Peripherally Acting μ-Opioid Receptor Antagonists in the Management of Postoperative Ileus: a Clinical Review

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.

The impact of opioid administration on the incidence of postanaesthetic colic in horses

Effective management of postoperative pain is essential to ensure patient welfare, reduce morbidity and optimize recovery. Opioids are effective in managing moderate to severe pain in horses but concerns over their adverse effects on gastrointestinal (GI) motility and associated increased colic risk limit their widespread use. Studies investigating the impact of systemic opioids on both GI motility and colic incidence in horses have yielded inconclusive outcomes. Therefore, this retrospective study aims to assess the influence of systemic administration of butorphanol, morphine, and methadone on post-anaesthetic colic (PAC) incidence. Horses undergoing general anaesthesia for non-gastrointestinal procedures that were hospitalized for at least 72 h post-anaesthesia were included in this study. Anaesthetised horses were stratified by procedure type into horses undergoing diagnostic imaging without surgical intervention, emergency or elective surgery. In addition, patients were grouped by opioid treatment regime into horses receiving no opioids, intraanaesthetic, short- (<24 h) or long-term (>24 h) postoperative opioids. Administered opioids encompassed butorphanol, morphine and methadone. The number of horses showing signs of colic in the 72 h after anaesthesia was assessed for each group. A total of 782 horses were included, comprising 659 undergoing surgical procedures and 123 undergoing diagnostic imaging. The overall PAC incidence was 15.1%. Notably, horses undergoing diagnostic imaging without surgery had a significantly lower PAC rate of 6.5% compared to those undergoing surgery (16.7%, p = 0.0146). Emergency surgeries had a significantly lower PAC rate of 5.8% compared to elective procedures (18%, p = 0.0113). Of the 782 horses, 740 received intraoperative opioids and 204 postoperative opioids, 102 of which long-term (≥24 h). Neither intraoperative (p = 0.4243) nor short-term postoperative opioids (p = 0.5744) increased PAC rates. Notably, only the long-term (≥24 h) administration of morphine significantly increased PAC incidence to 34% (p = 0.0038). In contrast, long-term butorphanol (5.3% PAC, p = 0.8482) and methadone (18.4% PAC, p = 0.6161) did not affect PAC rates. In summary, extended morphine administration was the only opioid treatment associated with a significantly increased risk of PAC.

Nomogram for predicting prolonged postoperative ileus after laparoscopic low anterior resection for rectal cancer

BACKGROUND

Prolonged postoperative ileus (PPOI) is a common complication after colorectal surgery that increases patient discomfort, hospital stay, and financial burden. However, predictive tools to assess the risk of PPOI in patients undergoing laparoscopic low anterior resection have not been developed. Thus, the purpose of this study was to develop a nomogram to predict PPOI after laparoscopic low anterior resection for rectal cancer.

METHODS

A total of 548 consecutive patients who underwent laparoscopic low anterior resection for mid-low rectal cancer at a single tertiary medical center were retrospectively enrolled between January 2019 and January 2023. Univariate and multivariate logistic regression analysis was performed to analyze potential predictors of PPOI. The nomogram was constructed using the filtered variables and internally verified by bootstrap resampling. Model performance was evaluated by receiver operating characteristic curve and calibration curve, and the clinical usefulness was evaluated by the decision curve.

RESULTS

Among 548 consecutive patients, 72 patients (13.1%) presented with PPOI. Multivariate logistic analysis showed that advantage age, hypoalbuminemia, high surgical difficulty, and postoperative use of opioid analgesic were independent prognostic factors for PPOI. These variables were used to construct the nomogram model to predict PPOI. Internal validation, conducted through bootstrap resampling, confirmed the great discrimination of the nomogram with an area under the curve of 0.738 (95%CI 0.736-0.741).

CONCLUSIONS

We created a novel nomogram for predicting PPOI after laparoscopic low anterior resection. This nomogram can assist surgeons in identifying patients at a heightened risk of PPOI.

