In enzyme assays it is convenient to
In enzyme assays, it is convenient to quantify the product formed in the enzyme reaction, where a decrease in the concentration of product indicates enzyme inhibition , , , . In the present study, substrates were carefully chosen so that they are specific to each enzyme. Known natural substrates for thrombin include coagulation factors V, VIII, XI and XIII, protein C and fibrinogen , . The natural substrate for FXa is prothrombin. Both thrombin and FXa prefer to hydrolyze an arginyl bond, which facilitates us to employ the similar peptide substrates for two enzymes. The proposed assay is based on the enzymatic cleavage of the substrates, S2238 by thrombin or S2765 by FXa, to release the same product, p-nitroaniline (pNA). In this manner, it is attainable to measure the combined inhibition effects of two lfm solely by detecting the formation of pNA. The reason for choosing chromogenic substrates instead of natural substrates is to make it easy to compare the results with previously reported studies. However, it is worth to mention that there is no particular requirement for the chromogenic substrate as a UHPLC MS/MS method.
Results and discussion
Acknowledgement This work was supported by the National Natural Science Foundation of China (21505124), and China Postdoctoral Science Foundation (2015M582144). The authors thank Professor Xia Zhao for providing the alginate-derived sulfated polysaccharides.
Introduction Hip fracture is a common cause of hospital admission and non-elective surgery among geriatric patients, with an annual mean of 958 hip fractures per 100,000 individuals in the United States . Venous thromboembolism (VTE) is a well-known complication that may occur following any orthopaedic injury or procedure, including surgical treatment of hip fractures. Pharmacologic VTE prophylaxis is often used in this setting to mitigate risk, and is recommended by the American Academy of Orthopaedic Surgeons (AAOS) Clinical Practice Guidelines . A variety of anticoagulants have been shown to be effective at reducing the rate of VTE, including warfarin (which interferes with clotting factors II, VII, IX, and X via vitamin K antagonism), enoxaparin (which acts directly on the protein antithrombin), and aspirin (an anti-platelet), among others , , , , . Despite the evidence in favor of VTE prophylaxis for hip fracture patients, there is limited data to guide surgeons when selecting a pharmacologic agent. In addition, newer anticoagulants such as Factor Xa inhibitors (XaI) are gaining popularity. These have some advantages compared with more traditional prophylaxis agents, including rapid onset, lack of required laboratory monitoring, and in some cases oral administration. They have also been shown to be effective for VTE prophylaxis in total joint arthroplasty , , , , . However, data on their use in hip fracture patients is limited , , , and to our knowledge no large databases have been utilized to assess the efficacy of various chemoprophylactic agents, including Factor Xa inhibitors, for VTE prevention among hip fracture patients.
Patients and methods All patient records were queried to identify patients Dicentric chromosome underwent surgical treatment of a hip fracture between 2007 and 2015, using Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision (ICD-9) codes (Table 1). Patients were age sixty or older at the time of surgery. We then identified those hip fracture patients who had a VTE chemoprophylaxis agent prescribed within two weeks of surgery and divided them into three cohorts: those who received 1) warfarin, 2) Factor Xa inhibitors, or 3) enoxaparin. Any patient who had been prescribed an antiplatelet or anticoagulant within 1year prior to surgery was excluded. Cohorts were matched by age and gender by proportions. We then compared Charlson Comorbidity Indices (CCI), standard demographic factors and comorbidities as described previously , and rates of deep vein thrombosis (DVT), pulmonary embolism (PE), significant bleeding events, post-operative anemia, and post-operative transfusion at 2 weeks, thirty days, 6 weeks, and ninety days between the three cohorts, which were identified using CPT and ICD-9 codes (Table 1).