Optimal Transport Destination for Ischemic Stroke Patients With Unknown Vessel Status

Optimization of the stroke hospital selection strategy and the distribution of endovascular thrombectomy resources

Nowadays, emergency medical technicians (EMTs) decide to send a suspected stroke patient to a primary stroke center (PSC) or to an endovascular thrombectomy (EVT)-capable hospital, based on the Cincinnati Prehospital Stroke Scale (CPSS) and the number of symptoms a patient presents at the scene. Based on existing studies, the patient is likely to have a better functional outcome after three months if the time between the onset of symptoms and receiving EVT treatment is shorter. However, if an acute ischemic stroke (AIS) patient with large vessel occlusion (LVO) is first sent to a PSC, and then needs to be transferred to an EVT-capable hospital, the time to get definitive treatment is significantly increased. For this purpose, We formulate an integer programming model to minimize the expected time to receive a definitive treatment for stroke patients. We then use real-world data to verify the validity of the model. Also, we expand our model to find the optimal redistribution and centralization of EVT resources. It will enable therapeutic teams to increase their experience and skills more efficiently within a short period of time.

Geographical Requirements for the Applicability of the Results of the RACECAT Study to Other Stroke Networks

Background The RACECAT (Transfer to the Closest Local Stroke Center vs Direct Transfer to Endovascular Stroke Center of Acute Stroke Patients With Suspected Large Vessel Occlusion in the Catalan Territory) trial was the first randomized trial addressing the prehospital triage of acute stroke patients based on the distribution of thrombolysis centers and intervention centers in Catalonia, Spain. The study compared the drip-and-ship with the mothership paradigm in regions where a local thrombolysis center can be reached faster than the nearest intervention center (equipoise region). The present study aims to determine the population-based applicability of the results of the RACECAT study to 4 stroke networks with a different degree of clustering of the intervention centers (clustered, dispersed). Methods and Results Stroke networks were compared with regard to transport time saved for thrombolysis (under the drip-and-ship approach) and transport time saved for endovascular therapy (under the mothership approach). Population-based transport times were modeled with a local instance of an openrouteservice server using open data from OpenStreetMap.The fraction of the population in the equipoise region differed substantially between clustered networks (Catalonia, 63.4%; France North, 87.7%) and dispersed networks (Southwest Bavaria, 40.1%; Switzerland, 40.0%). Transport time savings for thrombolysis under the drip-and-ship approach were more marked in clustered networks (Catalonia, 29 minutes; France North, 27 minutes) than in dispersed networks (Southwest Bavaria and Switzerland, both 18 minutes). Conclusions Infrastructure differences between stroke networks may hamper the applicability of the results of the RACECAT study to other stroke networks with a different distribution of intervention centers. Stroke networks should assess the population densities and hospital type/distribution in the temporal domain before applying prehospital triage algorithms to their specific setting.

Cost-effectiveness of Direct Transfer to Angiography Suite of Patients With Suspected Large Vessel Occlusion

BACKGROUND AND OBJECTIVES

Patients with acute ischemic stroke due to large vessel occlusion (LVO) deemed eligible for endovascular thrombectomy (EVT) are transferred from the emergency room to the angiography suite to undergo the procedure. Recently, the strategy of direct transfer of patients with suspected LVO to the angiography suite (DTAS) has been shown to improve functional outcomes. This study aims to evaluate the cost-effectiveness of the DTAS strategy vs initial transfer of patients with suspected LVO (Rapid Arterial Occlusion Evaluation score >4 and NIH Stroke Scale >10) to the emergency room (ITER).

METHODS

A decision-analytic Markov model was developed to estimate the cost-effectiveness of the DTAS strategy vs the ITER strategy from a Dutch health care perspective with a 10-year time horizon. The primary outcome was the incremental cost-effectiveness ratio (ICER) using Dutch thresholds of $59,135 (€50,000) and $94,616 (€80,000) per quality-adjusted life year (QALY). Uncertainty of input parameters was assessed using 1-way sensitivity analysis, scenario analysis, and probabilistic sensitivity analysis.

RESULTS

The DTAS strategy yielded 0.65 additional QALYs at an additional $16,089, resulting in an ICER of $24,925/QALY compared with the ITER strategy. The ICER varied from $27,169 to $38,325/QALY across different scenarios. The probabilistic sensitivity analysis showed that the DTAS strategy had a 91.8% and 97.0% likelihood of being cost-effective at a decision threshold of $59,135/QALY and $94,616/QALY, respectively.

