No inhibition of gastro-intestinal propulsion after propofol- or propofol/ketamine-N2O/O2 anaesthesia. A comparison of gastro-caecal transit after isoflurane anaesthesia

Influence of Intravenous S-Ketamine on the Pharmacokinetics of Oral Morphine in Healthy Volunteers

BACKGROUND

Subanesthetic ketamine may reduce perioperative consumption of opioids. We studied whether intravenous S-ketamine alters the pharmacokinetics of oral morphine in healthy volunteers.

METHODS

In this paired, randomized, double-blind, crossover trial, 12 participants under a 2-hour intravenous S-ketamine (0.57 mg/kg/h) or placebo infusion received oral morphine (0.2 mg/kg) at 30 minutes. Plasma concentrations of ketamine, morphine, and their major metabolites were quantified for 24 hours. The primary end point was area under the curve (AUC) 0-24 of morphine. Other pharmacokinetic variables for morphine and its metabolites were studied as secondary end points. The data were analyzed as between-phase comparisons for each participant using Wilcoxon matched-pairs signed-rank tests ( tmax ) or paired t -tests on log-transformed variables (other variables).

RESULTS

While the AUC 0-24 was similar between the 2 phases, S-ketamine reduced the AUC 0-1.5 of oral morphine by 69% (ratio to control, 0.31; 90% confidence interval [CI], 0.15-0.65; P = .0171) and increased its tmax from 0.5 (range, 0.50-1.5) to 1.0 hour (range, 0.50-4.0; P = .010). The AUC 0-1.5 of morphine-6-glucuronide (M6G) was reduced by 84% (0.16; 90% CI, 0.07-0.37; P = .0025) and maximum plasma concentration ( Cmax ) by 43% (0.57; 90% CI, 0.40-0.81; P = .0155), while its tmax was increased from 1.5 (range, 1.0-2.0) to 4.0 (range, 1.0-8.0; P = .0094) hours by S-ketamine. Similarly, the AUC 0-1.5 of morphine-3-glucuronide (M3G) was reduced by 85% (0.15; 90% CI, 0.05-0.43; P = .0083), and tmax increased from 1.0 (range, 0.5-1.5) to 4.0 hours (range, 1.0-8.0; P = .0063). In addition, the M6G-to-morphine and M3G-to-morphine metabolic AUC ratios were decreased by 47% (0.53; 90% CI, 0.39-0.71; P = .0033) and 52% (0.48; 90% CI, 0.27-0.85; P = .0043) during 0 to 1.5 hours and by 15% (0.85; 90% CI, 0.78-0.92; P = .0057) and 10% (0.90; 90% CI, 0.83-0.98; P = .0468) during 0 to 24 hours, respectively. One participant was excluded from the analyses due to vomiting in the S-ketamine phase.

CONCLUSIONS

Intravenous S-ketamine inhibited the metabolism of oral morphine and delayed its absorption, resulting in a net reduction in the exposure to morphine during the first 1.5 hours. Intravenous S-ketamine may delay the absorption and impair the efficacy of orally administered analgesics and other drugs.

Impact of anesthetics on pyloric characteristics measured using the EndoFLIP® system in patients with gastroparesis

BACKGROUND

Pyloric distensibility has been reported as a predictive measure in gastroparesis. Measures can be obtained either during endoscopy under anesthesia or in unsedated patients. However, the impact of anesthetic drugs on the results of pyloric characteristics remains unknown. The objective of the present study was to determine the impact of anesthetics on pyloric characteristics measured using EndoFLIP® in patients with gastroparesis.

METHODS

Consecutive patients with gastroparesis from three French tertiary centers were retrospectively analyzed. Patients with a previous history of pyloric intervention were not considered for analysis. Medical records were reviewed for the potential use of anesthetic drugs during EndoFLIP® measurement.

