Laparoscopic cholecystectomy: the missed diagnosis

Background: All 534 laparoscopic cholecystectomies performed by five surgeons at a single institution over a 3-year period were reviewed as part of a quality assurance process. The aim of the review, which has previously been published in this journal, was to identify and quantify complications of the procedure. Five cases in this series were recognized where major intra-abdominal pathology not identified at the time of laparoscopic cholecystectomy required laparotomy shortly thereafter. These five cases are reported here because there has been little discussion in the literature of this problem associated with laparoscopic cholecystectomy. Methods: The records of all 534 patients having a laparoscopic cholecystectomy between October 1990 and September 1993 were reviewed and entered into a computer database (Microsoft Access). This data collection and recording have subsequently become an ongoing process of quality assurance. Results: Five of 534 patients treated by laparoscopic cholecystectomy failed to have resolution of their symptoms post-operatively. A laparotomy was subsequently required within 3–12 months which demonstrated causative pathology present, but not detected at, the time of laparoscopic cholecystectomy. Where possible, treatment of these laparotomy findings resolved the initial presenting symptoms of colicky epigastric pain. Conclusions: The rate of ‘missed diagnosis’ is found to be < 1%. Laparoscopic cholecystectomy is a therapeutic, rather than diagnostic, procedure, and pre-operative discussion should include the possibility of further procedures being required subsequently, particularly when symptoms and signs are atypical

A Comparison of Qualitative and Quantitative Methods used to Define the Resolution of Two Overlapping Reversible Processes in Second and Fundamental Harmonic Alternating Current Voltammetry

Different authors have reached different conclusions concerning the relative resolving power of the fundamental and second harmonic alternating current voltammetric (polarographic) techniques. In this paper, the different qualitative and quantitative methods used to define the resolution of two overlapping processes in alternating current voltammetry have been evaluated. With all qualitative definitions, resolution of the second harmonic method is confirmed to be marginally superior to the fundamental harmonic. However, quantitatively, the resolution achieved with either method is so similar that the relative order to resolving power reported has actually been determined by the definition of resolution used and subtle differences in the examples chosen to evaluate the resolution. Experimental data confirm that the similarities in the qualitative aspects of resolution are far more substantial than the differences

Oxidation of the Platinum (II) Anticancer Agent [Pt{(p-BrC6F4)NCH2CH2NEt2}Cl(py)] to Platinum (IV) Complexes by Hydrogen Peroxide

PtIV coordination complexes are of interest as prodrugs of PtII anticancer agents, as they can avoid deactivation pathways owing to their inert nature. Here, we report the oxidation of the antitumor agent [PtII(p-BrC6F4)NCH2CH2NEt2}Cl(py)], 1 (py = pyridine) to dihydroxidoplatinum(IV) solvate complexes [PtIV{(p-BrC6F4)NCH2CH2NEt2}Cl(OH)2(py)].H2O, 2·H2O with hydrogen peroxide (H2O2) at room temperature. To optimize the yield, 1 was oxidized in the presence of added lithium chloride with H2O2 in a 1:2 ratio of Pt: H2O2, in CH2Cl2 producing complex 2·H2O in higher yields in both gold and red forms. Despite the color difference, red and yellow 2·H2O have the same structure as determined by single-crystal and X-ray powder diffraction, namely, an octahedral ligand array with a chelating organoamide, pyridine and chloride ligands in the equatorial plane, and axial hydroxido ligands. When tetrabutylammonium chloride was used as a chloride source, in CH2Cl2, another solvate, [PtIV{(p-BrC6F4)NCH2CH2NEt2}Cl(OH)2(py)].0.5CH2Cl2, 3·0.5CH2Cl2, was obtained. These PtIV compounds show reductive dehydration into PtII [Pt{(p-BrC6F4)NCH=CHNEt2}Cl(py)], 1H over time in the solid state, as determined by X-ray powder diffraction, and in solution, as determined by 1H and 19F NMR spectroscopy and mass spectrometry. 1H contains an oxidized coordinating ligand and was previously obtained by oxidation of 1 under more vigorous conditions. Experimental data suggest that oxidation of the ligand is favored in the presence of excess H2O2 and elevated temperatures. In contrast, a smaller amount (1Pt:2H2O2) of H2O2 at room temperature favors the oxidation of the metal and yields platinum(IV) complexes

Cyclic Voltammetric Experiment - Simulation. Comparisons of the Complex Mechanism Associated with Electrochemical Reduction of Zr4+ in LiCl-KCl Eutectic Molten Salt

Nuclear energy increasingly represents an important option for generating largely clean CO2-free electricity and zirconium is a fission product that is expected to be present in irradiated fuels. The present investigation addresses the electrochemical reduction of Zr4+ to Zro in LiCl - KCl eutectic molten salt in the temperature range 425–550◦C using cyclic voltammetry (CV), square-wave voltammetry (SWV) and bulk electrolysis. Simulations of the CV data indicate that the initial reduction proceeds through surface confined steps: Zr4+* + 2e− ↔Zr2+* and Zr2+* + 2e− ↔Zr* processes (* adsorbed species) followed by a peak-shaped complex diffusion controlled step that consists of a combination of closely spaced processes associated with the reactions Zr4+ + 4e− →Zr and Zr4+ + 3e− →Zr+*. Zr+*, probably in the form of ZrCl* is then further reduced to Zro* at even more negative potentials. The simulations provide the first quantitative analysis of the thermodynamics and kinetics of the Zr4+ reduction in the LiCl-KCl eutectic

