Heparin-induced thrombocytopenia after elective hip replacement and prophylaxis of venous thromboembolism with low molecular-weight heparin

Background: Heparin-induced thrombocytopenia (HIT) is a severe side effect of the prophylaxis of venous thromboembolism with unfractionated heparin. T he aim of the present study is to gain more information on the incidence of HIT during prophylaxis of venous thromboembolism with low-molecular-weight heparin in elective hip surgery. Methods: 586 consecutive patients were in cluded into the prospective study, who were admitted to hospital for electi ve hip replacement. The incidence of thrombocytopenia, clinically manifest venous thromboembolism and of the heparin-induced IgG antibodies were analy sed during prophylaxis with low molecular-weight heparin for a mean of 28 d ays postoperatively. Platelet counts and clinical examinations for the pres ence of venous thromboembolism were done at days 0, 2, 7 (+/- 1) and 12 (+/ - 2),Heparin-induced IgG antibodies were determined before and after a 12 ( +/- 2) days prophylaxis with low molecular-weight heparin in 265 of 586 pa tients randomly. Patients were reexamined for thromboembolic complications after 3 and 6 months. The clinical suspicion of thromboembolic complication was documented objectively. Results: None of the patients developed a decr ease of platelets of <50% of the initial value. Ten of 265 patients had ele vated IgG antibodies against heparin/platelet factor 4 before prophylaxis ( 3,8%). After the 12(+/- 2) days prophylaxis 13 of 265 patients had elevated IgG antibodies (4.9%). C14 serotonin assay was positive in 0 of 10 patient s before treatment and in 3 of 19 patients at day 12 (+/- 2). Ten patients developed venous thromboembolism postoperatively (8 x deep venous thrombosi s, 2 x pulmonary embolism, no fatal embolism). Only 1/19 patients with elev ated antiheparin IgG titres developed venous thromboembolism. The C14 serot onin assay was negative in this patient. Two patients died in the postopera tive phase due to underlying cardiovascular diseases. Conclusions: In patie nts with elective hip replacement prophylaxis of venous thromboembolism wit h low molecular-weight heparin was associated with a very low incidence of HIT, and hence screening for HIT antibodies is not required.