DISCUSSION

The cost-effectiveness of the DTAS strategy over ITER is robust for patients with suspected LVO. Together with recently published clinical results, this means that implementation of the DTAS strategy may be considered to improve the workflow and outcome of EVT.

Futility in Clinical Trials

This JAMA Guide to Statistics and Methods discusses the early stopping of clinical trials for futility due to lack of evidence supporting the desired benefit, evidence of harm, or practical issues that make successful completion unlikely.

Functional Outcome of Endovascular Treatment in Patients With Acute Ischemic Stroke With Large Vessel Occlusion: Mothership Versus Drip-and-Ship Model in a Portuguese Urban Region

Introduction Endovascular treatment (EVT) with mechanical thrombectomy and acute carotid stenting has become an integral part of the treatment of acute ischemic stroke with large vessel occlusion. Despite being included in the most recent stroke guidelines, only comprehensive centers can offer EVT and thus patients frequently need to be transferred from primary hospitals. We aimed to assess which pre-hospital model of care - direct admission to a comprehensive stroke center (mothership) or transfer to a comprehensive stroke center after the first admission to the nearest hospital (drip-and-ship) - had the most benefit in stroke patients in a Portuguese urban region. Methods We selected patients admitted to a comprehensive stroke center who underwent EVTs between January 2018 and December 2020, in Lisbon, Portugal. We used data from the Safe Implementation of Treatments in Stroke (SITS) International registry on stroke severity, previous modified Rankin Scale (mRS), time from symptom onset to the first admission, time from symptom onset to the procedure, and mRS three months post stroke. We defined an unfavorable outcome as having an mRS >2 at three months post stroke. For patients with previous mRS >2, an unfavorable outcome was defined as any increase in mRS at three months post stroke. Results We analyzed the data of 1154 patients, of which 407 were admitted through a mothership approach and 747 through a drip-and-ship approach. Both groups were similar regarding sociodemographic characteristics, stroke risk factors, previous disability, and stroke severity. Median onset-to-door time was higher (126 vs 110 minutes, p-value=0.002) but onset-to-procedure time was lower (199 vs 339 minutes, p-value<0.001) in the mothership group. The mothership group had a higher proportion of patients with mRS <3 at three months post stroke than the drip-and-ship group (41.3% vs 34.9%, p-value=0.035). Mortality was similar in both groups. A multivariate logistic regression model confirmed a lower probability of unfavorable outcomes with the mothership approach (OR = 0.677, 95% CI 0.514-0.892, p-value=0.006). Surprisingly, onset-to-procedure time did not have an impact on functional outcomes. Conclusion Our findings show that the mothership model results in better functional outcomes for patients with acute ischemic stroke with large vessel occlusion. Further studies are needed to better define patient selection for this strategy and the impact of a mothership model in comprehensive stroke centers.

Prehospital‐Stroke‐Scale Parameterized Hospital Selection Protocol for Suspected Stroke Patients Considering Door‐to‐Treatment Durations

Background

To mitigate uncertainty that may arise in the judgment of emergency medical technicians when relying on a prehospital stroke scale at the scene, we propose a hospital selection protocol that considers the uncertainty of a prehospital stroke scale and the actual door‐to‐treatment durations, and we have developed a web‐based system to be used with mobile devices.

Methods and Results

This hospital selection protocol incorporates real‐time, estimated transport time obtained from Google Maps, historical median door‐to‐treatment duration at hospitals that only provide the standard intravenous thrombolysis treatment, and at hospitals with endovascular thrombectomy for probable large‐vessel occlusion cases. We have validated the efficiency of the proposed protocol and compared it with other strategies used by emergency medical technicians when deciding on a receiving hospital. Using the proposed protocol for the triage reduces the time from onset to receiving definitive treatment by nearly 11 minutes. We found that the nearest endovascular thrombectomy–capable hospital from the scene may not be the most ideal if the door‐to‐treatment durations are discriminative. The results show that, when the tolerable bypass transport threshold and administration time are reduced to 9 minutes and 30.5 minutes, respectively, 228 patients out of 7678 cases, whose receiving hospitals were changed to endovascular thrombectomy–capable hospitals, received definitive treatment in a shorter time. The results of our analysis give recommendations for appropriate allowable bypass transport time for regional planning.

