A model to investigate postoperative ileus with strain gauge transducers in awake rats

Increased proinflammatory cytokines in mesenteric fat in major surgery and Crohn's disease

BACKGROUND

Proinflammatory cytokines play an important role in abdominal surgery and are often associated with the development of postoperative ileus, especially in Crohn's disease. The aim of this study was to investigate proinflammatory cytokine levels in mesenteric fat in Crohn's disease and patients without Crohn's disease.

METHODS

Human mesenteric tissue specimen were divided into 3 patient groups (n = 10 each): minor surgery (laparoscopic cholecystectomy), major surgery (colectomy) in patients without Crohn's disease, and major surgery (colectomy) in patients with Crohn's disease. Levels of interleukin 6, interleukin 1-β, and tumor necrosis factor α were determined by cytometric bead array, enzyme-linked immunosorbent assay and reverse transcription polymerase chain reaction. The Kruskal-Wallis and the Mann-Whitney U test were used to compare continuous variables. For categorical variables, the χ² test or Fisher exact test was used.

RESULTS

In minor surgery, cytokines levels of interleukin 6, interleukin 1-β and Tumor necrosis factor α were low (ie, interleukin 6: 1 pg/mL [0-36], interleukin 1-β: 0 fg/mL [0-18], tumor necrosis factor α: 157 fg/mL [91-237]) compared with major surgery in patients with and without Crohn's disease. Cytokines were significantly higher in major surgery (ie, interleukin 6: 147 pg/mL [29-347], interleukin 1-β: 660 fg/mL [0-2580], tumor necrosis factor α: 532 fg/mL [289-1647]; P = .02 and major surgery with CD (cytometric bead array: interleukin 6: 94 pg/mL [24-627], interleukin 1-β: 708 fg/mL [0-1664], tumor necrosis factor α: 733 fg/mL [209-1,354]; P < .05). Cytokine levels in major surgery with Crohn's disease showed a further increase of interleukin 6 in polymerase chain reaction in comparison to major surgery in patients without Crohn's disease (1.2 vs 4, P = .04).

CONCLUSION

Proinflammatory cytokines are increased in the mesenteric fat in major operations compared to minor operations, which indicates local mesenteric inflammation. In Crohn's disease, levels of proinflammatory cytokines are even higher, which may put the patients at risk for postoperative ileus.

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.

Risk factors for ileus after hip and knee arthroplasty

PURPOSE

Postoperative ileus (POI) is one of the complications that can occur after every surgical procedure including arthroplasty. It can have detrimental consequences for the patient and portrays an economic burden on health care systems. The risk factors for POI after arthroplasty described in the literature are scarce and include hip arthroplasty, male gender and previous abdominal surgery. The purpose of the study was to determine the risk factors for POI after hip and knee arthroplasty.

METHODS

A retrospective review of 2760 patients undergoing primary hip and knee arthroplasty was performed. An in-depth analysis of patient history and physical operative and postoperative course was reviewed and statistically analyzed in a univariate and multivariate setting.

RESULTS

Overall incidence of POI was 0.54%. History of myocardial infarction and chronic kidney disease were statistically significant risk factors for developing POI after arthroplasty with values of p = 0.023 and p = 0.004, respectively. Other risk factors included previous abdominal surgery (p < 0.001) and hip arthroplasty (p = 0.026). Age or gender correlations were not observed.

CONCLUSIONS

Although postoperative ileus is an uncommon complication after joint arthroplasty, in addition to the known risk factors of male age, hip arthroplasty, and previous abdominal surgery, this study describes two previously unknown risk factors: chronic kidney disease and history of myocardial infarction. Patients with these risk factors should be monitored closely for developing postoperative ileus.

Effect of DA-9701, a Novel Prokinetic Agent, on Post-operative Ileus in Rats

Background/Aims

Post-operative ileus (POI) is a common complication of abdominal surgery. DA-9701, an extract of Pharbitis Semen and Corydalis Tuber, is a new prokinetic agent that also alleviates visceral pain. The aim of this study was to investigate whether DA-9701 can ameliorate POI in rats.

