Abstract
OBJECTIVE: To identify distinct postoperative temperature trajectories in neonates with congenital heart defects after cardiopulmonary bypass (CPB), using advanced unsupervised machine learning clustering methods, corroborate findings, and evaluate their prognostic value on outcomes. PATIENTS AND METHODS: A secondary cohort analysis of prospective data collected from a single pediatric referral center's CardioAccess data registry, consistent of neonates who underwent CPB between January 1, 2015, and January 1, 2019, was performed. Postoperative temperatures were extracted from medical records (48 hours). Group-based trajectory modeling (GBTM) performance was compared with self-organizing maps (SOM) and k-means clustering. Cluster membership and model fit were optimized for 3 temperature clusters per method. The primary outcome was a composite of postoperative complications. Clustering techniques were compared and associated with outcomes using adjusted multivariable binary logistic regression. RESULTS: Neonates of ≥34 weeks' gestation underwent CPB (N=450). GBTM, SOM, and k-means identified membership for 3 groups: (1) persistent hypothermia (n=38 [9%]; n=49 [11%]; and n=40 [9%], respectively); (2) resolving hypothermia (n=233 [51%]; n=227 [50%]; and n=147 [33%], respectively); and (3) normothermia (n=179 [40%]; n=174 [39%]; and n=263 [58%], respectively). Concordance between techniques found strong agreement between GBTM and SOM (κ=0.92) and weak agreement between GBTM and k-means (κ=0.41). After adjustment, persistently hypothermic neonates compared with normothermic neonates were associated with higher odds of the complication composite outcome in the GBTM (odds ratio [OR], 2.8; 95% CI, 1.0-7.3; P=.04) and SOM (OR, 2.3; 95% CI, 1.0-5.4; P=.04) models, but not in the k-means model (OR, 1.4; 95% CI, 0.7-3.1; P=.38). CONCLUSION: Exploring concordance between different machine learning techniques shows that temperature in neonates after CPB follows unique trajectories. Those exhibiting persistent hypothermia trends are at higher risk of adverse outcomes.