Older adults experience of transition to the community from the emergency department: a qualitative evidence synthesis

AIM

Older adults comprise a growing proportion of Emergency Department (ED) attendees and are vulnerable to adverse outcomes following an ED visit including ED reattendance within 30 days. Interventions to reduce older adults' risk of adverse outcomes following an ED attendance are proliferating and often focus on improving the transition from the ED to the community. To optimise the effectiveness of interventions it is important to determine how older adults experience the transition from the ED to the community. This study aims to systematically review and synthesise qualitative studies reporting older adults' experiences of transition to the community from the ED.

METHODS

Six databases (Academic Search Complete, CINAHL, MEDLINE, PsycARTICLES, PsycINFO, and Social Science Full Text) were searched in March 2022 and 2023. A seven-step approach to meta-ethnography, as described by Noblit and Hare, was used to synthesise findings across included studies. The methodological quality of the included studies was appraised using the 10-item Critical Appraisal Skills Programme (CASP) checklist for qualitative research. A study protocol was registered on PROSPERO (Registration: CRD42022287990).

FINDINGS

Ten studies were included, and synthesis led to the development of five themes. Unresolved symptoms reported by older adults on discharge impact their ability to manage at home (theme 1). Limited community services and unresolved symptoms drive early ED reattendance for some older adults (theme 2). Although older adults value practical support and assistance transporting home from the ED this is infrequently provided (theme 3). Accessible health information and interactions are important for understanding and self-managing health conditions on discharge from the ED (theme 4). Fragmented Care between ED and community is common, stressful and impacts on older adult's ability to manage health conditions (theme 5). A line of argument synthesis integrated these themes into one overarching concept; after an ED visit older adults often struggle to manage changed, complex, health and care needs at home, in the absence of comprehensive support and guidance.

DISCUSSION/ CONCLUSION

Key areas for consideration in future service and intervention development are identified in this study; ED healthcare providers should adapt their communication to the needs of older adults, provide accessible information and explicitly address expectations about symptom resolution during discharge planning. Concurrently, community health services need to be responsive to older adults' changed health and care needs after an ED visit to achieve care integration. Those developing transitional care interventions should consider older adults needs for integration of care, symptom management, clear communication and information from providers and desire to return to daily life.

Exploring stakeholders' experiences of comprehensive geriatric assessment in the community and out-patient settings: a qualitative evidence synthesis

BACKGROUND

Comprehensive Geriatric Assessment (CGA) is a multidimensional interdisciplinary process that addresses an older adult's biopsychosocial capabilities to create an integrated and co-ordinated plan of care. While quantitative evidence that demonstrates the positive impacts of CGA on clinical and process outcomes has been synthesised, to date qualitative research reporting how older adults and service providers experience CGA has not been synthesised. This study aimed to systematically review and synthesise qualitative studies reporting community-dwelling older adults', caregivers' and healthcare professionals' (HCP) experiences of CGA in the primary care and out-patient (OPD) setting.

METHOD

We systematically searched five electronic databases including MEDLINE, CINAHL, PsycINFO, PsycARTICLES and Social Sciences Full Text targeting qualitative or mixed methods studies that reported qualitative findings on older adults', caregivers' and HCPs' experiences of CGA in primary care or out-patient settings. There were no language or date restrictions applied to the search. The protocol was registered with the PROSPERO database (Registration: CRD42021283167). The methodological quality of the included studies was appraised using the Critical Appraisal Skills Programme checklist for qualitative research. Results were synthesised according to Noblit and Hare's seven-step approach to meta-ethnography, which involves an iterative and inductive process of data synthesis.

RESULTS

Fourteen studies were included where CGA was completed in the home, general practice, out-patient setting in acute hospitals and in hybrid models across the community and hospital-based OPD settings. Synthesis generated four key themes: (1) CGA is experienced as a holistic process, (2) The home environment enhances CGA, (3) CGA in the community is enabled by a collaborative approach to care, and (4) Divergent experiences of the meaningful involvement of older adults, caregivers and family in the CGA process.

CONCLUSION

Findings demonstrate that CGA in a home-based or OPD setting allows for a holistic and integrated approach to care for community-dwelling older adults while increasing patient satisfaction and accessibility of healthcare. Healthcare professionals in the community should ensure meaningful involvement of older adults and their families or caregivers in the CGA process. Further robustly designed and well reported trials of different models of community-based CGA informed by the findings of this synthesis are warranted.

Establishing the core elements of a frailty at the front door model of care using a modified real-time Delphi technique

BACKGROUND

Innovations in models of care for older adults living with frailty presenting to the emergency department (ED) have become a key priority for clinicians, researchers and policymakers due to the deleterious outcomes older adults experience due to prolonged exposure to such an environment. This study aimed to develop a set of expert consensus-based statements underpinning operational design, outcome measurement and evaluation of a Frailty at the Front Door (FFD) model of care for older adults within an Irish context.

