Polglase Graeme R, Schmölzer Georg M, Roberts Calum T, Blank Douglas A, Badurdeen Shiraz, Crossley Kelly J, Miller Suzanne L, Stojanovska Vanesa, Galinsky Robert, Kluckow Martin, Gill Andrew W, Hooper Stuart B
The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.
Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia.
Front Physiol. 2020 Jul 30;11:902. doi: 10.3389/fphys.2020.00902. eCollection 2020.
Current guidelines recommend immediate umbilical cord clamping (UCC) for newborns requiring chest compressions (CCs). Physiological-based cord clamping (PBCC), defined as delaying UCC until after lung aeration, has advantages over immediate UCC in mildly asphyxiated newborns, but its efficacy in asystolic newborns requiring CC is unknown. The aim of this study was to compare the cardiovascular response to CCs given prior to or after UCC in asystolic near-term lambs. Umbilical, carotid, pulmonary, and femoral arterial flows and pressures as well as systemic and cerebral oxygenation were measured in near-term sheep fetuses [139 ± 2 (SD) days gestation]. Fetal asphyxia was induced until asystole ensued, whereupon lambs received ventilation and CC before (PBCC; = 16) or after ( = 12) UCC. Epinephrine was administered 1 min after ventilation onset and in 3-min intervals thereafter. The PBCC group was further separated into UCC at either 1 min (PBCC, = 8) or 10 min (PBCC, = 8) after return of spontaneous circulation (ROSC). Lambs were maintained for a further 30 min after ROSC. The duration of CCs received and number of epinephrine doses required to obtain ROSC were similar between groups. After ROSC, we found no physiological benefits if UCC was delayed for 1 min compared to immediate cord clamping (ICC). However, if UCC was delayed for 10 min after ROSC, we found significant reductions in post-asphyxial rebound hypertension, cerebral blood flow, and cerebral oxygenation. The prevention of the post-asphyxial rebound hypertension in the PBCC group occurred due to the contribution of the placental circulation to a low peripheral resistance. As a result, left and right ventricular outputs continued to perfuse the placenta and were evidenced by reduced mean pulmonary blood flow, persistence of right-to-left shunting across the ductus arteriosus, and persistence of umbilical arterial and venous blood flows. It is possible to obtain ROSC after CC while the umbilical cord remains intact. There were no adverse effects of PBCC compared to ICC; however, the physiological changes observed after ROSC in the ICC and early PBCC groups may result in additional cerebral injury. Prolonging UCC after ROSC may provide significant physiological benefits that may reduce the risk of harm to the cerebral circulation.
当前指南建议对需要进行胸外按压（CC）的新生儿立即进行脐带夹紧（UCC）。基于生理的脐带夹紧（PBCC），定义为将UCC延迟至肺通气后，在轻度窒息的新生儿中比立即UCC具有优势，但在需要CC的心脏停搏新生儿中其疗效尚不清楚。本研究的目的是比较在心脏停搏的近足月羔羊中，在UCC之前或之后进行CC时的心血管反应。在近足月绵羊胎儿（妊娠139±2（标准差）天）中测量脐动脉、颈动脉、肺动脉和股动脉的血流和压力以及全身和脑氧合。诱导胎儿窒息直至出现心脏停搏，随后羔羊在UCC之前（PBCC；n = 16）或之后（n = 12）接受通气和CC。通气开始1分钟后及此后每隔3分钟给予肾上腺素。PBCC组在自主循环恢复（ROSC）后1分钟（PBCC，n = 8）或10分钟（PBCC，n = 8）时进一步分为UCC组。ROSC后羔羊再维持30分钟。两组接受CC的持续时间和获得ROSC所需的肾上腺素剂量相似。ROSC后，我们发现与立即脐带夹紧（ICC）相比，UCC延迟1分钟没有生理益处。然而，如果ROSC后UCC延迟10分钟，我们发现窒息后反弹性高血压、脑血流量和脑氧合显著降低。PBCC组窒息后反弹性高血压的预防是由于胎盘循环对低外周阻力的贡献。结果，左、右心室输出继续灌注胎盘，表现为平均肺血流量减少、动脉导管右向左分流持续存在以及脐动脉和静脉血流持续存在。在脐带保持完整的情况下，CC后有可能获得ROSC。与ICC相比，PBCC没有不良反应；然而，在ICC和早期PBCC组中ROSC后观察到的生理变化可能导致额外的脑损伤。ROSC后延长UCC可能提供显著的生理益处，从而降低对脑循环造成伤害的风险。
