Comparative study of surgical instruments from sterile-service departments for presence of residual gram-negative endotoxin and proteinaceous deposits

The ineffective cleaning of surgical instruments may be a vector for the transmission of hospital-acquired infections. The aim of this research was to investigate whether further decontamination procedures need to be instigated in sterile-service departments (SSDs) to reduce the risk of nosocomial illnesses, such as endotoxemia, sepsis, or iatrogenic Creutzfeldt-Jakob disease (to date, 1,147 cases of confirmed Creutzfeldt-Jakob disease deaths in the United Kingdom since 1990 have been reported). Instrument sets were obtained from nine anonymous United Kingdom National Health Service (NHS) primary care trust SSDs. The investigation implemented an advanced light microscopy technique, episcopic differential interference contrast microscopy with the sensitive fluorescent reagents SYPRO Ruby and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI), to detect proteinaceous and microbial contamination levels. Gram-negative lipopolysaccharide (LPS) endotoxin was monitored using a dansylated polymyxin B fluorochrome agent. None of the 260 instruments examined displayed signs of microbial colonization or LPS endotoxin contamination. However, over 60 percent of the instruments showed a high degree of protein soiling (0.4 to 4.2 mu g protein/mm(2)). Some instruments appeared soiled with crystalline deposits that may consist of a potentially hazardous material contributing to inflammation and/or surgical shock. It is clear that the overall standard for cleaning must be raised in order to fulfill the imminent introduction of new European standards and to reduce the risk of cross-patient contamination and iatrogenic transmissio

Comparison between visual analysis and microscope assessment of surgical instrument cleanliness from sterile service departments

Modern hospital sterile service departments (SSDs) routinely inspect instruments visually to assess the degree of contamination present after the washer/disinfector cycle.We aimed to test the effectiveness and reliability of this method. Surgical instrument sets were obtained from nine anonymous National Health Service (NHS) Primary Care Trust SSDs to investigate the efficacy of ‘in-place’ cleaning procedures. The instruments were first inspected visually, followed by a novel technique called episcopic differential interference contrast microscopy. This was combined with a sensitive fluorescent reagent, SYPRORuby, to rapidly visualise and assess contamination levels on the medical devices. The application of a Contamination Index (0e4) for both proteinaceous and non-proteinaceous deposits on the surface allowed quantitative assessment. Close correlation was seen for simple instruments between visual assessment and microscopic analysis. For more complex instruments,however, there was a marked difference between the two assessment techniques and the microscopy procedure showed areas of proteinaceous and non-proteinaceous crystalline soiling that was difficult or impossible to see by eye. Visual assessment of cleaning is fraught with possible error. This survey shows how large amounts of contamination could pass undetected using such antiquated methods. The new methodology applied in the assessment of surface contamination is rapid and generally applicable and could be used more widely for routine monitoring of instrument cleanliness.<br/

Effect of drying time, ambient temperature and pre-soaks on prion-infected tissue contamination levels on surgical stainless steel: concerns over prolonged transportation of instruments from theatre to central sterile service departments

Iatrogenic transmission of prions through use of surgical instruments has been shown both experimentally and clinically. In addition, recent discoveries of prion protein accumulation in peripheral tissues such as appendix and muscle, and evidence suggesting human-to-human blood-borne transmission, have led to a concern that any residual soiling containing this agent may remain infectious even after sterile service processing. Removal of all proteinaceous material from surgical devices is extremely important for effective sterilization. This removal can be severely hampered if the contaminant is allowed to dry onto the instrument surface for any length of time. The current move to centralize sterile service centres and the inevitable lengthening of transport time between theatres and re-processing makes it necessary to minimize the amount of residual soiling adhering to an instrument before sterilization. This investigation simulates the period between the application of surgical instruments in theatre and their initial pre-wash by a washer/disinfector. The aim was to investigate the kinetics of drying at different temperatures, and the application of different commercially available pre-soak solutions in situ. The findings show that all pre-soaks significantly reduce (by up to 96%) the prion-infected tissue contamination, and that controlling the temperature whilst in transit between theatres and cleaning facilities may allow an increase in time before high protein adsorption levels occu

Micro-computer tomography: an aid in the investigation of structural changes in lead zirconate titanate ceramics after temperature-humidity bias testing

Lead zirconate titanate ceramic actuators are extensively used in electronic and electro-mechanical devices. Under humid conditions with a d.c. bias leakage currents increase power consumption In some materials the increasing leakage current is accompanied by the evolution of features on the anode surface, but little is known of any changes to the internal structure of the material. This research applies an advanced imaging technique (micro-computer tomography) to non-destructively investigate these features. This allows the evolution of internal features over time to be studied. The findings reveal that the microstructure of the ceramic was significantly altered during environmental testing

Are surgical stainless steel wires used for intracranial implantation of PrPsc a good model of iatrogenic transmission from contaminated surgical stainless steel instruments after cleaning?

