Electric Field Effects on Curved Graphene Quantum Dots.

The recent and continuous research on graphene-based systems has opened their usage to a wide range of applications due to their exotic properties. In this paper, we have studied the effects of an electric field on curved graphene nanoflakes, employing the Density Functional Theory. Both mechanical and electronic analyses of the system have been made through its curvature energy, dipolar moment, and quantum regeneration times, with the intensity and direction of a perpendicular electric field and flake curvature as parameters. A stabilisation of non-planar geometries has been observed, as well as opposite behaviours for both classical and revival times with respect to the direction of the external field. Our results show that it is possible to modify regeneration times using curvature and electric fields at the same time. This fine control in regeneration times could allow for the study of new phenomena on graphene.

Quantum Revivals in Curved Graphene Nanoflakes.

Graphene nanostructures have attracted a lot of attention in recent years due to their unconventional properties. We have employed Density Functional Theory to study the mechanical and electronic properties of curved graphene nanoflakes. We explore hexagonal flakes relaxed with different boundary conditions: (i) all atoms on a perfect spherical sector, (ii) only border atoms forced to be on the spherical sector, and (iii) only vertex atoms forced to be on the spherical sector. For each case, we have analysed the behaviour of curvature energy and of quantum regeneration times (classical and revival) as the spherical sector radius changes. Revival time presents in one case a divergence usually associated with a phase transition, probably caused by the pseudomagnetic field created by the curvature. This could be the first case of a phase transition in graphene nanostructures without the presence of external electric or magnetic fields.

Gaussian Curvature Effects on Graphene Quantum Dots.

In the last few years, much attention has been paid to the exotic properties that graphene nanostructures exhibit, especially those emerging upon deforming the material. Here we present a study of the mechanical and electronic properties of bent hexagonal graphene quantum dots employing density functional theory. We explore three different kinds of surfaces with Gaussian curvature exhibiting different shapes-spherical, cylindrical, and one-sheet hyperboloid-used to bend the material, and several boundary conditions regarding what atoms are forced to lay on the chosen surface. In each case, we study the curvature energy and two quantum regeneration times (classic and revival) for different values of the curvature radius. A strong correlation between Gaussian curvature and these regeneration times is found, and a special divergence is observed for the revival time for the hyperboloid case, probably related to the pseudo-magnetic field generated by this curvature being capable of causing a phase transition.

Prevalence and risk factors for colorectal adenomas in patients with ulcerative colitis.

BACKGROUND: Patients with ulcerative colitis (UC) have an increased risk of colorectal cancer. Scarce data regarding the development of adenomas in these patients are available both for normal and colitic mucosa. OBJECTIVE: The objective of this article is to evaluate the prevalence of adenomatous polyps and associated risk factors in patients with UC. METHODS: Patients with UC were identified from the databases of two tertiary referral centers. Medical, endoscopic and histologic reports were reviewed. RESULTS: A total of 403 patients were included (53% male; 33% extensive colitis) and 1065 colonoscopies (median per patient, 2) were recorded and analyzed. Seventy-four adenomas in 47 patients (11.7%) and three cases of colorectal cancer were found during a median follow-up of 6.3 years. The cumulative risk of colorectal adenoma was 4.7%, 16.7%, 23.6% and 34.4% at 10, 20, 30 and 40 years from UC diagnosis, respectively. The cumulative risk of developing metachronous colorectal adenoma was 66.7%, 87.9%, and 90.9% at 5, 10, and 15 years from first adenoma detection. Older age at UC diagnosis and longer disease duration were independent risk factors for colorectal adenoma development. CONCLUSIONS: The prevalence of colorectal adenomas among UC patients seems to be higher than previously reported, although lower than in the background population.

Fecal Calprotectin Levels Are Closely Correlated with the Absence of Relevant Mucosal Lesions in Postoperative Crohn's Disease.

