Factors that influence blood loss and need for transfusion following total knee arthroplasty.

Background: Blood loss during total knee arthroplasty (TKA) remains a concern, as many patients require blood transfusions, which increase risks of allergic reactions, disease transmission, and thromboembolisms. The purpose was to determine factors associated with blood loss and need for transfusion in patients receiving routine TKA.

Methods: The authors prospectively analyzed 150 consecutive uncemented TKAs for age, gender, body mass index (BMI), anticoagulant medication, type of anesthesia, tranexamic acid (TXA) administration, tourniquet inflation, drain placement, pre- and post-operative Haemoglobin (Hb) level (g/dL), and whether transfusion was necessary. Univariable and multivariable regression analyses were performed to identify factors associated with Hb loss and need for transfusion with significance level set at P value<0.05.

Results: The cohort comprised 92 women and 58 men, aged 69.5±8.9 years. The mean Hb loss was 3.7±1.3 g/dL. The 20 patients (13%) who had transfusions also had lower preoperative Hb (12.6±1.2 g/dL) compared to the remaining patients (14.3±1.2 g/dL). Hb loss was significantly associated with preoperative Hb, TXA, and gender, but multivariable regression identified gender as a confounder and indicated that TXA reduced Hb loss by 0.92 g/dL. Multivariable regression revealed the need for transfusion was only significantly associated with preoperative Hb and indicated that a decrease of preoperative Hb by 1 g/dL nearly quadrupled the chances of needing transfusion.

Conclusions: Hb loss was significantly associated with preoperative Hb levels and use of TXA, while the need for transfusion was only associated with preoperative Hb levels. These findings could help identify patients at risk for blood transfusions. Level of evidence: level III, prospective case series.