Career flexibility for PAs: What makes switching specialties successful?

ABSTRACT

Switching specialties is common among physician associates/assistants (PAs) and important in combating burnout. Despite this, little is known about the PA experience with switching specialties. This study sought to identify factors associated with successfully switching specialties using semistructured interviews with PAs and hiring managers. Participants reported that switching specialties was initially challenging for managers and PAs because of insufficient onboarding and unrealistic expectations, but they also reported that they were generally satisfied with long-term outcomes. Our findings suggest that PAs hoping to switch specialties may want to focus on building a professional network, identifying areas where they can highlight relevant experience, and demonstrating their intent to remain in that role. Hiring managers could benefit from considering their hiring practices and tailoring onboarding expectations for new hires.

Moral Engagement and Disengagement in Health Care AI Development

BACKGROUND

Machine learning (ML) is utilized increasingly in health care, and can pose harms to patients, clinicians, health systems, and the public. In response, regulators have proposed an approach that would shift more responsibility to ML developers for mitigating potential harms. To be effective, this approach requires ML developers to recognize, accept, and act on responsibility for mitigating harms. However, little is known regarding the perspectives of developers themselves regarding their obligations to mitigate harms.

METHODS

We conducted 40 semi-structured interviews with developers of ML predictive analytics applications for health care in the United States.

RESULTS

Participants varied widely in their perspectives on personal responsibility and included examples of both moral engagement and disengagement, albeit in a variety of forms. While most (70%) of participants made a statement indicative of moral engagement, most of these statements reflected an awareness of moral issues, while only a subset of these included additional elements of engagement such as recognizing responsibility, alignment with personal values, addressing conflicts of interests, and opportunities for action. Further, we identified eight distinct categories of moral disengagement reflecting efforts to minimize potential harms or deflect personal responsibility for preventing or mitigating harms.

CONCLUSIONS

These findings suggest possible facilitators and barriers to the development of ethical ML that could act by encouraging moral engagement or discouraging moral disengagement. Regulatory approaches that depend on the ability of ML developers to recognize, accept, and act on responsibility for mitigating harms might have limited success without education and guidance for ML developers about the extent of their responsibilities and how to implement them.

Practical Approaches to Enhancing Fairness, Social Responsibility and the Inclusion of Diverse Viewpoints in Biomedicine

The following sections are included:Workshop DescriptionLearning ObjectivesPresenter InformationAbout the Workshop OrganizersPresentationsSpeaker Presentations.

Impact of Sexual Harassment and Social Support on Burnout in Physician Mothers

Background: Burnout affects >50% of physicians, especially women. This study aimed to examine how negative workplace interactions can predict burnout, and whether positive social interactions can mitigate risk. Materials and Methods: In a study of 1627 physician mothers who responded to a survey by the Physician Moms Group, an online Facebook group, we first examined the association between workplace sexual harassment and burnout. In an embedded experiment, we then measured the causal impact of priming perceived social support and connectedness on the three dimensions of employee burnout. Results: Two-thirds of respondents reported having experienced sexual harassment in the past year. Sexual harassment by patients was associated with 0.27 points higher emotional exhaustion, one dimension of burnout (95% confidence interval [CI] 0.12-0.41), equivalent to the predicted impact of an additional 22 weekly work hours on emotional exhaustion. Sexual harassment by patients was also associated with 0.40 points higher patient depersonalization, another dimension of burnout (95% CI 0.27-0.53). Sexual harassment by colleagues was associated with 0.16 points higher emotional exhaustion (95% CI 0.02-0.30), but not other dimensions of burnout. We found no significant relationship between experiences of sexual harassment and levels of personal accomplishment (the third dimension of burnout) among this sample. Priming physician mothers to reflect on their connectedness with other physician mothers significantly increased their sense of personal accomplishment. The priming intervention did not yield a significant effect on emotional exhaustion or depersonalization. Conclusions: Negative and positive social interactions each affect different dimensions of burnout. Sexual harassment-a pervasive type of negative social interaction-strongly predicts emotional exhaustion and depersonalization. Reflecting on social connectedness-a type of positive social interaction-can improve one's sense of personal accomplishment with an effect similar in magnitude to more intensive in-person interventions, suggesting that social connectedness through online groups merits further consideration as a tool to mitigate burnout.

