Physiologic changes in microgravity may lead to unpredictable effects of spinal anesthesia

Regional techniques such as spinal anesthesia may offer advantages over general anesthesia for autonomous medical care during long-duration space missions, yet their behaviour in microgravity remains largely uncharacterised. On Earth, intrathecal anesthetic spread depends on baricity, posture, spinal curvature, and cerebrospinal fluid dynamics. Microgravity alters these determinants by diminishing gravity-dependent density gradients, modifying spinal geometry through paraspinal atrophy and elongation, and inducing cardiovascular and neurophysiologic adaptations that may affect block characteristics and hemodynamic tolerance. This Mini Review synthesises current evidence on spinal anesthetic mechanisms and spaceflight physiology to identify where terrestrial assumptions may fail in microgravity. Key knowledge gaps and research priorities are highlighted to inform the development of safe neuraxial anesthesia protocols for exploration-class missions.