Neutrophil extracellular traps were released during intraoperative blood salvage in posterior lumbar surgery

The formation of neutrophil extracellular traps (NETs) has been associated with endothelial damage and severe pulmonary dysfunction. The present study aimed to investigate whether this NETosis occurs during intraoperative blood salvage (IBS), and whether the washing procedures before re-transfusion of autologous blood could remove the NET components, including DNA, histones, and myeloperoxidase. The study was performed using blood samples from 20 patients who underwent posterior lumbar surgery at the Beijing Friendship Hospital. The samples were obtained at three time points/sources: peripheral venous blood prior to surgery (baseline), cell salvage collection reservoir (reservoir), and filtered salvaged blood prior to re-transfusion (pre-transfusion); blood salvage was accomplished with a Cell Saver 5 system. The plasma was collected after centrifugation of the blood sample. Then the DNA amount was measured using SYTOX Green labeling; the integrity and length of the DNA were roughly evaluated by agarose gel electrophoresis; and the levels of nucleosomes (DNA and histones) and myeloperoxidase were detected using commercial ELISA kits. Extracellular DNA, nucleosomes, and myeloperoxidase were found higher in the reservoir samples and pre-transfusion samples, as compared to the baseline samples. The DNA was primarily non-fragmented with high molecular weight (>15 kb). And lower levels of these NET components were observed in pre-transfusion samples, compared with the reservoir samples. In conclusion, DNA, histones, and myeloperoxidase were released during IBS, indicating the NET formation by activated neutrophils. Pre-transfusion processing could reduce the NET components but the levels remained significantly elevated compared to the baseline.