The effect of salvaged blood on coagulation function as measured by thromboelastography

Abstract

Background: There is concern that salvaged blood has the potential to activate the coagulation system, which might place patients at risk of thrombotic complications. The aim of this study was to determine whether transfusion of salvaged blood after total knee arthroplasty (TKA) would lead to procoagulopathic changes as measured by thromboelastography (TEG) and furthermore if washing would reduce this risk.

Study design and methods: Twenty-two patients undergoing TKA were enrolled. Control samples were venous blood samples taken before surgery. Test samples were created by mixing the control samples with postoperatively salvaged blood, either washed or unwashed. TEG profiles were measured, noting the time to initiate clotting (R), the time of clot formation (K), the angle of clot formation (α-angle), and the maximum amplitude (clot strength [MA]).

Results: The changes in the coagulation profile from control samples to test samples were consistent for both the washed and the unwashed groups: R time decreased, MA decreased, and K and α-angle remained the same. However, the changes were more pronounced in the unwashed group than the washed group, with a 61% decrease in R time compared with 14%, and a 26% decrease in MA compared with 6%.

Conclusion: The addition of salvaged blood to the patient's preoperative blood resulted in decreased MA as well as decreased R time. This suggests that the reinfusion of postoperatively salvaged washed or unwashed blood after TKA favors a change toward a more hypocoagulable state, and washing appears to reduce this effect.

Figure 1

Thromboelastogram (TEG) trace, which gives a graphical representation of the sum of platelet function, coagulation factors, fibrin polymerization and the fibrinolytic system. The main parameters are R: time it takes to initiate clotting; K: the time to 20mm amplitude; α-angle: Slope between R and K, an indication of the rate of fibrin polymerization once initialized; and MA: the maximum amplitude of the tracing, which represents the maximum strength of the clot.