Changes in fetal baroreceptor sensitivity during intrauterine inflammation in preterm fetal sheep

Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on fetal baroreceptor sensitivity in preterm fetal sheep. The changes in fetal baroreceptor sensitivity were measured in seven chronically instrumented preterm fetal sheep. Fetal baroreceptor sensitivity was measured in three phases: (A) control phase, defined as the 24 h before the first injection of LPS; (B) acute phase, defined as the 24 h between the first and second injections of LPS; and (C) fetal acidosis phase, defined as the time from the second LPS injection until intrauterine fetal death. Histological examinations of the fetal membrane and umbilical cord were also conducted. Each fetus developed metabolic acidosis after the second injection of LPS. The fetuses died 24.7 (SD = 6.1) hours after the second injection of LPS. Both the umbilical cord and fetal membranes showed histological evidence of severe inflammation. In total, 163 fetal baroreceptor measurements were performed in this experiment (A, <i>n</i> = 77 times; B, <i>n</i> = 60 times; C, <i>n</i> = 26 times). Fetal baroreceptor sensitivity showed significant differences in all three phases (A: 2.7 [SD = 0.2]; B: 2.5 [SD = 0.2]; and C: 1.5 [SD = 0.2]). Post hoc tests showed that baroreceptor sensitivity in the acidosis phase had decreased significantly compared to that in the control and acute phases (<i>p</i>&lt;.001 and <i>p</i>=.002, respectively). Fetal baroreceptor sensitivity decreased during fetal acidosis induced by LPSs.

压力反射（Baroreflex）是一种可减慢胎儿心率的调节机制。本研究旨在探讨脂多糖（lipopolysaccharide, LPS）诱导的内毒素血症对早产胎羊压力感受器敏感性的影响。本实验对7只经慢性手术植入监测装置的早产胎羊的压力感受器敏感性变化进行了检测。胎羊压力感受器敏感性的检测分为三个阶段：（A）对照期，定义为首次注射LPS前的24小时；（B）急性期，定义为首次与第二次注射LPS之间的24小时；（C）胎儿酸中毒期，定义为第二次注射LPS至宫内胎儿死亡的时段。本研究同时对胎膜与脐带开展了组织病理学检查。所有胎羊在第二次注射LPS后均出现代谢性酸中毒，并于第二次注射后24.7（SD=6.1）小时死亡。脐带及胎膜的组织学检查均显示存在重度炎症表现。本实验总计完成163次胎羊压力感受器敏感性检测，其中阶段A共77次，阶段B共60次，阶段C共26次。三个阶段的胎羊压力感受器敏感性存在显著差异（阶段A：2.7 [SD=0.2]；阶段B：2.5 [SD=0.2]；阶段C：1.5 [SD=0.2]）。事后检验结果显示，酸中毒期的压力感受器敏感性较对照期与急性期均显著降低（分别为p<.001与p=.002）。综上，LPS诱导的胎儿酸中毒可导致胎羊压力感受器敏感性下降。