BACKGROUND: Fecal calprotectin (FC) is the best noninvasive biomarker of disease activity in inflammatory bowel disease. Its correlation with endoscopic mucosal lesions could save inconvenient, expensive, and repeated endoscopic examinations in particular clinical settings. PATIENTS AND METHODS: To assess the correlation between FC and the existence and severity of endoscopic postoperative recurrence (POR), a group of clinically stable outpatients with Crohn's disease for whom an ileocolonoscopy was routinely planned to assess POR were invited to collect a stool sample before starting bowel cleansing to measure FC. POR was graded by means of Rutgeerts endoscopic score. RESULTS: One hundred nineteen ileocolonoscopies were included, 42% with endoscopic POR. FC was significantly lower in the absence of endoscopic POR and in the absence of any endoscopic lesion. The area under the receiver operating characteristic curve was 0.76 (95% confidence interval, 0.68-0.85) for the diagnosis of the absence of lesions and 0.75 (95% confidence interval, 0.66-0.84) for endoscopic POR. Better sensitivity and negative predictive value were observed when combining FC and serum C-reactive protein (CRP), leading to a sensitivity of 82%, a specificity of 53%, and negative and positive predictive values of 81% and 54%, respectively, for the prediction of endoscopic POR with a combination of FC 100 µg/g and CRP 5 mg/L cutoff values. CONCLUSIONS: FC correlates closely with endoscopic POR in clinically stable postoperative patients with Crohn's disease and, when used in combination with CRP, might save endoscopic examinations and allow for a high-grade suspicion of endoscopic POR in the long-term monitoring of these patients.

IL-6, IL-10 and TNFα do not improve early detection of post-endoscopic retrograde cholangiopancreatography acute pancreatitis: a prospective cohort study.

The most reliable indicators for post-ERCP acute pancreatitis are elevated amylase levels and abdominal pain 24 hours after ERCP. As ERCP is often performed on an outpatient basis, earlier diagnosis is important. We aimed to identify early predictors of post-ERCP pancreatitis. We prospectively analyzed IL-6, IL-10, TNFα, CRP, amylase and lipase before and 4 hours after ERCP, and studied their association with abdominal pain. We included 510 patients. Post-ERCP pancreatitis occurred in 36 patients (7.1%). IL-6, IL-10, TNFα and CRP were not associated with post-ERCP pancreatitis. Levels of amylase and lipase were higher in patients with pancreatitis (522 U/L and 1808 U/L vs. 78 U/L and 61 U/L, respectively; p < 0.001). A cut-off of 218 U/L for amylase (x2.2 ULN) and 355 U/L for lipase (x6 ULN) had a negative predictive value of 99.2% and 99.5%, respectively. Amylase and lipase present a good correlation (Pearson coefficient 0.912). Among 342 (67.1%) patients without abdominal pain at 4 hours, post-ERCP pancreatitis was diagnosed in 8 (2.3%). Only 4 of these patients presented amylase or lipase > 3 ULN. Amylase and lipase were the only markers of post-ERCP pancreatitis 4 hours after the procedure.

Somatostatin for prevention of post-ERCP pancreatitis: a randomized, double-blind trial.

BACKGROUND AND STUDY AIMS: Meta-analyses suggest that an intravenous bolus or a high dose continuous infusion of somatostatin reduces the incidence of acute pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP). Clinical guidelines, however, do not recommend this prophylaxis. The aim of this randomized, double-blind clinical trial was to evaluate the effect of somatostatin on the incidence of post-ERCP pancreatitis. PATIENTS AND METHODS: Patients undergoing ERCP at a single center were randomized to either intravenous bolus of somatostatin followed by a short (4-hour) continuous infusion, or to a similar placebo regimen. The primary outcome was post-ERCP pancreatitis, defined as abdominal pain with an amylase level at least three times higher than the upper limit of normality 24 hours after the ERCP and requiring admission for at least 2 days. RESULTS: A total of 510 patients were enrolled (255 patients per group) and all completed follow-up. The main indications for ERCP were choledocholithiasis (62 %), and biliary malignant stricture (31 %). Post-ERCP pancreatitis occurred in 19 patients (7.5 %) in the somatostatin group and 17 patients (6.7 %) in the placebo group (relative risk [RR] 1.12, 95 % confidence interval [95 %CI] 0.59 - 2.1; P = 0.73). The number of cases of moderate or severe acute pancreatitis was similar in the somatostatin (2.4 %) and the placebo (3.5 %) groups (RR 0.67, 95 %CI 0.24 - 1.85, P = 0.43). No side effects were observed related to the use of somatostatin. CONCLUSIONS: Administration of an intravenous bolus of somatostatin followed by a short continuous infusion does not reduce the incidence of post-ERCP pancreatitis. Clinical Trials.gov number: NCT01060826.

