Please confirm that an ethics committee approval has been applied for or granted: Not relevant

Background and Aims The ambitious goals of crewed deep space missions, like Nasa’s Artemis program and SpaceX’s colonization targets, require preparations for potential astronaut health crises. Innovative solutions are necessary to overcome the challenges of administering anesthesia in the unique environment of space and the physiologic changes associated with prolonged microgravity exposure. Regional anesthesia offers a viable solution to these challenges, but its feasibility is yet to be tested.

Methods Our study assessed the feasibility of single-shot peripheral nerve blocks in a simulated microgravity environment (free-floating underwater) using a meat model. We randomized forty meat models to be injected under simulated microgravity and normal Earth gravity conditions. Post-injection, blinded assessors determined success rates. Assessed parameters included, ‘time to block’, ease of needle placement, and ease of image acquisition.

Results Block success rates were comparable in both scenarios (80% normal gravity versus 85% microgravity, p > 0.999) and there was no difference in the rate of accidental intra-neural injections (5% versus 5%). The median time to block on land was 27 [IQR 21-69] seconds versus 35 [IQR 22-48] seconds in simulated microgravity (p = 0.751). Ease of needle placement and ease of image acquisition were similar in both conditions.

Conclusions Despite challenges, regional anesthesia appears to be feasible in simulated microgravity. While our model is not a perfect analogue to true space conditions, it provides a foundation for subsequent research into the provision of anesthesia and analgesia during crewed space missions.