Endogenous morphine levels increase following cardiac surgery as part of the antiinflammatory response?

Epidural analgesia for adults undergoing cardiac surgery with or without cardiopulmonary bypass

BACKGROUND

General anaesthesia combined with epidural analgesia may have a beneficial effect on clinical outcomes. However, use of epidural analgesia for cardiac surgery is controversial due to a theoretical increased risk of epidural haematoma associated with systemic heparinization. This review was published in 2013, and it was updated in 2019.

OBJECTIVES

To determine the impact of perioperative epidural analgesia in adults undergoing cardiac surgery, with or without cardiopulmonary bypass, on perioperative mortality and cardiac, pulmonary, or neurological morbidity.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase in November 2018, and two trial registers up to February 2019, together with references and relevant conference abstracts.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) including adults undergoing any type of cardiac surgery under general anaesthesia and comparing epidural analgesia versus another modality of postoperative pain treatment. The primary outcome was mortality.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We included 69 trials with 4860 participants: 2404 given epidural analgesia and 2456 receiving comparators (systemic analgesia, peripheral nerve block, intrapleural analgesia, or wound infiltration). The mean (or median) age of participants varied between 43.5 years and 74.6 years. Surgeries performed were coronary artery bypass grafting or valvular procedures and surgeries for congenital heart disease. We judged that no trials were at low risk of bias for all domains, and that all trials were at unclear/high risk of bias for blinding of participants and personnel taking care of study participants.Epidural analgesia versus systemic analgesiaTrials show there may be no difference in mortality at 0 to 30 days (risk difference (RD) 0.00, 95% confidence interval (CI) -0.01 to 0.01; 38 trials with 3418 participants; low-quality evidence), and there may be a reduction in myocardial infarction at 0 to 30 days (RD -0.01, 95% CI -0.02 to 0.00; 26 trials with 2713 participants; low-quality evidence). Epidural analgesia may reduce the risk of 0 to 30 days respiratory depression (RD -0.03, 95% CI -0.05 to -0.01; 21 trials with 1736 participants; low-quality evidence). There is probably little or no difference in risk of pneumonia at 0 to 30 days (RD -0.03, 95% CI -0.07 to 0.01; 10 trials with 1107 participants; moderate-quality evidence), and epidural analgesia probably reduces the risk of atrial fibrillation or atrial flutter at 0 to 2 weeks (RD -0.06, 95% CI -0.10 to -0.01; 18 trials with 2431 participants; moderate-quality evidence). There may be no difference in cerebrovascular accidents at 0 to 30 days (RD -0.00, 95% CI -0.01 to 0.01; 18 trials with 2232 participants; very low-quality evidence), and none of the included trials reported any epidural haematoma events at 0 to 30 days (53 trials with 3982 participants; low-quality evidence). Epidural analgesia probably reduces the duration of tracheal intubation by the equivalent of 2.4 hours (standardized mean difference (SMD) -0.78, 95% CI -1.01 to -0.55; 40 trials with 3353 participants; moderate-quality evidence). Epidural analgesia reduces pain at rest and on movement up to 72 hours after surgery. At six to eight hours, researchers noted a reduction in pain, equivalent to a reduction of 1 point on a 0 to 10 pain scale (SMD -1.35, 95% CI -1.98 to -0.72; 10 trials with 502 participants; moderate-quality evidence). Epidural analgesia may increase risk of hypotension (RD 0.21, 95% CI 0.09 to 0.33; 17 trials with 870 participants; low-quality evidence) but may make little or no difference in the need for infusion of inotropics or vasopressors (RD 0.00, 95% CI -0.06 to 0.07; 23 trials with 1821 participants; low-quality evidence).Epidural analgesia versus other comparatorsFewer studies compared epidural analgesia versus peripheral nerve blocks (four studies), intrapleural analgesia (one study), and wound infiltration (one study). Investigators provided no data for pulmonary complications, atrial fibrillation or flutter, or for any of the comparisons. When reported, other outcomes for these comparisons (mortality, myocardial infarction, neurological complications, duration of tracheal intubation, pain, and haemodynamic support) were uncertain due to the small numbers of trials and participants.

AUTHORS' CONCLUSIONS

Compared with systemic analgesia, epidural analgesia may reduce the risk of myocardial infarction, respiratory depression, and atrial fibrillation/atrial flutter, as well as the duration of tracheal intubation and pain, in adults undergoing cardiac surgery. There may be little or no difference in mortality, pneumonia, and epidural haematoma, and effects on cerebrovascular accident are uncertain. Evidence is insufficient to show the effects of epidural analgesia compared with peripheral nerve blocks, intrapleural analgesia, or wound infiltration.

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.

Endogenous morphine-6-glucuronide (M6G) is present in the plasma of patients: validation of a specific anti-M6G antibody for clinical and basic research

Endogenous morphine and its derivatives (morphine-6-glucuronide [M6G]; morphine-3-glucuronide [M3G]) are formed by mammalian cells from dopamine. Changes in the concentrations of endogenous morphine have been demonstrated in several pathologies (sepsis, Parkinson's disease, etc.), and they might be relevant as pathological markers. While endogenous morphine levels are detectable using enzyme-linked immunosorbant assay (ELISA), mass spectrometry (MS) analysis was, so far, the only approach to detect and quantify M6G. This study describes the preparation of a specific anti-M6G rabbit polyclonal antibody and its validation. The specificity of this antibody was assessed against 30 morphine-related compounds. Then, a M6G-specific ELISA-assay was tested to quantify M6G in the plasma of healthy donors, morphine-treated, and critically ill patients. The antibody raised against M6G displays a strong affinity for M6G, codeine-6-glucuronide, and morphine-3-6-glucuronide, whereas only weak cross-reactivities were observed for the other compounds. Both M6G-ELISA and LC-MS/MS approaches revealed the absence of M6G in the plasma of healthy donors (controls, n = 8). In all positive donors treated with morphine-patch (n = 5), M6G was detected using both M6G-ELISA and LC-MS/MS analysis. Finally, in a study on critically ill patients with circulating endogenous morphine (n = 26), LC-MS/MS analysis revealed that 73% of the positive-patients (19 of 26), corresponding to high M6G-levels in M6G-ELISA, contained M6G. In conclusion, we show that endogenous M6G can be found at higher levels than morphine in the blood of morphine-naive patients. With respect to the interest of measuring endogenous M6G in pathologies, we provide evidences that our ELISA procedure represents a powerful tool as it can easily and specifically detect endogenous M6G levels.

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.

Topical morphine for oral mucositis in children: dose finding and absorption

CONTEXT

Systemic opioids for painful chemotherapy-induced oral mucositis in children often result in unsatisfactory pain relief and a high frequency of side effects. Opioids applied topically can produce analgesia by binding to opioid receptors on peripheral terminals of sensory neurons. These receptors are upregulated during inflammation, for example, in oral mucositis.

