Selective postoperative inhibition of gastrointestinal opioid receptors

Analgesic and Gastrointestinal Effects of Morphine in Equines

Morphine has significant clinical and analgesic effects in horses, but its impact on the gastrointestinal tract requires further understanding. This study assessed the analgesic and gastrointestinal effects of morphine in horses undergoing elective orchiectomy in the quadrupedal position. Thirty uncastrated male horses were randomly assigned to three groups: orchiectomy without morphine and sedation protocol (OSM), orchiectomy with morphine and sedation protocol (OM), and administration of morphine alone in the absence of orchiectomy (M). The anesthetic protocol involved acepromazine (0.05 mg/kg IV) and detomidine (10 mcg/kg IV) sedation in groups OSM and OM, with morphine sulfate (0.05 mg/kg IV) given to OM and M, and NaCl to OSM. The team measured clinical parameters, pain, and sedation using the EQUUS-FAP scale, while they monitored bowel motility and gastric dilation through abdominal ultrasound. These assessments were performed on the previous day (m1), 20 min before surgery (m2), and at various time points following the administration of morphine or saline solution: one hour (m3), two hours (m4), four hours (m5), six hours (m6), and eight hours (m7) post-procedure for all three groups. There was no significant difference in pain score between OSM and OM, though OM had better sedation. Ultrasound revealed decreased colon contractions and minor gastric dilation in OSM and OM, normalizing within 6 h. Group M showed reduced motility and significant gastric dilation lasting 8 h. In conclusion, while morphine enhanced sedation without causing greater gastrointestinal dysfunction than OSM, its administration alone resulted in a more pronounced reduction in gastrointestinal motility and an increased risk of gastric dilation.

The effect of intraoperative low-dose ketamine versus dexmedetomidine infusion on postoperative bowel recovery in patients undergoing gastrointestinal malignancy surgeries: Placebo-controlled, randomized trial

Background and Aims

No studies have compared the effects of ketamine and dexmedetomidine on bowel recovery. We evaluated the effects of intraoperative low-dose ketamine or dexmedetomidine infusion on postoperative bowel recovery in patients undergoing gastrointestinal (GI) malignancy surgeries.

Material and Methods

This placebo-controlled, randomized study was carried out in 84 American Society of Anesthesiologists II patients, aged 18-70 years, of either gender, undergoing elective open GI malignancy surgeries. Patients received intraoperative infusion of ketamine @ 0.1 mg kg-1 h-1 (KET), dexmedetomidine @ 0.25 μg kg-1 h-1 (DEX), or normal saline (placebo). Primary outcome was the time to first flatus and/or stool. Secondary outcomes included time to extubation, total analgesic requirement, postoperative pain scores, time to feeds, duration of intensive care unit (ICU) and hospital stay, and the incidence of adverse events. Continuous data were analyzed by the one-way analysis of variance (ANOVA) or the Kruskal-Wallis test. Categorical data were analyzed by the Chi-square test or the Fisher's exact test.

Results

Median time to passage of flatus and/or stool was 3 [interquartile range (IQR) 2-3] days in the KET group, 2 [IQR 2-3] days in the DEX group, and 2 [IQR 2-3] days in the placebo group (P = 0.53 for placebo vs. KET, 0.81 for placebo vs. DEX, and 0.99 for KET vs. DEX). Pain scores and analgesic consumption were significantly less in the intervention groups versus placebo (P < 0.001). No difference was seen in other secondary outcomes.

Conclusion

Low-dose ketamine or dexmedetomidine did not result in early bowel recovery despite lower pain scores and opioid consumption in patients undergoing open GI malignancy surgeries.

Alvimopan for postoperative ileus following abdominal surgery: a systematic review

BACKGROUND

Postoperative ileus (POI) is a common complication following abdominal surgery, often leading to extended hospital stays and a higher risk of post-operative complications, leading to poorer patient outcomes. Alvimopan, a peripherally acting µ-opioid receptor antagonist, has been shown to aid in the recovery of normal bowel function after surgery. While its benefits are well-established in open abdominal surgeries, its efficacy in laparoscopic procedures had not been conclusively determined. However, recent clinical trials involving laparoscopic surgeries have since been conducted. This review aims to reassess the efficacy of Alvimopan by incorporating findings from these new studies, potentially providing further insight into its clinical benefits.

METHODS

A comprehensive search of PubMed, Google Scholar, EMBASE, and the Cochrane Library was conducted. Studies were included based on the PICO framework, focusing on Alvimopan's impact on postoperative gastrointestinal recovery. Primary outcomes were time to gastrointestinal function recovery (GI-3) and hospital stay duration.

RESULTS

Ten studies met the inclusion criteria, with seven focusing on the use of Alvimopan in open abdominal surgeries and three in laparoscopic procedures. Collectively, these studies involved 18,822 patients undergoing various types of abdominal Administration of Alvimopan 6 mg accelerated gastrointestinal function recovery by an average of 14 h (Hazard ratio: 1.62, p = 0.002) and reduced hospital stays by 5.2 h (Hazard ratio: 1.52, p = 0.04) compared to placebo. Similarly, Alvimopan 12 mg reduced GI-3 recovery time by 13.5 h (Hazard ratio: 1.58, p = 0.02) and hospital stay duration by 6.2 h (Hazard ratio: 1.46, p = 0.018).

CONCLUSION

Alvimopan shows promise in reducing POI and hospital stay durations following abdominal surgeries. The incorporation of the recent studies in laparoscopic abdominal procedures further supports these findings. Integrating Alvimopan into perioperative care protocols may enhance patient outcomes and help lower healthcare costs.

Early versus delayed oral feeding after major gynaecologic surgery

BACKGROUND

This is an updated and expanded version of the original Cochrane review, first published in 2014. Postoperative oral intake is traditionally withheld after major abdominal gynaecologic surgery until the return of bowel function. The concern is that early oral intake will result in vomiting and severe paralytic ileus, with subsequent aspiration pneumonia, wound dehiscence, and anastomotic leakage. However, clinical studies suggest that there may be benefits from early postoperative oral intake. Currently, gynaecologic surgery can be performed through various routes: open abdominal, vaginal, laparoscopic, robotic, or a combination. In this version, we included women undergoing major gynaecologic surgery through all of these routes, either alone or in combination.

OBJECTIVES

To assess the effects of early versus delayed (traditional) initiation of oral intake of food and fluids after major gynaecologic surgery.

SEARCH METHODS

On 13 June 2023, we searched the Cochrane Gynaecology and Fertility Group's Specialised Register, CENTRAL, MEDLINE, Embase, the citation lists of relevant publications, and two trial registries. We also contacted experts in the field for any additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared the effect of early versus delayed initiation of oral intake of food and fluids after major gynaecologic surgery, performed by abdominal, vaginal, laparoscopic, and robotic approaches. Early feeding was defined as oral intake of fluids or food within 24 hours post-surgery, regardless of the return of bowel function. Delayed feeding was defined as oral intake after 24 hours post-surgery, and only after signs of postoperative ileus resolution. Primary outcomes were: postoperative ileus, nausea, vomiting, cramping, abdominal pain, bloating, abdominal distension, need for postoperative nasogastric tube, time to the presence of bowel sounds, time to the first passage of flatus, time to the first passage of stool, time to the start of a regular diet, and length of postoperative hospital stay. Secondary outcomes were: infectious complications, wound complications, deep venous thrombosis, urinary tract infection, pneumonia, satisfaction, and quality of life.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed the risk of bias, and extracted the data. We calculated the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous data. We examined continuous data using the mean difference (MD) and a 95% CI. We tested for heterogeneity between the results of different studies using a forest plot of the meta-analysis, the statistical tests of homogeneity of 2 x 2 tables, and the I² value. We assessed the certainty of the evidence using GRADE methods.

MAIN RESULTS

We included seven randomised controlled trials (RCTs), randomising 902 women. We are uncertain whether early feeding compared to delayed feeding has an effect on postoperative ileus (RR 0.49, 95% CI 0.21 to 1.16; I² = 0%; 4 studies, 418 women; low-certainty evidence). We are uncertain whether early feeding affects nausea or vomiting, or both (RR 0.94, 95% CI 0.66 to 1.33; I² = 67%; random-effects model; 6 studies, 742 women; very low-certainty evidence); nausea (RR 1.24, 95% CI 0.51 to 3.03; I² = 74%; 3 studies, 453 women; low-certainty evidence); vomiting (RR 0.83, 95% CI 0.52 to 1.32; I² = 0%; 4 studies, 559 women; low-certainty evidence), abdominal distension (RR 0.99, 95% CI 0.75 to 1.31; I² = 0%; 4 studies, 559 women; low-certainty evidence); need for postoperative nasogastric tube placement (RR 0.46, 95% CI 0.14 to 1.55; 3 studies, 453 women; low-certainty evidence); or time to the presence of bowel sounds (MD -0.20 days, 95% CI -0.46 to 0.06; I² = 71%; random-effects model; 3 studies, 477 women; low-certainty evidence). There is probably no difference between the two feeding protocols for the onset of flatus (MD -0.11 days, 95% CI -0.23 to 0.02; I² = 9%; 5 studies, 702 women; moderate-certainty evidence). Early feeding probably results in a slight reduction in the time to the first passage of stool (MD -0.18 days, 95% CI -0.33 to -0.04; I² = 0%; 4 studies, 507 women; moderate-certainty evidence), and may lead to a slightly sooner resumption of a solid diet (MD -1.10 days, 95% CI -1.79 to -0.41; I² = 97%; random-effects model; 3 studies, 420 women; low-certainty evidence). Hospital stay may be slightly shorter in the early feeding group (MD -0.66 days, 95% CI -1.17 to -0.15; I² = 77%; random-effects model; 5 studies, 603 women; low-certainty evidence). The effect of the two feeding protocols on febrile morbidity is uncertain (RR 0.96, 95% CI 0.75 to 1.22; I² = 47%; 3 studies, 453 women; low-certainty evidence). However, infectious complications are probably less common in women with early feeding (RR 0.20, 95% CI 0.05 to 0.73; I² = 0%; 2 studies, 183 women; moderate-certainty evidence). There may be no difference between the two feeding protocols for wound complications (RR 0.82, 95% CI 0.50 to 1.35; I² = 0%; 4 studies, 474 women; low-certainty evidence), or pneumonia (RR 0.35, 95% CI 0.07 to 1.73; I² = 0%; 3 studies, 434 women; low-certainty evidence). Two studies measured participant satisfaction and quality of life. One study found satisfaction was probably higher in the early feeding group, while the other study found no difference. Neither study found a significant difference between the groups for quality of life (P > 0.05).

