Article

Chewing gum for 1 h does not change gastric volume in healthy fasting subjects. A prospective observational study

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Abstract

Study objective: 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. Design: Observational prospective analytical study. Setting: Bedside gastric ultrasound. Patients: 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. Interventions: Volunteers chewed gum for 1 h between the first and second assessment. Measurements: Four gastric ultrasound assessments were performed, the first one at baseline and then hourly thereafter. Main results: 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. Conclusions: 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.

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... However, there has not been a consensus on the recommendations for gum chewing preoperatively. From our study, we found that gum chewing did not significantly increase the gastric volume between the two groups (30.4+13.6 vs 29.1+11.6 ml) which was consistent with the recent findings of Valencia et al. (2019), who observed no significant effect of an increase in gastric fluid volume after one hour of gum chewing. Bouvet et al. (2017) found that gum chewing did not change gastric fluid volume two hours after ingestion of 250 ml water in 20 healthy individuals. ...
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Patients occasionally arrive in the operating suite chewing gum despite instructions to avoid oral intake for a specific number of hours before surgery. Some anaesthetists are hesitant to proceed with these patients fearing an increase in gastric volume and acidity. This study was undertaken to determine if gum chewing increased gastric volume and acidity. Seventy seven patients were recruited and informed consent obtained. Thirty-one patients who fasted overnight were randomly assigned either to serve as control (Group 1) or to chew sugarless gum prior to anaesthesia (Group 2). The remaining 46 patients fasted overnight but were given sugarless gum and allowed to chew it until immediately before induction of anaesthesia if they desired (Group 3). Volume and pH of gastric content were determined immediately after induction of anaesthesia and tracheal intubation. Results revealed mean values (range) of gastric volume for Group 1-26 ml (9-60), Group 2-40 ml (5-93), and Group 3-28 ml (4-65). Mean values for pH (range) were Group 1-1.8 (1.0-4.6), Group 2-1.6 (1.3-1.9), Group 3-1.7 (1.0-4.4). There was no difference between groups in terms of gastric volume or pH. In addition, there was no relationship between gastric content and the length of time from gum discard to induction or the length of time gum was chewed. In conclusion, the data suggest that induction of anaesthesia is safe and surgery does not need to be delayed if a patient arrives in the OR chewing sugarless gum.
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To determine if preoperative gum chewing affects gastric pH and gastric fluid volume.DesignSystematic 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.ResultsFour 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.
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Aspiration may be defined as the inhalation of material below the true vocal cords. It occurs in patients with high gastric volumes or an incompetent lower oesophageal sphincter, or in those patients whose protective airway reflexes have been lost. Patients are most at risk during induction, emergence, and in the emergency situation. Aspiration causes a chemical pneumonitis, and particulate matter may cause airway obstruction. Consequences of aspiration include atelectasis, pulmonary oedema, VQ mismatching and the development of acute respiratory disease syndrome. The clinical presentation covers a wide spectrum and is influenced by the nature, pH and volume of the aspirate. Acute management includes airway suction, oxygen therapy and securing the airway if the patient is unconscious. Bronchoscopy may be required for large foreign bodies or semi-solid material in the airway. Those patients who develop clinical sequelae within 2 hours of aspirating require admission to high-level care for further treatment. Bronchodilators and physiotherapy are appropriate treatments. Antibiotics should only be given if infected matter is inhaled or if subsequent infection develops. Steroids do not improve outcome. Severe cases will require ventilation and management in intensive care. Mortality in those who develop symptoms is about 10%.
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This guideline aims to provide an overview of the present knowledge on aspects of perioperative fasting with assessment of the quality of the evidence. A systematic search was conducted in electronic databases to identify trials published between 1950 and late 2009 concerned with preoperative fasting, early resumption of oral intake and the effects of oral carbohydrate mixtures on gastric emptying and postoperative recovery. One study on preoperative fasting which had not been included in previous reviews and a further 13 studies published since the most recent review were identified. The searches also identified 20 potentially relevant studies of oral carbohydrates and 53 on early resumption of oral intake. Publications were classified in terms of their evidence level, scientific validity and clinical relevance. The Scottish Intercollegiate Guidelines Network scoring system for assessing level of evidence and grade of recommendations was used. The key recommendations are that adults and children should be encouraged to drink clear fluids up to 2 h before elective surgery (including caesarean section) and all but one member of the guidelines group consider that tea or coffee with milk added (up to about one fifth of the total volume) are still clear fluids. Solid food should be prohibited for 6 h before elective surgery in adults and children, although 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 anaesthesia. These recommendations also apply to patients with obesity, gastro-oesophageal reflux and diabetes and pregnant women not in labour. There is insufficient evidence to recommend the routine use of antacids, metoclopramide or H2-receptor antagonists before elective surgery in non-obstetric patients, but an H2-receptor antagonist should be given before elective caesarean section, with an intravenous H2-receptor antagonist given prior to emergency caesarean section, supplemented with 30 ml of 0.3 mol l(-1) sodium citrate if general anaesthesia is planned. Infants should be fed before elective surgery. Breast milk is safe up to 4 h and other milks up to 6 h. Thereafter, clear fluids should be given as in adults. The guidelines also consider the safety and possible benefits of preoperative carbohydrates and offer advice on the postoperative resumption of oral intake.