Conclusions

By applying almost‐real value parameters, we have validated a web‐based model, which can be universally adapted for optimal, time‐saving hospital selection for patients with stroke.

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.

The "Flying Intervention Team": A Novel Stroke Care Concept for Rural Areas

BACKGROUND

Endovascular treatment of large vessel occlusion in acute ischemic stroke patients is difficult to establish in remote areas, and time dependency of treatment effect increases the urge to develop health care concepts for this population.

SUMMARY

Current strategies include direct transportation of patients to a comprehensive stroke center (CSC) ("mothership model") or transportation to the nearest primary stroke center (PSC) and secondary transfer to the CSC ("drip-and-ship model"). Both have disadvantages. We propose the model "flying intervention team." Patients will be transported to the nearest PSC; if telemedically identified as eligible for thrombectomy, an intervention team will be acutely transported via helicopter to the PSC and endovascular treatment will be performed on site. Patients stay at the PSC for further stroke unit care. This model was implemented at a telestroke network in Germany. Fifteen remote hospitals participated in the project, covering 14,000 km2 and a population of 2 million. All have well established telemedically supported stroke units, an angiography suite, and a helicopter pad. Processes were defined individually for each hospital and training sessions were implemented for all stroke teams. An exclusive project helicopter was installed to be available from 8 a.m. to 10 p.m. during 26 weeks per year. Key Messages: The model of the flying intervention team is likely to reduce time delays since processes will be performed in parallel, rather than consecutively, and since it is quicker to move a medical team rather than a patient. This project is currently under evaluation (clinicaltrials NCT04270513).

Cost Effectiveness of Interhospital Transfer for Mechanical Thrombectomy of Acute Large Vessel Occlusion Stroke: Role of Predicted Recanalization Rates

BACKGROUND

Emergency interhospital transfer of patients with stroke with large vessel occlusion to a comprehensive stroke center for mechanical thrombectomy is resource-intensive and can be logistically challenging. Imaging markers may identify patients in whom intravenous thrombolysis (IVT) alone is likely to result in thrombus resolution, potentially rendering interhospital transfers unnecessary. Here, we investigate how predicted probabilities to achieve IVT-mediated recanalization affect cost-effectiveness estimates of interhospital transfer.

METHODS

We performed a health economic analysis comparing emergency interhospital transfer of patients with acute large vessel occlusion stroke after administration of IVT with a scenario in which patients also receive IVT but remain at the primary hospital. Results were stratified by clinical parameters, treatment delays, and the predicted probability to achieve IVT-mediated recanalization. Estimated 3-month outcomes were combined with a long-term probabilistic model to yield quality-adjusted life years (QALYs) and costs. Uncertainty was quantified in probabilistic sensitivity analyses.

RESULTS

Depending on input parameters, marginal costs of interhospital transfer ranged from USD -61 366 (cost saving) to USD +20 443 and additional QALYs gained from 0.1 to 3.0, yielding incremental cost-effectiveness ratios of <USD 0 (dominant) to USD 310 000 per QALY. For some elderly patients with moderate or severe stroke symptoms treated in a remote primary stroke center, transfer was unlikely to be cost effective at a willingness-to-pay threshold of USD 100 000 and 50 000 per QALY (20% and 1%, respectively) if the predicted probability to achieve IVT-related recanalization was high. On the other hand, in some younger patients, the analysis yielded incremental cost-effectiveness ratio estimates below USD 20 000 per QALY independent of the predicted recanalization rate.

CONCLUSIONS

Predicted probabilities to achieve IVT-mediated recanalization significantly affect the cost-effectiveness of interhospital transfer for MT, in particular in elderly patients with moderate or severe stroke symptoms. However, high predicted recanalization rates alone do not generally imply that patients should not be considered for transfer.

European Resuscitation Council Guidelines 2021: First aid

The European Resuscitation Council has produced these first aid guidelines, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics include the first aid management of emergency medicine and trauma. For medical emergencies the following content is covered: recovery position, optimal positioning for shock, bronchodilator administration for asthma, recognition of stroke, early aspirin for chest pain, second dose of adrenaline for anaphylaxis, management of hypoglycaemia, oral rehydration solutions for treating exertion-related dehydration, management of heat stroke by cooling, supplemental oxygen in acute stroke, and presyncope. For trauma related emergencies the following topics are covered: control of life-threatening bleeding, management of open chest wounds, cervical spine motion restriction and stabilisation, recognition of concussion, cooling of thermal burns, dental avulsion, compression wrap for closed extremity joint injuries, straightening an angulated fracture, and eye injury from chemical exposure.

