Knee revision surgery is performed under a tourniquet, which means that the limb is exsanguinated and the tourniquet is placed over the thigh and is tightened till the end of the procedure. Most of the surgery is performed in a bloodless manner, however certain types of knee revision surgeries require that the procedure be done over several hours. In these type of surgeries, the tourniquet has to be let down, and although hemostasis is achieved, there may be blood loss intraoperatively which may need a blood transfusion.
For patients who undergo a spacer, the spacer is not strongly adherent to the bone because it’s an antibiotic spacer, and the idea is not to cement it to the bone because removing the spacer in the second stage will lead to more bone loss. Therefore, in patients who get a spacer, there is blood loss, not during the surgery but during the postoperative period. Patients who get a spacer after the removal of the knee joint do a transfusion on the second or the third day.