OBJECTIVES

The aims of this study were to investigate the dose-response relationship (n=7) and the potential absorption of topical morphine (n=5) across oral mucosa in children with oral mucositis.

METHODS

The dose-response study was conducted according to a sequential study design (Dixon's Up-and-Down method) for topical morphine doses of 0.025-0.400mg/kg, with the decrease in oral pain score as the primary outcome. To assess potential absorption across oral mucosa after a single dose of topical morphine of 0.050mg/kg, blood samples were drawn and the plasma concentrations of morphine and metabolites were determined by high-pressure liquid chromatography.

RESULTS

A decrease in oral pain score of ≥36% was achieved in six of seven patients in the dose-response part of the study. Plasma concentrations of morphine and metabolites were well below effective analgesic levels.

CONCLUSION

No obvious dose-response effect was found for topical morphine doses of 0.025-0.400mg/kg, and topically applied morphine was not absorbed in clinically relevant doses. However, this study was limited by the small number of patients and the allowance of a systemic opioid as rescue medication. Thus, randomized controlled studies are needed to further investigate the analgesic properties of topical morphine.

Pathogenesis and clinical and economic consequences of postoperative ileus

Postoperative ileus is a preventable disease with surprising economic consequences. Understanding the triad of dysmotility in conjunction with an enhanced recovery program improves patient outcome, decreases length of stay in hospital, and lowers the cost. Alvimopan and other investigational promotility medications can help attain these goals. Surgeons should avoid labeling all postoperative abdominal distention as ileus, which not only prevents timely diagnosis and treatment of early postoperative small bowel obstruction or acute colonic pseudo-obstruction but also increases patient morbidity and mortality.

Mapping of endogenous morphine-like compounds in the adult mouse brain: Evidence of their localization in astrocytes and GABAergic cells

Endogenous morphine, morphine-6-glucuronide, and codeine, which are structurally identical to vegetal alkaloids, can be synthesized by mammalian cells from dopamine. However, the role of brain endogenous morphine and its derivative compounds is a matter of debate, and knowledge about its distribution is lacking. In this study, by using a validated antibody, we describe a precise mapping of endogenous morphine-like compounds (morphine and/or its glucuronides and/or codeine) in the mouse brain. First, a mass spectrometry approach confirmed the presence of morphine and codeine in mouse brain, but also, of morphine-6-glucuronide and morphine-3-glucuronide representing two metabolites of morphine. Second, light microscopy allowed us to observe immunopositive cell somas and cytoplasmic processes throughout the mouse brain. Morphine-like immunoreactivity was present in various structures including the hippocampus, olfactory bulb, band of Broca, basal ganglia, and cerebellum. Third, by using confocal microscopy and immunofluroscence co-localization, we characterized cell types containing endogenous opiates. Interestingly, we observed that morphine-like immunoreactivity throughout the encephalon is mainly present in γ-aminobutyric acid (GABA)ergic neurons. Astrocytes were also labeled throughout the entire brain, in the cell body, in the cytoplasmic processes, and in astrocytic feet surrounding blood vessels. Finally, ultrastructural localization of morphine-like immunoreactivity was determined by electron microscopy and showed the presence of morphine-like label in presynaptic terminals in the cerebellum and postsynaptic terminals in the rest of the mouse brain. In conclusion, the presence of endogenous morphine-like compounds in brain regions not usually involved in pain modulation opens the exciting opportunity to extend the role and function of endogenous alkaloids far beyond their analgesic functions.

Endogenous morphine-like compound immunoreactivity increases in parkinsonism

Morphine is endogenously synthesized in the central nervous system and endogenous dopamine is thought to be necessary for endogenous morphine formation. As Parkinson's disease results from the loss of dopamine and is associated with central pain, we considered how endogenous morphine is regulated in the untreated and l-DOPA-treated parkinsonian brain. However, as the cellular origin and overall distribution of endogenous morphine remains obscure in the pathological adult brain, we first characterized the distribution of endogenous morphine-like compound immunoreactive cells in the rat striatum. We then studied changes in the endogenous morphine-like compound immunoreactivity of medium spiny neurons in normal, Parkinson's disease-like and l-DOPA-treated Parkinson's disease-like conditions in experimental (rat and monkey) and human Parkinson's disease. Our results reveal an unexpected dramatic upregulation of neuronal endogenous morphine-like compound immunoreactivity and levels in experimental and human Parkinson's disease, only partially normalized by l-DOPA treatment. Our data suggest that endogenous morphine formation is more complex than originally proposed and that the parkinsonian brain experiences a dramatic upregulation of endogenous morphine immunoreactivity. The functional consequences of such endogenous morphine upregulation are as yet unknown, but based upon the current knowledge of morphine signalling, we hypothesize that it is involved in fatigue, depression and pain symptoms experienced by patients with Parkinson's disease.

The opioid component of delayed gastrointestinal recovery after bowel resection

INTRODUCTION

Patients undergoing bowel resection or other major abdominal surgery experience a period of delayed gastrointestinal recovery associated with increased postoperative morbidity and longer hospital length of stay. Symptoms include nausea, vomiting, abdominal distension, bloating, pain, intolerance to solid or liquid food, and inability to pass stool or gas. The exact cause of delayed gastrointestinal recovery is not known, but several factors appear to play a central role, namely the neurogenic, hormonal, and inflammatory responses to surgery and the response to exogenous opioid analgesics and endogenous opioids.

DISCUSSION

Stimulation of opioid receptors localized to neurons of the enteric nervous system inhibits coordinated gastrointestinal motility and fluid absorption, thereby contributing to delayed gastrointestinal recovery and its associated symptoms. Given the central role of opioid analgesics in delayed gastrointestinal recovery, a range of opioid-sparing techniques and pharmacologic agents, including opioid receptor antagonists, have been developed to facilitate faster restoration of gastrointestinal function after bowel resection when used as part of a multimodal accelerated care pathway. This review discusses the etiology of opioid-induced gastrointestinal dysfunction as well as clinical approaches that have been evaluated in controlled clinical trials to reduce the opioid component of delayed gastrointestinal recovery.

Pathogenesis and clinical and economic consequences of postoperative ileus

Postoperative ileus (POI) occurs frequently in patients undergoing major abdominal surgery; and only recently has there been renewed interest in understanding the pathogenesis, etiology, clinical manifestations, and clinical and economic consequences related to POI. This interest has been spurred by the potential access to novel pharmaceutical options for the management of POI. POI has a complex and multimodal pathophysiology including neurogenic, inflammatory, hormonal, and pharmacologic components. The clinical manifestations are clinically obvious and include abdominal distention, pain, nausea, vomiting, and inability to pass stools or tolerate a solid diet. Prolonged ileus has been defined as persistence of these symptoms for more than 4 days after major abdominal surgery; however the goal should be to reduce the incidence of these symptoms immediately after surgery. Clearly, the magnitude of the surgical stress and usage of opioid analgesia are the predominant causes of POI. The unappreciated sequelae of POI include increased rates in adverse surgical wound healing, reduced ambulation, atelectasis, pneumonia, urinary infections, and deep vein thrombosis. The secondary impact of these complications includes increased hospital length of stay, resource use, and healthcare costs. POI is common and the impact is underestimated. The addition of alvimopan as the first in class μ-opioid inhibitor has demonstrated consistent benefit in reducing the incidence and impact of POI with reductions in length of hospital stay. POI is a common, and underappreciated complication of major abdominal surgery, and clinicians should be aware of the clinical care options, including novel pharmaceutical agents, that can successfully reduce the incidence of this postoperative complication.

