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

Abstract

INTRODUCTION: Intraoperative 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. METHODS: Patients undergoing spinal deformity surgery with Cell Saver were prospectively enrolled (N = 86). Comparison blood samples include baseline (arterial-line), allogenic (blood bank), and salvage (Cell Saver transfusate). Qualitative laboratory measures of RBC health and hemolysis were collected. Morphological assessment utilized Stimulated Raman Histology (SRH) and artificial intelligence based machine-learning algorithm. Functional RBC evaluation was measured via ektacytometry. RESULTS: Salvage blood differed significantly from baseline and allogenic blood, including an unpredictable range of RBC density (2.11-9.52 x 1000/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). Ektacytometry revealed that salvaged RBCs were poorly deformable and had impaired relaxation kinetics. 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). CONCLUSIONS: 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 and perioperative outcomes are currently underway.