Change In Coagulation Function And Hidden Blood Loss In Patients After Total Knee Arthroplasty

Introduction:Thromboprophylaxis,both mechanical and pharmacological,is a current standard practice for the prevention of VTE in patients undergoing total knee arthroplasty.LMWH or rivaroxaban are the most commonly used anticoagulants.Study found that LMWH and rivaroxaban both can effectively prevent the occurrence of DVT after TKA,but may also increase the risk of wound complications and bleeding.Ecchymosis around the wound is one of the most common complications after TKA,with an incidence of up to 13%.However,the specific mechanisms underlying the formation of ecchymosis after TKA remain unclear,and only a few studies have examined ecchymosis.Ecchymosis is related to postoperative coagulopathy.Moreover,as a type of hematoma,ecchymosis is not only caused by coagulation changes but also related to vascular injury,which can lead to additional hidden blood loss after TKA.Routine monitoring of coagulation function can assist in adjusting the dosage of anticoagulants for patients.Blood volume analysis of patients might be used to improve the perioperative blood management.Thromboelastography(TEG)provides information on coagulation defects that are often difficult to detect using conventional coagulation tests.The purpose of this study was to monitor the coagulation function and hidden blood loss of patients during TKA and to determine whether differences in the coagulation status and blood loss were present between patients.Materials and methods:a total of 142 patients with knee osteoarthritis who received a primary TKA in our institution from September 2017 to November 2017 were prospectively analyzed.All patients received the standard operation and perioperative care of elective TKA.Patients were divided into rivaroxaban group and LMWH group according to the anticoagulants used after TKA.In the rivaroxaban group,patients were closely monitored to record the occurrence of ecchymosis and were divided into an ecchymosis subgroup and a non-ecchymosis subgroup.TEG was performed the day before surgery and on postoperative day 4.Routine blood analysis,including the hematocrit(Hct),was performed the day before surgery and 4 days after.Total blood loss was calculated using the formula of Nadler.Hidden blood loss was further calculated.A further follow-up evaluation was performed 1 month after surgery,and any adverse event was recorded.Results:A total of 137 patients who received TKA at our hospital between September 2017 and November 2017 and met the inclusion criteria were included in the analysis.There were 75 patients in the Rivaroxaban group and 62 patients in the LMWH group.25 cases in ecchymosis subgroup and 50 cases in a non-ecchymosis subgroup.There was no statistical difference in the basic information of patients.Twenty-five of the 75 patients(33.3%)developed various degrees of ecchymosis surrounding the surgical site within 2-3 days after surgery.The mean area of ecchymosis was 3.64±1.63 hand.At the 1-month follow-up evaluation after discharge,all ecchymoses were absorbed and had subsided.Two patients in the LMWH group developed venous thrombosis after TKA,and two patients in the rivaroxaban group also had asymptomatic DVT(1 cases in ecchymosis subgroup and 1 cases in a non-ecchymosis subgroup).There was no significant difference in R value,a value,K value,MA value and CI value between LMWH group and rivaroxaban group(P>0.05).There were no significant differences in the total blood loss and hidden blood loss between the rivaroxaban and LMWH groups(P>0.05).No significant preoperative differences were observed in the R-time,K-time,a-angle,MA or CI between patients in the ecchymosis and non-ecchymosis groups(all p>0.05).Patients in the ecchymosis group showed a significantly decreased R-time,?-angle and CI after TKA(Table 2).However,The K-time and MA did not significantly differ between the ecchymosis and non-ecchymosis groups.The mean hidden blood loss after TKA was 349 mL,which was 93%of the total blood loss,while in patients without ecchymosis,the mean hidden blood loss after TKA was 263 mL,which was 90%of the total blood loss(p = 0.031).Conclusion:For patients with LMWH or rivaroxaban anticoagulation after TKA,there was no significant difference in TEG parameter between patients in LMWH group and rivaroxaban group.There was no significant difference in total blood loss and hidden blood loss between the two groups.Patients in the ecchymosis group showed a significantly decreased R-time,?-angle and CI,but no change was found in K-time or MA.These results imply that patients who experienced ecchymosis after TKA exhibited decreased enzymatic coagulation factor function,while platelets were not associated with ecchymosis formation.Our results show that ecchymosis after TKA was correlated with increased hidden blood loss after TKA.Personalized anticoagulation therapy and careful blood management should be applied in patients with ecchymosis after TKA.A deeper understanding of ecchymosis after TKA may be helpful for reducing the risk of postoperative complications.