Transmissible spongiform encephalopathies are a group of fatal, neurodegenerative diseases commonly known as prion diseases. Prion diseases can resist traditional inactivation strategies and may be iatrogenically transmitted by surgical instruments through the human population. These properties have led to the need for a suitable detection method of the prion infectious agent, and increased pressure regarding the development of anti-prion cleaning methodologies that would ensure the safety of surgical instruments. Although other techniques have been applied, the animal bioassay remains the 'gold standard' method for assessing infectivity. As the vast majority of surgical instruments are made of stainless steel, and in order to test this surface using the animal bioassay, the application of very thin surgical stainless steel wires has been widely adopted. These wires are easily inoculated and may be reimplanted into animals without the requirement for elution of the residual material. However, their comparability to the dimensions, shape and size of surgical instruments is questionable. This article shows how such contaminated wires (residual protein between 6.3 and 16.0 ng/ mm(2)) can be cleaned more easily than flat metal surfaces (residual protein between 63.9 and 89.3 ng /mm(2)) under comparable conditions using recommended cleaning agents. These results indicate that the application of wires as a realistic means of assessing the removal or inactivation of the prion infectious agent from surgical instruments should be treated with caution

The sensitivity of approved Ninhydrin and Biuret tests in the assessment of protein contamination on surgical steel as an aid to prevent iatrogenic prion transmission

Regulations recommend the routine application of biochemical tests, such as the Ninhydrin or Biuret tests, to confirm the efficacy of hospital sterile service department (SSD) washer-disinfector cycles in removing proteinaceous material, particularly with respect to prions. The effectiveness of these methods relies on both the effective sampling of the instruments and the sensitivity of the tests employed. Two commercially available contamination assessment tests were evaluated for their sensitivity to ME7 brain homogenate on surgical-grade stainless steel surfaces. Controls were visualized by the application of episcopic differential interference contrast/Epi-fluorescence microscopy (EDIC/EF) combined with the sensitive fluorescent reagent, SYPRO Ruby, which has been shown previously to rapidly visualize and assess low levels of contamination on medical devices. The Ninhydrin test displayed a minimum level of detection observed by 75% of volunteers (MLD75) of 9.25 ?g [95% confidence interval (95% CI) 8.6–10.0 ?g]. The Biuret test provided better sensitivity, with a MLD75 of 6.7 ?g (95% CI 5.4–8.2 ?g). However, much lower concentrations of proteinaceous soiling (pg) were visualized using the EDIC/EF microscopy method. From these findings, it is clear that these approved colorimetric tests of cleaning are relatively insensitive. This investigation demonstrates how large amounts (up to 6.5 ?g) of proteinaceous brain contamination could remain undetected and the instruments deemed clean using such methods. The application of more sensitive cleanliness evaluation methods should be applied to reduce the risk of iatrogenic transmission of prion disease in ‘high-risk’ instruments such as neurosurgical devices

Rapid method for the sensitive detection of protein contamination on surgical instruments

Hospital sterile service departments (SSDs) currently rely on simple visual confirmation of cleanliness as an assessment of the efficacy of cleaning surgical instruments. The inherent inability to monitor tow Levels of infectious or proteinaceous contamination on surgical instruments creates the possibility that highly dangerous and robust biological, agents may remain infectious and undetected even after standard cleaning and sterilization procedures have been employed. This paper describes the development of a novel. microscopy technique, episcopic differential. interference contrast microscope, combined with the fluorescent reagent, SYPRO Ruby, to rapidly detect brain tissue protein to below 400 Pg/mm(2) on an instrument surface. This technique has displayed a minimum level of detection observed by 50% of volunteers of 85 pg/mm(2) (95% confidence intervals 67-112 pg/mm(2)). Quantitative assessment of instruments supplied from various SSDs enabled the establishment of a 'contamination index' of both proteinaceous and non-proteinaceous deposits on the surface. This new methodology for the assessment of surface contamination is generally applicable and should facilitate future quantitative surveys of instrument contamination in hospitals and other healthcare environments

Respostas a uma crítica marxista às perspectivas retórica e pragmática em economia

<abstract language="eng">Answers to a marxist critic of the rhetorical and pragmatic perspectives in economics. Based on recent discussions regarding the rhetorical perspective in economics, this paper presents an interpretation of the philosophical approach of Habermas which attempts to rescue the so called 'modern spirit', forgotten in the annals of the 19th century, similar to that presented by Marshall Berman in 1982. Following the reconstructive approach of Habermas's project of modernity, we attempt to show how a 'rhetorical approach' could be applied in the field of economics, and yet still be clearly modern by taking into account intersubjectivities, given the expanded sphere of human communication (as defended in the theory of communicative action of Habermas). In this sense, we will seek to demonstrate the philosophical limits of the anti-rhetorical critiques of, for example, Paulani (1996, 2003, 2005, 2006), which seem to underestimate the linguistic and intersubjective aspect of Habermas's philosophical project that can also be found in McCloskey’s methodological approach

Influence of the temperature on the structure of an amorphous Ni 46 Ti 54 alloy produced by mechanical alloying

61.43.Dq Amorphous semiconductors, metals, and alloys, 81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation, 61.43.Bn Structural modeling: serial-addition models, computer simulation, 65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.,