The Effect of Intra-Abdominal Pressure on Sensory Block Level of Single-Shot Spinal Anesthesia for Cesarean Section

Abstract

(Int J Obstet Anesth. 2015;24(1):35–40) There is an association between pregnancy and increased intrathecal local anesthetic spread (and thus, lower local anesthetic requirements), although the exact mechanisms behind this association are unknown. There are 2 potential anatomic explanations: (1) in the supine position, the pregnant uterus compresses the inferior vena cava (IVC), diverting blood into the vertebral venous system and displacing lumbosacral cerebrospinal fluid (CSF) in a cranial direction; or (2) in addition to direct compression of the IVC, the growing uterus during pregnancy leads to a global increase in intra-abdominal pressure (IAP).