Chewing gum for postoperative recovery of gastrointestinal function
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
The objective of this review is to examine whether chewing gum after surgery hastens the return of gastrointestinal function. The review will consider the impact of chewing gum on indicators of bowel function (time to first passage of flatus, bowel movement and bowel sounds) and on recovery (length of hospital stay and postoperative complications). The review will also consider tolerability of chewing gum and the costs and benefits associated with using this intervention.
Background
Description of the condition
Loss of gastrointestinal function (ileus) is a common problem following abdominal surgery (Takagi 2012). Resolution of ileus is an important factor in the speed of postoperative recovery. Ileus can lead to nausea, vomiting, abdominal discomfort (Johnson 2009) and increased length of hospital stay (Schuster 2006). Factors contributing to the development and duration of ileus are associated with the surgical stress response; these include degree of bowel manipulation, level of surgical trauma and effects of postoperative modifiers such as pain management with opiates (Holte 2000; Lim 2013).
Resolution of ileus usually occurs two to five days postoperatively (Livingston 1990; Warren 2011). Approaches that have been investigated to prevent onset and reduce duration of ileus incorporate both decreasing surgical stress and optimising postoperative care. These include providing nasogastric decompression, performing minimally invasive surgery, promoting early ambulation, stopping preoperative bowel preparation, limiting intravenous fluid administration, using prokinetic agents, using epidural analgesia and reducing opiate use for pain management (Story 2009).
Early postoperative feeding is another strategy that may stimulate gut motility, reducing onset and duration of ileus (Fanning 2011). This has been incorporated into the Enhanced Recovery After Surgery (ERAS) programme employed across National Health Service (NHS) hospitals nationally. However, early postoperative feeding is not universally accepted, as it is not always well tolerated by patients. For example, vomiting and the risk of postoperative complications such as aspiration may be increased (Basaran 2009; Lewis 2001).
Description of the intervention
It has been suggested that chewing gum postoperatively may help recovery of gastrointestinal function through improved resumption of bowel activity (Lim 2013). Chewing gum replicates the process of eating without ingestion of food, so it may be a safe method of stimulating gastrointestinal function without producing additional complications associated with early feeding.
How the intervention might work
Chewing gum is a form of sham feeding that stimulates gut motility by cephalo‐vagal stimulation (Quah 2006), which in turn leads to release of gastrointestinal hormones. This intervention may provide a means to reduce the duration of postoperative ileus without the adverse effects of increased vomiting and nausea associated with early postoperative feeding. In 2002, results from a small randomised controlled trial suggested that use of chewing gum may improve postoperative recovery (Asao 2002). Since that time, a number of trials have examined the effect of chewing gum on postoperative ileus, and several have demonstrated benefits (Abd‐El‐Maeboud 2009; Ledari 2012; Marwah 2012). Serious adverse events are unlikely to occur with this intervention; many studies have reported no adverse events (Choi 2011; Husslein 2013). However incidents such as indigestion or bloating, potentially due to swallowing of air whilst chewing gum, may occur (Zaghiyan 2013).
Why it is important to do this review
Chewing gum may offer an innovative intervention for improving postoperative gastrointestinal function recovery. Earlier resolution of ileus may result in reductions in patient discomfort, complications and length of hospital stay. This could have implications for healthcare costs and patient recovery; it is therefore essential that benefits and costs are carefully evaluated. This systematic review will help to clarify available evidence on the use of chewing gum in reducing the onset and duration of ileus by improving the rate of return of postoperative gastrointestinal function.
Objectives
The objective of this review is to examine whether chewing gum after surgery hastens the return of gastrointestinal function. The review will consider the impact of chewing gum on indicators of bowel function (time to first passage of flatus, bowel movement and bowel sounds) and on recovery (length of hospital stay and postoperative complications). The review will also consider tolerability of chewing gum and the costs and benefits associated with using this intervention.
Methods
Criteria for considering studies for this review
Types of studies
We will consider all randomised controlled trials.
Types of participants
People of any age who have undergone abdominal surgery for any condition.
