The physiological significance of targeting a heart rate of 100 bpm and saturation of 80% by 5 min during preterm resuscitation

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ESPR336
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Abstract: :

Background: Increasing heart rate (HR) is the most reliable sign of successful neonatal resuscitation. A meta-analysis involving 768 preterm infants from 8 randomized control trials have shown that not achieving a saturation (SpO2) of 80%, and a heart rate of >100 bpm by 5 min leads to higher mortality and intraventricular hemorrhage. The hemodynamic and physiological significance of this combined target is not known


Objective: To study the effect of gas exchange, pulmonary and cerebral hemodynamic parameters at a combined target of HR ≥ 100 bpm and SpO2  of ≥ 80% in an asphyxiated, bradycardic preterm lambs. 


Methods: Preterm lambs (126-128d gestation) with RDS were asphyxiated by umbilical cord occlusion until a HR <90 bpm. The resuscitation was initiated with 30% oxygen (O2), and ventilation (PPV) continued by titrating O2 every min based on target saturations. If the HR dropped to <60 bpm, chest compression (CC) and PPV with 100% was initiated along with epinephrine (EPI) administration as per NRP guidelines.  Blood gas and hemodynamic parameters were collected every minute and compared at (i) baseline, (ii) HR≥100 bpm alone, and (iii) HR≥100 bpm&SpO2≥80%. 


Results: Eleven preterm lambs were included in the study, and 5 required CC and EPI. In an asphyxiated preterm model (pH 6.9±0.2), the time taken to achieve a HR of ≥100 bpm alone was 2±1.5 min and the time taken to achieve a combined outcome of HR≥100 bpm & SpO2 of ≥80% was 9±2 min. Compared to baseline and at HR of ≥ 100 bpm, arterial oxygenation (PaO2), peak pulmonary blood flow, and mean blood pressures (MBP) were significantly higher at the combined target of HR of ≥100 bpm & 80% SpO2 (fig 1 & fig 2). The arterial carbon dioxide (113±34 vs. 113±35 mm Hg), pH (6.9±0.2 vs. 7.0±0.2), and peak carotid blood flow (CBF - fig 2) were not different between HR≥100 bpm alone and HR≥100 bpm & SpO2≥80%. Oxygen delivery to the brain was significantly different from baseline at HR ≥ 100 bpm and at HR ≥ 100 bpm & SpO≥ 80% (fig 3). At HR ≥ 100 bpm & SpO≥ 80%, there was a non-significant higher oxygen delivery to the brain compared to HR≥100 bpm.


Conclusion: In the asphyxiated preterm lambs, the targets of a HR of ≥100 bpm and a SpO2≥ 80% is significantly better from a hemodynamic and oxygenation perspective compared to HR≥ 100 bpm alone. This physiological difference explains, confirms, and justifies the clinical importance of targeting HR of ≥100 bpm & SpO≥ 80% while resuscitating preterm infants.

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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