KEY RESULTS

One hundred twenty-five patients were included in the present study [median age: 55.0 years (43.0-66.0)]. Thirty-four patients (27.2%) had pyloric assessment without general anesthesia and 91 patients (72.8%) with general anesthesia. Pyloric pressure at 40 mL of distension was higher in patients with general anesthesia in comparison with patients without general anesthesia [18.7 (13.0-25.6) mmHg vs. 15.4 (11.9-20.7) mmHg; p = 0.044)]. In multivariate analysis, suxamethonium chloride administration was associated with decreased pyloric distensibility (OR: 3.9; 95% CI: 1.3-11.4; p = 0.013) while ephedrine was rather associated with increased pyloric distensibility (OR: 0.3; 95% CI: 0.1-0.9; p = 0.036).

CONCLUSIONS AND INFERENCES

This study is the first to have found an impact of general anesthesia on pyloric measurement using the EndoFLIP®. Therefore, further studies are needed to confirm these findings, if possible, prospective studies.

A randomized controlled trial of the effect of ramosetron on postoperative restoration of bowel motility after gynecologic laparoscopic surgery

OBJECTIVE

To investigate the effect of ramosetron after gynecological laparoscopic surgery on the recovery of bowel function.

METHODS

A prospective randomized controlled trial conducted at Kyung Hee University hospital, South Korea, from August 2016 to September 2017. Patients were randomized to receive either 10 mg dexamethasone before induction of anesthesia (control group C), followed by intravenous administration of patient-controlled analgesia (IV-PCA) or 2 ml normal saline before induction of anesthesia and 0.6 mg ramosetron (study group R) administered with IV-PCA.

RESULTS

A total of 88 patients were enrolled. Times to first flatus (group C 23.98 ± 6.31 vs. group R 27.14 ± 9.56 h; P = 0.148) and first defecation (group C 36.16 ± 16.04 vs. group R 43.41 ± 20.01 h; P = 0.138) showed no statistically significant differences. No significant differences were observed in the frequency of postoperative nausea and vomiting (PONV) and demand for additional analgesics. Multiple linear regression for analysis of factors affecting time to first flatus revealed no significant results.

CONCLUSION

Ramosetron did not delay bowel movement recovery after gynecologic laparoscopic surgery and was as effective as dexamethasone in regulating PONV. Ramosetron can be used with IV-PCA without concerns about delay in recovery of bowel function. ClinicalTrials.gov registration number: NCT02849483.

Effect of sedation with dexmedetomidine or propofol on gastrointestinal motility in lipopolysaccharide-induced endotoxemic mice

Background

Sepsis often accompanies gastrointestinal motility disorder that contributes to the development of sepsis in turn. Propofol and dexmedetomidine, as widely used sedatives in patients with sepsis, are likely to depress gastrointestinal peristalsis. We queried whether propofol or dexmedetomidine, at sedative doses, aggravated sepsis-induced ileus.

Methods

Sedative/Anesthetic Scores and vital signs of lipopolysaccharide (LPS)-induced endotoxemic mice were measured during sedation with propofol or dexmedetomidine. Endotoxemic mice were divided into 10% fat emulsion, propofol, saline, and dexmedetomidine group. The gastric emptying, small intestinal transit, tests of colonic motility, gastrointestinal transit and whole gut transit were evaluated at 15 mins and 24 h after intraperitoneal injection of sedatives/vehicles respectively.

Results

40 mg·kg^− 1propofol and 80 μg·kg^− 1 dexmedetomidine induced a similar depth of sedation with comparable vital signs except that dexmedetomidine strikingly decreased heart rate in endotoxemic mice. Dexmedetomidine markedly inhibited gastric emptying (P = 0.006), small intestinal transit (P = 0.006), colonic transit (P = 0.0006), gastrointestinal transit (P = 0.0001) and the whole gut transit (P = 0.034) compared with the vehicle, whereas propofol showed no depression on all parts of gastrointestinal motility 15 mins after administration. The inhibitive effects of dexmedetomidine in these tests vanished 24 h after the administration.

