Youth Caregivers of Adults in the United States: Prevalence and the Association Between Caregiving and Education

A growing proportion of individuals adopt family caregiving roles. Family caregivers are the primary providers of long-term care in the United States yet limited federal policy supports exist, despite the known negative impacts of caregiving. There is also limited information about the prevalence of youth/young adult caregivers and the impacts of caregiving at formative ages in the United States. Our objective is to estimate the prevalence of youth caregivers and examine the association of caregiving with educational investments. We use the American Time Use Survey (2013-2019) to identify and describe youth caregivers (aged 15-18) and young adult caregivers (aged 19-22) and compare them with non-caregiving peers. We estimate that there are approximately 1,623,000 youth caregivers and 1,986,000 young adult caregivers, corresponding to 9.2% and 12.7% of these age groups, respectively. However, there is a wide range in the estimated prevalence per year, from approximately 364,000 to 2.8 million youth caregivers and from 353,000 to 2.2 million young adult caregivers, depending on caregiver definition. Unlike adult caregivers, we find that young men and women were nearly equally likely to provide care. We also find that non-White individuals are disproportionately represented as youth caregivers. Compared with non-caregiving peers, both youth and young adult caregivers are less likely to be enrolled in school and, among those enrolled in school, spend significantly less time on educational activities. Considering the association of caregiving among youth/young adults and education, policies supporting youth and young adult caregivers are critical.

Nudging During Pediatric Intensive Care Conferences With Family Members: Retrospective Analysis of Transcripts From a Single-Center, 2015-2019

OBJECTIVES

Nudging, a behavioral economics concept, subtly influences decision-making without coercion or limiting choice. Despite its frequent use, the specific application of nudging techniques by clinicians in shared decision-making (SDM) is understudied. Our aim was to analyze clinicians' use of nudging in a curated dataset of family care conferences in the PICU.

DESIGN

Between 2019 and 2020, we retrospectively studied and coded 70 previously recorded care conference transcripts that involved physicians and families from 2015 to 2019. We focused on decision-making discussions examining instances of nudging, namely salience, framing, options, default, endowment, commission, omission, recommend, expert opinion, certainty, and social norms. Nudging instances were categorized by decision type, including tracheostomy, goals of care, or procedures.

SETTING

Single-center quaternary pediatric facility with general and cardiac ICUs.

PATIENTS

None.

INTERVENTIONS

None.

MEASUREMENTS

We assessed the pattern and frequency of nudges in each transcript.

MAIN RESULTS

Sixty-three of the 70 transcripts contained SDM episodes. These episodes represented a total of 11 decision categories based on the subject matter of nudging instances, with 308 decision episodes across all transcripts (median [interquartile range] 5 [4-6] per conference). Tracheostomy was the most frequently discussed decision. A total of 1096 nudging instances were identified across the conferences, with 8 (6-10) nudge types per conference. The most frequent nudging strategy used was gain frame (203/1096 [18.5%]), followed by loss frame (150/1096 [13.7%]).

CONCLUSIONS

Nudging is routinely employed by clinicians to guide decision-making, primarily through gain or loss framing. This retrospective analysis aids in understanding nudging in care conferences: it offers insight into potential risks and benefits of these techniques; it highlights ways in which their application has been used by caregivers; and it may be a resource for future trainee curriculum development.

Self-identified rurality in a nationally representative population in the US

INTRODUCTION

In the US, health services research most often relies on Rural-Urban Commuting Area (RUCA) classification codes to measure rurality. This measure is known to misrepresent rurality and does not rely on individual experiences of rurality associated with healthcare inequities. We aimed to determine a patient-centered RUCA-based definition of rurality.

METHODS

In this cross-sectional study, we conducted an online survey asking US residents, 'Do you live in a rural area?' and the rationale for their answer. We evaluated the concordance between their self-identified rurality and their ZIP code-derived RUCA designation of rurality by calculating Cohen's kappa (κ) statistic and percent agreement.

RESULTS

Of the 774 participants, 456 (58.9%) and 318 (41.1%) individuals had conventional urban and rural RUCA classifications, respectively. There was only moderate agreement between perceived rurality and rural RUCA classification (κ=0.48; 95% confidence interval (CI)=0.42-0.54). Among people living within RUCA 2-3 defined urban areas (n=51), percent agreement was only 19.6%. Discordance was driven by their perception of the population density, proximity to the nearest neighbor, proximity to a metropolitan area, and the number of homes in their area. Based on our results, we reclassified RUCA 2-3 designations as rural, resulting in an increase in overall concordance (κ=0.56; 95%CI=0.50-0.62).

DISCUSSION

Patient-centered rural-urban classification is required to effectively evaluate the impact of rurality on health disparities. This study presents a more patient-centric RUCA-based classification of rurality that can be easily operationalized in future research in situations in which self-reported rural status is missing or challenging to obtain.

CONCLUSION

Reclassification of RUCA 2-3 as rural represents a more patient-centric definition of rurality.

Education for Tobacco Use Disorder Treatment: Current State, Evidence, and Unmet Needs

Background

Tobacco use is undertreated in the medical setting. One driver may be inadequate tobacco use disorder treatment (TUDT) training for clinicians in specialties treating tobacco-dependent patients.

Objective

We sought to evaluate the current state of TUDT training for diverse professionals and how these skills are assessed in credentialing exams.

Methods

We performed a focused review of current educational practices, evidence-based strategies, and accreditation exam contents focused on TUDT.

Results

Among medical students, participants in reviewed studies reported anywhere from 45 minutes to 3 hours of TUDT training throughout their 4-year programs, most often in the form of didactic sessions. Similarly, little TUDT training was reported at the post-graduate (residency, fellowship, continuing medical education) levels, and reported training was typically delivered as time-based (expected hours of instruction) rather than competency-based (demonstration of mastery) learning. Multiple studies evaluated effective TUDT curricula at varied stages of training. More effective curricula incorporated longitudinal sessions and active learning, such as standardized patient encounters or proctored patient visits. Knowledge of TUDT is minimally evaluated on certification exams. For example, the American Board of Internal Medicine blueprint lists TUDT as <2% of one subtopic on both the internal medicine and pulmonary exams.

Conclusion

TUDT training for most clinicians is minimal, does not assess competency, and is minimally evaluated on certification exams. Effective, evidence-based TUDT training incorporating active learning should be integrated into medical education at all levels, with attention paid to inclusion on subsequent certifying exams.

Accuracy of Expected Symptoms and Subsequent Quality of Life Measures Among Adults With COPD

Importance

Patients' expectations for future health guide their decisions and enable them to prepare, adapt, and cope. However, little is known about how inaccurate expectations may affect patients' illness outcomes.

Objective

To assess the association between patients' expectation inaccuracies and health-related quality of life.

Design, Setting, and Participants

This cohort study of patients with severe chronic obstructive pulmonary disease (COPD) was conducted from 2017 to 2021, which included a 24-month follow-up period. Eligible participants received outpatient primary care at pulmonary clinics of a single large US health system. Data were analyzed between 2021 and 2023.

Exposure

Expectation accuracy, measured by comparing patients' self-reported expectations of their symptom burden with their actual physical and emotional symptoms 3, 12, and 24 months in the future.

Main Outcome and Measure

Health-related quality of life, measured by the St George's Respiratory Questionnaire-COPD at 3, 12, and 24 months.

Results

A total of 207 participants were included (median age, 65.5 years [range, 42.0-86.0 years]; 120 women [58.0%]; 118 Black [57.0%], 79 White [38.2%]). The consent rate among approached patients was 80.0%. Most patients reported no or only limited discussions of future health and symptom burdens with their clinicians. Across physical and emotional symptoms and all 3 time points, patients' expectations were more optimistic than their experiences. There were no consistent patterns of measured demographic or behavioral characteristics associated with expectation accuracy. Regression models revealed that overoptimistic expectations of future burdens of dyspnea (linear regression estimate, 4.68; 95% CI, 2.68 to 6.68) and negative emotions (linear regression estimate, -3.04; 95% CI, -4.78 to 1.29) were associated with lower health-related quality of life at 3 months after adjustment for baseline health-related quality of life, forced expiratory volume over 1 second, and interval clinical events (P < .001 for both). Similar patterns were observed at 12 months (dyspnea: linear regression estimate, 2.41; 95% CI, 0.45 to 4.37) and 24 months (negative emotions: linear regression estimate, -2.39; 95% CI, -4.67 to 0.12; dyspnea: linear regression estimate, 3.21; 95% CI, 0.82 to 5.60), although there was no statistically significant association between expectation of negative emotions and quality of life at 12 months.

