Stroke thrombolysis: Barriers to implementation

What would other emergency stroke teams do? Using explainable machine learning to understand variation in thrombolysis practice

INTRODUCTION

The aim of this work was to understand between-hospital variation in thrombolysis use among emergency stroke admissions in England and Wales.

PATIENTS

A total of 88,928 patients who arrived at all 132 emergency stroke hospitals in England Wales within 4 h of stroke onset, from 2016 to 2018.

METHODS

Machine learning was applied to the Sentinel Stroke National Audit Programme (SSNAP) data set, to learn which patients in each hospital would likely receive thrombolysis. We used XGBoost machine learning models, coupled with a SHAP model for explainability; Shapley (SHAP) values, providing estimates of how patient features, and hospital identity, influence the odds of receiving thrombolysis.

RESULTS

Thrombolysis use in patients arriving within 4 h of known or estimated stroke onset ranged 7% -49% between hospitals. The odds of receiving thrombolysis reduced 9-fold over the first 120 min of arrival-to-scan time, varied 30-fold with stroke severity, reduced 3-fold with estimated rather than precise stroke onset time, fell 6-fold with increasing pre-stroke disability, fell 4-fold with onset during sleep, fell 5-fold with use of anticoagulants, fell 2-fold between 80 and 110 years of age, reduced 3-fold between 120 and 240 min of onset-to-arrival time and varied 13-fold between hospitals. The majority of between-hospital variance was explained by the hospital, rather than the differences in local patient populations.

CONCLUSIONS

Using explainable machine learning, we identified that the majority of the between-hospital variation in thrombolysis use in England and Wales may be explained by differences in in-hospital processes and differences in attitudes to judging suitability for thrombolysis.

National implementation of reperfusion for acute ischaemic stroke in England: How should services be configured? A modelling study

Objectives

To guide policy when planning thrombolysis (IVT) and thrombectomy (MT) services for acute stroke in England, focussing on the choice between ‘mothership’ (direct conveyance to an MT centre) and ‘drip-and-ship’ (secondary transfer) provision and the impact of bypassing local acute stroke centres.

Design

Outcome-based modelling study.

Setting

107 acute stroke centres in England, 24 of which provide IVT and MT (IVT/MT centres) and 83 provide only IVT (IVT-only units).

Participants

242,874 emergency admissions with acute stroke over 3 years (2015–2017).

Intervention

Reperfusion delivered by drip-and-ship, mothership or ‘hybrid’ models; impact of additional travel time to directly access an IVT/MT centre by bypassing a more local IVT-only unit; effect of pre-hospital selection for large artery occlusion (LAO).

Main outcome measures

Population benefit from reperfusion, time to IVT and MT, admission numbers to IVT-only units and IVT/MT centres.

Results

Without pre-hospital selection for LAO, 94% of the population of England live in areas where the greatest clinical benefit, assuming unknown patient status, accrues from direct conveyance to an IVT/MT centre. However, this policy produces unsustainable admission numbers at these centres, with 78 out of 83 IVT-only units receiving fewer than 300 admissions per year (compared to 3 with drip-and-ship). Implementing a maximum permitted additional travel time to bypass an IVT-only unit, using a pre-hospital test for LAO, and selecting patients based on stroke onset time, all help to mitigate the destabilising effect but there is still some significant disruption to admission numbers, and improved selection of patients suitable for MT selectively reduces the number of patients who would receive IVT at IVT-only centres, challenging the sustainability of IVT expertise in IVT-only centres.

Conclusions

Implementation of reperfusion for acute stroke based solely on achieving the maximum population benefit potentially leads to destabilisation of the emergency stroke care system. Careful planning is required to create a sustainable system, and modelling may be used to help planners maximise benefit from reperfusion while creating a sustainable emergency stroke care system.

Understanding delays in acute stroke care: a systematic review of reviews

Background

Stroke is the leading cause of adult long-term disability in Western countries. Intravenous thrombolytic therapy with recombinant tissue plasminogen activator is safe and effective within the first 4.5 h after the onset of stroke. Various factors delaying acute stroke care have been identified in the literature. This review aimed to provide an overview of factors delaying acute stroke care and attempted to show how they interact in a synthetic framework.

Methods

We conducted a systematic review of literature reviews published in Medline and DORIS until 2016 on factors influencing acute stroke pathway timeframe.

Results

We analyzed 31 reviews that cover all factors of delays from stroke onset to treatment. We identified 27 factors that had a significant impact on acute stroke care and can be categorized into four distinct categories: patient-related factors, training, resources and lack of coordination. We also reported associations between factors observed in both between categories (mainly between patients and organizational/logistical factors) and within categories.

