There is no consensus on the optimum timing of administration of tranexamic acid (TA) in bilateral total knee arthroplasty (TKA). We aimed to determine whether the timing of administration of single-dose intravenous TA (either given preoperatively or intraoperatively) has a significant effect on blood loss reduction.
We compared two cohorts of patients with end-stage arthritis of knees who underwent bilateral TKA and were given single-dose intravenous TA (1 g or 15 mg/kg) at different times during surgery. The retrospective cohort group consisting of 40 patients (preoperative (PO) group) received TA before the skin incision. The prospective cohort consisting of 40 patients (intraoperative (IO) group) received TA 10 min before deflating the tourniquet on the first knee. Primary outcome measures were mean hemoglobin difference, A (between PO and day 1 postoperative hemoglobin), mean hemoglobin difference, B (between PO and lowest postoperative hemoglobin), and rate of allogeneic blood transfusion. Secondary measure was drain blood loss.
Both cohorts were well matched with respect to age, gender, duration of surgery, and length of hospital stay. The hemoglobin drop in the IO group was significantly lesser than the PO group on the first postoperative day (2 vs. 2.9 g/dL, 
Single-dose intravenous TA given before the start of surgery is as effective as a dose given during arthroplasty of the first knee in reducing blood loss in bilateral TKA.