Inhibition of sympathetic pathways restores postoperative ileus in the upper and lower gastrointestinal tract

Transcutaneous Auricular Vagal Nerve Stimulation in Healthy Non-Sedated Horses: A Feasibility Study

This study aimed to evaluate the feasibility of transcutaneous auricular vagal nerve stimulation (tAVNS) in healthy horses and its effect on heart rate variability (HRV). The study comprised three phases: the selection of mares, their acclimatization to the tAVNS, and the stimulation phase. Stimulation was performed with two electrodes positioned on the right pinna. The settings were 0.5 mA, 250 μs, and 25 Hz for pulse amplitude, pulse width, and pulse frequency, respectively. HRV was analysed before (B1), during (T), and after (B2) the tAVNS. From the 44 mares initially included, only 7 completed the three phases. In these mares, the heart rate (HR) was significantly lower, and frequency domain parameters showed an increased parasympathetic tone in B2 compared with B1. However, in 3/7 mares, the HR was significantly higher during T compared with B1 and B2, compatible with a decreased parasympathetic tone, while in 4/7 mares, the HR was significantly lower and the parasympathetic nervous system index was significantly higher during T and B2 compared with B1. The tAVNS is an economical and easy procedure to perform and has the potential to stimulate vagal activity; however, it was poorly tolerated in the mares included in this study.

CT-Guided Celiac Ganglion Block for Neurogenic Gastrointestinal Dysmotility

PURPOSE

To determine whether celiac ganglion block can serve as a diagnostic test for dysautonomia as the cause of gastrointestinal dysmotility-related symptoms.

MATERIALS AND METHODS

This was an institutional review board-approved, prospective, single-arm, registered study, from January 2020 to May 2021, and included patients aged 14-85 years with gastrointestinal symptoms of food intolerance, abdominal pain, or angina. Patients with nonneurogenic causes (ie, chronic cholecystitis, peptic ulcer disease, gastroesophageal reflux, and malabsorption syndrome) were excluded. All 15 patients underwent computed tomography-guided celiac ganglion block with 100 mg of liposomal bupivacaine. Patients filled out the dysautonomia-validated questionnaire Composite Autonomic Symptom Score 31 (COMPASS-31) before and after intervention. Differences (before vs after) were compared with the exact permutation method.

RESULTS

Fifteen women (median age, 17 years; range, 14-41 years) were included. Average COMPASS-31 score improved significantly, from baseline 11 (SD ± 2.8) to 4 (SD ± 1.9) (improvement, 7 points ± 2.8; P < .001). All patients reported significant reduction in abdominal angina. Fourteen of the 15 patients (93%) reported complete resolution, and 14 of 15 (93%) reported a significant reduction in non-postprandial abdominal pain (P < .01). Only 1 patient reported no improvement. Eight of those 14 patients (57%) reported complete resolution of abdominal pain. There was a significant improvement in functional scores (vomiting, P = .01; constipation frequency, P = .02; constipation severity, P < .01; and nausea, P < .01). The rate of minor and major adverse events was 13% and 0%, respectively, per the Society of Interventional Radiology adverse event classification.

CONCLUSIONS

Celiac ganglion block is a safe diagnostic tool for confirming dysautonomia as the underlying condition in patients with gastrointestinal dysmotility-related symptoms. It could provide early diagnosis, lead to definitive treatment (ganglionectomy) earlier, or obviate unnecessary surgery.

Postoperative Ileus: Comparative Pathophysiology and Future Therapies

Postoperative ileus (POI), a decrease in gastrointestinal motility after surgery, is an important problem facing human and veterinary patients. 37.5% of horses that develop POI following small intestinal (SI) resection will not survive to discharge. The two major components of POI pathophysiology are a neurogenic phase which is then propagated by an inflammatory phase. Perioperative care has been implicated, namely the use of opioid therapy, inappropriate fluid therapy and electrolyte imbalances. Current therapy for POI variably includes an early return to feeding to induce physiological motility, reducing the inflammatory response with agents such as non-steroidal anti-inflammatory drugs (NSAIDs), and use of prokinetic therapy such as lidocaine. However, optimal management of POI remains controversial. Further understanding of the roles of the gastrointestinal microbiota, intestinal barrier function, the post-surgical inflammatory response, as well as enteric glial cells, a component of the enteric nervous system, in modulating postoperative gastrointestinal motility and the pathogenesis of POI may provide future targets for prevention and/or therapy of POI.

