PB1477 - An Early Coagulation Factor Dominant Hypercoagulability is Followed by a Prolonged Platelet-Dominant Hypercoagulability in Patients with Hip Fracture

Background: Despite thromboprophylaxis, the risk for venous thromboembolism (VTE) after hip fracture surgery (HFS) remains high (2.5%) and 45.3% of VTE events are diagnosed more than six weeks post-fracture, beyond currently recommended thromboprophylaxis. Thrombelastography (TEG) is a whole-blood assay which provides a comprehensive real-time analysis of hemostasis, from clot initiation to fibrinolysis.

Aims: To determine the timing of different phases of coagulation responsible for hypercoagulability in HFS patients.

Methods: In this prospective cohort, TEG analysis was performed in HFS patients every 24-hours from admission until post-operative day (POD) 5, then at 2-week, 6-week, and 3-month post-operative follow-up (REB16-2240). Hypercoagulability was defined by TEG parameter values beyond the reference range for clot initiation [Activated Clotting Time (ACT), Reaction-time (R-time)], and >65mm was used for Maximal Amplitude (MA), a measure of platelet contribution to maximal clot strength. One-sample t-tests were performed at follow-up timepoints and paired t-test was performed to compare follow-up timepoints to admission values.

Results: In total, 121 patients provided informed or surrogate consent (81.0 [IQR 71-87] years). ACT and R-time demonstrated progressively shorter time to clot initiation compared to admission values until POD4 [(ACT mean difference=11.7sec, SEM=2.1; p< 0.001), (R-time mean difference=0.13min, SEM=0.02; p< 0.001)] signifying increased coagulation factor dominant hypercoagulability immediately post-operatively. MA values demonstrated a peak two weeks post-operatively (mean MA=70.8, SD=2.7; p< 0.001) and remained elevated six weeks post-operatively (mean MA=65.9, SD=4.0; p=0.04). Symptomatic VTE events were detected in three patients (2.5%) and all demonstrated platelet-dominant hypercoagulability at the 6-week follow-up.

Conclusion(s): TEG analysis was able to quantify early hypercoagulability after HFS that is related to increased procoagulant factor activity, supporting thromboprophylaxis within 24 hours of surgery with anticoagulants that target procoagulant factors. A prolonged platelet-dominant hypercoagulability then ensued beyond recommended thromboprophylaxis duration. Future studies evaluating alternative thromboprophylaxis that target procoagulant factors and platelet hyperactivity may help prevent VTE after HFS.