Preoperative prognostic nutritional index and in-hospital mortality in neonates undergoing cardiac surgery for congenital heart disease: a single-center retrospective study.

BACKGROUND: Neonates undergoing cardiac surgery for congenital heart disease (CHD) represent one of the highest-risk subpopulations in pediatric cardiac surgery. Preoperative nutritional and immune reserve may substantially influence perioperative resilience, yet practical neonatal-specific nutritional risk markers remain insufficiently defined. OBJECTIVE: To evaluate the association between preoperative prognostic nutritional index (PNI) and in-hospital mortality in neonates undergoing cardiac surgery for CHD, and to explore a neonatal-specific cutoff value for early risk stratification. METHODS: This retrospective single-center cohort study included 433 neonates ( ≤ 28 days of postnatal age at surgery) who underwent primary cardiac surgery for CHD between January 2021 and December 2025. PNI was calculated from the final routine preoperative serum albumin (g/L) and total lymphocyte count ( × 109/L) obtained before the index surgery. The optimal cutoff value was derived using receiver operating characteristic analysis and the Youden index. Associations between PNI and in-hospital mortality were assessed using nested multivariable logistic regression models and generalized additive models. RESULTS: Overall in-hospital mortality was 3.70% (16/433), and mean PNI was 53.49 ± 13.05. Receiver operating characteristic analysis yielded an area under the curve of 0.661 (95% CI: 0.535-0.786; p = 0.020), with an optimal cutoff of PNI < 43.65, sensitivity of 56.3% (9/16), and specificity of 76.7% (320/417). Mortality was significantly higher in the low-PNI group than in the high-PNI group (9/106, 8.49% vs. 7/327, 2.14%; p = 0.007). In unadjusted analysis, low PNI was associated with higher in-hospital mortality (OR 3.85, 95% CI 1.08-14.29; p = 0.038). This association weakened after full adjustment (Model 3 OR 3.13, 95% CI 0.85-11.11; p = 0.086), likely reflecting limited event numbers and residual confounding. CONCLUSION: Lower preoperative PNI was associated with higher crude in-hospital mortality in neonates undergoing cardiac surgery for CHD. Because statistical independence was not retained in the fully adjusted model, PNI should be interpreted as an exploratory adjunctive screening marker rather than a stand-alone prognostic tool. Larger prospective multicenter studies are warranted to validate neonatal-specific thresholds and determine whether PNI-informed perioperative optimization can improve outcomes.