Association of Free Maternal and Fetal Ropivacaine After Epidural Analgesia for Intrapartum Cesarean Delivery: A Prospective Observational Trial

( Int J Obstet Anesth . 58;2024:103975. https://doi.org/10.1016/j.ijoa.2024.103975) Local anesthetics (LA), such as ropivacaine, are commonly used in epidural analgesia to manage labor pain. Ropivacaine, an amide LA, enters the maternal bloodstream through absorption from the epidural space and may also reach the fetus. It circulates in both bound and free forms in the plasma, with the free form being potentially toxic. Several factors influence maternal exposure to LAs, including the type and concentration of the anesthetic, duration of use, and delivery method. A study by Porter and colleagues showed that ropivacaine exposure in laboring women ranged from 57 to 225 mg. The neonatal population is particularly vulnerable to the toxic effects of LAs due to lower protein binding capacity and serum alpha- l -acid glycoprotein (AAG) levels, leading to a higher proportion of unbound anesthetic in their system.