Exploring the Impact of ECHO Ontario Integrated Mental and Physical Health on Participants' Approach and Attitude Toward the Care of Patients With Complex Needs

OBJECTIVE

To examine how project Extension for Community Healthcare Outcomes-Integrated Mental and Physical Health (ECHO-IMPH) influences the attitudes and approaches of primary care providers and other participants towards patients.

METHODS

An exploratory qualitative approach was undertaken using semistructured interviews conducted between August 2020 and March 2021. One hundred and sixty-four individuals from two cycles of ECHO-IMPH were invited to participate, and 22 (n = 22) agreed to participate. Data were analyzed using the Braun and Clarke method for thematic analysis.

RESULTS

Three major themes were identified: 1) enhanced knowledge and skills; 2) changes in attitude and approach; 3) space for reflection and exploration. When participants were asked about areas for improvement, suggestions were focused on the structure of the sessions. Participants identified that ECHO-IMPH helped them to view patients more holistically, which led to greater patient-centered care in their practice. Additionally, skills gained in ECHO-IMPH gave participants the concrete tools needed to have more empathetic interactions with patients with complex needs.

CONCLUSIONS

ECHO-IMPH created a safe space for participants to reflect on their practice with patients with complex needs. Participants applied newly acquired knowledge and skills to provide more empathetic and patient-centered care for patients with complex needs. Based on the shift in perspectives described by participants, transformative learning theory was proposed as a model for how ECHO-IMPH created change in participants' practice.

Trends in Delirium and New Antipsychotic and Benzodiazepine Use Among Hospitalized Older Adults Before and After the Onset of the COVID-19 Pandemic

IMPORTANCE

The COVID-19 pandemic caused large disruptions to health care for hospitalized older adults. The incidence and management of delirium may have been affected by high rates of COVID-19 infection, staffing shortages, overwhelmed hospital capacity, and changes to visitor policies.

OBJECTIVE

To measure changes in rates of delirium and related medication prescribing during the COVID-19 pandemic among hospitalized older adults.

DESIGN, SETTING, AND PARTICIPANTS

This population-based, repeated cross-sectional study used linked databases to measure rates of delirium and related medication prescriptions among adults aged 66 years or older hospitalized before and during the COVID-19 pandemic (January 1, 2017, to March 31, 2022) in Ontario, Canada.

EXPOSURE

The first 2 years of the COVID-19 pandemic (March 1, 2020, to March 31, 2022).

MAIN OUTCOMES AND MEASURES

The main outcomes were weekly rates of delirium per 1000 admitted population and monthly rates of new antipsychotic and benzodiazepine prescriptions per 1000 discharged population. Observed rates were compared with projected rates based on modeling from 3 years before pandemic onset.

RESULTS

Among 2 128 411 hospitalizations of older adults over the 5-year study period (50.7% female; mean [SD] age, 78.9 [8.3] years), absolute rates of delirium increased from 35.9 per 1000 admitted population during the prepandemic period to 41.5 per 1000 admitted population throughout the pandemic. The adjusted rate ratio (ARR) of delirium during the pandemic compared with the projected rate was 1.15 (95% CI, 1.11-1.19). Monthly rates of new antipsychotic prescriptions increased from 6.9 to 8.8 per 1000 discharged population and new benzodiazepine prescriptions from 4.4 to 6.0 per 1000 discharged population and were significantly higher during the pandemic compared with projected rates (antipsychotics: ARR, 1.28; 95% CI, 1.19-1.38; benzodiazepines: ARR, 1.37; 95% CI, 1.20-1.57). Rates were highest during pandemic waves 1 (March to June 2020), 3 (March to June 2021), and 5 (December 2021 to February 2022) and remained elevated above projected levels throughout the first 2 years of the pandemic.

CONCLUSIONS AND RELEVANCE

In this repeated cross-sectional study of hospitalized older adults, there was a temporal association between COVID-19 pandemic onset and significant increases in rates of delirium in the hospital and new antipsychotic and benzodiazepine prescriptions after hospital discharge. Rates remained elevated over 2 years. Pandemic-related changes such as visitor restrictions, staff shortages, isolation practices, and reduced staff time at the bedside may have contributed to these trends.

Data-driven approach to identifying potential laboratory overuse in general internal medicine (GIM) inpatients

BACKGROUND

Reducing laboratory test overuse is important for high quality, patient-centred care. Identifying priorities to reduce low value testing remains a challenge.

