272 - Early Oxygen Saturation Trajectories in Neonates with Complete-Mixing Congenital Heart Disease

Publication Number: 4268.272

Grace A. Hooker, University of Texas at Austin Dell Medical School, Austin, TX, United States; Juan Gallegos, Dell Children's Medical Center of Central Texas, Austin, TX, United States; Daniel Janes, University of Texas at Austin Dell Medical School, Austin, TX, United States; Alan Groves, University of Texas at Austin Dell Medical School, Austin, TX, United States

Background: Congenital heart disease (CHD) affects ~40,000 births annually in the USA. In healthy term infants, preductal oxygen (O2) saturations typically remain below 90% in the first 5 minutes of life. However, oxygenation trajectories in infants with CHD are less well-defined during transition and early neonatal life. Interpretation of oxygen saturation in CHD depends on cardiac anatomy and mixing physiology, yet clinicians often target saturations of 75-85% when pulmonary and systemic blood flows are balanced. Emerging data suggest saturation patterns differ by physiologic subtypes of CHD in the first 5 minutes of life, but little is known about the oxygen saturations trends beyond the delivery room.

Objective: To characterize early oxygen saturation trajectories in the first 7 days of life in neonates with complete-mixing CHD.

Design/Methods: We conducted a retrospective study of neonates with complete-mixing CHD admitted from January 2021 to September 2025. Included diagnoses were tricuspid atresia, pulmonary atresia, and truncus arteriosus. Infants born < 35 weeks' gestation, undergoing cardiac surgery within 7 days of life, admitted >24 hours postnatal age, or with aneuploidy were excluded. Continuous SpO2 data was extracted from the SickBay remote monitoring platform and median values summarized at prespecified timepoints (1-168 hours of life) using all valid readings within a ±1-hour window. Data was averaged across two cohorts: all eligible infants and a subset who stayed on room air, to generate oxygenation trajectories across the first week of life.

Results: A total of 49 infants ≥35 weeks' gestation with eligible cardiac lesions were born during the study period. After exclusions, 26 infants were included (mean GA 38+2 weeks, mean birthweight 3.14kg). 17 required supplemental O2 in the first week of life. In the full cohort, mean SpO2 rose from 87.7% at 1 hour to a peak of 92.0% at 48 hours, then declined to 87.8% by 168 hours (Figure 1). In the subset without oxygen supplementation, mean SpO2 increased from 88.7% at 1 hour to 92.8% at 60 hours and gradually decreased to 89.1% at 168 hours (Figure 2).

Conclusion(s): Neonates with complete-mixing CHD exhibit higher-than-expected oxygen saturations during the early neonatal period, with mean values exceeding the accepted 75-85% range. We hypothesize that these higher levels are due to fetal hemoglobin's higher O2 affinity. Our findings suggest that current oxygenation targets underestimate the expected range in these infants, potentially leaving infants undersupported when their oxygen saturations are below the true achievable range in the days after birth.

Table 1. Infant Characteristics


SpO2 Trends by Postnatal Age in Infants with Complete Mixing Heart Lesions
Figure 1. Plot of average oxygen saturation and SEM for all subjects (n = 26) during 1 hour window centered on predetermined time points.

SpO2 Trends by Postnatal Age in Infants with Complete Mixing Heart Lesions with No Oxygen Requirement
Figure 2. Plot of average oxygen saturation and SEM for subjects with no oxygen requirement (n = 11) during 1 hour window centered on predetermined time points.