AUTHORS' CONCLUSIONS

Despite some uncertainty, there is no evidence to indicate harmful effects of early feeding following major gynaecologic surgery, measured as postoperative ileus, nausea, vomiting, or abdominal distension. The potential benefits of early feeding include a slightly faster initiation of bowel movements, a slightly sooner resumption of a solid diet, a slightly shorter hospital stay, a lower rate of infectious complications, and a higher level of satisfaction.

Pharmacologic prevention and therapy of postoperative paralytic ileus after gastrointestinal cancer surgery: systematic review and meta-analysis

BACKGROUND

Postoperative paralytic ileus (POI) is a significant concern following gastrointestinal tumor surgery. Effective preventive and therapeutic strategies are crucial but remain elusive. Current evidence from randomized-controlled trials on pharmacological interventions for prevention or treatment of POI are systematically reviewed to guide clinical practice and future research.

MATERIALS AND METHODS

Literature was systematically searched for prospective randomized-controlled trials testing pharmacological interventions for prevention or treatment of POI after gastrointestinal tumor surgery. Meta-analysis was performed using a random effects model to determine risk ratios and mean differences with 95% CI. Risk of bias and evidence quality were assessed.

RESULTS

Results from 55 studies, involving 5078 patients who received experimental interventions, indicate that approaches of opioid-sparing analgesia, peripheral opioid antagonism, reduction of sympathetic hyperreactivity, and early use of laxatives effectively prevent POI. Perioperative oral Alvimopan or intravenous administration of Lidocaine or Dexmedetomidine, while safe regarding cardio-pulmonary complications, demonstrated effectiveness concerning various aspects of postoperative bowel recovery [Lidocaine: -5.97 (-7.20 to -4.74)h, P <0.0001; Dexmedetomidine: -13.00 (-24.87 to -1.14)h, P =0.03 for time to first defecation; Alvimopan: -15.33 (-21.22 to -9.44)h, P <0.0001 for time to GI-2 ] and length of hospitalization [Lidocaine: -0.67 (-1.24 to -0.09)d, P =0.02; Dexmedetomidine: -1.28 (-1.96 to -0.60)d, P =0.0002; Alvimopan: -0.58 (-0.84 to -0.32)d, P <0.0001] across wide ranges of evidence quality. Perioperative nonopioid analgesic use showed efficacy concerning bowel recovery as well as length of hospitalization [-1.29 (-1.95 to -0.62)d, P =0.0001]. Laxatives showed efficacy regarding bowel movements, but not food tolerance and hospitalization. Evidence supporting pharmacological treatment for clinically evident POI is limited. Results from one single study suggest that Neostigmine reduces time to flatus and accelerates bowel movements [-37.06 (-40.26 to -33.87)h, P <0.0001 and -42.97 (-47.60 to -38.35)h, P <0.0001, respectively] with low evidence quality.

CONCLUSION

Current evidence concerning pharmacological prevention and treatment of POI following gastrointestinal tumor surgery is limited. Opioid-sparing concepts, reduction of sympathetic hyperreactivity, and laxatives should be implemented into multimodal perioperative approaches.

Improved Postoperative Pain Management Outcomes After Implementation of Enhanced Recovery After Surgery (ERAS) Protocol for Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy (CRS-HIPEC)

BACKGROUND

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) for patients with peritoneal carcinomatosis is promising but has potential for significant morbidity and prolonged hospitalization. Enhanced Recovery After Surgery (ERAS) is a standardized protocol designed to optimize perioperative care. This study describes trends in epidural and opioid use after implementing ERAS for CRS-HIPEC at a tertiary academic center.

METHODS

A retrospective analysis of patients undergoing CRS-HIPEC from January 2020 to September 2023 was conducted. ERAS was implemented in February 2022. Medication and outcomes data were compared before and after ERAS initiation. All opioids were converted to morphine milligram equivalents (MMEs).

RESULTS

A total of 136 patients underwent CRS-HIPEC: 73 (54%) pre- and 63 (46%) post-ERAS. Epidural usage increased from 63% pre-ERAS to 87% post-ERAS (p = 0.001). Compared with those without epidurals, patients with epidurals had decreased total 7-day oral and intravenous (IV) opioid requirements (45 MME vs. 316 MME; p < 0.001). There was no difference in 7-day opioid totals between pre- and post-ERAS groups. After ERAS, more patients achieved early ambulation (83% vs. 53%; p < 0.001), early diet initiation (81% vs. 25%; p < 0.001), and early return of bowel function (86% vs. 67%; p = 0.012).

CONCLUSIONS

ERAS implementation for CRS-HIPEC was associated with increased epidural use, decreased oral and IV opioid use, and earlier bowel function return. Our study demonstrates that epidural analgesia provides adequate pain control while significantly decreasing oral and IV opioid use, which may promote gastrointestinal recovery postoperatively. These findings support the implementation of an ERAS protocol for effective pain management in patients undergoing CRS-HIPEC.

Effect evaluation of different preventive measures for ileus after abdominal operation: A systematic review and network meta-analysis

Background

Different approaches to the prevention of postoperative ileus have been evaluated in numerous randomized controlled trials. This network meta-analysis aimed to investigate the relative effectiveness of different interventions in preventing postoperative ileus.

Methods

Randomized controlled trials (RCTS) on the prevention of postoperative ileus were screened from Chinese and foreign medical databases and compared. STATA software was used for network meta-analysis using the frequency method. Random-effects network meta-analysis was also used to compare all schemes directly and indirectly.

Results

A total of 105 randomized controlled trials with 18,840 participants were included in this report. The results of the network meta-analysis showed that intravenous analgesia was most effective in preventing the incidence of postoperative ileus, the surface under the cumulative ranking curve (SUCRA) is 90.5. The most effective intervention for reducing the first postoperative exhaust time was postoperative abdominal mechanical massage (SUCRA: 97.3), and the most effective intervention for reducing the first postoperative defecation time was high-dose opioid antagonists (SUCRA: 84.3). Additionally, the most effective intervention for reducing the time to initiate a normal diet after surgery was accelerated rehabilitation (SUCRA: 85.4). A comprehensive analysis demonstrated the effectiveness and prominence of oral opioid antagonists and electroacupuncture (EA) combined with gum.

Conclusion

This network meta-analysis determined that oral opioid antagonists and EA combined with chewing gum are the most effective treatments and optimal interventions for reducing the incidence of postoperative ileus. However, methods such as abdominal mechanical massage and coffee require further high-quality research.

Postoperative ileus after digestive surgery: Network meta-analysis of pharmacological intervention

AIMS

Several medicinal treatments for avoiding postoperative ileus (POI) after abdominal surgery have been evaluated in randomized controlled trials (RCTs). This network meta-analysis aimed to explore the relative effectiveness of these different treatments on ileus outcome measures.

METHODS

A systematic literature review was performed to identify RCTs comparing treatments for POI following abdominal surgery. A Bayesian network meta-analysis was performed. Direct and indirect comparisons of all regimens were simultaneously compared using random-effects network meta-analysis.

RESULTS

A total of 38 RCTs were included in this network meta-analysis reporting on 6371 patients. Our network meta-analysis shows that prokinetics significantly reduce the duration of first gas (mean difference [MD] = 16 h; credible interval -30, -3.1; surface under the cumulative ranking curve [SUCRA] 0.418), duration of first bowel movements (MD = 25 h; credible interval -39, -11; SUCRA 0.25) and duration of postoperative hospitalization (MD -1.9 h; credible interval -3.8, -0.040; SUCRA 0.34). Opioid antagonists are the only treatment that significantly improve the duration of food recovery (MD -19 h; credible interval -26, -14; SUCRA 0.163).

CONCLUSION

Based on our meta-analysis, the 2 most consistent pharmacological treatments able to effectively reduce POI after abdominal surgery are prokinetics and opioid antagonists. The absence of clear superiority of 1 treatment over another highlights the limits of the pharmacological principles available.

The Problem of Appetite Loss After Major Abdominal Surgery: A Systematic Review

OBJECTIVE

To systematically review the problem of appetite loss after major abdominal surgery.

SUMMARY OF BACKGROUND DATA

Appetite loss is a common problem after major abdominal surgery. Understanding of etiology and treatment options is limited.

METHODS

We searched Medline, Cochrane Central Register of Controlled Trials, and Web of Science for studies describing postoperative appetite loss. Data were extracted to clarify definition, etiology, measurement, surgical influence, pharmacological, and nonpharmacological treatment. PROSPERO registration ID: CRD42021224489.