Predictive modeling of postoperative gastrointestinal dysfunction: the role of serum bilirubin, sodium levels, and surgical duration in gynecological cancer care

OBJECTIVE

To elucidate the role of preoperative serum bilirubin and sodium levels, along with the duration of surgery, in predicting postoperative gastrointestinal dysfunction (POGD) following gynecological cancer surgery, informing tailored perioperative strategies.

METHODS

We conducted a retrospective analysis of 281 patients undergoing gynecological cancer surgery between 2018 and 2023. This analysis focused on preoperative serum bilirubin and sodium levels and intraoperative factors (surgical duration) as potential predictors of POGD. Logistic regression models were utilized for analysis, controlling for relevant confounders.

RESULTS

Elevated preoperative serum bilirubin was associated with a reduced risk of POGD (mean level in non-POGD cases: 14.172 ± 4.0701, vs. POGD cases: 9.6429 ± 3.5351; p <  0.001), suggesting a protective role. Lower preoperative sodium levels were identified in the POGD group (136.26 mEq/L [IQR: 135.2-137.63]) compared to the non-POGD group (139.32 mEq/L [IQR: 137.7-140.75]; p <  0.001), highlighting its predictive value. Additionally, longer surgical duration was associated with increased POGD incidence, with POGD cases experiencing surgeries lasting 6.1547 ± 1.9426 hours compared to 4.5959 ± 1.5475 hours in non-POGD cases (p <  0.001).

CONCLUSION

Our findings underscore the importance of serum bilirubin, sodium levels, and surgical duration as significant predictors of POGD in patients undergoing gynecological cancer surgery. These indicators should be integrated into a predictive model, aiding clinicians in identifying high-risk patients, allowing for personalized perioperative care adjustments, potentially mitigating POGD risks.

Management of Constipation in Hospitalized Patients

Constipation is frequently encountered in hospital settings and can have potentially serious consequences yet is often underrecognized and undertreated. Opioid-induced constipation is a common cause of constipation in hospitalized patients. Opioids induce constipation through agonistic effects on enteric µ-opioid receptors. This review aims to provide insight on the identification and management of constipation in inpatient settings, with a particular focus on opioid-induced constipation. Constipation assessment should be routinely initiated at hospital admission and can be facilitated by thorough symptom assessments; relevant patient history, including recent medication use; physical examination; and patient assessment tools developed to evaluate the impact of constipation. Management of opioid-induced constipation should begin with ensuring adequate hydration and electrolyte balance and encouraging patient mobilization. Other treatments may include laxatives, enemas, intestinal secretagogues, peripherally acting µ-opioid receptor antagonists, and manual disimpaction. Surgical intervention may be required for some patients as a salvage therapy in severe, refractory cases.

Alvimopan is associated with favorable outcomes in open and minimally invasive colorectal surgery: a regional database analysis

BACKGROUND

Alvimopan is a µ-opioid receptor antagonist associated with shorter time to gastrointestinal recovery in patients having open colorectal surgery. Data demonstrating the benefit of perioperative alvimopan for the minimally invasive surgical approach are inconsistent. The aim of this study is to determine colorectal surgery groups that benefit from perioperative alvimopan.

METHODS

This is a retrospective cohort analysis of colorectal surgery patients who had, and patients who did not have, perioperative alvimopan in the Michigan Surgical Quality Collaborative regional risk-adjusted database from 2018 through 2021. Main outcome measures were postoperative length of hospital stay, time to return of bowel function, and postoperative ileus.

RESULTS

There were 10,010 patients (30.3% open, 40.5% laparoscopic, 12.7% hand-assist laparoscopic, 43.5% robotic) who met inclusion criteria-4919 received alvimopan in the perioperative period and 5091 did not. When compared to those not receiving alvimopan, unadjusted outcomes showed that the alvimopan group had significantly shorter postoperative length of stay (4.75 days vs 5.5 days, p < 0.001), shorter time to return of bowel function (1.61 days vs 2.01 days, p < 0.001) and less postoperative ileus (5.45% vs 7.94%, p < 0.001). After adjustment, regression models confirmed that alvimopan was associated with an 9.6% reduction in hospital length of stay (p < 0.001), a 14.9% shorter time to return of bowel function (p < 0.001), and a 42.1% reduction in postoperative ileus (p < 0.001). Subgroup analysis showed significant benefit of alvimopan for all three outcomes in patients having the minimally invasive approach.