Methods

A total of 32 rats were divided into 4 groups: no surgery/no medication (NSNM), no surgery/medication (NSM), surgery/no medication (SNM), and surgery/medication (SM). Gastrointestinal transit (GIT), which is assessed by migration of charcoal, and cumulative stool weight were measured at 24 hours after surgery.

Results

GIT was significantly more delayed in the SNM group than in the other groups (SNM vs NSNM, P < 0.001; SNM vs NSM, P < 0.001; SNM vs SM, P = 0.005). Cumulative stool weight in that group was also lower than in the no surgery groups (SNM vs NSNM, P = 0.007; SNM vs NSM, P = 0.033), and there was no significant difference between the SM group and the no surgery groups (SM vs NSM, P = 0.703; SM vs NSNM, P = 0.347).

Conclusion

DA-9701 can ameliorate POI by reducing delayed GIT and improving defecation in a rat model of POI.

Autonomic consequences of spinal cord injury

Spinal cord injury (SCI) results not only in motor and sensory deficits but also in autonomic dysfunctions. The disruption of connections between higher brain centers and the spinal cord, or the impaired autonomic nervous system itself, manifests a broad range of autonomic abnormalities. This includes compromised cardiovascular, respiratory, urinary, gastrointestinal, thermoregulatory, and sexual activities. These disabilities evoke potentially life-threatening symptoms that severely interfere with the daily living of those with SCI. In particular, high thoracic or cervical SCI often causes disordered hemodynamics due to deregulated sympathetic outflow. Episodic hypertension associated with autonomic dysreflexia develops as a result of massive sympathetic discharge often triggered by unpleasant visceral or sensory stimuli below the injury level. In the pelvic floor, bladder and urethral dysfunctions are classified according to upper motor neuron versus lower motor neuron injuries; this is dependent on the level of lesion. Most impairments of the lower urinary tract manifest in two interrelated complications: bladder storage and emptying. Inadequate or excessive detrusor and sphincter functions as well as detrusor-sphincter dyssynergia are examples of micturition abnormalities stemming from SCI. Gastrointestinal motility disorders in spinal cord injured-individuals are comprised of gastric dilation, delayed gastric emptying, and diminished propulsive transit along the entire gastrointestinal tract. As a critical consequence of SCI, neurogenic bowel dysfunction exhibits constipation and/or incontinence. Thus, it is essential to recognize neural mechanisms and pathophysiology underlying various complications of autonomic dysfunctions after SCI. This overview provides both vital information for better understanding these disorders and guides to pursue novel therapeutic approaches to alleviate secondary complications.

New telemetry device for the measurement of gastrointestinal motility in rats and comparison with standard equipment

To perform stress-free recording of gastrointestinal motility in rats with strain gauge transducers, telemetry equipment had to be developed. We developed, programmed, and tested a new telemetry device that records gastrointestinal motility in freely moving rats using strain gauge transducers. The device can collect and transmit data in freely moving rats. Data are received and stored for later analysis with a regular PC. Linear calibration curves were obtained for the strain gauge transducers used. We compared data obtained with the new telemetry device with data gathered with standard equipment and could not find any statistically significant difference. Wired gastric and colonic contraction frequencies were 4.6 ± 0.3 per minute and 1.5 ± 0.3 per minute, whereas telemetric contraction frequencies were 4.4 ± 0.1 per minute and 1.25 ± 0.1 per minute. The new telemetry device is a very useful tool for the measurement of gastrointestinal motility in rats.

Randomized clinical trial of the effect of glucocorticoids on peritoneal inflammation and postoperative recovery after colectomy

Background

Recent data have suggested a relationship between postoperative fatigue and the peritoneal cytokine response after surgery. The aim of this study was to test the hypothesis that preoperative administration of glucocorticoids before surgery would decrease fatigue and enhance recovery, by reducing the peritoneal production of cytokines.

