Impact of restenting for recurrent colonic obstruction due to tumour ingrowth.

BACKGROUND: Endoscopic stenting is used to palliate malignant large bowel obstruction. A proportion of patients will develop recurrent obstruction due to tumour ingrowth and require reintervention. This study aimed to assess the outcome (clinical success and complication rates) of endoscopic reintervention compared with surgical intervention in patients with stent obstruction due to tumour ingrowth. METHODS: This was an observational study using data from a database of patients who underwent palliative colonic stenting between January 1998 and March 2017 at Christchurch Public Hospital. RESULTS: A total of 190 patients underwent colonic stent insertion, for palliation in 182 cases. Reintervention was performed in 55 (30·2 per cent). Thirty-one patients (17·0 per cent) developed obstruction within the stent at a median of 4·6 (i.q.r. 2·3-7·7) months after the procedure. Of these, 21 had endoscopic restenting and ten underwent surgery. Restenting had technical and clinical success rates of 100 per cent, and involved a significantly shorter length of stay compared with surgery (median 2 (i.q.r. 1-4) versus 11 (6-19) days respectively; P = 0·006). Seven of the 21 patients in the restented group underwent a third palliative intervention. The overall stoma rate in the restented group was significantly lower than that in the surgical group (4 of 21 versus 10 of 10; P < 0·001). There was no difference in complications or survival between the two groups. CONCLUSION: Among palliative patients who develop malignant stent obstruction, endoscopic restenting had a high chance of technical success. It resulted in a shorter hospital stay and lower stoma rate than those seen after surgery.

Seven-dimensional microcanonical treatment of hydrogen dissociation dynamics on Cu(111): clarifying the essential role of surface phonons.

A simple picture of the hydrogen dissociation/associative desorption dynamics on Cu(111) emerges from a two-parameter, full dimensionality microcanonical unimolecular rate theory (MURT) model of the gas-surface reactivity. Vibrational frequencies for the reactive transition state were taken from density functional theory calculations of a six-dimensional potential energy surface [Hammer et al., Phys. Rev. Lett. 73, 1400 (1994)]. The two remaining parameters required by the MURT were fixed by simulation of experiments. These parameters are the dissociation threshold energy, E(0)=79 kJmol, and the number of surface oscillators involved in the localized H(2)Cu(111) collision complex, s=1. The two-parameter MURT quantitatively predicts much of the varied behavior observed for the H(2) and D(2)Cu(111) reactive systems, including the temperature-dependent associative desorption angular distributions, mean translational energies of the associatively desorbing hydrogen as a function of rovibrational eigenstate, etc. The divergence of the statistical theory's predictions from experimental results at low rotational quantum numbers, J < or approximately 5, suggests that either (i) rotational steering is important to the dissociation dynamics at low J, an effect that washes out at high J, or (ii) molecular rotation is approximately a spectator degree of freedom to the dissociation dynamics for these low J states, the states that dominate the thermal reactivity. Surface vibrations are predicted to provide approximately 30% of the energy required to surmount the activation barrier to H(2) dissociation under thermal equilibrium conditions. The MURT with s=1 is used to analytically confirm the experimental finding that partial differential "E(a)(T(s))" partial differential E(t)= -1 for eigenstate-resolved dissociative sticking at translational energies E(t)

Microcanonical unimolecular rate theory at surfaces. III. Thermal dissociative chemisorption of methane on Pt(111) and detailed balance.

A local hot spot model of gas-surface reactivity is used to investigate the state-resolved dynamics of methane dissociative chemisorption on Pt(111) under thermal equilibrium conditions. Three Pt surface oscillators, and the molecular vibrations, rotations, and the translational energy directed along the surface normal are treated as active degrees of freedom in the 16-dimensional microcanonical kinetics. Several energy transfer models for coupling a local hot spot to the surrounding substrate are developed and evaluated within the context of a master equation kinetics approach. Bounds on the thermal dissociative sticking coefficient based on limiting energy transfer models are derived. The three-parameter physisorbed complex microcanonical unimolecular rate theory (PC-MURT) is shown to closely approximate the thermal sticking under any realistic energy transfer model. Assuming an apparent threshold energy for CH(4) dissociative chemisorption of E(0)=0.61 eV on clean Pt(111), the PC-MURT is used to predict angle-resolved yield, translational, vibrational, and rotational distributions for the reactive methane flux at thermal equilibrium at 500 K. By detailed balance, these same distributions should be observed for the methane product from methyl radical hydrogenation at 500 K in the zero coverage limit if the methyl radicals are not subject to side reactions. Given that methyl radical hydrogenation can only be experimentally observed when the CH(3) radicals are kinetically stabilized against decomposition by coadsorbed H, the PC-MURT was used to evaluate E(0) in the high coverage limit. A high coverage value of E(0)=2.3 eV adequately reproduced the experimentally observed methane angular and translational energy distributions from thermal hydrogenation of methyl radicals. Although rigorous application of detailed balance arguments to this reactive system cannot be made because thermal decomposition of the methyl radicals competes with hydrogenation, approximate applicability of detailed balance would argue for a strong coverage dependence of E(0) with H coverage--a dependence not seen for methyl radical hydrogenation on Ru(0001), but not yet experimentally explored on Pt(111).

