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updated 12/16/2010 1:47:35 PM ET 2010-12-16T18:47:35

Next time you go under the knife for a surgical procedure, you might want to think twice about the environment. Anesthetic gasses, found a new study, contribute to global warming more than you might expect.

The amount of gas used in any given surgery is small, and global warming is not a reason to put off a necessary procedure. But anesthetic gasses are potent heat-trappers, and small emissions from medical procedures add up -- rivaling the emissions from a million passenger cars each year.

Because the study found certain gasses to be more threatening to the environment than others, the findings suggest that anesthesiologists might want to factor climate change into their decision-making process when they weigh the merits of various drugs for their patients.

"Now there are accurate numbers for the climate impact of these gasses and doctors should, if possible, choose the one with the lowest impact," said Ole John Nielsen, an atmospheric chemist at the Copenhagen Center for Atmospheric Research. "It is not rocket science, as you say in the U.S. But it is still an important study with important results."

Nielsen and colleagues chose to look at three of the most common gasses used as general anesthetics: isoflurane, desflurane and sevoflurane. Before a procedure, patients inhale these gasses, which are mixed with either oxygen or nitrous oxide. But our bodies metabolize only a small fraction of them. Instead, more than 95 percent of the gasses used are released into the environment.

For each gas, the scientists calculated its heat-trapping power by measuring how much infrared energy could get through in a controlled laboratory setting. The researchers also factored in how long each gas lasts once it is released into the atmosphere.

Assuming about 200 million anesthetic procedures take place around the world each year, the study concluded that the total amount of gasses released for medical reasons are on par with annual carbon-dioxide emissions from a million cars or one coal-fired power plant. The study also found that a kilogram of anesthetic gas traps the same amount of heat as 1,620 kilograms (3,571 pounds) of CO2.

The researchers say their results, published in the British Journal of Anaesthesia, offer the first accurate estimate of the impact these gasses make on the environment.

So far, scientists have not detected any anesthetic gasses in the environment, and total levels are expected to be extremely small.

Still, the study points out that a whole lot of small actions by individuals can add up to make a big impact on the environment, said Dan Jaffe, an atmospheric chemist at the University of Washington, in Seattle and Bothell.

"There's a tendency to dismiss it and say it's a really tiny effect," Jaffe said. "It is a small effect. But the truth is that climate change is made up of billions of tiny effects."

The three gasses varied widely in their projected impacts, he added. Sevoflurane, which lingers in the atmosphere for less than two years, seems to cause the least damage. Desflurane, which lasts for nearly nine years, has the most impact.

That means that doctors might want to add the environment to their list of considerations while prepping patients for an operation.

"Realistically, if the doctor says, 'I think this is the best way to knock you out and the safest method,' let's face it: You or I would say, 'Yeah, let's go for that one,'" Jaffe said.

"If the doctor says they are equivalent in safety but this one has greater environmental implications, then choose the compound that going to be least damaging to the environment."

© 2012 Discovery Channel

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