Síndrome de Marcapaso en paciente con Síndrome de QT Prolongado / Pacemaker syndrome in long QT syndrome patient

El síndrome de marcapasos es generado por la desincronización de la actividad auricular con la ventricular durante el marcapaso ventricular VVI en pacientes portadores de enfermedad del nodo. La enfermedad evoluciona de meses hasta varios años después del implante del marcapaso, siendo más frecuente en pacientes adultos mayores. El único tratamiento es el implante de un electrodo auricular para una estimulación aurículo ventricular sincrónica. Se presenta el caso de una paciente diagnosticada con enfermedad del nodo sinusal asociada a un QT prolongado, a la cual se le implantó un marcapaso VVIR, luego de algunos meses comenzó a presentar síntomas de insuficiencia cardiaca,a los 3 años del implante presento un episodio sincopal,en cuya evaluación con Holter ECG se registró un episodio de una taquicardia ventricular no sostenida observándose la presencia de ondas P retrogradas tras cada estimulación ventricular con marcapasos. Se consideró la probabilidad de un síncope arrítmico, que se manejó con Amiodarona. Se diagnosticó síndrome de marcapaso, realizando un mejoramiento del marcapaso por un equipo bicameral, con lo cual todos los síntomas de insuficiencia cardiaca desaparecieron. No se repitió el evento sincopal y desde la época la paciente se maneja en una capacidad funcional normal.

Pacemaker syndrome is an entity generated by a desynchronization between the auricular and ventricular activity during the paced ventricleVVI in patients with node disease.This syndrome can develop in moths even years after the pacemaker implant, being more frequent in elderly patients. The only treatment is to implant an auricular electrode for a synchronic atrioventricular stimulation. It presents the case of a patient diagnosed with a sinus node disease associated to long QT, for this reason it was implanted a pacemaker VVIR, few months later the patient started to have symptoms of heart failure, three years after that presented a syncope episodes showed in a Holter ECG study that reported unsustainable ventricular tachycardia episode and retrograde P waves after every ventricular stimulation sent by the pacemaker. The probability of an arrhythmic syncope was considered treated with Amiodarona. Pacemaker syndrome was diagnosed, making an improvement by a dual chamber pacemaker and all symptoms of heart failure disappeared. Syncopal event was not repeated and from the time the patient is operated on a normal functional capacity.

Gastrointestinal safety of triflusal solution in healthy volunteers: a proof of concept endoscopic study.

PURPOSE: Triflusal is an antiplatelet agent that irreversibly acetylates cyclooxygenase isoform 1 (COX-1) and therefore inhibits thromboxane biosynthesis. It was initially marketed as capsules containing 300 mg of active substance. In 2006 a new 600 mg (10 ml) oral solution form of triflusal was authorized in Spain. The primary aim of this study was to compare the gastrointestinal safety of the new triflusal oral solution with triflusal capsules in healthy volunteers. METHODS: Sixty healthy subjects were randomly assigned, in a 2.5:2.5: 1 ratio, into one of three groups, with 25 subjects receiving one bottle of triflusal oral solution (600 mg) daily, 25 subjects receiving two triflusal capsules (600 mg) once daily, and ten subjects receiving two placebo capsules once daily, respectively, during 7 consecutive days. Gastroscopy was performed at baseline before the administration of study drugs and after 4-8 h of the last dose of study drugs. Effects on the esophagus, stomach, and duodenum were measured in accordance with a modified Lanza scale. RESULTS: No differences between groups were detected at baseline. After treatment, median global scores in the placebo, triflusal solution, and triflusal capsules groups were, respectively, 0, 1, and 3 (p = 0.003 for comparison between placebo and triflusal capsules and p = 0.042 for comparison between triflusal solution and triflusal capsules). There were no significant differences between the scores on the triflusal solution and placebo groups. All treatments were well tolerated. CONCLUSION: In healthy subjects, triflusal solution induced less endoscopically apparent gastrointestinal mucosal damage than triflusal capsules and did not induce more damage than the placebo in healthy volunteers.

NOTES-assisted transvaginal splenectomy: the next step in the minimally invasive approach to the spleen.