METHODS

A modified real-time Delphi method was used. Facilitation of World Café focus groups with an expert panel of 86 members and seperate advisory groups with a Public and Patient Involvement panel of older adults and members of the Irish Association of Emergency Medicine generated a series of statements on the core elements of the FFD model of care. Statements were analysed thematically and incorporated into a real-time Delphi survey, which was emailed to members of the expert panel. Members were asked to rank 70 statements across nine domains using a 9-point Likert scale. Consensus criteria were defined a priori and guided by previous research using 9-point rating scales.

RESULTS

Fifty members responded to the survey representing an overall response rate of 58%. Following analyses of the survey responses, the research team reviewed statements for content overlap and refined a final list of statements across the following domains: aims and objectives of the FFD model of care; target population; screening and assessment; interventions; technology; integration of care; evaluation and metrics; and research.

CONCLUSION

Development of a consensus derived FFD model of care represents an important step in generating national standards, implementation of a service model as intended and enhances opportunities for scientific impact. Future research should focus on the development of a core outcome set for studies involving older adults in the ED.

Effectiveness of community-based multidisciplinary integrated care for older people: a protocol for a systematic review

INTRODUCTION

The increasing number of older adults with multiple complex care needs has placed increased pressure on healthcare systems internationally to reorientate healthcare delivery. For many older adults, their first point of contact with the health service is with their general practitioner (GP) and GP participation with integrated care models is the foundation of a population-based approach. A knowledge gap remains in relation to the effectiveness of GP participation in community-based integrated health and social care approaches for older adults. This systematic review aims to examine the effectiveness of multidisciplinary-integrated care for community-dwelling older adults with GP participation.

METHODS AND ANALYSIS

This systematic review will include randomised controlled trials (RCTs), quasi and cluster RCTs focusing on integrated care interventions for community-dwelling older adults by multidisciplinary teams including health and social care professionals and GPs. The databases PUBMED, EMBASE, CINAHL, Central Register of Controlled Trials in the Cochrane Library and MEDLINE will be searched. The primary outcome measure will be functional status. Secondary outcomes will include: primary healthcare utilisation, secondary healthcare utilisation, participant satisfaction with care, health-related quality of life, nursing home admission and mortality. The methodological quality of the studies will be assessed using the Cochrane Risk of Bias Tool V.2. The elements of care integration will be mapped in the individual studies using the Rainbow Model of Integrated Care taxonomy. A meta-analysis will be completed, depending on the uniformity of the data. Grading of Recommendations, Assessment, Development and Evaluation will be used to assess the certainty of evidence.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as all data included are anonymous secondary data. Scientific outputs will be presented at relevant conferences and in collaboration with our public and patient involvement stakeholder panel of older adults at the Ageing Research Centre at the University of Limerick.

PROSPERO REGISTRATION NUMBER

CRD42022309744.

Antimicrobial and Hemostatic Activities of Cotton-Based Dressings Designed to Address Prolonged Field Care Applications

INTRODUCTION

Developing affordable and effective hemostatic and antimicrobial wound dressings for prolonged field care (PFC) of open wounds is of interest to prevent infection, to prevent sepsis, and to conserve tissue viability. The need for an effective hemostatic dressing that is also antimicrobial is required of a hemostatic dressing that can be left in place for extended periods (days). This is particularly important in light of the existence of pathogens that have coagulopathy properties. Thus, dressings that provide effective hemostasis and reduction in the frequency of dressing changes, whereas exerting robust antimicrobial activity are of interest for PFC. Highly cleaned and sterile unbleached cotton has constituents not found in bleached cotton that are beneficial to the hemostatic and inflammatory stages of wound healing. Here, we demonstrate two approaches to cotton-based antimicrobial dressings that utilize the unique components of the cotton fiber with simple modification to confer a high degree of hemostatic and antimicrobial efficacy.

METHODS

Spun bond nonwoven unbleached cotton was treated using traditional pad dry cure methods to add ascorbic acid, zeolite (NaY) with pectin, calcium chloride, and sodium carbonate/calcium chloride. Similarly, nanosilver-embedded cotton fiber was blended with pristine cotton fibers at various weight ratios to produce hydroentangled nonwoven fabrics. The resulting treated fabrics were assessed for hemostasis using thromboelastographic clotting assays and antimicrobial activity utilizing American Association of Textile Chemists and Colorists 100.

RESULTS

Zeolite-containing dressings possessed significant hemostatic activity, whereas ascorbic acid- and silver-containing dressings reduced Gram-positive and Gram-negative organism numbers by several logs.

