Magnetic resonance imaging of muscle electroporation injury

Low frequency electrical currents traversing the body during electrical shock can produce tissue damage by effects of electrical forces on cellular organelles and proteins as well as by Joule heating beyond thermotolerance. Treatment for these different injuries are quite distinct. Therefore, it is important to accurately diagnose the form of injury. Here we discuss the use of MRI for this purpose.

Dust weight and asthma prevalence in the National Survey of Lead and Allergens in Housing (NSLAH)

BACKGROUND

Settled dust has been used in studies to assess exposures to allergens and other biologically active components, but it has not been considered in the aggregate in relation to respiratory health outcomes in the general population.

OBJECTIVE

We addressed whether total house dust weight, an index of total dust exposure, was associated with respiratory health outcomes in the National Survey of Lead and Allergens in Housing (1998-1999) (NSLAH).

METHODS

NSLAH was a cross-sectional survey designed to represent permanently occupied housing units in the United States. In each household, a questionnaire was administered and settled dust was vacuumed from five locations. Linear regression models were used to identify predictors of dust weight; logistic regression models were used to examine the relationship between dust weight and asthma and wheeze.

RESULTS

Dust weight samples were available for 829 households, and survey information was available for 2,456 participants (children and adults). Lower income, older homes, household pets, having a smoker in the house, and less frequent cleaning predicted higher dust weight levels in U.S. households. Higher levels of dust weight were associated with greater odds of current asthma and wheeze. The strongest associations were seen for wheeze [adjusted odds ratio (OR) = 1.99; 95% confidence interval (CI), 1.21-3.28 for bedroom bed dust; OR = 2.81; 95% CI, 1.52-5.21 for upholstery dust). These associations persisted when adjusting for allergen and endotoxin exposures.

CONCLUSIONS

Dust weight, an index of total dust exposure in the home, may contribute to respiratory outcomes independently of the exposure to specific components.

Single-use device reuse risks

Efforts to reduce both costs and medical waste have led many health systems to start reusing single-use medical devices (SUDs) after cleaning and sterilizing (i.e. reprocessing). There is a currently a wide range of SUD types being reused in many health systems. The objective of this paper is to provide a brief summary of risk issues associated with critical SUDs, based on a rapid review of the available literature. The specific focus is on risk issues, but includes discussion of economic and legal/ethical issues as well. The evidence in the literature regarding the safety of reuse of SUDs indicates that for certain devices (e.g. heart catheters) reuse can be safe (in terms of patient infection) and cost-effective as long as stringent reprocessing protocols are followed. However, potential risks associated with reusing SUDs are not just limited to infection of patients. There are staff and environmental risks, plus important legal, ethical, and financial issues to consider in a reuse policy. There are currently no Canadian guidelines on reuse or reprocessing SUDs, although a national Scientific Advisory Panel on Reprocessing of Medical Devices has made recommendations. Additionally, reuse of SUDs is interwoven with the issue of infection control and reprocessing procedures in general and as applied to multiple-use devices. With limited healthcare resources, there will always be a trade-off between the human resources and costs required to clean and sterilize reused devices with costs associated with purchasing and disposing of non-reused SUDs. Evaluation of complete operational pathways, especially for more expensive and commonly used SUDs, will be useful to properly determine the balance of benefits, risks, and costs under a reuse policy.

Risk analysis in radiation treatment: application of a new taxonomic structure

BACKGROUND AND PURPOSE

Radiation treatment (RT) for cancer is susceptible to clinical incidents resulting from human errors and equipment failures. A systematic approach to collecting and processing incidents is required to manage patient risks. We describe the application of a new taxonomic structure for RT that supports risk analysis and organizational learning.

MATERIALS AND METHODS

A systematic analysis of the RT process identified five process domains. Within each domain we defined incident type groups. We then constructed a database reflecting this taxonomic structure and populated it with incidents from publicly available sources. Querying this database provides insights into the nature and relative frequency of incidents in RT.

RESULTS

There are relatively few reports of incidents in the Prescription domain compared with the Preparation and Treatment domains. There are also fewer reports of systematic and infrastructure incidents in comparison to sporadic and process incidents. Infrastructure incidents are mainly systematic in nature, while process incidents are more likely to be sporadic.

CONCLUSIONS

The lack of a standard, systems-oriented framework for incident reporting makes it difficult to learn from existing incident report sources. A clear understanding of the potential consequences and relationships between different incident types will guide incident reporting, resource allocation, and risk management efforts.

