The Incidence Of Low Molecular Weight Heparin-induced Thrombocytopenia And Analysis Of Related Factors

Objective: low molecular weight heparin (LMWH) is a widely used anticoagulant drug in the hospital today for coronary heart disease, vascular surgery, chronic atrial fibrillation and blood dialysis. Low molecular weight heparin enhances its coagulation factor Xa and thrombin inhibition through antithrombin (AT), and thus plays a role in its antithrombosis. Heparin-induced thrombocytopenia (HIT) is a very important adverse drug reaction, we can not ignore. That is the immune response. Combination of heparin and the heparin-platelet factor 4(PF4), as immunogen, resulting in production of antibodies, usually in the form of immunoglobulin G. The IgG/PF4/heparin immune complexes bind to Fcγreceptors on the platelet surface to produce platelet activation. Platelet activation cause a series of change, including the release of platelet microparticles, fibrinogen receptor expression increases, between platelet aggregation, and thus a large number of platelets is consumed, which result in thrombocytopenia finally. HIT final results are thrombocytopenia, thrombosis, amputation and even death. HIT is less likely to occur when low molecular weight heparin was administered. Recent data suggest that patients who do develop LMWH-induced HIT may experience severe thrombocytopenia and frequent thrombotic events. But individuals with LMWH-induced HIT exhibit a longer delay in the onset of symptoms compared with patients who have UFH-induced HIT.HIT has not been widely recognized, there are many reasons. First and foremost, the incidence of HIT is relatively low. Heparin-induced thrombocytopenia occurs in approximately 2-3% of patients receiving UFH and 1% of patients receiving LMWH. This equates to approximately 100,000 cases of HIT in inpatients in the United States. Besides, there are no clear indicators of clinical diagnosis and serological indicators. Last but not least, thrombocytopenia affected by multiple factors. For example, in addition to low molecular weight heparin other drugs, platelet disease itself, infection, etc. This makes it more difficult to diagnosis of HIT.The aim of this current study is to understand the heparin-induced thrombocytopenia diseases by comparing platelet changes of the before and after application of low molecular weight heparin. So that medical workers have some knowledge and early detection to the heparin-induced thrombocytopenia.Methods: A total of 791 patients receiving LMWH between March 2008 and January 2010, including 504 males and 287 females, with a mean age of 61.91±12 years. Blood samples were obtained through venipuncture within 24 hours of LMWH administration and at 5 to 10 days after LMWH administration, for measuring platelet count. There are two diagnostic criteria. First, a decrease in the platelet count to less than 150,000 per cubic millimeter, and a minimal decrease of 30 percent of the platelet count. Second, a 50 percent or greater decrease in the platelet count or a decrease in the platelet count to less than 100,000 per cubic millimeter. Quantitative data are reported as the median, minimum and maximal values, or mean±standard deviation (SD). Qualitative data are reported as numbers and percentages. Significance values are calculated usingχ2 or Fisher exact test. The influence of clinical baseline factors is evaluated by logistic regression analysis. A p value of <0.05 is considered statistically significant.Result: A decrease in the platelet count to less than 150,000 per cubic millimeter, and a minimal decrease of 30 percent of the platelet count or continuing decline in platelet count as the standard of diagnostic. Among the 791 patients, 20(2.53%) patients were found thrombocytopenia. In the dalteparin group, there were 4(1.34%) patients. In the Low-molecular-weight heparin calcium group, there were 15(3.33%) patients. In the enoxaparin group, there were 1(2.44%) patients. But there were significant differences among the three groups.A decrease in the platelet count to less than 100,000 per cubic millimeter, or a minimal decrease of 50 percent of the platelet count or continuing decline in platelet count as the standard of diagnostic.2 (0.25%) had thrombocytopenia, and they were Low-molecular-weight heparin calcium group. The platelet count of one patient was 98×109/L. Another patient, the platelet count was continuing decline after receiving low molecular weight heparin. There was a decrease of 41 percent of the platelet count when the patient was managed by the low molecular weight heparin in the 14 days. And there was a decrease of 62.87 percent of the platelet count in the 28 days. Two patients hadn't obvious thromboembolism.The baseline characteristics such as sex, weight, acute infarction history, old infarction history, angina pectoris, diabetes, cancer, hypertension, hyperlipidemia, history of surgery, upper respiratory tract infection, and fibrillation atrial were not significantly different between HIT group and non-HIT group. The ages in HIT group were older than non-HIT group. And chronic obstructive pulmonary disease and heart failure had higher prevalence in the HIT group than non-HIT group. In addition, the incidence of heparin-induced thrombocytopenia was lower in the receiving aspirin patients.