Changes of perioperative hemoglobin and hematocrit levels in patients receiving total knee arthroplasty, a prospective observational study for an optimal timing of determination

Abstract

Background Total knee arthroplasty (TKA) has long been associated with significant blood loss, hence postoperative hemoglobin (Hb) and hematocrit (Hct) determination remains necessary for evaluating blood loss and guiding transfusions. The aim of the study was to depict the changing patterns of perioperative Hb and Hct levels and to identify an optimal timing of determination in patients receiving TKA surgeries. Methods This was a prospective observational study by recruiting a total of 302 consecutive patients who received TKA surgeryfor final analysisfrom January 2017 until December 2018. Patients were kept in hospital for a full week postoperatively to detect a preoperative, postoperative day1 through to day7 Hb and Hct concentrations, postoperative 1-month, 3-months and 6-monthsvalues were followed up in the clinic visiting. Results Hb and Hct levels decreased in the first few days and reached a nadir on postoperative day4 and day3 respectively while recovered in the following days and approached to preoperative values at postoperative 3-months. The mean maximum drop of Hb and Hct concentrations was detected as 4.0g/dL and 11.5%separately. Significant differences were detected on Hb and Hct concentrations between the timing neighbors on preoperative vs. day1, day1 vs. day2, day2 vs. day3, day7 vs. 1 month, 1-monthvs. 3-months and Hct values at 3-months vs. 6-months. A total of 21 patients received blood transfusion perioperatively, among whom 4 patients were at postoperative day3and 5 patients were at day4. Conclusion Hb and Hct concentrations dramatically decreased during the first few days following TKA surgery whilegradually recovered from postoperative day4 and approached to the preoperative values at 3-months postoperatively. The changing patterns indicated an optimal timing of blood determination on postoperative day3 or day4 to accurately reflect ongoing hidden blood loss for better guiding blood transfusions.