At low concentrations, hydrogen sulphide causes suspended animation in mice.
Credit: iStockphoto
SYDNEY: The same gas that makes rotten eggs and sewage stink may one day help doctors perform open heart surgery, according to a new U.S. study.
Hydrogen sulphide can be toxic in large doses, but recently researchers in Boston used it at the low concentration of 80 parts per million to induce suspended animation in mice, without causing a decrease in blood pressure.
“We were surprised to find that blood pressure didn’t change, even though heart rate fell [from 500 beats per minute] to 200 beats per minute,” said Gian Paola Volpato, reporting earlier this week at the American Physiological Society conference in Virginia. Drops in blood pressure are a problem of current anaesthetics, and if scientists can replicate these results in larger animals ‘sewer gas’ may one day become an important tool in medicine.
The soporific effects of hydrogen sulphide have been known since 2005, when a team of scientists from the University of Washington reported that the gas caused mice to lose body heat and depressed their metabolic rates by 90 per cent. In the wake of this finding, Researchers at the Massachusetts General Hospital set out to measure what effect the gas had on blood pressure.
In general, according to the researchers, a mouse with such a low heart rate would have dangerously low blood pressure, hovering near death. Not so with these mice, who returned to normal two hours after the gas was discontinued. The Massachusetts team thinks this may have implications for human medicine.
Anaesthesia generally causes a drop in blood pressure, thereby reducing the amount of oxygen-rich blood that vital organs receive. Additionally, in complex procedures such as cardiac surgery doctors intentionally impair circulation even further. Currently, the only proven method of protecting organs during these procedures uses hypothermia - lowering the body’s core temperature - to slow down the body’s metabolism. The procedure is not perfect, however.
“Hypothermia has some adverse effects, including depressing cardiovascular function,” said Fumito Ichinose, another of the study’s authors. “If we can figure out how hydrogen sulphide reduces metabolic rate without depressing myocardial function, we may be able to reduce metabolism and protect organs without using hypothermia.”
It’s not clear yet whether hydrogen sulphide will have the same effects on other animals as it does on mice. According to the researchers, the gas may affect mice in this way because they hibernate in nature.
In order to see if the same effects might translate to humans, further studies on animals such as sheep or pigs are needed. “If the same thing happens to those species it would be much more interesting,” said Ichinose.