Barriers and facilitators to mobile health and active surveillance use among older adults with skin disease

Background

The COVID‐19 pandemic has accelerated the adoption of telemedicine, including teledermatology. Monitoring skin lesions using teledermatology may become increasingly important for several skin diseases, including low‐risk skin cancers. The purpose of this study was to describe the key factors that could serve as barriers or facilitators to skin disease monitoring using mobile health technology (mHealth) in older adults.

Methods

Older adult dermatology patients 65 years or older and their caregivers who have seen a dermatologist in the last 18 months were interviewed and surveyed between December 2019 and July 2020. The purpose of these interviews was to better understand attitudes, beliefs and behaviours that could serve as barriers and facilitators to the use of mHealth and active surveillance to monitor low‐risk skin cancers.

Results

A total of 33 interviews leading to 6022 unique excerpts yielded 8 factors, or themes, that could serve as barriers, facilitators or both to mHealth and active surveillance. We propose an integrated conceptual framework that highlights the interaction of these themes at both the patient and provider level, including care environment, support systems and personal values.

Discussion and conclusions

These preliminary findings reveal factors influencing patient acceptance of active surveillance in dermatology, such as changes to the patient‐provider interaction and alignment with personal values. These factors were also found to influence adoption of mHealth interventions. Given such overlap, it is essential to address barriers and facilitators from both domains when designing a new dermatology active surveillance approach with novel mHealth technology.

Patient or public contribution

The patients included in this study were participants during the data collection process. Members of the Stanford Healthcare and Denver Tech Dermatology health‐care teams aided in the recruitment phase of the data collection process.

Development of a patient decision aid for the management of superficial basal cell carcinoma (BCC) in adults with a limited life expectancy

BACKGROUND

Basal cell carcinoma (BCC) is a slow-growing, rarely lethal skin cancer that affects people 65 years or older. A range of treatment options exist for BCC, but there is little evidence available to guide patients and providers in selecting the best treatment options.

OBJECTIVES

This study outlines the development of a patient decision aid (PDA) for low-risk BCC that can be used by patients and providers to assist in shared decision-making.

METHODS

In accordance with the International Patient Decision Aids Standards (IPDAS) Collaboration framework, feedback from focus groups and semi-structured interviews with patients and providers, an initial prototype of the PDA was developed. This was tested using cognitive interviews and iteratively updated.

RESULTS

We created eighteen different iterations using feedback from 24 patients and 34 providers. The key issues identified included: 1) Addressing fear of cancer; 2) Communicating risk and uncertainty; 3) Values clarification; and 4) Time lag to benefit.

LIMITATIONS

The PDA does not include all possible treatment options and is currently paper based.

CONCLUSIONS

Our PDA has been specifically adapted and designed to support patients with a limited life expectancy in making decisions about their low risk BCC together with their doctors.

Experience with Social Distancing Early in the COVID-19 Pandemic in the United States: Implications for Public Health Messaging

