UFH reexposure for urgent cardiac surgery in a patient with a history of HIT. Patient 8 in Table 1. (A) Summary of the clinical (upper panel) and serological (lower panel) features of the patient’s previous episode of HIT (1999). The patient had unusually severe HIT but ultimately did well with therapeutic-dose danaparoid sodium (no new or progressive thrombosis and no ischemic limb loss). The patient tested strongly positive in the SRA, EIA-IgG, and EIA-IgA, and weakly positive in the EIA-IgM tests. (B) Summary of the clinical (upper panel) and serological (lower panel) features of the patient’s UFH reexposure to permit urgent cardiac surgery (2002). After reexposure to UFH, the patient had early-onset and persistent thrombocytopenia (platelet count nadir, 29 × 10⁹/L on POD 6), but this was not related to HIT (the SRA tested negative on POD6). The prolonged period of postoperative thrombocytopenia was probably also unrelated to subsequent formation of platelet-activating antibodies, given that the platelet count recovery occurred as the patient was developing a strongly positive SRA, and given that the buffer control (ie, at 0 U/mL UFH) reactivity in the SRA remained negative throughout the postoperative period and also remained negative in the presence of danaparoid (data indicating absence of danaparoid cross-reactivity not shown). IV, intravenous.