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October 12, 2014
3:00 PM - 4:30 PM
Room Room 245
Effect of Gum Chewing on the Volume and pH of Gastric Contents-A Prospective Randomized Study
Basavana Goudra, M.D., FRCA, FCARCSI, Preet Mohinder Singh, M.D., Augustus Samuel, Student
University of Pennsylvania, Philadelphia, Pennsylvania, United States
Preoperative fasting guidelines recommended by the American Society of Anesthesiologists (ASA) do not allow oral ingestion including liquids for varying time periods before induction of anesthesia(1). Although, these guidelines do not explicitly mention chewing gum, it would be considered as a non-clear liquid. An unsuspecting patient chewing gum in the preoperative period may face cancellation or delay of the surgical procedure. Studies evaluating the effect of gum chewing on the volume and Ph of residual gastric contents have used a gastric tube for aspiration of stomach contents (2-4). The completeness of suctioning with this method is debatable.


After institutional review board approval, 50 patients scheduled to undergo an upper gastrointestinal (GI) endoscopy or a combined upper GI endoscopy and a colonoscopy were contacted over the telephone on the evening before the procedure. After an explanation of the proposed study, willing patients were randomized to either chew gum or continue to follow the recommended fasting guidelines. There was no limit on the type, number of gums or the duration of chewing. They were allowed to chew until the injection of sedative medications. Intravenous conscious sedation was provided with a combination of midazolam, fentanyl and rarely diphenhydramine. An endoscope was inserted after adequate sedation and the stomach contents were suctioned completely into an empty plastic container. The volume and pH was measured immediately.


3 patients were excluded due to technical issues. The data analyzed included 24 patients who chewed gum (G) and 23 who did not (NG). The mean (SD) gastric volumes were 9.78 (9.1) and 24.08 (23.74) and pH was 2.72(2.14) and 3.92(2.40) respectively. Mann-Whitney test was used for comparing the volumes as the data was not normally distributed, which showed significantly lower volumes in NG group (p=0.027). Students-t test was used to compare pH, and the values were 2.72(2.14) and 3.92(2.40) respectively with no statistically significant difference(p=0.094). Both groups were comparable in all other demographic and procedure related factors.


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.


1. American Society of Anesthesiologists Committee. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: an updated report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology. 2011 Mar;114(3):495-511.

2. Dubin SA, Jense HG, McCranie JM, Zubar V. Sugarless gum chewing before surgery does not increase gastric fluid volume or acidity. Can J Anaesth J Can Anesth. 1994 Jul;41(7):603-6.

3. Søreide E, Holst-Larsen H, Veel T, Steen PA. The effects of chewing gum on gastric content prior to induction of general anesthesia. Anesth Analg. 1995 May;80(5):985-9.

4. Schoenfelder RC, Ponnamma CM, Freyle D, Wang S-M, Kain ZN. Residual gastric fluid volume and chewing gum before surgery. Anesth Analg. 2006 Feb;102(2):415-7.

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