Our goal is to inform ongoing public health policy on the design and communication of COVID-19 social distancing measures to maximize compliance. We assessed the US publics early experience with the COVID-19 crisis during the period when shelter-in-place orders were widely implemented to understand non-compliance with those orders, sentiment about the crisis, and to compare across age categories associated with different levels of risk. We posted our survey on Twitter, Facebook, and NextDoor on March 14th to March 23rd that included 21 questions including demographics, impact on daily life, actions taken, and difficulties faced. We analyzed the free-text responses to the impact question using LIWC, a computational natural language processing tool, and performed a thematic content analysis of the reasons people gave for non-compliance with social distancing orders. Stanford Universitys IRB approved the study. In 9 days, we collected a total of 20,734 responses. 6,573 individuals provided a response (≥30 words) to the question, Tell us how the coronavirus crisis is impacting your life. Our data (Figure 1) show that younger people (18-31) are more emotionally negative, self-centered, and less concerned with family, while middle-aged people are group-oriented (32-44) and focused on family (32-64) (all p values < .05 corrected for multiple comparisons). Unsurprisingly, the oldest and most at-risk group (65+) are more focused on biological terms (e.g., health-related topics), but were surprisingly low in anxiety and high in emotionally positive terms relative to those at lower risk. We also content-analyzed 7,355 responses (kappas > .75) to the question, What are the reasons you are not self-isolating more? Of these participants, 39.8% reported not being compliant, with the youngest group (18-31) having the lowest compliance rate (52.4%) compared to the other age groups (all > 60%; all p values < .01). Table 1 describes the seven primary themes for non-compliance. Non-essential work requirements, concerns about mental and physical health, and the belief that other precautions were sufficient were the most common reasons, although other rationales included wanting to continue everyday activities and beliefs that society is over-reacting. Childcare was an important concern for a subset of respondents. Overall, our findings suggest that public health messages should focus on young people and 1) address their negative affect, 2) refocus their self-orientation by emphasizing the importance of individual behavior to group-level health outcomes, and 3) target the specific rationales that different people have regarding the pandemic to maximize compliance with social distancing.

Differing views regarding diet and physical activity: adolescents versus parents' perspectives

Background

Today, approximately one in five United States adolescents age 12 to 19 years is obese and just over a third are either overweight or obese. This study examines how parents and peers influence diet and physical activity behaviors of older adolescents (14–18 years) with overweight or obesity to inform weight management interventions.

Methods

Adolescent participants included 14 to 18-year-olds with a Body Mass Index (BMI) greater than the 85th percentile for their age and sex who were receiving care in a large healthcare system in Northern California. Adolescents and their parents participated in separate focus groups and interviews (if not able to attend focus groups) that were held at the same time in the same location. We used qualitative thematic analysis to identify common themes discussed in the adolescent and parent focus groups as well as paired analysis of adolescent-parent dyads.

Results

Participants included 26 adolescents and 27 parents. Adolescent participants were 14 to 18 years old. Half were female and the participants were almost evenly distributed across year in school. The majority self-identified as White (56%) and Asian (36%).Three themes were identified which included 1) parents overestimated how supportive they were compared to adolescents’ perception 2) parents and adolescents had different views regarding parental influence on adolescent diet and physical activity behaviors 3) parents and adolescents held similar views on peers’ influential role on lifestyle behaviors.

Conclusion

Parents’ and adolescents’ differing views suggest that alignment of parent and adolescent expectations and behaviors for supporting effective weight management could be incorporated into interventions.

Association between financial links to indoor tanning industry and conclusions of published studies on indoor tanning: systematic review

OBJECTIVE

To assess whether an association exists between financial links to the indoor tanning industry and conclusions of indoor tanning literature.

DESIGN

Systematic review.

DATA SOURCES

PubMed, Embase, and Web of Science, up to 15 February 2019.

STUDY SELECTION CRITERIA

Articles discussing indoor tanning and health were eligible for inclusion, with no article type restrictions (original research, systematic reviews, review articles, case reports, editorials, commentaries, and letters were all eligible). Basic science studies, articles describing only indoor tanning prevalence, non-English articles, and articles without full text available were excluded.

RESULTS

691 articles were included in analysis, including empiric articles (eg, original articles or systematic reviews) (357/691; 51.7%) and non-empiric articles letters (eg, commentaries, letters, or editorials) (334/691; 48.3%). Overall, 7.2% (50/691) of articles had financial links to the indoor tanning industry; 10.7% (74/691) articles favored indoor tanning, 3.9% (27/691) were neutral, and 85.4% (590/691) were critical of indoor tanning. Among the articles without industry funding, 4.4% (27/620) favored indoor tanning, 3.5% (22/620) were neutral, and 92.1% (571/620) were critical of indoor tanning. Among the articles with financial links to the indoor tanning industry, 78% (39/50) favored indoor tanning, 10% (5/50) were neutral, and 12% (6/50) were critical of indoor tanning. Support from the indoor tanning industry was significantly associated with favoring indoor tanning (risk ratio 14.3, 95% confidence interval 10.0 to 20.4).

