Neuraxial anesthesia in spaceflight and microgravity: a scoping review

As crewed missions extend beyond low Earth orbit, crews will need to manage serious injury and illness on their own, without evacuation to Earth. Regional and neuraxial anesthesia (spinal, epidural, and combined spinal–epidural techniques) have been proposed as safer than general anesthesia in this setting. They avoid airway management and keep the patient conscious, and they need little equipment. However, how these techniques behave in microgravity is largely unknown. On Earth, intrathecal anesthetic spread depends on gravity-linked factors such as baricity, patient position, spinal curvature, and cerebrospinal fluid (CSF) dynamics. Microgravity changes each of these. It removes density-driven gradients, lengthens the spine, causes paraspinal muscle atrophy, and triggers cardiovascular and neurological adaptation. The current literature on this question consists mainly of narrative and opinion pieces, including a 2026 mini review. There is no systematic, protocol-driven map of the evidence. Relevant work is spread across anesthesiology, neurosurgery, physiology, and aerospace medicine, and much of it sits in grey literature such as technical reports and conference abstracts. A scoping review is therefore the appropriate design. Our primary question is: what is known from published and grey literature about neuraxial and other regional anesthesia in spaceflight, microgravity, and ground-based analogs? We also aim to: map the types and volume of evidence (in-flight, analog, animal, cadaveric, bench/phantom, modeling, and expert opinion); describe the techniques, physiologic mechanisms, and analog settings studied (parabolic flight, head-down tilt bed rest, dry immersion, and neutral buoyancy); rate how well analog evidence transfers to true spaceflight, separately for each physiologic mechanism; identify and categorize knowledge gaps to guide research priorities. The review will follow JBI scoping review methodology and will be reported according to PRISMA-ScR. A health sciences librarian will design the search strategy, and a second librarian will peer-review it using the PRESS checklist. We will search MEDLINE, Embase, Scopus, Web of Science, and the Cochrane Library. Grey literature sources will include the NASA Technical Reports Server, ProQuest Dissertations & Theses, Aerospace Medical Association proceedings, and ESA/NASA repositories, supplemented by forward and backward citation searching. We will apply no date, language, or study-design limits. Two reviewers will screen and chart sources independently, and a third reviewer will resolve disagreements. Transferability will be rated using pre-specified criteria, which are provided in a supplementary file. Consistent with scoping review methodology, we will not perform a formal risk-of-bias appraisal. We expect the evidence base to be small and heterogeneous, consisting mostly of analog, bench, and expert-opinion sources, with very little in-flight human data. The review will produce: descriptive counts of the evidence by type, technique, analog setting, and year; a narrative synthesis organized by physiologic mechanism; an evidence-gap matrix that separates gaps in the evidence overall from gaps in evidence that actually applies to spaceflight. We anticipate that the most important gaps will involve mechanisms that ground analogs cannot reproduce, especially density-driven anesthetic spread. The findings are meant to guide future experimental work, inform the development of neuraxial anesthesia protocols for exploration-class missions, and determine whether a future systematic review would be feasible. Team: Charles Keldsen (Kaiser Permanente Bernard J. Tyson School of Medicine), Sophia Levy (UCLA College of Letters and Science), Sahar Nangoli, Sarah Sorensen-Ogata, and Haig Aintablian, MD (David Geffen School of Medicine at UCLA).