Effects of Pressure

The exposure of whole organisms to increasing hydrostatic pressures often increases the anesthetic dose required to bring about unresponsiveness, a phenomenon called the pressure reversal of anesthesia. In experiments with mammals, pressure is increased by the addition of helium, because helium does not produce anesthesia and possesses little or no inherent anesthetic effect at high pressures.^[13] At a total pressure of 100 atm, a 30% to 60% increase in the partial pressure of inhaled anesthetics is required to abolish the righting reflex in the mouse.^[14] However, it remains debatable whether pressure reversal represents a specific antagonism at the site of anesthetic action or is simply a generalized phenomenon that counteracts a global depression produced by anesthetics.