Timing of Low Molecular Weight Heparin Does Not Affect Mortality in Hip Fracture Surgery

Postoperative and preoperative start of low molecular weight heparin (LMWH) does not change the outcome of mortality or risk of reoperation in patients with hip fractures treated with osteosynthesis, according to a recent study.

Thromboprophylaxis is commonly given to patients with hip fractures treated with osteosynthesis to prevent the development of thrombosis. However, thromboprophylaxis and surgery also predispose patients to the risk of bleeding, leading to anemia, reoperation, and transfusions. In practice, the administration of thromboprophylaxis is sometimes given preoperatively and other times postoperatively. To understand which method reduces mortality and reoperations while also diminishing bleeding complications, researchers used data from the Norwegian Hip Fracture Register (NHFR) to compare preoperative and postoperative starts of LMWH.

The NHFR consisted of 45,913 patients on LMWH, 45% (20,563) of patients given LMWH preoperatively and 55% (25,350) of patients given LMWH postoperatively. All primary outcomes, mortality, intraoperative bleeding complications, and reoperation, were analyzed 6 months postoperation.

After 6 months, overall mortality among all patients was 19% (8751). There were no statistically significant differences between patients receiving LMWH postoperatively or preoperatively 7, 30, and 180 days post operation.

The number of reoperations was also similar between patients given LMWH preoperative and postoperative. The total number of reoperations after 6 months was 4.5% (2067) with 115 of them due to infection, and 19 reoperations due to hematoma. Three percent (1294) of the patients on LMWH were reported to have intraoperative complications after osteosyntheses. Among these patients, 208 of the reported complications were related to intraoperative bleedings.

Upon analyzing the 2 groups, investigators found that postoperative start of LMWH decreased the risk of intraoperative bleeding complications compared with preoperative start (relative risk [RR] = 0.67). However, the number of patients treated with preoperative start of LMWH to cause 1 intraoperative bleeding complication was 434, and mainly in hip compression screw surgeries.

The type of osteosynthesis was also not a major factor that affected mortality and bleeding complications between the 2 groups. However, there was an increased 30-day mortality risk after operation with hip compression screw when LMWH was started postoperatively compared with preoperatively (RR = 1.10). In contrast, hip compression screw operations had decreased risk of intraoperative bleeding complications after postoperative start of LMWH compared with preoperative start (RR = 0.64).

Intramedullary nail operation also posed an increased 180-day risk of reoperation due to infection after postoperative start of thromboprophylaxis compared with preoperative (RR = 3.7). Patients exposed to long duration of surgery with intramedullary nail had an increased risk of reoperation due to infection after postoperative start of LMWH, compared with preoperative start (RR = 8.2). Meanwhile, patients exposed to long duration of surgery with hip compression screw had increased risk of intraoperative bleeding after preoperative start of LMWH compared with postoperative start (RR = 0.68).

From this analysis, investigators observed no significant differences among the 2 groups in terms of mortality and reoperations. However, in select surgeries and populations, there might be some benefits in exposing a patient to LMWH postoperatively or preoperatively, particularly the postoperative start of LMWH in patients with hip compression screw to reduce intraoperative bleeding. More studies will be able to verify these results in these subpopulation groups.

Reference

Leer-Salvesen S, Dybvik E, Engesaeter LB, Dahl OE, Gjertsen, J. Low-molecular-weight heparin for hip fracture patients treated with osteosynthesis: should thromboprophylaxis start before or after surgery? An observational study of 45,913 hip fractures reported to the Norwegian Hip Fracture Register. Acta Orthop. 2018:17;1-7. doi: 10.1080/17453674.2018.1519101.