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A Foul-Smelling Life-Saver?

Hydrogen sulfide, the chemical compound that causes the sulfurous odor of rotten eggs, also significantly improves the survival of rats that have lost extreme amounts of blood, a first-of-its kind study has shown.

Cell biologist Mark B. Roth and colleagues at the Fred Hutchinson Cancer Research Center reported their findings online ahead of print in The Journal of Trauma Injury, Infection, and Critical Care.

In a rat model of lethal hemorrhage, the researchers used hydrogen sulfide to induce a state of reversible metabolic hibernation, with the goal of reducing death caused by insufficient blood flow to organs and tissues. They found that 75 percent of rats administered with inhaled hydrogen sulfide and 67 percent of rats given intravenous hydrogen sulfide survived at least two weeks — the duration of the monitoring program — after losing more than half of their blood. In contrast, long-term survival rates for the untreated rats in the two control groups were 23 percent and 14 percent, respectively. Tests of the long-term survivors showed no observable side effects, and the rats eventually produced normal-sized litters of healthy pups.

"Our goal is to develop life-saving treatment for critically ill people suffering from acute, sustained blood loss, such as in a car accident or on the battlefield," said senior author Roth. "These findings have obvious implications for the military, but they also have tremendous implications for the civilian population."

Accordingly, the research was funded by the U.S. Defense Advanced Research Projects Agency. The ultimate objective is to design self-injectable hydrogen-sulfide kits that badly wounded soldiers could use on the battlefield to temporarily restrain their metabolism and lower their oxygen demand. "The military feels that if a soldier can be kept alive for at least three hours, that would allow time for the situation to be stabilized and the scene of the incident secured enough to allow evacuation of that soldier to an area where he or she can get medical attention," Roth said.

Scientists are not exactly sure how hydrogen-sulfide treatment prevents death from profound blood loss, but one theory is that the chemical compound, in lowering metabolism, also reduces oxygen demand; this might enable the hippocampus, the brain segment that controls the body's autonomic functions, to withstand the low levels of oxygen. Another possibility is that hydrogen sulfide, which is found naturally in the blood, is depleted during hemorrhage and must be replaced to maintain life processes.

This study follows a seminal 2005 paper published in the journal Nature, in which Roth and his colleagues reported the first use of hydrogen sulfide to induce a state of reversible hibernation in mice. The latest research is an attempt to demonstrate hydrogen sulfide's potential to treat conditions such as severe blood loss, hypothermia, cardiac arrest and stroke.