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

Area of Science:

• Anesthesiology
• Space Medicine
• Physiology

Background:

• Regional anesthesia, like spinal anesthesia, offers potential benefits for autonomous medical care during long-duration space missions.
• However, the behavior and efficacy of spinal anesthesia in microgravity are not well understood.
• Current understanding of anesthetic spread on Earth relies on factors altered by spaceflight.

Purpose of the Study:

• To synthesize evidence on spinal anesthetic mechanisms and spaceflight physiology.
• To identify how terrestrial assumptions about anesthesia may fail in microgravity.
• To highlight knowledge gaps and research priorities for space anesthesia.

Main Methods:

• Literature review synthesizing current evidence.
• Analysis of spinal anesthetic determinants (baricity, posture, CSF dynamics).
• Consideration of microgravity's effects on physiology (spinal geometry, cardiovascular, neurophysiologic).

Main Results:

• Microgravity alters key factors influencing intrathecal anesthetic spread, including density gradients and spinal geometry.
• Cardiovascular and neurophysiologic changes in space may impact anesthetic block characteristics and patient tolerance.
• Terrestrial assumptions regarding spinal anesthesia are likely invalid in microgravity.

Conclusions:

• Significant knowledge gaps exist regarding spinal anesthesia in microgravity.
• Further research is crucial to develop safe and effective neuraxial anesthesia protocols for exploration-class space missions.
• Understanding these physiological changes is essential for astronaut safety during future space exploration.