CONCLUSIONS

Alvimopan is associated with shorter hospital length of stay, shorter time to return of bowel function, and decreased postoperative ileus when administered to patients undergoing colorectal surgery. Benefit is not limited to the open approach and includes minimally invasive laparoscopic and robotic colorectal procedures.

Incidence and Risk Factors for Postoperative Ileus after Posterior Surgery in Adolescent Idiopathic Scoliosis

OBJECTIVE

Postoperative ileus (POI) is a relatively common complication after spinal fusion surgery, which can lead to delayed recovery, prolonged length of stay and increased medical costs. However, little is known about the incidence and risk factors of POI after corrective surgery for patients with adolescent idiopathic scoliosis (AIS). This study was performed to report the incidence of POI and identify the independent risk factors for POI after postoperative corrective surgery.

METHODS

In this retrospective cohort study, A total of 318 patients with AIS who underwent corrective surgery from April 2015 to February 2021 were enrolled and divided into two groups: those with POI and those without POI. The Student's t test, Mann-Whitney U test, and Pearson's chi-square test were used to compare the two groups regarding patient demographics and preoperative characteristics (age, sex and the major curve type), intraoperative and postoperative parameters (lowest instrumented vertebra [LIV], number of screws, and length of stay), radiographic parameters (T5-12 thoracic kyphosis [TK], T10-L2 thoracolumbar kyphosis and height [TLK and T10-L2 height], L1-S1 lumbar lordosis [LL], and L1-5 height). Then, a multivariate logistic regression analysis was used to identify independent risk factors for POI, and a receiver operating characteristic (ROC) curve was performed to assess the predictive values of these risk factors.

RESULTS

Forty-two (13.2%) of 318 patients who developed POI following corrective surgery were identified. The group with POI had a significantly longer length of stay, more lumbar screws, higher proportions of a major lumbar curve and lumbar anterior screw breech, and a lower LIV. Among radiographic parameters, the mean lumbar Cobb angle at baseline, the changes in the lumbar Cobb angle, and T10-L2 and L1-5 height from before to after surgery were significantly larger in the group with POI than in the group without POI. Multivariate logistic regression analysis showed that large changes in T10-L2 (odds ratio [OR] =2.846, P = 0.007) and L1-5 height (OR = 31.294, p = 0.000) and lumbar anterior screw breech (OR = 5.561, P = 0.006) were independent risk factors for POI. The cutoff values for the changes in T10-L2 and L1-5 height were 1.885 cm and 1.195 cm, respectively.

CONCLUSION

In this study, we identified that large changes in T10-L2 and L1-5 height and lumbar anterior screw breech were independent risk factors for POI after corrective surgery. Improving the accuracy of pedicle screw placement might reduce the incidence of POI, and greater attention should be given to patients who are likely to have large changes in T10-L2 and L1-5 height after corrective surgery.

Reductions in All-Cause Mortality Associated with the Use of Methylnaltrexone for Opioid-Induced Bowel Disorders: A Pooled Analysis

OBJECTIVE

Preclinical and clinical studies suggest that activation of the µ-opioid receptor may reduce overall survival and increase the risk for all-cause mortality in patients with cancer and noncancer pain. Methylnaltrexone, a selective, peripherally acting µ-opioid receptor antagonist, has demonstrated efficacy for the treatment of opioid-induced constipation. This retrospective analysis of 12 randomized, double-blind, placebo-controlled studies of methylnaltrexone evaluated the treatment of opioid-induced bowel disorders in patients with advanced illness or noncancer pain.

METHODS

The risk of all-cause mortality within 30 days after the last dose of study medication during the double-blind phase was compared between methylnaltrexone and placebo groups. The data were further stratified by cancer vs noncancer, age, gender, and acute vs chronic diagnoses.

