Heparin Reexposure of the Patient with a History of Remote HIT

HIT antibodies are usually not detectable 3 mo after an episode of HIT (Warkentin and Kelton, 2001b). There are few data describing the clinical and serological outcomes of patients reexposed with heparin with previously documented HIT in the remote past (arbitrarily, >3 mo ago, or sooner, if HIT antibodies have disappeared). One patient who developed fatal HIT on day 15 of UFH treatment had a history of HIT complicated by thrombosis 6 yr earlier (Gruel et al., 1990). However, several patients with previous remote HIT have been observed in whom repeat heparin use caused neither HIT nor HIT antibody formation (Potzsch et al., 2000; Warkentin and Kelton, 2001b).

Because there are acceptable alternative anticoagulant options for most prophylactic and therapeutic indications, both UFH and LMWH usually should be avoided in patients with a previous history of HIT. As discussed in the following section, however, there are special circumstances, such as cardiac or vascular surgery, during which it is reasonable to use heparin for a patient with a previous history of HIT, provided certain precautions are taken.

Recommendation. Heparin should not be used for antithrombotic prophylaxis or therapy in a patient with a previous history of HIT, except under special circumstances (e.g., cardiac or vascular surgery) (grade 2C).

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