Methods

In a double-blind randomized controlled study, patients undergoing elective, open colonic resection were administered 8 mg dexamethasone or normal saline. Patients were treated within an enhanced recovery after surgery programme. Primary outcomes were cytokine levels in peritoneal drain fluid and fatigue as measured by the Identity–Consequence Fatigue Scale (ICFS).

Results

Baseline parameters were similar for 29 patients in the dexamethasone group and 31 in the placebo group. Patients who received dexamethasone had lower ICFS scores on days 3 and 7. Dexamethasone was associated with significantly lower peritoneal fluid interleukin (IL) 6 and IL-13 concentrations on day 1, and these correlated with changes in the ICFS score. There was no significant increase in adverse events in the dexamethasone group.

Conclusion

Preoperative administration of dexamethasone resulted in a significant reduction in early postoperative fatigue, associated with an attenuated early peritoneal cytokine response. Peritoneal production of cytokines may therefore be important in postoperative recovery. Registration number: ACTRN12607000066482 (http://www.anzctr.org.au/).

Quantitative analysis of peristaltic and segmental motion in vivo in the rat small intestine using dynamic MRI

Conventional methods of quantifying segmental and peristaltic motion in animal models are highly invasive; involving, for example, the external isolation of segments of the gastrointestinal (GI) tract either from dead or anesthetized animals. The present study was undertaken to determine the utility of MRI to quantitatively analyze these motions in the jejunum region of anesthetized rats (N = 6) noninvasively. Dynamic images of the GI tract after oral gavage with a Gd contrast agent were acquired at a rate of six frames per second, followed by image segmentation based on a combination of three-dimensional live wire (3D LW) and directional dynamic gradient vector flow snakes (DDGVFS). Quantitative analysis of the variation in diameter at a fixed constricting location showed clear indications of both segmental and peristaltic motions. Quantitative analysis of the frequency response gave results in good agreement with those acquired in previous studies using invasive measurement techniques. Principal component analysis (PCA) of the segmented data using active shape models resulted in three major modes. The individual modes revealed unique spatial patterns for peristaltic and segmental motility.

The effects of intestinal ischemia on colonic motility in conscious rats

BACKGROUND

The present study aimed to examine whether and how colonic motility is affected by mild ischemia-induced intestinal injury in conscious rats through in vivo monitoring of colonic contractions, specifically with regard to the interstitial cells of Cajal (ICC) and the effect of nitric oxide (NO).

METHODS

Using miniature strain-gauge transducers, colonic motility with or without ischemia was recorded in conscious rats on the 4th, 7th, and 14th days after surgery. Histological examination for c-kit-positive cells was performed.

RESULTS

In control nonischemic rats, the number and duration of contractions (NC and DC, respectively) decreased gradually, but the mean amplitude of contractions (MC) and motility index (MI) did not change. On the 7th day, the NC in the ischemic group increased significantly when compared with that in the control group (P = 0.037). The DC in the ischemic group was lower than that in the control group; the difference was significant on the 4th day (P = 0.008). The MIs in the ischemic group were lower than those in the control group. In both groups, administration of NGnitro-L: -arginine methyl ester on the 7th day increased only the resting cecal motility. Pathological examinations revealed c-kit-positive cells in both groups.

CONCLUSIONS

Changes such as increased NC with shortened DC accompanied with decreased MI must have occurred at the ischemic site and might have been induced by an ischemic event. However, there exists a possibility that ICC and NO do not play a role in mild ischemia-induced dysmotility.

Postoperative ileus after total joint arthroplasty

We evaluated the incidence and risk factors for postoperative ileus (POI) after total joint arthroplasty in a consecutive group of patients between January 2004 and December 2005 using regional anesthesia and multimodal pain management protocols. Postoperative ileus developed in 31 (0.7%) of 4567 patients. Of these patients, 21 (67.7%) were men, and 10 (32.3%) were women, with a mean age of 68 years (range, 52-91 years). The ileus was treated successfully in 29 patients during the hospitalization. One patient died from this complication, and another one required sigmoid colon resection due to perforation. The risk factors for developing POI after joint arthroplasty were older age, male sex, hip arthroplasty, and prior history of abdominal surgery. The type and dose of narcotic medications, as administered using our current protocol, did not appear to influence the development of POI.