RESULTS

Out of 6144 articles, we included 165 studies, 121 of which were also analyzed quantitatively. A total of 19.8% were randomized, controlled trials (n = 24) and 80.2% were nonrandomized studies (n = 97). The studies included 20,506 patients undergoing the following surgeries: esophageal (n = 33 studies), gastric (n = 48), small bowel (n = 6), colon (n = 27), rectal (n = 20), hepatobiliary (n = 6), and pancreatic (n = 13). Appetite was mostly measured with the Quality of Life Questionnaire of the European Organization for Research and Treatment of Cancer (EORTC QLQ C30, n = 54). In a meta-analysis of 4 randomized controlled trials gum chewing reduced time to first hunger by 21.2 hours among patients who had bowel surgery. Other reported treatment options with positive effects on appetite but lower levels of evidence include, among others, intravenous ghrelin administration, the oral Japanese herbal medicine Rikkunshito, oral mosapride citrate, multidisciplin-ary-counseling, and watching cooking shows. No studies investigated the effect of well-known appetite stimulants such as cannabinoids, steroids, or megestrol acetate on surgical patients.

CONCLUSIONS

Appetite loss after major abdominal surgery is common and associated with increased morbidity and reduced quality of life. Recent studies demonstrate the influence of reduced gastric volume and ghrelin secretion, and increased satiety hormone secretion. There are various treatment options available including level IA evidence for postoperative gum chewing. In the future, surgical trials should include the assessment of appetite loss as a relevant outcome measure.

Complete opioid transition to sublingual Buprenorphine after abdominal surgery is associated with significant reductions in opioid requirements, but not reduction in hospital length of stay: a retrospective cohort study

Background

The use of sublingual buprenorphine (SLBup) for acute pain after major abdominal surgery may offer the potential advantages of unique analgesic properties and more reliable absorption during resolving ileus. We hypothesized that complete opioid transition to SLBup rather than oral oxycodone (OOxy) in the early postoperative period after major abdominal surgery would reduce hospital length of stay, and acute pain and total OMEDD (Oral Morphine Equivalent Daily Dose) requirements in the first 24 h from post-parenteral opioid transition.

Methods

We reviewed 146 patients who had undergone elective and emergency abdominal surgery under our quaternary referral centre’s Upper Gastro-Intestinal and Colo-Rectal Surgical Units 6 months before and after the introduction of complete postoperative transition to sublingual buprenorphine, rather than oral oxycodone, in July 2017. Our primary endpoint was 24-hourly post-transition OMEDDs; secondary endpoints were 24-hourly post-transition Mean NRS-11 pain scores on movement (POM) and length of hospital stay (LOS). Univariate analysis and linear multivariate regression analyses were used to quantify effect size and identify surgical, patient & other analgesic factors associated with these outcome measures.

Results

Patients transitioning to SLBup had reduced 24-hourly post-transition OMEDD requirements on postoperative day 2 (POD) (26 mg less, p = 0.04) and NRS-11 POM at POD1 (0.7 NRS-11 units less, p = 0.01). When adjusting for patient, surgical and special analgesic factors, SLBup was associated with a similar reduction in OMEDDs (Unstandardised beta-coefficient -26 mg, p = 0.0001), but not NRS-11 POM (p = 0.47) or hospital LOS (p = 0.16).

Conclusions

Our change of practice from use of OOxy to SLBup as primary transition opioid from patient-controlled analgesia delivered full opioid agonists was associated with a clinically significant decrease in 24-hourly post-parenteral opioid transition OMEDDs and improved NRS-11 POM, but without an association with hospital LOS after major abdominal surgery. Further prospective randomized work is required to confirm these observed associations and impact on other important patient-centred outcomes.

Postoperative Ileus: a Pharmacological Perspective

Post-operative ileus (POI) is a frequent complication after abdominal surgery. The consequences of POI can be potentially serious such as bronchial inhalation or acute functional renal failure. Numerous advances in peri-operative management, particularly early rehabilitation, have made it possible to decrease POI. Despite this, the rate of prolonged POI ileus remains high and can be as high as 25% of patients in colorectal surgery. From a pathophysiological point of view, POI has two phases, an early neurological phase and a later inflammatory phase, to which we could add a "pharmacological" phase during which analgesic drugs, particularly opiates, play a central role. The aim of this review article is to describe the phases of the pathophysiology of POI, to analyse the pharmacological treatments currently available through published clinical trials and finally to discuss the different research areas for potential pharmacological targets.

Design and feasibility of a double-blind, randomized trial of peri-operative methylnaltrexone for postoperative ileus prevention after adult spinal arthrodesis

BACKGROUND

Postoperative ileus (POI) is a common complication with no proven prophylactic measures in place. While perioperative opioid use has been implicated in POI development, current treatments fail to target this disease mechanism. Methylnaltrexone (MNTX) has been used to prevent the effects of opioids on the bowel and could reduce the incidence of POI when administered preoperatively.

METHODS

In this phase IIb randomized controlled trial, we assessed the effect of perioperative MNTX on time-to-first-bowel movement following spinal arthrodesis surgeries.

RESULTS

82 patients were randomly selected in a 1:1 ratio to be included in either the treatment or placebo groups. Comparison of relevant factors of included patients to patients who refused to participate (n = 21) and to a prior retrospective series (n = 241) revealed no differences in age, male sex, liver disease, and number of surgical levels. Overall treatment fidelity (98% adherence) and retention (100% at one-month follow-up) were high. The predicted POI incidence (9.3-11.1%) was also equivalent to a prior retrospective series. However, the overall observed POI incidence (3.7%) was lower than expected, which could reflect a superimposed 'trial effect' related to standardized care in a research setting.

CONCLUSIONS

Since exposure to significant opioid doses represents a barrier to enhanced recovery after surgery, the results of this innovative trial may provide further guidance for the peri-operative use of opioid-receptor blockers. Here, we show that MNTX can be effectively administered in the peri-operative period with appropriate follow-up achieved in a representative population of patients undergoing spinal surgery.

TRIAL REGISTRATION NUMBERS

Clinicaltrials.gov - NCT03852524 and Institutional Review Board - 2018H0260.

Association of Abdominal Incision Length With Gastrointestinal Function Recovery Post-operatively: A Multicenter Registry System-Based Retrospective Cohort Study

Objective: To evaluate the influence of the abdominal incision length on the gastrointestinal function recovery post-operatively.

Background: Gut motility recovers more quickly after the minimally invasive laparoscopic surgery compared than after the traditional open surgery; however, whether the minimal abdominal incision contributes to the faster gut motility recovery is controversial and lacks solid clinical evidence.

Methods: A registry-based secondary cohort analysis was conducted to evaluate the association between the abdominal incision length and gut motility recovery post-operatively based on a multicenter, prospective, and observational study of the prolonged post-operative ileus (PPOI) incidence and the risk factors in the patients with the major abdominal surgery. The incision length, in the centimeters, was the exposure. The primary outcome measures were the PPOI incidence and its association with the incision length. The secondary outcome included the days to the first passage of flatus and the days to the first passage of stool.

Results: Overall, 1,840 patients, including 287 (15.7%) patients with the PPOI, were recruited. The PPOI incidence was 17.6% and 13.3% in the long-incision (>18 cm) and short-incision patients ( ≤ 18 cm), respectively. The incidence of the PPOI increased by 1.1% (1.0–1.1) by each centimeter increment of the incision length after adjusting for the confounding factors. In comparison to the short-incision patients, the long-incision patients had prolonged passage of stool (4.46 vs. 4.95 days, p < 0.001). Each centimeter increment of the incision length contributed to a 2% increased risk of delay in the first bowel movement [hazard ratio (HR) 0.980 (0.967, 0.994)].

Conclusion: A long abdominal incision length independently contributed to the prolonged gut function recovery post-operatively mainly by delaying the time to the first bowel movement, but not influencing the time to first passage of flatus.

The effect of perioperative dexmedetomidine on postoperative bowel function recovery in adult patients receiving general anaesthesia: a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Dexmedetomidine has opioid sparing actions but its effect on bowel recovery is controversial. Primary aim of this review was to evaluate the effect of perioperative dexmedetomidine on postoperative bowel recovery. Secondary aim was to evaluate the effect of dexmedetomidine on hospital discharge.

EVIDENCE ACQUISITION

Randomised controlled trials in English language reporting any or all of the following parameters of bowel recovery; time to first bowel sounds, first flatus, first faeces, or time to oral diet were included.

EVIDENCE SYNTHESIS

Twelve hundred and thirty-five patients from 13 studies were analysed. There were insufficient studies evaluating bowel sounds. Perioperative dexmedetomidine usage significantly reduced the time to first flatus [MD -5.61 hours (95% CI -8.61 to -2.60); P = 0.0003; I2 = 95%], first faeces [MD -12.70 hours (95% CI -19.11 to -6.29); P = 0.0001; I2 = 76%] and the composite outcome of bowel recovery (flatus, faeces, oral diet) [MD -7.44 hours (95% CI -10.31 to -4.57); P < 0.00001; I2 = 96%]. No difference was seen in the time to oral diet [MD -6.29 hours (95% CI -13.48 to 0.91); P = 0.09; I2 = 88%] or hospital discharge [MD -0.47 days (95% CI -1.27 to 0.33); P = 0.25; I2 = 86%].

CONCLUSIONS

Perioperative dexmedetomidine usage significantly shortens the time to first flatus, faeces and composite bowel recovery but does not result in a shorter time to oral diet or earlier hospital discharge in adult patients receiving general anaesthesia. Strength of evidence is however very low for the effect of dexmedetomidine on bowel recovery.

The association of alvimopan treatment with postoperative outcomes after abdominal surgery: A systematic review across different surgical procedures and contexts of perioperative care

BACKGROUND

Alvimopan is a Food and Drug Administration-approved treatment to accelerate gastrointestinal recovery after abdominal surgery; however, benefits may vary across different procedures and contexts of care. The purpose of this study is to summarize the evidence regarding the effect of alvimopan on postoperative outcomes after abdominal surgery.

