Optimal 6-hour window for salvaged mediastinal blood retransfusion after cardiovascular surgery: an in vitro quality and safety analysis

Background – Postoperative hemorrhage is a significant complication of cardiovascular surgery. Although autologous cell salvage is safe and effective for preserving patients’ blood, its use in the postoperative context remains underexplored. We, therefore, evaluated the quality and safety of mediastinal blood collected for different periods at room temperature after cardiac surgery.

Materials and methods – In this preclinical, in vitro investigation, 60 patients who lost ≥500 mL mediastinal blood within 6 hours after cardiovascular surgery were randomized into three groups (6H, 8H, 12H) according to the time the shed mediastinal blood was processed. The quality of the salvaged blood was evaluated through measurements of hematocrit, pH, electrolyte and lactate levels, 2,3-diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP) content, and red blood cell (RBC) deformability and morphology. The safety evaluations included hemolysis, contamination, and levels of inflammatory cytokines.

Results – With regard to quality, the median [IQR] values for the 6H group were hematocrit 56.3 [46.5-59.0] %, pH 7.34 [7.31-7.40]), potassium 1.10 [0.91-1.25] mmol/L, lactate 0.45 [0.20-0.90] mmol/L, 2,3-DPG 12.00 [9.24-13.32] μmol/gHb), ATP 5.59 [5.27-5.93] μmol/gHb and deformability 0.88 [0.77-0.93]. The values were similar across the three groups, except for pH, which decreased over collection period. RBC morphology transitioned from biconcave in the 6H and 8H groups to spiny forms in the 12H group. Hemolysis and inflammatory cytokine levels were low in all groups. Only the 6H group achieved total microbial sterility, with 0% bacterial contamination, compared to 10% (No.=2) in the 8H group and 5% (No.=1) in the 12H group.

Discussion – Our study establishes a 6-hour window as the optimal period for ensuring microbial sterility and preserving the quality and safety of salvaged mediastinal blood postoperatively. Although blood quality remained stable for up to 12 hours, the heightened risk of contamination beyond 6 hours necessitates rigorous microbiological monitoring.