of the SPA column treatments that co rresponded with the prolonged aPTTs. The in vitro studies showed that 82 to 85 percent heparin (approx. 4400 U) was eluted from the SPA column during rather than before the procedure. CONCLUSION: Patients undergoing SPA column treatments, especially those wit h thrombocytopenia, may be at increased risk of bleeding as a result of the presence of a significant amount of heparin in their circulation during th e entire period of SPA column treatment.