OBJECTIVE

To develop a simple, data-driven approach to identify potential sources of laboratory overuse by combining the total cost, proportion of abnormal results and physician-level variation in use of laboratory tests.

DESIGN, SETTING AND PARTICIPANTS

A multicentre, retrospective study at three academic hospitals in Toronto, Canada. All general internal medicine (GIM) hospitalisations between 1 April 2010 and 31 October 2017.

RESULTS

There were 106 813 GIM hospitalisations during the study period, with median hospital length-of-stay of 4.6 days (IQR: 2.33-9.19). There were 21 tests which had a cumulative cost >US$15 400 at all three sites. The costliest test was plasma electrolytes (US$4 907 775), the test with the lowest proportion of abnormal results was red cell folate (0.2%) and the test with the greatest physician-level variation in use was antiphospholipid antibodies (coefficient of variation 3.08). The five tests with the highest cumulative rank based on greatest cost, lowest proportion of abnormal results and highest physician-level variation were: (1) lactate, (2) antiphospholipid antibodies, (3) magnesium, (4) troponin and (5) partial thromboplastin time. In addition, this method identified unique tests that may be a potential source of laboratory overuse at each hospital.

CONCLUSIONS

A simple multidimensional, data-driven approach combining cost, proportion of abnormal results and physician-level variation can inform interventions to reduce laboratory test overuse. Reducing low value laboratory testing is important to promote high value, patient-centred care.

"Addressing the bigger picture": A qualitative study of internal medicine patients' perspectives on social needs data collection and use

BACKGROUND

There is increasing interest in collecting sociodemographic and social needs data in hospital settings to inform patient care and health equity. However, few studies have examined inpatients' views on this data collection and what should be done to address social needs. This study describes internal medicine inpatients' perspectives on the collection and use of sociodemographic and social needs information.

METHODS

A qualitative interpretive description methodology was used. Semi-structured interviews were conducted with 18 patients admitted to a large academic hospital in Toronto, Canada. Participants were recruited using maximum variation sampling for diverse genders, races, and those with and without social needs. Interviews were coded using a predominantly inductive approach and a thematic analysis was conducted.

RESULTS

Patients expressed that sociodemographic and social needs data collection is important to offer actionable solutions to address their needs. Patients described a gap between their ideal care which would attend to social needs, versus the reality that hospital-based teams are faced with competing priorities and pressures that make it unfeasible to provide such care. They also believed that this data collection could facilitate more holistic, integrated care. Patients conveyed a need to have a trusting and transparent relationship with their provider to alleviate concerns surrounding bias, discrimination, and confidentiality. Lastly, they indicated that sociodemographic and social needs data could be useful to inform care, support research to inspire social change, and assist them with navigating community resources or creating in-hospital programs to address unmet social needs.

CONCLUSIONS

While the collection of sociodemographic and social needs information in hospital settings is generally acceptable, there were varied views on whether hospital staff should intervene, as their priority is medical care. The results can inform the implementation of social data collection and interventions in hospital settings.

"Don't Just Study our Distress, Do Something": Implementing and Evaluating a Modified Stepped-Care Model for Health Care Worker Mental Health During the COVID-19 Pandemic

OBJECTIVE

Throughout the COVID-19 pandemic, there have been concerns about the mental health of health care workers (HCW). Although numerous studies have investigated the level of distress among HCW, few studies have explored programs to improve their mental well-being. In this paper, we describe the implementation and evaluation of a program to support the mental health of HCW at University Health Network (UHN), Canada's largest healthcare network.

METHODS

Using a quality improvement approach, we conducted a needs assessment and then created and evaluated a modified stepped-care model to address HCW mental health during the pandemic. This included: online resources focused on psychoeducation and self-management, access to online support and psychotherapeutic groups, and self-referral for individual care from a psychologist or psychiatrist. We used ongoing mixed-methods evaluation, combining quantitative and qualitative analysis, to improve program quality.

RESULTS

The program is ongoing, running continuously throughout the pandemic. We present data up to November 30, 2021. There were over 12,000 hits to the UHN's COVID mental health intranet web page, which included self-management resources and information on group support. One hundred and sixty-six people self-referred for individual psychological or psychiatric care. The mean wait time from referral to initial appointment was 5.4 days, with an average of seven appointments for each service user. The majority had moderate to severe symptoms of depression and anxiety at referral, with over 20% expressing thoughts of self-harm or suicide. Post-care user feedback, collected through self-report surveys and semistructured interviews, indicated that the program is effective and valued.