Conclusion

This review provides a wide overview of factors influencing acute stroke pathway. Since it was observed that the identified factors were interrelated, they needed to be analyzed in a systematic way. We hence created a synthetic framework that combines several categories of factors while assuming that factor weight varies from a study context to another. Better knowledge on underlying mechanisms between factors would provide crucial improvement of the interventions aiming at reducing delays in both pre-hospital and inhospital stages. For future research, we recommend adopting a systemic perspective on factors influencing acute stroke pathway.

Feasibility of a hyper-acute stroke unit model of care across England: a modelling analysis

OBJECTIVES

The policy of centralising hyperacute stroke units (HASUs) in England aims to provide stroke care in units that are both large enough to sustain expertise (>600 admissions/year) and dispersed enough to rapidly deliver time-critical treatments (<30 min maximum travel time). Currently, just over half (56%) of patients with stroke access care in such a unit. We sought to model national configurations of HASUs that would optimise both institutional size and geographical access to stroke care, to maximise the population benefit from the centralisation of stroke care.

DESIGN

Modelling of the effect of the national reconfiguration of stroke services. Optimal solutions were identified using a heuristic genetic algorithm.

SETTING

127 acute stroke services in England, serving a population of 54 million people.

PARTICIPANTS

238 887 emergency admissions with acute stroke over a 3-year period (2013-2015).

INTERVENTION

Modelled reconfigurations of HASUs optimised for institutional size and geographical access.

MAIN OUTCOME MEASURE

Travel distances and times to HASUs, proportion of patients attending a HASU with at least 600 admissions per year, and minimum and maximum HASU admissions.

RESULTS

Solutions were identified with 75-85 HASUs with annual stroke admissions in the range of 600-2000, which achieve up to 82% of patients attending a stroke unit within 30 min estimated travel time (with at least 95% and 98% of the patients being within 45 and 60 min travel time, respectively).

CONCLUSIONS

The reconfiguration of hyperacute stroke services in England could lead to all patients being treated in a HASU with between 600 and 2000 admissions per year. However, the proportion of patients within 30 min of a HASU would fall from over 90% to 80%-82%.

Recent advances in targeted delivery of tissue plasminogen activator for enhanced thrombolysis in ischaemic stroke

Tissue plasminogen activator (tPA) is the only FDA approved medical treatment for the ischaemic stroke. However, it associates with some inevitable limitations, including: short therapeutic window, extremely short half-life and low penetration in large clots. Systemic administration may lead to complications such as haemorrhagic conversion in the brain and relapse in the form of re-occlusion. Furthermore, ultrasound has been utilised in combination with contrast agents, echogenic liposome, microspheres or nanoparticles (NPs) carrying tPA for improving thrombolysis - an approach that has resulted in slight improvement of tPA delivery and facilitated thrombolysis. Most of these delivery systems are able to extend the circulating half-life and clot penetration of tPA. Various technologies employed for ameliorated thrombolytic therapy are in different phases, some are in final steps for clinical applications while some others are under investigations for their safety and efficacy in human cases. Here, recent progresses on the thrombolytic therapy using novel nano- and micro-systems incorporating tPA are articulated. Of these, liposomes and microspheres, polymeric NPs and magnetic nanoparticles (MNPs) are discussed. Key technologies implemented for efficient delivery of tPA and advanced thrombolytic therapy and their advantages/disadvantages are further expressed.

Identifying the barriers and enablers for a triage, treatment, and transfer clinical intervention to manage acute stroke patients in the emergency department: a systematic review using the theoretical domains framework (TDF)

Background

Clinical guidelines recommend that assessment and management of patients with stroke commences early including in emergency departments (ED). To inform the development of an implementation intervention targeted in ED, we conducted a systematic review of qualitative and quantitative studies to identify relevant barriers and enablers to six key clinical behaviours in acute stroke care: appropriate triage, thrombolysis administration, monitoring and management of temperature, blood glucose levels, and of swallowing difficulties and transfer of stroke patients in ED.

Methods

Studies of any design, conducted in ED, where barriers or enablers based on primary data were identified for one or more of these six clinical behaviours. Major biomedical databases (CINAHL, OVID SP EMBASE, OVID SP MEDLINE) were searched using comprehensive search strategies. The barriers and enablers were categorised using the theoretical domains framework (TDF). The behaviour change technique (BCT) that best aligned to the strategy each enabler represented was selected for each of the reported enablers using a standard taxonomy.