Conclusions

Deep sedation with dexmedetomidine, but not propofol, significantly inhibited gastrointestinal peristalsis in endotoxemic mice while the inhibitory effect disappeared 24 h after sedation. These data suggested that both propofol and dexmedetomidine could be applied in septic patients while dexmedetomidine should be used cautiously in patients with cardiac disease or ileus.

Region specific differences in the effect of propofol on the murine colon result in dysmotility

Propofol is the most widely used intravenous anaesthetic agent for maintenance of anaesthesia and sedation. Studies in varying regions of the bowel have shown conflicting differences on the effects of propofol on motility. There the aim of this study was to understand the influence of propofol on colonic function and explore by which mechanism any changes occur. Functional studies were conducted using isolated colonic tissue from C57BL6 mice which were exposed to 5 μM propofol. Faecal pellet motility, colonic migratory motor complexes (CMMCs) and functional bioassays were utilised to monitor colonic function and nitric oxide production was monitored by amperometry. There was a signficant reduction in amplitude of CMMCs in the distal colon in the presence of 5 μM propofol, however no difference was observed in the proximal colon. A signficant increase in the 5-HT evoked contractions were observed in distal colon in the presence of 5 μM propofol. Additionally, a reduction in the NO production in the presence of 5 μM propofol was only observed in the distal colon. As a result, in the presence of 5 μM propofol, faecal pellet transit was increased, and velocity was reduced. At clinically relevant doses, propofol was shown to reduce colonic motility by inhibiting nitric oxide synthase in only the distal region of the colon. Our findings indicate that propofol has a considerable influence on colonic signalling mechanisms and impairs colonic motility, which may have implications in its clinical use especially for maintenance.

Opportunities and Challenges for Single-Unit Recordings from Enteric Neurons in Awake Animals

Advanced electrode designs have made single-unit neural recordings commonplace in modern neuroscience research. However, single-unit resolution remains out of reach for the intrinsic neurons of the gastrointestinal system. Single-unit recordings of the enteric (gut) nervous system have been conducted in anesthetized animal models and excised tissue, but there is a large physiological gap between awake and anesthetized animals, particularly for the enteric nervous system. Here, we describe the opportunity for advancing enteric neuroscience offered by single-unit recording capabilities in awake animals. We highlight the primary challenges to microelectrodes in the gastrointestinal system including structural, physiological, and signal quality challenges, and we provide design criteria recommendations for enteric microelectrodes.

Initial experience with ketamine-based analgesia in patients undergoing robotic radical cystectomy and diversion

INTRODUCTION

We instituted a ketamine-predominant analgesic regimen in the peri- and postoperative periods to limit the effects of narcotic analgesia on bowel function in patients undergoing radical cystectomy. The primary end points of interest were time to return of bowel function, time to discharge, and efficacy of the analgesic regimen.

METHODS

We performed a retrospective chart review of patients undergoing robotic-assisted laparoscopic cystectomy (RARC) with urinary diversion by a single surgeon at our institution from January 1, 2011 to June 30, 2012. Patients receiving the opioid-minimizing ketamine protocol were compared to a cohort of patients undergoing RARC with an opioid-predominant analgesic regimen.

RESULTS

In total, 15 patients (Group A) were included in the ketamine-predominant regimen and 25 patients (Group B) in the opioid-predominant control group. Three patients (19%) in Group A discontinued the protocol due to ketamine side effects. The mean time to bowel movement and length of stay in Group A versus Group B was 3 versus 6 days (p < 0.001), and 4 versus 8 days, respectively (p < 0.001). Group A patients received an average of 13.0 mg of morphine versus 97.5 mg in Group B (p < 0.001).

