Westgate J A, Bennet L, de Haan H H, Gunn A J
Department of Obstetrics & Gynecology, University of Auckland, Auckland, New Zealand.
Obstet Gynecol. 2001 Mar;97(3):454-9. doi: 10.1016/s0029-7844(00)01123-6.
To assess the clinical utility of overshoot fetal heart rate (FHR) decelerations by examining their occurrence after umbilical cord occlusions of varying frequency and length in near-term fetal sheep.
Fetuses were allocated to the following three groups: 1-minute umbilical cord occlusion repeated every 5 minutes (1:5 group, n = 8) or every 2.5 minutes (1:2.5 group, n = 8) or 2-minute occlusions repeated every 5 minutes (2:5 group, n = 4). Occlusions were continued for 4 hours or until fetal mean arterial pressure decreased below 20 mmHg during two successive occlusions.
In the 1:5 group, fetuses tolerated 4 hours of occlusion without hypotension or clinically significant acidosis and overshoot never occurred. In the 2:5 group, fetuses rapidly became hypotensive and acidotic, and occlusions were terminated at 116.3 +/- 22.9 min (mean +/- standard deviation). Overshoot was seen after every occlusion, starting with the first occlusion. In the 1:2.5 group, fetuses became progressively acidotic and hypotensive and occlusions were stopped at 183.1 +/- 42.8 min. Overshoot occurred after 91.6 +/- 42.5 minutes, at a pH of 7.17 +/- 0.06, base deficit 9.3 +/- 4.5 mmol/L. After the appearance of overshoot there was a more rapid decrease in fetal mean arterial pressure (0.25 [0.21, 0.35, 25-75th percentile] mmHg/minute versus 0.11 [0.03, 0.15] mmHg/minute before overshoot appeared, P <.01).
These data suggest that overshoot is related to longer (2-minute) occlusions or to developing fetal acidosis and hypotension during 1-minute occlusions. This pattern could have clinical utility, as 1-minute contractions are typical of active labor.
通过检查近足月胎羊不同频率和时长的脐带闭塞后过冲性胎儿心率（FHR）减速的发生情况，评估其临床实用性。
将胎儿分为以下三组：每5分钟重复1分钟脐带闭塞（1:5组，n = 8）或每2.5分钟重复1分钟脐带闭塞（1:2.5组，n = 8）或每5分钟重复2分钟脐带闭塞（2:5组，n = 4）。闭塞持续4小时或直至胎儿平均动脉压在连续两次闭塞期间降至20 mmHg以下。
在1:5组中，胎儿耐受4小时闭塞，未出现低血压或临床上显著的酸中毒，且从未发生过冲。在2:5组中，胎儿迅速出现低血压和酸中毒，闭塞在116.3±22.9分钟（平均值±标准差）时终止。从第一次闭塞开始，每次闭塞后均可见过冲。在1:2.5组中，胎儿逐渐出现酸中毒和低血压，闭塞在183.1±42.8分钟时停止。过冲在91.6±42.5分钟时出现，此时pH值为7.17±0.06，碱缺失为9.3±4.5 mmol/L。过冲出现后，胎儿平均动脉压下降更快（0.25 [0.21, 0.35, 25 - 75百分位数] mmHg/分钟，而过冲出现前为0.11 [0.03, 0.15] mmHg/分钟，P <.01）。
这些数据表明，过冲与较长时间（2分钟）的闭塞或1分钟闭塞期间胎儿酸中毒和低血压的发展有关。这种模式可能具有临床实用性，因为1分钟宫缩是活跃分娩的典型表现。
