A study presented at the American Society of Anesthesiologists (ASA) meeting in October of last year found that patients who chew gum in the immediate preoperative period may safely undergo surgery.

The authors, based at the University of Pennsylvania, found that gum chewing increases saliva production and the volume of fluid in the stomach, but stomach acidity was equivalent to that of non-gum chewers. An article about the study said The mean gastric volume, or total amount of liquid in the stomach, was statistically higher in patients who chewed gum before their procedure (13ml) versus those who did not (6ml). A 7 mL difference might be statistically significant, but surely is not clinically important.

The research differed from previous studies because it involved patients who underwent upper gastrointestinal endoscopy, which enabled the investigators to recover all of the fluid in the stomach for testing. Prior studies had been done using nasogastric tubes, and it was impossible to determine whether all gastric fluid was recovered when the tubes were suctioned.

The study involved 34 gum chewers who were allowed to chew any type or any amount of gum, compared to 33 patients who did not chew gum.

Another article quoted its lead author.

“We found that although chewing gum before surgery increases the production of saliva and therefore the volume of stomach liquids, it does not affect the level of stomach acidity in a way that would elevate complication risks,” explains Dr. Goudra.

He says patients shouldn’t be encouraged to chew gum before procedures involving anesthesia, but the habit shouldn’t necessitate the cancellation or delay of scheduled cases if other aspiration risk factors aren’t present.

There has been long-standing debate about the subject of whether using gum and hard candy should be treated the same as ingesting a regular meal.

I wrote about this on my blog back in January 2014 and pointed out that the ASA guidelines do not address the issue.

In an effort to do due diligence, I was able to locate the abstract of this paper on the ASA website. I’m glad I did because the abstract came to the opposite conclusion.

When the abstract was submitted, it included fewer patients—24 who chewed gum and 23 who did not.

The average gastric volumes were 9.78 mL for the gum chewers and 24.08 mL for the non-gum chewers (p = 0.027), and pH values were not significantly different (p = 0.094). It looks like regression to the mean occurred as the number of subjects increased.

In the original abstract, the authors concluded the following: Chewing gum in the preoperative fasting period leads to significant increase in the residual gastric volumes, with no difference in pH. We recommend that patients who have inadvertently chewed gum in the fasting period should be treated as full stomach and management modified accordingly. [Emphasis added]

So what is going on here? This would not be the first time that an abstract differed from the final paper. Actually, this sort of thing happens quite frequently. However in this case, the conclusions of the two versions are diametrically opposed to each other.

The study was presented at a meeting. Let’s see what happens when it is submitted to a journal for peer review.

The correct way to have done the study would have been to try to calculate the number of patients needed to be studied (power analysis) beforehand.

Since this was not done, I recommend we go with the conclusion of the larger number of patients studied because it is larger and agrees with my bias that chewing gum is not potentially harmful.

Skeptical Scalpel is a retired surgeon and was a surgical department chairman and residency program director for many years. He is board-certified in general surgery and critical care and has re-certified in both several times. He blogs at SkepticalScalpel.blogspot.com and tweets as @SkepticScalpel.

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