Describing the longitudinal course of major depression using Markov models: data integration across three national surveys

Background

Most epidemiological studies of major depression report period prevalence estimates. These are of limited utility in characterizing the longitudinal epidemiology of this condition. Markov models provide a methodological framework for increasing the utility of epidemiological data. Markov models relating incidence and recovery to major depression prevalence have been described in a series of prior papers. In this paper, the models are extended to describe the longitudinal course of the disorder.

Methods

Data from three national surveys conducted by the Canadian national statistical agency (Statistics Canada) were used in this analysis. These data were integrated using a Markov model. Incidence, recurrence and recovery were represented as weekly transition probabilities. Model parameters were calibrated to the survey estimates.

Results

The population was divided into three categories: low, moderate and high recurrence groups. The size of each category was approximated using lifetime data from a study using the WHO Mental Health Composite International Diagnostic Interview (WMH-CIDI). Consistent with previous work, transition probabilities reflecting recovery were high in the initial weeks of the episodes, and declined by a fixed proportion with each passing week.

Conclusion

Markov models provide a framework for integrating psychiatric epidemiological data. Previous studies have illustrated the utility of Markov models for decomposing prevalence into its various determinants: incidence, recovery and mortality. This study extends the Markov approach by distinguishing several recurrence categories.

The relative thermal stability of tissue macromolecules and cellular structure in burn injury

When tissue is subjected to higher than physiological temperatures, protein and cell organelle structures can be altered resulting in cell death and subsequent tissue necrosis. A burn injury can be stratified into three main zones, coagulation, stasis and edema, which correlate with the extent of heat exposure and thermal properties of the tissue. While there has been considerable effort to characterize the time-temperature dependence of the injury, relatively little attention has been paid to the other important variable, the thermal susceptibility of the tissue. In the present study, we employ a standard physical chemistry approach to predict the level of denaturation at supraphysiological temperatures of 12 vital proteins as well as RNA, DNA and cell membrane components. Melting temperatures and unfolding enthalpies of the cellular components are used as input experimental parameters. This approach allows us to establish a relation between the level of denaturation of critical cellular components and clinical manifestations of the burn through the characteristic zones of the injury. Specifically, we evaluate the degree of molecular alteration for characteristic temperature profiles at two different depths (Mid-Dermis and Dermis-Fat interface) of 80 degrees C; 20s contact burn. The results of this investigation suggest that the thermal alteration of the plasma membrane is likely the most significant cause of the tissue necrosis. The lipid bilayer and membrane-bound ATPases show a high probability of thermal damage (almost 100% for the former and 85% for the latter) for short heat exposure times. These results suggest that strategies to minimize the damage in a burn injury might focus on the stabilization of the cellular membrane and membrane-bound ATPases. Further work will be required to validate these predictions in an in vivo model.

Risk assessment for inherited susceptibility to cancer: a review of the psychosocial and ethical dimensions

The objective of this study was to conduct a broad-based systematic review of social, ethical, and legal considerations associated with genetic cancer risk assessment technologies (CaRATs). This paper focuses on psychosocial and ethical issues. Search results were limited to papers published in English, French, or German from January, 1990, to May, 2003. A quality assessment tool was developed and applied to retrieved papers. Application of the quality assessment tool resulted in 77 of 247 qualitative and quantitative primary research papers being reviewed and synthesized. A broad range of issues were addressed and grouped into content areas. Despite a large literature addressing psychosocial and ethical issues associated with CaRATs, many existing studies are not adequate to inform decision-makers and stakeholders. Careful policy analysis, as in some of the economic analyses reviewed here, is important to bridge this gap.

Reappraisal of left-sided gallbladder and its accompanying anomalies: a report of two cases and literature review

We report two cases of coexistent left-sided gallbladder and right-sided ligamentum teres with portal vein anomalies documented by magnetic resonance imaging (MRI) and three-dimensional (3D) computed tomography during arterial portography (CTAP). Reformatted 3D MR and CTAP images provide an informative illustration of the accompanying portal vein anomalies. This important anatomical information is useful in preoperative work-up of hepatobiliary surgery.

Endometrial stromal sarcoma mimicking submucosal myoma protruding to the vagina: MRI findings

A 46-year-old woman complained of persistent abnormal vaginal bleeding over ten days. Her intrauterine device had been removed two years before. Soon after, she suffered from menorrhagia and metrorrhagia. An incidental finding of severe anemia was also noted. In this admission, our initial T2-weighted magnetic resonance imaging (MRI) revealed a well-demarcated mass predominantly in the uterine cavity. The mass was depicted by an isointense signal relative to the myometrium on T1-weighted images, high signal intensity on T2-weighted images, and slightly heterogeneous enhancement on post-contrast images. The patient refused surgery. After two years, follow-up MRI showed a pedunculated mass protruding into the upper third of the vagina with a stalk connecting to the posterior wall of the uterine cavity, simulating submucosal myoma. Histological diagnosis was compatible with low-grade endometrial stromal sarcoma.

