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Background Hepatic artery thrombosis is one of the most serious complications after liver transplant. Our objective is to evaluate the impact of arterial thrombosis on the postoperative evolution of a series of patients who received transplants because of hepatocellular carcinoma. Methods A retrospective study of 100 consecutive hepatocellular carcinoma liver transplants was performed from January 2011 to November 2017. Results Of the 100 transplant recipients, we have observed hepatic artery thrombosis in 4 of them, 3 premature and 1 delayed. All of them received retransplants after diagnosis by hepatic artery ultrasonography and arteriography. The descriptive analysis showed a significant relationship between the appearance of hepatic artery thrombosis with variables of postoperative severity, such as arrhythmias, atelectasis, pleural effusion, hemodialysis requirement, acute kidney failure, and respiratory failure. Although patients with hepatic artery thrombosis had a longer mean hospital stay, this was not statistically significant. There was decreased graft survival and overall survival of patients who experienced hepatic artery thrombosis. Conclusion Although the incidence of hepatic artery thrombosis has been relatively low (4%), the early detection of risk factors, such as arterial anatomic anomalies that condition a complex anastomosis, should draw our attention, thus having at our disposal strict ultrasonography and arteriography surveillance protocols as well as prophylactic anticoagulation guidelines for receptors at risk.

As the popularity of solar panels increases, significant research is being performed on maximizing the power extracted from photovoltaic systems. A phenomenon known as partial shading is a major source of power losses for photovoltaic plants. One way to reduce the effects of partial shading conditions is by using bypass–diodes. Typically any number of series and parallel–connected photovoltaic cells, known as photovoltaic cell arrays, are connected in anti–parallel with bypass–diodes. Due to this, it is advantageous to have an equivalent model for a photovoltaic cell array that is connected to bypass–diodes. In order to accurately develop this model, it is necessary to consider both series and parallel configurations of bypass–diodes, as well as the thermal behavior of bypass–diodes. The bypass–diode’s temperature model must be comprised of the constantly changing dissipated power, the effects of wind speed and the ambient temperature. This paper constructs an electro–thermal modular model for any size photovoltaic system and includes the effects of both the photovoltaic cells and bypass–diodes. A detailed analysis of the proposed model is performed and is then validated in both PSCAD/EMTDC and Matlab–Simscape. The proposed model is then further validated by the use of real measurements of ambient temperature, cell temperature, wind speed and then finally by a performance analysis of several maximum–power–point–tracking algorithms.

This manuscript presents the numerical optimization (through a mathematical model and an evolutionary algorithm) of the voltage-doubler boost converter, also called the series-capacitor boost converter. The circuit is driven by two transistors, each of them activated according to a switching signal. In the former operation, switching signals have an algebraic dependence from each other. This article proposes a new method to operate the converter. The proposed process reduces the input current ripple without changing any converter model parameter, only the driving signals. In the proposed operation, switching signals of transistors are independent of each other, providing an extra degree of freedom, but on the other hand, this produces an infinite number of possible combinations of duty cycles (the main parameter of switching signals) to achieve the desired voltage gain. In other words, this leads to a problem with infinite possible solutions. The proposed method utilizes an evolutionary algorithm to determine the switching functions and, at the same time, to minimize the input current ripple of the converter. A comparison made between the former and the proposed operation shows that the proposed process achieves a lower input current ripple while achieving the desired voltage gain.

Power-electronics based converters are essential circuits in renewable energy applications such as electricity generated with photovoltaic panels. The research on the field is getting increasing attention due to climate change problems and their possible attenuation with the use of renewable energy. Mathematical models of the converters are being used to optimize several aspects of their operation. This article is dedicated to optimizing (through the mathematical model and an evolutionary algorithm) the operation of a state-of-the-art converter. The converter, which is composed of two parts or phases, is controlled by pulse width modulation with two switching signals (one for each phase). The converter provides by itself low switching ripple in both the output voltage and the input current, which is beneficial for renewable energy applications. In the traditional operation, one of the switching signals has an algebraic dependence on the other one. This article proposes a new way to select the duty cycle for both signals. In the proposed method, duty cycles of both phases are considered independent of each other, this provides an extra degree of freedom, on the other hand, this produce that the possible combinations of duty cycles which produce a certain voltage gain is infinite, it becomes a problem with infinite possible solutions. The proposed method utilizes the a linear success-history based adaptive differential evolution with linear population reduction, also called L-SHADE algorithm for simplicity, to find the two duty cycles that achieve the desired voltage gain and to minimize the converters switching ripple. The obtained results are compared with the former operation of the converter, the proposed operation achieves a lower output voltage ripple while achieving the desired operation (voltage gain).

