Esophageal melanoma: a systematic review and exploratory recurrence and survival analysis.

Esophageal melanoma is a rare and poorly described malignancy. We sought to review all available data on the clinicopathological features, management options, and outcomes of patients with esophageal melanoma to guide clinicians working to treat these uncommon tumors. A systematic literature search of the PubMed, Embase, and Cochrane databases was performed. Exploratory recurrence and survival analyses were performed using previously-validated pooled Cox and logistic regression techniques for case reports and case series. Quality assessment of included studies was performed using the tools developed by the Joanna Briggs and the National Heart, Lung, and Blood Institutes. Fifty-nine studies were reviewed. A total of 93 patients with esophageal melanoma were identified. The mean patient age was 61.2 ± 10.6 years. Esophageal melanoma usually developed at the lower esophagus (48.4%). 90.3% of the patients were symptomatic at presentation, with dysphagia being the most common symptom (72%). Esophagectomy was performed in 91.4% of the patients. Postoperatively, 14 patients (15.1%) received adjuvant chemotherapy. Tumor recurrence was seen in 37 patients (39.8%). The median time to recurrence was 6 months. Disease-specific mortality was 43%. All-cause mortality was 46.1%. On multivariable Cox regression, older patient age (hazard ratio [HR] = 0.91, P = 0.008) and higher Melan-A expression (HR = 0.21; P = 0.029) were associated with a significantly lower risk of mortality. Higher S100 levels (HR = 37.4; P = 0.001) were predictive of poor survival. On logistic regression, large, ulcerated, lower esophageal tumors were significantly more likely to recur (P = 0.018, P = 0.013, and P = 0.027 respectively). Esophageal melanoma is a rare malignancy that tends to present with dysphagia. Most surgically-treated patients undergo esophagectomy. Large, ulcerated, lower esophageal lesions recur more frequently. Immunohistochemistry provides prognostic information regarding survival.

Multiscale simulations of PS-SiO2 nanocomposites: from melt to glassy state.

The interaction energetics, molecular packing, entanglement network properties, segmental dynamics, and elastic constants of atactic polystyrene-amorphous silica nanocomposites in the molten and the glassy state are studied via molecular simulations using two interconnected levels of representation: (a) a coarse-grained one, wherein each polystyrene repeat unit is mapped onto a single "superatom" and the silica nanoparticle is viewed as a solid sphere. Equilibration at all length scales at this level is achieved via connectivity-altering Monte Carlo simulations. (b) A united-atom (UA) level, wherein the polymer chains are represented in terms of a united-atom forcefield and the silica nanoparticle is represented in terms of a simplified, fully atomistic model. Initial configurations for UA molecular dynamics (MD) simulations are obtained by reverse mapping well-equilibrated coarse-grained configurations. By analysing microcanonical UA MD trajectories, the polymer density profile is studied and the polymer is found to exhibit layering in the vicinity of the nanoparticle surface. An estimate of the enthalpy of mixing between polymer and nanoparticles, derived from the UA simulations, compares favourably against available experimental values. The dynamical behaviour of polystyrene (in neat and filled melt systems) is characterized in terms of bond orientation and dihedral angle time autocorrelation functions. At low concentration in the molten polymer matrix, silica nanoparticles are found to cause a slight deceleration of the segmental dynamics close to their surface compared to the bulk polymer. Well-equilibrated coarse-grained long-chain configurations are reduced to entanglement networks via topological analysis with the CReTA algorithm, yielding a slightly lower density of entanglements in the filled than in the neat systems. UA melt configurations are glassified by MD cooling. The elastic moduli of the resulting glassy nanocomposites are computed through an analysis of strain fluctuations in the undeformed state and through explicit mechanical deformation by MD, showing a stiffening of the polymer in the presence of nanoparticles. UA simulation results for the elastic constants are compared to continuum micromechanical calculations invoked in homogenization models of the overall mechanical behaviour of heterogeneous materials. They can be interpreted in terms of the presence of an "interphase" of approximate thickness 2 nm around the nanoparticles, with elastic constants intermediate between those of the filler and the matrix.

Effect of Surface Nanopatterning on Slip: The Case of Couette Flow of Long-Chain Polyethylene Melt Flowing Past Gold Surfaces.