Sympathetic Denervation Alters the Inflammatory Response of Resident Muscularis Macrophages upon Surgical Trauma and Ameliorates Postoperative Ileus in Mice

Interactions between the peripheral nervous system and resident macrophages (MMs) modulate intestinal homeostatic functions. Activation of β2-adrenergic receptors on MMs has been shown to reduce bacterial challenges. These MMs are also crucial for the development of bowel inflammation in postoperative ileus (POI), an iatrogenic, noninfectious inflammation-based motility disorder. However, the role of the sympathetic nervous system (SNS) in the immune modulation of these MMs during POI or other noninfectious diseases is largely unknown. By employing 6-OHDA-induced denervation, we investigated the changes in the muscularis externa by RNA-seq, quantitative PCR, and flow cytometry. Further, we performed transcriptional phenotyping of sorted CX3CR1⁺ MMs and ex vivo LPS/M-CSF stimulation on these MMs. By combining denervation with a mouse POI model, we explored distinct changes on CX3CR1⁺ MMs as well as in the muscularis externa and their functional outcome during POI. Our results identify SNS as an important mediator in noninfectious postoperative inflammation. Upon denervation, MMs anti-inflammatory genes were reduced, and the muscularis externa profile is shaped toward a proinflammatory status. Further, denervation reduced MMs anti-inflammatory genes also in the early phase of POI. Finally, reduced leukocyte infiltration into the muscularis led to a quicker recovery of bowel motility in the late phase of POI.

Postoperative ileus-An ongoing conundrum

BACKGROUND

Postoperative ileus is common and is a major clinical problem. It has been widely studied in patients and in experimental models in laboratory animals. A wide variety of treatments have been tested to prevent or modify the course of this disorder.

PURPOSE

This review draws together information on animal studies of ileus with studies on human patients. It summarizes some of the conceptual advances made in understanding the mechanisms that underlie paralytic ileus. The treatments that have been tested in human subjects (both pharmacological and non-pharmacological) and their efficacy are summarized and graded consistent with current clinical guidelines. The review is not intended to provide a comprehensive overview of ileus, but rather a general understanding of the major clinical problems associated with it, how animal models have been useful to elucidate key mechanisms and, finally, some perspectives from both scientists and clinicians as to how we may move forward with this debilitating yet common condition.

Neuro-innate immune interactions in gut mucosal immunity

The gastrointestinal (GI) tract performs a set of vital physiological functions related to food and water consumption. To help regulate these complex physiological processes, the GI tract is innervated by extensive neural networks. The GI tract also serves as the largest immune organ aimed to protect hosts from harmful microbes and toxins ingested with food. It emerges that the enteric nervous and immune systems are highly integrated to optimize digestion while reinforcing immune protection. In this review, we will discuss key cellular players involved in the neuro-immune interactions within the GI mucosa with the focus on the recently uncovered neural pathways that regulate mucosal immunity in a context relevant to GI health and disease.

Using a radiopaque marker with radiography for evaluating colonic transit by geometric center in conscious rats: A novel method

This study developed a new method using radiopaque markers under X-ray to measure rat colonic transit by geometric center repeatedly and/or over a time series in the same individually. Additionally, the utility of this method was shown by elucidating the innervation of the autonomic nerve on colonic transit in detail with a pharmacological technique in conscious rats. An in-dwelling silastic cannula was inserted into the cecum and the proximal part was moved through the abdominal wall, where it was fixed to the posterior neck skin. Twenty markers were administered from the cannula to the proximal colon with saline on the fifth day after surgery. The markers were observed with soft X-ray before required repeated short anesthesia. Experimentation 1: Rats were measured colonic transit twice over 2 days with no administration. Experimentation 2: Rats were administered saline on the first day and pharmacology on the second day intraperitoneally before measurement. Experimentation 1: The markers administrated from the cannula and transited from proximal colon to distal colon over a time series. It showed no significant difference in complication rates between 2 days. Experimentation 2: The colonic transit was increasingly accelerated by neostigmine and phentolamine but not propranolol. Significant changes in 1.0 mg/kg atropine were noted although no differences were found between control and 0.05 mg/kg atropine and between each other's. We have presented the method using radiopaque markers under X-ray with short anesthesia for evaluating the colonic transit. The methods could show rat colonic transit changes in detail with a pharmacological technique.

Ameliorating effects of sacral neuromodulation on gastric and small intestinal dysmotility mediated via a sacral afferent-vagal efferent pathway

BACKGROUND/AIMS

In a recent study of sacral nerve stimulation (SNS) for colonic inflammation, a possible spinal-vagal pathway was implicated. The aim of this study was to provide evidence for such a pathway by investigating the effects of SNS on dysmotility of the stomach and duodenum that are not directly innervated by the sacral efferents.