Types of interventions
Interventions must consist of chewing gum in the immediate postoperative recovery period and use of a control group for comparison. Studies in which the gum contains an active therapeutic agent will not be considered unless the agent is also administered to the control group without chewing gum.
Types of outcome measures
Primary outcomes
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time to first passage of flatus (hours),
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time to first bowel movement (hours).
Secondary outcomes
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length of hospital stay (days),
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time to bowel sounds (as an additional marker of return of gastrointestinal function; hours),
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reports of postoperative complications (incidence),
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tolerability of gum and costs and benefits (descriptive outcomes).
Search methods for identification of studies
Electronic searches
The following databases will be screened for eligible studies: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (via Ovid), MEDLINE (via PubMed), EMBASE (via Ovid), CINAHL (via EBSCO) and ISI Web of Science, using a combination of MeSH and key terms. The search terms include “gum”, “recovery” and “ileus” and any derivatives of those terms.
No limitation based on language or date of publication will be applied. For comprehensive search strategies, see Appendix 1 for CENTRAL; Appendix 2 for MEDLINE (via Ovid) from 1966 to present; Appendix 3 for MEDLINE (via PubMed) from 1966 to present; Appendix 4 for EMBASE (via Ovid) from 1980 to present; Appendix 5 for CINAHL (via EBSCO) from 1990 to present; and Appendix 6 for ISI Web of Science from 1900 to present.
Searching other resources
Reference lists of identified studies eligible for inclusion, previous reviews and systematic reviews will be handsearched for additional relevant studies. Proposed and ongoing trials will be sought using the following registers: clinicaltrials.gov, World Health Organization (WHO) International Clinical Trials Registry Platform and metaRegister of Controlled Trials. No date or language restrictions will be imposed. We will approach the principal investigators of identified ongoing trials that have not been published to ask for relevant data. In addition, chewing gum manufacturers (Wrigley Company, Cadbury Trebor Bassett, Lotte, Perfetti Van Melle and Hershey’s) will be contacted to ask for information on published or unpublished material on their product.
Data collection and analysis
Selection of studies
Two review authors (VS and GH) will independently examine the titles and abstracts of studies identified through the search strategy. Disagreement between review authors regarding articles for full‐text reading will be resolved by consultation with a third party (RP). Full‐text papers will be obtained for all studies that could not be excluded on the basis of title and abstract. The same review authors will then independently refine their selection by examining the selected articles and excluding those not relevant to this review. Agreement between review authors on trial inclusion will be recorded and disagreement resolved by predetermined co‐review authors (ST and SJL for clinical disputes, RP and CP for methodological disputes). Original study authors will be contacted for missing information. Decisions on all studies will be documented to permit completion of a PRISMA flow chart in the final review.
Data extraction and management
Data from each study accepted for inclusion will be extracted independently by both review authors. Review authors will be blinded to each other’s data. Data on participant demographics, participant disease status, surgical procedures, control group postoperative care and the intervention (frequency and duration of chewing gum) will be extracted using predesigned data extraction forms.
Assessment of risk of bias in included studies
Two authors (VS and GH) will independently assess the risk of bias using the criteria described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Use of power calculations and intention‐to‐treat analyses will be reported as measures of methodological quality. Once disagreements have been resolved through discussion, results from the risk of bias assessment will be presented in a table and in a summary figure. These will involve the following sources of bias and criteria.
Random sequence generation
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Low risk of bias: a random component in the sequence generation process is described, e.g. computer‐generated randomisation.
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Uncertain risk of bias: insufficient information to assess acceptability of sequence generation process.
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High risk of bias: a non‐random component in the sequence generation process is described.
Allocation concealment
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Low risk of bias: allocation could not be foreseen or affected by participants or investigators before assignment.
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Uncertain risk of bias: insufficient information to assess acceptability of allocation concealment.
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High risk of bias: allocation could be foreseen or affected by participants or investigators before assignment.
Blinding of participants and personnel
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Low risk of bias: participants and personnel adequately blinded, or lack of blinding but review authors anticipate that outcome measures are unlikely to be affected.
