Expansions to the MGDrivE suite for simulating the efficacy of novel gene-drive constructs in the control of mosquito-borne diseases

OBJECTIVE

The MGDrivE (MGDrivE 1 and MGDrivE 2) modeling framework provides a flexible and expansive environment for testing the efficacy of novel gene-drive constructs for the control of mosquito-borne diseases. However, the existing model framework did not previously support several features necessary to simulate some types of intervention strategies. Namely, current MGDrivE versions do not permit modeling of small molecule inducible systems for controlling gene expression in gene drive designs or the inheritance patterns of self-eliminating gene drive mechanisms.

RESULTS

Here, we demonstrate a new MGDrivE 2 module that permits the simulation of gene drive strategies incorporating small molecule-inducible systems and self-eliminating gene drive mechanisms. Additionally, we also implemented novel sparsity-aware sampling algorithms for improved computational efficiency in MGDrivE 2 and supplied an analysis and plotting function applicable to the outputs of MGDrivE 1 and MGDrivE 2.

Genetic conversion of a split-drive into a full-drive element

The core components of CRISPR-based gene drives, Cas9 and guide RNA (gRNA), either can be linked within a self-contained single cassette (full gene-drive, fGD) or be provided in two separate elements (split gene-drive, sGD), the latter offering greater control options. We previously engineered split systems that could be converted genetically into autonomous full drives. Here, we examine such dual systems inserted at the spo11 locus that are recoded to restore gene function and thus organismic fertility. Despite minimal differences in transmission efficiency of the sGD or fGD drive elements in single generation crosses, the reconstituted spo11 fGD cassette surprisingly exhibits slower initial drive kinetics than the unlinked sGD element in multigenerational cage studies, but then eventually catches up to achieve a similar level of final introduction. These unexpected kinetic behaviors most likely reflect differing transient fitness costs associated with individuals co-inheriting Cas9 and gRNA transgenes during the drive process.

Close-kin mark-recapture methods to estimate demographic parameters of mosquitoes

Close-kin mark-recapture (CKMR) methods have recently been used to infer demographic parameters such as census population size and survival for fish of interest to fisheries and conservation. These methods have advantages over traditional mark-recapture methods as the mark is genetic, removing the need for physical marking and recapturing that may interfere with parameter estimation. For mosquitoes, the spatial distribution of close-kin pairs has been used to estimate mean dispersal distance, of relevance to vector-borne disease transmission and novel biocontrol strategies. Here, we extend CKMR methods to the life history of mosquitoes and comparable insects. We derive kinship probabilities for mother-offspring, father-offspring, full-sibling and half-sibling pairs, where an individual in each pair may be a larva, pupa or adult. A pseudo-likelihood approach is used to combine the marginal probabilities of all kinship pairs. To test the effectiveness of this approach at estimating mosquito demographic parameters, we develop an individual-based model of mosquito life history incorporating egg, larva, pupa and adult life stages. The simulation labels each individual with a unique identification number, enabling close-kin relationships to be inferred for sampled individuals. Using the dengue vector Aedes aegypti as a case study, we find the CKMR approach provides unbiased estimates of adult census population size, adult and larval mortality rates, and larval life stage duration for logistically feasible sampling schemes. Considering a simulated population of 3,000 adult mosquitoes, estimation of adult parameters is accurate when ca. 40 adult females are sampled biweekly over a three month period. Estimation of larval parameters is accurate when adult sampling is supplemented with ca. 120 larvae sampled biweekly over the same period. The methods are also effective at detecting intervention-induced increases in adult mortality and decreases in population size. As the cost of genome sequencing declines, CKMR holds great promise for characterizing the demography of mosquitoes and comparable insects of epidemiological and agricultural significance.

Extracellular volume fraction by computed tomography predicts long-term prognosis among patients with cardiac amyloidosis

Objective

This study sought to investigate the association of extracellular volume fraction by computed tomography (ECVCT), myocardial remodeling and mortality in patients with systemic amyloidosis.

Background

Light chain (AL) and transthyretin (ATTR) amyloid fibrils are deposited in the extracellular space of the myocardium, resulting in heart failure and premature mortality. Extracellular expansion can be quantified by CT, offering a rapid and cost-effective alternative to cardiovascular magnetic resonance (CMR), especially among patients with cardiac devices or on renal dialysis.

Methods

Patients with confirmed systemic amyloidosis and varying degrees of cardiac involvement underwent ECG-gated cardiac CT. ECVCT was analysed in the inter-ventricular septum. All patients also underwent clinical assessment, ECG, echocardiography, serum amyloid protein component (SAP) and/or technetium-99m (99mTc) 3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy. ECVCT was compared across different extents of cardiac infiltration (ATTR Perugini Grade / AL Mayo Class) and evaluated for its association with myocardial remodelling and all-cause mortality.

Results

72 patients were studied (AL n=35, ATTR n=37; age 67 (59–76) years, 71% males). Mean septal ECVCT was 42.7±13.1% and 55.8±10.9% in AL and ATTR, respectively, and correlated with indexed left ventricular (LV) mass (r=0.426, p<0.001), LV ejection fraction [LVEF, (r=0.460, p<0.001)], NT-proBNP (r=0.563, p<0.001) and hsTnT (r=0.546, p=0.02). ECVCT increased with cardiac amyloid involvement in both AL and ATTR (Figure 1). Over a mean follow-up of 5.3±2.4 years, 40 deaths occurred (AL 14 [35%]; ATTR 26 [65%]). ECVCT was independently associated with all-cause mortality in ATTR (not AL) after adjustment for age and IV septal wall thickness (HR: 1.046, 95% CI: 1.003–1.090, p=0.037).