METHODS

Twenty-seven rats were chronically implanted with wire electrodes for SNS and gastrointestinal slow waves. SNS was performed in several acute sessions to investigate its effects on gastric/duodenal slow waves and emptying/transit impaired by glucagon and rectal distention (RD).

RESULTS

(a) SNS increased the percentage of normal gastric slow waves impaired by glucagon (from 53.9% to 77.0%, P < .0001) and RD (from 64% to 78%, P = .037). This improvement was abolished by atropine. (b) Similar effects were observed with SNS on duodenal slow waves, which was also blocked by atropine. (c) SNS normalized delayed gastric emptying induced by glucagon (control: 61.3%, glucagon: 44.3%, glucagon + SNS: 65.8%) and RD (control: 61.3%, RD: 46.7%, RD + SNS: 64.3%). It also normalized small intestinal transit delayed by RD (P = .001, RD + SNS vs RD; P = .9, RD + SNS vs control). (4) Both glucagon and RD induced an increase in the sympathovagal ratio (P = .007, glucagon vs baseline; P < .001, RD vs baseline) and SNS decreased the ratio (P = .006, glucagon + SNS vs glucagon; P = .04, RD + SNS vs RD).

CONCLUSIONS

Neuromodulation of the sacral nerve improves gastric and small intestinal pacemaking activity and transit impaired by glucagon and RD by normalizing the sympathovagal balance via a retrograde neural pathway from the sacral nerve to vagal efferents.

Is There Still a Place for Lidocaine in the (Postoperative) Management of Colics?

Intravenous lidocaine is widely used to prevent or treat postoperative ileus in horses. Clinical studies that support this approach are flawed and contradicted by others. Also, physical obstruction could be more important in causing postoperative reflux than postoperative ileus in the horse. The antiinflammatory properties of lidocaine and the role of inflammation from intestinal handling in the genesis of postoperative reflux are questionable. Because of cost and questionable efficacy of lidocaine, a well-designed clinical trial is required to support its continued use. However, lidocaine could be given to provide or enhance analgesia in selected cases with postoperative colic.

Mechanism of Electroacupuncture on Postoperative Ileus Induced by Surgical Stress in Rats

Objectives: Acupuncture has been used for treating gastrointestinal (GI) disorders such as postoperative nausea and vomiting. Electroacupuncture (EA) accelerates GI transit following surgery and ameliorates postoperative ileus (POI) to restore colonic transit (CT); however, the mechanisms of this EA-induced restoration remain unclear. The aims of this study were to show CT following surgery and the effects of EA at ST 36 on POI induced by surgical stress (SS) in 45 conscious, male Sprague-Dawley rats. Materials and Methods: An operation was performed in each rat, setting a cannula into the cecum to connect the proximal colon to inject markers. On the day after surgery, 20 metal radiopaque markers were administered to the proximal colon of each rat. These markers were visible throughout the GI tract on soft X-ray immediately after administration and up to 240 minutes afterward. The rats were divided into 5 groups with 9 rats in each group: (1) SS; (2) 5 days post surgery (POST-5D); (3) SS + phentolamine; (4) EA alone; and (5) EA + atropine. The EA was performed at ST 36 for 20 minutes at a frequency of 10 Hz and agents were administered in the appropriate groups before markers were administered and measurements were taken. Measurements were performed the day after surgery except in the POST 5-D group. CT was calculated by the geometric center on the images showing the CT for each rat. Results: CT after surgery was delayed significantly and phentolamine accelerated CT. EA restored CT following surgery and atropine abolished the effect of EA on CT. Conclusions: The current study demonstrated that surgery induced a delay in CT through the sympathetic pathway via α-adrenoreceptors; CT was restored by EA. These results suggest that EA can be used to treat POI through mediation of the autonomic nervous system.

Bioelectric neuromodulation for gastrointestinal disorders: effectiveness and mechanisms

The gastrointestinal tract has extensive, surgically accessible nerve connections with the central nervous system. This provides the opportunity to exploit rapidly advancing methods of nerve stimulation to treat gastrointestinal disorders. Bioelectric neuromodulation technology has considerably advanced in the past decade, but sacral nerve stimulation for faecal incontinence currently remains the only neuromodulation protocol in general use for a gastrointestinal disorder. Treatment of other conditions, such as IBD, obesity, nausea and gastroparesis, has had variable success. That nerves modulate inflammation in the intestine is well established, but the anti-inflammatory effects of vagal nerve stimulation have only recently been discovered, and positive effects of this approach were seen in only some patients with Crohn's disease in a single trial. Pulses of high-frequency current applied to the vagus nerve have been used to block signalling from the stomach to the brain to reduce appetite with variable outcomes. Bioelectric neuromodulation has also been investigated for postoperative ileus, gastroparesis symptoms and constipation in animal models and some clinical trials. The clinical success of this bioelectric neuromodulation therapy might be enhanced through better knowledge of the targeted nerve pathways and their physiological and pathophysiological roles, optimizing stimulation protocols and determining which patients benefit most from this therapy.