CONCLUSIONS

Although most articles in the indoor tanning literature are independent of industry funding, articles with financial links to the indoor tanning industry are more likely to favor indoor tanning. Public health practitioners and researchers need to be aware of and account for industry funding when interpreting the evidence related to indoor tanning.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019123617.

Quantitation of Tebuconazole in Liquid and Solid Formulations by Capillary GC: Collaborative Study

A capillary gas chromatographic method has been developed for quantitation of tebuconazole (Folicur, Elite, Raxil, Lynx) in liquid and solid formulations. Tebuconazole is a broad-spectrum, systemic foliar fungicide used to control diseases of wheat, barley, peanut, and grasses grown for seed. Samples are dissolved in acetone and analyzed by capillary gas chromatography (GC) with dicyclohexyl phthalate as internal standard. Twenty-two laboratories from 11 countries participated in a collaborative study of the method. Each collaborator was provided reference standard, internal standard, and blind duplicate samples from 6 formulations: aqueous flowable (F), aqueous emulsifiable concentrate (EW), emulsifiable concentrate for seed treatment (ES), flowable for seed treatment (FS), wettable powder (WP), and dry flowable (DF). Collaborators were instructed to use peak area measurements for quantitation. The seed treatment flowable formulation required confirmation of accurate integration values by the collaborator. Relative standard deviation values for reproducibility (RSDR) for analysis of the formulations were as follows: 3.6 lb/gal F, 1.22; 250 g/L EW, 1.13; 15 g/L ES, 2.40; 25 g/L FS, 2.65; 25% WP, 0.96; 25% DF, 0.72; 45% DF, 0.72. The capillary GC method for quantitation of tebuconazole in fungicide formulations has been adopted first action by AOAC INTERNATIONAL.

Beyond Consent: Building Trusting Relationships With Diverse Populations in Precision Medicine Research

With the growth of precision medicine research on health data and biospecimens, research institutions will need to build and maintain long-term, trusting relationships with patient-participants. While trust is important for all research relationships, the longitudinal nature of precision medicine research raises particular challenges for facilitating trust when the specifics of future studies are unknown. Based on focus groups with racially and ethnically diverse patients, we describe several factors that influence patient trust and potential institutional approaches to building trustworthiness. Drawing on these findings, we suggest several considerations for research institutions seeking to cultivate long-term, trusting relationships with patients: (1) Address the role of history and experience on trust, (2) engage concerns about potential group harm, (3) address cultural values and communication barriers, and (4) integrate patient values and expectations into oversight and governance structures.

The Importance Of Integrating Narrative Into Health Care Decision Making

When making health care decisions, patients and consumers use data but also gather stories from family and friends. When advising patients, clinicians consult the medical evidence but also use professional judgment. These stories and judgments, as well as other forms of narrative, shape decision making but remain poorly understood. Furthermore, qualitative research methods to examine narrative are rarely included in health science research. We illustrate how narratives shape decision making and explain why it is difficult but necessary to integrate qualitative research on narrative into the health sciences. We draw on social-scientific insights on rigorous qualitative research and our ongoing studies of decision making by patients with cancer, and we describe new tools and approaches that link qualitative research findings with the predominantly quantitative health science scholarship. Finally, we highlight the benefits of more fully integrating qualitative research and narrative analysis into the medical evidence base and into evidence-based medical practice.