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Aspiration of gastric contents can be a serious perioperative complication, attributing up to 9% of all anesthesia-related deaths. However, there is currently no practical, noninvasive bedside test to determine gastric content and volume in the perioperative period. The current study evaluates the feasibility of using bedside ultrasonography for assessing gastric content and volume. In the pilot phase, 18 healthy volunteers were examined to assess the gastric antrum, body, and fundus in cross-section in five prandial states: fasting and after ingestion of 250 mL of water, 500 mL of water, 500 mL of effervescent water, and a solid meal. In the phase II study, the authors concentrated on ultrasound examination of the gastric antrum in 36 volunteers for whom regression analysis was used to determine the correlation between gastric volume and antral cross-sectional area. The gastric antrum provided the most reliable quantitative information for gastric volume. The antral cross-sectional area correlated with volumes of up to 300 mL in a close-to-linear fashion, particularly when subjects were in the right lateral decubitus position. Sonographic assessment of the gastric antrum and body provides qualitative information about gastric content (empty or not empty) and its nature (gas, fluid, or solid). The fundus was the gastric area least amenable to image and measure. Our preliminary results suggest that bedside two-dimensional ultrasonography can be a useful noninvasive tool to determine gastric content and volume.
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The objectives of this study were to determine how salivary flow rate and pH vary with time during use of chewing-gums and lozenges. Twenty-four young adults collected unstimulated saliva and then, on different occasions, chewed one of six flavoured gums, or gum base, or sucked on one of two lozenges, for 20 min, during which time eight separate saliva samples were collected. Flow rate peaked during the 1st minute of stimulation with all nine products. With the lozenges, flow rate fell towards the unstimulated rate when the lozenges had dissolved. There were no significant differences in the flow rates elicited by cinnamon- or peppermint-flavoured gums or between sugar-containing or sugar-free gums. With the flavoured gums, the mean flow rate followed a power curve (r = -0.992) with time and within about 10 min was not significantly different from that when gum base was the stimulus. The initial stimulated flow rate with flavoured gums was about 10-12 times greater than the unstimulated rate (0.47 ml/min). After 20 min of chewing, it was still about 2.7 times that rate and about the same as the flow rate elicited by chewing-gum base alone. The pH of unstimulated saliva was about 6.95. With one gum containing about 1.5% organic acids, the salivary pH fell to a minimum of 6.18 in the 1st minute of stimulation, but then rose rapidly to a level above that in unstimulated saliva. With a sucrose-containing and a sucrose-free gum, the pH rose immediately on stimulation and then fell slightly with time to levels which were significantly above the pH of unstimulated saliva.
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In 15 patients, of whom 10 had a duodenal ulcer, aspirations were made of the gastric contents for one hour before and one hour after they had been chewing gum for 30 minutes. The volume and acidity was measured in each 15-min sample and the acid output was calculated. Differences between the secretion in the 3 periods were tested for significance with the Wilcoxon rank sum test for paired differences. During the chewing period the volume of gastric contents increased from 23 to 39 ml/15 min, p < 0.01, the acidity decreased from 29 to 25 meq/l, p < 0.05, and the acid output increased insignificantly (from 0.75 to 1.23 meq/15 min). The bicarbonate concentration of the saliva during chewing was on average 9 meq/l. The salivary flow during chewing was calculated to 13 ml/15 min. When the neutralization of gastric acid with salivary bicarbonate was taken into account, a significant increase in acid secretion was found during chewing. This stimulation continued during the one-hour period after chewing, causing a secretion rate of 29 ml/15 min, with an acidity of 42 meq/l and an acid output of 1.32 meq/15 min. It is concluded that although chewing gum causes a stimulation of the gastric acid secretion, this increase is so small that it does not justify an advice against the use of chewing gum in patients with duodenal ulcer or x-ray negative dyspepsia.
Article
To evaluate the effect of volume of aspirates with different pHs on mortality associated with pulmonary aspiration, hydrochloric acid solutions were injected into the tracheas of 336 Sprague-Dawley rats. The rats were divided randomly into 33 groups, were observed for 96 hr after aspiration, and were not resuscitated. Deaths were divided into two groups: early, less than 30 min after aspiration, and late, greater than 4 hr after aspiration. Late deaths, accounting for 22% of all fatalities, occurred exclusively in animals aspirating solutions with a pH less than 2.5. These late deaths indicated progressive lung damage as opposed to acute cardiorespiratory failure, which early deaths suggested. Low volume pulmonary aspirates (0.3 ml/kg) with extremely low pH (1.0) resulted in a high mortality rate (90%). Conversely, higher volume pulmonary aspirates (1.0-2.0 ml/kg) with a higher pH (greater than or equal to 1.8) resulted in a low mortality rate (14%). These data demonstrate an important interaction between pH and volume of aspirates: even low volumes have a high mortality rate if pH is very low, whereas if gastric fluid is effectively buffered, then much higher volumes than previously thought can be tolerated. This suggests that the routine use of nonparticulate antacids may be indicated in patients at risk from aspiration of stomach contents and should not be withheld because of concern of increasing gastric volume.
