Dissociation between early metabolic acidosis and structural brain injury in neonates with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia.

ObjectiveTo evaluate the association between admission blood gas parameters, particularly pH and base excess (BE), and serial amplitude-integrated electroencephalography (aEEG) background patterns, and to determine whether these early metabolic markers are associated with MRI-defined brain injury severity in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH).MethodsThis retrospective study included 80 neonates (gestational age ≥35 weeks) with moderate-to-severe HIE treated with TH. Admission pH and BE values were recorded. Serial aEEG monitoring was performed at 6, 24, 48, and 72 h of life, and background patterns were classified according to Hellström-Westas criteria. aEEG recordings were independently interpreted by two reviewers blinded to the clinical and MRI data. Brain MRI was performed in 74 neonates at a median postnatal age of 5 days and was evaluated by a blinded pediatric neuroradiologist.ResultsAdmission BE was significantly associated with aEEG background patterns at all evaluated time points (6 h: p = 0.001; 24 h: p = 0.003; 48 h: p = 0.034; 72 h: p = 0.005). Infants with more severely depressed aEEG patterns had more negative admission BE values. In contrast, neither admission pH nor BE was significantly associated with MRI-defined brain injury severity. Overall mortality was 7.5%.ConclusionAdmission metabolic derangement, particularly BE, is associated with early electrocortical depression on serial aEEG but not with MRI-defined structural brain injury severity in neonates with HIE treated with TH. These findings support a dissociation between early metabolic acidosis and established structural brain injury and underscore the importance of multimodal prognostic assessment in early clinical decision-making.