O2079: What Is the Optimal Duration of Umbilical Cord Clamping in a Preterm Asphyxiated Ovine Model ?

Background: Current guidelines suggests that it is reasonable to delay umbilical cord clamping for 30s after birth in most vigorous preterm neonates. There is insufficient evidence for optimal cord management in preterm infants with low heart rate (HR) needing immediate resuscitation.

Methods: Our objectives were to compare the effect of early cord clamping ventilation (ECCV) and various time frames of delayed cord clamping ventilation (DCCV), and resuscitation using 60% supplemental O2 on:
a) primary outcome - i) combined HR of ≥100 bpm & peripheral SpO2 of ≥ 80% by 5 min, ii) time to achieve the primary outcome b) secondary outcomes - effect on gas exchange, pulmonary/systemic hemodynamics.
Following instrumentation, a total of 21 preterm lambs (126-128d, ~28wk human neonates) were asphyxiated by umbilical cord occlusion to achieve HR < 90bpm. The lambs were randomized to one of the four groups, as shown in Fig 1. In the 1) ECCV group (Controls), the umbilical cord was clamped immediately & ventilated. In the study, DCCV groups: Umbilical cord was intact while ventilation was initiated 2) DCCV1 - until 1 minute, 3) DCCV2 - until 2 minutes 4) DCCV3 - until 3 minutes, 5) DCCV5 - until 5 minutes. Initial supplemental oxygen of 60% was used in all groups and titrated based on recommended preductal SpO2. Data on gas exchange and hemodynamics were collected for the first ten min.

Results: All lambs in DCCV5 achieved the primary composite outcome HR of ≥100 bpm & peripheral SpO2 of ≥ 80% by 5 min. The time taken to achieve the primary outcome in DCCV5 (5±0 min) was significantly lower (p-0.003) compared to DCCV1 & ECCV. There was no statistical difference between the groups' supplemental O2 exposure and arterial oxygenation (Fig 2a, Fig 2b, Fig 2c) . Arterial pH was not different between groups (fig 3a). Arterial carbon dioxide was significantly higher (p-0.0001) in ECCV & DCCV1 compared to DCCV5 (Fig 3b). Pulmonary blood flow was significantly higher (p-0.0001) in DCCV5 compared to ECCV & DCCV1(Fig 4a). Carotid blood flow was highest in the ECCV group and was statistically different (p- < 0.0001) compared to other groups(Fig 4b).

Conclusion: In an asphyxiated preterm ovine model, resuscitation with an intact cord for 5 min increased the incidence of primary outcome, decreased the time to achieve primary outcome and improved gas exchange by increasing pulmonary blood flow. Our results suggest that resuscitating an asphyxiated preterm infant with an intact cord could help with transition better than ECCV.