Optimal Duration of Umbilical Cord Clamping with Ventilation in a Preterm Asphyxiated Ovine Model

<b>Background</b>: There is inadequate evidence to support recommendations for the delayed clamping of umbilical cords in preterm neonates who are born non-vigorous. <b>Objective</b>: In a preterm bradycardic ovine model, our objective was to compare the effects of early cord clamping with ventilation (ECCV) and various time periods of delayed cord clamping with ventilation (DCCV) at 1 min (DCCV1), 2 min (DCCV2), 3 min (DCCV3), 4 min (DCCV4), and 5 min (DCCV5). The primary composite outcome was (i) incidence of achieving a combined heart rate (HR) ≥ 100 bpm and preductal saturation (SpO₂) ≥80% by 5 min, and (ii) time to attain this outcome. Secondary outcomes were to evaluate gas exchange/hemodynamics. <b>Methods:</b> 32 preterm lambs of 126-128-day gestational age were randomized to one of six groups: ECCV (<i>n</i> = 5), DCCV1 (<i>n</i> = 6), DCCV2 (<i>n</i> = 5), DCCV3 (<i>n</i> = 6), DCCV4 (<i>n</i> = 6), and DCCV5 (<i>n</i> = 4). Asphyxia was induced by umbilical cord occlusion to attain a HR ≤ 90 beats per minute (bpm). <b>Results</b>: All lambs in DCCV5 achieved a primary composite outcome by 5 min. The time taken to achieve the primary composite outcome in DCCV5 was significantly lower (<i>p</i> = 0.02). Partial pressure of arterial carbon dioxide (PaCO₂) was significantly lower (<i>p</i> = 0.0001) in DCCV5. Peak pulmonary blood flow (PBF) was significantly higher (<i>p</i> = 0.0001) in DCCV5 while peak carotid blood flow (CBF) was highest in the ECCV (<i>p</i> < 0.0001) compared to other groups. <b>Conclusions</b>: In a preterm ovine model of asphyxia, resuscitation with an intact umbilical cord for 5 min increased the incidence and reduced the time to achieve the primary composite outcome, while also improving gas exchange by enhancing pulmonary blood flow, compared to shorter durations of DCCV and ECCV. These findings suggest that DCCV for 5 min may offer physiological advantages in the resuscitation of non-vigorous preterm neonates, warranting further investigation in clinical settings.