Conclusions and Relevance

In this cohort study of patients with COPD, we found that patients are overoptimistic in their expectations about future negative symptom burdens, and such inaccuracies were independently associated with worse well-being over time. Developing and implementing strategies to improve patients' symptom expectations may improve patient-centered outcomes.

Associations of Race With Sedation Depth Among Mechanically Ventilated Adults: A Retrospective Cohort Study

OBJECTIVES

To evaluate the association of race with proportion of time in deep sedation among mechanically ventilated adults.

DESIGN

Retrospective cohort study from October 2017 to December 2019.

SETTING

Five hospitals within a single health system.

PATIENTS

Adult patients who identified race as Black or White who were mechanically ventilated for greater than or equal to 24 hours in one of 12 medical, surgical, cardiovascular, cardiothoracic, or mixed ICUs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The exposure was White compared with Black race. The primary outcome was the proportion of time in deep sedation during the first 48 hours of mechanical ventilation, defined as Richmond Agitation-Sedation Scale values of -3 to -5. For the primary analysis, we performed mixed-effects linear regression models including ICU as a random effect, and adjusting for age, sex, English as preferred language, body mass index, Elixhauser comorbidity index, Laboratory-based Acute Physiology Score, Version 2, ICU admission source, admission for a major surgical procedure, and the presence of septic shock. Of the 3337 included patients, 1242 (37%) identified as Black, 1367 (41%) were female, and 1002 (30%) were admitted to a medical ICU. Black patients spent 48% of the first 48 hours of mechanical ventilation in deep sedation, compared with 43% among White patients in unadjusted analysis. After risk adjustment, Black race was significantly associated with more time in early deep sedation (mean difference, 5%; 95% CI, 2-7%; p < 0.01).

CONCLUSIONS

There are disparities in sedation during the first 48 hours of mechanical ventilation between Black and White patients across a diverse set of ICUs. Future work is needed to determine the clinical significance of these findings, given the known poorer outcomes for patients who experience early deep sedation.

Comparing Smoking Cessation Interventions among Underserved Patients Referred for Lung Cancer Screening: A Pragmatic Trial Protocol

Smoking burdens are greatest among underserved patients. Lung cancer screening (LCS) reduces mortality among individuals at risk for smoking-associated lung cancer. Although LCS programs must offer smoking cessation support, the interventions that best promote cessation among underserved patients in this setting are unknown. This stakeholder-engaged, pragmatic randomized clinical trial will compare the effectiveness of four interventions promoting smoking cessation among underserved patients referred for LCS. By using an additive study design, all four arms provide standard "ask-advise-refer" care. Arm 2 adds free or subsidized pharmacologic cessation aids, arm 3 adds financial incentives up to $600 for cessation, and arm 4 adds a mobile device-delivered episodic future thinking tool to promote attention to long-term health goals. We hypothesize that smoking abstinence rates will be higher with the addition of each intervention when compared with arm 1. We will enroll 3,200 adults with LCS orders at four U.S. health systems. Eligible patients include those who smoke at least one cigarette daily and self-identify as a member of an underserved group (i.e., is Black or Latinx, is a rural resident, completed a high school education or less, and/or has a household income <200% of the federal poverty line). The primary outcome is biochemically confirmed smoking abstinence sustained through 6 months. Secondary outcomes include abstinence sustained through 12 months, other smoking-related clinical outcomes, and patient-reported outcomes. This pragmatic randomized clinical trial will identify the most effective smoking cessation strategies that LCS programs can implement to reduce smoking burdens affecting underserved populations. Clinical trial registered with clinicaltrials.gov (NCT04798664). Date of registration: March 12, 2021. Date of trial launch: May 17, 2021.

Stakeholders' Views on Reducing Psychological Distress in Chronic Obstructive Pulmonary Disease

CONTEXT

Psychological distress is highly prevalent among patients with chronic obstructive pulmonary disease (COPD), the top palliative care priority identified by such patients, and associated with poor outcomes. However, patients with COPD rarely receive care for psychological distress.

OBJECTIVES

To identify the barriers and opportunities to reducing psychological distress among patients with COPD in the specialty pulmonary setting.

METHODS

We conducted semi-structured interviews based on Consolidated Framework for Implementation Research constructs with key stakeholders at two pulmonary clinics, including clinicians, staff, patients, and caregivers. We focused on the relevance, identification, and management of psychological distress in COPD care. We identified emergent patterns and concepts, developed and applied codes to the text, and examined the content in each code to identify key themes.

RESULTS

Thirty-one stakeholders participated in interviews (RR=64.6%). Nearly all pulmonary clinicians felt that psychological well-being was a critical, unmet patient need. Yet, most pulmonary clinicians reported that they lacked sufficient training and available resources to support patients, prioritized physical symptoms and medication management over emotional concerns, and perceived limited cultural support for such efforts in the pulmonary clinic setting. Patient and caregiver participants desired integration and prioritization of care addressing psychological distress into routine pulmonary care.

CONCLUSION

Mitigating psychological distress is a palliative care priority in COPD. Integrating efficient, effective resources, such as tools or programs that address psychological distress, into pulmonary clinic settings serving a high volume of patients with COPD may improve the provision of supportive care to patients typically underserved by specialty palliative care.

Family Presence for Critically Ill Patients During a Pandemic

Family engagement is a key component of high-quality critical care, with known benefits for patients, care teams, and family members themselves. The COVID-19 pandemic led to rapid enactment of prohibitions or restrictions on visitation that now persist, particularly for patients with COVID-19. Reevaluation of these policies in response to advances in knowledge and resources since the early pandemic is critical because COVID-19 will continue to be a public health threat for months to years, and future pandemics are likely. This article reviews rationales and evidence for restricting or permitting family members' physical presence and provides broad guidance for health care systems to develop and implement policies that maximize benefit and minimize risk of family visitation during COVID-19 and future similar public health crises.

Family-Centered Care During the COVID-19 Era

Family support is more, not less, important during crisis. However, during the COVID-19 pandemic, maintaining public safety necessitates restricting the physical presence of families for hospitalized patients. In response, health systems must rapidly adapt family-centric procedures and tools to circumvent restrictions on physical presence. Strategies for maintaining family integrity must acknowledge clinicians' limited time and attention to devote to learning new skills. Internet-based solutions can facilitate the routine, predictable, and structured communication, which is central to family-centered care. But the reliance on technology may compromise patient privacy and exacerbate racial, socioeconomic, and geographic disparities for populations that lack access to reliable internet access, devices, or technological literacy. We provide a toolbox of strategies for supporting family-centered inpatient care during physical distancing responsive to the current clinical climate. Innovations in the implementation of family involvement during hospitalizations may lead to long-term progress in the delivery of family-centered care.

Preferences for Predictive Model Characteristics among People Living with Chronic Lung Disease: A Discrete Choice Experiment

Background. Patients may find clinical prediction models more useful if those models accounted for preferences for false-positive and false-negative predictive errors and for other model characteristics. Methods. We conducted a discrete choice experiment to compare preferences for characteristics of a hypothetical mortality prediction model among community-dwelling patients with chronic lung disease recruited from 3 clinics in Philadelphia. This design was chosen to allow us to quantify "exchange rates" between different characteristics of a prediction model. We provided previously validated educational modules to explain model attributes of sensitivity, specificity, confidence intervals (CI), and time horizons. Patients reported their interest in using prediction models themselves or having their physicians use them. Patients then chose between 2 hypothetical prediction models each containing varying levels of the 4 attributes across 12 tasks. Results. We completed interviews with 200 patients, among whom 95% correctly chose a strictly dominant model in an internal validity check. Patients' interest in predictive information was high for use by themselves (n = 169, 85%) and by their physicians (n = 184, 92%). Interest in maximizing sensitivity and specificity were similar (0.88 percentage points of specificity equivalent to 1 point of sensitivity, 95% CI 0.72 to 1.05). Patients were willing to accept a reduction of 6.10 months (95% CI 3.66 to 8.54) in the predictive time horizon for a 1% increase in specificity. Discussion. Patients with chronic lung disease can articulate their preferences for the characteristics of hypothetical mortality prediction models and are highly interested in using such models as part of their care. Just as clinical care should become more patient centered, so should the characteristics of predictive models used to guide that care.

Effect of Intensivist Communication in a Simulated Setting on Interpretation of Prognosis Among Family Members of Patients at High Risk of Intensive Care Unit Admission: A Randomized Trial

Importance

Discordance about prognosis between a patient's health care decision-making surrogate and the treating intensivist is common in the intensive care unit (ICU). Empowering families, friends, and caregivers of patients who are critically ill to make informed decisions about care is important, but it is unclear how best to communicate prognostic information to surrogates when a patient is expected to die.

