Hemolysis and red blood cell mechanical fragility in shed blood after total knee arthroplasty

BACKGROUND: There are several options for the salvage of postoperative shed red blood cells (RBCs). This study compared the characteristics of the returned RBCs collected using two different devices: one that washes and one that does not wash the collected RBCs. STUDY DESIGN AND METHODS: Forty patients undergoing first-time total knee arthroplasty consented to participate. Twenty patients were operated on by a surgeon who routinely uses a device that does not wash the shed RBCs (unwashed group), the other 20 patients were operated on by surgeons who routinely use a device that washes and concentrates the collected RBCs (washed group). A small quantity of post-processing RBCs were collected immediately before reinfusion and the amount of plasma-free hemoglobin (PFHb), and the mechanical fragility index (MFI) of the returned RBCs were determined. RESULTS: The patients in both groups were well matched for age, sex, and length of stay. The mean percent hemolysis of the returned RBCs was not different between the unwashed and washed groups (1.22 +/- 0.30 vs. 1.24 +/- 0.42, p = 0.895), while the mean total amount of returned PFHb was not different (0.51 +/- 0.12 g vs. 0.55 +/- 0.35 g, p < 0.615). The ratio of total PFHb: total returned Hb was significantly lower for the washed group (0.0087 +/- 0.0023 vs. 0.0035 +/- 0.0011, p < 0.0001). The MFI was higher in the washed group (1.71 +/- 0.55 vs. 0.53 +/- 0.42, p < 0.001). CONCLUSIONS: The washing device returned more Hb to the patients relative to the amount of free Hb.