Conclusion

Cardiac amyloid burden quantified by ECVCT is associated with adverse cardiac remodelling as well as all-cause mortality among ATTR amyloid patients. ECVCT may address the need for better identification and risk stratification of amyloid patients, using a widely-accessible imaging modality (Figure 2).

Funding Acknowledgement

Type of funding sources: None.

Reversing insecticide resistance with allelic-drive in Drosophila melanogaster

A recurring target-site mutation identified in various pests and disease vectors alters the voltage gated sodium channel (vgsc) gene (often referred to as knockdown resistance or kdr) to confer resistance to commonly used insecticides, pyrethroids and DDT. The ubiquity of kdr mutations poses a major global threat to the continued use of insecticides as a means for vector control. In this study, we generate common kdr mutations in isogenic laboratory Drosophila strains using CRISPR/Cas9 editing. We identify differential sensitivities to permethrin and DDT versus deltamethrin among these mutants as well as contrasting physiological consequences of two different kdr mutations. Importantly, we apply a CRISPR-based allelic-drive to replace a resistant kdr mutation with a susceptible wild-type counterpart in population cages. This successful proof-of-principle opens-up numerous possibilities including targeted reversion of insecticide-resistant populations to a native susceptible state or replacement of malaria transmitting mosquitoes with those bearing naturally occurring parasite resistant alleles.

Insecticide resistance (IR) poses a major global health challenge. Here, the authors generate common IR mutations in laboratory Drosophila strains and use a CRISPR-based allelic-drive to replace an IR allele with a susceptible wild-type counterpart, providing a potent new tool for vector control.

Exploiting a Y chromosome-linked Cas9 for sex selection and gene drive

CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes. However, in species with heterogametic sex chromsomes (e.g. XY, ZW), sex linkage of endonucleases could be beneficial to drive the expression in a sex-specific manner to produce genetic sexing systems, sex ratio distorters, or even sex-specific gene drives, for example. To explore this possibility, here we develop a transgenic line of Drosophila melanogaster expressing Cas9 from the Y chromosome. We functionally characterize the utility of this strain for both sex selection and gene drive finding it to be quite effective. To explore its utility for population control, we built mathematical models illustrating its dynamics as compared to other state-of-the-art systems designed for both population modification and suppression. Taken together, our results contribute to the development of current CRISPR genetic control tools and demonstrate the utility of using sex-linked Cas9 strains for genetic control of animals.

Suppressing mosquito populations with precision guided sterile males

The mosquito Aedes aegypti is the principal vector for arboviruses including dengue/yellow fever, chikungunya, and Zika virus, infecting hundreds of millions of people annually. Unfortunately, traditional control methodologies are insufficient, so innovative control methods are needed. To complement existing measures, here we develop a molecular genetic control system termed precision-guided sterile insect technique (pgSIT) in Aedes aegypti. PgSIT uses a simple CRISPR-based approach to generate flightless females and sterile males that are deployable at any life stage. Supported by mathematical models, we empirically demonstrate that released pgSIT males can compete, suppress, and even eliminate mosquito populations. This platform technology could be used in the field, and adapted to many vectors, for controlling wild populations to curtail disease in a safe, confinable, and reversible manner.

A. aegypti is the principal vector for arboviruses that impact on human health and wellbeing. Here the authors use precision guided sterile insect technique—pgSIT—to suppress or eliminate mosquito populations in multigeneration cage experiments.

MGDrivE 2: A simulation framework for gene drive systems incorporating seasonality and epidemiological dynamics

Interest in gene drive technology has continued to grow as promising new drive systems have been developed in the lab and discussions are moving towards implementing field trials. The prospect of field trials requires models that incorporate a significant degree of ecological detail, including parameters that change over time in response to environmental data such as temperature and rainfall, leading to seasonal patterns in mosquito population density. Epidemiological outcomes are also of growing importance, as: i) the suitability of a gene drive construct for release will depend on its expected impact on disease transmission, and ii) initial field trials are expected to have a measured entomological outcome and a modeled epidemiological outcome. We present MGDrivE 2 (Mosquito Gene Drive Explorer 2): a significant development from the MGDrivE 1 simulation framework that investigates the population dynamics of a variety of gene drive architectures and their spread through spatially-explicit mosquito populations. Key strengths and fundamental improvements of the MGDrivE 2 framework are: i) the ability of parameters to vary with time and induce seasonal population dynamics, ii) an epidemiological module accommodating reciprocal pathogen transmission between humans and mosquitoes, and iii) an implementation framework based on stochastic Petri nets that enables efficient model formulation and flexible implementation. Example MGDrivE 2 simulations are presented to demonstrate the application of the framework to a CRISPR-based split gene drive system intended to drive a disease-refractory gene into a population in a confinable and reversible manner, incorporating time-varying temperature and rainfall data. The simulations also evaluate impact on human disease incidence and prevalence. Further documentation and use examples are provided in vignettes at the project’s CRAN repository. MGDrivE 2 is freely available as an open-source R package on CRAN (https://CRAN.R-project.org/package=MGDrivE2). We intend the package to provide a flexible tool capable of modeling gene drive constructs as they move closer to field application and to infer their expected impact on disease transmission.

Malaria, dengue and other mosquito-borne diseases continue to pose a major global health burden through much of the world. Currently available tools, such as insecticides and antimalarial drugs, are not expected to be sufficient to eliminate these diseases from highly-endemic areas, hence there is interest in novel strategies including genetics-based approaches. In recent years, the advent of CRISPR-based gene-editing has greatly expanded the range of genetic control tools available, and MGDrivE 1 (Mosquito Gene Drive Explorer 1) was proposed to simulate the dynamics of these systems through spatially-structured mosquito populations. As the technology has advanced and potential field trials are being discussed, models are now needed that incorporate additional details, such as life history parameters that respond to daily and seasonal environmental fluctuations, and transmission of pathogens between mosquito and vertebrate hosts. Here, we present MGDrivE 2, a gene drive simulation framework that significantly improves upon MGDrivE 1 by addressing these modeling needs. MGDrivE 2 has also been reformulated as a stochastic Petri net, enabling model specification to be decoupled from simulation, making it easier to adapt the model for application to other insect and mammalian species.