Objective

To determine whether family members, who are often health care decision-making surrogates, interpret intensivists as being more optimistic when questions about prognosis in the ICU are answered indirectly.

Design, Setting, and Participants

This web-based randomized trial was conducted between September 27, 2019, and October 17, 2019, among a national sample of adult children, spouses, partners, or siblings of people with chronic obstructive pulmonary disease who were receiving long-term oxygen therapy. Participants were shown video vignettes depicting an intensivist answering a standardized question about the prognosis of a patient at high risk of death on day 3 of ICU admission. Participants were excluded if they had worked as a physician, nurse, or advanced health care practitioner. Data were analyzed from October 18, 2019, to November 12, 2019.

Interventions

Participants were randomized to view 1 of 4 intensivist communication styles in response to the question "What do you think is most likely to happen?": (1) a direct response (control), (2) an indirect response comparing the patient's condition with that of other patients, (3) an indirect response describing the patient's deteriorating physiological condition, or (4) redirection to a discussion of the patient's values and goals.

Main Outcomes and Measures

Participant responses to 2 questions: (1) "If you had to guess, what do you think the doctor thinks is the chance that your loved one will survive this hospitalization?" and (2) "What do you think are the chances that your loved one will survive this hospitalization?" answered using a 0% to 100% probability scale.

Results

Among 302 participants (median [interquartile range] age, 49 [38-59] years; 204 [68%] women) included in the trial, 165 (55%) were adult children of the individual with chronic obstructive pulmonary disease; 77 participants were randomized to view a direct response, 77 participants were randomized to view an indirect response referencing other patients, 68 participants were randomized to view an indirect response referencing physiological condition, and 80 participants were randomized to view a redirection response. Compared with participants who viewed a direct response, participants who viewed an indirect response referencing other patients (β = 10 [95% CI, 1-19]; P = .03), physiological condition (β = 10 [95% CI, 0-19]; P = .04), or redirection to a discussion of the patient's values and goals (β = 19 [95% CI, 10-28]; P < .001) perceived the intensivist to have a significantly more optimistic prognostic estimate.

Conclusions and Relevance

These findings suggest that family members interpret indirect or redirection responses to questions about prognosis in the ICU setting as more optimistic than direct responses.

Trial Registration

ClinicalTrials.gov Identifier: NCT04239209.

What's behind the white coat: Potential mechanisms of physician-attributable variation in critical care

Background

Critical care intensity is known to vary across regions and centers, yet the mechanisms remain unidentified. Physician behaviors have been implicated in the variability of intensive care near the end of life, but physician characteristics that may underlie this association have not been determined.

Purpose

We sought to identify behavioral attributes that vary among intensivists to generate hypotheses for mechanisms of intensivist-attributable variation in critical care delivery.

Methods

We administered a questionnaire to intensivists who participated in a prior cohort study in which intensivists made prognostic estimates. We evaluated the degree to which scores on six attribute measures varied across intensivists. Measures were selected for their relevance to preference-sensitive critical care: a modified End-of-Life Preferences (EOLP) scale, Life Orientation Test–Revised (LOT-R), Jefferson Scale of Empathy (JSE), Physicians' Reactions to Uncertainty (PRU) scale, Collett-Lester Fear of Death (CLFOD) scale, and a test of omission bias. We conducted regression analyses assessing relationships between intensivists’ attribute scores and their prognostic accuracy, as physicians’ prognostic accuracy may influence preference-sensitive decisions.

Results

20 of 25 eligible intensivists (80%) completed the questionnaire. Intensivists’ scores on the EOLP, LOT-R, PRU, CLFOD, and omission bias measures varied considerably, while their responses on the JSE scale did not. There were no consistent associations between attribute scores and prognostic accuracy.

Conclusions

Intensivists vary in feasibly measurable attributes relevant to preference-sensitive critical care delivery. These attributes represent candidates for future research aimed at identifying mechanisms of clinician-attributable variation in critical care and developing effective interventions to reduce undue variation.

Global Sensitivity Analysis of High-Dimensional Neuroscience Models: An Example of Neurovascular Coupling

The complexity and size of state-of-the-art cell models have significantly increased in part due to the requirement that these models possess complex cellular functions which are thought-but not necessarily proven-to be important. Modern cell models often involve hundreds of parameters; the values of these parameters come, more often than not, from animal experiments whose relationship to the human physiology is weak with very little information on the errors in these measurements. The concomitant uncertainties in parameter values result in uncertainties in the model outputs or quantities of interest (QoIs). Global sensitivity analysis (GSA) aims at apportioning to individual parameters (or sets of parameters) their relative contribution to output uncertainty thereby introducing a measure of influence or importance of said parameters. New GSA approaches are required to deal with increased model size and complexity; a three-stage methodology consisting of screening (dimension reduction), surrogate modeling, and computing Sobol' indices, is presented. The methodology is used to analyze a physiologically validated numerical model of neurovascular coupling which possess 160 uncertain parameters. The sensitivity analysis investigates three quantities of interest, the average value of [Formula: see text] in the extracellular space, the average volumetric flow rate through the perfusing vessel, and the minimum value of the actin/myosin complex in the smooth muscle cell. GSA provides a measure of the influence of each parameter, for each of the three QoIs, giving insight into areas of possible physiological dysfunction and areas of further investigation.

Patients' Perspectives on Approaches to Facilitate Completion of Advance Directives

BACKGROUND

Little is understood about the different ways patients complete advance directives (ADs), which is most commonly through lawyers and increasingly using websites.

OBJECTIVE

To understand patients' perspectives on different approaches to facilitating AD completion, the value of legal regulation of ADs, and the use of a web-based platform to create an AD.

DESIGN

Semi-structured interviews with patients.

SETTING/PARTICIPANTS

We purposively sampled 25 patients at least 70 years of age or with a chronic disease from 2 internal medicine clinics.

MEASUREMENTS

Interviews focused on experiences and perspectives creating ADs, including facilitation by lawyers, health-care professionals, and websites. Feedback on a website prototype was also obtained. Responses were analyzed with modified grounded theory until thematic saturation was achieved.

RESULTS

Although a majority of participants with ADs had used lawyers, participants were ambivalent about the benefits of lawyer facilitation. Most valued both the medical perspective of a health-care professional and a lawyer's attention to legal requirements for AD validity. Participants had positive impressions of the web platform, but some were concerned about privacy with online storage. Trust emerged as an overarching theme, and participants valued legal regulation of ADs to ensure document authenticity and delivery of preference-concordant care.

CONCLUSION

Efforts to improve documentation of care planning need to address the disparate methods by which participants complete ADs. Creating options that combine the perceived benefits of a legal approach with greater health professional involvement could appeal to participants. Privacy concerns may limit web use by some patients.

Perspectives on using decision-making nudges in physician-patient communications

Patients engaging in shared decision making must weigh the likelihood of positive and negative outcomes and deal with uncertainty and negative emotions in the situations where desirable options might not be available. The use of "nudges," or communication techniques that influence patients' choices in a predictable direction, may assist patients in making complex decisions. However, nudging patients may be perceived as inappropriate influence on patients' choices. We sought to determine whether key stakeholders, physicians, and laypersons without clinical training consider the use of nudges to be ethical and appropriate in medical decision making. Eighty-nine resident-physicians and 336 Mechanical-Turk workers (i.e., non-clinicians) evaluated two hypothetical preference-sensitive situations, in which a patient with advanced cancer chooses between chemotherapy and hospice care. We varied the following: (1) whether or not the patient's decision was influenced by a mistaken judgment (i.e., decision-making bias) and (2) whether or not the physician used a nudge. Each participant reported the extent to which the communication was ethical, appropriate, and desirable. Both physicians and non-clinicians considered using nudges more positively than not using them, regardless of an initial decision-making bias in patients' considerations. Decomposing this effect, we found that physicians viewed the nudge that endorsed hospice care more favorably than the nudge that endorsed chemotherapy, while non-clinicians viewed the nudge that endorsed chemotherapy more favorably than the nudge that endorsed hospice care. We discuss implications and propose exploring further physicians' and patients' differences in the perception of nudges; the differences may suggest limitations for using nudges in medical decisions.

Numeracy and Understanding of Quantitative Aspects of Predictive Models: A Pilot Study

BACKGROUND

The assessment of user preferences for performance characteristics of patient-oriented clinical prediction models is lacking. It is unknown if complex statistical aspects of prediction models are readily understandable by a general audience.

OBJECTIVE

A pilot study was conducted among nonclinical audiences to determine the feasibility of interpreting statistical concepts that describe the performance of prediction models.

