Impact of body mass index on hemoglobin level and blood transfusion in total knee arthroplasty: A retrospective case control study

BACKGROUND: Morbid obesity is a challenge in cases that require total knee arthroplasty, and several studies considered it a contraindication for the procedure due to associated risk of complications, including plummeting hemoglobin levels and subsequent need for a blood transfusion. This study investigated risk factors for blood transfusion in this patient group and considered their relationship to obesity. MATERIALS AND METHODS: Patients’ data were extracted from medical records, including estimated blood loss and perioperative hemoglobin levels. Patients were weighed and measured, and their body mass index (BMI) was calculated and stratified according to international criteria. RESULTS: A total of 188 patients were included in this study; among them, 136 patients had obesity (72%), with a mean BMI of 33.54. The mean volume of blood lost was 1055.4 ml, with the mean postoperative hemoglobin decrease of 1.42 g/dl and 2.88 g/dl at 6 and 24 h after surgery, respectively. The pre-operative Hb level was the only significant risk factor for blood transfusion. BMI did not affect the risk of blood transfusion or amount of blood lost. CONCLUSION: Obesity (BMI > 30 kg/m(2)) did not increase the risk of needing a blood transfusion after total knee arthroplasty. A judicious transfusion strategy involving the pre-operative Hb optimization should be adopted in TKA to decrease transfusion rate, benefit patient outcomes, and increase healthcare system efficiency. This study shows that high BMI is not a risk factor for postoperative blood transfusion.