CONCLUSION

Based on this study, a multilayered hemostatic dressing with antimicrobial properties is envisioned. This dressing would be safe, would be economical, and have a stable shelf-life that would be conducive for using PFC.

Development of a Nonwoven Hemostatic Dressing Based on Unbleached Cotton: A De Novo Design Approach

Minimally processed greige (unbleached) cotton fibers demonstrate enhanced clotting relative to highly processed United States Pharmacopeia (USP) type 7 bleached cotton gauze. This effect is thought to be due to the material surface polarity. We hypothesized that a textile could be constructed, conserving the hemostasis-accelerating properties of greige cotton, while maintaining structural integrity and improving absorbance. Spun bond nonwovens of varying surface polarity were designed and prepared based on ratios of greige cotton/bleached cotton/polypropylene fibers. A thromboelastographic analysis was performed on fibrous samples in citrated blood to evaluate the rate of fibrin and clot formation. Lee White clotting times were obtained to assess the material’s clotting activity in platelet fresh blood. An electrokinetic analysis of samples was performed to analyze for material surface polarity. Hemostatic properties varied with composition ratios, fiber density, and fabric fenestration. The determinations of the surface polarity of cotton fabrics with electrokinetic analysis uncovered a range of surface polarities implicated in fabric-initiated clotting; a three-point design approach was employed with the combined use of thromboelastography, thrombin velocity index, Lee White clotting, and absorption capacity determinations applied to fabric structure versus function analysis. The resulting analysis demonstrates that greige cotton may be utilized, along with hydrophilic and hydrophobic fibers, to improve the initiation of fibrin formation and a decrease in clotting time in hemostatic dressings suitable to be commercially developed. Hydroentanglement is an efficient and effective process for imparting structural integrity to cotton-based textiles, while conserving hemostatic function.

Microwave Assisted Preparation of Self-Extinguishing Cotton Fabrics by Small Molecules Containing Phosphorous and Nitrogen

Background:

New methods for preparing surface modification of flame retardant cotton fabrics were employed by applying a microwave-assisted technique with a minimum amount of co-solvent. Efforts at flame retardant cotton fabrics treated with economic and environmentally friendly flame retardant compounds based on the small molecules piperazine, PN and PNN, were done successfully.

Methods and Results:

The evidence of flame retardant chemical penetrations or surface modification of cotton fabrics was confirmed by Scanning Electron Microscope (SEM), and the treated cotton fabrics were evaluated by flammability tests, such as 45°angle (clothing textiles test) and limiting Oxygen Index (LOI). Thermogravimetric analysis of all treated cotton fabrics in a nitrogen atmosphere showed high thermal stability, as decomposition occurred between 276.9~291.2°C with 30.5~35.7% residue weight char yield at 600°C. Limiting Oxygen Index (LOI) and the 45° angle flammability test were used to determine the efficiency of the flame-retardant treatments on the fabrics. LOI values for control twill fabric showed ~18 vol% oxygen in nitrogen, whereas the highest treatment level had 32 vol%. High add-on treatments with flame retardants also readily passed the 45° angle flammability test.

Conclusion:

In the Microscale Combustion Calorimeter (MCC) tests, a decline in heat of combustion was shown through the smaller values acquired for THR, HRC and Tmax for all PN and PNN samples.

Search for γ-Ray Line Signals from Dark Matter Annihilations in the Inner Galactic Halo from 10 Years of Observations with H.E.S.S

Spectral lines are among the most powerful signatures for dark matter (DM) annihilation searches in very-high-energy γ rays. The central region of the Milky Way halo is one of the most promising targets given its large amount of DM and proximity to Earth. We report on a search for a monoenergetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a two-dimensional maximum likelihood method taking advantage of both the spectral and spatial features of the signal versus background. The analysis makes use of Galactic center observations accumulated over ten years (2004-2014) with the H.E.S.S. array of ground-based Cherenkov telescopes. No significant γ-ray excess above the background is found. We derive upper limits on the annihilation cross section ⟨σv⟩ for monoenergetic DM lines at the level of 4×10^{-28}  cm^{3} s^{-1} at 1 TeV, assuming an Einasto DM profile for the Milky Way halo. For a DM mass of 1 TeV, they improve over the previous ones by a factor of 6. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV. Ground-based γ-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into two γ-ray photons at the level expected from the thermal relic density for TeV DM particles.

The application of ultrasound and enzymes in textile processing of greige cotton

A review is reported herein of the research progress made at the USDA's Southern Regional Research Center to provide an ultrasound and enzymatic alternative to the current textile processing method of scouring greige cotton textile with caustic chemicals. The review covers early efforts to measure pectin and wax removal from greige cotton textiles using standard wicking methodology and further describes an investigation of newly discovered polygalacturonase enzymes as bioscouring agents. Additional research is reviewed involving efforts to characterize and optimize the ultrasound-enhanced enzymatic scouring process through a statistical examination of the operating parameters of power, enzyme concentration, ultrasonic frequency and time.

