What Are We Transfusing? Preliminary Results of a Prospective Trial Evaluating the Quality of Intraoperatively Salvaged Red Blood Cells in Spinal Deformity Surgery

Introduction: Intraoperative red blood cell (RBC) salvage (aka Cell Saver) is widely employed in spinal deformity surgery. Unlike other surgical subspecialities wherein blood is immediately salvaged (with low potential RBC injury), modern approaches to spine surgery inherently result in collection of blood exposed to high-heat electrocautery, prolonged stasis, and abrasive pharmaceuticals, potentially resulting in RBC injury. However, this has not been studied in a scientific manner. We present preliminary results of an ongoing prospective study defining the quality of RBC salvage in spinal deformity surgery.

Methods: Patients undergoing spinal deformity surgery with Cell Saver were prospectively enrolled (N = 35). Comparison blood samples include baseline (arterial-line), allogenic (blood bank), and salvage (Cell Saver transfusate). Qualitative laboratory measures of RBC health and cell lysis were collected. Morphological assessment utilized Stimulated Raman Histology (SRH) and artificial intelligence based machine-learning algorithm.

Results: Salvage blood differed significantly from baseline and allogenic blood, including an unpredictable range of RBC density (2.11-9.52 x1000/uL), and significantly lower MCV (smaller RBCs) vs. baseline and allogenic samples (p = 0.015 and 4.05E-8, respectively). SRH revealed a high proportion (30.7%) of often irreversibly injured acanthocytes (shrunken and irregularly spiculated RBCs). Salvage blood samples had significantly higher intracellular components indicating active lysis: potassium (p = 0.019 and 8.2E-16), LDH (p = 3.3E-11 and 1.66E-6), and free-hemoglobin (p = 4.87E-7 and 0.001). The salvage blood mean hemolysis index (HI) was significantly higher than baseline (155x, p = 1.1E-10) and allogenic blood (7.23x, p = 2.29E-5).

Conclusion : Intraoperative salvaged blood is composed of high proportions of irreversibly injured RBCs with HI even exceeding levels suitable for transfusion by US FDA and Council of Europe standards, properties that may decrease the suitability of salvaged RBCs as a blood replacement. Collection of postoperative laboratory data, perioperative outcomes, and ex-vivo mechanical fragility and rheological profiles are currently underway.