Microcanonical unimolecular rate theory at surfaces. II. Vibrational state resolved dissociative chemisorption of methane on Ni(100).

A three-parameter microcanonical theory of gas-surface reactivity is used to investigate the dissociative chemisorption of methane impinging on a Ni(100) surface. Assuming an apparent threshold energy for dissociative chemisorption of E(0)=65 kJ/mol, contributions to the dissociative sticking coefficient from individual methane vibrational states are calculated: (i) as a function of molecular translational energy to model nonequilibrium molecular beam experiments and (ii) as a function of temperature to model thermal equilibrium mbar pressure bulb experiments. Under fairly typical molecular beam conditions (e.g., E(t)>/=25 kJ mol(-1), T(s)>/=475 K, T(n)/=100 K the dissociative sticking is dominated by methane in vibrationally excited states, particularly those involving excitation of the nu(4) bending mode. Fractional energy uptakes f(j) defined as the fraction of the mean energy of the reacting gas-surface collision complexes that derives from specific degrees of freedom of the reactants (i.e., molecular translation, rotation, vibration, and surface) are calculated for thermal dissociative chemisorption. At 500 K, the fractional energy uptakes are calculated to be f(t)=14%, f(r)=21%, f(v)=40%, and f(s)=25%. Over the temperature range from 500 K to 1500 K relevant to thermal catalysis, the incident gas-phase molecules supply the preponderance of energy used to surmount the barrier to dissociative chemisorption, f(g)=f(t)+f(r)+f(v) approximately 75%, with the highest energy uptake always coming from the molecular vibrational degrees of freedom. The predictions of the statistical, mode-nonspecific microcanonical theory are compared to those of other dynamical theories and to recent experimental data.

Oropharyngeal and esophageal interrelationships in patients with nonobstructive dysphagia.

Normal swallowing requires the close functional coordination of the mouth, pharynx, and esophagus, and if one of these components becomes functionally impaired, it is likely that the others may be affected. Using videofluoroscopy and manometry in this study, we examined the esophageal phase of swallowing in 12 patients with oropharyngeal dysphagia (group A) and the oropharyngeal components of swallowing in 29 patients with esophageal motor dysfunction and nonobstructive dysphagia (group B). A wide range of esophageal function abnormalities was seen in the first group, including delayed esophageal body peristalsis, spontaneous or simultaneous (tertiary) contractions, esophageal body dilation, proximal bolus redirection, and poor lower esophageal sphincter relaxation. Manometrically, 92% of group A patients were classified as having nonspecific esophageal motility disorder (NSEMD). In a similar fashion, group B patients exhibited many oropharyngeal function abnormalities on videofluorography including disturbed lingual peristalsis, slowed pharyngeal transit time with poor constriction of pharyngeal muscles, and laryngeal vestibular and tracheal bolus penetration. Manometrically, group B patients were classified as having NSEMD, achalasia, diffuse esophageal spasm, nutcracker esophagus, scleroderma, and chronic intestinal pseudoobstruction. In conclusion, oropharyngeal function is significantly altered in patients with esophageal motility disorders and dysphagia, and esophageal motor dysfunction occurs in patients with oropharyngeal dysphagia. These changes may represent either a compensatory mechanism or concomitant involvement of the oropharynx or the esophagus by the underlying neuromotor disorder. We suggest that assessment by esophageal motility and videofluoroscopy of both the oropharyngeal and esophageal phases of swallowing may improve diagnosis and therapy in patients with nonobstructive dysphagia.