Inherently confinable split-drive systems in Drosophila

CRISPR-based gene-drive systems, which copy themselves via gene conversion mediated by the homology-directed repair (HDR) pathway, have the potential to revolutionize vector control. However, mutant alleles generated by the competing non-homologous end-joining (NHEJ) pathway, resistant to Cas9 cleavage, can interrupt the spread of gene-drive elements. We hypothesized that drives targeting genes essential for viability or reproduction also carrying recoded sequences that restore endogenous gene functionality should benefit from dominantly-acting maternal clearance of NHEJ alleles combined with recessive Mendelian culling processes. Here, we test split gene-drive (sGD) systems in Drosophila melanogaster that are inserted into essential genes required for viability (rab5, rab11, prosalpha2) or fertility (spo11). In single generation crosses, sGDs copy with variable efficiencies and display sex-biased transmission. In multigenerational cage trials, sGDs follow distinct drive trajectories reflecting their differential tendencies to induce target chromosome damage and/or lethal/sterile mosaic Cas9-dependent phenotypes, leading to inherently confinable drive outcomes.

NHEJ alleles and Cas9 remnants after a gene drive introduction are scientific and public concerns. Here, the authors use split drives with recoded rescue elements to target essential genes and minimize the appearance of NHEJ alleles while also leaving no trace of Cas9.

A confinable home-and-rescue gene drive for population modification

Homing-based gene drives, engineered using CRISPR/Cas9, have been proposed to spread desirable genes throughout populations. However, invasion of such drives can be hindered by the accumulation of resistant alleles. To limit this obstacle, we engineer a confinable population modification home-and-rescue (HomeR) drive in Drosophila targeting an essential gene. In our experiments, resistant alleles that disrupt the target gene function were recessive lethal and therefore disadvantaged. We demonstrate that HomeR can achieve an increase in frequency in population cage experiments, but that fitness costs due to the Cas9 insertion limit drive efficacy. Finally, we conduct mathematical modeling comparing HomeR to contemporary gene drive architectures for population modification over wide ranges of fitness costs, transmission rates, and release regimens. HomeR could potentially be adapted to other species, as a means for safe, confinable, modification of wild populations.

Efficient population modification gene-drive rescue system in the malaria mosquito Anopheles stephensi

Cas9/gRNA-mediated gene-drive systems have advanced development of genetic technologies for controlling vector-borne pathogen transmission. These technologies include population suppression approaches, genetic analogs of insecticidal techniques that reduce the number of insect vectors, and population modification (replacement/alteration) approaches, which interfere with competence to transmit pathogens. Here, we develop a recoded gene-drive rescue system for population modification of the malaria vector, Anopheles stephensi, that relieves the load in females caused by integration of the drive into the kynurenine hydroxylase gene by rescuing its function. Non-functional resistant alleles are eliminated via a dominantly-acting maternal effect combined with slower-acting standard negative selection, and rare functional resistant alleles do not prevent drive invasion. Small cage trials show that single releases of gene-drive males robustly result in efficient population modification with ≥95% of mosquitoes carrying the drive within 5-11 generations over a range of initial release ratios.

Active Genetic Neutralizing Elements for Halting or Deleting Gene Drives

CRISPR-Cas9-based gene drive systems possess the inherent capacity to spread progressively throughout target populations. Here we describe two self-copying (or active) guide RNA-only genetic elements, called e-CHACRs and ERACRs. These elements use Cas9 produced in trans by a gene drive either to inactivate the cas9 transgene (e-CHACRs) or to delete and replace the gene drive (ERACRs). e-CHACRs can be inserted at various genomic locations and carry two or more gRNAs, the first copying the e-CHACR and the second mutating and inactivating the cas9 transgene. Alternatively, ERACRs are inserted at the same genomic location as a gene drive, carrying two gRNAs that cut on either side of the gene drive to excise it. e-CHACRs efficiently inactivate Cas9 and can drive to completion in cage experiments. Similarly, ERACRs, particularly those carrying a recoded cDNA-restoring endogenous gene activity, can drive reliably to fully replace a gene drive. We compare the strengths of these two systems.

Modeling confinement and reversibility of threshold-dependent gene drive systems in spatially-explicit Aedes aegypti populations

Background

The discovery of CRISPR-based gene editing and its application to homing-based gene drive systems has been greeted with excitement, for its potential to control mosquito-borne diseases on a wide scale, and concern, for the invasiveness and potential irreversibility of a release. Gene drive systems that display threshold-dependent behavior could potentially be used during the trial phase of this technology, or when localized control is otherwise desired, as simple models predict them to spread into partially isolated populations in a confineable manner, and to be reversible through releases of wild-type organisms. Here, we model hypothetical releases of two recently engineered threshold-dependent gene drive systems—reciprocal chromosomal translocations and a form of toxin-antidote-based underdominance known as UD^MEL—to explore their ability to be confined and remediated.

Results

We simulate releases of Aedes aegypti, the mosquito vector of dengue, Zika, and other arboviruses, in Yorkeys Knob, a suburb of Cairns, Australia, where previous biological control interventions have been undertaken on this species. We monitor spread to the neighboring suburb of Trinity Park to assess confinement. Results suggest that translocations could be introduced on a suburban scale, and remediated through releases of non-disease-transmitting male mosquitoes with release sizes on the scale of what has been previously implemented. UD^MEL requires fewer releases to introduce, but more releases to remediate, including of females capable of disease transmission. Both systems are expected to be confineable to the release site; however, spillover of translocations into neighboring populations is less likely.