METHODS

We conducted a cross-sectional electronic survey using the Amazon Mechanical Turk platform. The survey instrument included educational modules about predictive models, sensitivity, specificity, and confidence intervals (CIs). Follow-up questions tested participants' abilities to interpret these characteristics with both verbatim and gist knowledge. Objective and subjective numeracy were assessed using previously validated instruments. We also tested understanding of these concepts when embedded in a sample discrete choice experiment task to establish feasibility for future elicitation of preferences using a discrete choice experiment design. Multivariable linear regression was used to identify factors associated with correct interpretation of statistical concepts.

RESULTS

Among 534 respondents who answered all nine questions, the mean correct responses was 95.9% (95% CI, 93.8-97.4) for sensitivity, 93.1% (95% CI, 90.5-95.0) for specificity, and 86.6% (95% CI, 83.3-89.3) for CIs. Verbatim interpretation was high for all concepts, but significantly higher than gist only for CIs (p < 0.001). Scores on each discrete choice experiment tasks were slightly lower in each category. Both objective and subjective numeracy were positively associated with an increased proportion of correct responses (p < 0.001).

CONCLUSION

These results suggest that a nonclinical audience can interpret quantitative performance measures of predictive models with very high accuracy. Future development of patient-facing clinical prediction models can feasibly incorporate patient preferences for model features into their development.

Thinking Forward: Future-oriented Thinking among Patients with Tobacco-associated Thoracic Diseases and Their Surrogates

RATIONALE

The goal of shared decision making is to match patient preferences, including evaluation of potential future outcomes, with available management options. Yet, it is unknown how patients with smoking-related thoracic diseases or their surrogates display future-oriented thinking.

OBJECTIVES

To document prevalent themes in patients' and potential surrogate decision makers' future-oriented thinking when facing preference-sensitive choices.

METHODS

We conducted 44 scenario-based semistructured interviews among a diverse group of outpatients with smoking-associated thoracic diseases and potential surrogates for whom one of three preference-sensitive decisions would be medically relevant. Using content analysis, we documented prevalent themes to understand how these individuals display future-oriented thinking.

MEASUREMENTS AND MAIN RESULTS

Patients and potential surrogates generally expressed expectations for future outcomes but also acknowledged their limitations in doing so. When thinking about potential outcomes, decision makers relied on past experiences, including those only loosely related; perceived familiarity with treatment options; and spirituality. The content of these expectations included effects on family, emotional predictions, and prognostication. For surrogates, a tension existed between hope-based and fact-based expectations.

CONCLUSIONS

Patients and surrogates may struggle to generate expectations, and these future-oriented thoughts may be based on loosely related past experiences or unrealistic optimism. These tendencies may lead to errors, preventing selection of treatments that promote true preferences. Clinicians should explore how decision makers engage in future-oriented thinking and what their expectations are as a component of the shared decision-making process. Future research should evaluate whether targeted guidance in future-oriented thinking may improve outcomes important to patients.

Variability Among US Intensive Care Units in Managing the Care of Patients Admitted With Preexisting Limits on Life-Sustaining Therapies

IMPORTANCE

Although the end-of-life care patients receive is known to vary across nations, regions, and centers, these differences are best explored within a group of patients with presumably similar care preferences.

OBJECTIVE

To examine the proportions of patients admitted to the intensive care unit (ICU) with limitations on life-sustaining treatments and the proportions of such patients who receive aggressive care across individual ICUs.

DESIGN, SETTINGS, AND PARTICIPANTS

Retrospective cohort study using the Project IMPACT database (from April 1, 2001, to December 31, 2008) including 141 ICUs in 105 hospitals in the United States and 277,693 ICU patient visits. We used logistic regression analysis models adjusted for available patient characteristics and clustered visits by individual ICU. The full analysis was last performed in October 2014.

MAIN OUTCOMES AND MEASURES

Outcomes included the provision of (1) cardiopulmonary resuscitation, (2) new forms of life support, and the (3) addition or (4) reversal of treatment limitations.

RESULTS

Of the ICU admissions evaluated, 4.8% (95% CI, 4.7%-4.9%) had previously established treatment limitations. Patients admitted with treatment limitations were more likely to be older with more functional limitations and comorbidities. Among patients who survived to hospital discharge, more experienced reversals of existing treatment limitations during the ICU stay (17.8% [95% CI, 17.0%-18.7%]) than additions of new limits (11.7% [95% CI, 11.1%-12.4%]) (P < .01). Among patients who died, 15.7% (95% CI, 14.7-16.8%) had received cardiopulmonary resuscitation. After risk adjustment, ICUs varied widely in the proportions of patients admitted with treatment limitations (median, 4.0%; range, <1.0%-20.9%), the proportions of those who received cardiopulmonary resuscitation (37.7% [95% CI, 3.8%-92.4%]), the proportions of new forms of life support (30.0% [95% CI, 6.0%-84.2%]), and, among survivors, the proportion who had new treatment limitations established (11.2% [95% CI, 1.9%-57.3%]) and reversal of treatment limitations during or following ICU admission (20.2% [95% CI, 1.8%-76.2%]). The observed variability could not be consistently explained using measurable center-level characteristics.

CONCLUSIONS AND RELEVANCE

Intensive care units vary dramatically in how they manage care for patients admitted with treatment limitations. Among patients who survive, escalations in the aggressiveness of care are more common during the ICU stay than are de-escalations in aggressiveness. This study cannot directly measure whether care received was consistent with patients' preferences but suggests that ICU culture and physicians' practice styles contribute to the aggressiveness of care.

Time-resolved contrast-enhanced MR angiography of spinal vascular malformations

BACKGROUND AND PURPOSE

The diagnosis of spinal vascular malformations may be challenging on conventional MR imaging because neither the location of the signal abnormality in the spinal cord nor the level of the abnormal flow voids correlates with the level of the fistula. We conducted a retrospective evaluation of the utility of using a time-resolved imaging of contrast kinetics sequence in the diagnosis, characterization, and localization of spinal vascular malformations, comparing it with the criterion standard of spinal DSA.

MATERIALS AND METHODS

Fifty-five consecutive patients with a suspected diagnosis of spinal vascular malformation underwent time-resolved imaging of contrast kinetics followed by spinal DSA. All scans were performed on a 1.5T scanner by using a standard 8-channel spine coil and were reported by a neuroradiologist before the DSA was performed.

RESULTS

Forty-seven lesions were confirmed on time-resolved imaging of contrast kinetics and classified as spinal dural arteriovenous fistulas (n = 33, with 1 patient having a type Ib fistula), perimedullary spinal cord arteriovenous fistulas (n = 10), and intramedullary arteriovenous malformations (n = 3). One patient had an extradural spinal vascular malformation. Time-resolved imaging of contrast kinetics identified the location of the arterial feeder to within 1 vertebral level in 27/33 patients (81.8%) with spinal dural arteriovenous fistulas and correctly predicted the side in 22/33 (66.6%) patients. Perimedullary spinal cord arteriovenous fistulas were erroneously considered to represent spinal dural arteriovenous fistulas before spinal DSA. The anatomy of the arterial supply to intramedullary arteriovenous malformations was also poorly characterized on time-resolved contrast-enhanced MR angiography.

CONCLUSIONS

It has been our experience that time-resolved imaging of contrast kinetics is a useful confirmatory tool when a spinal vascular malformation is suspected on the basis of clinical and conventional MR imaging findings. As experience with the technique grows and sequences are refined, it may be possible to rely on time-resolved imaging of contrast kinetics as a screening tool for the diagnosis of spinal vascular malformations.

Endothelium-dependent nitroxyl-mediated relaxation is resistant to superoxide anion scavenging and preserved in diabetic rat aorta

The aim of the study was to investigate whether diabetes-induced oxidant stress affects the contribution of nitroxyl (HNO) to endothelium-dependent relaxation in the rat aorta. Organ bath techniques were employed to determine vascular function of rat aorta. Pharmacological tools (3mM l-cysteine, 5mM 4-aminopyridine (4-AP), 200μM carboxy-PTIO and 100μM hydroxocobalamin, HXC) were used to distinguish between NO and HNO-mediated relaxation. Superoxide anion levels were determined by lucigenin-enhanced chemiluminescence. In the diabetic aorta, where there is increased superoxide anion production, responses to the endothelium-dependent relaxant ACh were not affected when the contribution of NO to relaxation was abolished by either HXC or carboxy-PTIO, indicating a preserved HNO-mediated relaxation. Conversely, when the contribution of HNO was inhibited with l-cysteine or 4-AP, the sensitivity and maximum relaxation to ACh was significantly decreased, suggesting that the contribution of NO was impaired by diabetes. Furthermore, whereas HNO appears to be derived from eNOS in normal aorta, in the diabetic aorta it may also arise from an eNOS-independent source, perhaps derived from nitrosothiol stores. Similarly, exposure to the superoxide anion generator, pyrogallol (100μM) significantly reduced the sensitivity to the NO donor, DEANONOate and ACh-induced NO-mediated relaxation but had no effect on responses to the HNO donor, Angeli's salt and ACh-induced HNO-mediated relaxation in the rat aorta. These findings demonstrate that NO-mediated relaxation is impaired during oxidative stress but the HNO component of relaxation is preserved under those conditions.