"Hot Girls Pearls" and other coping strategies for women experiencing adverse effects from endocrine therapy in the treatment of breast cancer

197

Background: While endocrine therapy can significantly improve outcomes for women with hormone receptor-positive breast cancer, as few as 50% of patients take the medication as prescribed. Studies have shown that physical side effects contribute to non-adherence with hormone therapy. This study draws on prospective, qualitative interviews with patients to identify coping strategies patients employ to manage concerns over current and anticipated side effects, and suggests methods for encouraging adherence. Methods: Interviews were conducted with breast cancer patients (n = 41) at four time points throughout their treatment, resulting in over 150 patient narratives. Using a grounded theory approach, data were coded and analyzed to identify influential factors in decision-making. Here we present data from a subset of our participants (n = 18) focused on the role of side effects in patients' endocrine therapy decision-making. Results: Patients expressed a variety of concerns about current and anticipated side effects associated with endocrine therapy. Our data suggest five categories of coping strategies participants employed to manage these concerns: 1) emphasizing control over their choice to remain adherent; 2) focusing on a future free from side effects and cancer instead of current concerns or discomfort; 3) "familiarizing" side effects to make current and potential treatment risks feel less strange and/or intimidating; 4) making lifestyle changes to mitigate physical discomfort; and 5) seeking help from both medical and social sources. Patients often described using these multiple strategies to help navigate the functional, social and physical responses to side effects, and remain adherent to their treatment regimen. Conclusions: Our data describe the diverse coping strategies employed by women to manage current or anticipated side effects, and maintain adherence to prescribed endocrine therapy. Discussion of these different coping strategies by clinicians with patients may help to improve adherence rates by personalizing approaches to managing side effects.

An effort to spread decision aids in five California primary care practices yielded low distribution, highlighting hurdles

Despite the proven efficacy of decision aids as interventions for increasing patient engagement and facilitating shared decision making, they are not used routinely in clinical care. Findings from a project designed to achieve such integration, conducted at five primary care practices in 2010-12, document low rates of distribution of decision aids to eligible patients due for colorectal cancer screening (9.3 percent) and experiencing back pain (10.7 percent). There were also no lasting increases in distribution rates in response to training sessions and other promotional activities for physicians and clinic staff. The results of focus groups, ethnographic field notes, and surveys suggest that major structural and cultural changes in health care practice and policy are necessary to achieve the levels of use of decision aids and shared decision making in routine practice envisioned in current policy. Among these changes are ongoing incentives for use, physician training, and a team-based practice model in which all care team members bear formal responsibility for the use of decision aids in routine primary care.

The impact of “significant others” on breast cancer patients’ treatment decision making

20

Background: Shared medical decision making (SDM) has been lauded by advocates for its potential to democratize the patient-physician relationship. However, the practice of SDM is still conceived of as largely a dyadic moment that exists between the patient and the physician. Few studies have looked at the role of significant others (spouses, partners, family members and friends) in decision making or considered how discussions and actions outside the consultation room affect a patient’s medical decisions. This prospective study investigated the impact of significant others on the decision making deliberations of newly diagnosed breast cancer patients. Methods: Forty-one newly diagnosed breast cancer patients were interviewed at four critical time points throughout treatment to explore how they deliberated decisions with both care providers and significant others. Surveys assessing HRQOL, role preferences and treatment satisfaction along with EHR abstraction augmented interview data. Grounded theory analysis was used to identify recurrent themes in the qualitative data, and survey data were analyzed using IBM SPSS Statistics 20. Results: Emergent themes from our analysis identified several factors that patients consider when faced with cancer treatment decisions, including 1) presentation of treatment options 2) patient or significant other conflict/concordance with care team recommendations 3) perceived risk of recurrence and 4) short and long term impact of treatment on daily life. Participants stressed the need for clinicians to view patients beyond diagnosis and recognize their larger care network as influential factors in their decision making. Conclusions: Our interviews highlight how the current healthcare delivery structure rarely acknowledges the circles of care that can exert influence on decision making. Lack of attention to non-clinical others can lead to sub-optimal medical decision making because these influences are not adequately understood by clinicians. Findings from this study suggest the need to enhance clinicians’ and researchers’ understanding of the influence of others in patients’ treatment decision making, enabling them to intervene in these practices.

