Turns out waking up during surgery isn’t the only potential downside to general anesthesia.
According to new peer-reviewed research published in the journal Geophysical Research Letters, the gases used to knock out patients before an operation are making a very small contribution to human-caused climate change. The gases — desflurane, isoflurane, and sevoflurane — have been detected in the atmosphere as far as Antarctica, the study showed. (Nitrous oxide is another common anesthetic, but it wasn’t included in the study because of how widely it’s used for other purposes.)
All three gases are greenhouse gases, meaning that like carbon dioxide, they trap heat in the atmosphere. But they’re also much more potent than carbon dioxide, meaning they trap more heat per pound emitted. In desflurane’s case, for instance, one kilogram (2.2 pounds) traps as much heat as 2,500 kilograms (5,512 pounds), according to a report in Phys.org.
Relative to other emissions sources, the research confirmed that anesthetic gases’ contribution to climate change is pretty minor. The amount of desflurane in the atmosphere, for instance, was measured as 0.30 parts per trillion (ppt). Isoflurane clocked in at .097 ppt, sevoflurane at 0.13 ppt, and halothane came in at 0.0092 ppt.
In all, emissions of those anesthetic gases in 2014 amounted to the equivalent of between 2.5 million and 3.7 million metric tons of carbon dioxide. That’s the same as the emissions of between 526,316 and 778,947 passenger vehicles. Comparatively, the U.S. coal industry produces 1,562 million metric tons of carbon dioxide equivalent every year — the same as 329 million cars.
Still, that doesn’t mean anesthetic gases aren’t worth reducing, according to Yale University School of Medicine anesthesiologist Jodi Sherman. Sherman, who reviewed the study before publication, told ThinkProgress that she was alarmed to find her profession was contributing even in small part to climate change — especially when mitigation measures are widely available.
“From my perspective what makes it alarming is that it’s significant enough that it could be measured at all,” she said, “and that as population grows and number of surgeries increases, this can be expected to rise.”
It’s long been known that anesthetic gases were heat-trapping and could therefore potentially contribute to climate change. But prior to the release of this research, estimates of just how much has accumulated in the global atmosphere have been “highly speculative,” the study said.
This study claims to be the first to base an estimate off of actual measurements of the gases taken by scientists in the field. Before, scientists had estimated the amount of anesthetic gases in the atmosphere by calculating things like how much of each gas is sold every year, and how much is released through vents.
Sherman said there are potentially easy ways to significantly cut anesthetic gas emissions. Chief among them, she said, is cutting out the use of the most offending gases: nitrous oxide, which wasn’t measured by the study but is “probably the most prevalent,” and desflurane, the most potent of the bunch. Others have disagreed, arguing the drugs have clinical advantages. Still, the study noted that 80 percent of anesthetic gas emissions measured came from desflurane.
Sherman also suggested that anesthesiologists work to carefully minimize fresh gas flow rate — which refers to the total volume of gas that flows from the anesthetic machine into the breathing system per minute — and use alternatives to inhaled anesthetics when clinically possible. Alternatives that can sometimes be used when recommended include intravenous anesthesia, and regional anesthesia via either the spine or an epidural.
“This is a low-hanging fruit,” she said. “Behavior change would be very advantageous.”