Needleless Transcutaneous Electrical Acustimulation: A Pilot Study Evaluating Improvement in Post-Operative Recovery

BACKGROUND

Functional gastrointestinal disturbance occurs after abdominal surgeries and could last for an extended period of time in some cases. This study was designed (1) to evaluate the effects of needleless transcutaneous electrical acustimulation (TEA) on postoperative recovery, and (2) to investigate the mechanisms involving autonomic function in postoperative patients after removal of gastrointestinal cancers.

METHODS

Forty-two patients (33 male, age: 69.5 ± 1.5 years) scheduled for abdominal surgical removal of gastrointestinal cancers were randomized to TEA (n = 21) and sham-TEA (n = 21). TEA was performed via acupoints ST36 and PC6 1 h twice daily from the postoperative day (POD) 1 to day 3. Sham-TEA was performed at non-acupoints.

RESULTS

(1) TEA improved major postoperative symptoms by about 30%, including a reduction in time to defecation by 31.7% (P < 0.01 vs. sham-TEA), time to first flatus by 35.9% (P < 0.001), time to ambulation by 42.8% (P < 0.01), time to resuming diet by 26.5% (P < 0.01) and hospital stay by 30% (P < 0.05) as well as pain score by 50% (P < 0.01). (2) TEA significantly increased vagal activity (P < 0.001) and decreased sympathetic activity on POD 4 (P < 0.001) compared with POD 1 as well as the serum level of NE (P < 0.05). (3) The vagal activity, high frequency assessed from the spectral analysis of heart rate variability, was negatively correlated with time to resuming diet, whereas the sympathetic measurement, serum norepinephrine was positively correlated with time to resuming diet and time to flatus. (4) TEA but not sham-TEA decreased TNF-α by 17.4% from POD 1 to POD 4. (5) TEA was an independent predictor of a shorter hospital stay.

CONCLUSIONS

Needleless TEA improves major postoperative symptoms by enhancing vagal and suppressing sympathetic activities.

Cellular Organization of Neuroimmune Interactions in the Gastrointestinal Tract

The gastrointestinal (GI) tract is the largest immune organ; in vertebrates, it is the only organ whose function is controlled by its own intrinsic enteric nervous system (ENS), but it is additionally regulated by extrinsic (sympathetic and parasympathetic) innervation. The GI nervous and immune systems are highly integrated in their common goal, which is to unite digestive functions with protection from ingested environmental threats. This review discusses the physiological relevance of enteric neuroimmune integration by summarizing the current knowledge of evolutionary and developmental pathways, cellular organization, and molecular mechanisms of neuroimmune interactions in health and disease.

Gut Motility Issues in Critical Illness

Acute gastrointestinal injury (AGI) is common in critical illness and negatively affects outcome. A variety of definitions have been used to describe AGI, which has led to clinical confusion and hampered comparison of research studies across institutions. An international working group of the European Society of Intensive Care Medicine was convened to standardize definitions for AGI and provide current evidence-based understanding of its pathophysiology and management. This disorder is associated with a wide variety of signs and symptoms and may be difficult to detect, therefore a high index of suspicion is warranted.

Postoperative ileus: mechanisms and future directions for research

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

Changes in beta-adrenergic neurotransmission during postoperative ileus in rat circular jejunal muscle

BACKGROUND

To explore postoperative changes in β-adrenergic neurotransmission that participate in pathophysiology of postoperative ileus.

METHODS

Contractile activity of circular jejunal muscle strips was studied. Groups (n = 6/group) were: naïve controls, sham controls 1 and 7 days after laparotomy, and rats 12 h, 1, 3, and 7 days after laparotomy with standardized small bowel manipulation (postoperative ileus). Dose-responses to the β-agonist isoprenaline (3 × 10(-10) - 10(-7) mol L(-1)) were studied in presence/absence of tetrodotoxin (global neural blockade; 10(-6) mol L(-1) ), N6-(1-iminoethyl)-l-lysine (inhibition of inducible nitric oxide synthesis; 10(-4) mol L(-1)), nimesulide (cyclooxygenase-2 inhibition; 10(-5) mol L(-1)), or propranolol (β-blockade; 5 × 10(-6) mol L(-1)). Histochemistry for inflammatory cells and intestinal transit were studied.