Aeromonas abscess in an immunocompromised child

An 11-year-old immunocompromised child developed cellulitis and abscess due to Aeromonas hydrophila at the site of bone marrow aspiration after swimming in a freshwater lake. The patient required treatment with intravenous antibiotics and surgical debridement to eradicate the infection. Both common and unusual organisms may complicate infections at the sites of percutaneous procedures.

Delayed posttraumatic brain hyperthermia worsens outcome after fluid percussion brain injury: a light and electron microscopic study in rats

The morphological consequences of delayed posttraumatic brain hyperthermia (39 degrees C) after fluid percussion brain injury were assessed in rats. Sprague-Dawley rats anesthetized with 4% halothane and maintained on a 70:30 mixture of nitrous oxide:oxygen and 0.5% halothane underwent moderate (1.5-2.0 atm) traumatic brain injury with the injury screw positioned parasagittally over the right parieto-occipital cortex. At 24 hours after traumatic brain injury, the rats were reanesthetized and randomized into two groups in which either a 3-hour period of brain normothermia (36.5 degrees C, n = 18) or hyperthermia (39 degrees C, n = 18) was maintained. Sham-operated controls (n = 10) underwent all surgical and temperature-monitoring procedures. After the 3-hour monitoring period, the rats were allowed to survive for 3 days for light microscopic analysis or were injected with the protein tracer horseradish peroxidase and were perfusion-fixed 15 minutes later for light and electron microscopic analysis. At 4 days after traumatic brain injury, delayed posttraumatic hyperthermia (n = 12) significantly increased mortality (47%) and contusion volume (1.7 +/- 0.69 mm3, mean +/- standard error of the mean), compared to normothermia (n = 12) (18% mortality and 0.13 +/- 0.21 mm3 contusion volume) (P < 0.01, analysis of variance). At 15 minutes after the 3-hour hyperthermic period, the area of hemorrhage and horseradish peroxidase extravasation overlying the lateral external capsule was significantly increased (2.52 +/- 0.71 mm2, mean +/- standard error of the mean, versus 0.43 +/- 0.16 mm2) (P < 0.01), compared to normothermic rats. Examination of toluidine blue-stained plastic sections demonstrated a higher frequency of abnormally swollen myelinated axons per high microscopic field with hyperthermia. For example, numbers of swollen axons within the sixth layer of the right somatosensory cortex, corpus callosum, and internal capsule were 7.3 +/- 1.3, 4.2 +/- 1.4, and 3.0 +/- 1.2 axons (mean +/- standard error of the mean) with normothermia, respectively, compared with 24.7 +/- 12.1, 33.1 +/- 4.2, and 27.3 +/- 3.1 axons with hyperthermia, respectively (P < 0.01). An ultrastructural examination of the swollen axons demonstrated a severely thinned myelin sheath containing axoplasm devoid of cytoskeletal components. These experimental results indicate that posttraumatic brain hyperthermia might increase morbidity and mortality in patients with head injury by aggravating axonal and microvascular damage.

Early microvascular and neuronal consequences of traumatic brain injury: a light and electron microscopic study in rats

The purpose of this study was to document the early morphologic consequences of moderate traumatic brain injury (TBI) in anesthetized Sprague-Dawley rats. Normothermic rats (37 degrees C) were injured with a fluid percussion pulse (1.7-2.1 atm) administered by an injury cannula positioned parasagittally over the right cerebral cortex (n = 7). At 45 min following TBI, rats were injected with the protein tracer horseradish peroxidase (HRP) and perfusion fixed or immersion fixed 15 min later for light and electron microscopic analysis. Blood-brain barrier (BBB) breakdown to HRP was present overlying the pial surface and superficial cortical layers of the injured hemisphere. A focal area of severe HRP leakage was also present at the gray-white interface of the lateral cortex. Light microscopic examination of this site revealed petechial hemorrhages associated with small venules. Dark shrunken neurons and swollen astrocytes were detected within cortical areas overlying the evolving contusion, CA3 and CA4 hippocampal subsectors, and lateral thalamus. Ultrastructural studies obtained evidence for irreversible neuronal injury and mechanical damage to vessel walls at this early posttraumatic period. In nonperfused traumatized rats, luminal platelet aggregates were also detected at sites of hemorrhage. In this model of TBI, a consistent pattern of microvascular and neuronal abnormalities can be documented in the early posttraumatic period. Pathomechanisms underlying these early changes are discussed in terms of primary and secondary injury processes.