The manifestation of slip during flow of a polymer melt past a solid surface depends on several parameters, such as film thickness, the strength of polymer-solid interactions compared to the cohesive energy of the polymer, and the roughness of the surface. Understanding the role of these molecular aspects for slip is crucial in microfluidics, friction-tuning, polymer extrusion, and nanocomposites applications. The present article investigates the effect of surface nanopatterning on slip, via Couette-flow simulations of long chain polyethylene melts past nanopatterned gold surfaces. Slip is quantified in terms of the true and effective slip velocity, and the slip length. When polymer chains are adsorbed to surfaces with periodic features (e.g., crystal planes), they develop preferential ordering in a way that enables them to minimize their free energy. The orientation of a chain is affected by that of its neighbors; thus, when several chains come together, they are prone to form regions with crystal-like orientation. We show that, in some cases, the introduction of nanopatterns on the surface can perturb and induce reorganization of these regions, and in turn affect slip. The nanopatterns are realized as periodic defect stripes of variable width, depth, areal density, and orientation angle. In situations in which the width of the defects becomes comparable to the diameter of individual chain backbones, slip is minimized (stick conditions). Cutting the nanopatterns in low symmetry directions can affect the quality of their edges and lead to enhanced friction. To characterize these edges we have devised a scheme for the quantification of the mean square roughness and mean position of the surface, which is general and applicable in 2 and 3 dimensions for any kind of material, either crystalline of amorphous. Applying the patterns on the opposing solid surfaces in a symmetric or antisymmetric manner has a profound effect on flow. We show that the application of nanopatterns in symmetric configurations generates zero net flow and induces additional shear along directions normal to the direction of the flow. The application of symmetry-breaking configurations can guide flow toward preferential directions, a result with possible applications in microfluidic devices.

Preoperative levosimendan in heart failure patients undergoing noncardiac surgery.

BACKGROUND: Heart failure (HF) is a major cause of perioperative morbidity and mortality in noncardiac surgery. Preoperative optimisation of these patients is, thus, of utmost importance. Levosimendan seems promising for patients undergoing cardiac surgery; however, its safety and efficacy in HF patients undergoing noncardiac surgery have not been evaluated. OBJECTIVE: To evaluate the effects of prophylactic preoperative levosimendan administration on left ventricular function in HF patients undergoing noncardiac surgery. METHODS: HF patients with ejection fraction <30%undergoing elective noncardiac surgery in 2005 were included in this prospective study. Patients were admitted to our surgical intensive care unit one day preoperatively. Under continuous haemodynamic monitoring, the treatment protocol consisted of an initial loading dose (24 microg/kg) for ten minutes followed by a continuous 24-hour infusion (0.1 microg/kg/min) at the end of which patients underwent surgery. Echocardiography was performed before infusion (day 0) and on the 7th postinfusion day (day 7). Measurements included left ventricular ejection fraction (LVEF), velocity time integral(VTI), pre-ejection period (PEP), ejection time (ET),maximum (Pmax) and minimum P(min) transvalvular aortic pressure gradient, and maximum (Vmax) and minimum V(min) aortic velocity. RESULTS: Twelve consecutive patients were enrolled. Levosimendan resulted in a significant increase in LVEF,VTI, P(max), P(min), V(max), and V(min) (p<0.01) and, moreover, a significant reduction in PEP, ET, and PEP/ET (p=0.04) on day 7 compared with day 0 values. No adverse reactions,complications or mortality occurred during 30-day follow-up. CONCLUSION: Prophylactic preoperative levosimendan treatment may be safe and efficient for perioperative optimisation of heart failure patients undergoing noncardiac surgery.

Refractory septic shock: efficacy and safety of very high doses of norepinephrine.

The aim of this study was to evaluate the safety, efficacy, and effects of administration of very high doses of norepinephrine (> 4 microg kg(-1) min(-1)) in catecholamine-resistant septic shock. We reviewed the charts of all patients with nonresponding to commonly used norepinephrine doses (< or = 4 microg kg(-1) min(-1)) septic shock from January 1999 to December 2002 in our Surgical Intensive Care Unit. All patients were treated with high norepinephrine doses (> 4 microg kg(-1) min(-1)), after initial resuscitation, so as to achieve a mean arterial pressure higher than or equal to 65 mmHg. During this 4-year period, 12 consecutive patients with catecholamine-resistant septic shock were included in our study. When compared with the values obtained prior to the administration of very high norepinephrine doses, the values of mean arterial pressure (p = 0.003) and systemic vascular resistance (p = 0.002) significantly increased after the administration of such doses, and additionally, lactate concentrations (p = 0.003) decreased. In contrast, no significant changes were observed regarding mean central venous pressure, pulmonary capillary wedge pressure, and pulmonary arterial pressure. Administration of high norepinephrine doses in our patients resulted in a survival rate of 33.4%. Management of catecholamine-resistant septic shock patients poses a challenging problem. Administration of very high norepinephrine doses is safe and effective and may improve survival of these patients with otherwise extremely high mortality rates.