KEY RESULTS

Intramural inflammation and delayed transit (postoperative ileus) occurred only in ileus groups. The inhibitory potential of isoprenaline decreased in all postoperative groups including sham (P < 0.05). Tetrodotoxin enhanced isoprenaline-induced inhibition in ileus and sham groups (P < 0.05). N6-(1-iminoethyl)-l-lysine and nimesulide decreased isoprenaline-induced inhibition in ileus groups 12 h, 1, and 7 days, and in sham controls 7 days postoperatively (P < 0.05). Propranolol prevented isoprenaline effects in all groups (P < 0.05).

CONCLUSIONS & INFERENCES

Inhibitory effects of isoprenaline on contractile activity were decreased for 7 days postoperatively. Changes in β-adrenergic neurotransmission do not induce postoperative ileus and appear to be caused by anesthesia and laparotomy rather than bowel manipulation.

Treating a patient with intractable paralytic ileus using thoracic epidural analgesia

Postoperative ileus is considered an undesirable response to major abdominal surgery that leads to discomfort, complications, morbidity, and the prolongation of hospital stays. Although thoracic epidural analgesia has been introduced to prevent and/or reduce postoperative ileus, it is rarely used as a way to treat postoperative ileus. A 65-year-old man developed paralytic ileus after undergoing a colectomy. Despite conservative and surgical management, postoperative morbidity persisted. A continuous infusion of 0.2% levobupivacaine at a rate of 4 mL/hour was administered for 4 days via a thoracic epidural catheter that had been percutaneously tunneled into the T11-T12 epidural space. With this treatment, daily drainage from a nasogastric tube was gradually decreased and flatus was noted. A week later, the patient could start receiving a liquid diet. Therefore, thoracic epidural analgesia can be used to treat or alleviate paralytic ileus.

Can the intestinal dysmotility of critical illness be differentiated from postoperative ileus?

Gastrointestinal dysmotility is commonly noted in the intensive care unit and postoperative settings. Characterized by delayed passage of stool and flatus, nausea, vomiting, and abdominal distention, the condition is associated with nutritional deficiencies, risk of aspiration, and considerable allocation of health care resources. Knowledge of gastrointestinal function in health and illness continues to expand. While the factors that precipitate ileus differ between postoperative and critically ill patients, the two clinical scenarios seem to have similar mechanisms and share many of the same pathophysiologic patterns. By reviewing and comparing the literature on the respective mechanisms and contributing factors generated in these separate clinical settings, a common more comprehensive management strategy may be derived with the potential for newer innovative therapeutic options.

Recovery of colonic transit following extrinsic nerve damage in rats

INTRODUCTION

Injury to pelvic sympathetic and parasympathetic nerves from surgical and obstetrical trauma has long been cited as a cause for abnormal colorectal motility in humans. Using a rat model, acute transaction of these extrinsic nerves has been shown to effect colorectal motility. The aim of this study is to determine in a rat model how transection of these extrinsic nerves affects colonic transit over time.

METHODS

Eighty-two Sprague-Dawley rats underwent placement of a tunneled catheter into the proximal colon. Bilateral hypogastric, pelvic nerves (HGN and PN) or both were transected in 66 rats. The remaining 16 rats received a sham operation. Colonic transit was evaluated at postoperative days (PODs) 1, 3, and 7 by injecting and calculating the geometric center (GC) of the distribution of (51)Cr after 3 h of propagation.

RESULTS

At POD 1, transection of PNs significantly delayed colonic transit (GC = 4.9, p < 0.05), while transection of HGNs (GC = 8.5, p < 0.05) or transection of both nerves (GC = 7.8, p < 0.05) significantly accelerated colonic transit, when compared with sham operation (GC = 6.0). A significant trend toward recovery was noted in both the HGN and PN transection groups at POD 7.

CONCLUSIONS

Damage to the extrinsic sympathetic and/or parasympathetic PNs affects colonic transit acutely. These changes in large bowel motor function normalize over time implicating a compensatory mechanism within the bowel itself.

Effect of preservation of the right gastro-epiploic artery on delayed gastric emptying after cytoreductive surgery and HIPEC: a randomized clinical trial

BACKGROUND

Delayed gastric emptying (DGE) is a main complication with unknown origin after a cytoreductive surgery and hyperthermic intra-peritoneal chemotherapy (CRS-HIPEC). The aim of this study was to investigate if preservation of the right gastro-epiploic artery (GEA) during standard omentectomy would have a positive effect on gastric emptying after CRS-HIPEC.