Kynurenic acid inhibits intestinal hypermotility and xanthine oxidase activity during experimental colon obstruction in dogs

Kynurenic acid (KynA), an endogenous antagonist of N-methyl-d-aspartate (NMDA) glutamate receptors, protects the central nervous system in excitotoxic neurological diseases. We hypothesized that the inhibition of enteric glutamate receptors by KynA may influence dysmotility in the gastrointestinal tract. Group 1 of healthy dogs served as the sham-operated control, in group 2, the animals were treated with KynA, while in groups 3 and 4 mechanical colon obstruction was maintained for 7 h. Group 4 was treated with KynA at the onset of ileus. Hemodynamics and motility changes were monitored, and the activities of xanthine oxidoreductase (XOR) and myeloperoxidase (MPO) were determined from tissue samples. Colon obstruction induced a hyperdynamic circulatory reaction, significantly elevated the motility index and increased the mucosal leucocyte accumulation and the XOR activity. The KynA treatment augmented the tone of the colon, permanently decreased the motility index of the giant colonic contractions and reduced the increases in XOR and MPO activities. These effects were concomitant with the in vitro inhibition of XOR activity. In conclusion, KynA antagonizes the obstruction-induced motility responses and XOR activation in the colon. Inhibition of enteric NMDA receptors may provide an option to influence intestinal hypermotility and inflammatory changes.

Effects of neurotrophin 3 on gastric and colonic motility in awake rats

Neurotrophin 3 (NT3) and its receptors are expressed throughout the gastrointestinal tract, especially in the enteric nervous system. However, little is known about the effects of NT3 on gastrointestinal motility. To investigate the effects of NT3 on gastric or colonic motility under baseline conditions, after subdiaphragmatic vagotomy and in a model of postoperative ileus. Sprague-Dawley rats were equipped with strain gauge transducers on the gastric or colonic wall. Motility was recorded for 30 min, followed by i.v. administration of NT3 and motility-recording for another 60 min. Experiments were performed on three consecutive days and separately in a postoperative ileus model. To evaluate a vagal pathway, experiments were also performed on vagotomized rats. NT3 inhibited gastric motility. This inhibitory effect was reduced by subdiaphragmatic vagotomy. Preoperative treatment with NT3 prolonged the postoperative gastric ileus compared to vehicle treatment. Colonic motility in the intact animal was unchanged by NT3, but was increased postoperatively. NT3 treatment inhibited gastric but not colonic motility. This inhibition of gastric motility seems to be partly mediated by the vagus nerve. NT3 aggravates gastric postoperative ileus but attenuates colonic postoperative ileus, which corresponds to the observed positive effects of NT3 on constipated patients.

The duration of postoperative ileus after elective colectomy is correlated to surgical specialization

AIM

Postoperative ileus is an important factor of complications following gastrointestinal procedures. Its pathophysiology and the parameters, which may impact on its duration, remain unclear. The aim of this study was to measure the role of various clinical determinants on restoration of intestinal function after elective colorectal surgery.

METHODS

From July 2002 to September 2003, all patients who underwent laparotomy for colectomy (laparoscopic resections excluded) with either an ileotransverse, colocolic, or high colorectal anastomosis were entered in this prospective study. The intervals in hours between the end of the surgical procedure and passing of flatus (PG) and passing of stool (PS) were recorded by an independent investigator. PG and PS were eventually correlated with the following parameters: type of colectomy, early removal of nasogastric tube (NGT), mechanical bowel preparation (MBP), type of underlying disease, systemic administration of opiates, and surgical training (colorectal fellowship or other).