Conclusions

Our analysis supports the use of translocations as a threshold-dependent drive system capable of spreading disease-refractory genes into Ae. aegypti populations in a confineable and reversible manner. It also highlights increased release requirements when incorporating life history and population structure into models. As the technology nears implementation, further ecological work will be essential to enhance model predictions in preparation for field trials.

A transcomplementing gene drive provides a flexible platform for laboratory investigation and potential field deployment

CRISPR-based gene drives can spread through wild populations by biasing their own transmission above the 50% value predicted by Mendelian inheritance. These technologies offer population-engineering solutions for combating vector-borne diseases, managing crop pests, and supporting ecosystem conservation efforts. Current technologies raise safety concerns for unintended gene propagation. Herein, we address such concerns by splitting the drive components, Cas9 and gRNAs, into separate alleles to form a trans-complementing split-gene-drive (tGD) and demonstrate its ability to promote super-Mendelian inheritance of the separate transgenes. This dual-component configuration allows for combinatorial transgene optimization and increases safety by restricting escape concerns to experimentation windows. We employ the tGD and a small-molecule-controlled version to investigate the biology of component inheritance and resistant allele formation, and to study the effects of maternal inheritance and impaired homology on efficiency. Lastly, mathematical modeling of tGD spread within populations reveals potential advantages for improving current gene-drive technologies for field population modification.

Workplace substance abuse prevention and help seeking: comparing team-oriented and informational training

Employees fail to seek help for alcohol or drug (AOD) abuse because of unhealthy work climates, stigma, and distrust in Employee Assistance Programs (EAPs). To address such problems, the authors randomly assigned groups of municipal employees (N = 260) to 2 types of training: a 4-hr informational review of EAPs and policy and an 8-hr training that embedded messages about AOD reduction in the context of team building and stress management. Pre- and posttraining and 6-month follow-up surveys assessed change. Group privacy regulation, EAP trust, help seeking, and peer encouragement increased for team training. Stigma of substance users decreased for information training. EAP/policy knowledge increased for both groups. A control group showed little change. Help seeking and peer encouragement also predicted EAP utilization. Integrating both team and informational training may be the most effective for improving help seeking and EAP utilization.

A comparison of patients with different types of syndactyly

We performed a retrospective review of finger syndactyly releases at Shriners Hospital for Children, Houston Unit, between January 1983 and January 1993. This study was performed in an attempt to compare the long-term postoperative function in patients after release of syndactyly resulting from Poland's syndrome with that in patients with idiopathic forms of syndactyly. Only patients with one involved hand were included in this study. The contralateral hand was used as a control. Twenty-seven patients with only one hand involved underwent syndactyly release during this period. Of these, 13 patients who underwent a total of 30 syndactyly releases were available for evaluation. For each patient, the type of syndactyly was determined. Each patient was subjected to a detailed physical examination and participated in occupational-therapy modalities. We noted statistically significant differences in function between operated-on and control hands in the Poland's group, whereas operated-on hands affected with idiopathic forms of syndactyly did not demonstrate significantly different function compared with contralateral controls. These data suggest that functional deficits in hands affected by Poland's syndrome are attributable to more than the syndactyly alone. Hands affected by idiopathic forms of syndactyly are likely to have little postoperative functional deficit.

Team awareness for workplace substance abuse prevention: the empirical and conceptual development of a training program

This paper describes the empirical and theoretical development of a workplace training program to help reduce/prevent employee alcohol and drug abuse and enhance aspects of the work group environment that support ongoing prevention. The paper (1) examines the changing social context of the workplace (e.g., teamwork, privacy issues) as relevant for prevention, (2) reviews studies that assess risks and protective factors in employee substance abuse (work environment, group processes, and employee attitudes), (3) provides a conceptual model that focuses on work group processes (enabling, neutralization of deviance) as the locus of prevention efforts, (4) describes an enhanced team-oriented training that was derived from previous research and the conceptual model, and (5) describes potential applications of the program. It is suggested that the research and conceptual model may help prevention scientists to assess the organizational context of any workplace prevention strategy. The need for this team-oriented approach may be greater among employees who experience psychosocial risks such as workplace drinking climates, social alienation, and policies that emphasize deterrence (drug testing) over educative prevention. Limitations of the model are also discussed.

Collaboration for preventing substance abuse in the workplace: modeling research partnerships in prevention

The managed care community and employers have expressed interest in substance abuse prevention, but there has been little consensus about which prevention and health promotion activities are most appropriately provided in the workplace. In the past 5 years, academicians have become increasingly interested in working with healthcare organizations to develop and implement short- and long-term research partnerships. The most helpful prevention research will serve mutual interests and produce mutual benefit. This article presents a preliminary guide to help facilitate greater collaboration among managed behavioral healthcare organizations, employee assistance programs, and health services researchers interested in preventing substance abuse in the workplace. This guide identifies broad objectives, topic areas, critical applications, and assumptions that can guide collaborative efforts in prevention research.

Reliability of the Lichtman classification of Kienböck's disease

The purpose of this study was to establish the interobserver reliability and intraobserver reproducibility of the staging of Kienböck's disease according to Lichtman's classification. Posteroanterior and lateral wrist radiographs of 64 patients with a diagnosis of Kienböck's disease and 10 control subjects were reviewed independently by 4 observers on 2 separate occasions. The reviewers included 3 hand fellowship-trained surgeons and 1 orthopedist who was not fellowship-trained in hand surgery. A stage was assigned to each set of radiographs according to the Lichtman classification. Paired comparisons for reliability among the 4 observers showed an average absolute percentage agreement of 74% and an average paired weighted kappa coefficient of 0.71. Furthermore, all the controls were correctly classified as stage I, which is in accordance with the Lichtman system. With regard to reproducibility, observers duplicated their initial readings 79% of the time with an average weighted kappa coefficient of 0.77. These results indicate substantial reliability and reproducibility of the Lichtman classification for Kienböck's disease.