Pulsed-field gradient nuclear magnetic resonance study of transport properties of fluid catalytic cracking catalysts.

Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been applied to study molecular diffusion in industrial fluid catalytic cracking (FCC) catalysts and in USY zeolite for a broad range of molecular displacements and temperatures. The results of this study have been used to elucidate the relevance of molecular transport on various displacements for the rate of molecular exchange between catalyst particles and their surroundings. It turned out that this rate, which may determine the overall rate and selectivity of FCC process, is primarily related to the diffusion mode associated with displacements larger than the size of zeolite crystals located in the particles but smaller than the size of the particles. This conclusion has been confirmed by comparative studies of the catalytic performance of different FCC catalysts.

Postresectional pulmonary oxidative stress in lung cancer patients. The role of one-lung ventilation.

OBJECTIVE: The authors conducted a prospective analysis in order to investigate through lipid peroxidation metabolites the generation of oxygen free radicals after one-lung ventilation (OLV). METHODS: From 2001 to 2003, 212 patients were prospectively studied for lung reexpansion/reperfusion injury. They were classified in six groups. Group A, non-OLV lobectomy group; B, OLV pneumonectomy group; C-E, OLV lobectomy of 60, 90, and 120 min duration, respectively; F, normal subjects as baseline group. Preoperative, intraoperative and postoperative strict blood sampling protocol was followed. Malondialdehyde (MDA) plasma levels were measured. The recorded values were analyzed and statistically compared between groups and within each one. RESULTS: Comparison of groups C-E (OLV) to all other documented significant (P<0.001) increase of MDA levels during lung reexpansion and for the following 12h. The magnitude of oxidative stress was related to OLV duration (group E>D>C, all P<0.001). The removal of cancer-associated parenchyma led to MDA level decrease postoperatively (P<0.001) especially after pneumonectomy (A vs. B, P<0.001). CONCLUSIONS: (1) Lung reexpansion provoked severe oxidative stress. (2) The degree of the amount of generated oxygen free radicals was associated to the duration of OLV. (3) Patients with lung cancer had a higher production of oxygen free radicals than normal population. (4)Tumor resection removes a large oxidative burden from the organism. (5) Mechanical ventilation and surgical trauma are weak free radical generators. (6) Manipulated lung tissue is also a source of oxygen free radicals, not only intraoperatively but also for several hours later.

Penetrating injuries of the neck in patients in stable condition. Physical examination, angiography, or color flow Doppler imaging.

BACKGROUND: The initial assessment of penetrating injuries of the neck is controversial, with angiography remaining the gold standard for identifying vascular injuries. Recent reports suggest that physical examination might be an accurate way to evaluate these injuries. Color flow Doppler imaging has been used with promising results to assess extremity injuries, but the role of color flow Doppler imaging in neck injuries has not been studied. OBJECTIVE: To evaluate and compare the roles of physical examination, color flow Doppler imaging, and angiography in the identification and management of penetrating neck injuries. STUDY DESIGN: A prospective study of patients in stable condition with penetrating injuries of the neck. All study patients were examined according to a written clinical protocol and subsequently underwent angiography and color flow Doppler imaging. The sensitivity and specificity of physical examination and color flow Doppler imaging were compared with those of angiography. RESULTS: Eighty-two patients fulfilled the criteria for inclusion in the study. Angiography demonstrated vascular lesions in 11 patients (13.4%), but only two (2.4%) of them required treatment. Serious injuries were detected or suspected during physical examination, but six lesions not requiring treatment were missed. When injuries not requiring treatment were excluded, the sensitivity was 100% and the specificity was 91%. With color flow Doppler imaging, 10 of the 11 injuries were identified, for a sensitivity of 91% and a specificity of 98.6%. The sensitivity and specificity were 100% for clinically important lesions. CONCLUSION: The combination of a careful physical examination and color flow Doppler imaging provides a reliable way to assess penetrating neck trauma and may be a safe alternative to routine contrast angiography.