Catechol-O-methyltransferase: potential relationship to idiopathic hypertension

Catecholamine signaling pathways in the peripheral and central nervous systems (PNS, CNS, respectively) utilize catechol-O-methyltransferase (COMT) as a major regulatory enzyme responsible for deactivation of dopamine (DA), norepinephrine (NE) and epinephrine (E). Accordingly, homeostasis of COMT gene expression is hypothesized to be functionally linked to regulation of autonomic control of normotensive vascular events. Recently, we demonstrated that morphine administration in vitro resulted in decreased cellular concentrations of COMT-encoding mRNA levels, as compared to control values. In contrast, cells treated with E up regulated their COMT gene expression. In sum, these observations indicate a potential reciprocal linkage between end product inhibition of COMT gene expression by E and morphine. Interestingly, the observed effects of administered E on COMT gene expression suggest an enhancement of its own catabolism or, reciprocally, a stimulation morphine biosynthesis.

Endogenous morphine levels after laparoscopic versus open colectomy

Background

Endogenous morphine may be a component of the acute-phase response to surgical trauma that affects both hospital stay and gastrointestinal motility. The purpose of this study was to assess the responses of endogenous morphine, stress hormones and cytokines following laparoscopic and open colectomy.

Methods

Twenty patients who underwent a laparoscopic colectomy were compared with ten who had an open procedure. Data collected included operative blood loss, operating time and time to pass flatus. Plasma endogenous morphine was measured before and immediately after operation, and 3, 24 and 48 h later.

Results

Age was comparable in the two groups. Operating time (mean 92·2 versus 61·3 min), time to tolerance of solid food (56·8 versus 103·6 h) and hospital stay (median 4 versus 6 days) were all significantly longer in the open group. Endogenous morphine levels rose immediately after open colectomy only and were higher than those after laparoscopic colectomy (8·69 versus 1·97 ng/ml; P &lt; 0·001). Levels remained significantly higher in the laparoscopic group at 3 h (10·36 versus 0·52 ng/ml; P &lt; 0·001) and 24 h, but were similar in both groups after 48 h.

Conclusion

There is a greater degree of morphine synthesis after open than laparoscopic colectomy.

Endogenous morphine levels are increased in sepsis: a partial implication of neutrophils

Background

Mammalian cells synthesize morphine and the respective biosynthetic pathway has been elucidated. Human neutrophils release this alkaloid into the media after exposure to morphine precursors. However, the exact role of endogenous morphine in inflammatory processes remains unclear. We postulate that morphine is released during infection and can be determined in the serum of patients with severe infection such as sepsis.

Methodology

The presence and subcellular immunolocalization of endogenous morphine was investigated by ELISA, mass spectrometry analysis and laser confocal microscopy. Neutrophils were activated with Interleukin-8 (IL-8) or lipopolysaccharide (LPS). Morphine secretion was determined by a morphine-specific ELISA. μ opioid receptor expression was assessed with flow cytometry. Serum morphine concentrations of septic patients were determined with a morphine-specific ELISA and morphine identity was confirmed in human neutrophils and serum of septic patients by mass spectrometry analysis. The effects of the concentration of morphine found in serum of septic patients on LPS-induced release of IL-8 by human neutrophils were tested.

Principal Findings

We confirmed the presence of morphine in human neutrophil extracts and showed its colocalisation with lactoferrin within the secondary granules of neutrophils. Morphine secretion was quantified in the supernatant of activated human polymorphonuclear neutrophils in the presence and absence of Ca²⁺. LPS and IL-8 were able to induce a significant release of morphine only in presence of Ca²⁺. LPS treatment increased μ opioid receptor expression on neutrophils. Low concentration of morphine (8 nM) significantly inhibited the release of IL-8 from neutrophils when coincubated with LPS. This effect was reversed by naloxone. Patients with sepsis, severe sepsis and septic shock had significant higher circulating morphine levels compared to patients with systemic inflammatory response syndrome and healthy controls. Mass spectrometry analysis showed that endogenous morphine from serum of patient with sepsis was identical to poppy-derived morphine.

Conclusions

Our results indicate that morphine concentrations are increased significantly in the serum of patients with systemic infection and that morphine is, at least in part, secreted from neutrophils during sepsis. Morphine concentrations equivalent to those found in the serum of septic patients significantly inhibited LPS-induced IL-8 secretion in neutrophils.

Epidural analgesia improves outcome in cardiac surgery: a meta-analysis of randomized controlled trials

OBJECTIVE

The authors conducted a review of randomized studies to determine whether there were any advantages for clinically relevant outcomes by adding epidural analgesia in patients undergoing cardiac surgery under general anesthesia.

DESIGN

Meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 2366 patients from 33 randomized trials.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

DATA SOURCES AND STUDY SELECTION

PubMed, BioMedCentral, CENTRAL, EMBASE, Cochrane Central Register of Controlled Trials, and conference proceedings were searched (updated January 2008) for randomized trials that compared general anesthesia with an anesthetic plan including general anesthesia and epidural analgesia in cardiac surgery. Two independent reviewers appraised study quality, with divergences resolved by consensus. Overall analysis showed that epidural analgesia reduced the risk of the composite endpoint mortality and myocardial infarction (30/1125 [2.7%] in the epidural group v 64/1241 [5.2%] in the control arm, odds ratio [OR] = 0.61 [0.40-0.95], p = 0.03 number needed to treat [NNT] = 40), the risk of acute renal failure (35/590 [5.9%] in the epidural group v 54/618 [8.7%] in the control arm, OR = 0.56 [0.34-0.93], p = 0.02, NNT = 36), and the time of mechanical ventilation (weighted mean differences = -2.48 hours [-2.64, -2.32], p < 0.001).

CONCLUSIONS

This analysis suggested that epidural analgesia on top of general anesthesia reduced the incidence of perioperative acute renal failure, the time on mechanical ventilation, and the composite endpoint of mortality and myocardial infarction in patients undergoing cardiac surgery.