Employee exposure to coworker substance use and negative consequences: the moderating effects of work group membership

The current study assesses: (1) whether the relationship between individual exposure to coworker substance use and negative consequences resulting from exposure depends on work group membership, and (2) whether group-level characteristics moderate the relationship between exposure and consequences. At the group-level, we assessed occupations involving safety risk or high mobility and social factors of drinking climate and group cohesiveness. We conducted Hierarchical Linear Modeling (HLM) across two samples of municipal employees (ns = 650, 878; n of groups = 50, 49). Our results revealed that groups with higher proportions of jobs involving risk (e.g., machine work) and, to a lesser extent, groups with a higher level of drinking climate were those most vulnerable to consequences under conditions of exposure. Importantly, our findings controlled for individual risk factors (e.g., personal drinking, job stress). Our discussion examines the implications of this study for theory and policy related to workplace substance abuse.

Workplace drinking climate, stress, and problem indicators: assessing the influence of teamwork (group cohesion)

OBJECTIVE

While job-related alcohol use may be associated with problems for drinkers, less is known about the effects of employee drinking on co-workers. We hypothesized that either exposure to co-worker drinking or the presence of a drinking climate would positively correlate with reports of stress and other problems. Following previous research, we also predicted that work group cohesion (or team orientation) would buffer against such problems.

METHOD

Two random samples of municipal employees (Ns = 909 and 1,068) completed anonymous surveys. These assessed individual drinking, co-worker drinking, task-oriented group cohesion, the direct reports of negative consequences due to co-worker substance use, and five problem indicators: job stress, job withdrawal, health problems, and performance (work accidents and absences).

RESULTS

In each sample, drinking climate correlated with stress and withdrawal more so than did reports of individual drinking. Drinking climate and individual job stress were negatively associated with cohesion. ANCOVA results indicated that drinking climate combined with low cohesion resulted in increased vulnerability for all five problems. Moreover, cohesion appeared to attenuate the negative impact of exposure to drinking norms.

CONCLUSIONS

As many as 40% of employees report at least one negative consequence associated with co-worker substance use (alcohol and drugs). Because teamwork may buffer negative effects of drinking climate on co-workers, workplace prevention efforts might be enhanced through a focus on the social environment. These efforts would include team-building and discussions of the impact of co-worker drinking on employee productivity.

Extracorporeal cardiopulmonary life support with heparin-bonded circuitry in the resuscitation of massively injured trauma patients

BACKGROUND

Patients who have massive but potentially survivable injuries frequently die from complications of hypovolemia, hypoxemia, hypothermia, metabolic acidosis, and coagulopathy. Emergency cardiopulmonary bypass has been unsuccessful in preventing such deaths because it involves systemic anticoagulation that exacerbates coagulopathy.

PATIENTS AND METHODS

A simplified extracorporeal cardiopulmonary life support (ECLS) system was assembled consisting of a centrifugal pump head, heat exchanger, membranous oxygenator, percutaneous cannulas, and heparin-bonded circuitry. The entire system has heparin-bonded surfaces. Patients were resuscitated with the system after femoral vein-femoral artery cannulation. ECLS was used to resuscitate massively injured patients who were deteriorating despite maximal conventional therapy.

RESULTS

While receiving maximal conventional therapy, 6 patients developed hypothermia, metabolic acidosis, and coagulopathy causing pulmonary hemorrhaging and hypoxemia from severe underlying lung injuries. ECLS with heparin-bonded circuitry provided cardiopulmonary support and rewarming while physicians addressed coagulopathies and surgical bleeding and assessed survivability. Three patients survived.

CONCLUSIONS

ECLS with heparin-bonded circuitry offers supplemental capability in the resuscitation and cardiopulmonary support of selected massively injured patients while their primary injuries are being evaluated and treated.

The Winner's Group: A Self-Help Group for Homeless Chemically Dependent Persons

The homeless chemically addicted person presents many unique problems that cannot be addressed in standard treatment programs. Homeless clients are difficult to track and are not consistent in follow-up care. The health and mental health conditions found in this population are straining the resources of drug treatment programs, hospitals, the criminal justice system, and social agencies that serve the homeless (Bassuck, 1991). The Winner's Group located in an inner city soup kitchen demonstrates the adaptability and flexibility of nursing practice. The nurses exhibited creativity in developing methods to meet the diverse needs of homeless chemically addicted persons. The goals and objective that were achieved were neither successes nor failures, they were reflections of efforts to make lifestyle changes. Some of those persons responded in a very positive manner, while others continued to deteriorate. An overall desire was to instill a seed of hope and knowledge that there is always a potential for change and that recovery from chemical dependency is possible. Nurses who work with the homeless must be knowledgeable and realistic about the impact and importance of substance abuse. Nontraditional programs that meet the unique needs of a particular setting and a particular population can provide an opportunity to gain access to health care providers.

Lateral and medial epicondylitis

Lateral and medial epicondylitis (tennis elbow) are common pain complaints about the elbow in the adult. Disability from persistent pain and weakness at the elbow lead to surgical correction of the disorder. Complications of surgery arise from the improper diagnosis of the origin of the pain, failure to correct the pathology with the surgical procedure, and resultant profound forearm weakness or elbow instability. Rehabilitation during the postoperative period is critical for successful return to work or sports activity.