HYPOTHESIS: Natural orifice transluminal endoscopic surgery (NOTES) has marked yet another step forward in less-invasive surgical procedures. Access to solid organs located deep in the left hypochondrium can be difficult using this technique but the transvaginal approach with the patient positioned in full lateral decubitus may be an option. MATERIAL AND METHODS: We present the case of a 60-year-old woman with a symptomatic splenic polycystic tumor. The procedure was carried out by a multidisciplinary team using a standard flexible videogastroscope and endoscopic instruments. Transvaginal visualization of the spleen and standard dissection of attachments were feasible, and splenectomy was completed using transvaginal stapling of the splenic hilum. The organ was extracted transvaginally. RESULTS: The postoperative course was uneventful. The patient had minimal postoperative pain and minimal scars, and was discharged on the second postoperative day. CONCLUSIONS: Transvaginal access can be safely used for operative visualization, hilum transection, and spleen removal with conventional instrumentation, reducing parietal wall trauma to a minimum. The clinical, esthetic, and functional advantages require further analysis.

A randomized controlled trial comparing ligation and sclerotherapy as emergency endoscopic treatment added to somatostatin in acute variceal bleeding.

BACKGROUND/AIMS: The currently recommended treatment for acute variceal bleeding is the association of vasoactive drugs and endoscopic therapy. However, which emergency endoscopic treatment combines better with drugs has not been clarified. This study compares the efficacy and safety of variceal ligation and sclerotherapy as emergency endoscopic treatment added to somatostatin. METHODS: Patients admitted with acute gastrointestinal bleeding and with suspected cirrhosis received somatostatin infusion (for 5 days). Endoscopy was performed within 6h and those with esophageal variceal bleeding were randomized to receive either sclerotherapy (N=89) or ligation (N=90). RESULTS: Therapeutic failure occurred in 21 patients treated with sclerotherapy (24%) and in nine treated with ligation (10%) (RR=2.4, 95% CI=1.1-4.9). Failure to control bleeding occurred in 15% vs 4%, respectively (P=0.02). Treatment group, shock and HVPG >16 mmHg were independent predictors of failure. Side-effects occurred in 28% of patients receiving sclerotherapy vs 14% with ligation (RR=1.9, 95% CI=1.1-3.5), being serious in 13% vs 4% (P=0.04). Six-week survival probability without therapeutic failure was better with ligation (P=0.01). CONCLUSIONS: The use of variceal ligation instead of sclerotherapy as emergency endoscopic therapy added to somatostatin for the treatment of acute variceal bleeding significantly improves the efficacy and safety.

Disseminated retroperitoneal choriocarcinoma with open fistula to intestine. "Restitutio ad integrum" with chemotherapy alone.

We hereby present a clinical case of a germinal tumour with a pulmonary and retroperitoneal dissemination in form of a great adenopathic mass that fistulizes into the duodenum, that obtained a complete resolution with chemotherapy.

Pharmacologic treatment of portal hypertension in the prevention of community-acquired spontaneous bacterial peritonitis.

INTRODUCTION: Given that beta-blockers reduce the incidence of bacterial translocation in cirrhotic rats, the aim of this study was to compare the long-term incidence of spontaneous bacterial peritonitis in cirrhotic patients submitted to pharmacologic versus endoscopic treatment to prevent variceal rebleeding. PATIENTS AND METHODS: Two hundred and thirty patients with variceal hemorrhage were included in two previous randomized trials performed to compare the efficacy of medication (nadolol plus isosorbide mononitrate, n=115) versus endoscopic treatment (n=115) with sclerotherapy or ligation for the prevention of rebleeding. RESULTS: The mean follow-up was 23+/-1.4 months. The characteristics of the patients and the number of patients on long-term prophylaxis with norfloxacin were similar in both groups. The incidence of spontaneous bacterial peritonitis was lower in the medication group (9 versus 14.7%, P=NS). The probability of spontaneous bacterial peritonitis was also lower in the medication group (6 versus 12% at 1 year, 22 versus 36% at 5 years; P=0.08), due to a significantly lower probability of community-acquired spontaneous bacterial peritonitis in this group (1 versus 10% at 1 year, 18 versus 32% at 5 years; P=0.02). Patients with no hemodynamic response to therapy had a significantly higher probability to develop community-acquired spontaneous bacterial peritonitis during follow-up than hemodynamic responders (P<0.03). Long-term probability of developing community-acquired spontaneous bacterial peritonitis is lower in patients submitted to pharmacologic treatment for preventing variceal rebleeding than in those submitted to endoscopic treatment. CONCLUSION: Long-term pharmacologic prophylaxis of variceal rebleeding contributes to the prevention of community-acquired spontaneous bacterial peritonitis.