METHODS

Forty-two patients subjected to a CRS-HIPEC were randomized into two groups perioperatively before performing an omentectomy: in Group I (N = 21) omentectomy was performed with preservation of the GEA; in Group II (N = 21) omentectomy was performed with resection of the GEA. The primary endpoint was the number of days to full oral intake of solid food. Secondary endpoints were number of days to intended occlusion of gastrostomy catheter and total hospital admission time.

RESULTS

No significant differences were discovered between both groups in any of the study endpoints after CRS-HIPEC. No significant differences were observed in patient or operation characteristics between the randomized groups.

CONCLUSIONS

No association was demonstrated between preservation of the gastro-epiploic artery during omentectomy and gastric emptying after CRS-HIPEC. The extensive intestinal manipulation or the heated intra-peritoneal chemotherapy during surgery are more plausible causes of this phenomenon. This clinical trial was registered in the Netherlands at the Central Committee on Research involving Human Subjects (CCMO) under registration number P06.0301L.

Systematic review and meta-analysis of chewing-gum therapy in the reduction of postoperative paralytic ileus following gastrointestinal surgery

BACKGROUND

Postoperative ileus has long been considered an inevitable consequence of gastrointestinal surgery. It prolongs hospital stay, increases morbidity, and adds to treatment costs. Chewing is a form of sham feeding reported to stimulate bowel motility. This analysis examines the value of chewing-gum therapy in treatment of postoperative ileus.

METHODS

A search for randomized, controlled trials studying elective gastrointestinal surgery was undertaken using MEDLINE, Embase, Cochrane Controlled Trials Register, and reference lists. Outcomes were extracted including time to first flatus and bowel motion, length of stay, and complications. Statistical analysis was undertaken using the weighted mean difference (WMD) and random-effects model with 95% confidence intervals (CI).

RESULTS

Seven studies with 272 patients were included. For time to first flatus the analysis favored treatment with a WMD of 12.6 h (17%) reduction (95% CI -21.49 to -3.72; P = 0.005). For time to first bowel motion, treatment was favored with a WMD of 23.11 h (22%) reduction (95% CI -34.32 to -11.91; P < 0.001). For length of stay, the analysis showed a nonsignificant trend toward treatment with WMD of 23.88 h (12%) reduction (95% CI -53.29 to +5.53; P = 0.11). There were no significant differences in complication rates.

CONCLUSIONS

Chewing-gum therapy following open gastrointestinal surgery is beneficial in reducing the period of postoperative ileus, although without a significant reduction in length of hospital stay. These outcomes are not significant for laparoscopic gastrointestinal surgery.

Peritoneal damage: the inflammatory response and clinical implications of the neuro-immuno-humoral axis

BACKGROUND

The peritoneum is a bilayer serous membrane that lines the abdominal cavity. We present a review of peritoneal structure and physiology, with a focus on the peritoneal inflammatory response to surgical injury and its clinical implications.

METHODS

We conducted a nonsystematic clinical review. A search of the Ovid MEDLINE database from 1950 through January 2009 was performed using the following search terms: peritoneum, adhesions, cytokine, inflammation, and surgery.

RESULTS

The peritoneum is a metabolically active organ, responding to insult through a complex array of immunologic and inflammatory cascades. This response increases with the duration and extent of injury and is central to the concept of surgical stress, manifesting via a combination of systemic effects, and local neural pathways via the neuro-immuno-humoral axis. There may be a decreased systemic inflammatory response after minimally invasive surgery; however, it is unclear whether this is due to a reduced local peritoneal reaction.

CONCLUSIONS

Interventions that dampen the peritoneal response and/or block the neuro-immuno-humoral pathway should be further investigated as possible avenues of enhancing recovery after surgery, and reducing postoperative complications.

The role of 5-HT3 and 5-HT4 receptors in the adaptive mechanism of colonic transit following the parasympathetic denervation in rats

BACKGROUND

Clinical studies show that disturbed colonic motility induced by extrinsic nerves damage is restored over time. We studied whether 5-HT3 and 5HT4 receptors are involved in mediating the adaptive mechanisms following parasympathetic denervation.

METHODS

Parasympathetic denervation of the entire colon was achieved by bilateral pelvic nerve transection and truncal vagotomy in rats. Colonic transit was measured by calculating the geometric center (GC) of 51Cr distribution. Expression of 5-HT3 and 5HT4 receptor mRNA was determined by real time RT-PCR.

