Obesity does not increase blood loss or incidence of immediate postoperative complications during simultaneous total knee arthroplasty: A multicenter study.

The purpose of the study was to determine blood loss, transfusion risk, and incidence of immediate postoperative complications in normal, overweight, and I-II obese patients undergoing simultaneous bilateral total knee arthroplasty (SBTKA).

We identified 1070 SBTKA procedures, and separated the patients into three groups on the basis of body mass index (BMI), including normal (BMI: 18.0-24.9 kg/m²), overweight (BMI: 25.0-29.9 kg/m²), and obese groups (BMI: ≥30.0 kg/m²). The primary outcome was total blood loss and secondary outcomes were dominant and hidden blood loss, transfusion rate and volume, hemoglobin (Hb) and hematocrit drop and other complications.

Patient's blood volume increased gradually among normal, overweight, and obese groups. There was no significant difference in blood loss or incidence of complications among the three groups, while the transfusion rate in the normal group was higher than that in overweight (36.0% vs 27.6%, p = 0.007) and obese groups (36.0% vs 24.6%, p = 0.006). In addition, the independent risk factors for complications among all groups following SBTKA included lower level of preoperative Hb (p = 0.040), general anesthesia (p = 0.002), drain use (p = 0.005), and transfusion (p < 0.001).I-II obesity does not increase patient's blood loss, transfusion risk, or immediate postoperative complications following SBTKA. Obese and overweight patients may have lower transfusion needs compared with normal patients because of their higher basal blood volume. The risk factors for complications after SBTKA are lower level of preoperative Hb, general anesthesia, drain use and transfusion.