Induction of Low-Level Hydrogen Peroxide Generation by Unbleached Cotton Nonwovens as Potential Wound Dressing Materials

Greige cotton is an intact plant fiber. The cuticle and primary cell wall near the outer surface of the cotton fiber contains pectin, peroxidases, superoxide dismutase (SOD), and trace metals, which are associated with hydrogen peroxide (H₂O₂) generation during cotton fiber development. Traditionally, the processing of cotton into gauze involves scouring and bleaching processes that remove the components in the cuticle and primary cell wall. The use of unbleached, greige cotton fibers in dressings, has been relatively unexplored. We have recently determined that greige cotton can generate low levels of H₂O₂ (5-50 micromolar). Because this may provide advantages for the use of greige cotton-based wound dressings, we have begun to examine this in more detail. Both brown and white cotton varieties were examined in this study. Brown cotton was found to have a relatively higher hydrogen peroxide generation and demonstrated different capacities for H₂O₂ generation, varying from 1 to 35 micromolar. The H₂O₂ generation capacities of white and brown nonwoven greige cottons were also examined at different process stages with varying chronology and source parameters, from field to nonwoven fiber. The primary cell wall of nonwoven brown cotton appeared very intact, as observed by transmission electron microscopy, and possessed higher pectin levels. The levels of pectin, SOD, and polyphenolics, correlated with H₂O₂ generation.

H.E.S.S. Limits on Linelike Dark Matter Signatures in the 100 GeV to 2 TeV Energy Range Close to the Galactic Center

A search for dark matter linelike signals iss performed in the vicinity of the Galactic Center by the H.E.S.S. experiment on observational data taken in 2014. An unbinned likelihood analysis iss developed to improve the sensitivity to linelike signals. The upgraded analysis along with newer data extend the energy coverage of the previous measurement down to 100 GeV. The 18 h of data collected with the H.E.S.S. array allow one to rule out at 95% C.L. the presence of a 130 GeV line (at l=-1.5°, b=0° and for a dark matter profile centered at this location) previously reported in Fermi-LAT data. This new analysis overlaps significantly in energy with previous Fermi-LAT and H.E.S.S.

RESULTS

No significant excess associated with dark matter annihilations was found in the energy range of 100 GeV to 2 TeV and upper limits on the gamma-ray flux and the velocity weighted annihilation cross section are derived adopting an Einasto dark matter halo profile. Expected limits for present and future large statistics H.E.S.S. observations are also given.

Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with H.E.S.S

The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using γ-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section ⟨σv⟩. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach ⟨σv⟩ values of 6×10^{-26}  cm^{3} s^{-1} in the W^{+}W^{-} channel for a DM particle mass of 1.5 TeV, and 2×10^{-26}  cm^{3} s^{-1} in the τ^{+}τ^{-} channel for a 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particles.

Prevalence of and attitudes about concussion in Irish schools' rugby union players

BACKGROUND

Youth rugby players represent 45.2% (N = 69,472) of the Irish rugby union playing population. The risk and consequences of concussion injury are of particular concern in these young athletes, but limited epidemiological data exists. This study investigated annual and lifetime prevalence of concussion in an Irish schoolboy rugby union cohort.

METHODS

An anonymous cross-sectional survey of youth rugby players was conducted. Diagnosed concussion was defined as an incident where diagnosis was confirmed by a health professional or coach. Demographics, prevalence, and attitudes to concussion were collated. Data were analyzed with descriptive statistics, chi-square test, t-tests, Mann-Whitney tests, and logistic regression.

RESULTS

Overall, 304 youth (aged 12-18 years) responded. Lifetime prevalence of diagnosed concussion was 19.4%, with annual (2010) prevalence 6.6%. Approximately 25.4% of players with diagnosed concussions returned to play without medical advice. Internal motivation (11.8%) was the predominant factor in feeling pressure to play while concussed. A desire for further concussion education was expressed by 89.5% of participants.

CONCLUSIONS

Reform is required to prevent and manage concussion injuries among youth players in the rugby union, including mandatory education specific to concussion and implementation of return-to-play protocols. These findings have relevance for governing bodies, coaches, clinicians, schools, parents, and rugby union players.

