Preoperative Tranexamic Acid, Tourniquet Use, and Recorded Intraoperative Blood Loss in Total Knee Arthroplasty

Background: Anesthesiologist-estimated blood loss is a frequent outcome in retrospective blood-conservation studies, but whether it captures the effect of tranexamic acid (TXA) in total knee arthroplasty (TKA) is unknown. Methods: This retrospective cohort study included primary unilateral TKAs in patients aged 40–75 years (2024–2025) at a public hospital in Mexico. The primary outcome, intraoperative blood loss recorded on the anesthesia record, was analyzed with linear regression including a TXA × tourniquet interaction and prespecified confounders. Predictors of TXA use and recording patterns were examined. Results: Of 343 patients, 125 (36.4%) received 1 g intravenous TXA and 233 (67.9%) had a tourniquet. TXA was not associated with recorded blood loss without a tourniquet (adjusted difference +15 mL; 95% CI −73 to 103) or with one (+24 mL; −18 to 65), whereas the tourniquet was associated with −349 mL (−405 to −293). Clinical and organizational variables did not predict TXA use (optimism-corrected AUC 0.54). Without a tourniquet, 95.5% of values were multiples of 50 mL; with a tourniquet, 0 mL was recorded less often after TXA (adjusted OR 0.43; 0.23–0.80). Conclusions: Recorded intraoperative blood loss reflected tourniquet use and recording habits, not preoperative TXA, and should not be used to evaluate antifibrinolytics.