METHODS

Major databases (Medline, Embase, Biosis, Cochrane, Web of Science, and Scopus) were searched for randomized controlled trials and nonrandomized studies comparing alvimopan versus control. Risk of bias was assessed using Cochrane's risk of bias tool 2.0 (for randomized controlled trials) and Risk of Bias in Nonrandomized Studies-of Intervention tool (for nonrandomized studies). Results were appraised descriptively as heterogeneity in reporting and risk of bias hindered meta-analysis. Quality of evidence across different surgical procedures and contexts of care (ie, open versus minimally invasive surgery, traditional care versus enhanced recovery pathway) was evaluated using Grading of Recommendations Assessment, Development, and Evaluation.

RESULTS

Nine randomized controlled trials and 35 nonrandomized studies were identified. Evidence of low to moderate certainty supports that alvimopan reduces length of stay and improves gastrointestinal recovery after open bowel resection and open radical cystectomy. Limited evidence supports alvimopan for surgeries not listed in Food and Drug Administration labels (ie, total abdominal hysterectomy and retroperitoneal lymph node dissection). Similar effects were observed in traditional and enhanced recovery pathway settings, but enhanced recovery pathway elements varied across studies. There is very low certainty of evidence supporting alvimopan for patients undergoing minimally invasive surgery.

CONCLUSION

Evidence supports that alvimopan improves outcomes after open bowel resection and open radical cystectomy. Benefits for patients undergoing minimally invasive surgery and treated in contemporary enhanced recovery pathway settings remain uncertain. These findings contribute important new knowledge to inform evidence-based alvimopan prescribing.

Incidence and risk factors of postoperative ileus after hysterectomy for benign indications

PURPOSE

Postoperative ileus (POI) after abdominal surgery is associated with prolonged hospital stay and increased costs. The aim of this study is to investigate the incidence of, risk factors for, and outcomes associated with POI in patients undergoing hysterectomy for benign indications.

METHODS

A retrospective review of 1017 consecutive patients undergoing benign hysterectomy over the period 2012-2017 in a single center was performed. POI was predefined as absence of flatus and defecation for more than 2 days with the presence of one or more of the following symptoms: nausea, vomiting, and abdominal distention. The association between perioperative variables and the risk of POI was evaluated by univariate analysis. Independent risk factors were identified by multivariate logistic regression analysis.

RESULTS

Overall incidence of POI was 9.2%. Incidence of POI did not differ significantly among three different surgical approaches (abdominal hysterectomy, 10.6%; laparoscopic hysterectomy, 7.8%; vaginal hysterectomy, 11.3%; P = 0.279). Independent risk factors of POI identified by multivariate analysis included anesthesia technique (odds ratio [OR] 2.662, 95% interval [CI] 1.533-4.622, P = 0.001), adhesiolysis (odds ratio [OR] 1.818, 95% interval [CI] 1.533-4.622, P = 0.011), duration of operation (odds ratio [OR] 1.005, 95% interval [CI] 0.942-6.190, P = 0.029), previous cancer (odds ratio [OR] 4.789, 95% interval [CI] 1.232-18.626, P = 0.024), and dysmenorrhea (odds ratio [OR] 1.859, 95% interval [CI] 1.182-2.925, P = 0.007).

CONCLUSION

POI is a common complication after hysterectomy. This study identified risk factors of POI specifically for gynecologic patients. Patients exposed to these factors should be monitored closely for the development POI.

A new zinc chelator, IPZ-010 ameliorates postoperative ileus

Zinc was discovered to be a novel second messenger in immunoreactive cells. We synthesized a novel free zinc chelator, IPZ-010. Here, we investigated the effects of IPZ-010 in a mouse postoperative ileus model and determined the effects of zinc signal inhibition as a new therapeutic strategy against postoperative ileus. Zinc waves were measured in bone marrow-derived mast cells (BMMCs) loaded with a zinc indicator, Newport green. Degranulation and cytokine expression were measured in BMMCs and bone marrow-derived macrophages (BMDMs). Postoperative ileus model mice were established with intestinal manipulation. Mice were treated with IPZ-010 (30 mg/kg, s.c. or p.o.) 1 h before and 2 h and 4 h after intestinal manipulation. Gastrointestinal transit, inflammatory cell infiltration, and expression of inflammatory mediators were measured. Free zinc waves occurred following antigen stimulation in BMMCs and were blocked by IPZ-010. IPZ-010 inhibited interleukin-6 secretion and degranulation in BMMCs. IPZ-010 inhibited tumor necrosis factor-α mRNA expression in BMMCs stimulated with lipopolysaccharide or adenosine triphosphate, whereas IPZ-010 had no effects on tumor necrosis factor-α mRNA expression in BMDMs stimulated with lipopolysaccharide or adenosine triphosphate. In postoperative ileus model mice, IPZ-010 inhibited leukocyte infiltration and cytokine expression, which ameliorated gastrointestinal transit. Furthermore, ketotifen (1 mg/kg) induced similar effects as IPZ-010. These effects were not amplified by co-administration of IPZ-010 and ketotifen. IPZ-010 inhibited zinc waves, resulting in inhibition of inflammatory responses in activated BMMCs in vitro. Targeting zinc waves in inflammatory cells may be a novel therapeutic strategy for treating postoperative ileus.

A meta-analysis of naldemedine for the treatment of opioid-induced constipation

INTRODUCTION

Opioid-induced constipation (OIC) is a common adverse effect in patients under long-term opioid therapy. Naldemedine is a novel peripherally acting μ-opioid receptor antagonists being developed for the treatment of OIC without affecting central analgesia. This meta-analysis is to assess the current evidence for efficacy and safety of naldemedine for the treatment of OIC. Areas covered: We searched through MEDLINE, EMBASE, Web of Science and Cochrane Library, 'ISRCTN Register' and'ClinicalTrials.gov' (up to Aug 2018). Our final review included five randomized clinical trials (1751 participants in total), three trials observed naldemedine for the treatment of OIC in non-cancer patients and two trials in cancer patients. A Random Effects model was used for all comparisons. Subgroup analyses for the following subgroups were carried out: naldemedine 0.1 mg; 0.2 mg; 0.4 mg; cancer patients; non-cancer patients. Expert opinion: Naldemedine improved the proportion of responders and spontaneous bowel movements frequency. The incidence of serious adverse effects (AEs) in naldemedine group was higher than placebo, especially in cancer patient subgroup. The AEs occurred in participants with naldemedine were mild to moderate and well tolerated during treatment. The results of this network meta-analysis will guide the future researchers in evaluating naldemedine for the treatment of OIC.

The Efficacy of Peripheral Opioid Antagonists in Opioid-Induced Constipation and Postoperative Ileus: A Systematic Review of the Literature

Opioid-induced constipation has a negative impact on quality of life for patients with chronic pain and can affect more than a third of patients. A related but separate entity is postoperative ileus, which is an abnormal pattern of gastrointestinal motility after surgery. Nonselective μ-opioid receptor antagonists reverse constipation and opioid-induced ileus but cross the blood-brain barrier and may reverse analgesia. Peripherally acting μ-opioid receptor antagonists target the μ-opioid receptor without reversing analgesia. Three such agents are US Food and Drug Administration approved. We reviewed the literature for randomized controlled trials that studied the efficacy of alvimopan, methylnaltrexone, and naloxegol in treating either opioid-induced constipation or postoperative ileus. Peripherally acting μ-opioid receptor antagonists may be effective in treating both opioid-induced bowel dysfunction and postoperative ileus, but definitive conclusions are not possible because of study inconsistency and the relatively low quality of evidence. Comparisons of agents are difficult because of heterogeneous end points and no head-to-head studies.

Effect of alvimopan on gastrointestinal recovery and length of hospital stay after retroperitoneal lymph node dissection for testicular cancer

Objective

Alvimopan use has reduced the length of hospital stay in patients undergoing major abdominal surgeries and radical cystectomy. Retroperitoneal lymph node dissection for testicular cancer may be associated with delayed gastrointestinal recovery prolonging hospital length of stay. We evaluate whether alvimopan is associated with enhanced gastrointestinal recovery and shorter hospital length of stay in men undergoing retroperitoneal lymph node dissection for testicular cancer.

Materials and methods

From 2010 to 2016, 29 patients underwent open, transperitoneal bilateral template retroperitoneal lymph node dissection. Data for patients who received alvimopan were prospectively collected and compared to a historical cohort of patients who did not receive alvimopan. Primary outcome measures were length of stay and recovery of gastrointestinal function. Descriptive statistics were reported. Time-to-event outcomes were evaluated using cumulative incidence curves and log rank test. Factors associated with length of stay were analyzed for correlation using multiple linear regression.

Results

Of 29 men undergoing retroperitoneal lymph node dissection, eight received alvimopan and 21 did not. The two cohorts were well matched, with no significant differences. In the alvimopan cohort compared with those who did not receive alvimopan median time to return of flatus was 2 versus 4 days (p=0.0002), and median time to first bowel movement was 2.5 versus 5 days (p=0.046), respectively. Median length of stay in the alvimopan cohort was 4 days versus 6 days in those who did not receive alvimopan (p=0.074). In adjusted analyses, receipt of alvimopan did not influence length of stay.

Conclusion

Alvimopan may facilitate gastrointestinal recovery after retroperitoneal lymph node dissection for testicular cancer. Whether this translates into reduced length of stay needs to be determined by randomized controlled trials using larger cohorts.

Level of evidence

3b.

