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Toxic Sewer Gas Induces Suspended Metabolism in Mice

Heart rate dropped 50% while maintaining blood pressure

WEDNESDAY, March 26, 2008 (HealthDay News) -- Using small amounts of potentially deadly hydrogen sulfide, or sewer gas, U.S. researchers were able to decrease metabolism and heart rate in mice, while maintaining blood pressure and oxygen levels -- putting them in a suspended animation-like state.

"Hydrogen sulfide is the stinky gas that can kill workers who encounter it in sewers; but when administered to mice in small, controlled does, within minutes, it produces what appears to be totally reversible metabolic suppression," study senior author Dr. Warren Zapol, chief of anesthesia and critical care at Massachusetts General Hospital, said in a prepared statement.

"This is as close to instant suspended animation as you can get, and the preservation of cardiac contraction, blood pressure and organ perfusion is remarkable," Zapol said.

When the mice inhaled the gas, it took as little as 10 minutes for their metabolic measurements, such as oxygen consumption and carbon dioxide production, to decline. The measurements remained low as long as the mice were inhaling the gas and returned to normal within 30 minutes after the mice started breathing normal air.

The rodents' heart rate decreased almost 50 percent while breathing the hydrogen sulfide, but there was no significant change in heart beat strength or blood pressure. The respiration rate did slow, but there were no changes in blood oxygen levels, which suggests that vital organs weren't at risk of oxygen starvation.

The study was published in the April issue of Anesthesiology.

"Producing a reversible hypometabolic state could allow organ function to be preserved when oxygen supply is limited, such as after a traumatic injury," study author Dr. Gian Paolo Volpato, an anesthesiology research follow, said in a prepared statement. "We don't know yet if these results will be transferable to humans, so our next step will be to study the use of hydrogen sulfate in larger mammals."

"It could be that inhaled hydrogen sulfate will only be useful in small animals, and we'll need to use intravenous drugs that can deliver hydrogen sulfate to vital organs to prevent lung toxicity in larger animals," Zapol added.

More information

The Wisconsin Department of Health and Family Services has more about sewer gas.

SOURCE: Massachusetts General Hospital, news releae, March 25, 2008
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