Methylnaltrexone, a new peripherally acting mu-opioid receptor antagonist being evaluated for the treatment of postoperative ileus

Postoperative ileus (POI), a transient impairment of bowel function, is considered an inevitable response after open abdominal surgery. It leads to significant patient morbidity and increased hospital costs and length of stay. The pathophysiology is multifactorial, involving neurogenic, hormonal, inflammatory and pharmacologic mediators. Several treatments have been shown to reduce the duration of POI, and a multimodal approach combining several of these interventions seems to be the most effective treatment option. Various drug therapies have been evaluated for the treatment of POI, although most have not shown any benefit. Peripherally active mu-opioid receptor antagonists are a new class of compounds that selectively block the peripheral (i.e., gastrointestinal [GI]) effects of opioids while preserving centrally mediated analgesia. Recently, alvimopan was approved in the US for the treatment of POI after abdominal surgery with bowel resection. Methylnaltrexone is a peripherally active mu-opioid receptor antagonist that has been shown to antagonize the inhibitory effects of opioids on GI transit without impairing analgesia. Phase II data indicated that methylnaltrexone was effective for improving GI recovery, reducing POI and shortening the time to discharge readiness in patients who underwent segmental colectomy. Two Phase III trials have been completed, and one is underway at present. Preliminary results from the two completed trials indicate that methylnaltrexone was not better than placebo for the primary or secondary outcomes. Further analyses of these data, clinical trial designs and the various dosage forms are necessary to determine the potential role of methylnaltrexone in the treatment of POI.

The presence of endogenous morphine signaling in animals

Recent empirical findings have contributed valuable mechanistic information in support of a regulated de novo biosynthetic pathway for chemically authentic morphine and related morphinan alkaloids within animal cells. Importantly, we and others have established that endogenously expressed morphine represents a key regulatory molecule effecting local circuit autocrine/paracrine cellular signaling via a novel mu(3) opiate receptor coupled to constitutive nitric oxide production and release. The present report provides an integrated review of the biochemical, pharmacological, and molecular demonstration of mu(3) opiate receptors in historical linkage to the elucidation of mechanisms of endogenous morphine production by animal cells and organ systems. Ongoing research in this exciting area provides a rare window of opportunity to firmly establish essential biochemical linkages between dopamine, a morphine precursor, and animal biosynthetic pathways involved in morphine biosynthesis that have been conserved throughout evolution.

New therapies in the treatment of postoperative ileus after gastrointestinal surgery

Postoperative ileus after gastrointestinal surgery results from many factors, including the effects of surgical trauma, anesthetic agents, hyperactivity of the sympathetic nervous system, local inflammatory reactions, and the use of opioids in the postoperative period. Postoperative ileus can lead to potential complications and may prolong patients' hospitalization, thereby leading to an increase in healthcare costs. There have been recent efforts to improve the understanding of the pathogenesis of postoperative ileus and to develop new treatments to prevent or minimize its occurrence. Here, we present a review of the factors related to the development of postoperative ileus and new therapies directed at its prevention.

Endogenous morphine/nitric oxide-coupled regulation of cellular physiology and gene expression: implications for cancer biology

Cancer is a simplistic, yet complicated, process that promotes uncontrolled growth. In this regard, this unconstrained proliferation may represent primitive phenomena whereby cellular regulation is suspended or compromised. Given the new empirical evidence for a morphinergic presence and its profound modulatory actions on several cellular processes it is not an overstatement to hypothesize that morphine may represent a key chemical messenger in the process of modulating proliferation of diverse cells. This has been recently demonstrated by the finding of a novel opiate-alkaloid selective receptor subtype in human multilineage progenitor cells (MLPC). Adding to the significance of morphinergic signaling are the findings of its presence in plant, invertebrate and vertebrate cells, which also have been shown to synthesize this messenger as well. Interestingly, we and others have shown that some cancerous tissues contain morphine. Furthermore, in medullary histolytic reticulosis, which is exemplified by cells having hyperactivity, the mu3 (mu3) opiate select receptor was not present. Thus, it would appear that morphinergic signaling has inserted itself in many processes taking a long time to evolve, including those regulating the proliferation of cells across diverse phyla.

Pathogenesis and clinical and economic consequences of postoperative ileus

PURPOSE

The pathogenesis, etiology, clinical manifestations, and clinical and economic consequences of postoperative ileus (POI) in patients undergoing major abdominal surgery; the estimated prevalence of POI; the potential cost savings from efforts to shorten hospital length of stay (LOS); and the role of patient counseling in minimizing the consequences of POI are discussed.

SUMMARY

POI has neurogenic, inflammatory, hormonal, and pharmacologic components. It manifests as abdominal distention, pain, nausea, vomiting, and inability to pass stools or tolerate a solid diet that in half of patients undergoing major abdominal surgery persist for more than four days. Surgical stress and prolonged opioid analgesic use contribute to POI. Delayed surgical wound healing and ambulation, atelectasis, pneumonia, and deep vein thrombosis are among the possible complications of POI that can increase LOS, resource use, and health care costs. POI is common; its prevalence probably is underestimated. The potential cost savings from shortening LOS by one day are substantial. Providing advice about the proper preoperative and postoperative care regimen to patients undergoing major abdominal surgery can minimize the clinical and economic consequences of POI.

CONCLUSION

POI is a common complication of major abdominal surgery that can have a substantial clinical and economic impact.

The pharmacological effects of Daikenchuto, a traditional herbal medicine, on delayed gastrointestinal transit in rat postoperative ileus

The effect of Daikenchuto, a traditional herbal medicine, on gastrointestinal hypoperistalsis in postoperative ileus (POI) was investigated. POI was induced by laparotomy with manipulation of the gastrointestine under anesthesia, and gastrointestinal transit was calculated by migration of Evans blue. Daikenchuto (270 - 2,700 mg/kg, p.o.) dose-dependently improved the delayed gastrointestinal transit in POI. This effect of Daikenchuto was partially inhibited by SB204070 (1 mg/kg, s.c.), a 5-hydroxytriptamine(4) (5-HT(4))-receptor antagonist and completely abolished by atropine (1 mg/kg, s.c.), a muscarine-receptor antagonist. Among the constituents of Daikenchuto, the medical herb zanthoxylum fruit (60 mg/kg, p.o.) and maltose syrup (2,400 mg/kg, p.o.) significantly ameliorated the delayed gastrointestinal transit, but ginseng and processed ginger did not affect the gastrointestinal transit in the rat POI. The improvement induced by zanthoxylum fruit was also inhibited by atropine or SB204070. In addition, the high osmotic pressure of the maltose syrup (2400 mg/10 mL per kg) was related to the improvement of delayed gastrointestinal transit. These results demonstrated that Daikenchuto ameliorates postoperative hypoperistalsis via cholinergic nerves and 5-HT(4) receptors and that osmotic pressure also may be involved in this action. Moreover, zanthoxylum fruit and maltose syrup were crucial medical herbs contributing to the ability of Daikenchuto.

