Research Update- Chewing Gum Study
'Should you chew gum before surgery?
Launceston General Hospital anaesthetist Dr Gregg Best asks a simple, but important medical question.
September, 2020
Our perception of medical research often relates to thoughts of the discovery of vaccines or finding cures for disease.
This is obviously an inaccurate perception of reality because the vast majority of health research being undertaken across the globe is looking for answers to the smaller, but vitally important, medical questions that lead to better treatments.
One such study, undertaken by anaesthetist Dr Gregg Best from the LGH Department of Anaesthesia and funded by the Clifford Craig Foundation, was seeking to find if chewing gum whilst fasting for an anaesthetised medical procedure is a risk to the patient, and thus leads to the cancellation of the procedure.
A simple but important medical question. Here is the final report from the project.
Assessing the influence of chewing gum on the residual gastric volume in patients fasting for surgery
Fasting from food and fluids before an anaesthetic is a well-established practice and is done to decrease the risk of aspiration of stomach contents into the lungs while the patient. The current standard fasting guidelines for patients in Australian hospitals are a minimum of six hours for food and two hours for clear fluids.
Many fasting patients find the sensation of thirst and dry mouth unpleasant,
so some patients use chewing gum to alleviate these symptoms. Unfortunately, there is currently no consensus about the appropriate time to stop chewing gum before an anaesthetic. As a result, many anaesthetists will deem patients who have been chewing gum to be inadequately fasted, which often leads to these patients’ anaesthesia either being delayed or cancelled depending on the individual circumstances.
The aim of this study was to determine whether chewing gum causes an increased volume of fluid in the stomach, thus poses an increased risk of aspiration in adults who are fasting in preparation for an anaesthetic. It is known from previous studies that despite fasting, most patients will have a small residual volume of fluid (<50ml) in their stomach consisting of secretions formed by gastric glands and swallowed saliva.
After gaining ethics committee approval we conducted a study over a period of 18 months at the Endoscopy Unit at Calvary, St Vincent’s campus on 237 adult patients undergoing elective gastroscopy under general anaesthesia. During the gastroscopy this fluid could be seen and sucked out using the gastroscope into a bottle, with the volume and pH of the fluid was then measured. The patients were divided into two groups, 120 patients in the control group who fasted routinely and 117 patients in the study group who were allowed to chew gum while fasting.
The primary outcome of the study was to determine if there was a difference in the proportion of patients who had a higher volume of fluid (>50ml) in their stomach. Six out of 120 (5.0%) in the control group and nine out of 117 (7.7%) in the chewing gum group had residual gastric fluid volumes greater than 50ml. Statistically, there was no difference in this incidence rate meaning the study showed that chewing gum while fasting did not increase the risk of having a high residual volume when compared with standard preoperative fasting.
The study also compared the average fluid volumes and distribution of fluid pH between the two groups. Again, there was no statistical difference between the groups for these two measures. From these results, we concluded that chewing gum in adult patients while following routine pre-anesthetic fasting instructions does not increase the volume or acidity of stomach fluid compared with non-gum chewing control patients, and recommended that published anaesthetic fasting guidelines should be standardised to allow chewing gum use while fasting as long as appropriate safeguards are implemented to ensure disposal of the gum before the start of an anaesthetic.
Our findings would also support the position that patients should not have their procedures cancelled or delayed by their anaesthetist because they have been chewing gum while fasting for a procedure requiring an anaesthetic.