Minimally invasive treatment for obstructive tumors of the left colon: endoluminal self-expanding metal stent and laparoscopic colectomy. Preliminary results.

BACKGROUND: Obstruction of the left colon may be the first manifestation of colorectal cancer. Resection of the colonic segment involved and the construction of an end colostomy (Hartman's procedure) is the most frequent treatment. Alternatives to the placement of a stoma are subtotal colectomy or intraoperative lavage of the colon and primary anastomosis, but their application depends on intraoperative findings and the availability of a skilled surgeon. The use of an expandable stent (SEMS) can enhance the feasibility of laparoscopic colectomy, avoiding the need for a colostomy and offering the advantages of a combination of two minimally invasive procedures. STUDY DESIGN: Between 1997 and 2004, an SEMS was placed in 11 cases of left colonic obstruction due to cancer, the obstruction being successfully resolved in each case. Seven patients were approached by laparoscopy to attempt the definitive colectomy. We evaluated the location and pathological characteristics of the tumor, effectiveness and complications of SEMS insertion, time interval between the insertion of SEMS and laparoscopic surgery, and postoperative data. RESULTS: The tumors were situated in the recto-sigma (1 case), sigma (3 cases) and descending colon (3 cases). Immediate relief of the obstruction was achieved in all cases after SEMS insertion of the stent, and oral diet was started at 24 h. The 7 patients were operated on an average of 8 days (range 6-14) after insertion of the stent. Conversion to open surgery was necessary in one case for reasons not related to the stent. CONCLUSIONS: Preliminary results of the combination of SEMS and elective laparoscopic surgery demonstrate that the procedure is feasible and that it presents all the clinical advantages of a minimally invasive approach. The procedure is a valid alternative to traditional major urgent surgery.

Tratamiento mínimamente invasivo de la neoplasia oclusiva del colon izquierdo: prótesis endoluminal autoexpandible y colectomía laparoscópica. Resultados preliminares / Minimally invasive treatment of malignant obstruction of the left colon: self-expandable endoluminal stent and laparoscopic colectomy. Preliminary results

Introducción. El tratamiento de la oclusión por cáncer más ampliamente utilizado consiste en la resección del segmento cólico y la realización de una colostomía terminal (operación de Hartmann). Las alternativas técnicas para evitar la realización de un estoma son la colectomía subtotal o colectomía segmentaria con lavado intraoperatorio pero, aunque existen muchos argumentos a favor de la cirugía en un tiempo, ésta es posible en menos del 70 por ciento de los casos. Otra opción técnica a esta intervención consiste en la colocación de una endoprótesis autoexpandible, con finalidad paliativa definitiva, o como paso previo a la colectomía electiva convencional. Ello permite obviar la realización de una colostomía. Por otra parte, la posibilidad de efectuar la colectomía laparoscópica permite asociar un abordaje mínimamente invasivo, con las consecuentes ventajas de bienestar para el paciente. Pacientes y método. De la base de datos prospectiva de 250 pacientes con patología colorrectal intervenidos por laparoscopia en nuestro servicio, hemos revisado los resultados obtenidos en los 5 pacientes a los que previamente se les había colocado una endoprótesis para solucionar una obstrucción completa por cáncer de colon izquierdo. Se han recogido los datos demográficos, las características del tumor, los datos referentes a la colocación de la endoprótesis y a la cirugía laparoscópica, así como la evolución postoperatoria. Resultados. Las lesiones se localizaron en el rectosigma (un caso), en el sigma (2 casos) y en el colon descendente (2 casos). La endoprótesis solucionó el cuadro oclusivo en los 5 pacientes con tolerancia a la dieta oral a las 24 h de su colocación. Un paciente presentó un episodio de rectorragia leve que se autolimitó sin necesidad de transfusión. Los 5 pacientes fueron intervenidos a los 8 días (rango, 6-14 días) tras la colocación de la prótesis. En un paciente fue necesaria la conversión a cirugía abierta y en otro a cirugía laparoscópica asistida con la mano. La causa de conversión en ningún caso se debió a dificultades relacionadas con la endoprótesis. Conclusiones. Los resultados preliminares de la combinación stent-cirugía electiva refuerzan las ventajas de esta opción, especialmente si se lleva a cabo la utilización secuencial de dos técnicas mínimamente invasivas (stent y colectomía laparoscópica), que permite obviar la necesidad de un estoma y ofrece las ventajas clínicas del abordaje laparoscópico (AU)