The role of perioperative chewing gum on gastric fluid volume and gastric pH: a meta-analysis

doi:10.1016/j.jclinane.2014.07.005

Journal of Clinical Anesthesia

Volume 27, Issue 2, March 2015, Pages 146-152

https://doi.org/10.1016/j.jclinane.2014.07.005 Get rights and content

Highlights

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Meta-analysis was used to examine if preoperative gum chewing affects gastric pH and fluid volume.
•
Chewing gum before surgery results in small increases in gastric volume but no change in gastric pH.
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The small increases in gastric volume from chewing gum are likely of no clinical significance.
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Elective surgery should not necessarily be canceled or delayed in patients due to chewing gum.

Abstract

Study objective

To determine if preoperative gum chewing affects gastric pH and gastric fluid volume.

Design

Systematic review and meta-analysis.

Methods

Data sources included Cochrane, PubMed, and EMBASE databases from inception to June 2012 and reference lists of known relevant articles without language restriction. Randomized controlled trials in which a treatment group that chewed gum was compared to a control group that fasted were included. Relevant data, including main outcomes of gastric fluid volume and gastric pH, were extracted.

Results

Four studies involving 287 patients were included. The presence of chewing gum was associated with small but statically significant increases in gastric fluid volume (mean difference = 0.21 mL/kg; 95% confidence interval, 0.02-0.39; P = .03) but not in gastric pH (mean difference = 0.11 mL/kg; 95% confidence interval, − 0.14 to 0.36; P = .38). Gastric fluid volume and gastric pH remained unchanged in subgroup analysis by either sugar or sugarless gum type.

Conclusions

Chewing gum in the perioperative period causes small but statically significant increases in gastric fluid volume and no change in gastric pH. The increase in gastric fluid most likely is of no clinical significance in terms of aspiration risk for the patient. Elective surgery should not necessarily be canceled or delayed in healthy patients who accidentally chew gum preoperatively.

Introduction

Pulmonary aspiration of gastric contents is an uncommon event during the perioperative period with incidence, morbidity, and mortality estimates in the adult population of approximately 1 in 7000, 1 in 16,000, and 1 in 100,000, respectively [1]. Since Mendelson’s [2] original publication , several reports and studies of the incidence of aspiration have been published [3], [4], [5], [6], [7]. Raidoo et al. [8] reported that the volume of aspirate required to produce severe pneumonitis with significant mortality was 0.8 mL/kg and that aspirates up to 0.6 mL/kg did not cause severe pneumonitis in a primate model. These findings are in contrast to those of Roberts and Shirley [9] who quoted a risk reference range of greater than or equal to 25 mL (0.4 mL/kg) gastric volume and pH less than or equal to ≤ 2.5.

The effect of chewing gum may influence gastric contents in a variety of ways, including increasing saliva and swallowing, increasing gastric secretions, and simultaneously increasing or causing no change to gastric emptying. Given that studies on gastric volume have found equivocal results [10], [11], [12], [13], some anesthesiologists cancel or delay operative procedures if a patient has been chewing gum [14] because they believe that perioperative gum chewing increases saliva production, thereby increasing gastric volume and decreasing gastric pH. The concern is that gastric fluid volume would increase to a degree that would place the patient at risk for aspiration during induction of general anesthesia [10]. However, whether chewing gum ultimately increases the risk of aspiration has not yet been definitively addressed.

The American Society of Anesthesiologists (ASA) has developed practice guidelines for preoperative fasting to reduce the risk of pulmonary aspiration in healthy patients undergoing elective procedures [15]. The most recent ASA guidelines fail to address directly the issue of preoperative gum chewing, potentially leading physicians to vary, delay, or cancel a case rather than proceeding when the patient has possibly violated the nil per os (NPO) directive by chewing gum. Guidelines on perioperative fasting for children and adults from the European Society of Anesthesiology include the recommendation that “patients should not have their operation cancelled or delayed just because they are chewing gum, sucking a boiled sweet or smoking immediately prior to induction of anesthesia” [16]. The objective of this systematic review and meta-analysis was to determine if preoperative gum chewing affects gastric pH and gastric fluid volume.

