Smokers scheduled for elective surgery are told to abstain before their operations because smoking interferes with wound healing and increases risk for complications. But what about vaping before surgery—is that OK? Until recently, the answer wasn’t known. But a new animal study from Boston University Medical School provides a pretty clear clue.

For the study, researchers exposed two groups of 15 rats either to e-cigarette vapor or cigarette smoke for 30 minutes, twice a day for 30 days. A third group of 15 rats was not exposed to anything and served as the control. At the end of the 30 days, the vapor- and smoke-exposed groups had their blood levels of nicotine checked, and nicotine in both groups was found to be about the equivalent of the level in a human smoking one pack of cigarettes per day. Then all three groups of rats underwent a surgical procedure—replacement of a piece of skin on their backs—designed to see how well the wounds would heal. The wounds were monitored to see whether the blood vessels under the skin were keeping the skin alive (and the wound was healing)…or necrosis was setting in, meaning the piece of skin was dying.

Results: After 30 days, 68.7% of the wounds in the “smoking” group showed signs of necrosis…and so did 65.9% of the wounds in the “vaping” group—a difference that is not statistically significant. In other words, the vaping group healed as poorly as the smoking group. Meanwhile, only 51% of the wounds in the control group of rats showed signs of necrosis.

Now, this is not to suggest that human smokers or vapers would experience similarly high levels of necrosis after a surgical wound, because their wounds would be treated (such as with stitches) and tended to (such as with frequently changed dressings) in ways that the rats’ wounds were not. Instead, it is the difference in the body’s ability to muster its own healing power after smoking and after vaping that was demonstrated here—and that can definitely make a difference in speed and quality of healing even when more care is given.

These results did not surprise the researchers. Nicotine narrows blood vessels and for that reason can be a prime contributor to necrosis. There is at least as much nicotine in e-cigarette vapor as in tobacco smoke, they noted.

Although this study was done with rats, the researchers point out that previous cigarette research using rats has proved to be a reliable indicator of effects on humans. They consider this study sufficient evidence that surgeons should tell their patients to stop vaping before elective surgery. (The study researchers did not suggest how long before surgery to stop, but the American College of Surgeons recommends that smokers abstain from four to six weeks before to four weeks after their operations.)

And while it was not part of this study, these researchers also dispute the automatic assumption that e-cigarettes are safer than cigarette smoking when it comes to cancer risk. E-cigarettes have high levels of formaldehyde and diethylene glycol, both known carcinogens—levels that may be higher than with traditional cigarettes, they state.

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