The Association Between Perioperative Allogeneic Transfusion Volume and Postoperative Infection in Patients Following Lumbar Spine Surgery

Infections following spinal surgical procedures impart an increased risk of postoperative patient morbidity and mortality. Surgical site infection is the most common nosocomial infection in the early postoperative period1. More importantly, 77% of acute mortality in patients with surgical site infection is directly related to the infection2. The consequences of postoperative infection include loss of instrumentation fixation, pseudarthrosis, osteomyelitis, chronic pain, sepsis, and death3-6. In addition, the economic implications of infection following spinal surgery cannot be overstated. Patients who develop surgical site infection usually require longer postoperative hospitalization, are more likely to be managed in intensive care units, and have higher hospital readmission rates7. The incidence of surgical site infection following spinal procedures is influenced by a multitude of intrinsic and extrinsic factors. Patient-specific factors identified as increasing the risk for surgical site infection include advanced age6,8,9, corticosteroid use10,11, smoking6,12,13, alcohol abuse6, and diabetes6,10,13,14. Olsen et al. performed a large retrospective case control study in which diabetes was the greatest independent risk factor for spinal surgical site infection15. Schwarzkopf et al. found body mass index (BMI) to significantly influence the risk of surgical site infection following thoracic and lumbar spine surgery16. Intraoperative risk factors identified include the type of surgical approach, the procedure performed, revision procedures, and the length of the surgery6,14. A point of contention in the literature and among surgeons is the relationship between allogeneic perioperative blood product transfusion and morbidity. The rationale for aggressive perioperative red blood cell transfusion following spine surgery has been established17. Additionally, postoperative anemia has been correlated with longer hospital admission and higher readmission rates in patients following open reduction and internal fixation of hip fractures18, although this has been questioned recently19. In the United States, 14 million units of blood are transfused annually and transfused blood is generally considered to be safe20. However, allogeneic transfusion does have some risks. The association between the development of surgical site infection and transfusion has been reported in the literature21-24. The immunomodulatory effects imparted by allogeneic transfusion are not completely understood. Allogeneic transfusion has been linked not only to an increased risk of nosocomial infection, but also to cancer recurrence and autoimmune diseases25-27. Although allogeneic red blood cell transfusion has been identified as a risk factor for the development of surgical site infection following spinal surgery16, we are unaware of any studies that have evaluated if the volume of transfusion given influences infection risk. The purpose of this study was to determine if there is an association between the volume of perioperative red blood cell transfusion and the risk of surgical site infection following lumbar spine procedures.