Should patients be informed about the risk of heparin-induced thrombocytopenia before prolonged low-molecular-weight heparin thromboprophylaxis post-trauma/orthopedic surgery?

OBJECTIVES: Heparin-induced thrombocytopenia (HIT) is an immune-mediated prothrombotic adverse drug effect that occurs less frequently with low-molecular-weight heparin (LMWH) than with unfractionated heparin (UFH) in post-trauma/orthopedic surgery patients. The life-threatening nature of HIT raises the question whether informed consent for this treatment-induced adverse effect should be obtained, particularly as LMWH is often continued during the outpatient period when clinical and platelet count monitoring become problematic. Paradoxically, refusal of thromboprophylaxis as a result of seeking informed consent could increase risk for thrombosis.
METHODS: We evaluated in patients undergoing routine LMWH thromboprophylaxis post-trauma/orthopedic surgery the feasibility of obtaining informed consent, using a standardized questionnaire to determine patient preferences. We also identified the proportion of HIT patients in our laboratory comprised of trauma/orthopedic surgery patients from 1995-1997 and 2002-2004 (time periods characterized, respectively, by UFH and LMWH thromboprophylaxis for this patient population).
RESULTS: None of 460 patients in whom informed consent was administered rejected LMWH thromboprophylaxis. The patients' perception of the informed consent process and the written information provided about the risk of HIT and its risk due to clinical consequences were highly favorable. From 1995-1997 to 2002-2004, the proportion of HIT identified among trauma/orthopedic surgery patients declined from 30.3% to 1.2% (P < 0.0001).
CONCLUSIONS: Obtaining informed consent about HIT is feasible in written form and does not cause refusal of LMWH thromboprophylaxis. Despite the uncommon occurrence of HIT during LMWH thromboprophylaxis, informed consent increases patient's awareness of this potentially life-threatening adverse drug effect, an outcome that could increase outpatient recognition of the diagnosis.