The cardiopulmonary benefits of physiologically based cord clamping persist for at least 8 hours in lambs with a diaphragmatic hernia

Introduction: Infants with congenital diaphragmatic hernia can suffer severe respiratory insufficiency and pulmonary hypertension after birth. Aerating the lungs before removing placental support (physiologically based cord clamping, PBCC) increases pulmonary blood flow (PBF) and reduces pulmonary vascular resistance (PVR) in lambs with a diaphragmatic hernia (DH). We hypothesized that these benefits of PBCC persist for at least 8 h after birth.

Methods: At ∼138 days of gestation age (dGA), 21 lambs with a surgically induced left-sided DH (∼86 dGA) were delivered via cesarean section. The umbilical cord was clamped either before ventilation onset (immediate cord clamping, ICC, n = 9) or after achieving a tidal volume of 4 ml/kg, with a maximum delay of 10 min (PBCC, n = 12). The lambs were ventilated for 8 h, initially with conventional mechanical ventilation, but were switched to high-frequency oscillatory ventilation after 30 min if required. Ventilatory parameters, cardiopulmonary physiology, and arterial blood gases were measured throughout the study.

Results: PBF increased after ventilation onset in both groups and was higher in the PBCC DH lambs than the ICC DH lambs at 8 h (5.2 ± 1.2 vs. 1.9 ± 0.3 ml/min/g; p < 0.05). Measured over the entire 8-h ventilation period, PBF was significantly greater (p = 0.003) and PVR was significantly lower (p = 0.0002) in the PBCC DH lambs compared to the ICC DH lambs. A high incidence of pneumothoraces in both the PBCC (58%) and ICC (55%) lambs contributed to a reduced sample size at 8 h (ICC n = 4 and PBCC n = 4).

Conclusion: Compared with ICC, PBCC increased PBF and reduced PVR in DH lambs and the effects were sustained for at least 8 h after ventilation onset.