Intrapartum paracervical block anesthesia with 2-chloroprocaine.

Most of the reports of fetal bradycardia and acidosis following paracervical block anesthesia have involved the use of amide-linked anesthetics, such as lidocaine and mepivacaine. The purposes of this study were (1) to determine placental transfer of an ester-linked local anesthetic, 2-chloroprocaine, and its inactive metabolite, 2-chloroaminobenzoic acid (CABA) following paracervical block and (2) to evaluate the clinical use of 2-chloroprocaine for paracervical block anesthesia. Accordingly, 2-chloroprocaine was administered to 16 normal pregnant women in labor at term. Following injection, the levels of 2-chloroprocaine or CABA in maternal and neonatal plasma or urine were quantitated. Multiple clinical parameters, including the presence or absence of fetal bradycardia, were monitored before and after the paracervical block. The pharmacologic data indicated that 2-chloroprocaine is rapidly hydrolyzed. At delivery only trace levels of 2-chloroprocaine were present in 6.3% of the maternal samples and 25% of the cord vein samples. Furthermore, only 0.24% of the total dose of 2-chloroprocaine administered was recovered in neonatal urine as CABA. The clinical data showed no adverse effects on the parturient or neonate. Therefore, the data suggest that paracervical block anesthesia with 2-chloroprocaine may offer safe analgesia during the first stage of labor. Larger clinical studies appear warranted.