胎儿酸中毒、2-氯普鲁卡因与剖宫产硬膜外麻醉

Philipson E H, Kuhnert B R, Syracuse C D

Am J Obstet Gynecol. 1985 Feb 1;151(3):322-4. doi: 10.1016/0002-9378(85)90295-9.

Amide-linked local anesthetic agents, such as lidocaine and bupivacaine, can become "trapped" in their ionized forms on the fetal side of the placenta, and therefore their net transfer across the placenta is increased. An ester-linked local anesthetic agent, 2-chloroprocaine, is rapidly metabolized, and placental transfer is limited. Since the metabolism of 2-chloroprocaine by fetal plasma is slower than in maternal plasma, the potential for ion trapping exists. The purpose of this study was to determine the disposition of 2-chloroprocaine and its metabolite, chloroaminobenzoic acid, in relation to the umbilical cord vein pH at delivery, and specifically, to determine whether ion trapping exists. Epidural anesthesia with 2-chloroprocaine was administered to 44 women at term prior to cesarean section. At delivery the levels of 2-chloroprocaine and chloroaminobenzoic acid in maternal plasma and umbilical cord vein were quantitated. Neonates were divided into two groups based on the umbilical cord vein pH at delivery. Ten of the 44 patients delivered neonates with a pH less than or equal to 7.25 (acidotic group) while 34 delivered neonates with a pH greater than 7.25 (nonacidotic group). The mean umbilical cord vein pH in the acidotic and nonacidotic groups was 7.22 +/- 0.03 and 7.32 +/- 0.03, respectively (p less than 0.001). There were also no differences between the groups in maternal and neonatal clinical characteristics or in the total dose of 2-chloroprocaine administered or the drug-to-delivery interval. The pharmacologic results did not demonstrate a statistical difference in the concentration of 2-chloroprocaine or chloroaminobenzoic acid in the maternal vein or umbilical cord vein at delivery between the two groups. Thus the results of this study demonstrate that placental transfer of 2-chloroprocaine is not influenced by fetal acidosis. Therefore these data suggest that 2-chloroprocaine may be the drug of choice when fetal acidosis or distress is anticipated.

酰胺类局部麻醉药，如利多卡因和布比卡因，可能会以离子形式“被困”在胎盘胎儿侧，因此它们通过胎盘的净转运增加。酯类局部麻醉药2-氯普鲁卡因代谢迅速，胎盘转运有限。由于胎儿血浆对2-氯普鲁卡因的代谢比母体血浆慢，存在离子捕获的可能性。本研究的目的是确定2-氯普鲁卡因及其代谢产物氯氨基苯甲酸在分娩时与脐静脉pH值的关系，特别是确定是否存在离子捕获。44名足月剖宫产术前的妇女接受了2-氯普鲁卡因硬膜外麻醉。分娩时对母体血浆和脐静脉中2-氯普鲁卡因和氯氨基苯甲酸的水平进行了定量。根据分娩时脐静脉pH值将新生儿分为两组。44例患者中有10例分娩的新生儿pH值小于或等于7.25（酸中毒组），34例分娩的新生儿pH值大于7.25（非酸中毒组）。酸中毒组和非酸中毒组的脐静脉平均pH值分别为7.22±0.03和7.32±0.03（p<0.001）。两组在母体和新生儿临床特征、2-氯普鲁卡因给药总量或药物至分娩间隔方面也无差异。药理学结果显示，两组在分娩时母体静脉或脐静脉中2-氯普鲁卡因或氯氨基苯甲酸的浓度无统计学差异。因此，本研究结果表明，2-氯普鲁卡因的胎盘转运不受胎儿酸中毒影响。因此，这些数据表明，当预计有胎儿酸中毒或窘迫时，2-氯普鲁卡因可能是首选药物。