Is membrane expansion relevant to anesthesia? Mean excess volume

Area of Science:

• Anesthesiology
• Membrane Biophysics
• Pharmacology

Background:

• Conflicting theories exist regarding membrane expansion's role in anesthesia mechanisms.
• Discrepancies arise from differing definitions of membrane expansion: simple volume increase versus creation of excess volume.
• Understanding these concepts is crucial for resolving disputes about anesthesia's molecular basis.

Purpose of the Study:

• To clarify the discrepancies between various concepts of membrane expansion in anesthesia.
• To critically review volume theories of anesthesia.
• To explain the physical meaning of pressure reversal of anesthesia.

Main Methods:

• Critical review of existing volume theories of anesthesia.
• Analysis of factors influencing membrane volume changes upon anesthetic interaction.
• Examination of the relationship between excess volume and pressure reversal of anesthesia.

Main Results:

• Membrane volume change is not a simple summation of membrane and anesthetic volumes.
• Theories assuming simple volume increase are incompatible with pressure reversal of anesthesia.
• The presence of excess volume is necessary for pressure to antagonize anesthesia.

Conclusions:

• Excess volume creation, not just membrane expansion, is critical for anesthesia.
• The mechanism of excess volume generation is likely the key event inducing anesthesia.
• The mean excess volume hypothesis suggests membrane size is irrelevant to anesthesia.