Current concepts review: heparin-induced thrombocytopenia.

Immune-type (Type II) heparin-induced thrombocytopenia (HIT) is a rare but potentially fatal complication that can result from the use of heparin or its derivatives employed to reduce the risk of venous thromboembolic disease (VTED) after surgery. As such, the onset of HIT creates a therapeutic paradox: VTED prophylaxis that induces systemic thrombosis. Orthopaedic patients often necessitate chemoprophylaxis after surgery because of their particularly high risk for developing VTED, but concomitantly they represent a population at high risk for developing HIT. Although HIT is known to occur after exposure to unfractionated (UFH) or low molecular weight (LMWH) heparin, it can develop with the use of any heparin-derived product. Unfortunately, the orthopaedic patient who develops this incompletely understood disease also ranks amongst the highest in development of its most devastating manifestation, HITmediated arterial thrombosis, which can result in amputation or death.29,74a,108,114 Since it remains unclear exactly how much treatment can alter the natural course of HIT, preventing its onset is paramount. This current concepts review is intended to increase the awareness and highlight the potential severity of HIT, and familiarize the orthopaedic surgeon with the many challenges associated with its diagnosis and treatment.