Early echocardiographic markers following deferred cord clamping with high or low oxygen in extremely low gestation infants (DOXIE-Echo).

Deferred cord clamping (DCC) with adequate ventilation improves cardiovascular transition and survival. Brief use of 100% oxygen during neonatal resuscitation may enhance ventilation and reduce pulmonary vascular resistance. Determine whether high oxygen (HI, 100%) versus low oxygen (LO, 30%) support during DCC affects postnatal hemodynamics in extremely preterm infants. In this double-blinded randomized sub-study, infants born at 23⁰-27⁶ weeks' gestation received respiratory support with HI or LO oxygen during 90 s of DCC. After cord clamping, all infants were managed per standard guidelines. An echocardiogram was performed within 12 postnatal hours to assess cardiac function. Baseline characteristics of 110 infants (51 HI, 59 LO) were similar. Right ventricular output did not differ between groups (293 ± 105 vs 268 ± 71 ml/kg/min; p = 0.17), nor did additional measures of cardiac function. Use of 100% oxygen during DCC did not adversely affect early transitional hemodynamics compared with 30% oxygen.