Microvascular and neuronal consequences of common carotid artery thrombosis and platelet embolization in rats

The microvascular and neuronal consequences of nonocclusive common carotid artery (CCA) thrombosis were documented in rats. Thrombosis of the CCA was produced by a rose bengal-mediated photochemical insult and regional patterns of blood-brain barrier (BBB) disruption were documented by horseradish peroxidase (HRP) histochemistry at 15 min (n = 12), 4 h (n = 3), 1 day (n = 5) or 7 days (n = 5) after vascular injury. At 15 min and 4 h after thrombosis, multiple foci of BBB disruption were present throughout the thrombosed hemisphere; protein leakage was occasionally detected contralaterally. Extravasated HRP was associated with well-perfused arterioles and arterioles containing luminal platelet aggregates at different stages of degranulation. Evidence for local platelet adhesion and aggregation or endothelial disruption at these sites was not detected. However, HRP-containing endothelial plasmalemmal vesicles were present at leaky sites. Variable degrees of parenchymal injury were documented including dendritic and astrocytic swelling with neuronal necrosis. By 1 day after CCA thrombosis, the overall frequency of permeable sites, more commonly associated with luminal leukocytes and parenchymal necrosis, was reduced. At 7 days, vessels permeable to HRP were associated with tissue necrosis, reactive astrocytes and microglial infiltration. Arteriole wall thickening and leukocyte accumulation within arterioles and venules were also detected. Widespread platelet embolization leading to variable degrees of BBB disruption and tissue injury occurs after CCA thrombosis. Acute abnormalities in vascular permeability are thus hypothesized to play an important role in the acute pathogenesis of cerebrovascular thrombosis. Delayed leukocyte accumulation in this model of embolic infarction may represent a secondary insult to the injured brain.

Intraventricular infusion of N-methyl-D-aspartate. 2. Acute neuronal consequences

This study documents the ultrastructural features of acute neuronal injury following N-methyl-D-aspartate (NMDA) receptor activation. NMDA (100 nmol/microliters) or vehicle was infused over a 15-min period into the lateral ventricle of adult rats. After perfusion fixation, specimens demonstrating normal and abnormal patterns of vascular permeability to horseradish peroxidase were sampled for ultrastructural analysis. In NMDA-infused rats, brain regions exhibiting protein extravasation contained swollen dendritic profiles and abnormal neuronal perikarya. Although periventricular regions were most severely affected, parenchymal abnormalities were also detected in the cerebral cortex, septum, striatum, thalamus, hypothalamus and cerebellum. Mildly affected dendrites contained dark compact mitochondria, while in severely swollen dendrites mitochondria were enlarged with ruptured cristae. Focal sites of plasma membrane disruption were also detected within swollen dendrites. Swollen neurons commonly displayed peripheral pallor and increased numbers of cytoplasmic vacuoles. Other neurons appeared dark and shrunken, some containing disrupted mitochondria and pyknotic nuclei. Pretreatment with the NMDA antagonist MK-801 (2 mg/kg) attenuated the neuronal and dendritic alterations. In conditions where cerebrospinal fluid levels of glutamate are abnormally elevated, excessive NMDA receptor activation may lead to early vascular and neuronal complications which could work in concert to promote brain injury.

