Ultrasound predictors of extubation outcomes in pediatric cardiac surgery: A prospective evaluation of lung, diaphragmatic, and cardiac ultrasound

Abstract

ABSTRACT Backgrounds: Extubation failure after pediatric cardiac surgery increases morbidity and intensive care unit (ICU) stay. Conventional indices such as rapid shallow breathing index (RSBI) and PaO2/FiO2 do not account for multi-organ contributors such as cardiac function, pulmonary aeration, and diaphragmatic performance. This study prospectively evaluated bedside ultrasound parameters – lung ultrasound score (LUS), mean diaphragmatic excursion (DE), and E/e′ ratio – as predictors of extubation outcomes. Methods: In this prospective, observational study conducted in a tertiary pediatric cardiac ICU, 102 postoperative children undergoing elective extubation were evaluated using ultrasound at three standardized timepoints (M1: SIMV mode, M2: CPAP/PS mode, and M3: NIV/room air). The primary outcome was extubation failure, defined as reintubation within 48 h. Diagnostic accuracy was analyzed using receiver operating characteristic curves and Youden index-derived thresholds. The secondary outcomes included associations with ventilation duration, ICU stay, incremental value over conventional indices (PaO2/FiO2 and RSBI), and timepoint dynamics. Results: Extubation failure occurred in 11 (10.8%) patients. In SIMV mode (M1), the optimal thresholds were LUS ≥12 (area under the curve [AUC] 0.69, sensitivity 63.6%, specificity 64.8%), mean DE ≤0.82 cm (AUC 0.45, specificity 89%), and E/e′ ≥8.9 (AUC 0.38). LUS ≥12 trended toward longer mechanical ventilation and ICU stay but did not reach statistical significance. Adding LUS to conventional indices showed a nonsignificant increase in discrimination from AUC 0.66 to 0.71 (P = 0.145). At later timepoints, LUS performance improved (AUC 0.72 at M3), while DE and E/e′ remained poor discriminators. Inter-observer reproducibility for DE was moderate (intra-class correlation coefficients 0.50–0.61). Conclusions: In pediatric cardiac surgical patients, LUS demonstrated a moderate predictive ability for extubation outcomes, whereas diaphragmatic and diastolic parameters were weak predictors. The addition of LUS to conventional indices provided incremental value, supporting its role as a useful bedside adjunct in evaluating extubation readiness.