Can knee position save blood following total knee replacement?

Previous research showed knee flexion at 70 degrees for 6 h following total knee replacements (TKR) reduced wound drainage by 30%. However, wound drainage may not represent total blood loss and obstruction of the drain in flexion or the relative elevation of the knee could have caused the reduction in drainage. We wished to confirm that this simple, cheap method not only reduced wound drainage but also total haemoglobin loss and determine what part elevation or drain obstruction may play. Sixty consecutive TKR patients were randomly allocated to three groups. Group 1-knee extended and level with bed. Group 2-leg elevated 35 degrees at the hip with knee flexed to 70 degrees for 6 h post-operatively. Group 3-leg elevated 35 degrees at the hip with knee extended for 6 h post-operatively. We assessed wound drainage over 48 h, calculated haemoglobin loss, total blood transfusion, pain, arc of motion, swelling, length of hospital stay and complications. We found knee flexion and knee elevation in extension reduced haemoglobin loss by 25%. Compromise to tissue oxygenation has been reported with knee flexion. We recommend elevation of the leg at 35 degrees from the hip with the knee extended. This offers a simple, safe and effective way to reduce total blood loss by 25%.