Background Sarcopenia is defined as the loss of muscle mass and function. Our aim is to evaluate the degree of sarcopenia by measuring the patients on the waiting list for liver transplantation and its influence on the different post-liver transplant outcomes in our group. Methods The psoas muscle index (PMI, cm2/m2) was calculated (right psoas muscle area [cm2]/the square of the body height [m2]) in 57 patients on the waiting list for liver transplantation in our center, and the post-transplant variables relevant to our study were collected. Results The 57 recipients had a mean age of 57 years (range, 35-73) and had a mean of 7.4 months (range, 0-39) on the liver transplant waiting list. The mean psoas muscle index was 2.39 (range, 1-4), and the mean body mass index was 28.01kg/m2 (range, 22-36). After multivariate analysis we found a positive correlation between the PMI and the body mass index of the recipients (r = 0.320, P = .017), intensive care unit length of stay, and donor age (r = 0.319, P = .042), and between cold ischemia time and graft survival (r = 0.366, P = .009). We found no correlation in our sample between PMI and post–liver transplant complications either in terms of graft or patient survival. Conclusion PMI is not representative of total muscle mass and sarcopenia and is not effective in adequately predicting the survival of patients on the waiting list for liver transplantation.

A control approach developed in the α β0 reference frame must be able to track control signals which are sinusoidal functions of time. Therefore, designing these compensators is not a straightforward task. Alternatively, a control scheme elaborated in dq reference frame offers the possibility to track dc control signals. It also allows the design of compensators with simpler structures and low dynamic orders. The purpose of this work is to propose a control scheme in the dq reference frame for Hexverter-based systems. Considering the Hexverter's operating principle and its characteristic waveforms, a frequency decoupled branch current control model in the dq reference frame is synthesized. It can be considered as an extension of the control model developed for the two-level voltage source inverter. A feature of the proposed control is to allow independent regulation of the Hexverter's active and reactive power flows. The former control is then integrated to a modulator and a voltage balancing algorithm when the Hexverter-based system is functioning as an intertie. The effectiveness of the characterized system is validated via a detailed PSCAD/EMTDC computer simulation.

The study aim is to analyze the evolution over the last 25 years of the results reported after abdominal oncological surgery in patients aged 80 years of age and older. The primary endpoint was morbidity and mortality in this group of patients; the secondary endpoint was overall survival.A systematic search strategy was used to browse through Medline/PubMed, EMBASE, Scopus, ClinicalTrials.gov, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials using a combination of standardized index terms. Studies published between 1997 and 2017 were selected. Only those studies that showed morbidity and mortality after digestive and hepatobiliary tract oncological surgery in individuals aged 80 years and older were included. The PROSPERO registration number is CRD42018087921. PRISMA and MOOSE guidelines were applied.A total of 79 studies were included, categorized by origin of malignancy: esophageal (7), stomach (26), liver (4), pancreas (19), and colorectal (23). Compared with the non-elderly group, the elderly group had similar esophageal morbidity with higher mortality (RR 2.51, 1.50 to 4.21; P = 0.0005); higher gastric morbidity (RR 1.25, 1.09 to 1.43; P = 0.001), and mortality (RR 2.51, 1.81 to 3.49; P = 0.0001); similar liver morbidity and mortality; higher pancreatic morbidity (RR 1.17, 1.03 to 1.33; P = 0.02) and mortality (RR 2.37, 1.86 to 3.03; P 0.00001); and similar colorectal morbidity with higher mortality (RR 4.44, 1.91 to 10.32; P = 0.005).Oncological surgery of most abdominal visceral tumors is associated with increased morbidity and mortality in patients older than 80 years.

