Does the Use of Higher Versus Lower Oxygen Concentration Improve Neurodevelopmental Outcomes at 18-24 Months in Very Low Birthweight Infants - The HiLo-Trial

Purpose: Over the last 10 years, recommendations regarding the ideal level of oxygen for resuscitation in preterm infants have changed from 100 percent, down to low levels of oxygen (<30 percent), up to moderate concentration (30-65 percent). In addition, in 2010, oxygen saturation targeting was recommended as standard of care and this contributed to a change in clinical practice as clinicians were more likely and comfortable to start resuscitation at either 21percent (room air) or titrated levels of oxygen such as 30-40 percent. When the guidelines were again revised in 2015, the International Liaison Committee on Resuscitation (ILCOR) acknowledged that a critical knowledge gap continued to exist for the resuscitation of the preterm infants <37 weeks, highlighting the need to provide more concrete guidelines. This leaves clinicians in a challenging position. Despite the advances that have been achieved in perinatal and neonatal care, neonates are still vulnerable to the consequences of the oxidative effects from hyperoxia as well as the deleterious effects from hypoxia. A large, multi-centre international trial of sufficient sample size that is powered to look at safety outcomes such as mortality and adverse neurodevelopmental outcomes is required to provide the necessary evidenced to guide clinical practice with confidence.

Hypothesis: the null hypothesis for this study is that the incidence of mortality or abnormal neurodevelopmental outcomes at 24+/- 6 months corrected age will be no different by using either higher initial oxygen concentration of 60 percent compared to using lower initial oxygen concentration of 30 percent for resuscitation of preterm infants of 23 0/7- 28 6/7 weeks gestation.

Justification:

The use of supplementary oxygen may be crucial, but also potentially detrimental to premature infants at birth. High oxygen levels may lead to organ damage through oxidative stress, while low oxygen levels may lead to increased mortality. Excess oxygen exposure during the early post-birth period is associated with many complications and morbidities of preterm birth. Preterm infants have lower levels of anti-oxidant pathways consistent with their expected fetal environment of low oxygen exposure. Excess of oxygen free-radicals in infants intrinsically deficient in enzymatic antioxidants and non-enzymatic antioxidants may contribute to these morbidities. Pulmonary oxygen toxicity, through the generation of reactive oxygen and nitrogen species in excess of antioxidant defenses, is believed to be a major contributor to the development of bronchopulmonary dysplasia (BPD). Using lower oxygen concentrations at birth results in decreased oxidative stress markers and a decrease risk of developing BPD compared to higher oxygen concentrations. Other organs that may be damaged by such oxidative stress include kidneys, myocardium and the retina.

There is equally growing evidence that using lower oxygen concentrations will lead to lower oxygen saturation levels and bradycardia, which may lead to increased rates of mortality in this vulnerable group of infants. An individual patient analysis of clinical trials reported that 46% of preterm infants resuscitated with initial low oxygen concentration did not reach SpO2 of 80% at 5 min. This was associated with increased risk of major intraventricular hemorrhage (IVH), and an almost five times higher risk of death in this vulnerable group of infants. These data provide a warning note for the use of higher vs. lower initial oxygen concentration during delivery room resuscitation. As the investigator proceed in determining a safe range for resuscitation of ELBW/ELGA infants, it is highly likely that the optimum level of oxygen concentration is between the two extremes of 21 percent and 100 percent.