Natural course of hemoglobin level after total knee arthroplasty and the benefit of tranexamic acid injection in the joint.

We retrospectively investigated the natural course of hemoglobin (Hb) level after total knee arthroplasty (TKA) and identified the benefit of tranexamic acid injection at the operation field for unilateral TKA patients who have not received blood transfusions.There were 115 cases conducted by a surgeon who performed TKA without injecting tranexamic acid and 62 cases by another surgeon with injection. During 2-weeks of hospitalization, Hb level was checked on the day of surgery and 1, 2, 3, 5, 7, 11 days after surgery.Regardless of whether whom the operator was and tranexamic acid was injected or not, the same natural course of Hb level after TKA was observed. The lowest value of Hb was shown at postoperative day 3, after which it tended to recover. In repeated measures analysis of variance test, mean difference from preoperative Hb level showed a statistically significant difference between tranexamic acid injected and noninjected groups (P = .01). In post hoc test, the differences from preoperative Hb levels were significantly lower at all measurements in surgeon with injection of tranexamic acid.When deciding whether to transfuse after TKA, it should be noted that the patient tends to show the lowest Hb level on postoperative day 3. Also, the authors emphasize that tranexamic acid injection in the joint at the operation field is an effective method to reduce the loss of Hb after TKA.