Red blood cells are damaged by intraoperative blood salvage via Ca-dependent and -independent mechanisms.

Aims: Intraoperative blood salvage (IBS) is associated with shortened lifespan of red blood cells (RBCs). This study aims to examine how salvaged RBCs are compromised during IBS.

Main Methods: Thirty patients who underwent vertebra surgery with IBS were included in the study. To examine possible mechanisms of IBS-induced injury, both fresh and salvaged RBCs from each patient were mixed with plasma, the Ca ionophore ionomycin or mannitol-adenine-phosphate (MAP) solution (n = 10 patients per condition). Binding of Fluo-3 and/or Annexin V by RBCs was measured.

Key Findings: The percentage of Fluo-3-binding RBCs in salvaged samples was 2.83 ± 0.76%, which increased to 15.34 ± 5.99% after 48-h incubation in plasma. These percentages were significantly higher than those observed with fresh RBCs (P < 0.01). Ionomycin dose-dependently increased the percentage of Fluo-3-binding RBCs in salvaged samples, while MAP solution decreased it. Incubating salvaged RBCs in plasma for 48 h increased the percentage of Fluo-3-positive spherocytes from 0.8 ± 0.6% to 11.35 ± 3.96%, and this increase was blocked by MAP solution. Ionomycin increased the percentage of RBCs binding both Fluo-3 and Annexin V, while MAP decreased this percentage. The percentage of Annexin V-binding RBCs was also higher in salvaged samples than in fresh samples, but this percentage was unaffected by either ionomycin or MAP solution.

Significance: Our results suggest that IBS induces a postponed RBC damage by inducing spherocyte formation, which likely reflects Ca entry induced by energy exhaustion, as well as by exposing phosphatidylserine on the RBC surface, which likely occurs via Ca entry and via Ca-independent pathways.