Refining estimates of major depression incidence and episode duration in Canada using a Monte Carlo Markov model

BACKGROUND

Serial period prevalence estimates for recurrent diseases such as major depression are available more frequently than fully detailed longitudinal data, but it is difficult to estimate incidence and episode duration from such data. Incidence and episode duration are critical decision modeling parameters for recurrent diseases.

OBJECTIVES

To reduce bias that would otherwise occur in national incidence and duration-of-episode estimates for major depressive episodes deriving from studies using serial period prevalence data and to illustrate a methodological approach for the estimation of incidence from such studies.

METHODS

Monte Carlo simulation was applied to a Markov process describing incidence and recovery from major depressive episodes.

RESULTS

The annual incidence and episode duration were found to be 3.1% and 17.1 weeks, respectively. These estimates are expected to be less subject to bias than those generated without modeling.

CONCLUSIONS

These results highlight the usefulness of Markov models for analysis of longitudinal data. The methods described here may be useful for decision modeling and may be generalizable to other chronic diseases.

Epidemiological theory, decision theory and mental health services research

BACKGROUND

Mathematical models describing the epidemiology of major depression are potentially useful for epidemiological analyses, as decision support tools and in economic analyses. The objective of this project was to develop a Markov model based on epidemiological theory that may be useful for decision analysis and health services research.

METHODS

Longitudinal data from a Canadian national survey, the National Population Health Survey (NPHS), were used. The NPHS has collected longitudinal data on a cohort of 17,262 subjects since 1994. The analysis employed a Markov tunnel in order to model the dependence of recovery probabilities on episode duration.

RESULTS

Episode incidence ranged between 6.2 % per year in women under 35 to 0.26 % in men over the age of 65.A greater proportion of subjects over 35 years old reported episodes lasting more than 26 weeks. The probability of recovery declined with increasing episode duration, independently of sex. Under steady-state assumptions, a Markov model integrating these parameters predicted a point prevalence of approximately 2% in women and 1% in men under the age of 55. In older age groups, the predicted point prevalence declined in both sexes.

CONCLUSIONS

These models support the hypothesis that sex differences in major depression prevalence are due primarily to differences in incidence rather than episode length. These results also indicate that there is no meaningful "central tendency" describing the distribution of episode length in major depression episode. Estimates of mean episode duration represent an intermixing of frequent brief episodes with infrequent protracted episodes. This finding may have important policy implications.

Pathogenicity of Stagonospora nodorum requires malate synthase

A gene encoding malate synthase, a key enzyme of the glyoxylate cycle, has been cloned and characterized in the necrotrophic wheat pathogen Stagonospora nodorum. Expression studies of Mls1 showed high levels of transcript in ungerminated spores whereas malate synthase enzyme activities were low. Expression studies in planta found that Mls1 transcript levels decreased approximately 10-fold upon germination before slowly increasing throughout the remainder of the infection. To characterize Mls1 further, the gene was disrupted in S. nodorum by homologous recombination. In the absence of any supplied carbon source, the mls1 spores were unable to germinate and consequently the mutants were non-pathogenic. Germination and pathogenicity could be restored by the addition of either glucose or sucrose, implying that S. nodorum is reliant upon the catabolism of lipids for infection. Furthermore, analysis of lipid bodies in the mutant strain indicated that lipid mobilization and, consequently, peroxisomal beta-oxidation of fatty acids is delayed or inhibited by the disruption of the glyoxylate cycle. This study has demonstrated for the first time in a fungal phytopathogen the requirement of malate synthase for pathogenicity, suggesting that gluconeogenesis is both dependent on the glyoxylate cycle and required for infection.

Towards a dynamic description of major depression epidemiology

AIMS

The substantial impact of major depression on population health is widely acknowledged. To date, health system responses to this condition have been largely shaped by observational findings. In the future, health policy decisions will benefit from an increasingly integrated and dynamic understanding of the epidemiology of this condition. Policy decisions can also be supported by the development of decision-support tools that can simulate the impact of alternative policy decisions on population health. Markov models are useful both in epidemiological modelling and in decision analysis.

METHODS

In this project, a Markov model describing major depression epidemiology was developed. The model employed a Markov Tunnel in order to depict the dependence of recovery probabilities on episode duration. Transition probabilities, including incidence, recovery and mortality were estimated from Canadian national survey data.

