The relationship between hematocrit, blood lost, and blood transfused in total knee replacement. Implications for postoperative blood salvage and reinfusion.

The relationship between patient hematocrit level, red blood cell volume lost, and blood units transfused is important in determining conservation strategies in patients undergoing total knee replacement surgery. In a series of 30 such patients, 3 (10%) received allogeneic blood, despite preoperative autologous blood donation in 28 patients. There was no evidence that the degree of anemia affected rate or volume of postoperative wound blood drainage. The wound drainage volume that could have been salvaged and reinfused in bilateral procedures was substantial. A combination of one or more conservation techniques along with conservative transfusion practice is necessary to achieve minimal allogeneic blood exposure.