Abstract
BackgroundAs measurement of arterial oxygen saturation (SpO2) is common in the delivery room, target SpO2 ranges allow clinicians to titrate oxygen therapy for preterm infants in order to achieve saturation levels similar to those seen in normal term infants in the first minutes of life. However, the influence of the onset of ventilation and the timing of cord clamping on systemic and cerebral oxygenation is not known.AimWe investigated whether the initiation of ventilation, prior to, or after umbilical cord clamping, altered systemic and cerebral oxygenation in preterm lambs.MethodsSystemic and cerebral blood-flows, pressures and peripheral SpO2 and regional cerebral tissue oxygenation (SctO2) were measured continuously in apnoeic preterm lambs (126±1 day gestation). Positive pressure ventilation was initiated either 1) prior to umbilical cord clamping, or 2) after umbilical cord clamping. Lambs were monitored intensively prior to intervention, and for 10 minutes following umbilical cord clamping.ResultsClamping the umbilical cord prior to ventilation resulted in a rapid decrease in SpO2 and SctO2, and an increase in arterial pressure, cerebral blood flow and cerebral oxygen extraction. Ventilation restored oxygenation and haemodynamics by 5–6 minutes. No such disturbances in peripheral or cerebral oxygenation and haemodynamics were observed when ventilation was initiated prior to cord clamping.ConclusionThe establishment of ventilation prior to umbilical cord clamping facilitated a smooth transition to systemic and cerebral oxygenation following birth. SpO2 nomograms may need to be re-evaluated to reflect physiological management of preterm infants in the delivery room.
Highlights
Aeration of the lungs at birth is the primary trigger for the transition from fetal to newborn patterns of gas exchange and cardiopulmonary circulation[1,2,3,4]
We investigated whether the initiation of ventilation, prior to, or after umbilical cord clamping, altered systemic and cerebral oxygenation in preterm lambs
18.7% of all babies born in Australia in 2009 required respiratory support in the form of oxygen therapy or intermittent positive pressure ventilation to assist with the transition at birth[5]
Summary
Aeration of the lungs at birth is the primary trigger for the transition from fetal to newborn patterns of gas exchange and cardiopulmonary circulation[1,2,3,4]. 2010 reported the normal range of SpO2 in preterm infants during the first 10 minutes of life[6] These infants all had the umbilical cord clamped early, which was the standard practice at the time. These nomograms showed that the median SpO2 at 1 minute is 62% (47–72% IQR) for preterm infants and 68% (55–75%) for term infants not requiring respiratory support. As measurement of arterial oxygen saturation (SpO2) is common in the delivery room, target SpO2 ranges allow clinicians to titrate oxygen therapy for preterm infants in order to achieve saturation levels similar to those seen in normal term infants in the first minutes of life. The influence of the onset of ventilation and the timing of cord clamping on systemic and cerebral oxygenation is not known
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