Postoperative effects of opioid analgesics administered via continuous perfusion and patient controlled analgesia after open heart surgery

Critical care nurses and physicians are familiar with the principles of patient controlled analgesia and the opioid analgesics' regimens and observations necessary for pain control in the postoperative cardiac surgical patients. The objective of the study was to compare the effects of morphine, fentanyl, meperidine, remifentanil and tramadol which were administered by patient controlled analgesia and continuous intravenous infusion combination on the various parameters. This study was designed as prospective randomised trial. Fifty patients undergone open heart surgery with sternotomy were entered equally into five randomized groups. Visual analog scale was used by researcher nurse to assess the patient' pain status. Respiratory rate, heart rate and blood gases (pO2, pCO2, SaO2), radial arterial blood pressures were measured in the first 24 hrs postoperatively. Bolus requirements were determined by physicians and side effects of the analgesics were documented. Fentanyl group showed statistically higher levels of mean pO2 (p=0.002). Meperidine had the lowest number of bolus doses (p=0.001). There were no significant differences between the groups for pain management except higher visual analog scales on tramadol. Headache, stomach-ache and, palpitations were observed in our patients. Remifentanil, meperidine, fentanyl and morphine showed similar effect with each other for pain relief except tramadol.

The selective mu opioid receptor antagonist, alvimopan, improves delayed GI transit of postoperative ileus in rats

Postoperative ileus (POI) is often exacerbated by opioid analgesic use during and following surgery, since mu opioid receptor activation results in a further delay of gastrointestinal (GI) transit. The effects of alvimopan, a novel, selective, and peripherally acting mu opioid receptor antagonist, and the reference compound methylnaltrexone, upon POI were investigated in rats. Under isoflurane anesthesia, POI was induced by laparotomy with intestinal manipulation. Immediately after the surgery, the rats received (51)Cr by gavage. Three hours after the surgery, the rats were sacrificed and GI transit was estimated using the geometric center (GC) of (51)Cr. Alvimopan (0.1-3 mg/kg) or methylnaltrexone (100 mg/kg) were administered by gavage either before or after the surgery, with or without morphine administration (1 mg/kg). GI transit was delayed by intestinal manipulation (GC = 2.92 +/- 0.17). Alvimopan (1 and 3 mg/kg) significantly reversed this delayed GI transit when administered 45 min prior to surgery. However, the effects of alvimopan were less pronounced when administered following surgery. Morphine administration further delayed GI transit induced by intestinal manipulation (GC = 1.97 +/- 0.11). Under these conditions, alvimopan (1 and 3 mg/kg) also significantly improved delayed GI transit when administered before surgery. Methylnaltrexone was inactive under all experimental conditions. These data suggest that mu opioid receptors play a role in the pathogenesis of POI, and that the clinical benefit reported to be afforded by alvimopan may be in part mediated via inhibition of an endogenous opioid release as well as blockade of the unwanted GI actions of analgesic agents.

Optimizing perioperative management of patients undergoing colorectal surgery: what is new?

PURPOSE OF REVIEW

This review highlights recent developments in individual perioperative interventions in colorectal surgery, and progress in so-called fast-track or enhanced-recovery programmes.

RECENT FINDINGS

A new survey from five northern European countries has revealed that best clinical practice in perioperative care, based on previously published high-grade evidence, is only partially in use in daily clinical practice. Recently, a number of trials contrasting clinical results in enhanced-recovery protocols versus traditional care clearly show that such protocols indeed enhance recovery, although effects on morbidity are less obvious. Further evidence supporting preoperative oral carbohydrate treatment, avoidance of oral bowel preparation and wound drainage in elective colonic surgery and avoidance of intraoperative fluid excess has emerged. The oral opioid antagonist alvimopan has recently been shown to limit postoperative gastrointestinal paralysis. The role of laparoscopic surgery in the era of enhanced-recovery programmes is unclear.

SUMMARY

There is strong evidence on how to enhance recovery after colorectal surgery, but many interventions are not utilized in daily practice. Further evidence has emerged supporting several perioperative treatments, and successful experiences of enhanced-recovery programmes have now been reported from several centres.

Human white blood cells synthesize morphine: CYP2D6 modulation

Human plasma contains low, but physiologically significant, concentrations of morphine that can increase following trauma or exercise. We now demonstrate that normal, human white blood cells (WBC), specifically polymorphonuclear cells, contain and have the ability to synthesize morphine. We also show that WBC express CYP2D6, an enzyme capable of synthesizing morphine from tyramine, norlaudanosoline, and codeine. Significantly, we also show that morphine can be synthesized by another pathway via l-3,4-dihydroxyphenylalanine (L-DOPA). Finally, we show that WBC release morphine into their environment. These studies provide evidence that 1) the synthesis of morphine by various animal tissues is more widespread than previously thought and now includes human immune cells. 2) Moreover, another pathway for morphine synthesis exists, via L-DOPA, demonstrating an intersection between dopamine and morphine pathways. 3) WBC can release morphine into the environment to regulate themselves and other cells, suggesting involvement in autocrine signaling since these cells express the mu3 opiate receptor subtype.

N-methyl-D-aspartate receptors mediate endogenous opioid release in enteric neurons after abdominal surgery

BACKGROUND & AIMS

We tested the hypothesis that N-methyl-D-aspartate (NMDA) receptors mediate surgery-induced opioid release in enteric neurons.

METHODS

We used mu opioid receptor (muOR) internalization as a measure of opioid release with immunohistochemistry and confocal microscopy. MuOR internalization was quantified in enteric neurons from nondenervated and denervated ileal segments of guinea pig after abdominal laparotomy with and without pretreatment with NMDA-receptor antagonists acting at different recognition sites (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,b] cyclohepten-5,10-imine (MK-801) or (D) 2-amino-5-phosphopenoic acid (AP-5) at .5, 1 mg/kg; 8-chloro-4-hydroxy-1-oxo-1,2-dihydropyridazinol [4,5-]quinoline-5-oxide choline (MRZ 2/576) or 8-chloro-1,4-dioxo-1,2,3,4-tetrahydropyridazinol [4,5-]quinoline choline salt (MRZ 2/596) at .3, 1 mg/kg, or with an antagonist for the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (1, 3 mg/kg). To determine whether NMDA stimulation induces opioid release, (1) ilea were exposed to NMDA (100 micromol/L) and D-serine (10 micromol/L) with or without the antagonist MK-801 or AP-5 (50 micromol/L); and (2) neuromuscular preparations of the ileum were stimulated electrically (20 Hz, 20 min) with or without MK-801 or AP-5 (50 micromol/L).

RESULTS

MuOR endocytosis induced by abdominal laparotomy was inhibited significantly by NMDA-receptor antagonists in nondenervated and denervated ileal segments, but not by the AMPA-receptor antagonist. MuOR endocytosis in neurons exposed to NMDA or electrical stimulation was prevented by NMDA-R antagonists.