Section snippets

Data sources and searches

This meta-analysis followed recent methodological guidelines Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [17]. The aim of the study was to identify all relevant randomized controlled trials that evaluated the effect of chewing gum before anesthesia induction on gastric volume and pH by comparing patients who chewed gum preoperatively to fasted NPO controls. A search of the National Library of Medicine’s MEDLINE, Cochrane Collaboration’s CENTRAL, and the EMBASE

Results

In the systematic review, 4 articles provided data on 287 patients, with the gum-chewing and control groups including 174 and 113 patients, respectively [10], [11], [12], [13]. Table 1 provides study characteristics, including details regarding assessment of gastric pH and/or volume. One treatment group chewing bicarbonate gum was excluded from analysis given expected changes in pH [13]. The gum-chewing group in each trial initiated chewing in the immediate preoperative period, chewed gum at

Discussion

In the first systematic review and meta-analysis on this topic, we found that chewing gum before induction of anesthesia resulted in small increases in gastric volume but no changes in gastric pH. For example, chewing gum would increase the gastric fluid volume in a 70-kg patient by approximately 9 to 15 mL. Though statistically significant, this increase in gastric fluid most likely is of no clinical significance in terms of risk for the patient. The exponential half time (t_½) of gastric

Acknowledgements

We would like to acknowledge Claire Levine, MS, ELS, for her help with the preparation of this manuscript.

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Cited by (28)