CONCLUSIONS

Development of a high-quality internal mental health support for HCW program is feasible, effective, and highly valued. By using early and frequent feedback from multiple perspectives and stakeholders to address demand and implement changes responsively, the program was adjusted to meet HCW mental health needs as the pandemic evolved.

Boosting Delirium Identification Accuracy With Sentiment-Based Natural Language Processing: Mixed Methods Study

BACKGROUND

Delirium is an acute neurocognitive disorder that affects up to half of older hospitalized medical patients and can lead to dementia, longer hospital stays, increased health costs, and death. Although delirium can be prevented and treated, it is difficult to identify and predict.

OBJECTIVE

This study aimed to improve machine learning models that retrospectively identify the presence of delirium during hospital stays (eg, to measure the effectiveness of delirium prevention interventions) by using the natural language processing (NLP) technique of sentiment analysis (in this case a feature that identifies sentiment toward, or away from, a delirium diagnosis).

METHODS

Using data from the General Medicine Inpatient Initiative, a Canadian hospital data and analytics network, a detailed manual review of medical records was conducted from nearly 4000 admissions at 6 Toronto area hospitals. Furthermore, 25.74% (994/3862) of the eligible hospital admissions were labeled as having delirium. Using the data set collected from this study, we developed machine learning models with, and without, the benefit of NLP methods applied to diagnostic imaging reports, and we asked the question "can NLP improve machine learning identification of delirium?"

RESULTS

Among the eligible 3862 hospital admissions, 994 (25.74%) admissions were labeled as having delirium. Identification and calibration of the models were satisfactory. The accuracy and area under the receiver operating characteristic curve of the main model with NLP in the independent testing data set were 0.807 and 0.930, respectively. The accuracy and area under the receiver operating characteristic curve of the main model without NLP in the independent testing data set were 0.811 and 0.869, respectively. Model performance was also found to be stable over the 5-year period used in the experiment, with identification for a likely future holdout test set being no worse than identification for retrospective holdout test sets.

CONCLUSIONS

Our machine learning model that included NLP (ie, sentiment analysis in medical image description text mining) produced valid identification of delirium with the sentiment analysis, providing significant additional benefit over the model without NLP.

Abstract WMP54: Stroke Secondary Prevention Care In Persons With Schizophrenia

Introduction: Schizophrenia is associated with stroke incidence and case-fatality but the causes of this are not well-understood. We evaluated the association between comorbid schizophrenia and the quality of secondary prevention care after ischemic stroke.

Methods: We used linked health administrative data to identify adults discharged alive from acute care hospitals in Ontario, Canada between 2004 and 2017 following an incident ischemic stroke and identified those with a history of schizophrenia using a validated algorithm. Outcomes were screening, treatment among those with the risk factor, control of vascular risk factors, and receipt of outpatient physician services. We used modified Poisson regression to model the relative risk of each indicator outcome among persons with and without schizophrenia who were alive one year after discharge, adjusting for age, sex, income, comorbidity and rural residence.

Results: Among 85,046 persons with ischemic stroke, 886 (1.04%) had a diagnosis of schizophrenia. Those with schizophrenia were younger (median age 64 vs 72), more likely to be female (50.1% vs 44.6%), live in the lowest neighbourhood income quintile (41.1% vs 23.0%) and have diabetes (42.8% vs 32.3%). Of those alive 1 year after stroke, those with schizophrenia were less likely to be screened for hyperlipidemia (adjusted relative risk (aRR) 0.89; 95% confidence interval (CI) 0.84 to 0.94) or diabetes (aRR 0.93; 95% CI 0.89 to 0.97), be prescribed antihypertensive agents (aRR 0.96; 95% CI 0.93 to 0.99), or achieve target lipid levels (LDL < 2 mml/L) (aRR 0.87; 95% CI 0.78 to 0.96). There were no differences in prescription of antilipemic (aRR 0.96; 95% CI 0.91 to 1.01) or antiglycemic (aRR 0.95; 95% CI 0.87 to 1.03) agents or in achievement of target HbA1c ≤ 7% (aRR 0.89; 95% CI 0.78 to 1.02). Outpatient stroke specialist care in the 3 months after discharge was less likely among those with schizophrenia (aRR 0.72; 95% CI 0.65 to 0.78) as were visits to primary care physicians (aRR 0.93; 95% CI 0.91 to 0.96).