CONCLUSIONS

Abdominal laparotomy evokes local release of glutamate that results in endogenous opioid release through the activation of peripheral NMDA receptors. This suggests an interaction between the glutamatergic and opioid systems in response to the noxious and perhaps mechanosensory stimulation of surgery.

Effect of adding ketorolac to intravenous morphine patient-controlled analgesia on bowel function in colorectal surgery patients--a prospective, randomized, double-blind study

BACKGROUND

Postoperative ileus (PI) is the transient impairment of bowel motility due to surgical trauma and the associated physiological responses. Postoperative ileus results in patient discomfort, increases gastrointestinal risks, prolongs hospital stay and increases medical expenses. In this study, we investigated the effect of patient-controlled analgesia (PCA) morphine with or without ketorolac on bowel functions in patients after colorectal surgeries.

METHODS

A total of 79 patients who received elective colorectal resection were randomly allocated into two groups receiving either intravenous PCA morphine (M group) or intravenous PCA morphine plus ketorolac (K group). Recovery of bowel functions (bowel movement, passage of flatus, and soft diet intake), pain scores, morphine consumption, time for first ambulation, and opioid-related side-effects were recorded.

RESULTS

Patients in the K group received 29% less morphine than patients in the M group with comparable pain scores. The first bowel movement (1.5 [0.7-1.9] vs. 1.7 [1.0-2.8] days, P < 0.05) and the first ambulation (2.2 +/- 1.0 vs. 2.8 +/- 1.2 days, P < 0.05) were significantly earlier in the K group than in the M group. The time of the first flatus passing, the first intake of soft diet, and duration of hospital stay were not significantly different between the two groups.

CONCLUSIONS

The results of this study suggest that addition of ketorolac to intravenous morphine PCA provides an opioid-sparing effect but has limited benefit in shortening the duration of bowel immobility and time to first ambulation. These findings imply that postoperative ileus is attributable to multiple factors in addition to morphine consumption.

Morphine modulates inducible nitric oxide synthase expression and reduces pulmonary oedema induced by α-naphthylthiourea

This study was designed to investigate the possible participation of morphine in pulmonary oedema induced by alpha-naphthylthiourea (ANTU), which is a well-known noxious chemical agent in the lung. Injection of ANTU (15 mg/kg i.p.) produced pulmonary oedema as indicated by an increase in lung weight/body weight ratio and pleural effusion reaching a maximum within 4 h in rat. Administration of morphine prior to ANTU significantly inhibited to pulmonary oedema with a dose-dependent manner. The protective effect of morphine is prevented by peripheral opioid receptor antagonist, naloxone methiodide. ANTU-treated rats were shown positive by inducible nitric oxide synthase immunohistochemical staining. There was no staining in the control group. On the other hand, the degree of staining was markedly reduced in tissue sections by morphine. These results suggest that previous administration of subcutaneous morphine has preventive effect on ANTU-induced pulmonary inflammatory reaction and its effect mediated via peripheral opioid receptors. Application of naloxone with ANTU has no effect on the lung parameters indicating that endogenous opioids do not modulate ANTU-induced damage.

Presence of reticuline in rat brain: a pathway for morphine biosynthesis

We demonstrate the presence of reticuline, an isoquinoline alkaloid that was purified and identified in the rat brain. This was achieved by high-performance liquid chromatography coupled with electrochemical detection. This material was finally identified by nano-electrospray ionization quadrupole time-of-flight tandem mass spectrometry. The expression of this tetrahydroisoquinoline alkaloid in rat brain is at 12.7+/-5.4 ng/g wet tissue. Furthermore, rat chow, rat small and large intestine and bacteria cultured from these tissues did not contain either morphine or reticuline, eliminating the possibility of contamination or an exogenous source of these compounds. This finding adds information which suggests that morphine biosynthesis may occur in rat neural tissues, and that its biosynthesis pathway may be similar to that reported in the poppy plant.

Opioid-induced bowel dysfunction: pathophysiology and potential new therapies

Opioid treatment for postoperative or chronic pain is frequently associated with adverse effects, the most common being dose-limiting and debilitating bowel dysfunction. Postoperative ileus, although attributable to surgical procedures, is often exacerbated by opioid use during and following surgery. Postoperative ileus is marked by increased inhibitory neural input, heightened inflammatory responses, decreased propulsive movements and increased fluid absorption in the gastrointestinal tract. The use of opioids for chronic pain is characterised by a constellation of symptoms including hard dry stools, straining, incomplete evacuation, bloating, abdominal distension and increased gastroesophageal reflux. The current management of opioid-induced bowel dysfunction among patients receiving opioid analgesics consists primarily of nonspecific ameliorative measures. Intensive investigations into the mode of action of opioids have characterised three opioid receptor classes -mu, delta and kappa- that mediate the myriad of peripheral and central actions of opioids. Activation of mu-opioid receptors in the gastrointestinal tract is responsible for inhibition of gut motility, whereas receptors in the central nervous system mediate the analgesic actions of opioids. Blocking peripheral opioid receptors in the gut is therefore a logical therapeutic target for managing opioid-induced bowel dysfunction. Available opioid antagonists such as naloxone are of limited use because they are readily absorbed, cross the blood-brain barrier, and act at central opioid receptors to reverse analgesia and elicit opioid withdrawal. Methylnaltrexone and alvimopan are recently developed opioid antagonists with activity that is restricted to peripheral receptors. Both have recently shown the ability to reverse opioid-induced bowel dysfunction without reversing analgesia or precipitating central nervous system withdrawal signs in non-surgical patients receiving opioids for chronic pain. In addition, recent clinical studies with alvimopan suggest that it may normalise bowel function without blocking opioid analgesia in abdominal laparotomy patients with opioid-related postoperative ileus.

Pseudo-obstruction in the critically ill

Intestinal pseudo-obstruction is defined as a clinical syndrome characterized by impairment of intestinal propulsion, which may resemble intestinal obstruction, in the absence of a mechanical cause. It may involve the small and/or the large bowel, and may present in acute, subacute or chronic forms. We have performed a systematic review of acute pseudo-obstruction, also referred to as Ogilvie's syndrome in the literature, and focused on proposed mechanisms, manifestations and management of post-surgery and critically ill patients who suffer from one or more underlying clinical conditions. The hallmark of the syndrome is massive intestinal distension, which is detected on clinical inspection and plain abdominal radiography. The underlying pathophysiological mechanisms are not fully understood. Therefore, treatment focuses on preventing intestinal perforation, which is associated with an average 21% mortality rate.

Pseudo-obstruction in the critically ill

Intestinal pseudo-obstruction is defined as a clinical syndrome characterized by impairment of intestinal propulsion, which may resemble intestinal obstruction, in the absence of a mechanical cause. It may involve the small and/or the large bowel, and may present in acute, subacute or chronic forms. We have performed a systematic review of acute pseudo-obstruction, also referred to as Ogilvie's syndrome in the literature, and focused on proposed mechanisms, manifestations and management of post-surgery and critically ill patients who suffer from one or more underlying clinical conditions. The hallmark of the syndrome is massive intestinal distension, which is detected on clinical inspection and plain abdominal radiography. The underlying pathophysiological mechanisms are not fully understood. Therefore, treatment focuses on preventing intestinal perforation, which is associated with an average 21% mortality rate.

