This chapter about the recognition, treatment, and prevention of
heparin-induced
thrombocytopenia (HIT) is part of the Seventh ACCP Conference on Antithrombotic and
Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading, see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients in whom the risk of HIT is considered to be > 0.1%, we recommend platelet count monitoring (Grade 1C). For patients who are receiving therapeutic-dose
unfractionated heparin (UFH), we suggest at least every-other-day platelet count monitoring until day 14, or until UFH is stopped, whichever occurs first (Grade 2C). For patients who are receiving postoperative antithrombotic prophylaxis with UFH (HIT risk > 1%), we suggest at least every-other-day platelet count monitoring between postoperative days 4 to 14 (or until UFH is stopped, whichever occurs first) [Grade 2C]. For medical/obstetric patients who are receiving prophylactic-dose UFH, postoperative patients receiving prophylactic-dose
low molecular weight heparin (
LMWH), postoperative patients receiving intravascular
catheter UFH "flushes," or medical/obstetrical patients receiving
LMWH after first receiving UFH (risk, 0.1 to 1%), we suggest platelet count monitoring every 2 days or 3 days from day 4 to day 14, or until
heparin is stopped, whichever occurs first (Grade 2C). For medical/obstetrical patients who are only receiving
LMWH, or medical patients who are receiving only intravascular
catheter UFH flushes (risk < 0.1%), we suggest clinicians do not use routine platelet count monitoring (Grade 2C). For patients with strongly suspected (or confirmed) HIT, whether or not complicated by
thrombosis, we recommend use of an alternative
anticoagulant, such as
lepirudin (Grade 1C+),
argatroban (Grade 1C),
bivalirudin (Grade 2C), or
danaparoid (Grade 1B). For patients with strongly suspected (or confirmed) HIT, we recommend routine ultrasonography of the lower-limb veins for investigation of
deep venous thrombosis (Grade 1C); against the use of
vitamin K antagonist (VKA) [
coumarin]
therapy until after the platelet count has substantially recovered; that the VKA antagonist be administered only during overlapping alternative anticoagulation (minimum 5-day overlap); and begun with low, maintenance doses (all Grade 2C). For patients receiving VKAs at the time of diagnosis of HIT, we recommend use of
vitamin K (Grade 2C) [corrected] For patients with a history of HIT who are HIT antibody negative and require cardiac surgery, we recommend use of UFH (Grade 1C).