Supplementary Material for: Effects of milrinone on neonates after patent ductus arteriosus ligation: A retrospective nationwide database study

Introduction: Milrinone is administered after patent ductus arteriosus (PDA) ligation to prevent and treat postoperative hemodynamic instability (ie, postligation cardiac syndrome). We aimed to explore the effectiveness of milrinone on in-hospital outcomes in infants who underwent PDA ligation using a nationwide inpatient database in Japan. Methods: Using the Japanese Diagnosis Procedure Combination database, we identified patients who received milrinone after PDA ligation (n=428) in neonatal intensive care units between July 2010 and March 2021, and those who did not (n=3 392). We conducted a 1:4 propensity score-matched analysis with adjustment for background characteristics (eg, gestational age, birth weight, comorbidities, preoperative treatments, and hospital background) to compare morbidities (bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis, and retinopathy of prematurity), mortality, total hospitalization costs, and other outcomes. For sensitivity analysis, we performed an overlap propensity score-weighted analysis. Results: In-hospital morbidity, bronchopulmonary dysplasia, intraventricular hemorrhage, and necrotizing enterocolitis occurred in 58%, 48%, 9.5%, and 7.1% of patients, respectively; the in-hospital mortality was 5.4%. After 1:4 propensity score matching, no significant difference was observed regarding mortality (7.1% vs 5.7%), in-hospital morbidity (55% vs 50%), bronchopulmonary dysplasia (44% vs 41%), intraventricular hemorrhage (7.8% vs. 9.1%), necrotizing enterocolitis (8.5% vs. 8.9%), retinopathy of prematurity (21% vs. 22%), or total hospitalization costs (median: approximately 86 000 vs. 82 000 US dollars) between milrinone users (n=425) and nonusers (n=1 698). Sensitivity analyses yielded consistent results. Conclusions: Milrinone use after PDA ligation was not associated with improved in-hospital outcomes, such as mortality and morbidity