CONCLUSIONS

Patients who received our ketamine pain control regimen had a shorter time to return of bowel function and length of hospitalization after RARC. Our study has its limitations as a retrospective, single surgeon, single institution study and the non-randomization of patients. Notwithstanding these limitations, this study was not designed to show inferiority of one approach, but instead to show that our protocol is safe and efficacious, warranting further study in a prospective fashion.

Sedation With Propofol Has No Effect on Capsule Endoscopy Completion Rates: A Prospective Single-Center Study

Patients who need both capsule endoscopy (CE) and colonoscopy often undergo both examinations on the same day to avoid repeated bowel preparation and fasting. Sedation can relieve pain and is commonly used for colonoscopies but may influence the CE completion rate.To determine whether sedation with propofol influences the completion rate and small-bowel transit time (SBTT) of CE.From July 2014 to December 2014, patients (18-65 years old) who needed both CE and colonoscopy were assessed consecutively for enrollment in our study. Colonoscopies were performed with or without sedation based on patient preferences on the day of capsule ingestion. The completion rate, SBTT, and diagnostic yield of CEs were recorded. Patients' satisfaction and pain scores were also recorded.Sedation with propofol had no significant effect on CE completion rates (83.3% sedation group vs 81.8% nonsedation group, P = 0.86) but was associated with increased SBTT (403.6 ± 160.3 sedation group vs 334.5 ± 134.4 nonsedation group, P = 0.006). The diagnostic yields in the sedation and nonsedation groups were 69.4% and 65.9%, respectively (P = 0.74). The median satisfaction scores were 8.6 in the sedation group and 3.5 in the nonsedation group (P < 0.001). Median pain scores were 1.4 in the sedation group and 6.7 in the nonsedation group (P < 0.001).Sedation with propofol increased SBTT but had no effect on CE completion rates, suggesting that CE and colonoscopy with propofol can be performed on the same day (clinical trial registration number: ChiCTR-ONRC-14004866).

Effect of prolonged general anesthesia with sevoflurane and laparoscopic surgery on gastric and small bowel propulsive motility and pH in dogs

OBJECTIVE

To determine if general anesthesia with sevoflurane and laparoscopic surgery changed gastric and small bowel propulsive motility or pH in dogs.

STUDY DESIGN

Prospective, controlled trial.

ANIMALS

Twelve, 19-24 months old, female, Treeing Walker Hound dogs, weighing 23-30 kg.

METHODS

Dogs were anesthetized for a median of 8.5 hours during another study to determine the minimum alveolar concentration of sevoflurane using a visceral stimulus. Gastric and small bowel motility were determined using a sensor capsule that measures pressure, pH and temperature. Gastric transit time and motility index were calculated. For 8/12 dogs, gastric motility, pH and transit time were measured. In 4/12 dogs, small bowel motility and pH were measured.

RESULTS

Anesthesia decreased gastric and small bowel motility but did not change luminal pH. Mean gastric contraction force decreased from median (range) 11 (8-20) to 3 (1-10) mmHg (p < 0.01) and gastric motility index decreased from 0.63 (0-1.58) to 0 (0-0.31; p = 0.01). Frequency of contractions did not change, 3.7 (1.6-4.4) versus 2.8 (0.1-5.1) contractions minute(-1) (p = 0.1). Gastric motility returned to normal 12-15 hours following anesthesia. Gastric emptying was prolonged from 12 (5.3-16) to 49 (9.75-56.25) hours (p < 0.01). Mean small bowel contraction force decreased from 34 (24-37) to 3 (0.9-17) mmHg (p < 0.02) and motility index decreased from 3.75 (1-4.56) to 0 (0-1.53; p = 0.02). Frequency of contractions did not change, 0.5 (0.3-1.4) versus 1.4 (0.3-4.6) contractions minute(-1) (p = 0.11). Small bowel motility returned within 2 hours after anesthesia. Laparoscopy did not result in changes to gastric or small bowel parameters beyond those produced by general anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

The force of gastric and small bowel contractions decreased during sevoflurane anesthesia for laparoscopy. Although gastric motility returned to normal within 12-15 hours the impairment of gastric emptying lasted 30-40 hours, predisposing dogs to postoperative ileus.