RESULTS

Pooled data included 2,526 methylnaltrexone-treated patients of which 33 died, and 1,192 placebo-treated patients of which 35 died. The mortality rate was 17.8 deaths/100 person-years of exposure in the methylnaltrexone group and 49.5 deaths/100 person-years of exposure for the placebo group. The all-cause mortality risk was significantly lower among patients receiving methylnaltrexone compared with placebo (hazard ratio: 0.399, 95% confidence interval: 0.25, 0.64; P = .0002), corresponding to a 60% risk reduction. Significant risk reductions were observed for those receiving methylnaltrexone who had cancer or chronic diagnoses. Methylnaltrexone-treated patients had a significantly reduced mortality risk compared with placebo regardless of age or gender.

CONCLUSIONS

Methylnaltrexone reduced all-cause mortality vs placebo treatment across multiple trials, suggesting methylnaltrexone may confer survival benefits in patients with opioid-induced bowel disorders taking opioids for cancer-related or chronic noncancer pain.

Impact of intravenous dexmedetomidine on gastrointestinal function recovery after laparoscopic hysteromyomectomy: a randomized clinical trial

Postoperative intestinal ileus is common after laparoscopic surgery, the incidence of those after hysterectomy was 9.2%. Anesthesia is one of the independent risk factors of postoperative ileus. Dexmedetomidine has been widely used in perioperative anesthesia and previous reports suggested that intraoperative dexmedetomidine may be associated with the improvement of gastrointestinal function recovery after abdominal surgery. We hypothesized that dexmedetomidine could improve gastrointestinal function recovery after laparoscopic hysteromyomectomy. Participants in elective laparoscopic hysteromyomectomy were enrolled with a single dose of 0.5 μg kg⁻¹ dexmedetomidine or the same volume of placebo intravenously administered for 15 min, followed by continuous pumping of 0.2 μg kg⁻¹ h⁻¹ of corresponding drugs until 30 min before the end of surgery. The primary outcome was the time to first flatus. Secondary outcomes were the time to first oral feeding and the first defecation, the occurrence of flatulence, pain score and postoperative nausea and vomiting until 48 h after the surgery. Eventually, 106 participants (54 in dexmedetomidine group and 52 in placebo group) were included for final analysis. The time to first flatus (SD, 25.83 [4.18] vs 27.67 [3.77], P = 0.019), oral feeding time (SD, 27.29 [4.40] vs 28.92 [3.82], P = 0.044), the time to first defecation (SD, 59.82 [10.49] vs 63.89 [7.71], P = 0.025), abdominal distension (n%, 12 (22.2) vs 21 (40.4), P = 0.044), PONV at 24 h (n%, 10 (18.5) vs 19 (36.5), P = 0.037), NRS 6 h (3.15(0.68) vs 3.46 (0.87), P = 0.043) and NRS 12 h (3.43 (0.88) vs 3.85 (0.85), P = 0.014) of dexmedetomidine group were significantly shorter than those of the placebo group. Intraoperative dexmedetomidine reduced the time to first flatus, first oral feeding, and first defecation. These results suggested that this treatment may be a feasible strategy for improving postoperative gastrointestinal function recovery in patients undergoing laparoscopic hysteromyomectomy.

Peripherally restricted transthyretin-based delivery system for probes and therapeutics avoiding opioid-related side effects

Several investigations into the sites of action of opioid analgesics have utilized peripherally acting mu-opioid receptor antagonists (PAMORAs), which have been incorrectly assumed to possess limited permeability across the blood-brain barrier. Unfortunately, the poor pharmacokinetic properties of current PAMORAs have resulted in misunderstandings of the role of central nervous system and gastrointestinal tract in precipitating side effects such as opioid-induced constipation. Here, we develop a drug delivery approach for restricting the passage of small molecules across the blood-brain barrier. This allows us to develop naloxone- and oxycodone-based conjugates that display superior potency, peripheral selectivity, pharmacokinetics, and efficacy in rats compared to other clinically used PAMORAs. These probes allow us to demonstrate that the mu-opioid receptors in the central nervous system have a fundamental role in precipitating opioid-induced constipation. Therefore, our conjugates have immediate use as pharmacological probes and potential therapeutic agents for treating constipation and other opioid-related side effects.