In this work two different modulation strategies termed: i) nearest level control, and ii) phase disposition– sinusoidal pulse width modulation, are described, simulated and compared when applied to a Hexverter–based modular multilevel converter. In addition, two different voltage balancing algorithms are implemented and evaluated. Furthermore, total harmonic distortion regarding three–phase system voltages are assessed. In the end, synthesized branch voltage spectrum for each modulation strategy is analyzed.

Heat stroke is a condition caused by an excessive increase in body temperature in a relatively short period of time, and is clinically characterized by central nervous system dysfunction, including delirium, seizures, coma, and severe hyperthermia. In this context, the resulting fulminant hepatic failure makes liver transplant the best choice when there are no guarantees of better results with conservative treatment. We present our experience in this case, possible alternative choices, and the current role of liver transplantation in the resolution of fulminant liver failure due to heat stroke. Case Report We report the case of a 32-year-old man with a history of malabsorption syndrome and unconfirmed celiac disease controlled with a gluten-free diet, who, while working on a typical summer midday in southern Spain (approximately 40°C), abruptly presented with loss of consciousness, coma, and a temperature of 42°C, as well as seizures at the initial medical assessment that subsided after the administration of diazepam. On the third day, the patient presented with multiple organ dysfunction syndrome, requiring mechanical ventilation, hemodialysis, and inotropic support. He did not improve with the support of conservative treatment, therefore it was decided to perform an urgent liver transplant, after which he recovered completely. Conclusions Liver transplantation should be a main choice of treatment for cases in which, despite intensive medical treatment, there is still clinical and analytical evidence of massive and/or irreversible hepatocellular damage.

This paper exhibits the performance of a high step-up converter employed for maximum power extraction in a photovoltaic system. The proposed converter is conformed by a conventional boost followed by a diode-capacitor-based multiplier for increasing the nominal voltage gain of the boost converter, resulting in a lower duty cycle at the maximum power point. The main characteristics of the converters are analyzed in order to determine an optimal equivalent input impedance. Evaluation of the proposed converter using standard Perturb and Observe algorithm is carried out. Switching simulations evidence the good performance of the whole system under irradiance disturbances.

This paper will analyze the power quality of multilevel voltage waveforms generated using three modulation strategies: i) a conventional nearest level control (NLC) strategy, ii) NLC with harmonic elimination, and iii) optimized selective harmonic elimination (OSHE). A uniform sampling frequency of the sinusoidal voltage is considered for NLC modulation. It is found in all selected experimental results that the power quality obtained employing OSHE is higher than the other two modulation techniques.

Introduction Right hepatic artery (RHA) injury after laparoscopic cholecystectomy (LC) may go unnoticed clinically, but can sometimes cause necrosis of the right lobe. Exceptionally, when the necrosis spreads to segment IV, fulminant liver failure (FLF) may occur, and an urgent liver transplantation (LT) may be required. Patients and method We provide a review of the literature on patients with indication for an LT due to vascular damage caused by bile duct injury following LC. The case reported herein is the fourth described in the specialized literature of LT due to RHA injury after LC and the second of FLF after RHA injury. Results LT due to RHA injury was performed in 3 of 13 patients reported in the literature: one LT was performed at 3 months due to FLF, after an extended right hepatectomy was performed, and the remaining two were performed due to secondary biliary cirrhosis. Our patient was transplanted due to FLF 15 days after the injury. Conclusions RHA injury after LC may require LT due to FLF. Although exceptional, this possibility should be considered when there are RHA complications that may require occlusion.

The best treatment for hepatocellular carcinoma (HCC) associated with liver cirrhosis is liver transplantation and the best results are obtained when the tumors fulfill the Milan criteria. However, although the number of transplants is increasing, the organ deficit is growing, which lengthens time on the waiting list, increasing the risk of tumor progression of and exclusion from the list. The use of elderly donors is a valid option for patients on the transplant waiting list with HCC, reducing time on the waiting list. We report our experience with patients transplanted for HCC associated with hepatic cirrhosis using livers from donors >75 years of age. Our preliminary results supported the use of elderly suboptimal donors making it possible to give priority to these patients. All patients in the series achieved good graft function after a follow-up of 2 years with a 100% disease-free survival rate. More extensive long-term studies are needed to confirm these findings.

