Relative narcotic potency and mode of action of sulfur hexafluoride and nitrogen in humans

Abstract

Impairments of psychomotor, perceptual, and cognitive abilities were determined in nine male subjects exposed to inhaled SF6 partial pressures of 0, 52, 104, and 156 kPa and to inhaled N2 partial pressures of 103, 575, 825, and 1,075 kPa. Also data from a previous study with inhaled N2O partial pressures of 0, 13, 26, and 39 kPa were included. With the highest gas concentrations, performances were reduced by 41–57%. Effective doses for a 20% performance impairment were 830, 97, and 21.5 kPa for N2, SF6, and N2O, respectively, yielding relative narcotic potencies of 1.0:8.5:39. The order of narcotic potencies is the same as for the lipid solubility of the three gases. In contrast, the order of increasing tendency for hydrate formation (decreasing hydrate dissociation pressure) for the three gases is N2, N2O, and SF6. Thus, mild to moderate inert gas narcosis in humans shows the same positive relationship to lipid solubility as was shown in previous animal models that utilized much deeper levels of anesthesia.