Antagonists of the Mu-Opioid Receptor in the Cancer Patient: Fact or Fiction?

Purpose of Review

Antagonists of mu-opioid receptor role in cancer progression remains to be elucidated. The objective of this review was to summarize the available evidence on antagonists of mu-opioid receptor effect on tumor progression and prognosis in different types of cancers and an evaluation of the available findings on their mechanism of action.

Recent Findings

We have found studies related to methylnaltrexone (MNTX) and naltrexone (NTX) usage in cancer outcomes-related setting. We found consistent preclinical evidence of a potential action of MNTX and NTX on cancer growth and spread mediated mainly by effect on the opioid growth factor receptor (OGFr) axis, which results in depressed cell replication. However, clinical results are scarce and limited to poor-quality evidence.

Summary

Further high-quality studies are warranted to study antagonists of mu-opioid receptor role as a therapeutic option in different types of cancer, especially in patients where the classical treatment causes unacceptable side effects.

Perioperative subcutaneous methylnaltrexone does not enhance gastrointestinal recovery after posterior short-segment spinal arthrodesis surgery: a randomized controlled trial

BACKGROUND CONTEXT

Postoperative ileus is a major barrier to gastrointestinal recovery following surgery. Opioid analgesics likely play an important causative role, particularly in spinal or orthopedic surgeries not involving bowel manipulation. Methylnaltrexone, a peripherally-acting µ-opioid receptor antagonist, is a potential prophylactic treatment.

PURPOSE

To assess the influence of perioperative subcutaneous methylnaltrexone administration on gastrointestinal recovery following short-segment lumbar arthrodesis surgeries.

DESIGN

This is a randomized, double-blind, controlled trial.

PATIENT SAMPLE

Eligible patients undergoing posterior short-segment lumbar arthrodesis surgeries at a single institution between February 2019 and April 2021 were enrolled in this study.

OUTCOME MEASURES

The primary outcome measure was time-to-first bowel movement. Secondary outcome measures included time-to-discharge/discharge eligibility. Exploratory outcome measures included daily postoperative opioid consumption and pain scores.

METHODS

In this study, eligible patients were enrolled to receive either methylnaltrexone or placebo perioperatively. Time-to-bowel movement, time-to-discharge/discharge eligibility, intra and postoperative analgesic administration, and pain scores were recorded and compared.

RESULTS

Eighty two patients in total were enrolled; 41 to the methylnaltrexone and 41 to the placebo group. Both groups were similar in their baseline characteristics. There was no difference in median (range) time-to-bowel movement between the 2 groups [61.8 hours (35.7-93.6) versus 50.7 hours (17.8-110.8), p = .391]. There was also no difference in time-to-discharge/discharge eligibility [105.0 hours (81.0 - 201.3) versus 90.7 (77.5 - 184.5), p=.784]. Finally, there were no differences in either postoperative opioid consumption or numeric rating scores for back, leg, or abdominal pain on postoperative days 0 to 4 (p>.05).

CONCLUSIONS

Methylnaltrexone did not accelerate gastrointestinal recovery and did not affect opioid consumption or pain scores following short-segment spinal surgery as compared to placebo. Additional studies will be needed to identify effective opioid receptor antagonist dosing regimens for patients undergoing either short- or long-segment spinal arthrodesis procedures.

