Abstract: We included 128 trials with 8754 participants in the review, and 94 trials with 5846 participants in the analysis. Trials included in the review were funded as follows: charity (n = 19), departmental resources (n = 8), governmental sources (n = 15) and industry (in part or in total) (n = 15). The source of funding was not specified for the other studies. Results of 22 trials including 1138 participants show that an epidural containing a local anaesthetic will decrease the time required for return of gastrointestinal transit as measured by time to first flatus after an abdominal surgery (standardized mean difference (SMD) -1.28, 95% confidence interval (CI) -1.71 to -0.86; high quality of evidence; equivalent to 17.5 hours). The effect is proportionate to the concentration of local anaesthetic used. A total of 28 trials including 1559 participants reported a decrease in time to first faeces (stool) (SMD -0.67, 95% CI -0.86 to -0.47; low quality of evidence; equivalent to 22 hours). Thirty-five trials including 2731 participants found that pain on movement at 24 hours after surgery was also reduced (SMD -0.89, 95% CI -1.08 to -0.70; moderate quality of evidence; equivalent to 2.5 on scale from 0 to 10). From findings of 22 trials including 1154 participants we did not find a difference in the incidence of vomiting within 24 hours (risk ratio (RR) 0.84, 95% CI 0.57 to 1.23; low quality of evidence). From investigators in 17 trials including 848 participants we did not find a difference in the incidence of gastrointestinal anastomotic leak (RR 0.74, 95% CI 0.41 to 1.32; low quality of evidence). Researchers in 30 trials including 2598 participants noted that epidural analgesia reduced length of hospital stay for an open surgery (SMD -0.20, 95% CI -0.35 to -0.04; very low quality of evidence; equivalent to one day). Data on costs were very limited. An epidural containing a local anaesthetic, with or without the addition of an opioid, accelerates the return of gastrointestinal transit (high quality of evidence). An epidural containing a local anaesthetic with an opioid decreases pain after abdominal surgery (moderate quality of evidence). We did not find a difference in the incidence of vomiting or anastomotic leak (low quality of evidence). For open surgery, an epidural containing a local anaesthetic would reduce the length of hospital stay (very low quality of evidence).

Plain-language summary: We included 128 trials with 8754 participants of both sexes aged between 33 and 76 years in the review and 94 trials with 5846 participants in the analysis. Three trials reported that their trial was officially registered. Trials included in the review were funded as follows: charity (n = 19), departmental resources (n = 8), governmental sources (n = 15) and industry (in part or in total) (n = 15). The source of funding was not specified for the other trials. We found that an epidural containing a local anaesthetic reduces the time required for return of gut function compared with an opioid-based regimen (equivalent to 17 hours). An epidural providing a local anaesthetic and an opioid also reduce pain (equivalent to a reduction of 2.5 on a scale from 0 to 10 for pain on movement at 24 hours after surgery) and time spent in hospital for open surgery (equivalent to one day). We found no evidence that an epidural with a local anaesthetic would affect the incidence of vomiting or poor healing of the gut. We rated the quality of the evidence as high for return of gastrointestinal function, moderate for pain treatment, low for no effect on vomiting or healing of the gut and very low for reduced time spent in the hospital after open surgery.