Quantitative computed tomography of spine: comparison of three-dimensional and two-dimensional imaging approaches in clinical practice.

Quantitative computed tomography (QCT), a widely utilized technique for determining bone mineral density (BMD) at various skeletal sites, may yield less precise measurements if there are operator measurement errors and other technical variables. Two-dimensional (2D)and three-dimensional (3D)QCT scans of the lumbar spine of 21 women were compared in order to investigate the effects of potential operator variability on the precision of BMD measurements and to examine resulting differences of these imaging approaches in clinical practice. No significant difference was found (p > 0.05) in precision between the 2D and 3D QCT BMD measurements owing to operator measurement errors on the CT scans. The variability in BMD values within numerous small regions of interest (ROIs)( approximately 75 mm (2) ) of cancellous bone within a single vertebra was 10.1%, larger than the 2D or 3D BMD variability measured in typical regions ( approximately 250 mm (2)) by an order of magnitude. 3D BMD values in this population, which represented a wide range of clinical values, were found to be significantly greater than 2D BMD values by an average of 5.6% (p = 0.00024) relative to the 2D QCT values. Our findings suggest technical measurement error does not have a significant effect on precision of BMD measurements obtained with either QCT method. Several factors, however, including the incorporation of focal regions of higher density bone mass within the 3D QCT ROI may account for the higher BMD values compared with those for 2D QCT.

Fetal death after trauma in pregnancy.

Trauma in pregnancy places the mother and fetus at risk. The objective of this study is to identify risk factors independently associated with acute termination of pregnancy and/or fetal mortality after trauma. The medical and trauma registry records of 80 injured pregnant patients were reviewed. Data were collected and then analyzed by univariate and multivariate analysis. Three patients died (3.7%), 23 had the pregnancy acutely terminated (30%), and 14 suffered fetal death (17.5%). The only independent risk factors for fetal mortality were an Injury Severity Score (ISS) > or =9 and a nonviable pregnancy (<23 weeks). The combination of both risk factors increased the likelihood of fetal mortality by fivefold over that of patients without either risk factor. Maternal hemodynamic parameters did not predict fetal loss. Two patients lost their fetuses despite insignificant trauma (ISS = 1) and normal hemodynamic parameters, whereas eight delivered normal babies despite major trauma (ISS > or = 16). Hemodynamic stability on admission does not predict fetal mortality. Although the presence of moderate to severe injuries (ISS > or = 9) increases the likelihood of fetal mortality, this complication may occur even with insignificant trauma. Close maternal and fetal monitoring is justified, regardless of maternal hemodynamic presentation or severity of injury.

Pharmacokinetics of aztreonam in critically ill surgical patients.

The pharmacokinetics of aztreonam in critically ill surgical patients with serious gram-negative infections were studied. Blood samples were taken before and at 30 minutes, 2.5 hours, and 5 hours after a dose of aztreonam 2 g i.v. every six hours. All patients had received at least two aztreonam doses before the dosage interval being studied. Aztreonam concentrations were measured by high-performance liquid chromatography. Aztreonam's pharmacokinetics, the severity of illness, and patient outcomes were examined. A total of 28 patients with 111 serum aztreonam concentrations were included in the analysis. The patients were young (mean age, 35 years) and predominantly male. The mean APACHE II score was 19.3, and 22 patients had sepsis. Four patients died. The mean volume of distribution (V) of 0.35 L/ kg was nearly twice the previously reported steady-state value for healthy volunteers (0.18 L/kg) and was highly variable. A slightly higher than normal mean V, 0.22 L/ kg, was seen in a subset of six patients whose infection occurred earlier in their intensive care and who had lower APACHE II scores. While with some antibiotics the elevated V would imply difficulty in achieving therapeutic drug levels, 99 (89%) of the 111 concentrations were at or above the in vitro susceptibility breakpoint of 8 micrograms/mL. Despite observations of markedly increased and highly variable V in critically ill surgical patients, a standard dosage of aztreonam was usually sufficient to maintain adequate serum drug levels.