RESULTS

One hundred twenty-four patients were entered in this study. Four patients (3.2%) developed septic complications (3 anastomotic leaks and 1 intraabdominal abscess) and were excluded from the analysis. Median age in this population was 68 (range 30-95) years. Mean duration of postoperative ileus was 70+/-28 h (PG) and 99+/-34 h (PS). The type of colectomy, underlying disease, MBP, and early NGT removal failed, in univariate analysis, to correlate with the duration of postoperative ileus. By contrast, time intervals PG and PS were statistically shorter in the group of patients treated by a colorectal surgeon [56+/-23 vs 74+/-28 h (PG); 82+/-26 vs 103+/-35 h (PS), p=0.004], as well as in patients who received systemic opiates for less than 2 days [64+/-27 vs 75+/-28 h (PG), p=0.04; 88+/-32 vs 108+/-33 h (PS), p=001].

CONCLUSION

Restoration of normal intestinal function after elective open colectomy takes 3 (PG) to 4 (PS) days. In our series, specialized training in colorectal surgery has a positive impact on the duration of postoperative ileus. Surgical specialization should be considered an important parameter in future clinical trials aiming to minimize postoperative ileus.

Intestinal nitric oxide synthase activity changes during experimental colon obstruction

OBJECTIVE

The experiments in this study were designed to follow the time course of nitric oxide (NO) synthesis in the large bowel during acute mechanical ileus.

MATERIAL AND METHODS

Occlusion of the mid-transverse colon was maintained for 420 min in anesthetized dogs. Strain-gauge transducers were used to analyze motility changes on the hepatic and lienal flexures, respectively. Constitutive NO synthase (cNOS) and inducible NOS (iNOS) activities were determined in tissue biopsies, and plasma nitrite/nitrate (NOx) level was measured in the portal blood. Following completion of the baseline studies, the animals were treated with either 7-nitroindazole (7-NI, selective neuronal NOS inhibitor), or N-nitro-L-arginine (NNA, non-selective NOS inhibitor).

RESULTS

In the sham-operated group the cNOS activities differed significantly in the oral and aboral tissue samples (oral: 102.9; versus aboral: 62.1 fmol/mg protein/min). The obstruction elicited a significant increase in portal NOx and elevated tissue inducible NO synthase (iNOS) activity. NNA treatment decreased the motility index in both intestinal segments for 60 min, but 120 min later the motility index was significantly elevated (2.5-fold increase in the oral part, and 1.8-fold enhancement in the aboral segment, respectively). Treatment with 7-NI decreased the cNOS activity in the oral and aboral parts by approximately 40% and 70%, respectively, and suppressed the motility increase in the aboral colon segment.

CONCLUSIONS

The motility of the colon was either significantly increased or decreased, depending on the type and selectivity of the NOS inhibitor compounds applied. NO of neuronal origin is a transmitter that stimulates peristaltic activity; but an increased iNOS/nNOS ratio significantly moderates the obstruction-induced motility increase.

Nitric oxide synthase inhibition results in immediate postoperative recovery of gastric, small intestinal and colonic motility in awake rats

BACKGROUND

Nitric oxide (NO) is known to inhibit gastrointestinal motility. However, no detailed analysis of gastric, small intestinal and colonic motor effects, including effects on contraction frequency, has, as yet, been reported after NO inhibition in awake rats. We therefore investigated the effects of NO synthase inhibition on gastric, small intestinal and colonic motility in awake rats under baseline conditions and in a postoperative ileus model.

METHODS

In Sprague-Dawley rats, strain gauge transducers were sutured either to the gastric corpus, the small intestine or the colon. After 3 days, L-NMMA (NO synthase inhibitor), D-NMMA or vehicle was given i.v., while the motility was recorded continuously. In addition, postoperative gastric, small intestinal or colonic motility was investigated after L-NMMA or vehicle treatment prior to abdominal surgery. The motility index, the contraction amplitude, the area under the contraction amplitude and the contraction frequency were analysed.