Results

Five qualitative studies and four surveys out of the 44 studies identified met the selection criteria. The majority of barriers reported corresponded with the TDF domains of “environmental, context and resources” (such as stressful working conditions or lack of resources) and “knowledge” (such as lack of guideline awareness or familiarity). The majority of enablers corresponded with the domains of “knowledge” (such as education for physicians on the calculated risk of haemorrhage following intravenous thrombolysis [tPA]) and “skills” (such as providing opportunity to treat stroke cases of varying complexity). The total number of BCTs assigned was 18. The BCTs most frequently assigned to the reported enablers were “focus on past success” and “information about health consequences.”

Conclusions

Barriers and enablers for the delivery of key evidence-based protocols in an emergency setting have been identified and interpreted within a relevant theoretical framework. This new knowledge has since been used to select specific BCTs to implement evidence-based care in an ED setting. It is recommended that findings from similar future reviews adopt a similar theoretical approach. In particular, the use of existing matrices to assist the selection of relevant BCTs.

Does the 'diffusion of innovations' model enrich understanding of research use? Case studies of the implementation of thrombolysis services for stroke

OBJECTIVE

To test whether the model of 'diffusion of innovations' enriches understanding of the implementation of evidence-based thrombolysis services for stroke patients.

METHODS

Four case studies of the implementation of evidence on thrombolysis in stroke services in England and Sweden. Semistructured interviews with 95 staff including doctors, nurses and managers working in stroke units, emergency medicine, radiology, the ambulance service, community rehabilitation services and commissioners.

RESULTS

The implementation of thrombolysis in acute stroke management benefited from a critical mass of the factors featured in the model including: the support of national and local opinion leaders; a strong evidence base and financial incentives. However, while the model provided a starting point as an organizational framework for mapping the critical factors influencing implementation, to understand properly the process of implementation and the importance of the different factors identified, more detailed analyses of context and, in particular, of the human and social dimensions of change was needed.

CONCLUSIONS

While recognising the usefulness of the model of diffusion of innovations in mapping the processes by which diffusion occurs, the use of methods that lend themselves to in-depth analysis, such as ethnography and the application of relevant bodies of social theory, are needed.

Implementing thrombolytic guidelines in stroke care: perceived facilitators and barriers

We performed a qualitative study to identify facilitators of and barriers to the implementation of national guidelines on thrombolytic therapy for acute ischemic stroke. We interviewed physicians and nurses at nine Swedish hospitals using 16 explorative, semistructured interviews, and selected hospitals based on their implementation rate of new stroke care methods according to data from the Swedish Stroke Register, Riks-Stroke. Through content analysis, we identified facilitators and barriers to implementation, which we classified into three categories: (a) individuals, (b) social interactions and context, and (c) organizational and resource issues. Insights obtained from this study can be used to identify target areas for improving the implementation of thrombolytic therapy and other new methods in stroke care.

Barriers to the utilization of thrombolysis for acute ischaemic stroke

WHAT IS KNOWN AND OBJECTIVE

Thrombolysis is currently the only evidence-based pharmacological treatment available for acute ischaemic stroke (AIS); however, its current utilization is suboptimal (administered to <3% of AIS patients). The aim of this article was to identify the potential barriers to the use of thrombolysis via a review of the available literature.

METHODS

Medline, Embase, International Pharmaceutical Abstracts and Google Scholar were searched to identify relevant original articles, review papers and other literature published in the period 1995-2011.

RESULTS AND DISCUSSION

Several barriers to the utilization of thrombolysis in stroke have been identified in the literature and can be broadly classified as 'preadmission' barriers and 'post-admission' barriers. Preadmission barriers include patient and paramedic-related factors leading to late patient presentation for treatment (i.e. outside the therapeutic time window for the administration of thrombolysis). Post-admission barriers include in-hospital factors, such as suboptimal triage of stroke patients and inefficient in-hospital acute stroke care systems, a lack of appropriate infrastructure and expertise to administer thrombolysis, physician uncertainty in prescribing thrombolysis and difficulty in obtaining informed consent for thrombolysis. Suggested strategies to overcome these barriers include public awareness campaigns, prehospital triage by paramedics, hospital bypass protocols and prenotification systems, urgent stroke-unit admission, on-call multidisciplinary acute stroke teams, urgent neuroimaging protocols, telestroke interventions and risk-assessment tools to aid physicians when considering thrombolysis. Additionally, greater pharmacists' engagement is warranted to help identify the people at risk of stroke and support preventative strategies, and provide the public with information regarding the recognition of stroke, as well as facilitate the access and use of thrombolysis.

WHAT IS NEW AND CONCLUSION

The most effective interventions appear to be those comprising several strategies and those that target more than one barrier simultaneously. Therefore, optimal utilization of thrombolysis requires a systematic, integrated multidisciplinary approach across the continuum of acute care.