Electrokinetic and hemostatic profiles of nonwoven cellulosic/synthetic fiber blends with unbleached cotton

Greige cotton contains waxes and pectin on the outer surface of the fiber that are removed when bleached, but these components present potential wound dressing functionality. Cotton nonwovens blended with hydrophobic and hydrophilic fibers including viscose, polyester, and polypropylene were assessed for clotting activity with thromboelastography (TEG) and thrombin production. Clotting was evaluated based on TEG measurements: R (time to initiation of clot formation), K (time from end of R to a 20 mm clot), α (rate of clot formation according to the angle tangent to the curve as K is reached), and MA (clot strength). TEG values correlate to material surface polarity as measured with electrokinetic parameters (ζ_plateau, Δζ and swell ratio). The material surface polarity (ζ_plateau) varied from −22 to −61 mV. K values and thrombin concentrations were found to be inversely proportional to ζ_plateau with an increase in material hydrophobicity. An increase in the swell ratios of the materials correlated with decreased K values suggesting that clotting rates following fibrin formation increase with increasing material surface area due to swelling. Clot strength (MA) also increased with material hydrophobicity. Structure/function implications from the observed clotting physiology induced by the materials are discussed.

Decreased immunoglobulin E (IgE) binding to cashew allergens following sodium sulfite treatment and heating

Cashew nut and other nut allergies can result in serious and sometimes life-threatening reactions. Linear and conformational epitopes within food allergens are important for immunoglobulin E (IgE) binding. Methods that disrupt allergen structure can lower IgE binding and lessen the likelihood of food allergy reactions. Previous structural and biochemical data have indicated that 2S albumins from tree nuts and peanuts are potent allergens, and that their structures are sensitive to strong reducing agents such as dithiothreitol. This study demonstrates that the generally regarded as safe (GRAS) compound sodium sulfite effectively disrupted the structure of the cashew 2S albumin, Ana o 3, in a temperature-dependent manner. This study also showed that sulfite is effective at disrupting the disulfide bond within the cashew legumin, Ana o 2. Immunoblotting and ELISA demonstrated that the binding of cashew proteins by rabbit IgG or IgE from cashew-allergic patients was markedly lowered following treatment with sodium sulfite and heating. The results indicate that incorporation of sodium sulfite, or other food grade reagents with similar redox potential, may be useful processing methods to lower or eliminate IgE binding to food allergens.

Chromatographic and traditional albumin isotherms on cellulose: a model for wound protein adsorption on modified cotton

Albumin is the most abundant protein found in healing wounds. Traditional and chromatographic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressings is adsorption and accumulation of proteins like albumin at the solid-liquid interface of the biological fluid and wound dressing fiber. To better understand the effect of fiber charge and molecular modifications in cellulose-containing fibers on the binding of serum albumin as observed in protease sequestrant dressings, albumin binding to modified cotton fibers was compared with traditional and chromatographic isotherms. Modified cotton including carboxymethylated, citrate-crosslinked, dialdehyde and phosphorylated cotton, which sequester elastase and collagenase, were compared for their albumin binding isotherms. Albumin isotherms on citrate-cellulose, cross-linked cotton demonstrated a two-fold increased binding affinity over untreated cotton. A comparison of albumin binding between traditional, solution isotherms and chromatographic isotherms on modified cellulose yielded similar equilibrium constants. Application of the binding affinity of albumin obtained in the in vitro protein isotherm to the in vivo wound dressing uptake of the protein is discussed. The chromatographic approach to assessment of albumin isotherms on modified cellulose offers a more rapid approach to evaluating protein binding on modified cellulose over traditional solution approaches.

Flame retardant behavior of polyelectrolyte-clay thin film assemblies on cotton fabric

Cotton fabric was treated with flame-retardant coatings composed of branched polyethylenimine (BPEI) and sodium montmorillonite (MMT) clay, prepared via layer-by-layer (LbL) assembly. Four coating recipes were created by exposing fabric to aqueous solutions of BPEI (pH 7 or 10) and MMT (0.2 or 1 wt %). BPEI pH 10 produces the thickest films, while 1 wt % MMT gives the highest clay loading. Each coating recipe was evaluated at 5 and 20 bilayers. Thermogravimetric analysis showed that coated fabrics left as much as 13% char after heating to 500 degrees C, nearly 2 orders of magnitude more than uncoated fabric, with less than 4 wt % coming from the coating itself. These coatings also reduced afterglow time in vertical flame tests. Postburn residues of coated fabrics were examined with SEM and revealed that the weave structure and fiber shape in all coated fabrics were preserved. The BPEI pH 7/1 wt % MMT recipe was most effective. Microcombustion calorimeter testing showed that all coated fabrics reduced the total heat release and heat release capacity of the fabric. Fiber count and strength of uncoated and coated fabric are similar. These results demonstrate that LbL assembly is a relatively simple method for imparting flame-retardant behavior to cotton fabric. This work lays the foundation for using these types of thin film assemblies to make a variety of complex substrates (foam, fabrics, etc.) flame resistant.