RESULTS

Parasympathetic denervation caused a significant delay in colonic transit (GC=4.36) at postoperative day (POD) 1, compared with sham operation (GC=6.31). Delayed transit was gradually restored by POD 7 (GC=5.99) after the denervation. Restored colonic transit was antagonized by the administration of 5-HT3 and 5HT4 receptors antagonists at POD 7. 5-HT3 and 5HT4 receptors mRNA expression were significantly increased in the mucosal/submucosal layer at POD 3 or POD 7, whereas no significant difference was observed in the longitudinal muscle layers adherent with the myenteric plexus (LMMP).

CONCLUSIONS

It is suggested that up-regulation of 5-HT3 and 5-HT4 receptors expression in the mucosal/submucosal layer is involved to restore the delayed transit after the parasympathetic denervation in rats.

The role of 5-HT3 and 5-HT4 receptors in the adaptive mechanism of colonic transit following the parasympathetic denervation in rats

BACKGROUND

Clinical studies show that disturbed colonic motility induced by extrinsic nerves damage is restored over time. We studied whether 5-HT3 and 5HT4 receptors are involved in mediating the adaptive mechanisms following parasympathetic denervation.

METHODS

Parasympathetic denervation of the entire colon was achieved by bilateral pelvic nerve transection and truncal vagotomy in rats. Colonic transit was measured by calculating the geometric center (GC) of 51Cr distribution. Expression of 5-HT3 and 5HT4 receptor mRNA was determined by real time RT-PCR.

RESULTS

Parasympathetic denervation caused a significant delay in colonic transit (GC=4.36) at postoperative day (POD) 1, compared with sham operation (GC=6.31). Delayed transit was gradually restored by POD 7 (GC=5.99) after the denervation. Restored colonic transit was antagonized by the administration of 5-HT3 and 5HT4 receptors antagonists at POD 7. 5-HT3 and 5HT4 receptors mRNA expression were significantly increased in the mucosal/submucosal layer at POD 3 or POD 7, whereas no significant difference was observed in the longitudinal muscle layers adherent with the myenteric plexus (LMMP).

CONCLUSIONS

It is suggested that up-regulation of 5-HT3 and 5-HT4 receptors expression in the mucosal/submucosal layer is involved to restore the delayed transit after the parasympathetic denervation in rats.

Abdominal surgery activates nesfatin-1 immunoreactive brain nuclei in rats

Abdominal surgery-induced postoperative gastric ileus is well established to induce Fos expression in specific brain nuclei in rats within 2-h after surgery. However, the phenotype of activated neurons has not been thoroughly characterized. Nesfatin-1 was recently discovered in the rat hypothalamus as a new anorexigenic peptide that also inhibits gastric emptying and is widely distributed in rat brain autonomic nuclei suggesting an involvement in stress responses. Therefore, we investigated whether abdominal surgery activates nesfatin-1-immunoreactive (ir) neurons in the rat brain. Two hours after abdominal surgery with cecal palpation under short isoflurane anesthesia or anesthesia alone, rats were transcardially perfused and brains processed for double immunohistochemical labeling of Fos and nesfatin-1. Abdominal surgery, compared to anesthesia alone, induced Fos expression in neurons of the supraoptic nucleus (SON), paraventricular nucleus (PVN), locus coeruleus (LC), Edinger-Westphal nucleus (EW), rostral raphe pallidus (rRPa), nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM). Double Fos/nesfatin-1 labeling showed that of the activated cells, 99% were nesfatin-1-immunoreactive in the SON, 91% in the LC, 82% in the rRPa, 74% in the EW and VLM, 71% in the anterior parvicellular PVN, 47% in the lateral magnocellular PVN, 41% in the medial magnocellular PVN, 14% in the NTS and 9% in the medial parvicellular PVN. These data established nesfatin-1 immunoreactive neurons in specific nuclei of the hypothalamus and brainstem as part of the neuronal response to abdominal surgery and suggest a possible implication of nesfatin-1 in the alterations of food intake and gastric transit associated with such a stressor.

Clinical trial: the impact of cyclooxygenase inhibitors on gastrointestinal recovery after major surgery - a randomized double blind controlled trial of celecoxib or diclofenac vs. placebo

BACKGROUND

Ileus occurs after abdominal surgery and may be severe. Inhibition of prostaglandin release reduces post-operative ileus in a rat model.

AIM

To determine whether prostaglandin inhibition by cyclooxygenase inhibitors, celecoxib or diclofenac, could enhance gastrointestinal recovery and reduce post-operative ileus in humans.

