RELATIVE NARCOTIC POTENCY AND MODE OF ACTION OF SULFUR-HEXAFLUORIDE AND NITROGEN IN HUMANS

Impairments of psychomotor, perceptual, and cog abilities were determi ned in nine male subjects exposed to inhaled SF6 partial pressures of 0, 52, 104, and 156 kPa and to inhaled N-2 partial pressures of 103, 5 75, 825, and 1,075 kPa. Also data from a previous study with inhaled N 2O partial pressures of 0, 13, 26, and 39 kPa were included. With the highest gas concentrations, performances were reduced by 41-57%. Effec tive doses for a 20% performance impairment were 830, 97, and 21.5 kPa for N-2, SF6, and N2O, respectively, yielding relative narcotic poten cies 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 in creasing tendency for hydrate formation (decreasing hydrate dissociati on pressure) for the three gases is N-2, N2O, and SF6. Thus, mild to m oderate inert gas narcosis in humans shows the same positive relations hip to lipid solubility as was shown in previous animal models that ut ilized much deeper levels of anesthesia.