Probiotics in pediatric cardiac surgery: biological effects and clinical outcomes – a systematic review of randomized evidence

Children undergoing cardiac surgery with cardiopulmonary bypass (CPB) are vulnerable to intestinal barrier dysfunction, systemic inflammation, and postoperative infection. Probiotics may restore gut microbiota balance and modulate inflammation, but evidence in pediatric cardiac populations is limited. The objective is to systematically analyze the effects of perioperative probiotic supplementation in pediatric cardiac surgery, and incorporating indirect evidence from adult CPB trials. Following PRISMA 2020 guidelines, major databases (PubMed, Embase, Scopus, CENTRAL, and ClinicalTrials.gov) were searched through March 2025. Eligible studies were randomized controlled trial (RCTs) and pilot studies that evaluated the probiotics in pediatric or adult cardiac-surgery patients. Data extraction and risk-of-bias assessment (RoB2) were performed independently by three reviewers. Owing to clinical heterogeneity and sparse events, findings were narratively synthesized, with quantitative pooling limited to comparable continuous outcomes. Five RCTs (three pediatric, two adult) met the inclusion criteria. Pediatric trials using Bifidobacterium breve or Bifidobacterium longum demonstrated improved intestinal microbiota and trends toward reduced endotoxin and I-FABP levels, but no significant differences in infection or ICU length of stay. Adult CPB trials showed reduced acute gastrointestinal injury and nosocomial infections. No adverse events or probiotic-associated sepsis were reported. Overall certainty of evidence ranged from low to moderate, limited by sample size and outcome heterogeneity. Perioperative probiotic supplementation in pediatric cardiac surgery appears safe and biologically active but lacks conclusive evidence for clinical benefit. Larger, standardized multicenter RCTs are warranted to determine efficacy and optimize strain selection, dosing, and timing.