A three-dimensional finite element model of maximal grip loading in the human wrist

The aim of this work was to create an anatomically accurate three-dimensional finite element model of the wrist, applying subject-specific loading and quantifying the internal load transfer through the joint during maximal grip. For three subjects, representing the anatomical variation at the wrist, loading on each digit was measured during a maximal grip strength test with simultaneous motion capture. The internal metacarpophalangeal joint load was calculated using a biomechanical model. High-resolution magnetic resonance scans were acquired to quantify bone geometry. Finite element analysis was performed, with ligaments and tendons added, to calculate the internal load distribution. It was found that for the maximal grip the thumb carried the highest load, an average of 72.2 +/- 20.1 N in the neutral position. Results from the finite element model suggested that the highest regions of stress were located at the radial aspect of the carpus. Most of the load was transmitted through the radius, 87.5 per cent, as opposed to 12.5 per cent through the ulna with the wrist in a neutral position. A fully three-dimensional finite element analysis of the wrist using subject-specific anatomy and loading conditions was performed. The study emphasizes the importance of modelling a large ensemble of subjects in order to capture the spectrum of the load transfer through the wrist due to anatomical variation.

The relation between MRI neuroactivation changes and response rate on a word-fluency task

This study investigated the functional magnetic resonance imaging response of the left premotor cortex activated during a word-fluency task. We hypothesized that a cortical region crossing the boundary between Brodmann's areas 44 and 6 would show bias toward output during word generation (i.e., the more words generated the greater the activation), supporting the view that this region is involved in the motor planning of speech rather than the search component of word generation. Ten participants were shown letters with different word-generational frequencies, and these were correlated with magnetic resonance signal changes over the region. Significant differences (p = .05) were found in the neuroactivation changes between groups of letters associated with high and low overt frequencies. This finding supports our hypothesis concerning the role of areas 44 and 6 in word-generation tasks.

The ferromagnetic pillow: a potential MR hazard not detectable by a hand-held magnet

This paper describes an incident in which an apparently normal hospital pillow became a ferromagnetic missile when brought into the proximity of a 1.5 T MR system owing to a fine internal spring system within the pillow. Measurements revealed that the 1 kg pillow reached a maximum velocity of 33.7 km h(-1) after undergoing a maximum acceleration of 9.9g. Non-pathological cervical spines should sustain the measured forces and torques without significant injury. However, the effect could be injurious or even fatal to patients suffering from an existing cervical instability, for example due to rheumatoid arthritis. Of more general concern is the fact that the use of a powerful hand-held magnet did not reveal the presence of ferromagnetic components in this instance. Large objects containing sparsely distributed ferromagnetic materials may not be deflected by such a magnet but could still represent a hazard in the MR environment.

Method of determination of three dimensional index finger moment arms and tendon lines of action using high resolution MRI scans

High-resolution MRI scans, in conjunction with CAD software, were used to determine the three-dimensional moment arms and force vector direction cosines for 11 structures passing the interphalangeal and metacarpophalangeal joints of the index finger. The results are presented for five different angles of joint flexion for a single subject. The moment arm data obtained differ from previous studies, where results have been derived from tendon excursion techniques or geometrical models. These dissimilarities have been accounted for by the differences in experimental techniques.

Thermal injuries associated with MRI

Most physicians are aware of the absolute contraindications to magnetic resonance imaging (MRI). However, less familiar is the potential for an MRI-induced thermal or electrical burn associated with electrical monitoring devices. Although detailed studies concerning the burn hazard in MRI have not been reported, it is widely believed that direct electromagnetic induction in looped cables associated with the patient is responsible for the excessive heating and it is on this theory that present guidelines are based. Recent reports have however indicated that other mechanisms may cause the heating of metal, either in or on the patient. This document reviews numerous reported burn injuries sustained during MRI and addresses the underlying heating mechanisms possibly causing these events.

Investigation of the factors responsible for burns during MRI

Numerous reported burn injuries have been sustained during clinical MRI procedures. The aim of this study was to investigate the possible factors that may be responsible for such burns. Experiments were performed to investigate three possible mechanisms for causing heating in copper wire during MRI: direct electromagnetic induction in a conductive loop, induction in a resonant conducting loop, and electric field resonant coupling with a wire (the antenna effect). Maximum recorded temperature rises were 0.6 degrees C for the loop, 61.1 degrees C for the resonant loop, and 63.5 degrees C for the resonant antenna. These experimental findings suggest that, contrary to common belief, it is unlikely that direct induction in a conductive loop will result in thermal injury. Burn incidents are more likely to occur due to the formation of resonant conducting loops and from extended wires forming resonant antenna. The characteristics of resonance should be considered when formulating safety guidelines.