Plasma cytokines do not reflect expression of pro- and anti-inflammatory cytokine mRNA at organ level after cardiopulmonary bypass in neonatal pigs

BACKGROUND

Plasma concentrations of inflammatory markers are increased in response to the trauma of cardiac surgery and cardiopulmonary bypass (CPB). It is, however, unknown whether the plasma cytokine levels and cytokine mRNA expression at organ level reflect each other.

METHODS

Twenty-six piglets (17-19 days) were allocated to the sham-group (sternotomy only, n = 13) or to the CPB-group (sternotomy, 120 min CPB procedure with 60-min aortic cross-clamp, n = 13). The pigs were observed for 0.5 h or 4 h post-CPB. Plasma levels of IL-1beta, IL-6, IL-8 and IL-10 and mRNA expression of TNF-alpha, IL-1beta, IL-6, IL-8, IL-10 and iNOS in organs were registered with concomitant changes in oxygenation index (OI) and expiratory nitric oxide (NO).

RESULTS

In pigs killed 0.5 h post-CPB there was a significant increase in IL-10 mRNA in the lungs and kidneys compared with the sham-group. IL-1beta mRNA was detectable in the kidneys and lungs of the CPB-pigs, while IL-6 mRNA was up regulated only in lungs. In pigs killed 4 h post-CPB a significantly higher IL-6 mRNA was found in heart tissue and a lower IL-10 mRNA was found in lungs of CPB pigs compared with the sham-group. There was a concomitant significant increase in OI and increased plasma IL-8 and IL-10 concentrations in the CPB-pigs compared with the sham-pigs.

CONCLUSION

The cytokine mRNA expression pattern was very different for the pigs killed already 0.5 h after the CPB procedure compared with the pigs killed 4 h post-CPB. The plasma cytokine levels poorly reflected mRNA expression of the pro- and anti-inflammatory cytokines.

Postoperative ileus: progress towards effective management

The pathogenesis of postoperative ileus (PI) is multifactorial, and includes activation of inhibitory reflexes, inflammatory mediators and opioids (endogenous and exogenous). Accordingly, various strategies have been employed to prevent PI. As single-modality treatment, continuous postoperative epidural analgesia including local anaesthetics has been most effective in the prevention of PI. Choice of anaesthetic technique has no major impact on PI. Minimally invasive surgery reduces PI, in accordance with the sustained reduction in the inflammatory responses, while the effects of early institution of oral nutrition on PI per se are minor. Several pharmacological agents have been employed to resolve PI (propranolol, dihydroergotamine, neostigmine, erythromycin, cisapride, metoclopramide, cholecystokinin, ceruletide and vasopressin), most with either limited effect or limited applicability because of adverse effects. The development of new peripheral selective opioid antagonists is promising and has been demonstrated to shorten PI significantly. A multi-modal rehabilitation programme including continuous epidural analgesia with local anaesthetics, enforced nutrition and mobilisation may reduce PI to 1-2 days after colonic surgery.

Manejo clínico de la seudoobstrucción aguda de colon en el enfermo hospitalizado: revisión sistemática de la bibliografía

Intestinal pseudoobstruction is a clinical syndrome characterized by impairment of intestinal propulsion, which may resemble intestinal obstruction, in the absence of a mechanical cause. It usually affects the colon but the small intestine may also be involved, and may present in acute, subacute or chronic forms. We have performed a systematic review of the acute form of pseudoobstruction, also referred to as Ogilvie's syndrome. We discuss proposed pathophysiological mechanisms, manifestations and management of this clinical condition in post-surgery and critically ill patients. The hallmark of the syndrome is massive intestinal distension, which is detected on clinical inspection and plain abdominal radiography. The underlying pathophysiological mechanisms are not fully understood. Therefore, treatment has focussed on preventing intestinal perforation, which is associated with a 21% mortality rate.

FORMATION OF HIGHLY ANALGESIC MORPHINE-6-GLUCURONIDE FOLLOWING PHYSIOLOGIC CONCENTRATION OF MORPHINE IN HUMAN BRAIN

3H-Morphine at physiologic concentration was metabolized in vitro to its 3- and 6-glucuronides by human brain homogenate. Recombinant UGT2B7, one of the UDP-glucuronosyltransferase (UGT) isoforms, is able to glucuronidate the 3- and 6-hydroxy groups of morphine at nanomolar concentrations. These results suggest that endogenous morphine is converted to its 6-glucuronide, a more highly analgesic substance than the parent compound, to suppress effectively pain symptoms in humans.

To ventilate or not after minimally invasive direct coronary artery bypass surgery: the role of epidural anesthesia

OBJECTIVE

To evaluate the effect of immediate postoperative extubation and postoperative ventilation after minimally invasive direct coronary artery bypass (MIDCAB) surgery and to assess the role of epidural anesthesia.

DESIGN

Randomized prospective study.

SETTING

University hospital, single institution.

PARTICIPANTS

Patients (n = 90) scheduled for elective MIDCAB surgery.

INTERVENTIONS

Patients were divided into 3 groups: 30 patients had general anesthesia and were extubated immediately after surgery (extubated group), 30 patients had a thoracic epidural and general anesthesia and were extubated immediately after surgery (epidural group), and 30 patients had general anesthesia and were ventilated after surgery (intubated group).

MEASUREMENTS AND MAIN RESULTS

With a similar cardiac index and less vasoactive medication, mean arterial blood pressure (77 plus minus 8 mmHg [mean plus minus SD]) and heart rate (76 plus minus 10 beats/min) in the epidural group were lower on the first postoperative day than in the intubated group (83 plus minus 10 mmHg and 81 plus minus 13 beats/min) and the extubated group (86 plus minus 10 mmHg and 83 plus minus 13) (p = 0.01 and p = 0.09). Oxygenation on the first postoperative day was better in the epidural group than in the intubated group (14.8 plus minus 3.8 kPa v 12.6 plus minus 3.2 kPa; p = 0.05). The epidural group and the extubated group had a transient respiratory acidosis postoperatively. Pain score in the epidural group was lower on the first postoperative day than in the extubated group with general anesthesia (3.0 plus minus 1.6 visual analog scale v 4.6 plus minus 1.8 visual analog scale; p = 0.01). Hospital stay was shorter in the epidural group than in the ventilated group (5.9 plus minus 2.4 days v 8.1 plus minus 5.3 days; p = 0.05)

CONCLUSION

Immediate postoperative extubation in patients with thoracic epidural anesthesia and supplemental general anesthesia provides the most favorable clinical circumstances after MIDCAB surgery.