Stereoselective HPLC separation of alvimopan on cellulose-based immobilized polysaccharide as a chiral stationary phase

Chiral separation by normal phase high performance liquid chromatography is one of the most powerful technique to quantify the chiral purity of the compounds. In this study, a novel, simple, and specific analytical method was proposed to ascertain the chiral purity of alvimopan (ALV). The normal phase HPLC method was developed based on cellulose tris (3,5-dichlorophenylcarbamate) stationary phase. The separation of ALV isomers achieved by using column CHIRALPAK IC (250 × 4.6 mm, 5 μm), mobile phase n-hexane: isopropyl alcohol: ethanol: diethylamine (650:200:150:5 v/v), column oven temperature 30°C, flow rate 1.0 mL min-1 , injection volume was 10 μL, chromatographic response monitored at 273 nm. The developed method was validated as per the ICH guidelines and found precise, accurate, and linear. The advantage of the method is a good separation of ALV isomers within 35 minutes of the analysis time. Therefore, this method is suitable for routine determination of chiral purity of ALV active pharmaceutical ingredient.

Postoperative ileus following major colorectal surgery

BACKGROUND

Postoperative ileus (POI) is characterized by delayed gastrointestinal recovery following surgery. Current knowledge of pathophysiology, clinical interventions and methodological challenges was reviewed to inform modern practice and future research.

METHODS

A systematic search of MEDLINE and Embase databases was performed using search terms related to ileus and colorectal surgery. All RCTs involving an intervention to prevent or reduce POI published between 1990 and 2016 were identified. Grey literature, non-full-text manuscripts, and reanalyses of previous RCTs were excluded. Eligible articles were assessed using the Cochrane tool for assessing risk of bias.

RESULTS

Of 5614 studies screened, 86 eligible articles describing 88 RCTs were identified. Current knowledge of pathophysiology acknowledges neurogenic, inflammatory and pharmacological mechanisms, but much of the evidence arises from animal studies. The most common interventions tested were chewing gum (11 trials) and early enteral feeding (11), which are safe but of unclear benefit for actively reducing POI. Others, including thoracic epidural analgesia (8), systemic lidocaine (8) and peripheral μ antagonists (5), show benefit but require further investigation for safety and cost-effectiveness.

CONCLUSION

POI is a common condition with no established definition, aetiology or treatment. According to current literature, minimally invasive surgery, protocol-driven recovery (including early feeding and opioid avoidance strategies) and measures to avoid major inflammatory events (such as anastomotic leak) offer the best chances of reducing POI.

Does coffee affect the bowel function after caesarean section?

OBJECTIVES

Postoperative ileus is a common consequence of abdominal surgery, which tends to prolong the duration of hospital stay and imposes considerable economic costs on healthcare system. Coffee is proved to have positive effects on gastrointestinal motility index in healthy young adults. Thus, the present study aims to examine effects of coffee on bowel function after caesarean section.

MATERIAL AND METHOD

A total number 100 patients after elective caesarean section were randomly assigned before surgery into control and intervention groups. The intervention group received 100cc coffee at 8, 12 and 20h after the surgery, while the control group received 100cc hot water at the same intervals. First bowel sound, first passage of flatus, first defecation, and length of stay after surgery were compared in the two groups.

FINDINGS

Mean time to first flatus passage was recorded in the control (22.54±5.09h) and intervention (17.28±4.44h) groups and showed to be statistically significant (p=-0.000). However, average time of first defecation (intervention 37.22±16.31h; control 36.82±16.5h; p=0.647) and mean time of hospital stay of patients (intervention 30.08±9.50h; control 32.16±11.82h; p=0.518) and first bowel sound (intervention 5.84±1.41h; control 6.16±1.33h; p=-0.326) were not statistically significant.

DISCUSSION

Drinking coffee after a caesarean section reduces time to first flatus in patients. Nevertheless, further studies are needed to examine effects of coffee on ileus after elective caesarean section.

Alvimopan for recovery of bowel function after radical cystectomy

BACKGROUND

Alvimopan is used in abdominal surgery to reduce postoperative ileus in patients undergoing small bowel resections with primary anastomosis. The role and efficacy of alvimopan in patients undergoing radical cystectomy with urinary diversion is not well understood.

OBJECTIVES

To assess the effects of alvimopan in the context of enhanced recovery pathways compared to enhanced recovery pathways alone for perioperative bowel dysfunction in patients undergoing radical cystectomy.

SEARCH METHODS

The terms alvimopan and cystectomy were used to search the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase. We also reviewed abstracts from the past four years (2013 to 2016) of the American Urologic Association, Society of Urologic Oncology, and American Society of Clinical Oncology Genitourinary Cancers.

SELECTION CRITERIA

We searched for randomized controlled trials that compared alvimopan to placebo.

DATA COLLECTION AND ANALYSIS

This study was based on a published protocol. We performed a comprehensive search of multiple databases including CENTRAL in the Cochrane Library, MEDLINE, Embase, LILACS, Web of Science, Scopus and Biosis, which we last updated on 6 February 2017. We also searched abstract proceedings for major relevant meetings (2013 to 2016), databases of the grey literature, trial registries, citations of relevant reviews and contacted clinical experts and the drug manufacturer.Two independent reviewers screened the literature in two stages (title and abstract, full-text) using Covidence software. Two independent reviewers assessed the risk of bias on a 'per outcome' basis using the Cochrane 'Risk of bias; tool and rated the quality of evidence according to GRADE. Results of the single eligible trial were reported in a 'Summary of findings' table based on an intention-to-treat analysis.

MAIN RESULTS

Based on a single trial and moderate-quality evidence, alvimopan reduced the time to reach a composite endpoint of tolerance of solid food and documented bowel movements (hazard ratio (HR) 1.77, 95% confidence interval (CI) 1.41 to 2.23). This represents 165 more patients (109 more to 207 more) per 1000 meeting this endpoint within 10 days of surgery. Based on moderate-quality evidence, alvimopan reduced the time to hospital discharge (HR 1.67, 95% CI 1.38 to 2.01). This represents 138 more patients (82 more to 198 more) per 1000 being discharged within 10 days of surgery. Also based on moderate-quality evidence, alvimopan was associated with a reduced risk of major adverse events (risk ratio (RR) 0.28, 95% CI 0.18 to 0.44) representing 355 fewer patients (404 fewer to 276 fewer) with major adverse events per 1000. We downgraded this outcome for indirectness as it included adverse events that we did not consider major.In terms of secondary outcomes, alvimopan did not appear to alter the rate of readmission (RR 0.89, 95% CI 0.59 to 1.33), change the rate of any cardiovascular event (RR 0.54, 95% CI 0.27 to 1.05) or alter the mean narcotic pain medication use (mean difference 0, 95% CI 14.08 fewer to 14.08 more morphine equivalents). The quality of evidence was moderate for all three outcomes. Based on high-quality evidence, alvimopan reduced the rate of nasogastric tube replacement (RR 0.31, 95% CI 0.16 to 0.59). We did not find evidence for the drug's impact on rates of parenteral nutrition. All outcomes were short term and limited to a 30-day time horizon.Based on the existence of only one trial, we were unable to perform any subgroup or sensitivity analyses.

AUTHORS' CONCLUSIONS

In patients undergoing radical cystectomy and urinary diversion, the use of alvimopan administered as part of an enhanced recovery pathway for a limited duration (up to 15 doses for up to seven days) probably reduces the time to tolerance of solid food, time to hospital discharge and rates of major adverse events. Readmission rates, rates of cardiovascular events and narcotic pain requirements are probably similar. The need for reinsertion of nasogastric tubes is reduced. We found no evidence for the impact on rates of parenteral nutrition within 30 postoperative days.

Comparative Pharmacology and Guide to the Use of the Serotonin 5-HT3 Receptor Antagonists for Postoperative Nausea and Vomiting

Since the introduction of the serotonin 5-hydroxy tryptamine 3 (5-HT₃) receptor antagonists in the early 1990s, the incidence of postoperative nausea and vomiting (PONV) and post-discharge nausea and vomiting (PDNV) has decreased, yet continues to be a problem for the surgical patient. The clinical application of the 5-HT₃ receptor antagonists has helped define the approach and role of these antiemetics in the prevention and treatment of PONV and PDNV. Pharmacological and clinical differences exist among these medications resulting in corresponding differences in effectiveness, safety, optimal dosage, time of administration, and use as combination and rescue antiemetic therapy. The clinical application of the 5-HT₃ receptor antagonist antiemetics has improved the prevention and treatment of PONV and PDNV. The most recent consensus guidelines for PONV published in 2014 outline the use of these antiemetics. The 5-HT₃ receptor antagonists play an important role to help prevent PONV and PDNV in perioperative care pathways such as Enhanced Recovery After Surgery (ERAS). Comparisons and guidelines for use of the 5-HT₃ receptor antagonists in relation to the risk for PONV and PDNV are reviewed.

Prokinetic effects of LD02GIFRO on functional gastrointestinal disorder in rats

LD02GIFRO is a novel prokinetic agent formulated with Poncirus fructus and Zanthoxylum sp. fruits. The aim of the present study was to evaluate the effect of LD02GIFRO on delayed gastrointestinal transit (GIT) and colorectal hypersensitivity. To investigate the effect of LD02GIFRO, a rat model of delayed GIT was induced via three mechanisms; postoperative ileus (POI), morphine, and POI plus morphine. Visceromotor responses (VMR) to colorectal distension (CRD) were also evaluated. POI was induced by laparotomy surgery and manipulation of the small intestine under anesthesia, and GIT was calculated by measuring the length that Evans Blue travelled through the gastrointestinal tract in a given time. Oral administration of 260 mg/kg LD02GIFRO caused Evans Blue to migrate significantly further in the delayed GIT models induced by POI, morphine and POI plus morphine compared with the control (P<0.05). This effect was inhibited by atropine, a muscarinic receptor antagonist, and completely abolished by GR125487, a 5-HT₄-receptor antagonist. Furthermore, intraperitoneal administration of 600 and 900 mg/kg LD02GIFRO significantly reduced VMR to CRD in acute and chronic colorectal hypersensitive rat models, induced by acetic acid and trinitrobenzenesulfonic acid, to almost normal levels (P<0.01). In the present study, LD02GIFRO successfully ameliorated delayed GIT models and colorectal hypersensitivity models, suggesting that LD02GIFRO may be an effective therapeutic treatment for patients with functional gastrointestinal disorders and abnormalities in GIT.