Effects of Compound Ketamine Oral Solution on gastrointestinal motility in rats

AIM: To investigate the effects of Compound Ketamine Oral Solution (CKOS) on gastric emptying rate, intestinal transit rate, and plasma motilin levels in rats and to evaluate the safety of application of CKOS to clinical practice.

METHODS: One hundred and twenty-five Wistar rats were randomly divided into five groups (25 rats each): control group (intragastrically given 1 mL distilled water), sauce group (intragastrically given 1 mL sauce solution), midazolam (MID) group (intragastrically given 1 mL MID solution, 10 mg/kg), ketamine (KET) group (intragastrically given 1 mL KET solution, 100 mg/kg), and CKOS group (intragastrically given 1 mL CKOS). These groups were further divided into five subgroups (five rats each) for testing at different time points. After gastric administration, each rat was intragastrically given 1 mL of 0.2% phenolphthalein. Blood samples were taken at 0, 30, 60, 120 and 360 min to measure plasma motilin levels. The stomach and small intestine of the rats in the 30-min subgroup were removed to measure the rates of gastric emptying and intestinal transit, respectively.

RESULTS: In the control group, the motilin levels at 30 and 60 min were significantly higher than that at baseline (219.6 ng/L ± 13.05 ng/L and 235.4 ng/L ± 22.43 ng/L vs 178.3 ng/L ± 15.32 ng/L, both P < 0.01). In the sauce group, the motilin levels at 30 and 60 min were significantly higher than that at baseline and those at corresponding time points in the control group (all P < 0.01). The motilin levels at 30 and 60 min in the KET, MID and CKOS groups were lower than those in the control group at corresponding time points (all P < 0.01 or 0.05). There were no differences in the motilin levels among the KET, MID and CKOS groups. The rates of gastric emptying and intestinal transit were significantly higher in the sauce group than in the control group (both P < 0.01). The rates of gastric emptying at 30 min in the KET, MID and CKOS groups were significantly lower than that in the control group (all P < 0.01 or 0.05). The rate of intestinal transit in the KET group was lower than that in the control group (P < 0.01).

CONCLUSION: CKOS can slow down gastric emptying in rats. KET and MID can inhibit excretion of motilin.

Intensive Care Unit-acquired infection as a side effect of sedation

Introduction

Sedative and analgesic medications are routinely used in mechanically ventilated patients. The aim of this review is to discus epidemiologic data that suggest a relationship between infection and sedation, to review available data for the potential causes and pathophysiology of this relationship, and to identify potential preventive measures.

Methods

Data for this review were identified through searches of PubMed, and from bibliographies of relevant articles.

Results

Several epidemiologic studies suggested a link between sedation and ICU-acquired infection. Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Furthermore, experimental evidence coming from studies both in humans and animals suggest that sedatives and analgesics present immunomodulatory properties that might alter the immunologic response to exogenous stimuli. Clinical studies comparing different sedative agents do not provide evidence to recommend the use of a particular agent to reduce ICU-acquired infection rate. However, sedation strategies aiming to reduce the duration of mechanical ventilation, such as daily interruption of sedatives or nursing-implementing sedation protocol, should be promoted. In addition, the use of short acting opioids, propofol, and dexmedetomidine is associated with shorter duration of mechanical ventilation and ICU stay, and might be helpful in reducing ICU-acquired infection rates.

Conclusions

Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects, and immunomodulatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Future studies should compare the effect of different sedative agents, and the impact of progressive opioid discontinuation compared with abrupt discontinuation on ICU-acquired infection rates.