MR imaging of the midfoot: normal anatomy with cadaveric correlation.

MR imaging has an invaluable role in the diagnosis of foot and ankle pathology. Analyzing abnormalities on MR images depends upon a thorough understanding of the normal anatomy. This article reviews the MR anatomy of the midfoot with cadaveric correlation.

Delayed diagnosis of primary non-Hodgkin's lymphoma of the sacrum.

Primary non-Hodgkin's lymphoma of bone is a rare, malignant hematologic tumor affecting most commonly persons in the fourth decade of life. The tumor produces predominantly osteolytic lesions usually in the femur and pelvic bones and, very rarely, may present with spinal epidural involvement. The authors discuss an interesting case of primary non-Hodgkin's lymphoma of bone involving the sacrum with epidural invasion, in which the atypical imaging findings along with negative biopsy results delayed diagnosis.

Osteonecrosis of the patella: imaging features.

Osteonecrosis of the patella, although uncommon, has become important to recognize because it can be a cause of pain in the knee. We describe the imaging manifestations of nontraumatic osteonecrosis of the patella in seven clinical cases. The lesions uniformly involved the superior aspect of the patella. Conventional radiography displayed increased radiodensity, subchondral radiolucent areas, and typical demarcation line surrounding the ischemic region. MR imaging and bone scintigraphy demonstrated the characteristic features of osteonecrosis. Recognition of the imaging findings of osteonecrosis involving the patella can preclude misdiagnosis and may obviate unproductive invasive diagnostic procedures.

Mesenchymal chondrosarcoma of soft tissues of the calf.

Mesenchymal chondrosarcomas are distinct from conventional and dedifferentiated chondrosarcomas and are quite rare, making up less than 2% of all chondrosarcomas. We describe a mesenchymal chondrosarcoma of the soft tissues of the calf and review the differential diagnosis of this poorly understood entity.

Avulsion fractures of the medial and lateral malleoli of the ankle in cadavers: new radiographic projections for improved diagnosis.

The malleolar attachment sites of the tibionavicular (TN), tibiocalcaneal (TC), posterior tibiotalar (PTT), anterior talofibular (ATF), and calcaneofibular (CF) ligaments of 3 cadaveric ankles were dissected. Standard and new radiographic projections of the ankle were obtained with the foot in different positions and various degrees of beam angulation. Simulated avulsion injuries related to these ligaments were created, and the visibility of these structures was assessed. Avulsion injuries of the TN ligament were better assessed in the plantar-flexed radiographs with lateral beam angulation. Standard projections were found to adequately depict avulsion fractures related to the TC and CF ligaments. Radiographs in external ankle rotation were best for evaluating injuries of the PTT ligament. Avulsion injuries related to the ATF ligament were best visualized in the plantar-flexed views with medial beam angulation. Modified radiographic projections of the ankle improve visualization of ligamentous structures of the malleoli and avulsion injuries related to those.

Skeletal muscle disease: patterns of MRI appearances.

Although the presumptive diagnosis of skeletal muscle disease (myopathy) may be made on the basis of clinical-radiological correlation in many cases, muscle biopsy remains the cornerstone of diagnosis. Myopathy is suspected when patients complain that the involved muscle is painful and tender, when they experience difficulty performing tasks that require muscle strength or when they develop various systemic manifestations. Because the cause of musculoskeletal pain may be difficult to determine clinically in many cases, MRI is increasingly utilised to assess the anatomical location, extent and severity of several pathological conditions affecting muscle. Infectious, inflammatory, traumatic, neurological, neoplastic and iatrogenic conditions can cause abnormal signal intensity on MRI. Although diverse, some diseases have similar MRI appearances, whereas others present distinct patterns of signal intensity abnormality. In general, alterations in muscle signal intensity fall into one of three cardinal patterns: muscle oedema, fatty infiltration and mass lesion. Because some of the muscular disorders may require medical or surgical treatment, correct diagnosis is essential. In this regard, MRI features, when correlated with clinical and laboratory findings as well as findings from other methods such as electromyography, may facilitate correct diagnosis. This article will review and illustrate the spectrum of MRI appearances in several primary and systemic disorders affecting muscle, both common and uncommon. The aim of this article is to provide radiologists and clinicians with a collective, yet succinct and useful, guide to a wide array of myopathies.