Antiproliferative and palliative activity of flavonoids in colorectal cancer

Flavonoids are plant bioactive compounds of great interest in nutrition and pharmacology, due to their remarkable properties as antioxidant, anti-inflammatory, antibacterial, antifungal and antitumor drugs. More than 5000 different flavonoids exist in nature, with a huge structural diversity and a plethora of interesting pharmacological properties. In this work, five flavonoids were tested for their potential use as antitumor drugs against three CRC cell lines (HCT116, HT-29 and T84). These cell lines represent three different stages of this tumor, one of which is metastatic. Xanthohumol showed the best antitumor activity on the three cancer cell lines, even better than that of the clinical drug 5-fluorouracil (5-FU), although no synergistic effect was observed in the combination therapy with this drug. On the other hand, apigenin and luteolin displayed slightly lower antitumor activities on these cancer cell lines but showed a synergistic effect in combination with 5-FU in the case of HTC116, which is of potential clinical interest. Furthermore, a literature review highlighted that these flavonoids show very interesting palliative effects on clinical symptoms such as diarrhea, mucositis, neuropathic pain and others often associated with the chemotherapy treatment of CRC. Flavonoids could provide a double effect for the combination treatment, potentiating the antitumor effect of 5-FU, and simultaneously, preventing important side effects of 5-FU chemotherapy.

Selective Opioid Antagonists Following Bowel Resection for Prevention of Postoperative Ileus: a Systematic Review and Meta-analysis

BACKGROUND

Postoperative ileus (POI) remains a common complication following bowel resection. Selective opioid antagonists have been increasingly studied as prophylactic pharmaceutical aids to reduce rates of POI. The aim of this study was to evaluate the impact of selective opioid antagonists on return of bowel function following bowel resection.

METHODS

MEDLINE, Embase, and CENTRAL were systematically searched. Articles were included if they compared the incidence of POI and/or length of stay (LOS) in patients receiving and not receiving selective opioid antagonists following elective bowel resection. A pairwise meta-analyses using inverse variance random effects was performed.

RESULTS

From 636 citations, 30 studies with 45,051 patients receiving selective opioid antagonists (51.3% female, mean age: 60.9) and 55,071 patients not receiving selective opioid antagonists (51.2% female, mean age: 61.1) were included. Patients receiving selective opioid antagonists had a significantly lower rate of POI (10.1% vs. 13.8%, RR 0.68, 95%CI 0.63-0.75, p < 0.01). Selective opioid antagonists also significantly reduced LOS (MD - 1.08, 95%CI - 1.47 to - 0.69, p < 0.01), readmission (RR 0.94, 95%CI 0.89-0.99, p = 0.03), and 30-day morbidity (RR 0.85, 95%CI 0.79-0.90, p < 0.01). Improvements in LOS, readmission rate, and morbidity were not significant when analysis was limited to laparoscopic surgery. There was no significant difference in inpatient healthcare costs (SMD - 0.33, 95%CI - 0.71-0.04, p = 0.08).

CONCLUSIONS

Rate of POI decreases with the use of selective opioid antagonists in patients undergoing bowel resection. Selective opioid antagonists also improve LOS, rates of readmission, and 30-day morbidity for patients undergoing open bowel resection. Addition of these medications to enhance recovery after surgery protocols should be considered.

State-of-the-art colorectal disease: postoperative ileus

PURPOSE

Postoperative Ileus (POI) remains an important complication for patients after abdominal surgery with an incidence of 10-27% representing an everyday issue for abdominal surgeons. It accounts for patients' discomfort, increased morbidity, prolonged hospital stays, and a high economic burden. This review outlines the current understanding of POI pathophysiology and focuses on preventive treatments that have proven to be effective or at least show promising effects.

METHODS

Pathophysiology and recommendations for POI treatment are summarized on the basis of a selective literature review.

RESULTS

While a lot of therapies have been researched over the past decades, many of them failed to prove successful in meta-analyses. To date, there is no evidence-based treatment once POI has manifested. In the era of enhanced recovery after surgery or fast track regimes, a few approaches show a beneficial effect in preventing POI: multimodal, opioid-sparing analgesia with placement of epidural catheters or transverse abdominis plane block; μ-opioid-receptor antagonists; and goal-directed fluid therapy and in general the use of minimally invasive surgery.

CONCLUSION

The results of different studies are often contradictory, as a concise definition of POI and reliable surrogate endpoints are still absent. These will be needed to advance POI research and provide clinicians with consistent data to improve the treatment strategies.