A simple measure to reduce the incidence of heparin induced thrombocytopenia (HIT) in cardiac intensive care patients – a retrospective observational analysis

Abstract

Heparin induced thrombocytopenia (HIT) is an immune-mediated drug reaction associated with the administration of heparin that leads to a reduced platelet count. HIT has an incidence in the general population of around 3% and causes arterial and venous thromboses that are life threatening. The diagnosis of HIT should be considered if the platelet count falls by 50% or more or below the laboratory normal range [1]. The pathophysiology involves development of IgG antibodies that recognise and bind the platelet factor 4/heparin complex resulting in platelet aggregation and thrombus formation. Our unit stopped adding heparin to the pressure transducer flush systems in both theatres and cardiac intensive care unit (CICU) and the aim of this observational study was to audit the effect on the incidence of HIT. All patients with a diagnosis of HIT who tested antibody positive on an enzyme- linked immunosorbent assay (ELISA) for the HIT antibody between 30 January 2006 and 22 March 2007 were identified (Group 1). Following removal of heparin from pressure transducer flush, HIT positive patients were also identified between 23 March 2007 and 23 March 2008 (Group 2) The incidences of HIT were compared between the groups. Twenty-one of 884 patients identified in Group 1 were HIT antibody positive whilst eight of the 802 patients in Group 2 were HIT antibody positive (p < 0.03, Chi squared test). Eleven of the 29 patients from both groups who were HPIA positive died before leaving hospital. Before March 2007, the incidence of HIT on our cardiac unit was 2.6% which is in line with the national incidence. In the year following the removal of heparin from pressure transducer flush systems, our incidence of HIT fell to 1%. This action along with use of the British Society of Haematology 2006 guidelines for the estimation of pre-test probability (the 4 Ts) happened simultaneously and both may have contributed to the decreased incidence [1]. Removing heparin from the flush systems may not only have decreased the incidence of HIT and prevented life-threatening complications but it also less expensive (500 ml saline £0.40 versus 500 ml heparinised saline £3.88). Potentially, it also reduces the number of patients who have prolonged stays in the CICU which would have a less easily quantified cost saving [2]. We thank the Department of Haematology, University Hospital of Wales and Prof J. Hall, Head of Department of Anaesthesia, UHW.