Children undergoing high-risk cardiac surgery face significant postoperative morbidity and mortality risk, and early recognition of impaired systemic perfusion is critical. Current monitoring modalities, such as lactate, central venous oxygen saturation, and near-infrared spectroscopy, are indirect surrogates of cardiac output and are either invasive or have limited predictive value. Perfusion index (PI) is a continuous, noninvasive measure derived from pulse oximetry that has shown promise in adult critical care but remains underexplored in pediatric cardiac surgery. We sought to determine whether postoperative PI is associated with morbidity and mortality in this high-risk population.

We conducted a retrospective cohort study of children (age 0-18 years) who underwent STAT 4-5 surgery between 2021 and 2024. High-resolution PI data from the first 24 postoperative hours were analyzed. Multivariable logistic regression was used to determine associations with mortality and secondary outcomes.

Of the 223 patients in our cohort, 33 (14.8%) died before discharge and demonstrated significantly lower PI values across all time points. Higher median PI during the first 6 postoperative hours was associated with reduced mortality (adjusted odds ratio [aOR], 0.49; P = .042). An abnormal PI (<0.7) in the first 6 postoperative hours was associated with a 3-fold increase in mortality risk (aOR, 3.7; P = .004). Higher median PI over the first 6 hours also was linked to lower odds of dialysis, extracorporeal membrane oxygenation, or low cardiac output syndrome, as well as shorter intensive care unit and hospital stays.

PI may be a useful early biomarker of adverse outcomes after high-risk pediatric cardiac surgery. Its continuous, noninvasive nature offers practical advantages over traditional measures and is complementary to other indirect measures. Multicenter prospective studies are needed.