血漿分離療法中肝素引起之血小板減少症：一例報告

Heparin-induced Thrombocytopenia during Plasmapheresis: Report of A Case

肝素引起血小板減少症（heparin-induced thrombocytopenia HIT）是肝素療法中相對常見之併發症。大部分HIT病人不致有後遺症，唯也有30-60%HIT病人被發現合併嚴重之梗塞併發症引起後遺症乃至死亡。早期血漿分離療法相對於未使用者可以改善HIT之30天死亡率。本文報告一例重症肌無力病患在連續5次雙重過濾血漿分離療法後，常規抽血中意外發現血小板數目降至29,000/μL。療程中每次平均使用2,880IU的肝素。該員之血小板數目在停用肝素11天後即恢復正常，且其中未出現任何血或梗塞之併發症。鑑於HIT之免疫致病機轉，本案例在不知情下，連續5次使用肝素進行血漿分離療法，加速病人體內之免疫反應，而導致嚴重之血小板低下。因此，我們建議在使用肝素為抗凝血劑之連續血漿分離療法前/後，必需抽血檢驗血中血小板數目，以策安全。

Heparin-induced thrombocytopenia (HIT) is a relatively common complication of heparin therapy. Many patients with HIT suffer no morbidity. However, 30-60% of HIT patients develop serious thrombotic complications resulting in morbidity or mortality. Early plasmapheresis was associated with a marked decrease in 30-day mortality compared with controls. We report a myasthenic patient who was incidentally found to have severe thrombocytopenia (29,000/μL) after 5 consecutive sessions of double filtration plasmapheresis. A mean of 2,880 IU of heparin was used in each session of plasmapheresis. Her platelet counts were normalized 11 days after discontinuation of heparin. No clinical bleeding or thrombotic complications were noted. Based on the immune-mediated mechanism for HIT, repeated plasmapheresis in this heparin-sensitive patient will accelerate the immune reaction and result in severe thrombocytopenia. Therefore, routine check-up of platelet counts before/after consecutive sessions of plasmapheresis is warranted in all patients with plasmapheresis using heparin as an anticoagulant.