Conclusions: People with schizophrenia and stroke are less likely to receive secondary preventive care across many indicators measured. This information may be useful for targeted interventions to improve post-stroke care in those with schizophrenia.

Individual- and Institutional-level Concerns of Health Care Workers in Canada During the COVID-19 Pandemic: A Qualitative Analysis

IMPORTANCE

Mental health and coping difficulties among health care workers (HCWs) have been reported during pandemics and particularly during the COVID-19 pandemic.

OBJECTIVE

To examine sources of distress and concern for HCWs in Canada during the COVID-19 pandemic.

DESIGN, SETTING, AND PARTICIPANTS

In this qualitative study, a critical discourse analysis was performed of questions posed by HCWs to hospital senior leadership between March 16, 2020, and December 1, 2020, through an online employee forum as part of a larger mixed-methods evaluation of a stepped-care mental health support program for HCWs at 1 of Canada's largest health care institutions. Questions could be submitted online anonymously in advance of the virtual forums on COVID-19 by any of the University Health Network's 21 555 employees, and staff members were able to anonymously endorse questions by upvoting, indicating that an already posed question was of interest.

MAIN OUTCOMES AND MEASURES

Themes, text structure, and rhetorical devices used within the questions were analyzed, taking into consideration their larger institutional and societal context.

RESULTS

Unique individual views of the forums ranged from 2062 to 7213 during the study period. Major individual-level concerns related to risks of contamination and challenges coping with increased workloads as a result of the pandemic intersected with institutional-level challenges, such as feeling or being valued within the health care setting and long-standing stratifications between types of HCWs. Concerns were frequently reported in terms of calls for clarity or demands for transparency from the institutional leadership.

CONCLUSIONS AND RELEVANCE

The findings of this qualitative study suggest that larger institutional-level and structural concerns need to be addressed if HCWs are to be engaged in support and coping programs. Potential service users may be dissuaded from seeing their needs as being met by workplace mental health interventions that solely relate to individual-level concerns.

Stroke care and case fatality in people with and without schizophrenia: a retrospective cohort study

BACKGROUND

Schizophrenia is associated with an increased risk of death following stroke; however, the magnitude and underlying reasons for this are not well understood.

OBJECTIVE

To determine the association between schizophrenia and stroke case fatality, adjusting for baseline characteristics, stroke severity and processes of care.

DESIGN

Retrospective cohort study used linked clinical and administrative databases.

SETTING

All acute care institutions (N=152) in the province of Ontario, Canada.

PARTICIPANTS

All patients (N=52 473) hospitalised with stroke between 1 April 2002 and 31 March 2013 and included in the Ontario Stroke Registry. Those with schizophrenia (n=612) were identified using validated algorithms.

MAIN OUTCOMES AND MEASURES

We compared acute stroke care in those with and without schizophrenia and used Cox proportional hazards models to examine the association between schizophrenia and mortality, adjusting for demographics, comorbidity, stroke severity and processes of care.

RESULTS

Compared with those without schizophrenia, people with schizophrenia were less likely to undergo thrombolysis (10.1% vs 13.4%), carotid imaging (66.3% vs 74.0%), rehabilitation (36.6% vs 46.6% among those with disability at discharge) or be treated with antihypertensive, lipid-lowering or anticoagulant therapies. After adjustment for age and other factors, schizophrenia was associated with death from any cause at 1 year (adjusted HR (aHR) 1.33, 95% CI 1.14 to 1.54). This was mainly attributable to early deaths from stroke (aHR 1.47, 95% CI 1.20 to 1.80, with survival curves separating in the first 30 days), and the survival disadvantage was particularly marked in those aged over 70 years (1-year mortality 46.9% vs 35.0%).

CONCLUSIONS

Schizophrenia is associated with increased stroke case fatality, which is not fully explained by stroke severity, measurable comorbid conditions or processes of care. Future work should focus on understanding this mortality gap and on improving acute stroke and secondary preventive care in people with schizophrenia.

Prospective study of psychiatric illness as a predictor of weight loss and health related quality of life one year after bariatric surgery

OBJECTIVE

Despite a lack of evidence, there is an assumption that patients with more complex psychiatric histories (CPH) prior to bariatric surgery have poor post-surgical weight loss and worsening psychiatric symptoms following surgery. Consequently, those with CPH are excluded from bariatric surgery in many bariatric clinics. This study examines whether psychiatric illness affects post-surgical weight loss and HRQOL, focusing on patients with CPH.