Does the Ileal Brake Contribute to Delayed Gastric Emptying After Pancreatoduodenectomy?

Delayed gastric emptying (DGE) represents a significant cause for morbidity following pancreatoduodenectomy (PD). At a time when no specific and universally effective therapy exists to treat these patients, elucidating other potential (preventable or treatable) mechanisms for DGE is important. The aim of the manuscript was to test the hypothesis that ileal brake contributes to DGE in PD patients receiving jejunal tube feeding by systematically reviewing experimental and clinical literature. A series of clinically relevant questions were framed related to the potential role of the ileal brake in development of DGE post-PD and formed the basis of targeted literature searches. A comprehensive search of major reference databases from January 1980 to June 2015 was carried out which included human and animal studies. The ileal brake is a feedback loop neurally mediated by the vagus and sympatho-adrenergic pathways and hormonally by gut peptides including glucagon-like peptide-1, peptide YY (PYY), and neurotensin. The most potent stimulus for this inhibitory reflex is intra-ileal fat. There is evidence to indicate the role of an inhibitory reflex (on gastric emptying) mediated by PYY and CCK which, in turn, are stimulated by nutrient delivery into the distal small intestine providing indirect support to the role of ileal brake in post-PD DGE. The ileal brake is a likely factor contributing to DGE post-PD. While there has been no study to directly test this hypothesis, there is compelling indirect evidence to support it. Designing a trial that would answer such a question appears to be the most appropriate way forward.

Gastric Feeding as an Extension of an Established Enteral Nutrition Protocol

BACKGROUND

Indiscriminate gastric feeding in ICU patients imposes unacceptable risks of aspiration. Believing that a subset of ICU patients can be fed safely via the stomach, we have developed a protocol to identify appropriate patients and guide the bedside clinician in how to safely and effectively feed via the stomach.

METHODS

A literature search was done to identify appropriate medical literature. High grade evidence along with local expert opinions were used to develop a protocol. This protocol has been refined and implemented.

RESULTS

Based on perceived risk of aspiration, patients are assigned enteral access (ie, stomach vs. distal post-pyloric). Enteral formula is selected based on patient characteristics. It is then advanced by a standard protocol with specific precautions while monitoring for symptoms of intolerance. Management of intolerance is dictated by the type and severity of intolerance.

CONCLUSION

We have implemented a gastric feeding into a subset of our ICU patients. Gastric feeding requires certain precautions but appears to be safe. With more experience and better understanding of the pathogenesis gastroparesis, we believe that most ICU patients should be able to safely feed into the stomach. This is logistically easier than post-pyloric feeding and offers physiologic advantages.

Electroacupuncture treatment partly promotes the recovery time of postoperative ileus by activating the vagus nerve but not regulating local inflammation

Postoperative ileus (POI) after abdominal surgery significantly lowers the life quality of patients and increase hospital costs. However, few treatment strategies have successfully shortened the duration of POI. Electroacupuncture (EA) is a modern way of administering acupuncture and widely used in various gastrointestinal (GI) diseases in the world. Here, we studied the effect of EA on POI and its underlying mechanisms. Intestinal manipulation resulted in significant delays of GI transit, colonic transit and gastric emptying. Surgery also up-regulated c-fos in nucleus of the solitary tract (NTS) and induced inflammation response in the small intestine. Further, operation and inhale anesthesia inhibited NTS neuron excitation duration for the whole observation time. EA administered at ST36 indeed shortened the recovery time of GI and colonic transit, and significantly increased the gastric emptying. EA also significantly activated the NTS neurons after operation. However, there was no anti-inflammation effect of EA during the whole experiment. Finally, atropine blocked the regulatory effect of EA on GI function, when it was injected after surgery, but not before surgery. Thus, the regulatory effect of EA on POI was mainly mediated by exciting NTS neurons to improve the GI tract transit function but not by activating cholinergic anti-inflammatory pathway.

The use of alvimopan for postoperative ileus in small and large bowel resections

Transient ileus is a normal physiologic process after surgery. When prolonged, it is an important contributor to postoperative complications, increased length of stay and increased healthcare costs. Efforts have been made to prevent and manage postoperative ileus; alvimopan is an oral, peripheral μ-opioid receptor antagonist, and the only currently US FDA-approved medication to accelerate the return of gastrointestinal function postoperatively.

Redefining the implications of nasogastric tube placement following radical cystectomy in the alvimopan era

PURPOSE

Alvimopan has decreased ileus and need for nasogastric tube (NGT) after radical cystectomy (RC). However, the natural history of ileus versus intestinal obstruction in patients receiving alvimopan is not well defined. We sought to examine the implications of NGT placement before and after the introduction of alvimopan for RC patients.

METHODS

Retrospective review identified 278 and 293 consecutive patients who underwent RC before and after instituting alvimopan between June 2009 and May 2014. Baseline characteristics and postoperative outcomes were compared by alvimopan status. Multivariate logistic regression was performed to assess the impact of alvimopan on rates of NGT placement and reoperation for bowel complications.

RESULTS

The cohorts had similar age, stage, approach, and BMI. Patients receiving alvimopan had decreased ileus (16 vs 32 %, p < 0.01) but similar rates of reoperation for bowel complications (2.8 vs 2.7 %). On multivariate analysis, alvimopan was associated with lower risk of NGT placement (OR 0.30, p < 0.01). For patients requiring NGT placement, there was an increased rate of reoperation among patients receiving alvimopan compared with those who did not (28 vs 11 %, p = 0.03). Patients receiving alvimopan who needed NGT had significantly increased median length of stay (22 vs 7 days), need for TPN (66 vs 5.3 %), and readmission for ileus (10.3 vs 2.3 %) compared with those who did not require NGT.

CONCLUSIONS

Alvimopan significantly reduced the incidence of ileus and NGT placement following RC. NGT placement was associated with an increased need for reoperation for bowel complications in the setting of alvimopan.

Pharmacological management to prevent ileus in major abdominal surgery: a systematic review and meta-analysis

BACKGROUND

Prolonged ileus is a common complication following gastrointestinal surgery, with an incidence of up to 40 %. Investigations examining pharmacological treatment of ileus have proved largely disappointing; however, recently, several compounds have been shown to have benefited when used as prophylaxis to prevent ileus.

OBJECTIVE

This review aimed to evaluate the safety and efficacy of compounds which have been recently developed or repurposed to reduce bowel recovery time, thereby preventing ileus.

DATA SOURCES

Data were taken from a systematic review of the MEDLINE, EMBASE and Cochrane Library Databases, in addition to manual searching of reference lists up to April 2015. No limits were applied.

STUDY SELECTION

Only randomized trials were eligible for inclusion.

INTERVENTIONS

Opioid receptor antagonists, ghrelin receptor agonists and serotonin receptor agonists used for the prevention of postoperative ileus in gastrointestinal surgery.

MAIN OUTCOME MEASURES

Outcomes of time to first defecation, first flatus and composite bowel recovery endpoints (GI2 and GI3) were used to determine efficacy. Pooled treatment effects were presented as the standard mean difference or as hazard ratios alongside the corresponding 95 % confidence intervals. Risk of bias was assessed using the Cochrane risk of bias framework.

RESULTS

A total of 17 studies were included in the final analysis. The μ-opioid receptor antagonist alvimopan and serotonin receptor agonists appeared to significantly shorten the duration of ileus. The use of Ghrelin receptor agonists did not appear to have any effect in five trials. No publication bias was detected.

LIMITATIONS

Most of the trials were poorly reported and of mixed quality. Future studies must focus on the development of a set of core outcomes.

CONCLUSIONS

There is evidence to make a strong recommendation for the use of alvimopan in major gastrointestinal surgery to reduce postoperative ileus. Further randomized trials are required to establish whether serotonin receptor agonists are of use. Identifying a low-cost compound to promote bowel recovery following surgery could reduce complications and shorten duration of hospital admissions.

Alvimopan combined with enhanced recovery strategy for managing postoperative ileus after open abdominal surgery: a systematic review and meta-analysis

BACKGROUND

To assess the efficacy and safety of alvimopan in conjunction with enhanced recovery strategy, compared with this strategy alone, in management of postoperative ileus in patients undergoing open abdominal surgery.

METHODS

Electronic databases were comprehensively searched for relevant randomized controlled trials. We were interested in doses of 6 and 12 mg. The efficacy end points included the time to recovery of full gastrointestinal (GI) function (a composite end point measured by the time to first toleration of solid food [SF] and the time to first passage of stool, GI-2), the recovery of upper (SF) or the lower (the time to first bowel movement, BM) GI function, and the length of hospital stay (the time to discharge order written). Safety end points included GI-related, non-GI-related, and serious adverse events. These parameters were all analyzed by RevMan 5.3 software.