RESULTS

L-NMMA decreased gastric motility to 60+/-8% for about 15 min, but continuously increased small intestinal motility to 221+/-22% and colonic motility to 125+/-7% compared to baseline (baseline=100%; p<0.01 for all comparisons). L-NMMA increased the contraction frequency throughout the gastrointestinal tract (stomach, 13+/-2%; small intestine, 8+/-1%; colon, 16+/-5%; p<0.01 vs. baseline for all comparisons). L-NMMA injection prior to surgery did not prohibit intraoperative inhibition of gastrointestinal motility, but did result in immediate recovery of gastric, small intestinal and colonic motility postoperatively (L-NMMA vs. vehicle, 0-60 min postoperatively; stomach, 90+/-9% vs. 53+/-3%; small intestine, 101+/-5% vs. 57+/-3%; colon, 134+/-6% vs. 60+/-5%; p<0.01 for all comparisons; no significant difference between preoperative baseline motility and L-NMMA treated rats postoperatively).

CONCLUSIONS

Under baseline conditions, endogenous NO inhibits small intestinal and colonic motility and gastric, small intestinal and colonic contraction frequency in awake rats. In the early postoperative period, endogenous NO is a major inhibitory component that seems to constitute the common final pathway of mediators and the neural pathways inhibiting gastrointestinal motility in rats.

Impaired gastric motor activity after abdominal surgery in rats

Postoperative ileus (POI) is a transient bowel dysmotility that occurs following abdominal surgery. Several mechanisms have been proposed such as neural reflex and inflammatory changes. We focused on gastric motility after abdominal surgery in rats. To investigate the time course of gastric motility after surgery, gastric motility was continuously recorded before, during and after surgery. After laparotomy, terminal ileum was manipulated for 10 min. Gastric motility was recorded by a strain gauge transducer implanted on the serosal surface of the stomach. To investigate whether peripheral sympathetic nerve is involved in the pathogenesis of POI, effects of guanethidine and celiac ganglionectomy were tested on the postoperative gastric motility. Although isoflurane anaesthesia reduced the gastric motility to 40%, the motility recovered immediately when isoflurane was withdrawn. Intestinal manipulation reduced the postoperative gastric motility for 3-24 h after surgery, compared with preoperative levels. Guanethidine administration and celiac ganglionectomy restored the impaired gastric motility. Feeding increased the gastric motility in each group. It is suggested that the pathogenesis of postoperative gastric ileus induced by intestinal manipulation involves viscero-sympathetic pathways. Intestinal manipulation causes impaired gastric motility via inhibitory sympathetic efferent pathway. Feeding may improve the postoperative gastric motility.

Mesenteric lymph collected during peritonitis or sepsis potently inhibits gastric motility in rats

Gastrointestinal motility is strongly inhibited during peritonitis or sepsis and proinflammatory cytokines released into mesenteric lymph during an acute gastrointestinal insult mediate systemic responses. We investigated whether mesenteric lymph collected during peritonitis or sepsis inhibits gastric motility and gastric emptying. Mesenteric lymph was collected for 12 hours from three experimental groups: vehicle (saline, 1 ml, intraperitoneally [ip], control lymph), peritonitis (0.5% acetic acid, 1 ml, ip, peritonitis lymph), and sepsis (lipopolysaccharide [LPS], 5 mg/kg, 1 ml, ip, sepsis lymph). Gastric motility and gastric emptying were measured in recipient rats in response to lymph injections into the jugular vein. Quantitative polymerase chain reaction (PCR) for tumor necrosis factor alpha (TNFalpha) gene expression in the jejunum and in lymph cells were measured during sepsis. Mesenteric lymph flow significantly increased during peritonitis or sepsis (lymph flow [ml] per 60 minutes; control 2.45 +/- 0.04; peritonitis 2.67 +/- 0.07; sepsis 3.25 +/- 0.1, p < 0.01 vs. control). Injection of peritonitis or sepsis lymph (1 ml) produced a significant and prolonged inhibition of gastric motility in recipient rats (decrease in intragastric pressure and duration: control lymph -0.14 +/- 0.05 cm H(2)O, 1.89 +/- 1.31 minutes; peritonitis lymph: -0.56 +/- 0.06 cm H(2)O, 9.9 +/- 0.9 minutes; sepsis lymph: -0.51 +/- 0.05 cm H(2)O, 6.9 +/- 0.6 minutes; p < 0.001 vs. control for all comparisons). Gastric emptying was significantly inhibited by continuous infusion of sepsis lymph (3 ml per 60 minutes; gastric emptying: saline 81% +/- 4%; control lymph: 80% +/- 6%; sepsis lymph: 44% +/- 10%; p < 0.001 vs. control). TNFalpha gene expression in the gut wall of the jejunum increased during sepsis over 90-fold within the first 2 hours and decreased continuously thereafter (relative TNFalpha mRNA transcription: basal 1.0 +/- 0.05; LPS 2 hours: 91.9 +/- 2.6, p < 0.001 vs. basal; 12 hours: 24.7 +/- 16.8, not significant [NS]; 24 hours: 7.0 +/- 3.4, NS). In conclusion, mediators in mesenteric lymph, possibly cytokines, may be responsible for the inhibition of gastric motility during peritonitis or sepsis. Because the composition of mesenteric lymph probably reflects the interstitial fluid of the gut wall, monitoring visceral lymph might be an extremely beneficial tool to determine mediators released during impaired gut wall function.

