Is 30% oxygen adequate to start preterm resuscitation in an asphyxiated, bradycardic ovine model?

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ESPR228
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Abstract: :

Background: Current resuscitation guidelines for preterm infants needing respiratory support recommend beginning with 21-30% oxygen. A recent meta-analysis showed that preterm neonates, who do not achieve a heart rate (HR) of ≥100 bpm and peripheral oxygen saturation (SpO2) of ≥ 80% by 5 min, are at an increased risk of mortality and morbidity. 


Objective: To evaluate if initiation of resuscitation with 30% O2 followed by titration based on SpO2 in preterm surfactant deficient lambs with mild (HR 60-90 bpm) and severe (HR<60 bpm) bradycardia, can achieve HR≥100 bpm and SpO2 ≥ 80% by 5 min.


Methods: Preterm lambs (126-128d) with asphyxia induced by umbilical cord occlusion to achieve mild or severe bradycardia were used. A) Mild bradycardia requiring ventilation (PPV) alone: the umbilical cord was occluded until the lambs reached HR 60-90 bpm and ventilated with an initial supplemental O2 of 30% & the O2 was titrated every min until a composite outcome of HR ≥ 100 bpm & SpO2 of ≥ 80% was achieved. B) Severe bradycardia requiring PPV and chest compressions(CC): the cord was occluded until HR was <60 bpm and ventilated with an initial O2 of 30%. After 30s of PPV, CC was performed along with PPV in the ratio of 3:1 with 100% supplemental O2, until a HR of >60 bpm. PPV with 100% O2 was continued until a composite primary outcome of HR ≥ 100 bpm & SpO2 of ≥ 80% was achieved. Time taken to achieve the primary outcome was recorded. Gas exchange and hemodynamics were assessed.


Results: Characteristics of the asphyxiated lambs a) with HR <90 bpm(N=6) and b) HR <60 bpm(N=5) are shown in table 1. In both groups, 100% of the preterm lambs did not achieve the primary outcome by 5 min. The primary composite outcome was significantly shorter in preterm lambs with HR <90 bpm compared to those resuscitated with a HR <60 bpm (7±1 min vs.10±2 min, p-0.007, figure 1). Supplemental O2 use to achieve a HR of ≥ 100 bpm was 83±18 % when initial HR was <90 bpm & 100±0 % when initial HR was <60 bpm. To achieve a HR of 100 bpm & SpO2 of 80%, 100% O2 was required in both groups. The arterial oxygenation (PaO2) and peak pulmonary flow (PBF) were significantly higher than the baseline values in both groups when the composite outcome was achieved (figure 2). The peak PBF was 2-fold significantly higher compared to baseline when assessed at the primary composite outcome (HR ≥ 100 bpm & SpO2 ≥ 80 %) in both groups. The peak carotid flow (CBF) did not increase significantly at primary composite outcome compared to baseline in both groups (figure 3).


Conclusion: In asphyxiated preterm lambs, 100% supplemental O2 was needed to achieve a HR of ≥ 100 bpm & SpO2 ≥ 80% regardless of the extent of resuscitation. Despite ventilation with 100% O, the pulmonary vascular transition was suboptimal for surfactant deficient preterm newborn transition. Our findings suggest that a depressed preterm neonate be resuscitated with 100% initial O2. Clinical studies are needed to validate our findings.

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University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo
University at Buffalo

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