METHOD

This prospective cohort study investigated 341 patients from a tertiary care centre bariatric surgery program who had surgery between September 2010 and October 2013. Patients were divided into CPH, other psychiatric disorder (OPD), or no psychiatric disorder (NPD) groups based on lifetime psychiatric diagnoses. Groups were compared one year post-surgery in regards to percent total weight loss (%TWL), mental and physical health related quality of life (HRQOL) using a Kruskal-Wallist test. Linear regression analysis was used to determine if mental illness group, gender, age, pre-op BMI, education, employment and relationship status predict change in %TWL and HRQOL.

RESULTS

There was no significant difference in %TWL or physical HRQOL across groups. The CPH group experienced a decrease in mental HRQOL (p=0.0003). Mental illness severity predicted mental HRQOL (p=0.002) but not physical HRQOL or %TWL.

CONCLUSION

Those with controlled CPH can achieve comparable weight loss compared to those with OPD or NPD. However, CPH may predict post-surgical decline in mental HRQOL. These findings demonstrate a need to reevaluate exclusion criteria to ensure equitable access to care, while continuing to monitor for psychiatric illness following surgery.

Turning points for perpetrators of intimate partner violence

Understanding why and how perpetrators of intimate partner violence (IPV) change their behavior is an important goal for both policy development and clinical practice. In this study, the authors investigated the concept of "turning points" for perpetrators of IPV by conducting a systematic review of qualitative studies that investigated the factors, situations, and attitudes that facilitated perpetrators' decisions to change their abusive behavior. Two literature databases were searched and six studies were found that met the inclusion criteria for the systematic review. Most included participants from batterer intervention programs (BIPs). The data indicate that community, group, and individual processes all contribute to perpetrators' turning points and behavioral change. These include identifying key incidents that precede change, taking responsibility for past behavior, learning new skills, and developing relationships within and outside of the BIP. By using a qualitative systematic review, the authors were able to generate a more complete understanding of the catalysts for and process of change in these individuals. Further research, combining quantitative and qualitative approaches, will be helpful in the modification of existing BIPs and the development of new interventions to reduce IPV.

Is discrimination training necessary to cause changes in the P2 auditory event-related brain potential to speech sounds?

Previous studies have found that the P2 component of the auditory event-related potential (ERP) increases after speech discrimination training. We compared electrophysiological and behavioral outcomes of individuals undergoing speech discrimination training (N = 8) with an untrained control group (N = 9). Significant improvements on the behavioral speech discrimination task were found only in the trained group; however, there were similar increases in P2 amplitude in both groups. Simple exposure to repeated instances of a speech sound during the ERP recording seems sufficient lead to enhancement of P2. This interpretation was bolstered by the finding of significant change in P2 during the first and second halves of the initial ERP recording, when listeners were not required to make any discriminative response. However, the largest change in P2 occurred between rather than within recording sessions, suggesting that the effects of exposure to a speech stimulus on ERPs may have a slow time-course and are most evident after a delay. Our data challenge the view that increased P2 amplitude reflects enhanced perceptual discrimination by auditory cortex.

Activation and propagation of Ca(2+) release during excitation-contraction coupling in atrial myocytes

Fast two-dimensional confocal microscopy and the Ca(2+) indicator fluo-4 were used to study excitation-contraction (E-C) coupling in cat atrial myocytes which lack transverse tubules and contain both subsarcolemmal junctional (j-SR) and central nonjunctional (nj-SR) sarcoplasmic reticulum. Action potentials elicited by field stimulation induced transient increases of intracellular Ca(2+) concentration ([Ca(2+)](i)) that were highly inhomogeneous. Increases started at distinct subsarcolemmal release sites spaced approximately 2 microm apart. The amplitude and the latency of Ca(2+) release from these sites varied from beat to beat. Subsarcolemmal release fused to build a peripheral ring of elevated [Ca(2+)](i), which actively propagated to the center of the cells via Ca(2+)-induced Ca(2+) release. Resting myocytes exhibited spontaneous Ca(2+) release events, including Ca(2+) sparks and local (microscopic) or global (macroscopic) [Ca(2+)](i) waves. The microscopic [Ca(2+)](i) waves propagated in a saltatory fashion along the sarcolemma ("coupled" Ca(2+) sparks) revealing the sequential activation of Ca(2+) release sites of the j-SR. Moreover, during global [Ca(2+)](i) waves, Ca(2+) release was evident from individual nj-SR sites. Ca(2+) release sites were arranged in a regular three-dimensional grid as deduced from the functional data and shown by immunostaining of ryanodine receptor Ca(2+) release channels. The longitudinal and transverse distances between individual Ca(2+) release sites were both approximately 2 microm. Furthermore, electron microscopy revealed a continuous sarcotubular network and one peripheral coupling of j-SR with the sarcolemma per sarcomere. The results demonstrate directly that, in cat atrial myocytes, the action potential-induced whole-cell [Ca(2+)](i) transient is the spatio-temporal summation of Ca(2+) release from subsarcolemmal and central sites. First, j-SR sites are activated in a stochastic fashion by the opening of voltage-dependent sarcolemmal Ca(2+) channels. Subsequently, nj-SR sites are activated by Ca(2+)-induced Ca(2+) release propagating from the periphery.