Preoperative gum chewing for different durations to prevent postoperative sore throat after endotracheal intubation: A randomized controlled trial
2023, Trends in Anaesthesia and Critical Care
Postoperative sore throat (POST) is one of the most prevalent patient complaints following endotracheal intubation (ETI). We conducted this trial to evaluate the preoperative chewing gums' effect for two or 4 min on POST after ETI.
This randomized controlled trial enrolled 150 female cases aged from 21 to 65 years old planned for elective breast surgery under general anesthesia. Cases were randomly distributed into three equal groups. Patients chewed one piece of sugar-free herbal gum for 2 min in Group G2 and for 4 min in Group G4 then spat it out. Group C: patients swallowed two times only before surgery.
One case in group G2, and two cases in group G4, and in group C dropped out. The numeric rating scale (NRS) was significantly lower in group G2 and group G4 than in group C with no difference between group G2 and group G4 at 2, 6, and 24h. Incidence of moderate/severe POST was significantly lower in both G2(16.33%) and G4 (10.42%) groups than in group C (54.17%), with no significant difference between group G2 and G4. Cough was significantly lower in group G2 (8.16%) and group G4(4.17%) than in group C (22.92%), with no significant difference between groups G2 and G4. Hoarseness of voice was comparable among the studied groups.
Preoperative gum chewing can efficiently decrease the incidence of POST following ETI. Chewing gum for 2 min is non-inferior to chewing gum for 4 min to decrease POST incidence.
Multicenter Survey on Staff Understanding of Preoperative Fasting Guidelines
2022, Journal of Perianesthesia Nursing
Citation Excerpt :
The tertiary pediatric hospital is an established pediatric center that has been using a fasting protocol for some time. Chewing gum is an area of much debate and the literature shows a slight, likely insignificant, increase in gastric volume.13 The survey, however, was assessing knowledge of the guideline which is deliberately conservative and treats chewing gum like food in case of swallowing.
To assess the knowledge of nursing staff regarding pediatric preoperative fasting in a tertiary pediatric center and a general hospital.
Anonymous electronic survey with nine questions modified to each institution.
This was a prospective quantitative study. Nursing staff at a tertiary pediatric center and pediatric nursing staff at a general hospital with pediatric services were eligible for participation. An anonymous electronic survey with nine questions via Survey Monkey was used over a 2-month period.
There were 295 participants from the tertiary pediatric center and 24 from the general hospital which represented 10% of overall nursing staff at the tertiary pediatric center and approximately 50% of pediatric nursing staff at the general hospital. At both the tertiary pediatric center and the general hospital, 50 to 80% of participants correctly answered most questions. More participants were correct for the fasting times for infants less than 6 month of age than for those over 6 months old. For clear fluids, 61 (20.7%) and 13 (4.4%) considered jelly and breast milk as clear fluids respectively at the tertiary pediatric center.
Preoperative fasting continues to be a core area of pediatric care that is not completely understood. Our survey showed that although the majority of staff claim to be able to access the hospital guidelines, knowledge of these guidelines can be improved. In light of ongoing changing evidence, it is clear that education is a key factor in reducing morbidity and improving patient experience related to preoperative fasting.
Prevention and Treatment of Gastrointestinal Morbidity
2021, Perioperative Medicine: Managing for Outcome, Second Edition
The prevention and treatment of perioperative gastrointestinal morbidity is an area where much attention has been paid in recent years. This chapter aims to review the more common adverse gastrointestinal outcomes including aspiration of gastric contents, postoperative nausea and vomiting, and postoperative ileus. Particular focus is spent on the different modalities of providing anesthetic care and how they affect patient outcomes. For each of these morbidities, the literature supporting risk stratification was reviewed in an effort to identify those populations in whom there was an increased risk. Once those patients for whom there is an increased risk area identified, the different modalities used to mitigate the incidence are discussed. The areas covered include: (1) Those tasks performed before the patient is ever administered an anesthetic including preoperative fluid ingestion; (2) What anesthesia providers can do during cases that will have a discernable benefit including medications given, types of anesthetic regimens, and timing of certain pharmacologic interventions; and (3) Patient management postoperatively that impacts return to appropriate bowel homeostasis.
Chewing gum for 1 h does not change gastric volume in healthy fasting subjects. A prospective observational study
2019, Journal of Clinical Anesthesia
Citation Excerpt :
Main outcome was identification of immediate changes in gastric content and volume with ultrasound after chewing gum in fasted healthy volunteers. Sample size calculation was based on the meta-analysis by Ouanes et al. [13] and the statistical calculator Granmo version 7.2 was used. First, a pilot test including 9 volunteers was conducted.
Perioperative fasting guidelines differ in their approaches to chewing gum in the preoperative period. Current recommendations range from canceling the surgery to proceeding with it. Given this lack of consensus, we performed gastric ultrasound assessments in healthy volunteers before and after a standardized period of chewing gum. The objective of our study was to determine if chewing gum for 1 h change the gastric volume.
Observational prospective analytical study.
Bedside gastric ultrasound.
Following institutional Review Board approval, 55 healthy (American Society of Anesthesiologists class I to II) fasted (non-surgical research) volunteers provided written informed consent to participate in the study. Morbid obesity, renal failure, diabetes mellitus, pregnancy and previous upper abdominal surgery were exclusion criteria.
Volunteers chewed gum for 1 h between the first and second assessment.
Four gastric ultrasound assessments were performed, the first one at baseline and then hourly thereafter.
Fifty-five healthy volunteers were studied. The proportion of subjects who presented a completely empty stomach (Grade 0 antrum) was similar at baseline and after 1 h of gum-chewing [81% vs. 84%, p = 0.19, CI 95% (−12%, 16%)]. Among those subjects who had visible fluid at baseline, the volume remained unchanged throughout the study period.
One hour of gum-chewing had no significant effect on the gastric fluid volume of healthy volunteers, suggesting that it may be safe for healthy subjects to chew gum prior to elective surgery.
Preoperative Evaluation, Premedication, and Induction of Anesthesia
2019, A Practice of Anesthesia for Infants and Children
Adequate preparation of children for anesthesia allows optimization of medical conditions and leads to decreased morbidity. The medical history and laboratory testing obtained preoperatively aid the anesthesiologist in determining readiness for the planned surgery. Preparedness begins with adherence to a preoperative fasting schedule for elective surgery, selecting appropriate premedication, formulating an anesthetic plan and anticipating postoperative concerns.
There are a variety of techniques for inducing general anesthesia. The technique used depends on a number of factors including the child's developmental age, understanding and ability to cooperate, previous experiences, the presence of a parent and the interaction of these factors with the child's underlying medical or surgical conditions.
This chapter discusses special problems encountered in the pediatric population that require additional considerations from anesthesiologists. The preoperative period can be a stressful time for the fearful child and for those with autism spectrum disorders thus requiring the anesthesiologist to tailor the approach to meet the child's needs. Other challenges that pediatric patients present include respiratory system conditions such as obstructive sleep apnea syndrome, bronchopulmonary dysplasia, difficult airway, upper respiratory tract infections and apnea in former preterm infants. Additional conditions that are discussed include diabetes, seizure disorders, and sickle cell disease. Finally, the detection of a cardiac murmur, anemia or a fever before elective surgery will present a dilemma whether to proceed.
The preoperative visit is an essential component of identifying the pediatric patient's needs and devising a plan that leads to a superior patient experience, a decrease in the number of cancellations and improved outcomes.
Preoperative Evaluation, Premedication, and Induction of Anesthesia
2018, A Practice of Anesthesia for Infants and Children
Adequate preparation of children for anesthesia allows optimization of medical conditions and leads to decreased morbidity. The medical history and laboratory testing obtained preoperatively aid the anesthesiologist in determining readiness for the planned surgery. Preparedness begins with adherence to a preoperative fasting schedule for elective surgery, selecting appropriate premedication, formulating an anesthetic plan and anticipating postoperative concerns.
There are a variety of techniques for inducing general anesthesia. The technique used depends on a number of factors including the child's developmental age, understanding and ability to cooperate, previous experiences, the presence of a parent and the interaction of these factors with the child's underlying medical or surgical conditions.
This chapter discusses special problems encountered in the pediatric population that require additional considerations from anesthesiologists. The preoperative period can be a stressful time for the fearful child and for those with autism spectrum disorders thus requiring the anesthesiologist to tailor the approach to meet the child's needs. Other challenges that pediatric patients present include respiratory system conditions such as obstructive sleep apnea syndrome, bronchopulmonary dysplasia, difficult airway, upper respiratory tract infections and apnea in former preterm infants. Additional conditions that are discussed include diabetes, seizure disorders, and sickle cell disease. Finally, the detection of a cardiac murmur, anemia or a fever before elective surgery will present a dilemma whether to proceed.
The preoperative visit is an essential component of identifying the pediatric patient's needs and devising a plan that leads to a superior patient experience, a decrease in the number of cancellations and improved outcomes.