RESULTS

Episode incidence was approximately 3% per year. Recovery rates declined exponentially over time. The model predicted point prevalence at slightly less than 1%, agreeing closely with observed prevalence data.

CONCLUSIONS

Epidemiological models describing the dynamic relationships between major depression incidence, prevalence, recovery and mortality can help to integrate available epidemiological data. Such models offer an attractive option for support of health policy decisions.

Reliability of contemporary radiology to measure tumour size of hepatocellular carcinoma in patients undergoing resection: limitations and clinical implications

BACKGROUND

Preoperative radiology has been widely used to detect and measure hepatocellular carcinoma (HCC). However, its accuracy and reliability are unclear. This study aimed to assess the ability of current radiology to measure tumour size in patients undergoing resection.

METHODS

We evaluated 212 HCC patients undergoing curative resection. Tumour size measured in the pathological examination was correlated with that obtained in preoperative ultrasound (US) and contrast-enhanced dynamic computed tomography (CT). Accuracy and association with tumour recurrence were investigated.

RESULTS

The mean size of the tumour was 4.5 +/- 2.6 cm and was accurate in both US and CT in only 6 (3%) patients. Cirrhosis (P = 0.015), absence of tumour stain (P = 0.002) and small (< or = 4 cm) tumour (P < 0.001) were the significant factors associated with size deviation using both US and CT. Ninety-four (44%) patients developed tumour recurrence within 17 +/- 11 months of resection. Recurrence rate was 52%, 52% and 67% in patients with underestimation in US (relative risk [RR]: 2.0, 95% confidence interval [CI]: 1.2-3.4, P = 0.01), CT (RR: 2.1, 95% CI: 1.1-4, P = 0.022) and both modalities (RR: 2.5, 95% CI: 1.4-4.2, P = 0.001), respectively, compared to 30% recurrence in patients with accurate estimation of tumour size.

CONCLUSION

The accuracy of radiology in measuring tumour size was poor, and may lead to inappropriate treatment. The finding that underestimation of tumour size was associated with a higher tumour recurrence rate is consistent with the hypothesis that HCC may recur from pre-existing tumour foci which could not be identified from the current imaging modalities.

Comparative risk and policy analysis in environmental health

There is increasing interest in the integration of quantitative risk analysis with benefit-cost and cost-effectiveness methods to evaluate environmental health policy making and perform comparative analyses. However, the combined use of these methods has revealed deficiencies in the available methods, and the lack of useful analytical frameworks currently constrains the utility of comparative risk and policy analyses. A principal issue in integrating risk and economic analysis is the lack of common performance metrics, particularly when conducting comparative analyses of regulations with disparate health endpoints (e.g., cancer and noncancer effects or risk-benefit analysis) and quantitative estimation of cumulative risk, whether from exposure to single agents with multiple health impacts or from exposure to mixtures. We propose a general quantitative framework and examine assumptions required for performing analyses of health risks and policies. We review existing and proposed risk and health-impact metrics for evaluating policies designed to protect public health from environmental exposures, and identify their strengths and weaknesses with respect to their use in a general comparative risk and policy analysis framework. Case studies are presented to demonstrate applications of this framework with risk-benefit and air pollution risk analyses. Through this analysis, we hope to generate discussions regarding the data requirements, analytical approaches, and assumptions required for general models to be used in comparative risk and policy analysis.

Health technology assessment, research, and implementation within a health region in Alberta, Canada

OBJECTIVES

To determine the need for and implement health technology assessment (HTA) to inform decision making and policy within a regional health care system in Calgary (Alberta, Canada).

METHODS

Published literature and organizational materials for the Calgary Health Region (CHR) and HTA units worldwide were reviewed. Key individuals within the provincial health ministry (Alberta Health and Wellness), CHR, the University of Calgary (U of C), funding agencies, and HTA organizations were consulted in a structured fashion. A structure for a regional HTA program was developed, taking into account relationships between these organizations.

RESULTS

A locally focused HTA and implementation unit was deemed desirable. The Calgary Health Technology Implementation Unit (CaHTIU) was established. The CaHTIU was designed to efficiently integrate with CHR planning as well as undertake independent research activities. HTA activities focus primarily on CHR needs and are managed by a Health Technology Advisory Committee (HTAC) that consists of CHR management and other key individuals. Working groups contribute to and coordinate HTAs and implementation under the leadership of the unit Director, and include content as well as management individuals. The unit cooperates where appropriate with extant Canadian HTA organizations.

