BackgroundPre-operative anemia is known to be associated with perioperative complications in many surgical interventions. Here, we examine the effects of pre-operative anemia on peri-operative complications and post-operative outcomes in pediatric patients undergoing spinal fusion. MethodsRetrospective analysis was conducted using the American College of Surgeons Pediatric National Surgery Quality Improvement Program Database between 2012-2020. Current Procedural Terminology codes 22800, 22802, 22804, 22840, 22842, 22843, and 22844 were included to represent all primary spinal fusion procedures performed. Patients without pre-operative hematocrit (HCT) levels were excluded. Classification of anemia was determined via age- and sex-adjusted HCT levels. Patient demographics, pre-operative comorbidities and risk factors, and 30-day post-operative outcomes were compared between the two cohorts using univariate analysis. Multivariate logistic regressions were performed to determine if anemia severity was independently associated with worse post-operative outcomes. ResultsA total of 30,243 pediatric patients were included in this study, with 26,621 not having pre-operative anemia and 3,622 having pre-operative anemia. Pediatric patients with anemia have increased length of stay (6.7 ± 9.6 vs. 5 ± 6, P < 0.001), 30-day unplanned reoperation rate (4% vs 2.8%, P <0.001), and total blood transfused (489.9 ± 497.8 vs. 423.4 ± 452.6, P <0.001). Multivariate analysis supported anemia and degree of its severity as an independent predictor of increased length of stay, reoperation rate, and post-operative complications. ConclusionPreoperative anemia leads to worse outcomes in pediatric spinal fusion procedures. Utilizing HCT recordings could be factored into the equation for optimal patient selection and prevention of post-operative complications.