A Short History of Hydrogen Sulfide
From the sewers of Paris to physiological messenger
No less a scientist than Linus Pauling and his associates described the magnetic properties of another blood pigment, which they called sulfmethemoglobin. This pigment is easily prepared in pure form by mixing hydrogen sulfide with methemoglobin, and it is chemically analogous to cyanmethemoglobin, in which the cyanide ion is bound to ferric irons of heme. The hydrosulfide anion (HS–) also binds to ferric heme, albeit not quite so tenaciously as cyanide. Indeed, this reaction has been exploited medically as an antidote to cyanide poisoning. One can deliberately inject sodium nitrite intravenously to generate a tolerable level of methemoglobin. The methemoglobin will temporarily bind free cyanide as the inactive complex cyanmethemoglobin. Over time the cyanide is slowly released, at a rate at which the body’s natural detoxification mechanisms can deal with it.
At least three laboratories have demonstrated that the same principles can be applied to hydrogen sulfide poisoning and that induced methemoglobinemia can indeed be lifesaving. At least a half dozen successful human resuscitations have been reported in the literature. The odds against its successful application, however, are high. Few poisons are more rapidly acting than inhaled hydrogen sulfide, and inhalation is invariably the route of exposure. Sulfide poisoning tends to occur in remote locations, and there is seldom a medically qualified individual on the scene who is prepared with a parenteral form of nitrite and trained to make intravenous injections. Most successful resuscitations from cyanide poisoning have occurred in individuals who ingested soluble salts of cyanide, where absorption is delayed.