Increased Severity of Anemia Is Associated with Postoperative Complications following a Adult Spinal Deformity Surgery

Background: Anemia is a modifiable risk factor for postoperative complications following surgery. This study aimed to determine the impact of preoperative anemia severity on 30-day postoperative complications following adult spinal deformity (ASD) surgery. Methods: Adults undergoing spinal fusion for ASD from 2012 to 2018 were identified in the National Surgical Quality Improvement Program database. Patients were substratified into 3 cohorts–non-anemia, mild anemia, and moderate-to-severe anemia–based on World Health Organization definitions. We assessed 30-day wound, cardiac, pulmonary, renal, and thromboembolic complications, as well as sepsis, mortality, postoperative transfusions, extended length of stay, and reoperation. Bivariate analyses and multivariable logistic regression were performed. Results: Of 2173 patients, 1694 (78%) had no anemia, 307 (14%) had mild anemia, and 172 (8%) had moderate or severe anemia. Following adjustments, patients with mild anemia were more likely to have postoperative blood transfusions (odds ratio [OR] 1.80, P < 0.001) and extended length of stay (OR 1.43, P < 0.001). Patients with moderate-to-severe anemia were at increased risk of organ space infection (OR 3.27, P = 0.028), death (OR 13.15, P = 0.001), postoperative blood transfusion (OR 2.81, P < 0.001), and extended length of stay (OR 3.02, P < 0.001). Conclusions: We found a stepwise and approximately two-fold increase in the odds ratio of postoperative transfusion and length of stay with increasing severity of anemia. Moderate-to-severe anemia was associated with increased odds of death and organ space infection. Patients with moderate-to-severe anemia should be medically optimized before ASD surgery.