Interhospital transport of the patient on extracorporeal cardiopulmonary support

Portable extracorporeal cardiopulmonary support systems have enhanced the resuscitation and support of moribund patients outside of the operating room environment. The literature documents the successful application of emergency cardiopulmonary support within the hospital setting. Clinicians have reported the use of helicopter and ground ambulance to transport patients requiring intraaortic balloon counterpulsation and fixed-wing transport of neonates requiring extracorporeal membrane oxygenation. As medical transport capabilities extend the sphere of tertiary care to outlying medical facilities, there is a role for extracorporeal cardiopulmonary support in the initial stabilization and safe transport of critically ill patients, via air or ground ambulance. Potentially, the early application of life-sustaining technology can lower mortality and morbidity in patients with a survivable pathology. This is a report on the experience with the resuscitation and interhospital transport of patients on extracorporeal cardiopulmonary support.

Considerations for inter-hospital extracorporeal cardiopulmonary support resuscitation and transport

The availability of commercial, pre-packaged extracorporeal cardiopulmonary support (ECPS) circuits, which are simplified for rapid set-up and priming, has made the intra-hospital resuscitation of moribund patients routine. The successful utilization of this technology in the emergent setting requires planning and the coordination of personnel familiar with the technology. Many issues must be addressed when a patient requiring life-sustaining support utilizing this technology at an outlying hospital, must be transported while on ECPS. After reducing the size and weight of the ECPS cart and obtaining Federal Aviation Administration approval for use during aeromedical transport, the Emanuel Hospital Mobile Surgical Transport Team (MSTT) was able to extend the use of emergency cardiopulmonary bypass to outlying medical facilities. The patients selected for transport, using ECPS, are a group of patients with a potentially survivable pathology unlikely to survive inter-hospital transport without such measures. This report describes our experience with inter-hospital transport of patients on ECPS with special emphasis on transport considerations.

Power staple fixation in trapeziometacarpal arthrodesis

Twenty-seven trapeziometacarpal arthrodeses were performed in 26 patients for basilar thumb joint arthritis utilizing power staple fixation. Short arm thumb spica cast immobilization was maintained for an average of 8 weeks, followed by part-time splintage for 6-12 weeks. Twenty patients were available for evaluation an average of 19 months after the operation. All of the patients were satisfied with the procedure. Thirteen had complete relief of pain, four had mild pain, and three had moderate pain after surgery. The two nonunions that occurred were in patients that refused postoperative casting and both had complete pain relief. There were no fixation-related complications in the remaining 18 patients that were casted postoperatively, and all developed a solid fusion. Power staple fixation in trapeziometacarpal arthrodesis has a 90% union rate with no long-term fixation related complications.

In vitro validation of color velocity imaging and spectral Doppler for velocity determination

Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow imaging. Using information contained in the two-dimensional B-mode, gray-scale image to determine velocity, CVI offers potential advantages over Doppler color flow imaging methods. In order to be used clinically, velocity determination with CVI must be validated by other current methods. A Doppler string phantom was studied with a Philips CVI ultrasound system. Velocity measurements were obtained by both CVI and duplex Doppler spectral analysis for constant string speeds from 10 to 200 cm/sec, at intervals of 10 cm/sec. Twenty separate estimates were obtained with each method, at each string speed. Linear regression assessed the relationship between estimated and actual string velocities, with CVI and spectral Doppler analysis yielding highly valid results (CVI = -0.713 + 1.000997 x phantom; r 2 = 0.9979). At all string speeds tested, the averaged estimated and the actual velocities for both methods were within the 95% confidence estimates. The range for the CVI 95% confidence limits from the regression line varied from +/-1.07 cm/sec at the lowest speed of 10 cm/sec (11.6%) to +/-7.72 cm/sec at 200 cm/sec (3.87%). Based on in vitro testing, CVI is as accurate as Doppler spectral analysis for the estimation of flow velocity.

Surgical management of chronic medial elbow instability

Chronic medial elbow instability in the active adult working population is a rarely diagnosed entity. Although it is recognized in the professional athlete as a cause of disability, reports in the general population do not exist. Fourteen adult patients with symptomatic chronic medial instability were evaluated from 1982 to 1986. Surgical reconstruction of the medial collateral ligaments was performed with follow-up evaluation averaging two years. Symptomatic complaints, physical examination, and roentgenographic evaluation were recorded preoperatively. Range of motion, postoperative stability, ulnar nerve symptomatology, and activity level were recorded postoperatively. All but one patient reported improved stability of the elbow.

Rigid internal fixation for shoulder arthrodesis

Fifteen patients underwent a shoulder arthrodesis utilizing standard dynamic compression plate fixation, but with limited postoperative immobilization with only an abduction pillow. In each case, the position of the extremity relative to the scapula and trunk was recorded immediately postoperatively, at regular intervals until fusion, and at follow-up evaluations. Thirteen of 15 shoulders fused without change of intraoperative position after an average postoperative period of 4 months. One patient lost position in the early postoperative period secondary to inadequate fixation, but subsequently fused. Another who demonstrated a persistent non-union at 2 1/2 years was subsequently explored and underwent a bone graft. Four patients complained of residual symptomatic hardware, with two requiring surgical removal of the plate and screws. All but one patient were satisfied with the clinical result at follow up. Only two patients were within 5 degrees of the preoperatively determined position of 30 degrees abduction, 30 degrees forward flexion, and 30 degrees internal rotation. However, almost all were able to function satisfactorily. The authors concluded that shoulder arthrodesis utilizing rigid internal fixation without postoperative cast or brace immobilization maximizes patient comfort without compromising the success of arthrodesis. However, control of arm position remains inexact and additional modifications are needed to ensure fusion position and to minimize disability.