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To study the effects on gastric content and subjective well being of chewing gum in the immediate preoperative period, 60 female nonsmokers were randomized to use regular, sugar-free chewing gum preoperatively or to continue the overnight fast. In a similar fashion 44 habitual smokers were randomized to use nicotine gum 2 mg or not. Nonsmokers using chewing gum had significantly larger gastric fluid volumes than controls (mean 30 +/- 19 mL vs 20 +/- 15 mL; 95% confidence interval (CI) for difference 1-19 mL; P = 0.03), with no difference in gastric fluid acidity. In smokers, neither gastric fluid volume nor acidity differed significantly between those who were or were not chewing gum. Although the use of nicotine gum in smokers was associated with a reduction in dryness of the mouth, thirst, and irritability, nonsmokers chewing regular gum did not report significant improvements in patient well being. In habitual smokers unable to abstain from nicotine, the use of nicotine gum on the morning of surgery may be beneficial. Although it is difficult to prove a direct influence on the incidence of pulmonary aspiration of increased gastric contents, the fact that regular, sugar-free chewing gum increased gastric fluid volumes probably means that it should not be used on the morning of surgery.
Article
The epidemiology of aspiration pneumonia and its impact on clinical and economic outcomes in surgical patients are poorly defined. We sought to identify preoperative patient characteristics and surgical procedures that are associated with an increased risk for aspiration pneumonia and to determine the clinical and economic impact in hospitalized surgical patients. Observational study using a state discharge database. All hospitals in Maryland. We obtained discharge data for 318,880 adult surgical patients in 52 Maryland hospitals from January 1, 1999, through December 31, 2000. The primary outcome variable was a discharge diagnosis of aspiration pneumonia. Unadjusted and adjusted analyses were performed to identify patient characteristics and surgical procedures associated with an increased risk for aspiration pneumonia and to determine the impact on intensive care unit admission, in-hospital mortality, hospital length of stay, and total hospital charges. The overall prevalence of aspiration pneumonia was 0.8%. The prevalence varied among hospitals (range, 0% to 1.9%) and by surgical procedure (range, <0.1% to 19.1%). Patient characteristics independently associated with an increased risk included: male sex, nonwhite race, age of >60 yrs vs. 18-29 yrs, dementia, chronic obstructive pulmonary disease, renal disease, malignancy, moderate to severe liver disease, and emergency room admission. In patients undergoing procedures other than tracheostomy, aspiration pneumonia was independently associated with an increased risk for admission to the intensive care unit (odds ratio, 4.0; 95% confidence interval, 3.0-5.1), in-hospital mortality (odds ratio, 7.6; 95% confidence interval, 6.5-8.9), longer hospital length of stay (estimated mean increase of 9 days; 95% confidence interval, 8-10), and increased total hospital charges (estimated mean increase of 22,000 US dollars; 95% confidence interval, 19,000 US dollars-25,000 US dollars). Aspiration pneumonia occurs in approximately 1% of surgical patients and is associated with significant morbidity, mortality, and costs of care. Given that the rate of aspiration pneumonia varies among hospitals, we can improve the quality and reduce the costs of care by implementing strategies to reduce the rate of aspiration pneumonia.
Article
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.
Article
We evaluated the current incidence and outcome of perioperative pulmonary aspiration (PPA) in the nonobstetric adult population at a tertiary university medical center. A 4-yr retrospective analysis (January 2001-December 2004) was conducted using both quality improvement data and the hospital-wide medical archive recording system. PPA was defined as either detection of nonrespiratory secretions from the tracheobronchial tree or development of new pulmonary symptoms and/or new abnormalities in chest radiographs within 24 hr postoperatively. Of 99,441 anesthetics, 14 cases had confirmed PPA. Seven of them (50%) occurred in connection with gastroesophageal procedures. All patients had one or more predisposing risk factors for PPA. PPA occurred under general anesthesia in 10 patients and under monitored anesthesia care in 4 patients. In general anesthesia cases, the aspiration was recognized immediately after induction in 5 patients and occurred during changing of the endotracheal tubes in 5. The PPA was detected during the surgical procedures in all the monitored anesthesia care cases. Six patients with confirmed PPA developed pulmonary complications, of which, one died. Ten of 14 (70%) cases of PPA were the result of improper anesthesia technique. The current incidence of PPA is 1 of 7103, with morbidity 1 of 16,573 and mortality 1 of 99,441.