Intraventricular infusion of N-methyl-D-aspartate. 1. Acute blood-brain barrier consequences

The purpose of this study was to document the early cerebrovascular consequences of excessive N-methyl-D-aspartate (NMDA) receptor activation. Five microliters of NMDA (100 nmol/microliters) or vehicle was infused over a 15-min period into the lateral ventricle of adult rats. The protein tracer horseradish peroxidase (HRP) was injected intravenously for blood-brain barrier (BBB) studies. The intraventricular infusion of vehicle (n = 5) caused no alterations in arterial blood pressure or microvascular damage away from the intraventricular probe tract. In contrast, NMDA infusion (n = 8) led to a gradual increase in arterial blood pressure (mean 36 mm Hg). Multifocal regions of HRP extravasation were observed bilaterally throughout the neuraxis following NMDA infusion. Sites of BBB disruption and hemorrhage included brain regions bordering ventricular spaces. In addition, isolated foci of protein extravasation were commonly detected in the cerebral cortex, thalamus, basal forebrain, septum and cerebellum. Pretreatment with the noncompetitive NMDA antagonist MK-801 (2 mg/kg) substantially reduced the BBB responses to NMDA. However, microvascular abnormalities were seen in NMDA-infused rats where blood pressure elevations were inhibited by blood removal. In addition to neurons, cerebral blood vessels are also acutely affected by NMDA receptor activation. Blockage of NMDA receptor channels following brain injury may potentially provide protection by attenuating BBB breakdown and subsequent brain edema.

Interrelationships between increased vascular permeability and acute neuronal damage following temperature-controlled brain ischemia in rats

This study examined regional patterns of increased vascular permeability and morphological indicators of acute neuronal injury following normothermic and mildly hyperthermic forebrain ischemia. Rats underwent 20 min of four-vessel occlusion during which intraischemic brain temperature was maintained at either 37 degrees C or 39 degrees C. At 45-min recirculation, the blood-brain barrier (BBB)-tracer horseradish peroxidase was injected and rats were perfusion-fixed at 1-h recirculation for light and electron microscopic analysis. In normothermic and hyperthermic rats, sites of increased vascular permeability were spatially correlated with dark shrunken type IV neurons. Neuronal alterations within cortical, hippocampal, striatal, and thalamic areas ranged from mild cytoplasmic vacuolation and mitochondrial swelling to severe cytoplasmic shrinkage and increased density. Although dark shrunken neurons were routinely associated with permeable blood vessels in both temperature groups, dark neurons were not detected in regions demonstrating an intact BBB. Following normothermic brain ischemia, the appearance of dark shrunken neurons was restricted to the cerebral cortex and striatum. In both temperature groups, luminal leukocytes were detected within otherwise well-perfused forebrain microvascular beds. Our studies suggest a close interrelationship between postischemic microvascular abnormalities, including increased vascular permeability, and morphological indicators of acute neuronal injury following brain ischemia.

The importance of brain temperature in alterations of the blood-brain barrier following cerebral ischemia

We studied whether small variations in intraischemic brain temperature influence the response of the blood-brain barrier (BBB) to transient forebrain global ischemia. Six animal subgroups included rats whose brain temperature was maintained at 30, 33, 36 or 39 degrees C during 20 minutes (min) of 4-vessel occlusion. Control rats without ischemia had brain temperature maintained between 30 and 39 degrees C for a 20 min period. After a 45 min postischemic recirculation period, rats were injected with the protein tracer, horseradish peroxidase (HRP), and perfusion fixed 5 or 15 min later. Control rats showed no leakage of the tracer protein. Postischemic rats in which brain temperature was controlled at either 30 or 33 degrees C failed to demonstrate consistent BBB alterations. In contrast, foci of cortical HRP extravasation were consistently documented in rats whose intraischemic brain temperature was 36 degrees C. Permeability alterations were more widespread in the 39 degrees C ischemic group and occurred in cortical, thalamic, hippocampal and striatal regions. The HRP extravasation frequently involved arterioles surrounded by perivascular spaces. Routes of increased permeability to HRP included endothelial pinocytosis, opening of the interendothelial tight junctions and diffuse leakage through damaged endothelial cells. These results demonstrate that brain temperature is a critical factor in determining whether BBB dysfunction is an acute consequence of a transient cerebral ischemic insult.