Procedural Mechanics and Pitfalls of Neuraxial Anesthesia in Obstetrics: A Physics-based Approach

Neuraxial anesthesia is an effective method of pain control for various procedures in obstetrics and gynecology, pain medicine, and orthopedic surgery. Spinals and epidurals can greatly enhance a patient’s quality of life but there often exists a limited understanding of the mechanics of performing such procedures, thus hindering the troubleshooting of non-functional or partially functional epidurals. Understanding how mechanical factors like patient anatomy, clinical history, anesthetic injection rate, pressure gradients between the epidural and intrathecal spaces, and medication infusion are crucial for preventing complications like false analgesic levels, failed epidurals, or total/high spinal. In addition to reviewing knowledge available in anesthesia textbooks, the present article introduces a simplified model for understanding neuraxial anesthesia and postulates a mechanism of action for epidurals. Additionally, this article aims to identify high-risk situations that could lead to a total spinal, while considering the unique anatomical changes experienced during pregnancy.