This meta-analysis demonstrates that, in patients who underwent elective colorectal surgery, gum chewing significantly improved postoperative ileus by reducing the time to first flatus by 14 h, the time to first feces by 25 h, and the length of hospital stay by 26 h in comparison with standard treatment. Reductions of the time to first flatus were also observed in subgroups defined by type of colorectal disease and type of surgery.
Postoperative ileus is the delay of the resumption of normal gastrointestinal motility after surgical stress. The clinical expression includes the absence of flatus and feces transit, abdominal distension, nausea, and vomiting. Each segment of the digestive tube resumes its motility after surgery at different times. The small intestine has the shortest time of ileus (between 8 and 12 h). The stomach has a longer ileus (between 1 and 2 days), and the colon has the longest time of ileus (between 3 and 5 days).18–20
Postoperative ileus is a consequence of the interaction of several factors. Probably the most important factor is the sympathetic hyperstimulation, which inhibits gastrointestinal motility. Some neurohormones of the enteric nervous system such as substance P, vasoactive intestinal peptide, and nitric oxide can also contribute to the duration of ileus.5,19,20 Moreover, surgical aggression may stimulate the inflammatory cascade with liberation of interleukins (IL-6, IL-1b) and chemokines (MCP-1, ICAM-1), which further inhibit gastrointestinal motility.19,20 Some drugs may also contribute to postoperative ileus. For instance, anesthetic drugs such as atropine, halothane, and enflurane may have a transitory effect, while opioid analgesics used during surgery and in the postoperative period may have a more prolonged effect.21–23
After surgery the myoelectric activity of the gastrointestinal tract is disorganized and this is translated into lack of propulsion. The electrical activity of the colon is the last to recover. Colon motility is diminished or absent until approximately the third postoperative day. At the fourth day, the colonic electrical activity consists of disorganized bursts, and later, a coordinated motor response is able to propagate. This allows the passage of flatus, the first indicator of the ileus resolution process. The passage of feces occurs within 1 or 2 days after the first flatus, and it does not necessarily mean the final resolution of the ileus. The passage of feces depends on the type of surgical procedure, the condition and content of the intestine prior to surgery, dietetic factors, and the usual intestinal frequency of the patient.5,20,21
Shortening of hospital stay by almost 26 h with gum chewing in comparison to standard care is translated into better well-being of patients, early return to the preoperative functional status, and especially, reduction of hospital costs.24–26 To our knowledge, there are no specific studies evaluating the reduction of costs by using gum chewing in patients undergoing colorectal surgery. Additional advantages of gum chewing include stimulation of appetite and sensation of well-being during the postoperative period.
Two decades ago, it was described that replication of the cephalic phase of digestion through sham feeding stimulated the electrical, motor, and secretory activities of the gastrointestinal tract through neurohormonal and vagal pathways. In humans, sham feeding produces a significant increase of gastrin and neurotensin release and a partial alteration of the myoelectrical pattern of the gastrointestinal tract during fasting, also known as interdigestive migrating motor complex. Gum chewing is a type of sham feeding and was lately proposed as an activator of these various mechanisms.27,28
An open colorectal surgery has a more prolonged postoperative ileus than a laparoscopic-assisted colorectal surgery, probably due to a longer visceral manipulation and environmental exposure and higher use of analgesic drugs to control postoperative pain.29–31 We found that gum chewing especially benefited patients who underwent open surgery. Gum chewing can also extend the benefits of the minimally invasive laparoscopic surgery.8 Moreover, the larger benefit of gum chewing in the subgroup that included patients with colorectal cancer alone can be important, given that these patients usually have a moderate to bad nutritional state and a shorter hospitalization can avoid in-hospital complications.32,33
Our meta-analysis is different than two recently published meta-analyses14,15 in several ways. Our meta-analysis included six trials with 244 patients, 50% more patients than the other studies (five trials, n = 158). We did not restrict the language of the studies; one of the other studies focused on English language studies.14 The period of our systematic review was until August 2008, longer than the other periods (January 200714 and July 200615). Finally, we focused on randomized controlled trials, not on nonrandomized comparative studies.14
Multimodal fast-track perioperative care programs in colorectal surgery are oriented to a fast recovery of patients, as well as to a shortened hospital stay. These programs include: adequate patient information about specific procedures, no bowel preparation, no sedative premedication, intake of small quantities of carbohydrate-enriched liquids within 2 h before surgery, epidural thoracic analgesia and short half-life anesthetics, restriction of intravenous perioperative fluids, use of minimally invasive surgery, use of nonopioid systemic analgesic drugs, avoidance of the routine use of drainages or nasogastric tube, early withdrawal of urinary probe, early intake of small quantities of liquid, and early deambulation. All these measures have demonstrated favorable results such as shorter hospitalization, better patient comfort, reduction of in-hospital mortality, and reduction of postoperative costs.1–3,34 Gum chewing should become part of the multimodal fast-track perioperative care program in colorectal surgery.
It is not known whether gum chewing also has a favorable effect in postoperative ileus in abdominopelvic surgery, such as transperitoneal aortic surgery,35 cesarean section, hysterectomy with abdominal access,36 and radical cystectomy.37,38
Our study has some limitations. First, the total number of patients (n = 244) included in the meta-analysis was relatively small. However, this meta-analysis is the largest available meta-analysis that adds about 90 patients more than recently published meta-analyses.14,15 We performed a formal systematic review of all clinical trials published until August 1, 2008 and our analysis did not show evidence of publication bias. Second, we did not have access to original source data (i.e., individual patient data) for any of these clinical trials. Thus, we based the analysis on available data from published studies or directly from authors. Third, clinical trials included in the meta-analysis can be regarded as poorly controlled as far as use of opiates and other analgesics, postoperative feeding, epidural analgesia, fast-track, or other standard and nonstandard protocols. However, those controls reflected what authors considered their current clinical practice. We expect that a tightly controlled randomized trial will show a smaller clinical effect. Fourth, a meta-analysis may be considered less convincing than a large prospective trial designed to assess the outcome of interest. However, given the lack of an appropriately sized clinical trial evaluating gum chewing for postoperative ileus in colorectal surgery, a well-designed and well-performed meta-analysis is the best option available to answer this clinical question