Comparison of pain after prophylactic anticoagulant injections to prevent venous thromboembolism

Subcutaneous injection of unfractionated heparin (UH) or low molecular weight heparin (LMWH) is frequently utilized for venous thromboembolism chemoprophylaxis. We previously discovered that nurses believe patients experience more pain with UH compared to the LMWH enoxaparin; however, no published studies that are appropriately powered exist comparing pain associated with subcutaneous chemoprophylaxis. Our objective was to assess if differences exist in pain associated with subcutaneous administration of UH and enoxaparin. We conducted an observational study of patients who underwent major abdominal surgery between 11/2017-4/2019. All patients received one of three prophylactic regimens: (1) UH only, (2) Initial dose of UH followed by enoxaparin, or (3) enoxaparin only. Of the 74 patients observed, 40 patients received UH followed by enoxaparin, 17 received UH only, and 17 received enoxaparin only. There was a significant difference in patients' mean perceived pain between subcutaneous UH and enoxaparin injections (mean post-injection pain after UH 3.3 vs. enoxaparin 1.5; p < 0.001). There was no significant difference in perceived pain for patients who received consecutive UH or enoxaparin injections. Differences in pain associated with different chemoprophylaxis agents may be an unrecognized driver of patient refusals of VTE chemoprophylaxis and may lead to worse VTE outcomes.