Impairment of both nitric oxide-mediated and EDHF-type relaxation in small mesenteric arteries from rats with streptozotocin-induced diabetes

BACKGROUND AND PURPOSE

To investigate whether diabetes affects either or both nitric oxide (NO)-mediated and endothelium-derived hyperpolarizing factor (EDHF)-type relaxation in endothelium-dependent relaxation of mesenteric arteries from streptozotocin-induced diabetic rats.

EXPERIMENTAL APPROACH

Wire myography was employed to examine endothelial function of mesenteric arteries. Superoxide levels were measured by L-012 and lucigenin-enhanced chemiluminescence. Western blotting was used to quantify protein expression levels.

KEY RESULTS

Superoxide levels were significantly increased in diabetic mesenteric arteries compared with normal arteries. Diabetes significantly reduced the sensitivity to the endothelium-dependent relaxant, acetylcholine (ACh) in mesenteric arteries. When the contribution of NO to relaxation was abolished by N-nitro-L-arginine (L-NNA) + a soluble guanylate cyclase inhibitor (ODQ), the sensitivity to ACh was significantly decreased in the diabetic arteries compared with normal arteries, indicating an impaired EDHF-type relaxation despite increased expression of intermediate- and small-conductance calcium-activated potassium channels. Conversely, when the contribution of EDHF was inhibited with TRAM-34 + apamin + iberiotoxin, maximum relaxations to ACh were significantly decreased in diabetic compared with normal arteries, suggesting that the contribution of NO was also impaired by diabetes. Basal levels of NO release, indicated by contraction to L-NNA, were also significantly decreased in diabetic arteries. Western blot analysis demonstrated that diabetic arteries had an increased expression of Nox2, decreased pSer⁴⁷³ Akt and a reduced proportion of endothelial NO synthase (eNOS) expressed as a dimer, indicating uncoupling.

CONCLUSION AND IMPLICATIONS

The contribution of both NO and EDHF-type relaxations was impaired in diabetes and was caused by increased oxidative stress, decreased pSer⁴⁷³ Akt and/or eNOS uncoupling.

Immediate and sustained benefits of a "total" implementation of speech recognition reporting

Speech recognition reporting was introduced in our institution to address the significant delay between report dictation and the appearance of a typed report on the Picture Archiving and Communication System (PACS). We report our experience of a "total" implementation of a speech recognition reporting (SRR) system, which became the sole means of radiology reporting from day 1 of introduction. Prospectively gathered Radiology Information System (RIS) data were examined to determine the monthly mean reporting times and completion times for all studies from January 2004 to February 2006 (11 months before introduction of SRR and 15 months after introduction). Studies were grouped for analysis according to referral source (casualty, general practice, inpatient or outpatient). A large, sustained reduction in time to completion was noted in all referral groups at both hospital sites within our institution (6.79 +/- 0.92 days pre-SRR and 2.20 +/- 0.78 days post-SRR, independent two-sample Student's t-test, p<10(-11)). Workflow was maintained following the introduction of SRR: numbers of reports per month and mean times to report were unchanged. SRR eliminated the delays associated with report transcription and subsequent authorisation, dramatically reducing report turnaround times. Resistance to change has perhaps led to suboptimal implementation of SRR in some other institutions, such that benefits have not been fully realised. Our experience demonstrates the dramatic impact that a well-planned, organisation-wide implementation of SRR can have on radiology service delivery.

Factors contributing to differences in the regulation of cGMP in isolated porcine pulmonary vessels

Guanosine 3',5'-cyclic monophosphate (cGMP) is an important second messenger in many biological systems including vascular smooth muscle where it mediates relaxation. Cellular levels of cGMP are regulated primarily by three enzymes; nitric oxide (NO) synthase, soluble guanylate cyclase, and cGMP-phosphodiesterase. Basal cGMP levels of isolated endothelium intact porcine pulmonary vein are five fold higher than in pulmonary artery. The objective of this study was to investigate possible reasons for this difference. Therefore, we compared NO synthase activity of pulmonary vein with artery and used pharmacologic approaches to compare soluble guanylate cyclase and phosphodiesterase activities in these vessels. NO synthase activities of pulmonary vein and artery were measured by monitoring the conversion of exogenous L-[14C]arginine to L-[14C]citrulline and by quantifying NO formation from endogenous L-arginine. Rates (pM/min per mg protein) of basal L-citrulline and NO formation from endothelium intact pulmonary vein (29.0 +/- 4.8 and 44 +/- 7.1, respectively) were significantly higher than from artery (8.3 +/- 2.2 and 17.1 +/- 3.3). Western blot analysis indicated higher constitutive NO synthase protein in the vein than in artery. N-nitro-L-arginine (0-100 microM), a potent inhibitor of NO synthase, induced contractions of the pulmonary vein which were significantly higher than those of the artery. N-nitro-L-arginine (5 and 20 microM) in the presence of phosphodiesterase inhibitors, decreased basal cGMP levels of endothelium intact blood vessels. In endothelium denuded pulmonary vein and artery, basal cGMP levels were not different from each other, but increased significantly following stimulation of soluble guanylate cyclase with exogenous NO. In the presence of both non-specific and specific cGMP phosphodiesterase inhibitors, exogenous NO-induced cGMP levels of endothelium denuded tissues were not significantly different from each other. However, in the absence of the phosphodiesterase inhibitors, exogenous NO-induced cGMP was significantly less in the artery than in the vein. These results suggest that (I) the intact porcine pulmonary vein contains higher levels of NO synthase activity than pulmonary artery, and that (II) the soluble guanylate cyclase activities in pulmonary vein and artery are equally responsive to NO, and finally (III) pulmonary artery expresses greater phosphodiesterase activity than vein. Higher NO synthase and lower phosphodiesterase activity may explain the greater accumulation of cGMP in the pulmonary vein compared to the artery.

Degranulation enhances release of a stable contractile factor from rabbit polymorphonuclear leukocytes

We investigated the release of a stable contractile factor(s) from rabbit isolated polymorphonuclear leukocytes (PMNs; 10(8) cells/ml) incubated in Tyrode buffer at 37 degrees C. PMNs were untreated, stimulated with N-formylmethionyl-leucyl-phenylalanine (FMLP; 0.1 microM), of degranulated with cytochalasin B (1 microM) in combination with FMLP (0.1 microM). Products from unstimulated PMNs incubated for 60 min caused significantly greater contraction of rabbit isolated aorta (0.56 +/- 0.12 g, n = 8) than did products released from PMNs during a 5-min incubation (0.32 +/- 0.07 g, n = 11, P < 0.05). Stimulation alone did not affect contractile factor release; however, products released from degranulated PMNs caused significantly greater aortic contraction (0.48 +/- 0.08 g, n = 5) than products from nondegranulated PMNs (0.24 +/- 0.04 g, n = 5, P < 0.05) after a 5-min incubation. The contractile activity of PMN-derived products was virtually abolished by heat (90 degrees C, 10 min) or protease (trypsin; 166 U/ml, 5 h) treatment. These findings suggest a PMN-derived protein vasoconstrictor(s) is spontaneously released at a slow rate in vitro and that degranulation can enhance this rate of release. Because PMN degranulation in vivo is associated with inflammation, these results support suggestions that PMN-derived contractile factors may contribute to the impaired blood flow observed during postischemic reperfusion.