Postoperative ileus: a review

PURPOSE

Postoperatively, some patients experience a prolonged inhibition of coordinated bowel activity, which causes accumulation of secretions and gas, resulting in nausea, vomiting, abdominal distension, and pain. This prolonged inhibition can take days or weeks to resolve and often is referred to as postoperative paralytic ileus lasting more than three days after surgery. This article reviews the etiology, pathophysiology, and treatment options of postoperative ileus.

METHODS

The relevant literature from 1965 to 2003 was identified and reviewed using MEDLINE database of the U.S. Medical Library of Medicine. Both retrospective and prospective studies were included in this review.

RESULTS

The pathophysiology of postoperative ileus is multifactorial. The duration of postoperative ileus correlates with the degree of surgical trauma and is most extensive after colonic surgery. However, postoperative ileus can develop after all types of surgery including extraperitoneal surgery. A variety of treatment options have been used to decrease the duration of postoperative ileus. However, it is difficult to compare these studies because of small sample sizes and differences in operations performed, anesthesia protocols provided both intraoperatively and postoperatively, patient comorbidities, and in the measured end points, such as the time to the presence of bowel sounds, flatus, or bowel movements, tolerance of solid food, or discharge from the hospital. However, despite these drawbacks, some conclusions can be made.

CONCLUSIONS

Paralytic postoperative ileus continues to be a significant problem after abdominal and other types of surgery. The etiology is multifactorial and is best treated with a combination of different approaches. Currently, the important factors that could effect the duration and recovery from postoperative ileus include limitation of narcotic use by substituting alternative medications such as nonsteroidals and placing a thoracic epidural with local anesthetic when possible. The selective use of nasogastric decompression and correction of electrolyte imbalances also are important factors to consider.

Thoracic epidural anesthesia improves the gastric microcirculation during experimental gastric tube formation

BACKGROUND

Gastric tube formation is a surgical technique to reestablish the continuity of the gastrointestinal tract after esophagectomy. Our aims were to study the microcirculatory consequences of experimental gastric tube formation and characterize the effects of thoracic epidural anesthesia (TEA) during this condition.

METHODS

The experiments were performed on mongrel dogs anesthetized with pentobarbital. The stomach was prepared for replacement according to the method of Akiyama, and TEA was induced with bupivacaine (1 mg/kg). Macrohemodynamics, intramucosal pH, and gastric motility changes were monitored, and intravital video-microscopy with orthogonal polarization spectral imaging technique was used to observe the gastric microcirculation.

RESULTS

The gastric pull-up induced a significant decrease in intramucosal pH. The functional capillary density of the mucosa or subserosa did not change; the red blood cell velocity in the capillaries of the upper part of the gastric tube was decreased in the mucosa, as well as on the serosal side. After epidural anesthesia the red blood cell velocity returned to the baseline, and the gastric and intestinal motility index was significantly increased.

