Predictive and protective factors for allogenic blood transfusion in total knee arthroplasty. A retrospective cohort study.

Background: This study aimed to identify the predictive and protective factors of blood transfusion in patients undergoing total knee arthroplasty (TKA) and therefore determine the profile of patients with low and high risk of blood transfusion after arthroplasty. Methods: We conducted a retrospective study with all patients who underwent primary TKA between January 2017 and December 2019 (n = 1.028 patients) in our institution. Information about allogenic transfusion was collected from medical records to determine the incidence, the predictive and protective factors of blood transfusion. All cases of blood transfusions were documented as well the number of units and the moment of each transfusion. We performed univariate and multivariate logistic regression analyses to identify the independent risk and protective factors. Results: The total transfusion rate was 11%, 1.1% at intraoperative and 9,9% at postoperative period. The independent risk factors for transfusion were female gender (OR 1.64), older age (>55yo, OR > 2) higher surgical risk (ASA III, OR 3.07), lower preoperative hemoglobin levels (p = 0.024), post-traumatic arthritis (OR 4.11) and use of postoperative drains (OR 1.81) The protective factors for transfusion were male gender (OR 0.60), obesity (IMC >30, OR 0.60) and use of intravenous tranexamic acid intraoperatively (OR 0.40). Conclusions: We conclude that in addition to the well-established risk factors for blood transfusion such as advanced age, low hemoglobin levels and high surgical risk, we can add post-fracture arthroplasty, non-use of tranexamic acid and the use of postoperative joint drain.