Which patients are more likely to benefit from postoperative shed blood salvage after unilateral total knee replacement? An analysis of 581 consecutive procedures.

INTRODUCTION: Requirements for allogeneic blood transfusion (ABT) after total knee replacement (TKR) are still high (30-50%), and salvage of unwashed filtered postoperative shed blood (USB) may represent an alternative to ABT. We evaluated that patients are more likely to benefit of USB reinfusion after TKR. PATIENTS AND METHODS: Data from 581 consecutive primary TKR, managed with (reinfusion group, n = 382) or without (control group, n= 199) reinfusion of USB, were retrospectively reviewed. RESULTS: Patients from reinfusion group received 119 +/- 88 ml of red blood cells from USB, without clinically relevant incidents, and showed a lower ABT rate (30.6% vs. 8.4%, for control and reinfusion groups, respectively; P = 0.001) (transfusion trigger, haemoglobin [Hb] < 9 g/dl). Differences in ABT rate between groups were significant for all preoperative Hb levels, except for Hb < or = 12 g/dl. A lower transfusion threshold (Hb < 8 g/dl) might have further decreased ABT rate (14.6% vs. 5.2%, respectively; P < 0.001), with differences being significant for preoperative Hb between 12 and 15 g/dl. There were no differences with respect to postoperative infection rate, but patients from reinfusion group had a shorter length of hospital stay (11 +/- 4 vs. 13 +/- 4 days, respectively; P= 0.001). CONCLUSIONS: Return of USB after TKR seems to reduce the need for ABT, especially in patients with preoperative Hb between 12 and 15 g/dl. There is little benefit of USB reinfusion for patients with preoperative Hb > 15 g/dl, whereas patients with preoperative Hb < 12 g/dl would probably benefit from the combination of USB with some other blood-saving method