Bowel function after bowel surgery: morphine with ketamine or placebo; a randomized controlled trial pilot study

BACKGROUND

Morphine decreases gut peristalsis, and ketamine decreases morphine use after surgery, and does not slow peristalsis. Thus, the combination should result in faster return of bowel function after surgery than morphine alone.

METHOD

A double-blind randomized controlled trial of saline vs. ketamine with intravenous patient-controlled-analgesia morphine for post-operative pain control was conducted on 42 patients having bowel resection. Bowel function was assessed by auscultation, time to passage of flatus and stool, and time to first retained oral intake; pain by visual analog scale. Time to return of all four measures of bowel function was the primary outcome.

RESULTS

Despite a ketamine dose that in other studies had decreased morphine use without side-effects, there was no difference in bowel function, pain control, or morphine use between the two groups. Ketamine resulted in hallucinations in six out of 19 patients, with none in the placebo group (P =0.018).

CONCLUSION

Low-dose ketamine was not efficacious for hastening return of bowel function, or for decreasing post-operative pain after surgery for bowel resection. It resulted in hallucinations in some patients. Those reporting hallucinations all wished to remain in the study.

Effects of NMDA receptor antagonists on visceromotor reflexes and on intestinal motility, in vivo

Antagonists of NMDA receptors can inhibit both the transmission of pain signals from the intestine and enteric reflexes. However, it is unknown whether doses of the NMDA antagonist, ketamine, that are used in anaesthetic mixtures suppress motility reflexes and visceromotor responses (VMRs). In fact, whether intestinal motility is affected by NMDA receptor blockers in vivo has been little investigated. We studied the effects of ketamine and memantine, administered intravenously or intrathecally. Rats were maintained under alpha-chloralose plus xylazine or pentobarbitone anaesthesia; VMR and jejunal motility were measured. Under alpha-chloralose/xylazine anaesthesia, i.v. ketamine inhibited VMRs at 6 mg kg h(-1), but not at 3 mg kg h(-1). It did not inhibit propulsive reflexes in the jejunum at 10 mg kg h(-1), but reduced them by 30% at 20 mg kg h(-1). Under alpha-chloralose/pentobarbitone anaesthesia, i.v. ketamine reduced propulsive reflexes at 40 mg kg h(-1) and VMR at 10 mg kg h(-1). Memantine inhibited VMRs at 20 mg kg h(-1) and propulsion at 2 mg kg h(-1). Ketamine and memantine, intrathecally, prevented VMRs, but not jejunal propulsion. We conclude that peripherally administered ketamine reduces both VMR and motility reflexes, but not at doses used in anaesthetic mixes (1.8-2.4 mg kg h(-1)). Effects on motility reflexes are likely to be due to non-NMDA receptor actions, possibly on nicotinic receptors.

The effect of anesthetic technique on early postoperative gastric emptying: comparison of propofol-remifentanil and opioid-free sevoflurane anesthesia

PURPOSE

A postoperative decrease in the gastric emptying (GE) rate may delay the early start of oral feeding and alter the bioavailability of orally administered drugs. The aim of this study was to compare the effect on early gastric emptying between two anesthetic techniques.

METHODS

Fifty patients (age, 19-69 years) undergoing day-case laparoscopic cholecystectomy were randomly assigned to received either total intravenous anesthesia with propofol/remifentanil/rocuronium (TIVA; n = 25) or inhalational opioid-free anesthesia with sevoflurane/rocuronium (mask induction; GAS; n = 25). Postoperative gastric emptying was evaluated by the acetaminophen method. After arrival in the recovery unit, acetaminophen (paracetamol) 1.5 g was given through a nasogastric tube, and blood samples were drawn during a 2-h period. The area under the serum-acetaminophen concentration curve from 0-60 min (AUC60), the maximal concentration (Cmax), and the time to reach C-max (Tmax) were calculated.