Factors relating to the development of respiratory symptoms in coffee process workers

After several cases of occupational asthma had been reported in a coffee processing factory in England, 197 coffee workers representing 80% of the production workforce were studied to determine the factors affecting the development of work related respiratory symptoms of wheeze, cough, and dyspnoea. Two computer administered questionnaires concerning the presence of respiratory symptoms and the occurrence of work related respiratory symptoms were used. Workers underwent skin prick testing to green coffee bean extract (GCB) and 11 common inhalant allergen extracts and bronchial provocation testing with methacholine. The presence of specific immunoglobulin E (IgE) antibodies to GCB and castor bean extract (CAB) were determined by a radioallergosorbent test (RAST). The prevalence of work related respiratory symptoms was 12.7%, bronchial hyperresponsiveness 30%, atopy 54%, positive GCB skin prick test 14.7%, positive GCB RAST 14%, and positive CAB RAST 14.7%. None of the workers was sensitised to fungi present in the factory and the numbers of certain species of fungi, despite being greater than may be found out of doors or in an uncontaminated indoor environment, were fewer than are generally associated with the presence of work related respiratory symptoms among agricultural workers. Storage mites were not isolated. Green coffee bean extract and CAB RAST were significantly correlated using the McNemar test but there was limited allergenic cross reactivity in RAST inhibition studies of the two extracts. The only factors that were significantly and independently associated with work related symptoms were CAB RAST and duration of employment. Bronchial hyperresponsiveness was not independently associated with work related respiratory symptoms. The significant independent associations of bronchial hyperresponsiveness included GCB RAST, duration of employment, and resting forced expiratory volume in one second. Exposure to CAB, a highly potent antigen, may be overriding the effects of other factors such a GCB, atopy, bronchial hyperresponsiveness, and smoking. This study suggests that CAB contamination remains a potential problem in the coffee processing industry and all efforts to eliminate it from the working environment should continue.

Brachial plexus injury associated with chest restraint seatbelt: case report

Rapid deceleration while wearing a lap-shoulder strap seatbelt may result in a traction injury to the brachial plexus on the side of the shoulder strap. Occult vascular injury should be considered in patients with this injury pattern. The deficit will recover after a neuropraxic type injury.

A general practice based survey of bronchial hyperresponsiveness and its relation to symptoms, sex, age, atopy, and smoking

The prevalence and associations of bronchial hyperresponsiveness were investigated in a general practice population. The sample was obtained by using every 12th patient on the practice age-sex register, replacing non-responders with corresponding age and sex matched individuals from up to two further 1 in 12 samples. The response rate was 43%; 366 patients were studied. Doubling concentrations of methacholine were given to a maximum of 32 mg/ml or until a 20% fall in forced expiratory volume in one second (FEV1) occurred (provocation concentration, PC20FEV1). Bronchial hyperresponsiveness was defined arbitrarily as a PC20FEV1 of 2 mg/ml or less (or 11 mumol cumulative dose, PD20FEV1). The prevalence of bronchial hyperresponsiveness was 23%. Bronchial hyperresponsiveness was not associated with age but was more prevalent in women than men (31%:13%). It was also more common in those who had ever wheezed (39%) and in those who had had an attack of rhinitis in the preceding month (45%, p less than 0.1), in atopic individuals (30%), and in smokers (32%), but it was not associated with cough or dyspnoea. There was a positive correlation between PC20FEV1 and resting FEV1 (r = 0.288) and a negative correlation between PC20FEV1 and mean daily peak flow variability (r = -0.356). Stepwise binary logistic regression analysis showed significant independent effects on PC20FEV1 for mean daily peak flow variability, gender, number of positive skin test responses, resting FEV1, and mean histamine skin weal area, but no relation with smoking or mean allergen weal area. The prevalence of bronchial hyperresponsiveness was much higher than the prevalence of diagnosed asthma in the practice in 1984 (4.9%). Analysis of case notes of 169 individuals showed that those with bronchial hyperresponsiveness had not attended the practice more frequently for respiratory complaints during the previous five years.

Failure of trapeziometacarpal arthrodesis with use of the Herbert screw and limited immobilization

Eighteen patients with trapeziometacarpal joint arthritis had arthrodesis with use of the 1.9 mm Herbert screw for internal fixation. Thumb spica cast immobilization was maintained for an average of 8 weeks, followed by thumb spica orthoplast splintage on a part time basis. Fourteen patients had radiographic follow-up an average of 12 months after operation. Seven had union and seven had a nonunion. There were three fixation-related complications and two nonfixation-related complications. Eleven patients had clinical follow-up an average of 12 months after operation. Four patients had no pain, five had mild pain, and two had moderate pain after operation. All had severe pain before operation. All were satisfied with the procedure. Although subgroups of patients had a higher rate of union with bone grafts or with immobilization over 8 weeks, the theory that arthrodesis with 1.9 mm Herbert screws does not require external splintage and allows early mobilization is not supported by this series.

Arthritis of the hand and wrist. Management options for some common arthritic conditions

Many arthritic conditions can affect the small joints of the hand and wrist. An understanding of the disease process helps in managing the problem. Conservative care generally consists of rest, splinting, use of anti-inflammatory drugs, intra-articular injection with corticosteroids, and rehabilitation therapy. Surgical procedures for the arthritic hand are reserved for persistent cases of pain or instability that do not respond to conservative treatment.

