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

Abstract

Objective

To 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).

Methods

This 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.

Results

Admission 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%.

Conclusion

Admission 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.