Use of enoxaparin in patients with heparin-induced thrombocytopenia syndrome

Abstract

Purpose: To determine whether low molecular weight heparin (LMWH) can be an alternative to unfractionated heparin (UH) for patients with heparin-induced thrombocytopenia syndrome (HIT).

Methods: The diagnosis of HIT was established in 126 patients by platelet aggregometry with UH (1 U/ml). These plasma samples were also tested for the ability to aggregate platelets in the presence of the LMWH enoxaparin (1 U/ml). Two patients with the HIT syndrome, after negative platelet aggregometry testing with enoxaparin, were anticoagulated with enoxaparin.

Results: Fifteen plasma samples that tested negative to UH also tested negative to enoxaparin. Forty-three of 126 (34%) UH-positive plasma samples aggregated platelets in the presence of enoxaparin. Twenty-two of 102 (22%) plasma samples with limited positive aggregation responses (minimal or no change in optical density) aggregated platelets in the presence of enoxaparin. However, 21 of 24 (88%) strongly positive plasma samples (30% to 60% change in optical density at 3 to 27 minutes) also aggregated platelets in the presence of enoxaparin. Two patients with HIT who received enoxaparin after aggregation testing demonstrated no cross-reactivity to enoxaparin achieved adequate anticoagulation and did not develop HIT.

Conclusions: Thirty-four percent of plasma samples from patients with HIT (88% of those strongly positive) aggregated platelets in the presence of enoxaparin. Patients with HIT may safely receive enoxaparin if their plasma does not aggregate platelets in the presence of enoxaparin. (J Vasc Surg 1996;23:839-43.)