Is aspirin as effective as dalteparin (Fragmin) for extended venous thromboembolism prophylaxis in patients who have undergone total hip arthroplasty?
Aspirin is as effective as dalteparin for extended thromboprophylaxis in patients who had total hip arthroplasty and had initially received 10 days of dalteparin prophylaxis postoperatively. Because of its relative safety, low cost, and easy administration, aspirin is an attractive alternative to low-molecular-weight heparin (LMWH) when used for this purpose. (Level of Evidence = 1b)
Previous studies have confirmed the benefit of extended thromboprophylaxis with LMWH in patients who have undergone elective total hip arthroplasty. The cost of LMWH and the inconvenience of administering daily subcutaneous injections are high, however. In this study, investigators enrolled patients undergoing elective total hip arthroplasty to receive extended thromboprophylaxis with LMWH, specifically dalteparin, or with aspirin. All patients received an initial eight to 10 days of postoperative dalteparin prophylaxis. This was followed by randomization to dalteparin at a dosage of 5,000 units daily or aspirin at a dosage of 81 mg daily for the next 28 days. To preserve masking, placebo aspirin tablets and placebo dalteparin injections were also administered. Patients with metastatic cancer or those with conditions that precluded the use of an anticoagulant or aspirin were excluded. An amendment to the initial study protocol allowed patients using long-term aspirin therapy at a dosage of less than 100 mg daily to be enrolled. These patients were assigned to dalteparin or 81 mg of aspirin in addition to their usual dose of aspirin.
Because of slow recruitment, study enrollment was halted prematurely after 786 patients of a targeted group of 1,100 had entered. Baseline characteristics in the two groups were similar, with a mean age of 58 years and mean hospital stay of five days. More than 90% of the patients in the study reported adherence to all doses of the study medications. After a 90-day follow-up period, aspirin was found to be as effective as dalteparin for the prevention of symptomatic venous thromboembolism (1.3% with venous thromboembolism events in the dalteparin group vs. 0.3% in the aspirin group; P < .001 for noninferiority). There were no differences in clinically significant bleeding events between the two groups, although the trend favored aspirin (1.3% with dalteparin vs. 0.5% with aspirin). In the subset of patients using long-term aspirin therapy (n = 39), one patient assigned to the aspirin group had a clinically significant, nonmajor bleeding event, but there were no venous thromboembolism events in either group.
Study design: Randomized controlled trial (double-blinded)
Funding source: Industry
Setting: Inpatient (any location) with outpatient follow-up
Reference: AndersonDRDunbarMJBohmERet alAspirin versus low-molecular-weight heparin for extended venous thromboembolism prophylaxis after total hip arthroplasty: a randomized trial. Ann Intern Med.2013; 158( 11): 800– 806.