The aim of the present study was to describe the incidence and microbiological profiles of positive cultures obtained from preservation solution (PS) and correlate these findings with infectious complications detected in the liver transplant (LT) recipient.We conducted a single-center, retrospective study between December 2010 and August 2014 among 178 LT. In all grafts, a PS culture was carried out. All the infections in the receipt until hospital discharge were collected. In patients with1, infection was considered the most severe according to Clavien-Dindo classification.PS culture was positive for bacterial or fungal agents in 79 of 178 LT recipients (44%). The most commonly cultured organisms were coagulase-negative staphylococci (64%), Enterobacteriaceae (17%), and Staphylococcus aureus (4.7%). In the 79 patients with positive PS, 49 blood cultures were requested in the period after LT. Twenty-five postoperative infections (31.7%) were diagnosed. Only 4 of 79 patients (5%) with PS contamination had a postoperative infections related with isolated microorganism.Contamination of PS appears in a high percentage of liver grafts before LT, although there is a poor correlation with postoperative infections in LT recipient. In these patients, a standardized process including fungal and bacterial cultures could be useful.

Introduccion El tratamiento medico del fracaso hepatico fulminante busca la recuperacion espontanea de la funcion hepatica, pero sus resultados son muy desalentadores (mortalidad del 50-80%). El trasplante hepatico es una opcion en los pacientes con mala evolucion a pesar del tratamiento medico, con una supervivencia superior al 50%. El momento idoneo para efectuar el trasplante es discutido, pues no debe hacerse ni demasiado pronto, cuando la enfermedad hepatica aun es reversible, ni demasiado tarde, cuando el paciente se encuentra en una situacion clinica irreversible. Pacientes y Metodo Se revisaron de forma retrospectiva las historias clinicas de 34 pacientes ingresados en nuestro hospital con el diagnostico de fracaso hepatico fulminante, de los que 26 fueron sometidos a trasplante. La causa mas frecuente fue la viral con 10 casos (38%), sin que se pudiera establecer etiologia alguna en 11 casos (42%). Trece pacientes presentaron complicaciones preoperatorias, la mas frecuente de las cuales fue la insuficiencia renal. Segun el grado de compatibilidad ABO/DR, fueron identicos en 13 casos (40%), compatibles en 17 (51%) e incompatibles en los 3 casos restantes (9%). Resultados Se efectuaron 33 trasplantes en 26 pacientes: 4 fueron retrasplantados por rechazo cronico, dos por fallo primario del injerto y un caso por rechazo hiperagudo. La mortalidad global fue del 46% (12 pacientes), y la causa mas frecuente de fallecimiento fue la infecciosa (50%). La supervivencia actuarial global fue del 68% al ano, del 63% a los 3 anos y del 59% a los 5 anos. Los factores de mal pronostico fueron la insuficiencia renal y respiratoria, el electroencefalograma grado D y los grados de encefalopatia III y IV; este ultimo fue el unico factor pronostico segun el analisis multivariante. Los factores pronosticos de mortalidad fueron los hallazgos de un electroencefalograma grado D, los grados de encefalopatia III y IV y la insuficiencia respiratoria; este ultimo fue el unico factor pronostico segun el analisis multivariante. Conclusiones La obtencion de buenos resultados con el empleo del trasplante en el abordaje del fracaso hepatico fulminante depende de una optima seleccion de los candidatos a trasplante, lo que implica la identificacion temprana de los mismos, esto es, precocidad en la indicacion del trasplante, reduccion del tiempo medio de espera y exclusion de aquellos con factores de mal pronostico.