Outcomes and Issues of 'Drip and Go' as an Inter-Hospital Cooperation System in Mechanical Thrombectomy for Acute Ischemic Stroke

Objective

Mechanical thrombectomy in acute ischemic stroke (AIS) has become popular in recent years. Our affiliated institutes without neuro-endovascular specialists call our department to come to assist and perform thrombectomy (Drip and Go). In this study, the effectiveness of this inter-hospital cooperative system was evaluated.

Methods

Between January 2016 and December 2018, "Drip and Go" was performed in a total of 29 patients (20 males, average age of 75 years) from four hospitals located within a 1-hour drive, that frequently called for AIS assistance. The background and outcomes of such cases were then retrospectively collected and evaluated.

Results

The median National Institutes of Health Stroke Scale (NIHSS) and diffusion-weighed image-Alberta Stroke Programme Early CT Score (DWI-ASPECTS) were 19 and 7, respectively. Gro in puncture was performed in 27 patients (93%) within 6 h of onset. Good reperfusion (thrombolysis in cerebral infarction [TICI] 2b/3) was obtained in 24 patients (82%) with only one patient exhibiting hemorrhagic complication. A total of 12 patients (41%) had a modified Rankin Scale (mRS) score of 0-3 after 90 days or at the time of discharge. Univariate analysis identified a DWI-ASPECTS of 7 or higher as the only significant factor associated with a good neurological prognosis (P <0.05). Neurological prognosis was the most favorable at the furthest hospital where patients had a good DWI-ASPECTS.

Conclusion

By employing a 1-hour arrival time window and proper patient selection, the "Drip and Go" inter-hospital cooperative system can be an alternative approach for covering areas where no neuro-endovascular specialists are available for AIS.

Routing to Endovascular Treatment of Ischemic Stroke in Korea: Recognition of Need for Process Improvement

BACKGROUND

To track triage, routing, and treatment status regarding access to endovascular treatment (EVT) after acute ischemic stroke (AIS) at a national level.

METHODS

From national stroke audit data, potential candidates for EVT arriving within 6 hours with National Institute of Health Stroke Scale score of ≥ 7 were identified. Acute care hospitals were classified as thrombectomy-capable hospitals (TCHs, ≥ 15 EVT cases/year) or primary stroke hospital (PSH, < 15 cases/year), and patients' initial routes and subsequent inter-hospital transfer were described. Impact of initial routing to TCHs vs. PSHs on EVT and clinical outcomes were analyzed using multilevel generalized mixed effect models.

RESULTS

Out of 14,902 AIS patients, 2,180 (14.6%) were EVT candidates. Eighty-one percent of EVT candidates were transported by ambulance, but only one-third were taken initially to TCHs. Initial routing to TCHs was associated with greater chances of receiving EVT compared to initial routing to PSHs (33.3% vs 12.1%, P < 0.001; adjusted odds ratio [aOR], 2.21; 95% confidence interval [CI], 1.59-2.92) and favorable outcome (38.5% vs. 28.2%, P < 0.001; aOR, 1.52; 95% CI, 1.16-2.00). Inter-hospital transfers to TCHs occurred in 17.4% of those initially routed to a PSH and was associated with the greater chance of EVT compared to remaining at PSHs (34.8% vs. 7.5%, P < 0.001), but not with better outcomes.

CONCLUSION

Two-thirds of EVT candidates were initially routed to PSHs despite greater chance of receiving EVT and having favorable outcomes if routed to a TCH in Korea. Process improvement is needed to direct appropriate patients to TCHs.

Prehospital Triage Strategies for the Transportation of Suspected Stroke Patients in the United States

Background and Purpose:

Ischemic stroke patients with large vessel occlusion (LVO) could benefit from direct transportation to an intervention center for endovascular treatment, but non-LVO patients need rapid IV thrombolysis in the nearest center. Our aim was to evaluate prehospital triage strategies for suspected stroke patients in the United States.

