Probabilistic Risk Assessment of Prophylactic Surgery Before Extended-Duration Spaceflight

Area of Science:

• Space Medicine
• Surgical Risk Assessment
• Probabilistic Risk Analysis

Background:

• Appendicitis and cholecystitis pose risks during long-duration space missions.
• Prophylactic surgery could mitigate these risks but introduces others, such as small bowel obstruction (SBO).
• Probabilistic risk assessment (PRA) is a tool for evaluating complex medical decisions in resource-limited environments.

Purpose of the Study:

• To compare the risks of appendicitis and cholecystitis during a Mars mission versus the risk of SBO from prophylactic surgery.
• To utilize PRA to quantify the benefits and risks of prophylactic appendectomy and/or cholecystectomy for astronauts.

Main Methods:

• A probabilistic risk assessment (PRA) model employing Monte Carlo simulation was developed.
• Risks were forecasted for a 2.5-year Mars mission scenario.
• Outcomes compared included probability of medical evacuation (pEVAC) and probability of loss of crew life (pLOCL).

Main Results:

• Combined prophylactic appendectomy and cholecystectomy increased the probability of medical evacuation (pEVAC) due to SBO compared to no surgery.
• The no surgery group showed a slightly higher probability of loss of crew life (pLOCL) than groups with prophylactic surgery.
• The increased pEVAC from SBO in surgical groups was deemed a significant risk, especially given the impossibility of evacuation.

Conclusions:

• The analysis does not support prophylactic removal of the appendix and/or gallbladder for spaceflight due to increased SBO risk and limited reduction in loss of life probability.
• Medical evacuation, even if possible, represents a critical risk in space missions.
• Future advancements in surgical techniques or medical capabilities may alter these findings, highlighting the utility of PRA for space mission planning.