Halothane attenuates nitric oxide relaxation of rat aortas by competition for the nitric oxide receptor site on soluble guanylyl cyclase

Endothelial cells play an important role in the regulation of vascular activity through the release of endothelium derived relaxing factor (EDRF) now believed to be nitric oxide (NO). NO and the NO donor drug nitroglycerin relax vascular smooth muscle by stimulating soluble guanylyl cyclase leading to elevation of intracellular levels of cyclic guanosine 3',5'-monophosphate (cGMP). Halothane has been shown to inhibit the action of NO on blood vessels. This study was designed to further investigate the mechanisms by which halothane attenuates NO-induced vascular relaxations. This was done by examining the effects of halothane on nitroglycerin and NO-induced relaxations in the presence and absence of the inhibitors of soluble guanylyl cyclase, methylene blue and 6-anilino-5,8-quinolinedione (LY 83583). Thoracic aortas from anesthetized male Sprague-Dawley rats were excised and cut into rings and the endothelium was removed. The aortic rings were suspended in organ baths containing Krebs solution and equilibrated at their optimal passive tension. When a stable plateau of contraction was produced by EC60 concentrations of norepinephrine, increasing concentrations of nitroglycerin or NO were added to the baths to relax the rings. This contraction-relaxation procedure was repeated three or four times. In some baths halothane was administered by a calibrated vaporizer 10 min before beginning the second procedure. Either methylene blue or LY 83583 was added to the baths 20 min before the third procedure. The combination of halothane, methylene blue or LY 83583 was added before the fourth procedure. Halothane, methylene blue or LY 83583 significantly inhibited nitroglycerin-induced relaxation individually. Halothane and LY 83583 also significantly inhibited NO-induced relaxations (5 x 10(-9)-3 x 10(-8) M and 5 x 10(-9)-3 x 10(-5) M, respectively) individually. The combination of halothane and methylene blue or halothane and LY 83583 significantly inhibited nitroglycerin-induced relaxation, also, the combination of halothane and LY 83583 significantly inhibited NO-induced relaxations. Halothane, methylene blue and LY 83583 treatment led to rightward shift in the concentration-effect curves. Halothane, in combination with methylene blue or LY 83583, produced inhibition equivalent to the sum of their individual effects. The present study demonstrates that the halothane, methylene blue and LY 83583 attenuate nitroglycerin and NO-induced relaxations of endothelium-denuded rat aortic rings. This suggests that halothane, methylene blue and LY 83583 may act through competitive antagonism at a common site of action on soluble guanylyl cyclase in the EDRF/NO relaxation pathway.

Prevention of ischaemia-induced coronary vascular dysfunction

Myocardial ischaemia and reperfusion cause dysfunction of the coronary vasculature leading to a sustained reduction in coronary blood flow and an impairment of responses to both endothelium-dependent and endothelium-independent vasodilators. In contrast, when previously ischaemic arteries are removed from the myocardium and vascular function is examined in vitro, it is evident that while endothelial function is impaired, smooth muscle reactivity remains intact. Therefore, other changes must be responsible for the general reduction in vasodilator reserve. Examination of the vasculature in the ischaemic myocardium by electron microscopy reveals adhesion of leukocytes and plugging of capillaries. There also is evidence that polymorphonuclear leukocytes (PMNs) release a factor that constricts coronary arterioles, and that release of this factor is increased by atherosclerosis. The identity of this factor remains uncertain, but the calcium antagonist amlodipine prevents the coronary vasoconstriction. Amlodipine is also able to prevent the impaired perfusion and the reduction in vasodilator reserve that occurs after myocardial ischaemia and reperfusion in the dog. In addition, amlodipine prevents the endothelial dysfunction observed in isolated arteries after ischaemia and reperfusion. The interaction between the endothelium and activated PMNs may be a suitable target for pharmacological intervention to improve postischaemic vascular function.

Actions of diaspirin cross-linked hemoglobin on isolated rat and dog vessels

The objectives of these studies were to investigate the responses of isolated blood vessels from rats and dogs to the administration of diaspirin cross-linked hemoglobin (DCLHb) and to determine the mechanisms of these responses. Isolated vascular rings (3 to 5 mm) were suspended at optimal passive tension in Krebs-filled (37 degrees C) tissue baths and bubbled with 95% O2-5% CO2, and isometric tension was recorded. With the vessels under basal conditions increasing concentrations of DCLHb (10(-8)-3 x 10(-6) mol/L) were added. DCLHb addition was repeated during a submaximal contraction with norepinephrine and again during acetylcholine relaxation. The effects of the nitric oxide synthase inhibitor L-nitro arginine (10(-5) mol/L) on the responses to DCLHb were also determined. Dog vessels developed very little tension (1% to 5% of norepinephrine maximum), whereas rat arteries contracted between 9% and 15% when exposed to DCLHb under basal conditions. However, both the dog and rat vessels developed significant tension to DCLHb when they were precontracted (5% to 54%) and also when they were relaxed with acetylcholine (21% to 93%). L-nitro arginine eliminated the contractile responses to DCLHb but did not cause contraction of any of the vessels under basal conditions. We conclude that in this model the mechanism of DCLHb-induced contractions of in vitro dog and rat vessels is dependent on interference with nitric oxide. This is similar to the mechanism of DCLHb action in isolated pig vessels reported previously. Differences in responses of dog, rat, and pig vessels under basal conditions in vitro are the result of active generation of nitric oxide by pig but not by dog or rat vessels.

Novel cypermethrin formulation for the control of sea lice on salmon (Salmo salar)

A novel formulation of cypermethrin was applied as a bath treatment to Atlantic salmon infested with sea lice on a commercial fish farm on the Isle of Skye, Scotland. Twenty 15 m x 15 m cages were treated with cypermethrin at a concentration of 5 micrograms/litre sea water. The numbers of sea lice of all stages were recorded on five fish per cage before the treatment and one, seven and 16 days after treatment. Statistically significant reductions in the numbers of chalimus III and IV pre-adults and adults were recorded over the whole period; the average percentage reductions at one and 16 days after treatment were 59 per cent and 90 per cent (chalimus III and IV), 98 per cent and 95 per cent (pre-adults), and 99 per cent (adults), respectively.

Hemoglobin-induced contraction of pig pulmonary veins

The effects of hemoglobin Ao (HbAo), alpha alpha cross-linked hemoglobin (alpha alphaHb), cyanomet alpha alpha cross-linked hemoglobin (cyanomet alpha alphaHb), and human serum albumin (HSA) were compared under basal conditions and during relaxation with acetylcholine (ACh), sodium nitroprusside (SNP), and papaverine (PAP) in porcine pulmonary veins. Isometric tension changes were recorded in isolated rings (3 to 4 mm) that were suspended in Krebs solution bubbled with 95% O2/5% CO2. Increasing concentrations of HbAo and alpha alphaHb (10(-9) - 3 x 10(-6) mol/L) caused concentration-dependent increases in tension that reached a maximum of 4.20 +/- 0.3 gm and 3.78 +/- 0.6 gm, respectively. Cyanomet alpha alphaHb and HSA (10(-9) - 3 x 10(-6) mol/L) did not cause significant increases in tension. The maximum responses to HbAo and alpha alphaHb were significantly increased during relaxation with ACh and SNP but not with PAP. In contrast, SNP (10(-4) mol/L) and PAP (10(-5) mol/L), but not ACh, reversed contractions induced by HbAo and alpha alphaHb. These studies support the concept that hemoglobin-induced vascular contraction is primarily mediated by inactivation of the vasodilator nitric oxide in vitro. We suggest that this mechanism is common to acellular hemoglobins in which the ligand binding site is unimpaired and in which the heme iron is in the ferrous (+2) state.

Effects of halothane and isoflurane on carbon monoxide-induced relaxations in the rat aorta

BACKGROUND

Halothane and isoflurane previously were reported to attenuate endothelium-derived relaxing factor/nitric oxide-mediated vasodilation and cyclic guanosine monophosphate (cGMP) formation in isolated rat aortic rings. Carbon monoxide has many chemical and physiologic similarities to nitric oxide. This study was designed to investigate the effects of halothane and isoflurane on carbon monoxide-induced relaxations and cGMP formation in the isolated rat aorta.

METHODS

Isometric tension was recorded continuously from endothelium denuded rat aortic rings suspended in Krebs-filled organ baths. Rings precontracted with submaximal concentrations of norepinephrine were exposed to cumulative concentrations of carbon monoxide (26-176 microM). This procedure was repeated three times, with anesthetics delivered 10 min before the second procedure. Carbon monoxide responses of rings contracted with the same concentration of norepinephrine (10(-6) M and 2 x 10(-6) M) used in the anesthetic-exposed preparations also were examined. The concentrations of cGMP were determined in denuded rings using radioimmunoassay. The rings were treated with carbon monoxide (176 microM, 30 s) alone, or carbon monoxide after a 10-min incubation with halothane (0.34 mM or 0.72 mM). To determine whether the sequence of anesthetic delivery influenced results, vascular rings pretreated with halothane were compared with nonpretreated rings.

