Data Sheet 1_Circulating prostaglandin E2 concentrations decrease at birth in premature lambs.docx

RationaleDuring pregnancy, prostaglandin E2 (PGE2) is released from the placenta and circulates in relatively high concentrations in the fetus. As PGE2 suppresses breathing, PGE2 concentrations must decrease after birth, but the timing and mechanisms behind this decrease are unknown. We hypothesised that both umbilical cord clamping and lung aeration contribute to the reduction in PGE2 concentrations after birth. Materials and methodsInstrumented premature lambs (138–141 days gestation) were randomised to receive either physiological-based cord clamping (PBCC; cord clamping after ventilation onset; n = 5) or immediate cord clamping (ICC; before ventilation onset; n = 6). PGE2 concentrations were measured in pulmonary and carotid arterial blood 30 s after ventilation onset, after lung aeration and 30 s after cord clamping. All PGE2 data are expressed relative to fetal PGE2 concentrations. ResultsRelative to fetal concentrations, ventilation onset decreased PGE2 concentrations in the carotid (p = 0.036) and pulmonary arteries (p = 0.052) in PBCC lambs, whereas cord clamping had no further additional effect on PGE2 concentrations in these lambs. In ICC lambs, cord clamping decreased PGE2 concentrations, relative to fetal concentrations, in both the carotid (p = 0.001) and pulmonary arteries (p < 0.001). Ventilation onset further decreased PGE2 concentrations in both the carotid (p = 0.002) and pulmonary arteries (p = 0.014). ConclusionBoth umbilical cord clamping and ventilation onset independently decrease PGE2 concentrations immediately after birth, which may enhance breathing activity, although the effect of cord clamping is reduced by ventilation onset.研究背景：妊娠期间，前列腺素E2（prostaglandin E2, PGE2）由胎盘释放，并在胎儿体内以较高浓度循环。由于PGE2会抑制呼吸活动，因此出生后其浓度必须下降，但该浓度下降的时机与机制尚不明确。本研究假设，脐带钳夹与肺通气均可促成出生后PGE2浓度的降低。 材料与方法：将经仪器监测的妊娠138~141天的早产羔羊随机分为两组，分别接受基于生理的脐带钳夹（PBCC：通气启动后进行脐带钳夹，n=5）与即刻脐带钳夹（ICC：通气启动前进行脐带钳夹，n=6）。分别在通气启动后30秒、肺充气完成后及脐带钳夹后30秒，检测肺动脉与颈动脉血液中的PGE2浓度。所有PGE2数据均以胎儿体内PGE2浓度为参照进行表达。 研究结果：相较于胎儿初始浓度，PBCC组羔羊的颈动脉（p=0.036）与肺动脉（p=0.052）内PGE2浓度在通气启动后均出现下降，而脐带钳夹未对该组羔羊的PGE2浓度产生额外显著影响。在ICC组羔羊中，脐带钳夹即可使颈动脉（p=0.001）与肺动脉（p<0.001）内的PGE2浓度相较于胎儿初始浓度出现下降；在此基础上进行通气启动，可进一步降低两处血管内的PGE2浓度（颈动脉：p=0.002；肺动脉：p=0.014）。 结论：脐带钳夹与通气启动均可独立降低出生即刻的PGE2浓度，这或许可增强呼吸活动；不过通气启动会削弱脐带钳夹对PGE2浓度的调控效果。