Thrombin generation may increase during orthopedic surgery
MedWire News: UK researchers report that when measured by ex vivo assay thrombin generation (TG) increases during both total hip (THR) and total knee replacement (TKR) surgery.
"Recent studies have shown that ex vivo measurement of an individual's potential to generate thrombin over time (via the TG test), may be more sensitive than the current tests at measuring the effect of anticoagulation," remark Laura Green (University College London) and colleagues.
To investigate this claim in the setting of orthopedic surgery, Green and team measured TG, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT), and D-dimer levels in the plasma samples of 51 patients undergoing THR or TKR surgery. The samples were taken pre-operatively, peri-operatively just after the new hip/knee joint had been inserted, and 24 hours post-operatively.
All patients received thromboprophylaxis with dalteparin or rivaroxaban, starting 6-8 hours post-operatively. The researchers compared the anticoagulant effects of each of these drugs on TG at 24 hours after surgery.
As reported in the British Journal of Haematology, the median TG lag-time and time-to-peak TG decreased from the pre-operative to the peri-operative period, while endogenous thrombin potential, peak thrombin, and velocity-index-rate increased. This, according to the team, indicates enhanced peri-operative coagulability. The results were similar in the THR and TKR groups.
Post-operatively, patients in the dalteparin group had a varied TG response, classed as favorable (reduced TG) in 7 of 21 patients, unfavorable (increased TG) in one patient, and unclear in the remaining 13 patients. In contrast the response was favorable in the majority (23 of 26) of patients on rivaroxaban.
D-dimer increased during and after surgery in all patients. F1 + 2 and TAT also increased during surgery in all patients and then significantly decreased from the peri-to post- operative period in the rivaroxaban group, but not in the dalteparin group.
Green and co-authors conclude that their findings "support the view that thrombogenecity in these orthopedic patients begins during their surgery.
"Therefore it follows that initiation of thromboprophylaxis prior to orthopaedic surgery could be more effective at preventing or reducing these peri-operative changes," they say.
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By Laura Dean