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Uncertain risk of bias: insufficient information to assess acceptability of blinding of participants and personnel.
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High risk of bias: no blinding of participants and personnel or blinding attempts likely to be broken, subsequently affecting outcome measures.
Blinding of outcome assessment
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Low risk of bias: outcome assessment adequately blinded, or lack of blinding but review authors anticipate that outcome measures are unlikely to be affected.
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Uncertain risk of bias: insufficient information to assess acceptability of blinding of outcome assessment.
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High risk of bias: no blinding of outcome assessment or blinding attempts likely to be broken, subsequently affecting outcome measures.
Incomplete outcome data
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Low risk of bias: no missing outcome data, explanation for missing data unlikely to be related to true outcome.
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Uncertain risk of bias: insufficient information to assess acceptability of incomplete outcome data.
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High risk of bias: explanation for missing data likely to be related to true outcome.
Selective outcome reporting
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Low risk of bias: all pre‐stated outcomes that can be confirmed by the protocol or in published reports are stated.
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Uncertain risk of bias: insufficient information to assess selectivity of outcome reporting.
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High risk of bias: not all pre‐stated outcomes are reported.
Other bias
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Low risk of bias: no additional sources of bias apparent.
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Uncertain risk of bias: insufficient information to assess other sources of bias.
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High risk of bias: at least one additional source of bias exists.
Measures of treatment effect
Outcomes will be considered as weighted mean differences (WMD) for continuous data or as risk ratios (RR) for binary data. Means, standard deviations and event rates (as relevant) will be extracted. Any information on tolerability of gum or financial burden/benefit reported in the studies will also be recorded. Time to event data will be evaluated as either hazard ratios or as per binary data provided that the status of all participants can be ascertained at a given time‐point. Hazard ratios could be used instead of risk ratios for binary data, if available and the length of follow‐up differs substantially between studies.
Unit of analysis issues
Individual participants will be used as the unit of analysis. We do not intend to include studies which use a within patient design (i.e. crossover studies).
Dealing with missing data
We will contact authors of trials to obtain missing data and will attempt to estimate data from available results. If data are still missing following these efforts, we will analyse only the available data.
Assessment of heterogeneity
Degree of statistical heterogeneity will be assessed using the I2 measurement. The condition requiring surgical treatment, surgical procedure (e.g. type of surgery such as colectomy, surgical approach such as laparoscopic or open) and postoperative care (e.g. ERAS, non‐ERAS) may influence the extent of effect of the intervention. These factors are likely to differ across studies.
Assessment of reporting biases
Potential publication bias will be assessed using a funnel plot.
Data synthesis
Analyses will be performed in RevMan 5. Results will be shown using the approach recommended in the Cochrane Handbook for Systematic Reviews of Interventions. All randomly assigned participants included will be analysed using the intention‐to‐treat principle. We anticipate a high level of heterogeneity among included studies, therefore a random effect model will be presented for the meta‐analysis of results.
Subgroup analysis and investigation of heterogeneity
Surgeries requiring more extensive bowel manipulation may result in longer duration of ileus, hence chewing gum may vary in the extent of effect. We will conduct subgroup analyses according to the anatomical surgical location. The key surgical disciplines reporting trials in this research area are colorectal surgery and caesarean section. Therefore we intend to perform analyses for three subgroups: ‘colorectal surgery’, ‘caesarean section’ and ‘other’.
Meta‐regression will be used to assess whether the overall effect size is associated with the anatomical surgical location and whether this is a source of heterogeneity between studies using the 'metareg' package for the statistical software 'Stata'. We will also consider further subgroup analyses comparing studies that apply an ERAS protocol, and those that do not.
Sensitivity analysis
We will use sensitivity analyses to examine the extent to which meta‐analysis results are sensitive to the methodological and reporting qualities of the studies analysed. As we will attempt to estimate missing data values, we will assess how robust our overall results are to these estimates by running the same meta‐analysis models with less conservative methods for dealing with missing data. We will also consider the impact of methodological quality by excluding studies of lower quality.
