Anesth Analg 2006;102:415-417
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ane.0000189218.07293.6e
PEDIATRIC ANESTHESIA
Residual Gastric Fluid Volume and Chewing Gum Before Surgery
Renate C. Schoenfelder, MD*
,
Chandra M. Ponnamma, MD*,
David Freyle, MD*,
Shu-Ming Wang, MD*, and
Zeev N. Kain, MD, MBA*
*Center for the Advancement of Perioperative Health and the Departments of Anesthesiology, Pediatrics, and Child Psychiatry, Yale University School of Medicine, New Haven, Connecticut
Address correspondence and reprint requests to Renate Schoenfelder, MD, Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8051. Address e-mail to renate.schoenfelder{at}yale.edu.
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Abstract
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In this study we sought to determine if chewing gum preoperatively increases gastric fluid volume (GFV) and changes gastric acidity. Children, 5–17 yr old, were randomized to one of three groups: a control group that was not given any gum, a group that was given sugarless bubble gum, and a group that was given sugared bubble gum. Patients in the two gum groups were instructed to chew their gum for a period of 30 min. After induction of anesthesia and tracheal intubation, the stomach was suctioned with a salem sump orogastric tube. We found that children who did not chew gum had significantly smaller GFV as compared with children who chewed sugared and sugarless gum (0.35 [0.2–0.5] mL/kg versus 0.88 [0.6–1.4] mL/kg versus 0.69 [0.4–1.6] mL/kg; P = 0.0001). Children who did not chew gum also had a significantly lower gastric fluid pH as compared with children chewing sugared and sugarless gum (geometric mean, 1.91 versus 2.25 versus 2.19; P = 0.007). We conclude that children who present for surgery while chewing gum have significantly larger GFV and higher pH.
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Introduction
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The issue of preoperative fasting is controversial and was the subject of practice guidelines published in 1999 by the American Society of Anesthesiology (ASA) (1). Several participants in a recent anesthesia conference raised the issue of children chewing gum immediately before surgery and queried how this clinical situation should be handled. That is, as the act of chewing increases oral and gastric secretions, which should alter gastric contents temporarily, one can expect the gastric fluid volume (GFV) to be increased after chewing gum.
In adults, previous studies that have addressed the issue of GFV after chewing gum have reported contradictory results (2,3). Although Dubin et al. (2) found no effect of chewing gum on GFV or acidity, Soreide et al. (3) reported increased GVF but no changes in acidity among nonsmoking adults. This question has not been addressed in children undergoing surgery. Furthermore, no studies have examined whether chewing gum with or without sugar before surgery has any impact on GFV and acidity. Thus, the hypothesis of this study is that chewing gum immediately before surgery results in a significant increase in GFV. Accordingly, we designed a randomized, controlled trial that examined the impact of gum chewing (sugared/sugarless) on GFV and pH in children undergoing surgery.
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Methods
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Children aged 5 to 17 yr, ASA physical status I–II, scheduled for elective outpatient surgical procedures were recruited for this study. The subjects followed current ASA fasting guidelines before surgery (1). Patients with a history of gastrointestinal reflux, obesity, prematurity, or developmental delay were excluded from participation in this study. No sedative premedication was given to any subject. The Yale Human Investigation Committee approved the study and informed consent was obtained from all parents. Assent was obtained from children older than 6 yr. On the day of surgery, parents and children provided written, informed consent and completed a demographic questionnaire.