Estimation of torque on mechanical heart valves due to magnetic resonance imaging including an estimation of the significance of the Lenz effect using a computational model

Mitral and aortic valve replacement is a procedure which is common in cardiac surgery. Some of these replacement valves are mechanical and contain moving metal parts. Should the patient in whom such a valve has been implanted be involved in magnetic resonance imaging, there is a possible dangerous interaction between the moving metal parts and the static magnetic field due to the Lenz effect. Mathematical models of two relatively common forms of single-leaflet valves have been derived and the magnitude of the torque which opposes the motion of the valve leaflet has been calculated for a valve disc of solid metal. In addition, a differential model of a ring-strengthener valve type has been considered to determine the likely significance of the Lenz effect in the context of the human heart. For common magnetic field strengths at present, i.e. 1 to 2 T, the effect is not particularly significant. However, there is a marked increase in back pressure as static magnetic field strength increases. There are concerns that, since field strengths in the range 3 to 4 T are increasingly being used, the Lenz effect could become significant. At 5 to 10 T the malfunction of the mechanical heart valve could cause the heart to behave as though it is diseased. For unhealthy or old patients this could possibly prove fatal.

Potential MR hazard to patients with metallic heart valves: the Lenz effect

The Lenz effect on the motion of metal containing moving parts of artificial heart valves has not been considered to date. In this paper the basic theory is outlined and a simple model applied to estimate worst-case forces on such valves. The results indicate a potential for forces over 100 times greater than for the more widely recognized ferromagnetic interation. Resistive pressure effects comparable to cardiac pressure differences may occur for such valves in the mitral position even at fields as low as 1.5 T. The effect will increase linearly with field strength. Additional monitoring and perhaps even exclusion of such patients may be prudent, even at 1.5 T.

Early 1H magnetic resonance spectroscopy of acute head injury: four cases

In an attempt to examine in vivo the early metabolic consequences of severe acute head injury, 1H MRS was performed in four patients from 8 to 25 h (mean 15 h) following trauma. In three of these patients, decompressive surgery was performed 4-5 h prior to the MRS. High levels of lactate (area of lactate peak >50% of the mean areas of the NAA, choline-containing, and creatine-containing compound peaks) were found at 8 h posttrauma in the one patient who was not operated on and at 10 h posttrauma in one of the patients who underwent surgery. In the other two postoperative patients, at 18 and 25 h after trauma, lactate levels were found to be low (lactate peak <20% of the mean area of the other three peaks). In the one patient who had a follow-up at 6 days and who had the largest initial lactate levels, these remained high. These findings suggest that high levels of lactate may not be an inevitable consequence of severe head injury and that similar MRS studies should be performed on each individual patient before therapies to reduce lactate are considered. There appeared to be no correlation between the relative amounts of lactate and outcome.

Structure and functional relationships in human pur H

1. The human pur H (ATIC) gene encoding a bifunctional protein, hPurH, which carries the penultimate and final enzymatic activities of the purine nucleotide synthesis pathway, AICARFT & IMPCH, has been cloned and sequenced. The gene product, hPurH has been overexpressed in E. coli, purified to homogeneity and crystallized. 2. The human pur H gene lies on chromosome 2, between band q34 and q35. There is at least one intron of 278 bp near the 5' end. 3. Truncation mutant studies demonstrate two non-overlapping functional domains in the protein arranged as indicated in Figure 5. The existence of a linker or interaction region between the catalytic domains remains to be established. 4. Cleland-type kinetic inhibition experiments indicate that the AICARFT reaction is of the ordered, sequential type with the reduced folate cofactor binding first. 5. The reaction has a broad pH optimum in the alkaline range, with a maximum at about pH 8.2. 6. Preliminary transient phase kinetic studies show the presence of a "burst" indicating that a late step in the reaction sequence is rate limiting. 7. A PurH crystal structure is that of a dimer, with a putative single binding site for the reduced folate cofactor formed using elements from each of the monomer subunits. Probable binding sites for AICAR and FAICAR can be identified on each monomer. 8. Equilibrium sedimentation studies show hPurH apoprotein to be a monomer:dimer equilibrium mixture with a kD of 0.55 uM. 9. The crystal structure has permitted identification of a number of candidate amino acid residues likely to be involved in catalysis and/or substrate binding. Among these, we have thus far completed studies on two, Lysine 265 and Histidine 266. These appear to be critically involved in the AICARFT reaction, although whether their role(s) are in catalysis or binding remains to be determined.