Resumen Introduccion La colecistectomia realizada por via laparoscopica se acompana de una incidencia de lesiones iatrogonicas de la via biliar principal mayor que cuando se realiza por via abierta. Estas lesiones son mas graves, al ser mas altas en su localizacion, afectando a la via biliar intrahepatica y con frecuente desaparicion de tramos completos de la misma, lo que dificulta su diagnostico y tratamiento quirurgico. Pacientes y metodo Se presentan 10 casos de lesiones iatrogenicas de la via biliar principal tras colecistectomia laparoscopica intervenidos en nuestro servicio, tres de ellos con afectacion de la via biliar intrahepatica. En los 7 casos de localizacion extrahepatica se practico una hepaticoyeyunostomia en “Y” de Roux en 4 casos, una coledococoledocostomia terminoterminal sobre tubo en “T” de Kehr en otros 2 casos (en ambos hubo que realizar posteriormente una hepaticoyeyunostomia en “Y” de Roux) y, en el restante, un cierre de una seccion parcial del coledoco sobre un tubo en “T” de Kehr. En los 3 casos de lesion intrahepatica fracaso una primera reconstruccion en “Y” de Roux, precisando un abordaje intrahepatico con tutores multiples y nueva hepaticoyeyunostomia en “Y” de Roux. Resultados Todos los enfermos se encuentran asintomaticos y con unas analiticas normales tras un seguimiento medio de 39,2 meses. Conclusion Las lesiones iatrogenicas de la via biliar principal tras colecistectomia laparoscopica pueden requerir cirugia compleja para su tratamiento, por lo que deben ser referidas a centros con experiencia experiencia en cirugia hepatobiliar, sobre todo si son de localizacion intrahepatica.

Resumen Objetivos La aparicion de seromas axilares es la complicacion mas frecuente tras la linfadenectomia axilar. En este trabajo estudiamos algunos parametros relacionados con el uso de drenajes quirurgicos que podrian resultar predictivos del desarrollo de dichos seromas. Pacientes y metodo Se han estudiado, de forma prospectiva, 100 pacientes intervenidas de manera consecutiva por cancer de mama y en las que se realizo linfadenectomia axilar de los tres niveles como parte de su tratamiento. En todas se coloco en la intervencion un drenaje axilar, y se registraron datos sobre el debito y duracion de dicho drenaje en el postoperatorio. Estos parametros se compararon segun desarrollaran las pacientes seromas que precisasen punciones evacuadoras. Resultados Solo se encontraron diferencias significativas en el debito medio de los tres ultimos dias de drenaje, encontrandose una relacion entre el desarrollo de seromas y mas de 50 ml del citado debito. No encontramos diferencias en el resto de parametros, incluyendo la tecnica utilizada. Conclusiones La retirada del drenaje axilar cuando el debito medio de los tres ultimos dias es menor de 50 ml, es una medida eficaz a la hora de tratar de evitar el desarrollo de seromas axilares postoperatorios tras linfadenectomias por cancer de mama.

Introduccion y Objetivo El carcinoma de vesicula es la lesion maligna mas frecuente del tracto biliar. Sin embargo, la supervivencia a los 5 anos es inferior al 5%. El objetivo de este estudio es analizar la influencia de varias variables clinicopatologicas en la supervivencia en una serie de 226 pacientes con carcinoma de vesicula. Pacientes y Metodos Los resultados son analizados retrospectivamente y los factores pronosticos son identificados mediante un analisis estadistico univariante y un modelo de regresion de Cox. Todos los pacientes fueron intervenidos y se realizo una intervencion quirurgica potencialmente curativa en 67 casos (29,6%). En 63 pacientes (27,9%) el diagnostico fue incidental al estudiar una vesicula extirpada por un proceso patologico benigno. El estadio TNM fue 0 en 7 casos (3,1%), I en 19 casos (8,4%), II en 21 casos (9,3%), III en 61 casos (27%) y IV en 118 casos (52,2%). Resultados La supervivencia global a los 5 anos fue del 17,3%. En el analisis univariante, las variables con influencia significativa fueron la presencia de ictericia, la perdida de peso, la palpacion de una tumoracion abdominal, el momento del diagnostico, la tecnica quirurgica, el sistema de estadificacion TNM y las tres variables de dicho sistema (T: tamano, N: adenopatias, M: metastasis a distancia). En el analisis multivariante tuvieron una asociacion significativa con la supervivencia las tres variables del sistema TNM y la tecnica quirurgica. Conclusiones El factor pronostico mas importante es la estadificacion TNM del tumor y, actualmente, con la realizacion de la colecistectomia radical en los estadios II y III, la tecnica quirurgica se ha convertido en el otro factor pronostico importante.