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

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.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.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).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.