CONCLUSIONS

The Calgary HTA unit is unique in Canada, because it functions within a regional health care system as well as a research institution. Advantages include a local focus in terms of applied HTAs, a systematic process for implementation of recommendations, and a collaborative atmosphere for research within the U of C.

The need for evolution in healthcare decision modeling

STATEMENT OF PROBLEM

Many healthcare decisions are difficult because they are complex and have important consequences such as the impact on survival or quality-of-life of individuals and on allocation of limited resources. The present state-of-the-art in healthcare decision modeling is often inadequate to properly assess these decisions.

METHODS

Based on a literature search and the experience of the authors, typical methodologies used in healthcare decision analysis modeling are explored and compared with methods used in other practices. An example of hormonal therapy decisions is used.

RESULTS

Useful methods that have been developed in other fields are presented. These include methods targeted toward appropriate assessment and representation of the complexity of decisions, assessment of uncertainty, use of nonexpected value decision analysis, and use of multi-attribute decision criteria.

CONCLUSION

The state-of-the-art in healthcare decision modeling can be improved through learning from other practices.

Bifunctional family 3 glycoside hydrolases from barley with alpha -L-arabinofuranosidase and beta -D-xylosidase activity. Characterization, primary structures, and COOH-terminal processing

An alpha-l-arabinofuranosidase and a beta-d-xylosidase, designated ARA-I and XYL, respectively, have been purified about 1,000-fold from extracts of 5-day-old barley (Hordeum vulgare L.) seedlings using ammonium sulfate fractional precipitation, ion exchange chromatography, chromatofocusing, and size-exclusion chromatography. The ARA-I has an apparent molecular mass of 67 kDa and an isoelectric point of 5.5, and its catalytic efficiency during hydrolysis of 4'-nitrophenyl alpha-l-arabinofuranoside is only slightly higher than during hydrolysis of 4'-nitrophenyl beta-d-xyloside. Thus, the enzyme is actually a bifunctional alpha-l-arabinofuranosidase/beta-d-xylosidase. In contrast, the XYL enzyme, which also has an apparent molecular mass of 67 kDa and an isoelectric point of 6.7, preferentially hydrolyzes 4'-nitrophenyl beta-d-xyloside, with a catalytic efficiency approximately 30-fold higher than with 4'-nitrophenyl alpha-l-arabinofuranoside. The enzymes hydrolyze wheat flour arabinoxylan slowly but rapidly hydrolyze oligosaccharide products released from this polysaccharide by (1 --> 4)-beta-d-xylan endohydrolase. Both enzymes hydrolyze (1 --> 4)-beta-d-xylopentaose, and ARA-I can also degrade (1 --> 5)-alpha-l-arabinofuranohexaose. ARA-I and XYL cDNAs encode mature proteins of 748 amino acid residues which have calculated molecular masses of 79.2 and 80.5 kDa, respectively. Both are family 3 glycoside hydrolases. The discrepancies between the apparent molecular masses obtained for the purified enzymes and those predicted from the cDNAs are attributable to COOH-terminal processing, through which about 130 amino acid residues are removed from the primary translation product. The genes encoding the ARA-I and XYL have been mapped to chromosomes 2H and 6H, respectively. ARA-I transcripts are most abundant in young roots, young leaves, and developing grain, whereas XYL mRNA is detected in most barley tissues.

Severe hypokalemia as a cause of acute transient paraplegia following electrical shock

Transient lower extremity paralysis has been previously reported following high voltage electrical injury. The following case report describes an unusual presentation of transient acute flaccid lower extremity paralysis following a high voltage electrical injury associated with profound hypokalemia and acid/base abnormalities similar to the periodic paralysis syndrome. The patient's symptoms resolved with correction of severe hypokalemia. Potential mechanisms for a metabolic neuromuscular disorder induced by electrical injury are proposed.

Biophysical injury mechanisms in electrical shock trauma

Electrical shock trauma tends to produce a very complex pattern of injury, mainly because of the multiple modes of frequency-dependent tissue-field interactions. Historically, Joule heating was thought to be the only cause of electrical injuries to tissue by commercial-frequency electrical shocks. In the last 15 years, biomedical engineering research has improved the understanding of the underlying biophysical injury mechanisms. Besides thermal burns secondary to Joule heating, permeabilization of cell membranes and direct electroconformational denaturation of macromolecules such as proteins have also been identified as tissue-damage mechanisms. This review summarizes the physics of tissue injury caused by contact with commercial-frequency power lines, as well as exposure to lightning and radio frequency (RF), microwave, and ionizing radiation. In addition, we describe the anatomic patterns of the resultant tissue injury from these modes of electromagnetic exposures.