Management of the Patient Following Disappearance of HIT Antibodies

The drawbacks of alternative anticoagulants for CPB provide a rationale for the use of heparin in two groups of patients with a previous history of HIT: (1) a patient with a history of HIT, but who no longer has circulating HIT antibodies detected by a sensitive (washed platelet) activation assay; and (2) a patient with acute or recent HIT who requires elective heart surgery. In the latter situation, it is reasonable to delay cardiac surgery until HIT antibodies become undetectable, which usually occurs in a few weeks or months (Warkentin and Kelton, 2001b; Warkentin and Greinacher, 2003).

It is feasible to give UFH for cardiac or vascular surgery in a patient with a previous history of HIT, provided that HIT antibodies are not detectable at the time of surgery (Olinger et al., 1984; Smith et al., 1985; Makhoul et al., 1987; Potzsch et al., 2000; Warkentin and Kelton, 2001b; Warkentin and Greinacher, 2003). We recommend that heparin be avoided completely both before surgery (to prevent potential for restimulation of HIT antibodies) and after surgery (thus making HIT unlikely even if HIT antibodies are reformed). Current evidence suggests that there is a minimum time to formation of clinically significant HIT antibodies of 5 days even in patients who have a previous history of HIT (Cadroy et al., 1994; Warkentin and Kelton, 2001b; Lubenow et al., 2002b). The patient should receive routine doses of UFH for the surgical procedure itself. Preoperative anticoagulation (e.g., for heart catheterization) and postoperative antithrombotic prophylaxis can be achieved with a non-heparin agent such as danaparoid (750 U b.i.d. or t.i.d.) or r-hirudin (15 mg b.i.d. sc) (Eriksson et al., 1997) (see Chapters 13 and 14).

Recommendation. In a patient with a previous history of HIT, heart or vascular surgery can be performed using heparin, provided that HIT antibodies are absent (by sensitive assay) and heparin use is restricted to the surgical procedure itself (grade 1C).

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