Stenning Fiona J, Hooper Stuart B, Kluckow Martin, Crossley Kelly J, Gill Andrew W, Wallace Euan M, Te Pas Arjan B, LaRosa Domenic, Polglase Graeme R
The Ritchie Centre, The Hudson Institute of Medical Research, Monash University, Clayton, VIC, Australia.
Department of Obstetrics and Gynaecology, Monash University, Clayton, VIC, Australia.
Front Pediatr. 2019 Oct 9;7:405. doi: 10.3389/fped.2019.00405. eCollection 2019.
Placental transfusion has been thought to be the main benefit of delayed umbilical cord clamping (DCC) in preterm neonates. However, the importance of cardiovascular stability provided by allowing lung aeration prior to cord clamping has recently been highlighted. We aimed to determine the influence of blood volume changes on cardiovascular stability at birth. Preterm lambs (0.85 gestation) were instrumented for measurement of pulmonary, systemic and cerebral blood pressures and flows, systemic oxygen saturation and cerebral oxygenation. Left ventricular output (LVO) was assessed by Doppler Echocardiography. Lambs underwent immediate cord clamping followed by (1) 25 ml/kg infusion of whole blood over (90 s; or 2) withdrawal of 10 ml/kg blood over 90 s. Ventilation was initiated 30 s after volume change (2 min after cord clamping) and was maintained for 30 min. Blood infusion significantly increased pulmonary blood flow (PBF) which maintained systemic cardiac output during the infusion, and increased carotid arterial pressure, flow and heart rate, which remained elevated until after ventilation onset. Upon completion of transfusion PBF rapidly returned to control levels and LVO decreased. Conversely, blood withdrawal decreased PBF and LVO. The cardiovascular changes that accompanied ventilation onset were similar between groups. Providing a blood volume transfusion immediately after umbilical cord clamping maintains PBF and cardiac output during the transfusion, which does not persist beyond the period of the transfusion. Our study implies that an apneic newborn cannot maintain cardiac output through an increase blood volume alone. Importantly, delaying umbilical cord clamping until after breathing/aeration of the lung may be a way to maintain cardiac output throughout delivery at birth.
胎盘输血一直被认为是延迟脐带结扎（DCC）对早产儿的主要益处。然而，最近强调了在脐带结扎前允许肺通气所提供的心血管稳定性的重要性。我们旨在确定出生时血容量变化对心血管稳定性的影响。对早产羔羊（妊娠0.85）进行仪器安装，以测量肺、体循环和脑血流动力学参数、全身血氧饱和度和脑氧合。通过多普勒超声心动图评估左心室输出量（LVO）。羔羊出生后立即进行脐带结扎，随后（1）在90秒内输注25ml/kg全血；或（2）在90秒内抽取10ml/kg血液。在容量变化后30秒（脐带结扎后2分钟）开始通气，并维持30分钟。输血显著增加了肺血流量（PBF），在输血期间维持了体循环心输出量，并增加了颈动脉血压、血流和心率，这些指标在通气开始前一直保持升高。输血结束后，PBF迅速恢复到对照水平，LVO下降。相反，抽血减少了PBF和LVO。两组在通气开始时伴随的心血管变化相似。脐带结扎后立即进行血容量输血可在输血期间维持PBF和心输出量，但这种情况不会在输血期后持续。我们的研究表明，呼吸暂停的新生儿不能仅通过增加血容量来维持心输出量。重要的是，将脐带结扎延迟到肺呼吸/通气后可能是在出生时整个分娩过程中维持心输出量的一种方法。