RESULTS

Carbon monoxide (26-176 microM) caused a dose-dependent reduction of norepinephrine-induced tension, with a maximal relaxation of 1.51 +/- 0.07 g (85 +/- 7% of norepinephrine-induced contraction). Halothane (0.34 mM and 0.72 mM) significantly attenuated the carbon monoxide-induced relaxations, but only the highest concentration of isoflurane (0.53 mM) significantly attenuated the carbon monoxide-induced relaxations. Carbon monoxide (176 microM) significantly increased cGMP content (+88.1 +/- 7.1%) and preincubation of the aortic rings with halothane (0.34 mM and 0.72 mM) inhibited this increase (-70.7 +/- 6.8% and -108.1 +/- 10.6%, respectively). When aortic rings and carbon monoxide were added simultaneously to Krebs solution equilibrated with halothane (0.72 mM), no inhibition of cGMP formation occurred.

CONCLUSION

Carbon monoxide-induced endothelium-independent relaxations of rat aortic rings were decreased by clinically relevant concentrations of halothane and isoflurane. The carbon monoxide-induced elevations of cGMP were attenuated by halothane only when the anesthetic was incubated with aortic rings before carbon monoxide treatment. The possible clinical significance of the actions of the anesthetics on this endogenous vasodilator is yet to be determined.

Cholesterol feeding enhances vasoconstrictor effects of products from rabbit polymorphonuclear leukocytes

We have studied the vasoactive properties of products released from rabbit polymorphonuclear leukocytes (PMNs) before and after short-term (4 and 8 wk) dietary supplementation with 1% cholesterol. Plasma cholesterol levels were similar after 4 and 8 wk of cholesterol diet, whereas gross atherosclerotic lesions were present at 4 wk but significantly more extensive after 8 wk. PMN products from all rabbits caused endothelium-dependent contraction of isolated, control (nonatherosclerotic) rabbit aorta submaximally contracted with phenylephrine. However, both 4 and 8 wk of cholesterol feeding resulted in equivalent contractions by PMN products, which were significantly greater than contractions by control PMNs. Endothelium-dependent contraction (by PMN products) and relaxation (by acetylcholine) were attenuated by 8 wk of cholesterol feeding. PMN products attenuated acetylcholine-induced relaxation of aorta from cholesterol-fed rabbits and of control aorta treated with phenoxybenzamine to reduce muscarinic receptor reserve. We conclude that elevation of plasma cholesterol results in increased release of a PMN product(s) that causes endothelium-dependent constriction.

Effects of halogenated and non-halogenated anesthetics on diaspirin cross-linked hemoglobin induced contractions of porcine pulmonary veins

Diaspirin crosslinked hemoglobin (DCLHb) is a resuscitative fluid presently undergoing clinical trials. Administration of DCLHb is associated with an elevation of mean arterial pressure in vivo and contraction of isolated blood vessels in vitro. The mechanisms for the vascular actions are unknown but may be due to inhibition of nitric oxide (NO). Halothane has been reported to inhibit NO induced relaxation. We examined the effect of anesthetics on DCLHb induced contraction of blood vessels. Porcine pulmonary veins were excised, cut into rings and placed in organ chambers filled with 25 ml Krebs-Ringer solution (37 degrees C). Following equilibration at their optimal length the rings were exposed to increasing concentrations of serotonin(10(-8)M-10(-5)M). Endothelial activity was confirmed by relaxation greater than 80% with ACh (10(-6)M). DCLHb (1.5 x 10(-8)M to 6 x 10(-7)M) contracted porcine pulmonary veins (1.04 +/- 0.17g to 3.45 +/- 0.22g), and halothane (0.5% and 1%) significantly inhibited these DCLHb induced contractions in a dose-related manner (-41.6 +/- 8.1% and -73.3 +/- 8.2%, respectively). At equi-molar concentrations, isoflurane had no inhibitory activity. The relative effect of these volatile anesthetics is consistent with their inhibitory actions on other heme containing proteins. Propofol (10(-5)M) only has inhibitory effects on lower concentrations of DCLHb. Fentanyl did not have inhibitory effects. These results suggest that halogenated anesthetics may interact with the heme iron of DCLHb and inhibit its binding with NO.

Comparative effects of exogenous nitrovasodilators on cGMP levels in different canine blood vessels

Nitrovasodilators, by releasing nitric oxide (NO) in vascular smooth muscle, activate soluble guanylate cyclase (sGC) in vascular smooth muscle. However, there is little information on their relative effectiveness, concentration ranges, or on the incubation times required to produce maximum sGC stimulation. To determine the optimal concentrations and incubation times we measured 3', 5'-cyclic guanosine monophosphate (cGMP) levels in response to different concentrations of NO, S-nitroso-L-cysteine (SNC), and S-nitroso-N-acetylpenicillamine (SNAP), in canine aorta, femoral, and carotid arteries incubated in Krebs. Production of cGMP following incubation of endothelium denuded tissues with NO, SNC, and SNAP peaked close to 20 +/- 5, 90 +/- 20, and 120 +/- 60 seconds respectively. Results indicate that cGMP levels vary with concentration of nitrovasodilators and time of incubation. SNAP was the least effective in increasing cGMP levels among the three nitrovasodilators used. In different vascular beds, the production of cGMP in the presence of nitrovasodilators may depend on variations in the levels of guanylate triphosphate (GTP) and/or sGC.

Vascular effects of halothane and isoflurane: cGMP dependent and independent actions

This study investigated the effects of halothane and isoflurane on cGMP-dependent and independent regulation of vascular contraction of the isolated rat aorta and on NO-stimulated soluble guanylate cyclase (sGC) isolated from the perfused rat liver. For the studies of the aorta, isometric tension of isolated rings, with and without, endothelium was recorded and cGMP content measured. ACh was used to initiate endothelial-dependent relaxation of norepinephrine (NE)-contracted rings while NO was used to directly stimulate isolated aortic ring sGC which catalyzes the isolated aortic ring formation of cGMP. Both halothane and isoflurane interfered with ACh and NO relaxations and with NO-stimulated increases in cGMP. Halothane was more potent, having significant attenuating effects at 0.34 mM (1 MAC) and 0.72 mM (2 MAC) while isoflurane had effects only at 0.53 mM (2 MAC). For the isolated sGC studies, a soluble liver fraction was prepared from perfused rat livers. In the absence of NO stimulation, neither halothane nor isoflurane modified the activity of the sGC. However, during NO-stimulation halothane produced significant, concentration-dependent, inhibition of sGC activity over a wide range of NO concentrations. Isoflurane also inhibited sGC activity, but to a lesser extent than halothane. The mechanism whereby the anesthetics could interfere with sGC from liver and blood vessels is unknown. It could result from anesthetic interaction at hydrophobic sites that may exist in GC. However, the results of both the aorta and liver sGC enzyme studies support the suggestion that these anesthetics can compete with NO for its binding site on the ferrous heme of sGC, with chemical structural differences accounting for the potency variations. Both anesthetics also had cGMP independent effects, causing concentration dependent relaxations of NE-contracted vessels without endothelium. Isoflurane was about 5 times more effective at 1 MAC than halothane. Therefore, the net effects of these anesthetics involve the sum of two opposite effects on tension of vessels with intact endothelium: 1) interference with NO-stimulated cGMP relaxation and 2) direct stimulation of relaxation (not dependent on changes in cGMP).

Vasoconstrictor responses to polymorphonuclear leucocytes from atherosclerotic rabbits

1. The vascular contractile effects of polymorphonuclear leucocytes (PMN) isolated from control rabbits and from rabbits made atherosclerotic by 1% cholesterol feeding for 8 weeks were examined. 2. Rings of control rabbit thoracic aorta with or without endothelium were mounted at 2 g tension in 10 mL organ baths and were submaximally contracted by phenylephrine (0.1 mumol/L). After 30 min incubation at 37 degrees C, the supernatant of PMN (5 x 10(7)/mL, in Tyrode solution containing 0.25% bovine serum albumin) was obtained by centrifugation for addition to the vascular preparation. 3. Control PMN supernatant (443 microL) caused contraction (0.58 +/- 0.15 g, n = 11) of phenylephrine-contracted aortic rings, which was prevented by removal of the endothelium (0.11 +/- 0.07 g, n = 5, P < 0.05). However, the control PMN supernatant had no contractile effect on aortic rings at resting tension (0.00 +/- 0.00 g, n = 8). 4. By comparison, atherosclerotic PMN supernatant (443 microL) caused a significantly greater contraction of the aortic rings (1.41 +/- 0.13 g, n = 9, P < 0.05 vs control PMN supernatant) that was only partly inhibited by removal of the endothelium (0.45 +/- 0.20 g, n = 9, P < 0.05). Moreover, PMN supernatants from four of seven atherosclerotic rabbits contracted aortic rings at resting tension (3.5 +/- 1.4 g, n = 7). 5. These results suggest that the release of a stable vasoconstrictor substance(s) by PMN is enhanced under conditions of atherosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of halothane on EDRF/cGMP-mediated vascular smooth muscle relaxations

BACKGROUND

Halothane has been reported to inhibit endothelium-dependent relaxation in a variety of vessels. These studies were done to determine whether this inhibition is caused by interference with synthesis, release, or action of endothelium-derived relaxing factor (EDRF) on cyclic guanosine monophosphate (cGMP) levels within the vascular smooth muscle.