View all citing articles on Scopus

^☆: Funding: supported by the Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University.

¹: These authors contributed equally as first authors.

²: Role: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

³: Role: This author helped conduct the study and write the manuscript.

⁴: Role: This author helped write the manuscript.

View full text

Original ContributionThe role of perioperative chewing gum on gastric fluid volume and gastric pH: a meta-analysis☆

Highlights

Abstract

Study objective

Design

Methods

Results

Conclusions

Introduction

Section snippets

Data sources and searches

Results

Discussion

Acknowledgements

Am J Obstet Gynecol

J Clin Anesth

Br J Anaesth

Control Clin Trials

Contin Educ Anaesth Crit Care Pain

The incidence and outcome of perioperative pulmonary aspiration in a university hospital: a 4-year retrospective analysis

Anesth Analg

Aspiration during anaesthesia: a computer-aided study of 185,358 anaesthetics

Acta Anaesthesiol Scand

Clinical significance of pulmonary aspiration during the perioperative period

Anesthesiology

Routine preoperative gastric emptying is seldom indicated. A study of 85,594 anaesthetics with special focus on aspiration pneumonia

Acta Anaesthesiol Scand

Perioperative pulmonary aspiration in infants and children

Anesthesiology

Reducing the risk of acid aspiration during cesarean section

Anesth Analg

Sugarless gum chewing before surgery does not increase gastric fluid volume or acidity

Can J Anaesth

The effects of chewing gum on gastric content prior to induction of general anesthesia

Anesth Analg

Original Contribution
The role of perioperative chewing gum on gastric fluid volume and gastric pH: a meta-analysis☆