Impact of pre-operative anemia on outcomes following posterior spinal fusion for adolescent idiopathic scoliosis

Objective: The aim of this study was to investigate the relationship of pre-operative anemia and outcomes following 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 (NSQIP-P) database from 2016 through 2018. All pediatric patients (age 10-18 years) with AIS undergoing PSF were identified. Two cohorts were categorized into Anemic and Non-Anemic cohorts based on age- and sex-based criteria for anemia. 30-day outcomes and readmission rates were evaluated.

Results: A total of 4,929 patients were identified, of which 592(12.0%) were found to have preoperative anemia. The Anemic cohort had a greater prevalence of comorbidities and longer operative times. Compared to the Non-Anemic cohort, the Anemic cohort experienced significantly higher rates of perioperative bleed/transfusion (Non-Anemic:67.4% vs. Anemic:73.5%, p=0.004) and required greater total amount of blood transfused (Non-Anemic: 283.2±265.5 mL vs. Anemic: 386.7±342.6 mL, p<0.001). The Anemic cohort experienced significantly longer hospital stays (Non-Anemic: 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 [OR:1.36,95% CI:(1.12, 1.66),p=0.002] as well as a longer LOS [RR:0.46, 95%CI:(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 greater perioperative bleed/transfusion event a slightly longer length of stay, however, not associated with greater 30-day complication and readmission rates in AIS patients undergoing PSF.

Keywords: Adolescent idiopathic scoliosis; Posterior spinal fusion; Pre-operative anemia.