METHODS

Rat aortic rings were suspended in aerated Krebs solution (37 degrees C) and were contracted to a stable plateau with EC60-70 norepinephrine (NE). Relaxations caused by acetylcholine (ACh; 1 x 10(-8)-1 x 10(-6) M), nitric oxide (NO; 5 x 10(-9)-1 x 10(-6) M), or nitroglycerin (NG; 2 x 10(-9)-3 x 10(-7) M) in rings contracted with NE were compared in the presence and absence of halothane. Tissue cGMP contents were measured using a radioimmunoassay method.

RESULTS

In the presence of halothane (0.5, 1.0, and 2.0 MAC), the ACh-induced relaxations were significantly attenuated in a concentration-dependent manner, an effect that was reversible. Halothane (2 MAC) significantly attenuated NO-induced relaxations at all concentrations and NG-induced relaxations at low concentrations (5 x 10(-9)-3 x 10(-8) M) but not at higher concentrations (1 x 10(-9)-3 x 10(-7) M) in denuded vessels. Nitric oxide-stimulated (5 x 10(-8)-5 x 10(-6) M) cGMP content was significantly attenuated by halothane (2 MAC) at NO concentrations between 1 x 10(-7) and 5 x 10(-6) M.

CONCLUSIONS

Nitric oxide, either endogenous or exogenous, interacts with the enzyme guanylate cyclase to stimulate the production of cGMP. Halothane interfered with the relaxations caused by NO (in rings without endothelium) and decreased the NO-stimulated cGMP content. These results suggest that the site of action of halothane in attenuating endothelium-dependent relaxation in the rat aorta is within the vascular smooth muscle, rather than on the synthesis, release, or transit of the EDRF from the endothelium and that its action may involve an interference with guanylate cyclase activation.

Neurovascular effects of reactive oxygen intermediates produced by photoradiation

These experiments examined the effect of reactive oxygen intermediates, produced by laser illumination of the photosensitizer hematoporphyrin derivative, on the accumulation and release of norepinephrine from sympathetic nerve terminals. Using an isolated, spirally cut, superfused caudal artery of the rat, basal overflow of norepinephrine (NE) was significantly increased both during and after generation of reactive oxygen intermediates. Generation of reactive oxygen intermediates increased overflow of NE in vascular preparations in which release of NE had previously been elevated by the continuous superfusion of Krebs' solution, containing high concentrations of potassium (40 mM). Calcium free solutions did not block the overflow of norepinephrine augmented by reactive oxygen intermediates. This increase in overflow was due both to an increase in release of NE and an inhibition of accumulation of NE.

Vascular interactions of calcium and reactive oxygen intermediates produced following photoradiation

This study was designed to examine vascular smooth muscle contractile properties following enhanced production of reactive oxygen intermediates (ROIs), which were produced by pretreating rat caudal arteries and aortas with a photosensitizer, hematoporphyrin derivative, and then illuminating them with red laser light. This treatment produced a long-lasting contraction that was dependent on the presence of extracellular calcium. Reduction in extracellular calcium relaxed the smooth muscle and replacement of calcium 30 min later increased the tension. Oxygen radical scavengers did not block the contractile effect postillumination when calcium was returned to the bathing solution; however, verapamil (5.5 microM) and nifedipine (10 microM) attenuated this contraction. The contractions were dependent on oxygen in the aerating gas mixture. Production of ROIs by isolated blood vessels was supported biochemically by a significant increase in both bath and tissue levels of oxidation products, reactive with thiobarbituric acid, and by a reduction in the tissue stain, nitroblue tetrazolium. These ROI-induced contractions were observed in vitro on large conduit arteries and also in vivo on small ear arteries. The vascular response following this acute production of ROIs may be similar to vascular abnormalities in certain pathological conditions where ROI production is reported to be elevated. Therefore, these results could contribute to a further understanding of mechanisms involved in these ROI-dependent vascular changes.

Contractile properties of isolated vascular smooth muscle after photoradiation

The purpose of this study was to characterize the responses of various types of vascular smooth muscle to conditions that would be encountered during photodynamic therapy, namely laser illumination of photosensitizer-pretreated tissue. Vascular smooth muscle obtained from representative canine, rodent, and rabbit vascular beds was cut into rings and placed in organ baths (37 degrees C, aerated with 95% O2-5% CO2). These vessels were pretreated for 30 min with the photosensitizer hematoporphyrin derivative (HpD, 3-30 micrograms/ml) washed, and then exposed to red laser light (633 nm, 1-3.5 mW) for up to 20 min. Under basal tension conditions laser illumination of HpD-pretreated vessels resulted in an increase in tension, whereas laser illumination of vessels not exposed to HpD did not contract. This sustained contraction was not reversed by washing the tissue with fresh Krebs-Ringer solution. Responses to norepinephrine, transmural electrical stimulation, and elevated concentrations of KCl were reduced in blood vessels tested after HpD laser illumination. Laser-induced contractions of canine carotid arteries did not require the presence of an intact vascular endothelium. Vascular effect of these photosensitizers appears to involve the formation of oxygen-derived radicals. This preparation could provide a good model for examining the effects of free radicals on vascular physiology.

Adrenergic nerve function and contractile activity of the caudal artery of the streptozotocin diabetic rat

The adrenergic nerve function and contractile responses of the densely innervated caudal artery of the 8-week streptozotocin (SZ) (65 mg/kg i.p.) diabetic rat were investigated. Segments of this artery were removed from diabetic and control rats, placed in Krebs-filled tissue baths (37 degrees C) and isometric tension recorded. Contractile responses to sympathetic nerve activation by electrical stimulation and to cumulative concentrations of norepinephrine (NE) and tyramine were recorded. In order to determine NE content, the NE was extracted from the caudal artery, isolated by adsorption chromatography, and quantified by HPLC with electrochemical detection. NE accumulation and release were also studied by quantifying the amount of tritiated NE [( 3H]NE) and its metabolites in extracts of the tissue or incubation medium. The responses of the caudal artery of SZ diabetic rats to electrical stimulation (4-16 Hz) and to tyramine (1 X 10(-5)-1 X 10(-4) M) were significantly less than those of arteries from control rats and the NE content reduced by 41%, while sensitivity to NE was unchanged. Diabetic arteries also accumulated and released more [3H]NE than did arteries from control rats. These results establish that neurovascular function of the isolated caudal artery of the 8-week SZ diabetic rat is abnormal and suggest that problems in the ability of adrenergic nerves to store and release NE may contribute to this dysfunction. Such changes may play a role in the cardiovascular disturbances associated with diabetic autonomic neuropathy.

Attenuation of endothelium-mediated vasodilation by halothane

To determine whether halothane alters endothelium-mediated vasodilation of vascular smooth muscle, isolated ring preparations of rabbit aorta and canine femoral and carotid arteries were suspended for isometric tension recordings in Krebs-Ringer bicarbonate solution at 37 degrees C. Acetylcholine and bradykinin have been shown to relax these norepinephrine contracted arteries via an endothelium-dependent process. In this study, these relaxations were reversibly and significantly attenuated by 2% halothane. However, halothane did not affect relaxations caused by nitroglycerin, which, in these vessels, acts by an endothelium independent mechanism. These results suggest that halothane is not interfering with cyclic guanylate-monophosphate mediated relaxation of vascular smooth muscle, but may interfere with the synthesis, release, or transport of the endothelium-derived relaxing factor. In addition, during contractions evoked by norepinephrine, halothane caused significant decreases in tension in both the canine carotid and rabbit aortic preparations, but increased tension in the femoral artery rings. These effects were not altered by mechanical removal of the endothelium. These results suggest a direct action of halothane on the vascular smooth muscle, which can result in either an increase or decrease in tension, depending on the specific vessel. In addition to its direct vascular effect, this study suggests a new action of halothane; it interferes with endothelium-derived relaxing factor-mediated relaxation of vascular smooth muscle. This action may contribute in part to the vascular alterations seen clinically during administration of halothane.