Functional coupling between glycolysis and excitation-contraction coupling underlies alternans in cat heart cells

Electromechanical alternans was characterized in single cat atrial and ventricular myocytes by simultaneous measurements of action potentials, membrane current, cell shortening and changes in intracellular Ca2+ concentration ([Ca2+]i). Using laser scanning confocal fluorescence microscopy, alternans of electrically evoked [Ca2+]i transients revealed marked differences between atrial and ventricular myocytes. In ventricular myocytes, electrically evoked [Ca2+]i transients during alternans were spatially homogeneous. In atrial cells Ca2+ release started at subsarcolemmal peripheral regions and subsequently spread toward the centre of the myocyte. In contrast to ventricular myocytes, in atrial cells propagation of Ca2+ release from the sarcoplasmic reticulum (SR) during the small-amplitude [Ca2+]i transient was incomplete, leading to failures of excitation-contraction (EC) coupling in central regions of the cell. The mechanism underlying alternans was explored by evaluating the trigger signal for SR Ca2+ release (voltage-gated L-type Ca2+ current, ICa,L) and SR Ca2+ load during alternans. Voltage-clamp experiments revealed that peak ICa,L was not affected during alternans when measured simultaneously with changes of cell shortening. The SR Ca2+ content, evaluated by application of caffeine pulses, was identical following the small-amplitude and the large-amplitude [Ca2+]i transient. These results suggest that the primary mechanism responsible for cardiac alternans does not reside in the trigger signal for Ca2+ release and SR Ca2+ load. beta-Adrenergic stimulation with isoproterenol (isoprenaline) reversed electromechanical alternans, suggesting that under conditions of positive cardiac inotropy and enhanced efficiency of EC coupling alternans is less likely to occur. The occurrence of electromechanical alternans could be elicited by impairment of glycolysis. Inhibition of glycolytic flux by application of pyruvate, iodoacetate or beta-hydroxybutyrate induced electromechanical and [Ca2+]i transient alternans in both atrial and ventricular myocytes. The data support the conclusion that in cardiac myocytes alternans is the result of periodic alterations in the gain of EC coupling, i. e. the efficacy of a given trigger signal to release Ca2+ from the SR. It is suggested that the efficiency of EC coupling is locally controlled in the microenvironment of the SR Ca2+ release sites by mechanisms utilizing ATP, produced by glycolytic enzymes closely associated with the release channel.

Divalent cation permeability and blockade of Ca2+-permeant non-selective cation channels in rat adrenal zona glomerulosa cells

1. The effects of the divalent cations Ca2+, Mg2+ and Ni2+ on unitary Na+ currents through receptor-regulated non-selective cation channels were studied in inside-out and cell-attached patches from rat adrenal zona glomerulosa cells. 2. External Ca2+ caused a concentration-dependent and voltage-independent inhibition of inward Na+ current, exhibiting an IC50 of 1.4 mM. The channel was also Ca2+ permeant and external Ca2+ shifted the reversal potential as expected for a channel exhibiting a constant Ca2+ : Na+ permeability ratio near to 4. 3. External and internal 2 mM Mg2+ caused voltage-dependent inhibition of inward and outward Na+ current, respectively. Modelling Mg2+ as an impermeant fast open channel blocker indicated that external Mg2+ blocked the pore at a single site exhibiting a zero voltage Kd of 5.1 mM for Mg2+ and located 19 % of the distance through the transmembrane electric field from the external surface. Internal Mg2+ blocked the pore at a second site exhibiting a Kd of 1.7 mM for Mg2+ and located 36% of the distance through the transmembrane electric field from the cytosolic surface. 4. External Ni2+ caused a voltage- and concentration-dependent slow blockade of inward Na+ current. Modelling Ni2+ as an impermeant slow open channel blocker indicated that Ni2+ blocked the pore at a single site exhibiting a Kd of 1.09 mM for Ni2+ and located 13.7% of the distance through the transmembrane electric field from the external surface. 5. External 2 mM Mg2+ increased the Kd for external Ni2+ binding to 1.27 mM, consistent with competition for a single binding site. Changing ionic strength did not substantially affect Ni2+ blockade indicating the absence of surface potential under physiological ionic conditions. 6. It is concluded that at least two divalent cation binding sites, separated by a high free energy barrier (the selectivity filter), are located in the pore and contribute to Ca2+ selectivity and permeability of the channel.

