24 - The Association of the Difference Between Pre- and Post-natal Blood Gas Values with Brain Injury following Neonatal Encephalopathy

Publication Number: 1021.24

Ceilidh Smith, Brigham and Women's Hospital, Boston, MA, United States; Mohamed El-Dib, Brigham and Women's Hospital / Harvard Medical School, Boston, MA, United States; Hoda El-Shibiny, Brigham's Women Hospital, Boston, MA, United States

Background: Early biomarkers of neonatal encephalopathy (NE) due to hypoxic-ischemic encephalopathy (HIE) are critical for timely assessment and determining the need for neuroprotective therapies such as therapeutic hypothermia (TH). Prior studies, including those from our group, have shown that measures of metabolic acidemia (pH, base deficit (BD), and lactate) in postnatal blood gases (BGs) correlated with the severity of precooling neurological examination scores. Although many clinicians interpret improvement in BG values from cord to postnatal samples as clinically meaningful, little is known about whether such differences relate to the extent of brain injury.

Objective: To evaluate blood gas differences as early indicators of brain injury.

Design/Methods: We conducted a retrospective single-center study of ninety infants treated with TH in the neonatal intensive care unit at Brigham and Women's Hospital between 2017 and 2021 (Table 1). All infants had documented pH values, while seven had missing BD data. For each infant, the differences between arterial umbilical cord blood (aUCG) and postnatal BG pH and BD were calculated and compared with the degree of brain injury on MRI using the Weeke MRI scoring system. We also examined associations between individual aUCG and postnatal values (pH and BD), as well as the NE examination score, with MRI injury scores.

Results: The difference between aUCG and postnatal pH showed a significant negative correlation with MRI Weeke scores (Spearman r = -0.33, p = 0.001), indicating that an increase in pH from cord to postnatal blood was associated with less severe brain injury. No significant correlations were observed for individual pH values (cord or postnatal) (Figure 1), differences in BD or individual BD values (Figure 2), and MRI injury scores. Also, no significant correlation was noted between NE score and MRI injury scores (Spearman r= -0.005, p=0.964 ).

Conclusion(s): Conclusion/Impact:
We report that the difference between pre-natal (cord) and post-natal pH values provides additional insight into the risk of brain injury on MRI beyond the use of either measure alone or the clinical examination. An improvement in pH after birth was associated with less severe MRI-detected brain injury, suggesting that changes in acid-base status during the early postnatal period may reflect evolving cerebral recovery or ongoing injury.
Future studies should evaluate the clinical utility of incorporating pre- to post-natal differences in blood gas values into decision-making algorithms for initiating or refining neuroprotective interventions, including TH and emerging adjunctive therapies.

Table 1. Baseline Characteristics of participants who received Therapeutic Hypothermia between 2017 and 2021.
Categorical and binary data presented as n (%). Continuous data as mean (±SD) or median (range).

Figure 1. Scatter plots showing the relation between pH difference (postnatal-aUCG) , aUCG pH, and post-natal pH and Weeke Scores.
A) Scatter plot showing the relation between pH difference (postnatal-aUCG) and Weeke score (Spearman r= -0.330* , p= 0.001)
B) Scatter plot the relation between aUCG pH and Weeke score (Spearman r= 0.260 , p= 0.013 )
C) Scatter plot the relation between postnatal pH and Weeke score (Spearman r= -0.173 , p= 0.102 )

*. Correlation is significant at the 0.01 level (2-tailed).

Figure 2 Scatter plots showing the relation between BD difference (postnatal-aUCG) , aUCG BD and post-natal BD and Weeke Scores.
A) Scatter plot showing the relation between base deficit difference (postnatal-aUCG) and Weeke score (Spearman r= -0.149 , p=0.185 )
B) Scatter plot showing the relation between aUCG base deficit and Weeke score (Spearman r= -.095 , p= 0.393 )
C) Scatter plot the relation between postnatal base deficit and Weeke score (Spearman r= 0.053 , p= 0.623 )