Subjects were randomized into the three study groups: a control group (no gum), sugarless gum group (chewing sugarless gum: Bubble Yum Wild Strawberry sugarless, Hershey, PA) and a sugared gum group (chewing sugared gum: Bubble Yum Wild Strawberry). The randomization process was done based on a random table number that was generated by a computer. The patients in the two gum groups were instructed to chew one piece of bubble gum for a period of 30 min; length of time actually chewing gum was recorded by the researcher. Next, the gum was removed and subjects were taken to the operating room (OR). Anesthesia was induced via mask with N2O/O2 and sevoflurane, an IV cannula was placed, and all subjects underwent endotracheal intubation. Immediately afterwards, a investigator who was blinded as to group assignment suctioned the stomach based on an established and validated method with a salem sump orogastric tube (14F) at three different Trendelenburg positions (4). The volume of the gastric aspirate was measured and recorded and pH was analyzed using a Oakton pH 5 pH meter (Lazar Research Lab, Los Angeles, CA). The experimental protocol was terminated after suctioning of the stomach.
The investigators who suctioned the stomach and measured and analyzed the gastric aspirate were blinded as to group assignment. Indeed, the research assistant who conducted the randomization procedures and administrated the intervention to the child was not involved in any other aspects of the research or clinical management of the case. Furthermore, the anesthesiologists managing the case were also blinded as to group assignment.
The sample size was based on previous investigations involving gum chewing and adults (2,3). Given an effect size of 0.50 and 3 study groups, one-way analysis of variance required an N of 15 per cell to attain power of 0.85. Normally distributed data are presented as mean ± sd and skewed data are presented as median (interquartile range). Categorical data were analyzed using a 
2 test and continuous data were analyzed using one-way analysis of variance with Scheffe post hoc correction. Skewed data were analyzed using Kruskal-Wallis test and Mann-Whitney U-test. GFV was adjusted for body weight. To calculate average pH values, we used the Geometric Mean that is used to average logarithmic data. We used the SPSS 12.0 statistical package to analyze the data (SPSS, Chicago, IL). Statistical significance was accepted at 0.05.
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Results
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A total of 46 subjects between the ages of 5 and 17 yr were recruited to this study. No significant differences such as age were found in demographic characteristics among the sugarless gum, sugared gum, and control groups (11.5 ± 3.5 yr versus 9.6 ± 3.5 yr versus 11 ± 2.2 yr). Also, no significant differences were found in chewing time between the two gum chewing groups (27 ± 6 min, sugarless gum versus 31 ± 6 min, sugared gum; P = not significant).
We found that children who did not chew gum had significantly smaller GFV as compared with children who chewed sugared and sugarless gum (0.35 [0.2–0.5] mL/kg versus 0.88 [0.6–1.4] mL/kg versus 0.69 [0.4–1.6] mL/kg; P = 0.0001). Also, a significantly smaller proportion of subjects who did not chew gum had a GFV of more than 0.8 mL/kg as compared with subjects who chewed sugared and sugarless gum (6.3% versus 66.7% versus 40%; P = 0.002). Figure 1 demonstrates the GFV values of all subjects based on group assignment. Children who did not chew gum also had a significantly lower pH as compared with children in both sugared and sugarless gum groups (geometric mean 1.91 versus 2.25 versus 2.19; P = 0.007). When comparing the proportion of children in each study group who had a pH less than 2.5, no significant differences were found among the 3 groups (100% versus 87% versus 80%; P = 0.19). Post hoc analysis found no significant differences in GFV and pH between the two gum groups (P = not significant) (Table 1). No occurrence of pulmonary aspiration or other complications occurred during the induction of anesthesia in any of the children.
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Discussion
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Under the conditions of this study, which included chewing gum until the time of departure for the OR, we found a significant increase in GFV as well as higher pH. The clinical relevance of these findings, however, is unclear. To establish the clinical relevance of the findings of this report an outcome such as the actual incidence of pulmonary aspiration has to be chosen for a future randomized, controlled study. Because the incidence of pulmonary aspiration among patients undergoing anesthesia is approximately 1:10,000, a sample size of many thousands of patients is needed to examine this issue using the outcome of pulmonary aspiration (5). That is, if we assume a twofold increase in the incidence of pulmonary aspiration with a power of 85% and an alpha of 0.5, a total sample size of 6000 patients will be required. Obviously, such a large-scale study is not feasible.