RESULTS

Nine randomized controlled trials involving 4075 patients were enrolled in this study. The pooled results showed that alvimopan significantly decreased the time to GI-2 recovery (6 mg, hazard ratio [HR] = 1.45, P < 0.00001; 12 mg, HR = 1.59, P < 0.00001), BM (6 mg, HR = 1.54, P < 0.00001; 12 mg, HR = 1.74, P = 0.0002), and the time to discharge order written (6 mg, HR = 1.37, P < 0.00001; 12 mg, HR = 1.34, P < 0.00001) compared with the placebo group. However, SF was significantly reduced in 6 mg group (HR = 1.23, P = 0.008) rather than 12 mg group (HR = 1.14, 95% confidence interval 1.00, 1.30, P = 0.04). The incidence of some GI-related and serious adverse events were significantly lower in the alvimopan group than the placebo group, and the dose of 12 mg was superior to 6 mg in this regard.

CONCLUSIONS

Alvimopan can accelerate recovery of GI function (especially for the lower GI tract), shorten the length of hospital stay, and reduce postoperative ileus-related morbidity without compromising opioid analgesia in an enhanced recovery setting.

Delayed gastrointestinal recovery after abdominal operation - role of alvimopan

Postoperative Ileus (POI), which occurs after surgical manipulation of the bowel during abdominal operations, is associated with prolonged hospital stay, increasing medical costs, and delayed advancement of enteral diet, which contributes to a significant economic burden on the healthcare system. The use of accelerated care pathways has shown to positively impact gut function, but inevitable postoperative opioid use contributes to POI. Alvimopan is a peripherally acting μ-opioid receptor antagonist designed to mitigate antimotility effects of opioids. In our review, we examined ten trials on alvimopan’s use after abdominal operations. Several of the earlier studies on patients undergoing bowel resection showed correlations between the study group and GI recovery as defined by passage of flatus, first bowel movement, and time to readiness for discharge. Data in patients undergoing total abdominal hysterectomy showed similarly decreased GI recovery time. Additionally, data within the past few years shows alvimopan is associated with more rapid GI recovery time in patients undergoing radical cystectomy. Based on our review, use of alvimopan remains a safe and potentially cost-effective means of reducing POI in patients following open GI surgery, radical cystectomy, and total abdominal hysterectomy, and should be employed following these abdominal operations.

Off-label uses of alvimopan and methylnaltrexone

PURPOSE

Off-label uses of the peripheral μ-opioid receptor antagonists alvimopan and methylnaltrexone are reviewed.

SUMMARY

Alvimopan is approved by the Food and Drug Administration (FDA) for postoperative ileus after surgeries that include partial bowel resection with primary anastomosis, while methylnaltrexone is approved for the treatment of opioid-induced constipation (OIC) in patients with advanced illness who are receiving palliative care. Literature describing the off-label use of alvimopan in the treatment of OIC and of methylnaltrexone in postoperative ileus was reviewed and included retrospective studies and prospective Phase II-IV trials. Randomized controlled trials did not demonstrate consistent benefit of alvimopan in OIC nor of methylnaltrexone in postoperative ileus. A greater proportion of patients receiving alvimopan for OIC experienced severe adverse cardiovascular events, leading to a risk evaluation and mitigation strategy and discontinuation of its study in this condition. Data are limited and unreplicated for the off-label use of alvimopan for postoperative ileus in patients undergoing abdominal hysterectomy. Individual studies suggest benefit with methylnaltrexone for OIC in unlabeled populations, including patients with non-cancer-related pain, opioid dependence, opioid sedation, and opioid use after orthopedic surgery; however, confirmatory evaluations have not been performed.

CONCLUSION

Trials of alvimopan in the FDA-approved use of methylnaltrexone (OIC) indicate potentially serious cardiovascular safety concerns and conflicting findings of efficacy. Similarly, trials of methylnaltrexone in the FDA-approved use of alvimopan (postoperative ileus) consistently showed no benefit. Evaluations of both drugs in their labeled conditions in populations not endorsed in their product labeling have been limited and largely unreplicated.

Early versus delayed oral fluids and food for reducing complications after major abdominal gynaecologic surgery

BACKGROUND

This is an updated version of the original Cochrane review published in 2007. Traditionally, after major abdominal gynaecologic surgery postoperative oral intake is withheld until the return of bowel function. There has been concern that early oral intake would result in vomiting and severe paralytic ileus with subsequent aspiration pneumonia, wound dehiscence, and anastomotic leakage. However, evidence-based clinical studies suggest that there may be benefits from early postoperative oral intake.

OBJECTIVES

To assess the effects of early versus delayed (traditional) initiation of oral intake of food and fluids after major abdominal gynaecologic surgery.

SEARCH METHODS

We searched the Menstrual Disorders and Subfertility Group's Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), electronic databases (MEDLINE, EMBASE, CINAHL), and the citation lists of relevant publications. The most recent search was conducted 1 April 2014. We also searched a registry for ongoing trials (www.clinicaltrials.gov) on 13 May 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) were eligible that compared the effect of early versus delayed initiation of oral intake of food and fluids after major abdominal gynaecologic surgery. Early feeding was defined as oral intake of fluids or food within 24 hours post-surgery regardless of the return of bowel function. Delayed feeding was defined as oral intake after 24 hours post-surgery and only after signs of postoperative ileus resolution.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies, assessed study quality and extracted the data. For dichotomous data, we calculated the risk ratio (RR) with a 95% confidence interval (CI). We examined continuous data using the mean difference (MD) and a 95% CI. We tested for heterogeneity between the results of different studies using a forest plot of the meta-analysis, the statistical tests of homogeneity of 2 x 2 tables and the I² value. We assessed the quality of the evidence using GRADE methods.

MAIN RESULTS

Rates of developing postoperative ileus were comparable between study groups (RR 0.47, 95% CI 0.17 to 1.29, P = 0.14, 3 RCTs, 279 women, I² = 0%, moderate-quality evidence). When we considered the rates of nausea or vomiting or both, there was no evidence of a difference between the study groups (RR 1.03, 95% CI 0.64 to 1.67, P = 0.90, 4 RCTs, 484 women, I² = 73%, moderate-quality evidence). There was no evidence of a difference between the study groups in abdominal distension (RR 1.07, 95% CI 0.77 to 1.47, 2 RCTs, 301 women, I² = 0%) or a need for postoperative nasogastric tube placement (RR 0.48, 95% CI 0.13 to 1.80, 1 RCT, 195 women).Early feeding was associated with shorter time to the presence of bowel sound (MD -0.32 days, 95% CI -0.61 to -0.03, P = 0.03, 2 RCTs, 338 women, I² = 52%, moderate-quality evidence) and faster onset of flatus (MD -0.21 days, 95% CI -0.40 to -0.01, P = 0.04, 3 RCTs, 444 women, I² = 23%, moderate-quality evidence). In addition, women in the early feeding group resumed a solid diet sooner (MD -1.47 days, 95% CI -2.26 to -0.68, P = 0.0003, 2 RCTs, 301 women, I² = 92%, moderate-quality evidence). There was no evidence of a difference in time to the first passage of stool between the two study groups (MD -0.25 days, 95% CI -0.58 to 0.09, P = 0.15, 2 RCTs, 249 women, I² = 0%, moderate-quality evidence). Hospital stay was shorter in the early feeding group (MD -0.92 days, 95% CI -1.53 to -0.31, P = 0.003, 4 RCTs, 484 women, I² = 68%, moderate-quality evidence). Infectious complications were less common in the early feeding group (RR 0.20, 95% CI 0.05 to 0.73, P = 0.02, 2 RCTs, 183 women, I² = 0%, high-quality evidence). In one study, the satisfaction score was significantly higher in the early feeding group (MD 11.10, 95% CI 6.68 to 15.52, P < 0.00001, 143 women, moderate-quality evidence).

AUTHORS' CONCLUSIONS

Early postoperative feeding after major abdominal gynaecologic surgery for either benign or malignant conditions appeared to be safe without increased gastrointestinal morbidities or other postoperative complications. The benefits of this approach include faster recovery of bowel function, lower rates of infectious complications, shorter hospital stay, and higher satisfaction.

Postoperative ileus: mechanisms and future directions for research

Postoperative ileus (POI) is an abnormal pattern of gastrointestinal motility characterized by nausea, vomiting, abdominal distension and/or delayed passage of flatus or stool, which may occur following surgery. Postoperative ileus slows recovery, increases the risk of developing postoperative complications and confers a significant financial load on healthcare institutions. The aim of the present review is to provide a succinct overview of the clinical features and pathophysiological mechanisms of POI, with final comment on selected directions for future research.Terminology used when describing POI is inconsistent, with little differentiation made between the obligatory period of gut dysfunction seen after surgery ('normal POI') and the more clinically and pathologically significant entity of a 'prolonged POI'. Both normal and prolonged POI represent a fundamentally similar pathophysiological phenomenon. The aetiology of POI is postulated to be multifactorial, with principal mediators being inflammatory cell activation, autonomic dysfunction (both primarily and as part of the surgical stress response), agonism at gut opioid receptors, modulation of gastrointestinal hormone activity and electrolyte derangements. A final common pathway for these effectors is impaired contractility and motility and gut wall oedema. There are many potential directions for future research. In particular, there remains scope to accurately characterize the gastrointestinal dysfunction that underscores an ileus, development of an accurate risk stratification tool will facilitate early implementation of preventive measures and clinical appraisal of novel therapeutic strategies that target individual pathways in the pathogenesis of ileus warrant further investigation.

Pharmacological therapy of feed intolerance in the critically ills

Feed intolerance in the setting of critical illness is associated with higher morbidity and mortality, and thus requires promptly and effective treatment. Prokinetic agents are currently considered as the first-line therapy given issues relating to parenteral nutrition and post-pyloric placement. Currently, the agents of choice are erythromycin and metoclopramide, either alone or in combination, which are highly effective with relatively low incidence of cardiac, hemodynamic or neurological adverse effects. Diarrhea, however, can occur in up to 49% of patients who are treated with the dual prokinetic therapy, which is not associated with Clostridium difficile infection and settled soon after the cessation of the drugs. Hence, the use of prokinetic therapy over a long period or for prophylactic purpose must be avoided, and the indication for ongoing use of the drug(s) must be reviewed frequently. Second line therapy, such as total parenteral nutrition and post-pyloric feeding, must be considered once adverse effects relating the prokinetic therapy develop.