Ambulatory EEG recordings in children with infrequent seizures

Twenty-one children, ages 1-15 years, were selected for outpatient ambulatory electroencephalographic (AEEG) monitoring on the basis of infrequent seizures without therapy, normal routine EEGs, and normal neurologic/developmental examinations. Technically satisfactory recordings were obtained in all patients; recording time consisted of 24, 22, and 6 hours for 15, 4, and 2 patients, respectively. Eighteen patients were not receiving antiepileptic drug therapy at AEEG. The follow-up intervals after the AEEG ranged from 4-20 months. Only 2 patients had epileptiform AEEGs. Of the remaining 19 with nonepileptiform records, 10 were seizure free without antiepileptic drug therapy, but 9 developed additional seizures which required treatment.

Comparison of the properties of [3H]-D-2-amino-5-phosphonopentanoic acid and [3H]-DL-2-amino-7-phosphonoheptanoic acid binding to homogenates of rat cerebral cortex

1. The pharmacology and ionic regulation of [3H]-2-D-2-amino-5-phosphonopentanoic acid ([3H]-D-AP5) and [3H]-DL-2-amino-7-phosphonoheptanoic acid ([3H]-DL-AP7) binding to homogenates of rat cerebral cortex were examined using radioligand binding methodology. 2. Both [3H]-D-AP5 and [3H]-DL-AP7 labelled a single population of binding sites with dissociation constants of 0.39 and 1.8 mumol/l, respectively. The density of binding sites found with [3H]-DL-AP7 was 13 times greater than that found with [3H]-D-AP5. 3. The ionic requirements of the [3H]-D-AP5 binding site in the presence of chloride were such that calcium acetate enhanced binding, while magnesium and sodium acetate both decreased binding. In the absence of chloride both calcium and chloride ions stimulated binding. 4. In a chloride-free buffer calcium acetate stimulated binding of [3H]-DL-AP7 in a biphasic manner. Chloride ions (ammonium salt) enhanced binding slightly at low concentrations (0.1-1.0 mmol/l) above which binding was reduced to non-specific levels. The ionic dependence of [3H]-DL-AP7 binding had some similarities to the previously defined GLU-C site. 5. The pharmacological profile of the site labelled by [3H]-D-AP5 was consistent with that of a recognition site for N-methyl-D-aspartate (NMDA) as defined in electrophysiological experiments. [3H]-DL-AP7 did not label an NMDA site as several non-NMDA ligands displaced binding with high affinity and the binding was not stereospecific as found for [3H]-D-AP5. Moreover, the pharmacological profile of the [3H]-DL-AP7 site did not correspond to any excitatory amino acid receptor as presently defined.

Absence of N-methyl-D-aspartate receptors on ovine cerebral microvessels

Radioreceptor methods were used to quantitate the N-methyl-D-aspartate (NMDA) receptor-complex of ovine cerebral microvessels and cerebral gray matter. Specific binding of D[3H]2-amino-5-phosphono-pentanoate and [3H]1-[1-(2-thienyl)cyclohexyl]piperidine, ligands for the NMDA primary acceptor site and ionophore, respectively, was found in cerebral gray matter but was not detectable in membranes prepared from brain microvessels enriched in capillaries. Sigma receptors, another locus of action for phencyclidine congeners, were also not present on microvessels but were found in cortical homogenates. On the other hand, cerebral microvessels and gray matter contained significant numbers of beta-adrenoceptors. Our results indicate the NMDA receptors and NMDA antagonists are unlikely to regulate the function of the cerebral microvasculature.