Methods:

We used a decision tree model and geographic information system to estimate outcome of suspected stroke patients transported by ambulance within 4.5 hours after symptom onset. We compared the following strategies: (1) Always to nearest center, (2) American Heart Association algorithm (ie, directly to intervention center if a prehospital stroke scale suggests LVO and total driving time from scene to intervention center is <30 minutes, provided that the delay would not exclude from thrombolysis), (3) modified algorithms with a maximum additional driving time to the intervention center of <30 minutes, <60 minutes, or without time limit, and (4) always to intervention center. Primary outcome was the annual number of good outcomes, defined as modified Rankin Scale score of 0–2. The preferred strategy was the one that resulted in the best outcomes with an incremental number needed to transport to intervention center (NNTI) <100 to prevent one death or severe disability (modified Rankin Scale score of >2).

Results:

Nationwide implementation of the American Heart Association algorithm increased the number of good outcomes by 594 (+1.0%) compared with transportation to the nearest center. The associated number of non-LVO patients transported to the intervention center was 16 714 (NNTI 28). The modified algorithms yielded an increase of 1013 (+1.8%) to 1369 (+2.4%) good outcomes, with a NNTI varying between 28 and 32. The algorithm without time limit was preferred in the majority of states (n=32 [65%]), followed by the algorithm with <60 minutes delay (n=10 [20%]). Tailoring policies at county-level slightly reduced the total number of transportations to the intervention center (NNTI 31).

Conclusions:

Prehospital triage strategies can greatly improve outcomes of the ischemic stroke population in the United States, but increase the number of non-LVO stroke patients transported to an intervention center. The current American Heart Association algorithm is suboptimal as a nationwide policy and should be modified to allow more delay when directly transporting LVO-suspected patients to an intervention center.

Clinical Outcomes of On-Site Versus Off-Site Endovascular Stroke Interventions

OBJECTIVES

The aim of this study was to assess whether offering local endovascular stroke therapy (EST) rather than transferring patients off-site to receive EST would improve outcomes.

BACKGROUND

There are limited data to determine whether offering EST on-site rather than transferring patients to receive EST off-site improves clinical outcomes.

METHODS

A large academic consortium database was queried to identify patients with acute ischemic stroke who received EST between October 2015 and September 2019. Primary endpoints were in-hospital mortality and poor functional outcomes. Secondary endpoints were major complications, length of stay, and cost. Baseline characteristics were adjusted for using propensity score matching and multivariate risk adjustment.

RESULTS

A total of 22,193 patients with acute ischemic stroke who underwent EST (50.8% on-site, 49.2% off-site) were included. Mean ages were 67.9 ± 15.5 years and 68.4 ± 15.5 years, respectively (p = 0.03). In the propensity score matching analysis, mortality and poor functional outcomes were higher in the off-site EST group (14.7% vs. 11.2% and 40.7% vs. 35.9%, respectively; p < 0.001). In the risk-adjusted analyses with different models, in-hospital mortality and poor functional outcomes remained significantly higher in the off-site EST group. In the most comprehensive model (adjusting for age, sex, demographics, risk factors, tissue plasminogen activator use, and institutional EST volume), in-hospital mortality and poor functional outcomes were significantly higher in the off-site EST group, with odds ratios of 1.38 (95% confidence interval: 1.26 to 1.51) and 1.26 (95% confidence interval: 1.18 to 1.34), respectively (p < 0.001). The incidence of intracranial hemorrhage and mechanical ventilation was higher in the off-site group, but cost was higher in the on-site group in both the propensity score matching and risk-adjusted analyses.

CONCLUSIONS

In contemporary U.S. practice, patients with acute ischemic stroke treated with EST on-site had lower in-hospital mortality and better functional outcomes compared with those transferred off-site for EST.

Impact of interhospital transfer on patients undergoing endovascular thrombectomy for acute ischaemic stroke in an Australian setting

Objective

To assess the impact of interhospital transfer on the interplay between functional outcome, mortality, reperfusion rates and workflow time metrics in patients undergoing endovascular thrombectomy (EVT) for acute ischaemic stroke due to large vessel occlusion (LVO) in the anterior cerebral circulation.

Design setting and participants

This is an analysis of a prospective database of consecutive patients undergoing EVT for LVO presenting between January 2017 and December 2018 at a single Australian comprehensive stroke centre (CSC). Patients presented directly or were transferred to the CSC from 21 sites across New South Wales and the Australian Capital Territory.

Main outcome measures

The main outcome measures were rate of good 90-day functional outcome (modified Rankin Scale 0-2), successful reperfusion (Thrombolysis in Cerebral Infarction scale grade 2b or 3), symptomatic intracerebral haemorrhage (sICH) and 90-day mortality. Key workflow time metric milestones were examined.