METHODS

Two hundred and ten patients undergoing elective major abdominal surgery were randomized to receive twice daily placebo (n = 67), celecoxib (100 mg, n = 74) or diclofenac (50 mg, n = 69), preoperatively and continuing for up to 7 days. Primary outcomes were hallmarks of gut recovery. Secondary outcomes were paralytic ileus, pain and complications.

RESULTS

There was no clinically significant difference between the groups for restoration of bowel function. There was a significant reduction in paralytic ileus in the celecoxib-treated group (n = 1, 1%) compared with diclofenac (n = 7, 10%) and placebo (n = 9, 13%); P = 0.025, RR 0.20, CI 0.01-0.77. Pain scores, analgesia, transfusion requirements and adverse event rates were similar between study groups.

CONCLUSIONS

Perioperative low dose celecoxib, but not diclofenac, markedly reduced the development of paralytic ileus following major abdominal surgery, but did not accelerate early recovery of bowel function. This was independent of narcotic use and had no increase in post-operative complications.

Postoperative ileus: pathogenesis and treatment

Surgical manipulation of the intestines activates intestinal macrophages that release cytokines and nitric oxide, which results in inhibition of intestinal motility. Subsequent infiltration of circulating leukocytes into the intestinal wall contributes to cytokine and nitric oxide release and exacerbates ileus. Other factors contributing to ileus are endotoxemia; edema of the intestine wall subsequent to excessive fluid therapy; hypocalcemia; and long abdominal incisions. Because treatment of ileus with prokinetic drugs has not proven to be very effective, efforts should be directed at reducing its severity. Strategies which reduce the severity of ileus include pretreatment with a nonsteroidal anti-inflammatory drug, minimizing the length of the abdominal incision, reducing intestinal manipulation, intraoperative lidocaine infusion, correction of hypocalcemia, limiting the volume of intravenous fluids to prevent intestinal edema, and administration of alpha(2) antagonists.

Abdominal surgery affects small bowel transit time and completeness of capsule endoscopy

The aim of the study was to evaluate bowel dysmotility in patients with a history of abdominal surgery by measuring both gastric transit time and small bowel transit time during capsule endoscopy and assessing the completeness of the examination. The study included 26 patients who had undergone abdominal surgery (postoperative group) and 52 patients who had not (control group). The capsule reached the cecum in 50.0% of the postoperative group and 80.8% of the control group (P=0.005). While there was no significant difference in gastric transit time between the two groups (P=0.882), small bowel transit time was significantly longer in the postoperative group (338.3+/-119.2 min) than in the control group (266.4+/-110.8 min, P=0.010). This is the first study to report that the small bowel transit time during capsule endoscopy is prolonged in patients who had a history of abdominal surgery, resulting in a lower frequency of complete examination.

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.

Jejunal cholinergic, nitrergic, and soluble guanylate cyclase activity in postoperative ileus

BACKGROUND

In animal models of postoperative ileus (POI), inflammation of the intestine plays an important role in the pathogenesis of POI. Changes in alpha(2)-adrenoceptors and nitrergic regulation have been proposed to be implicated. The aim of our study was to investigate the presynaptic alpha(2)-receptor-mediated control of cholinergic nerve activity, the nitrergic nerve activity, and the possible role of soluble guanylate cyclase (sGC) during the inflammatory phase of POI.

METHODS

Ileus was induced by anesthesia and manipulation of the rat jejunum. Rats were treated with the sGC inhibitors methylene blue or ODQ; nonoperated animals served as controls. After 24 h, plasma and jejunal tissue were collected for biochemical assays, nitric oxide synthase-1 (NOS-1)-immunohistochemistry, acetylcholine (Ach)-release experiments, and muscle tension experiments.

RESULTS

In all operated animal groups, myeloperoxidase activity was significantly increased, which indicates initiation of an inflammatory response. The alpha(2)-adrenoceptor agonist UK14,304 reduced electrically induced Ach-release similarly in operated and nonoperated animals. In strips of operated animals, electrically induced nitrergic relaxations were decreased, whereas relaxations induced by exogenous nitric oxide (NO) remained unchanged compared with control. The number of myenteric neurons and the percentage of NOS-1-positive neurons were not influenced. Plasmatic cyclic guanosine monophosphate (cGMP) levels were decreased in all operated groups, whereas jejunal cGMP levels were unchanged compared with nonoperated controls; treatment with sGC inhibitors did not reduce plasmatic cGMP levels.

CONCLUSIONS

This study demonstrates that presynaptic alpha(2)-receptor mediated control of intestinal cholinergic nerve activity is unchanged during manipulation-induced inflammation. However, this inflammation induces impaired nitrergic neurotransmission related to decreased NOS-1 activity in the nitrergic nerves.