Electrolyte cation dependence of the electron transfer kinetics associated with the [SVW 11 O 40 ] 3–/4– (V V/IV ) and [SVW 11 O 40 ] 4–/5– (W VI/V ) processes in propylene carbonate

Changing the supporting electrolyte cation from tetrabutylammonium to 1-butyl-3-methylimidazolium is known to significantly increase the apparent heterogeneous electron transfer rate constants (k0 value at the formal reversible potential, (EF0)) associated with the [SVW11O40]3−/4− (VV/IV) and [SVW11O40]4−/5− (WVI/V) processes in aprotic organic media. In this study, supporting electrolytes containing 7 different cations, namely 1-ethyl-3-methylimidazolium ([EMIM]+), 1-butyl-3-methylimidazolium ([BMIM]+), 1-butyl-1-methylpyrrolidinium ([Py14]+), tetraethylammonium ([TEA]+), tetrapropylammonium ([TPA]+), tetrabutylammonium ([TBA]+) and tetrahexylammonium ([THA]+), have been investigated in order to provide a systematic account of the influence of the electrolyte cations on the rate of polyoxometalate (POM) electron transfer at a platinum disk electrode. Fourier transformed alternating current (FTAC) voltammetry has been used for the measurement of fast kinetics and DC cyclic voltammetry for slow processes. The new data reveal the formal reversible potentials and electron-transfer rate constants associated with the VV/IV (kV0) and WVI/V (kW0) processes correlate with the size of the supporting electrolyte cation. kV0 and kW0 values decrease in the order, [EMIM]+ > [BMIM]+ > [Py14]+ ≈ [TEA]+ > [TPA]+ > [TBA]+ > [THA]+ for both processes. However, while kV0 decreases gently with increasing cation size (k0 = 0.1 and 0.002 cm s−1 with [EMIM]+ and [THA]+ electrolyte cations, respectively), the decrease in kW0 is much more drastic (k0 = 0.1 and 2 × 10−6 cm s−1 for [EMIM]+ and [THA]+, respectively). Possible explanations for the observed trends are discussed (e.g., ion-pairing, viscosity, adsorption and the double-layer effect), with inhibition of electron-transfer by a blocking “film” of electrolyte cations considered likely to be the dominant factor, supported by a linear plot of ln(k0) vs. ln(d) (where d is the estimated thickness of the adsorbed layer on the electrode surface) for both the VV/IV and WVI/V processes

Strengthening impact assessment: a call for integration and focus

We suggest that the impact assessment community has lost its way based on our observation that impact assessment is under attack because of a perceived lack of efficiency. Specifically, we contend that the proliferation of different impact assessment types creates separate silos of expertise and feeds arguments for not only a lack of efficiency but also a lack of effectiveness of the process through excessive specialisation and a lack of interdisciplinary practice. We propose that the solution is a return to the basics of impact assessment with a call for increased integration around the goal of sustainable development and focus through better scoping. We rehearse and rebut counter arguments covering silo-based expertise, advocacy, democracy, sustainability understanding and communication. We call on the impact assessment community to rise to the challenge of increasing integration and focus, and to engage in the debate about the means of strengthening impact assessment

Impact of adsorption on scanning electrochemical microscopy voltammetry and implications for nanogap measurements

Scanning electrochemical microscopy (SECM) is a powerful tool that enables quantitative measurements of fast electron transfer (ET) kinetics when coupled with modeling predictions from finite-element simulations. However, the advent of nanoscale and nanogap electrode geometries that have an intrinsically high surface area-to-solution volume ratio realizes the need for more rigorous data analysis procedures, as surface effects such as adsorption may play an important role. The oxidation of ferrocenylmethyl trimethylammonium (FcTMA+) at highly oriented pyrolytic graphite (HOPG) is used as a model system to demonstrate the effects of reversible reactant adsorption on the SECM response. Furthermore, the adsorption of FcTMA2+ species onto glass, which is often used to encapsulate ultramicroelectrodes employed in SECM, is also found to be important and affects the voltammetric tip response in a nanogap geometry. If a researcher is unaware of such effects (which may not be readily apparent in slow to moderate scan voltammetry) and analyzes SECM data assuming simple ET kinetics at the substrate and an inert insulator support around the tip, the result is the incorrect assignment of tip–substrate heights, kinetics, and thermodynamic parameters. Thus, SECM kinetic measurements, particularly in a nanogap configuration where the ET kinetics are often very fast (only just distinguishable from reversible), require that such effects are fully characterized. This is possible by expanding the number of experimental variables, including the voltammetric scan rate and concentration of redox species, among others

Electrochemical reduction of CO2 with an oxide-derived lead nano-coralline electrode in dimcarb

Electroreduction of CO2 in the distillable ionic liquid dimethylammonium dimethylcarbamate (dimcarb) has been investigated with an oxide‐derived lead (od‐Pb) electrode. Compared with unmodified polycrystalline Pb, where H2 is the dominant electrolysis product, od‐Pb possesses impressive catalytic properties for the reduction of CO2 in dimcarb (mixing molar ratio of CO2 and dimethylamine (DMA) >1 : 1.8), with faradaic efficiencies for the generation of H2, CO, and [HCOO]− of approximately 15, 10, and 75 %, respectively. These efficiencies are independent of the applied potential in the range of −1.34 to −3.34 V vs. Cc0/+ (where Cc+=cobaltocenium). Thorough analysis of the properties of od‐Pb, we demonstrate that its intrinsically high catalytic activity towards CO2 reduction compared to bulk Pb is attributable to an increased surface roughness and greater surface area (ca. 10 times higher), rather than the existence of residual metal oxides that are known to suppress the hydrogen evolution reaction, preferred crystal orientation, or the existence of metastable active sites