Tailoring oxygen needs of ELBW infants in the delivery room

During fetal life, arterial partial pressure of oxygen (PaO2) is about 25–30 mmHg. This relatively hypoxemic environment permits fetal growth and differentiation; however, in fetal-to-neonatal transition, PaO2 abruptly increases to 80–90 mmHg. This sudden influx of oxygen to the tissue causes a physiologic oxidative stress which, under normal circumstances, triggers specific metabolic pathways to favor postnatal adaptation. However, an excess of oxygen after birth causes an imbalance between the formation of free radicals and antioxidant defences, leading to oxidative damage of cellular molecules.
In particular, fetal to neonatal transition poses an extraordinary challenge for the extremely low birth weight (ELBW) neonate. While a number of factors (regionalization of perinatal care, use of antenatal steroids, postnatal surfactant, new modalities of mechanical ventilation, prevention of streptococcus group B infection, improvement of nutrition and general care) have contributed significantly to reducing neonatal mortality in ELBW neonates, mortality in the delivery room (DR) has not substantially changed in the last decade and still represents 15% of liveborn and 32% of total deaths of ELBW infants.
Indeed a significant number of ELBW neonates will need proactive resuscitation to achieve postnatal stabilization. Positive pressure ventilation and oxygenation are currently the most relevant interventions in the DR; however, oxygen needs during resuscitation still represent a conundrum for neonatologist and should be tailored to the specific situation of every neonate. In fact, hyperoxemia favors oxidative stress and subsequent organ injury, while hypoxemia is associated with long-term neurodevelopmental impairment. In the DR, rapid and reliable arterial oxygen saturation (SpO2) readings are indispensable and can be achieved with the latest generation of pulse oximeters: reliable measurements can be obtained in 90 seconds and will reflect brain perfusion.
It has been shown that ELBW neonates can be successfully resuscitated with lower concentrations of oxygen as had been done traditionally. Moreover, reducing oxygen load has resulted in achievement of arterial partial pressures of oxygen at admission closer to the physiologic range, less oxidative stress and less inflammation. The availability of reference ranges for arterial SpO2 for ELBW neonates in the first 10 minutes after birth has been an extraordinary step forward in our ability to individually titrate oxygen needs, thus avoiding the risks of both hypo- and hyperoxemia. Despite these advances, the optimal fraction of inspired oxygen (FiO2) to initiate resuscitation and the safest SpO2 percentiles for ELBW neonates during the first minutes of life are still unknown. Therefore, there is a need for further research in adequately powered randomized clinical trials performed in resuscitation settings provided with homogenous technical equipment and adequately trained personal. Until then, optimal ventilation at birth and individually tailoring FiO2 seem to be the most reasonable and safe approach.

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