Errors in MR stereotaxy due to undetected extraneous metal objects

MR stereotaxic procedures are being increasingly used, particularly in functional neurosurgery where very high levels of localization accuracy are required. Whilst many studies have investigated intrinsic causes of non-linearity, potential errors due to an extrinsic cause are not generally appreciated. It is not uncommon to find objects such as hair clips, paper clips and pins inside high-field magnets. They can remain undetected for long periods because they can reach positions not open to visual inspection and because they often do not produce observable deterioration in routine image quality. In this study we measured the maximum absolute positional shifts caused by such objects and found that these can be significant (> 1 mm, even up to 200 mm from one such object). Additional measurements were performed using an MR compatible Leksell stereotaxic frame to calculate actual stereotaxic coordinate errors. The encompassing nature of the frame is such that some degree of compensation for such nonlinearities is inherent, and so errors for areas of the brain more proximal to the object are found to be reduced but not eliminated. Stereotaxic coordinate errors will not be reduced in nonencompassing designs and in frameless stereotaxy. The prevalence of such objects in clinical systems and the measures required to detect their presence are discussed. The need for quality control testing before each stereotaxic procedure is highlighted.

Early changes in peritumorous oedema and contralateral white matter after dexamethasone: a study using proton magnetic resonance spectroscopy

AIMS

To study the mechanism of action of steroids in patients with peritumorous oedema.

METHODS

To investigate early cerebral metabolic changes proton magnetic resonance spectroscopy (1H-MRS) was used before and 11 to 14 hours after treatment with dexamethasone (12 mg oral loading and 4 mg four times daily maintenance). Nine patients (two men, seven women, mean age 54) with pronounced oedema associated with various intracranial tumours (two astrocytomas, three meningiomas, two glioblastoma, and two metastases) were examined using MRI and MRS. SE1500/135 volume selected MRS (mean volume 21 ml) were performed on an oedematous region and a contralateral region. All spectra were acquired with and without water suppression. Metabolite peak area ratios were determined.

RESULTS

Regions of oedema had significantly (P < 0.01) higher unsuppressed water than the contralateral regions, as expected. There was no change at this early time point after dexamethasone. The ratio of the area of choline containing compounds to that creatine and phosphocreatine compounds was determined after which the serial ratios of these before and after were calculated (a serial ratio of 1.0 would indicate no change in the choline to creatine ratios after steroid administration). The mean serial ratios for the area of oedema were 1.02 (SEM 0.08) and 1.10 (0.08) for the contralateral volume of interest, indicating no significant changes. However, significant changes (P < 0.02) were found in the N-acetyl-aspartate (NAA)/choline serial ratios (0.86 (0.06) in the area of oedema, 1.20 (0.10) in contralateral brain) and the NAA/creatine serial ratios (0.86 (0.08) for the oedema, 1.25 (0.11) in contralateral brain).

CONCLUSIONS

Such rapid changes may be explained either by relatively large alterations in the relaxation characteristics of NAA or, more controversially, by actual changes in the amounts of NAA. It is proposed that steroids act primarily by causing early metabolic changes that are later expressed in improvements in intracranial volume relations.

Habituation-like effects cause a significant decrease in response in MRI neuroactivation during visual stimulation

A wide range of rest/stimulus cycle durations (40-360 sec) is reported to have been used by various groups for MRI neuroactivation studies of the visual cortex. In this paper we demonstrate a clear habituation-like response for longer cycle durations which results in a halving of apparent activation between cycle durations of 138 and 276 sec. This has important implications, not only in terms of optimizing the technique, but also in providing an insight into the underlying physiological mechanisms.

Single-chain recombinant human cytomegalovirus protease. Activity against its natural protein substrate and fluorogenic peptide substrates

We report here the production of active recombinant single-chain human cytomegalovirus protease in Escherichia coli and development of a continuous assay for this protease. In order to produce the human cytomegalovirus (HCMV) protease for structural studies and accurate kinetic analysis, mutation of alanine 143 at an internal cleavage site was introduced to prevent auto-proteolysis. The resulting soluble 29-kDa A143Q protease was purified to homogeneity as a stable single-chain protein by hydrophobic interaction and ionic-exchange chromatography. The in vivo protein substrate, assembly protein precursor, was also expressed and purified for activity studies. To develop a continuous protease assay, fluorescent synthetic peptide substrates similar to the cleavage sequence P5 to P5' of the maturation site containing anthranilic acid and nitrotyrosine as a resonance energy transfer donor-acceptor pair were designed. Purified HCMV A143Q protease cleaved the recombinant assembly protein precursor with Km and kcat values of 3.0 +/- 1.0 microM and 13.3 +/- 1.6 min-1. The Km for peptide substrates is at least 45-fold higher than for the natural protein substrate, but the kcat values are similar. A sensitive assay was developed using fluorescent peptide substrates, which can detect nM HCMV protease activity.