Armstrong L, Stenson B
Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA, Scotland, UK.
Arch Dis Child Fetal Neonatal Ed. 2006 Sep;91(5):F342-5. doi: 10.1136/adc.2005.086744. Epub 2006 Apr 25.
Cord blood lactate at birth is a marker of antenatal hypoxia, and is comparable to pH as a prognostic tool.
To determine, by a prospective observational study, the effect of delayed sampling from arteries and veins that were double clamped to isolate the blood from the placenta (clamped), and from vessels that were not isolated from the placenta (unclamped).
Paired samples taken from clamped and unclamped vessels at 0, 20, 40, and 60 minutes were analysed for lactate, base excess, pH, and Pco(2). Data were analysed as the change from time 0 at 20, 40, and 60 minutes.
Thirty eight placentas of infants delivered by elective caesarean section were studied. Arterial samples were taken from 20 placentas, and venous samples from 18 placentas. Arterial and venous lactate was significantly higher than at time 0 by 20 minutes in both clamped and unclamped vessels. Changes in unclamped vessels were greater than in clamped vessels. The pH remained unchanged over 60 minutes in clamped vessels, but changed significantly in unclamped vessels. Base excess changed significantly in both clamped and unclamped vessels.
Cord blood samples taken after 20 minutes delay are unreliable for lactate measurement, even if the vessel has been doubly clamped to isolate the blood from the placenta. Current guidelines that state that blood can be sampled from a clamped cord for up to one hour after delivery should not apply to the interpretation of lactate or base excess. Delayed sampling from unclamped cords is very unreliable.
出生时脐血乳酸是产前缺氧的标志物，作为一种预后工具可与pH值相媲美。
通过一项前瞻性观察性研究，确定对双重钳夹以隔离来自胎盘的血液的动脉和静脉（钳夹组）以及未与胎盘隔离的血管（未钳夹组）进行延迟采样的影响。
分析在0、20、40和60分钟时从钳夹组和未钳夹组血管采集的配对样本中的乳酸、碱剩余、pH值和二氧化碳分压。数据作为在20、40和60分钟时相对于0时刻的变化进行分析。
对38例择期剖宫产分娩的婴儿的胎盘进行了研究。从20个胎盘采集了动脉样本，从18个胎盘采集了静脉样本。在钳夹组和未钳夹组血管中，动脉和静脉乳酸在20分钟时均显著高于0时刻。未钳夹组血管的变化大于钳夹组血管。钳夹组血管的pH值在60分钟内保持不变，但未钳夹组血管的pH值有显著变化。钳夹组和未钳夹组血管的碱剩余均有显著变化。
即使血管已被双重钳夹以隔离来自胎盘的血液，延迟20分钟后采集的脐血样本用于乳酸测量也是不可靠的。目前规定分娩后可从钳夹的脐带采样长达1小时的指南不适用于乳酸或碱剩余的解读。从未钳夹的脐带进行延迟采样非常不可靠。
