Impact of Preoperative Anemia on Outcomes After Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Objective: The aim of this study was to investigate the relationship of preoperative anemia and outcomes after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Methods: A retrospective cohort study was performed using the American College of Surgeons National Surgical Quality Improvement Program–Pediatric database from 2016 to 2018. All pediatric patients (age 10–18 years) with AIS undergoing PSF were identified. Two cohorts were categorized into anemic and nonanemic cohorts based on age-based and sex-based criteria for anemia. Thirty-day outcomes and readmission rates were evaluated. Results: A total of 4929 patients were identified, of whom 592 (12.0%) were found to have preoperative anemia. The anemic cohort had a greater prevalence of comorbidities and longer operative times. Compared with the nonanemic cohort, the anemic cohort experienced significantly higher rates of perioperative bleed/transfusion (nonanemic, 67.4% vs. anemic, 73.5%; P = 0.004) and required a greater total amount of blood transfused (nonanemic, 283.2 ± 265.5 mL vs. anemic, 386.7 ± 342.6 mL; P < 0.001). The anemic cohort experienced significantly longer hospital stays (nonanemic, 3.8 ± 2.2 days vs. anemic, 4.2 ± 3.9 days; P = 0.001), yet discharge disposition (P = 0.58), 30-day complication rates (P = 0.79) and unplanned reoperation rates (P = 0.90) were similar between cohorts. On multivariate analysis, anemia was found to be an independent predictor of perioperative bleed/transfusion (odds ratio, 1.36; 95% confidence interval, 1.12–1.66; P = 0.002) as well as a longer length of hospital stay (relative risk, 0.46; 95% confidence interval, 0.25–0.67; P < 0.001) but was not an independent predictor for postoperative complications (P = 0.85). Conclusions: Our study suggests that preoperative anemia may be a risk factor for a greater perioperative bleed/transfusion event and slightly longer length of stay; however, it was not associated with greater 30-day complication and readmission rates in patients with AIS undergoing PSF.