Facilitating return of bowel function after colorectal surgery: alvimopan and gum chewing

Postoperative ileus is common after colorectal surgery, and has a huge impact on hospital LOS. With the impeding cost crisis in the United States, safely reducing length of stay is essential. Chewing gum and pharmacological treatment with alvimopan are safe, simple tools to reduce postoperative ileus and its associated costs. Future research will determine if integrating these tools with laparoscopic procedures and enhanced recovery pathways is a best practice in colorectal surgery.

Biased agonism of the μ-opioid receptor by TRV130 increases analgesia and reduces on-target adverse effects versus morphine: A randomized, double-blind, placebo-controlled, crossover study in healthy volunteers

Opioids provide powerful analgesia but also efficacy-limiting adverse effects, including severe nausea, vomiting, and respiratory depression, by activating μ-opioid receptors. Preclinical models suggest that differential activation of signaling pathways downstream of these receptors dissociates analgesia from adverse effects; however, this has not yet translated to a treatment with an improved therapeutic index. Thirty healthy men received single intravenous injections of the biased ligand TRV130 (1.5, 3, or 4.5mg), placebo, or morphine (10mg) in a randomized, double-blind, crossover study. Primary objectives were to measure safety and tolerability (adverse events, vital signs, electrocardiography, clinical laboratory values), and analgesia (cold pain test) versus placebo. Other measures included respiratory drive (minute volume after induced hypercapnia), subjective drug effects, and pharmacokinetics. Compared to morphine, TRV130 (3, 4.5mg) elicited higher peak analgesia (105, 116 seconds latency vs 75 seconds for morphine, P<.02), with faster onset and similar duration of action. More subjects doubled latency or achieved maximum latency (180 seconds) with TRV130 (3, 4.5mg). Respiratory drive reduction was greater after morphine than any TRV130 dose (-15.9 for morphine versus -7.3, -7.6, and -9.4 h*L/min, P<.05). More subjects experienced severe nausea after morphine (n=7) than TRV130 1.5 or 3mg (n=0, 1), but not 4.5mg (n=9). TRV130 was generally well tolerated, and exposure was dose proportional. Thus, in this study, TRV130 produced greater analgesia than morphine at doses with less reduction in respiratory drive and less severe nausea. This demonstrates early clinical translation of ligand bias as an important new concept in receptor-targeted pharmacotherapy.

Biased ligands at G-protein-coupled receptors: promise and progress

Drug discovery targeting G protein-coupled receptors (GPCRs) is no longer limited to seeking agonists or antagonists to stimulate or block cellular responses associated with a particular receptor. GPCRs are now known to support a diversity of pharmacological profiles, a concept broadly referred to as functional selectivity. In particular, the concept of ligand bias, whereby a ligand stabilizes subsets of receptor conformations to engender novel pharmacological profiles, has recently gained increasing prominence. This review discusses how biased ligands may deliver safer, better tolerated, and more efficacious drugs, and highlights several biased ligands that are in clinical development. Biased ligands targeting the angiotensin II type 1 receptor and the μ opioid receptor illustrate the translation of the biased ligand concept from basic biology to clinical drug development.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Randomized placebo-controlled study of intravenous methylnaltrexone in postoperative ileus

OBJECTIVE

This phase 2 study evaluated the safety and activity of intravenous methylnaltrexone on the duration of postoperative ileus in patients undergoing segmental colectomy.

METHODS

Adults (aged 18 years or older) with American Society of Anesthesiologists physical status of I, II, or III who underwent segmental colectomy, including partial colectomy, sigmoidectomy, cecectomy, or anterior proctosigmoidectomy, via laparotomy with general anesthesia, received intravenous methylnaltrexone 0.30 mg/kg or placebo every 6 h beginning within 90 min after end of surgery. Treatment continued until 24 h after the patient tolerated solid foods, was discharged, or for 7 d maximum. Efficacy endpoints included measures of gastrointestinal recovery and time to discharge eligibility.

RESULTS

A total of 65 patients (methylnaltrexone, n = 33; placebo, n = 32) were randomized. Mean time to first bowel movement was accelerated by 20 h (p = 0.038) and time to discharge eligibility was accelerated by 33 h (p = 0.049) with methylnaltrexone vs placebo. Opioid use was similar between groups until postoperative day 4, then fluctuated in the placebo group. Methylnaltrexone was generally well tolerated.

CONCLUSIONS

In this study, intravenous methylnaltrexone significantly decreased time to postoperative bowel recovery and eligibility for hospital discharge by ∼1 d, with an adverse event profile similar to placebo. These were two of several exploratory endpoints; not all efficacy endpoints showed a significant difference between methylnaltrexone and placebo. The efficacy results in this trial were not seen in two subsequent large-scale studies.

Impaired gastrointestinal transit and its associated morbidity in the intensive care unit

PURPOSE

To determine the proportion of critically ill adults developing impaired gastrointestinal transit (IGT) using a clinically pragmatic definition, its associated morbidity and risk factors.

MATERIALS AND METHODS

Critically ill adult patients receiving enteral nutrition for ≥ 72 hours and mechanically ventilated for ≥ 48 hours were prospectively identified. IGT was defined as absence of a bowel movement for ≥ 3 days, treatment for constipation, and one of the following: (1) radiologic confirmed ileus, (2) feed intolerance, (3) abdominal distention, or (4) gastric decompression.

RESULTS

One thousand patients were screened, and 248 were included for analysis. Fifty patients (20.1%; 95% confidence interval, 15.1-25.6%) developed IGT persisting for 6.5 ± 2.5 days. Patients with IGT had longer lengths of intensive care unit stay and were less likely to reach nutrition targets compared to patients without IGT or traditional definitions of constipation. Daily opioid use and pharmacological constipation prophylaxis were identified risk factors for IGT.

CONCLUSION

Traditional definitions of constipation or ileus in intensive care unit patients are simplistic and lack clinical relevance. Pragmatically defined IGT is a common complication of critical illness and is associated with significant morbidity. Future interventional studies for IGT in critically ill adults should use a more clinically relevant definition and evaluate energy deficits and lengths of stay as clinically relevant outcomes.

Methylnaltrexone for the treatment of opioid-induced constipation

Opioids are the drugs of choice for treating moderate-to-severe pain, especially for patients in the end stage of cancer or other advanced illnesses, and also in critical care or for the treatment of chronic pain. Side effects such as nausea, pruritus, dizziness and constipation have to be controlled in order to use these drugs to their full potential. Opioid-induced bowel syndrome and constipation caused by activation of μ-receptors in the gut can have such distressing effects that some patients prefer to forego adequate pain control. Methylnaltrexone is a μ-opioid receptor antagonist that, unlike naltrexone or naloxone, does not pass the blood-brain barrier, and therefore does not impair the centrally mediated analgesic effect of opioids. It is licensed for the treatment of opioid-induced constipation in palliative care in more than 50 countries. This article presents practically relevant pharmacological data, basic research results and evidence from clinical research about methylnaltrexone, and outlines potential future therapeutic options for this promising drug.

A meta-analysis of the effectiveness of the opioid receptor antagonist alvimopan in reducing hospital length of stay and time to GI recovery in patients enrolled in a standardized accelerated recovery program after abdominal surgery

BACKGROUND

Despite accelerated recovery programs and the widespread uptake of laparoscopic surgery, postoperative ileus remains a significant factor affecting length of stay after abdominal surgery. Alvimopan, an opioid-receptor antagonist, may reduce the incidence of postoperative ileus and expedite hospital discharge.

OBJECTIVE

The aim of this study was to perform a meta-analysis to determine the role of alvimopan in accelerating GI recovery and hospital discharge after laparoscopic and open abdominal surgery performed within an accelerated recovery program.

DATA SOURCES AND STUDY SELECTION

Cochrane (1999-2010), Embase (1980-2010), MEDLINE (1980-2010), and International Pharmaceutical Abstracts (1970-2010) were searched for relevant double-blinded, randomized controlled trials.

INTERVENTIONS

Twelve milligrams of alvimopan and placebo were given to patients enrolled in an accelerated recovery program after abdominal surgery.

MAIN OUTCOME MEASURES

The primary outcomes measured were the length of stay as defined by the writing of the hospital discharge order and GI-3 and GI-2 GI tract recovery.

RESULTS

: Three trials were included that reported on a pooled modified intention-to-treat population of 1388 patients; 685 (49%) patients received alvimopan. On meta-analysis, alvimopan reduced time to the hospital discharge order (HR 1.37 (1.21, 1.62), p < 0.0001), GI-3 recovery (HR 1.42 (1.25, 1.62), p < 0.001), and GI-2 recovery (HR 1.49 (1.32, 1.68), p < 0.0001).

LIMITATIONS

The search criteria identified only a small number of trials of alvimopan after abdominal surgery with no randomized trials of alvimopan after laparoscopic surgery. In addition, the use of length of hospital stay as the primary outcome measure may be inappropriate, because it is open to many confounding factors. Finally, adverse events, in particular, adverse cardiovascular events, were not considered.

CONCLUSIONS

Alvimopan 12 mg can further reduce time to GI recovery and hospital discharge in patients undergoing abdominal surgery within an accelerated recovery program. Investigation into the effect of alvimopan following laparoscopic surgery and additional cost-benefit analyses are required to further define the role of this intervention.