The incidence of heparin-induced thrombocytopenia Type II in patients with subarachnoid hemorrhage treated with heparin versus enoxaparin

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Heparin-induced thrombocytopenia Type II (HIT II) is a serious complication that occurs in 0.2–3% of patients treated with heparin and is associated with a high risk of thrombotic events. One center recently reported an incidence of HIT II of 15% in a population of patients with aneurysmal subarachnoid hemorrhage (aSAH). Because these patients are typically exposed to heparin during angiography, controversy exists regarding whether prophylaxis with enoxaparin rather than heparin affords any reduction in the risk of developing HIT II. In this study, the authors investigated the effect of heparin compared with enoxaparin on the incidence of HIT II in patients with aSAH.


The authors reviewed the medical records of 300 patients treated for aSAH who received thromboprophylaxis with either heparin or enoxaparin, and identified patients who developed HIT II. The incidences of HIT II in the 2 treatment groups were then compared.


One hundred sixty-six patients with aSAH were treated with heparin, and 134 patients were treated with enoxaparin. Sixteen (5.3%) of 300 patients met the diagnostic criteria for HIT II. Of those treated with heparin, 8 (4.8%) of 166 developed HIT II, compared with 8 (6%) of 134 treated with enoxaparin (difference not significant).


The authors report a lower incidence of HIT II in patients with aSAH than has previously been reported. The data also suggest that patients with aSAH who receive heparin are at no greater risk of developing HIT II than those who receive enoxaparin. This finding challenges the merit of choosing enoxaparin rather than heparin for thromboprophylaxis in patients with a SAH.

Abbreviations used in this paper: aSAH = aneurysmal subarachnoid hemorrhage; DVT = deep venous thrombosis; HIT II = heparininduced thrombocytopenia Type II; ICU = intensive care unit; LMWH = low-molecular-weight heparin; SD = standard deviation.

Article Information

Address correspondence to: Grace H. Kim, M.D., Department of Neurological Surgery, Columbia College of Physicians and Surgeons, Neurological Institute of New York, 630 West 168th Street, Room 5-462, New York, New York 10032. email:

Please include this information when citing this paper: published online October 31, 2008; DOI: 10.3171/2008.3.17480.

© AANS, except where prohibited by US copyright law.




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