Time-related changes of collected shed blood in autologous retransfusion after total knee arthroplasty

A prospective study was done to determine the changes in blood quality parameters of collected drainage blood in retransfusion systems at 6 and 12 h after surgery to verify whether the blood was still suitable for retransfusion purposes for an additional 6 postoperative hours beyond the so far accepted first 6-h time window after surgery. Eighty-one patients received retransfusion within the first 6 h immediately following total knee arthroplasty. Additionally, drainage blood was collected for another 6 h using the same retransfusion system. Samples for laboratory analysis were taken from both the first and second 6-h blood collection interval. Hemoglobin values increased from 9.6 to 10.4 g dl^–1 (p = 0.021). Platelet counts increased from 65,500 to 80,900 μl^–1 (p < 0.001). Leukocyte counts increased from 5,550 to 8,190 l^–1 (p < 0.001). Lactate dehydrogenase (672 U l^–1 during the first vs 651 U l^–1 during the second collection period) and free hemoglobin (71.7 mg dl^–1 vs 67.0 mg dl^–1) did not change significantly. The potassium concentration decreased slightly from 4.33 to 4.20 mg dl^–1 (p = 0.002). The lactate concentration increased from 4.44 to 7.21 mg dl^–1 (p < 0.001). The pH decreased from 7.07 to 6.94 (p < 0.001). Interleukin-6 concentration increased from 6,500 to 46,500 ng l^–1 (p < 0.001). In this study, we found no relevant difference in most of the drainage blood quality parameters between the first 6-h collection period and the second 6-h collection with regard to its suitability for autologous retransfusion except higher interleukin-6 levels. Due to the higher interleukin concentration, a possible increase in febrile reactions should be taken into account during retransfusion.