Center Volume Not Associated with Survival Benefit of Inter-Hospital Transfer for Pediatric Cardiac Surgery

To evaluate the relationship between center volume and inpatient mortality among patients transferred to another hospital for pediatric cardiac surgery using contemporary real-world data. The Kids' Inpatient Database (KID) was queried for cardiopulmonary bypass (CPB) cases for the years 2016 and 2019. Hospitals were divided into three groups based on terciles of volume: low: ≤ 103 cases/year, mid: 104-194 cases/year, and high: > 194 cases/year. Multilevel regression models were created to evaluate the association between volume and inpatient mortality for transferred patients, both for the entire cohort and for high-complexity cases. (Risk Stratification for Congenital Heart Surgery (RACHS-2) categories 3,4, and 5). Of 25,749 patients undergoing cases on CPB, 3511 (13.6%) were preoperative inpatient transfers between hospitals. Compared to direct admissions, unadjusted mortality for patients who were transferred was higher in all groups: 1.7% vs 5.6% (low-volume), 1.1% vs 4.6% (mid-volume) and 1.1% vs 4.9% (high-volume). Compared to low-volume hospitals, inpatient mortality for patients admitted on transfer was not significantly different in mid-volume (OR = 0.85, 95% CI 0.54-1.34, p = 0.483) and high-volume centers (OR = 0.7, 95% CI 0.45-1.12, p = 0.127) for the entire cohort. There was no significant difference in risk-adjusted inpatient mortality for high-complexity cases performed at mid-volume (OR 1.06, p = 0.845, 95% CI (0.62-1.85)) or high-volume hospitals (OR 0.82, p = 0.482, 95% CI (0.48-1.45)) compared to low-volume hospitals. Annual CPB case volume may not accurately predict risk-adjusted inpatient mortality for children transferred for pediatric cardiac surgery. Annual case volume alone should not dictate transfer for surgical care.