Review of postoperative ileus

Postoperative ileus (POI) is an inevitable adverse consequence of surgical procedures. In fact, prolonged POI can lead to patient discomfort, decreased mobility, delayed enteral feeding, and ultimately, prolonged hospitalizations and increased costs. It is believed that POI occurs as a result of inhibitory neural reflexes and inflammatory processes. The use of postoperative opioids also appears to contribute to ileus. Recently, the potential influence of endogenous opioids, in addition to exogenous opioids, on the pathogenesis of ileus has come to light and spurred investigations into new treatment strategies. Over the years, several treatment modalities have become accepted management options for POI; chief among these are nasogastric suction and prokinetic agents. However, data demonstrating that these agents reduce the duration of POI are limited. Of current treatment modalities, use of epidural local anesthetics appears to be the most effective means of reducing POI. Other potentially effective treatments include early enteral feeding and less invasive surgical procedures. Together, these techniques have reduced the length of stay after colonic surgery to 2 to 3 days. Future studies, including those incorporating investigational agents, such as kappa-opioid agonists and peripheral mu-opioid antagonists, into a multimodal regimen, may offer new treatment options to further impact POI duration.

Alvimopan* (ADL 8-2698) is a novel peripheral opioid antagonist

Alvimopan (ADL 8-2698; Adolor Corporation, Exton, PA, USA) is a novel, peripherally restricted opioid antagonist. After oral administration, it has activity specific to the gastrointestinal (GI) tract. ADL 8-2698 has low systemic absorption and a high affinity for mu-opioid receptors. In healthy subjects, ADL 8-2698 antagonized loperamide-induced changes in GI transit and prevented morphine-induced delays in oral-cecal transit time without antagonizing centrally mediated opioid effects, such as analgesia or pupillary constriction. In the treatment of opioid naive patients who underwent surgery and received opioids for acute pain, oral ADL 8-2698 (6.0 mg) improved the management of postoperative ileus (POI) by shortening the time to achieve normal bowel function and, ultimately, hospital stay. Postoperative nausea and vomiting and the overall incidence of all GI side effects were reduced in patients treated with ADL 8-2698 for POI. Analgesia was not compromised, because there were no changes in median opioid consumption or Visual Analog Scale (VAS) pain scores in patients treated with ADL 8-2698 versus patients treated with placebo. No drug-related side effects were observed in acute pain postsurgical patients in the initial POI study. In patients treated with opioids for chronic pain or opioid addiction, lower doses of oral ADL 8-2698 (0.5 to 3.0 mg) reversed opioid bowel dysfunction (OBD) and normalized GI activity. These effects were evident without compromising opioid analgesia or inducing central nervous system symptoms of withdrawal. Some chronic opioid patients receiving apparently supramaximal doses of ADL 8-2698 (> or = 3.0 mg) reported localized GI side effects, possibly indicative of a localized GI withdrawal response. The most common side effects of ADL 8-2698 in chronic pain patients with OBD were abdominal pain, flatulence, and diarrhea. These effects were not observed in most OBD patients receiving lower doses of ADL 8-2698. Overall, ADL 8-2698 was well tolerated in clinical trials. Further studies to evaluate the efficacy and safety of ADL 8-2698 in clinical practice are in progress.

Human vascular and cardiac endothelia express mu opiate receptor transcripts

Pharmacologic and immunologic evidence suggests that nitric oxide-coupled mu-subtype opiate receptors are expressed in human vascular endothelium. In this study, we present molecular evidence of mu opiate receptor expression. Using primers derived from the human neuronal mu1 opiate receptor, we used RT-PCR to detect expression of mu transcripts from human endothelia. Sequence analysis of the RT-PCR products revealed 100% identity with the neuronal human mu1 receptor. We further show that pretreatment of human internal thoracic artery and cardiac atrial endothelium with the proinflammatory cytokines interleukin-1-alpha and -beta led to a significant increase in both the expression of the mu transcript and in morphine-stimulated nitric oxide release measured amperometrically. Taken together, these studies provide molecular evidence that mu-type opiate receptors are expressed in human vascular endothelia and that their expression can be upregulated by proinflammatory cytokines.

The presence of morphine in ganglionic tissues of Modiolus deminissus: a highly sensitive method of quantitation for morphine and its derivatives

Morphine and morphine-6-glucuronide, a morphine metabolite, have been identified and quantified in Modiolus deminissus pedal ganglia at a level of 2.41 and 0.95 ng/ganglia, respectively. These opiate alkaloids are normally found at low concentrations in invertebrate and vertebrate tissues, including neural. Given this problem, we also describe a new opiate extraction protocol as well as a high-performance liquid chromatography purification procedure that can separate and quantify morphine and its derivatives at sub-nanogram concentrations. Furthermore, both morphine and morphine-6-glucuronide were identified in this mollusk's pedal ganglia by mass spectrometry analysis.

Endogenous morphine is produced in response to cardiopulmonary bypass in neonatal pigs

BACKGROUND

Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response. Endogenous morphine production has previously been demonstrated in humans after cardiac surgery with CPB. It has been hypothesized that morphine plays a role as an anti-inflammatory mediator in the systemic inflammatory response. The aim of this study was to investigate if the CPB procedure in itself elicits an endogenous morphine production in neonatal pigs.

METHODS

Endogenous morphine production was measured in arterial blood in piglets exposed to sternotomy alone (sham group, n=10) or sternotomy and CPB (n=10). Blood samples were obtained immediately after the induction of anaesthesia, at the end of CPB and 4 h later. Morphine in arterial blood was detected by radioimmunoassay and confirmed by gas chromatography mass spectrometry.

RESULTS

Animals undergoing CPB showed detectable endogenous morphine concentrations immediately after CPB, with increased concentrations postoperatively. There was no measurable morphine production in the sham operated pigs.

CONCLUSION

The CPB procedures elicits an endogenous morphine production in neonatal pigs. This morphine response is analogous to the previously demonstrated response in patients subjected to cardiac surgery and CPB.

Lipopolysaccharide increases endogenous morphine levels in rat brain

The present study was designed to determine whether whole body injection of lipopolysaccharide increases endogenous rat brain morphine levels. High performance liquid chromatography coupled to electrochemical detection and gas-chromatography mass spectrometry reveal that the resting brain morphine level is 7.0+/-3.2ng/g wet weight. In a time dependent manner, intraperitoneal injection of lipopolysaccharide (10 microg), leads to an increase of brain morphine level with a peak reaching after 36h post injection. After 72h following the lipopolysaccharide-injection, morphine levels increased to 66.0+/-5.4ng/g brain wet weight (P<0.001). Furthermore, 96h of fasting also increased the brain morphine level to 44.0+/-3. 6ng/g of brain wet weight. These results suggest that rat brain morphinergic processes respond to organismic challenges after a significant latent period.