In 1974 Roberts and Shirley published a report regarding acid aspiration during cesarean delivery (6). The investigators indicated in the introduction to the report that "Our preliminary work in the rhesus monkey suggests that 0.4 mL/kg is the maximum acid aspirate that does not produce significant changes in the lungs." The data that support this statement were never published in the peer-reviewed literature. Unfortunately, numerous subsequent studies considered this value of 0.4 mL/kg as a risk factor for aspiration in humans. In 1988, however, Raidoo et al. (7) found that in a primate model, the maximum acid aspirate volume that will not cause damage to the lungs is 0.8 mL/kg. This is the reason we have selected the value of 0.8 mL/kg as the cut-off value for our calculations in the Results section. A review of pediatric perioperative studies reveals that the residual GFV in children after 2 hours of clear liquids before surgery ranges from 0.24 ± 0.31 mL/kg to 0.66 ± 0.79 mL/kg (8–9). Thus, if an increased GFV was the only significant risk factor for pulmonary aspiration, then given the many children who have large GFV at the time of induction of anesthesia one would expect a substantial incidence of pulmonary aspiration. However, that is not the case. In fact, all recent studies indicate that the incidence of pulmonary aspiration under general anesthesia is only approximately 1:10,000 in children (5). Schreiner (10) addressed this issue in an editorial and advocated that gastric fluid volume is not a clear risk factor for pulmonary aspiration but is rather a surrogate outcome. That is, GFV has no clinical significance as an isolated indicator and it is likely that other risk factors and comorbidities are involved in this process.
Finally, it is important to note that this study examined only the scenario of children who chewed gum until the point of induction of anesthesia. The impact of chewing gum on GFV until 1–2 hours before surgery was not examined in this study. Also, it is unclear if the increase in GFV that we observed was attributable to increased saliva and/or gastric juice. We propose that future studies are needed to determine whether or not chewing gum should be treated as a clear liquid.
We conclude that the clinical significance of chewing gum immediately before surgery and the associated increased GFV is unclear. Furthermore, future studies need to evaluate whether chewing gum should be treated as drinking clear liquids. At the present time we can not make any recommendation whether the surgical procedures of children who present to a preoperative holding area while chewing gum should be delayed or canceled.
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Footnotes
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Accepted for publication September 9, 2005.
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References
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- Anonymous. 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: a report by the American Society of Anesthesiologist Task Force on Preoperative Fasting. Anesthesiology 1999;90:896–905.[Web of Science][Medline]
- Dubin SA, Jense HG, McCranie JM, Zubar V. Sugarless gum chewing before surgery does not increase gastric fluid volume or acidity. Can J Anaesth 1994;41:603–6.[Web of Science][Medline]
- Soreide 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;80:985–9.[Abstract]
- Cook-Sather SD, Liacouras CA, Previte JP, et al. Gastric fluid measurement by blind aspiration in pediatric patients: a gastroscopic evaluation. Can J Anaesth 1997;44:168–72.[Web of Science][Medline]
- Warner MA, Warner ME, Warner DO, et al. Perioperative pulmonary aspiration in infants and children. Anesthesiology 1999;90:66–71.[Web of Science][Medline]
- Roberts RB, Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesth Analg 1974;53:859–68.[Web of Science][Medline]
- Raidoo DM, Marszalek A, Brock-Utne JG. Acid aspiration in primates: a surprising experimental result. Anaesth Intensive Care 1988;16:375–6.[Web of Science][Medline]
- Schreiner MS. Preoperative and postoperative fasting in children. Pediatr Clin North Am 1994;41:111–21.[Web of Science][Medline]
- Schwartz DA, Connelly NR, Theroux CA, et al. Gastric contents in children presenting for upper endoscopy. Aneth Analg 1998;87:757–60.
- Schreiner M. Gastric volume: is it really a risk factor for pulmonary aspiration? Anesth Analg 1998;87:754–6.[Free Full Text]
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Abstract
Introduction