Recurrent carotid stenosis: a consequence of local or systemic factors? The influence of unrepaired technical defects

To determine the influence of unrepaired technical defects as well as systemic risk factors for atherogenesis on carotid artery healing after endarterectomy, we conducted a prospective study using intraoperative duplex scanning with spectral analysis to establish the initial status of the artery (N = 131 arteries), and then we studied these vessels at regular postoperative intervals with the same technique (N = 108 arteries, 265 studies). The vessels were divided into the operated and nonoperated segments of the common, internal, and external carotid arteries, and both intraoperative image and flow data were tabulated by artery segment. The technical factors that were analyzed included defect size, defect type, adjacent segment defects, number of defects, shunt use, vessel reopening, and peak, mean, and end-diastolic frequency and velocity. The systemic risk factors studied were sex, hypertension, diabetes, smoking, randomly drawn total serum cholesterol and triglyceride levels, and perioperative aspirin and dextran use. Data were analyzed by linear logistic regression analysis. Among the technical factors, only intraoperative defect size was significantly associated with risk of recurrent stenosis (p = 0.0175). Although any defect size adversely affected the condition of the vessel during follow-up, the magnitude of this effect was small for smaller defects (size category 1: less than or equal to 40% stenosis or flap length less than or equal to 25% of vessel diameter). The systemic factors that were associated with risk of recurrent stenosis were hypertension (p = 0.0002), smoking (p = 0.0016), and randomly drawn total serum cholesterol level (p = 0.0116). The fact that the operated segments consistently fared worse during follow-up than did the nonoperated segments (p = 0.0044) undoubtedly reflects the inevitable trauma of the endarterectomy, but also emphasizes the important contribution of systemic risk factors in recurrent carotid stenosis. Risk factor modification may be the most effective method of ensuring the durability of carotid endarterectomy.

Repairing cuts and lacerations of the hand

Cuts and lacerations of the hand require complete evaluation and care to ensure optimal healing. Contamination must be considered, and x-ray films should be taken to rule out the presence of foreign bodies, fractures, or joint injury in severe wounds. Irrigation and excision of nonviable tissue precede operative closure and graft placement. Puncture, gunshot, and bite wounds are left open to drain, and if necessary, tetanus and antibiotic prophylactic treatment is given. Appropriate immobilization and dressing with follow-up care are critical to the successful outcome of these injuries.

A randomized double blind controlled trial comparing two amoxycillin regimens in the treatment of acute exacerbations of chronic bronchitis

A randomized double blind trial comparing two amoxycillin regimens in the treatment of acute exacerbations of chronic bronchitis was performed. Forty-one patients were entered into the study. Twenty patients received amoxycillin sachets 3g twice daily for three days and 21 patients received amoxycillin capsules 500 mg three times daily for seven days. There was no significant difference between the two groups in terms of duration of hospital admission, reduction in sputum volume, clearance of pus from the sputum or the number of treatment failures. No patient developed unwanted effects from the treatment with high dose amoxycillin. Twenty-eight patients were followed for one year and there was no difference in the number of exacerbations experienced by patients treated with short course high dose therapy compared with low dose therapy. It is concluded that short course high dose amoxycillin may be as effective as conventional course amoxycillin in the treatment of acute exacerbations of chronic bronchitis.

Simple dislocation of the elbow in the adult. Results after closed treatment

The long-term results after treatment of simple dislocation of the elbow in fifty-two adults were evaluated with regard to limitation of motion, pain, instability, and residual neurovascular deficit. All patients were treated with traditional closed reduction, but the duration of immobilization before commencement of active motion varied. Goniometric, photographic, and radiographic data were compiled for these patients, who had an average follow-up of 34.4 months. Despite the generally favorable prognosis for this injury, 60 per cent of the patients reported some symptoms on follow-up. A flexion contracture of more than 30 degrees was documented in 15 per cent of the patients; residual pain, in 45 per cent; and pain on valgus stress, in 35 per cent. Prolonged immobilization after injury was strongly associated with an unsatisfactory result. The longer the immobilization had been, the larger the flexion contracture (p less than 0.001) and the more severe the symptoms of pain were. The results indicate that early active motion is the key factor in rehabilitation of the elbow after a dislocation.

Arthroscopic subacromial decompression. An anatomical study

Anterior acromioplasty as described by Neer has been an effective procedure for shoulder impingement syndrome. Recent presentations by Ellman suggest that an effective acromioplasty may be performed arthroscopically. These clinical reports have not been supported by any laboratory experience. The purpose of our study was to examine the feasibility and attempt to quantitate the results of arthroscopic subacromial decompressions. Six acromioplasties were performed according to the recommended technique of Dr. Neer to create a standard for comparison. Fourteen fresh postmortem specimens were studied. In seven shoulders a standard acromioplasty was performed with an osteotome. In seven shoulders an acromioplasty was performed using standard arthroscopic approaches and motorized instruments. In five shoulders an isolated division of the coracoacromial ligament was performed arthroscopically. The coracoacromial ligament was completely divided in all five cases. In the osteotome group adequate bone was resected in 75% (21/28) measured locations. In the arthroscopic group adequate bone was removed at 86% (24/28) location. This difference is not statistically significant. In the cadaver, anterior acromioplasty was performed effectively and predictably with arthroscopic instruments. This compared favorably to a conventional osteotome acromioplasty. It was concluded that coracoacromial ligament division can be accomplished.

Surgical correction of severe knee pterygium

Knee flexion contracture secondary to a severe pterygium is a disabling condition. Full surgical correction has not been possible because of the sciatic nerve and its terminal branches. Our technique to obtain full correction is to divide the nerve near the neuromuscular junction and bridge the defect with multiple sural nerve cable grafts. Microscopic technique is used.

A comparison of histamine and methacholine bronchial challenges using the DeVilbiss 646 nebulizer and the Rosenthal-French dosimeter

We have compared bronchial challenge with both histamine and methacholine for the tidal breathing method and dosimeter method, using the DeVilbiss 646 nebulizer, in 18 patients with asthma. There was a significant difference between the PC20 FEV1 but not the PD20 FEV1 when either agonist was administered by the different techniques but not by the same method.