CONCLUSIONS

TEA significantly improves the microcirculation of the distal portion of the gastric tube and increases the intestinal and gastric motility after gastric pull-up. The procedure is favorable and should be recommended during reconstructive esophageal surgery.

Small intestinal transit does not adequately represent postoperative paralytic ileus in rats

Small intestinal transit (SIT) has often been regarded as an index of pathophysiological state of postoperative ileus (PI) in rats. The reliability of SIT as an index of PI was examined in the present study. PI was induced via abdominal surgery (i.e., laparotomy with evisceration and manipulation) in rats. For one group of PI-induced rats, SIT of a charcoal test meal was measured. When necessary, the physical state (i.e., severity and site of distension) of the gastrointestinal (GI) tract in each rat was visually examined. For another group of PI-induced rats, abdominal X-ray radiographs were obtained after introducing the barium sulfate suspension. The abdomen was then opened and the physical state of the GI tract was visually examined. The SIT was decreased in most of the PI-induced rats, and the GI distension was observed, with substantial intersubject variations, in all of the PI-induced rats. However, no linear relationship was evident between the SIT and the severity of GI distension (e.g., at 20 h after PI induction). Instead, the severity and site of GI distension could be monitored by the X-ray radiology. Therefore, the use of SIT as an index of Pi should be substantially limited.

Intestinal motility in an in vivo rat model of intestinal ischemia-reperfusion with special reference to the effects of nitric oxide on the motility changes

BACKGROUND

To clarify the relation between intestinal ischemia-reperfusion (IR) and dysmotility, the authors investigated changes in the motility pattern in the duodenum and jejunum in an in vivo rat model of IR when artery- (and vein-) fed jejunum was clamped transiently. The authors also studied the effect of nitric oxide on the motility changes in this model by means of the administration of L-NAME (N(G)-nitro-L-arginine methyl ester) or S-methylisothiourea sulfate (SMT).

MATERIALS AND METHODS

A force transducer was sutured onto the serosal side of the duodenum or jejunum. After a 3-to 4-day recovery period, contractions were recorded during periods of preischemia, ischemia (60 minutes), and reperfusion (90 minutes). An intestinal IR was produced by clamping and releasing the mesenteric artery and vein with artery forceps.

RESULTS

In the jejunum, there was a prolongation in the duration of contraction and there were decreases in the number of contractions (NC) during the IR. When treated with L-NAME, no decrease in the NC was observed during the 45 to 90 minutes after reperfusion. S-methylisothiourea sulfate did not affect the IR-induced motility changes significantly. In the duodenum, there was a prolongation in the duration of contraction and a decrease in the NC and AC only during the reperfusion. L-NAME or S-methylisothiourea sulfate inhibited the decreases in the NC during the reperfusion.

CONCLUSIONS

Intestinal IR causes motility changes in the ischemic site during the IR and in the nonischemic site during the reperfusion. The IR-induced motility changes partly depend on nitric oxide production.

Small bowel motility: relationship between smooth muscle contraction and electroenterogram signal

A study is made to correlate the electrical and mechanical activity of the smooth muscle of the small bowel. Bioelectrical signal recording from the intestinal serosa (electroenterogram) comprises a slow wave (SW) and spike burst (SB), though only the latter reflects intestinal pressure. The electroenterogram and smooth muscle pressure are simultaneously recorded in the canine small bowel. Spectral and time series analysis of the electroenterogram are performed to establish those electrical parameters that best reflect intestinal pressure. The results reveal an underlying correlation between the estimated parameters of electrical activity and smooth muscle pressure. In addition, parameters derived from the spectral techniques were closely correlated to pressure events in the intestine, even more so than the variables directly acquired from the classical time domain analyses. Specifically, spectral energy above 2 Hz and mean frequency (both calculated from the biosignal periodogram), are parameters that identify intestinal pressure. The extrapolation of these spectral parameters to long time periods could serve to define a motility index (MI) from electrical gut activity. In this context, electroenterogram recording and analysis can contribute to solve problems inherent to manometric recording, though the need for surgical intervention restricts electrical methods to experimental or surgical studies.