RESULTS

Twelve patients were excluded due to surgical complications (e.g., conversion to open surgery) and difficulty in drawing blood samples (TIVA, n = 7; GAS, n = 5). Gastric emptying parameters were (mean +/- SD): TIVA, AUC60, 2458 +/- 2775 min.micromol.l(-1); Cmax, 71 +/- 61 micromol.l(-1); and Tmax, 81 +/- 37 min; and GAS, AUC60, 2059 +/- 2633 min.micromol.l(-1); Cmax, 53 +/- 53 micromol.l(-1); and Tmax, 83 +/- 41 min. There were no significant differences between groups.

CONCLUSION

There was no major difference in early postoperative gastric emptying between inhalation anesthesia with sevoflurane versus total intravenous anesthesia with propofol-remifentanil. Both groups showed a pattern of delayed gastric emptying, and the variability in gastric emptying was high. Perioperative factors other than anesthetic technique may have more influence on gastric emptying.

Peripheral N-methyl-D-aspartate receptors modulate nonadrenergic noncholinergic lower esophageal sphincter relaxation in rabbits

We investigated the role of peripheral N-methyl-D-aspartate (NMDA) receptors in the myenteric plexus in mediating nonadrenergic noncholinergic (NANC) nitrergic relaxation of the lower esophageal sphincter (LES). Isometric contraction of LES strips from Japanese White rabbits was measured. NANC relaxation was induced by KCl (30 mM) in the presence of atropine and guanethidine. The concentration of 3',5'-cyclic guanosine monophosphate (cGMP) was measured using a radioimmunoassay. The muscle strips were exposed to diethyldithiocarbamic acid (DETCA; 3 mM) to inactivate Cu/Zn superoxide dismutase. MK801 (5-methyl-10,11-dihydroxy-5H-dibenzo(a,d)cyclohepten-5,10-imine) inhibited NANC relaxation in a concentration-dependent manner (EC50 = 1.5 x 10(-5) M), accompanied by a decrease in cGMP production. NMDA induced a concentration-dependent relaxation, which was antagonized by MK801. NMDA stimulated cGMP production, which was inhibited by N(G)-nitro-L-arginine. Superoxide dismutase (100 U/mL) shifted the concentration-response relationship of MK801-mediated inhibition of NANC relaxation to the right (EC50 = 3.4 x 10(-5) M), whereas catalase did not. Treatment with DETCA shifted the concentration-response relationships of pyrogallol-, ketamine- and MK801-mediated inhibition of NANC relaxation to the left. These findings suggest that the peripheral NMDA receptors mediate NANC smooth muscle relaxation, and modulate it, in part, through extracellular production of superoxide anions, thus eliminating the relaxant effect of endogenous nitric oxide.

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.

Propofol and midazolam inhibit gastric emptying and gastrointestinal transit in mice

We studied the effect of propofol and midazolam on gastric emptying and gastrointestinal transit in mice. Ten minutes after intraperitoneal injection of propofol or midazolam, 0.2 mL of saline containing fluorescent microbeads was infused into the stomach. Thirty minutes later, the gastrointestinal tract was excised, and gastric emptying and gastrointestinal transit were calculated by measuring the quantity of fluorescent microbeads in the gastrointestinal tract by using a flow cytometer. At a dose that produced a light level of sedation (mice righted themselves within 2 s), both drugs significantly, but weakly, inhibited gastric emptying to a similar degree (propofol: P < 0.001 versus control value; 95% confidence interval [CI] for difference, 4.9%-20.2%; midazolam: P < 0.001 versus control value; 95% CI for difference, 7.8%-14.7%). Midazolam, but not propofol, delayed gastrointestinal transit (P < 0.001). At a larger dose that produced a deeper level of sedation (absence of righting reflex >10 s), both drugs significantly inhibited gastric emptying (propofol: P < 0.001; 95% CI for difference, 31.4%-61.2%; midazolam: P < 0.001; 95% CI for difference, 30.8%-61.1%) and gastrointestinal transit (P < 0.001 for both drugs).