Acute Postoperative Anemia After Unilateral Primary Total Joint Arthroplasty: Restrictive Transfusion Thresholds are Safe for Discharge Regardless of Delta Hemoglobin

Primary unilateral total joint arthroplasty (TJA) is associated with acute postoperative anemia that may require blood transfusion. Clinicians may worry about discharging patients after surgery who experience substantial decreases in hemoglobin (Hgb), even if their Hgb is above restrictive transfusion thresholds. The purpose of this study was to determine whether differences between preoperative and postoperative Hgb values (Delta) correlate with 90-day readmission in patients who did not receive perioperative transfusions.A retrospective review of patients undergoing primary unilateral TJA between 2015 and 2020 was performed. The primary outcome was whether a specific cutoff delta Hgb was predictive of readmission within 90 days due to anemia-related causes. Secondary outcomes included the presence of acute postoperative anemia and transfusion during readmission.Six thousand seven hundred and ninety one patients had a median delta Hgb of 2.80. In total, 268 patients (3.95%) were readmitted within 90 days postoperatively, with two patients requiring transfusion during readmission. A significantly higher rate of readmission was found in patients with cardiovascular disease (5.16% versus 3.68%; P = .020). When constructing receiver operating characteristic curves, a cutoff value of 3.20 resulted in an area under curve of 0.595 (0.486-0.704). In patients with cardiovascular disease, a cutoff value of 3.10 resulted in an area under curve of 0.626 (0.466-0.787).The magnitude of Hgb change was not predictive of anemia-related readmission within 90 days in patients who did not receive a perioperative transfusion. Patients experiencing higher delta Hgb values but remaining above the transfusion threshold may have a greater physiologic reserve.