Results

154 of 213 (72%) patients were interhospital transfers. There was no significant difference in baseline characteristics including age, National Institutes of Health Stroke Scale score, intravenous thrombolysis administration or procedure time between transferred and direct presenters (all p>0.05). Transferred patients had worse 90-day functional outcome (39.6% vs 61.0%, OR 0.42, 95% CI 0.23 to 0.78), higher mortality (25.3% vs 6.8%, OR 4.66, CI 1.59 to 13.70) and longer stroke onset to treatment (groin puncture) time (298 min vs 205 min, p<0.01). Successful reperfusion rates and sICH were similar between the cohorts (96.8% vs 98.3%, and 7.8% vs 3.4%).

Conclusion

Interhospital transfer is associated with longer stroke onset to treatment, worse 90-day functional outcome and higher mortality compared with patients presenting directly to the CSC.

Safety of inter-hospital transfer of patients with acute ischemic stroke for evaluation of endovascular thrombectomy

Stroke networks facilitate access to endovascular treatment (EVT) for patients with ischemic stroke due to large vessel occlusion. In this study we aimed to determine the safety of inter-hospital transfer and included all patients with acute ischemic stroke who were transferred within our stroke network for evaluation of EVT between 06/2016 and 12/2018. Data were derived from our prospective EVT database and transfer protocols. We analyzed major complications and medical interventions associated with inter-hospital transfer. Among 615 transferred patients, 377 patients (61.3%) were transferred within our telestroke network and had transfer protocols available (median age 76 years [interquartile range, IQR 17], 190 [50.4%] male, median baseline NIHSS score 17 [IQR 8], 246 [65.3%] drip-and-ship i.v.-thrombolysis). No patient suffered from cardio-respiratory failure or required emergency intubation or cardiopulmonary resuscitation during the transfer. Among 343 patients who were not intubated prior departure, 35 patients (10.2%) required medical interventions during the transfer. The performance of medical interventions was associated with a lower EVT rate and higher mortality at three months. In conclusion, the transfer of acute stroke patients for evaluation of EVT was not associated with major complications and transfer-related medical interventions were required in a minority of patients.

Optimizing Stroke Care for Patients with Large Vessel Occlusions: Current State of the Art and Future Directions

Acute ischemic stroke (AIS) is a severely disabling disease. Endovascular therapy is a powerful and highly effective treatment option for these patients and has recently become standard of care. The benefits of endovascular treatment (EVT) are tremendous both from a patient and from an economic perspective, since it dramatically improves individual patient outcomes while reducing long-term healthcare costs at the same time. The effect of EVT is highly time-dependent. Thus, the overarching goal in AIS is to quickly transport and diagnose the patient to minimize treatment delays. In this review, we provide an overview about the current state of stroke care, propose a fast and simplified imaging protocol and management approach for AIS patients. We also highlight the challenges we are currently facing in endovascular stroke treatment and suggest possible solutions to overcome these.

Bypassing the Closest Stroke Center for Thrombectomy Candidates

Background and Purpose—

Patients with acute ischemic stroke who have large vessel occlusion benefit from direct transport to a comprehensive stroke center (CSC) capable of endovascular therapy. To avoid harm for patients without large vessel occlusion from delayed access to intravenous thrombolysis (IVT), it has been suggested to only redirect patients with high likelihood of large vessel occlusion for whom the additional delay to intravenous thrombolysis (IVT) caused by transport to the CSC is below a certain threshold. However, which threshold achieves the greatest clinical benefit is unknown.

Methods—

We used mathematical modeling to calculate additional-delay-to-IVT thresholds associated with the greatest reduction in disability-adjusted life years in abstracted 2-stroke center and multiple-stroke center scenarios. Model parameters were extracted from recent meta-analyses or large prospective cohort studies. Uncertainty was quantified in probabilistic and 2-way univariate sensitivity analyses.

Results—

Assuming ideal treatment time performance metrics, transport to the nearest CSC was the preferred strategy irrespective of additional delay-to-IVT when the transfer time between primary stroke center and CSC was <40 minutes (95% credible interval: 25–66 minutes); otherwise, the optimal additional delay-to-IVT-threshold ranged from 28 to 139 minutes. In multiple-stroke center scenarios, optimal additional-delay-to-IVT thresholds were 30 to 54 minutes in urban and 49 to 141 minutes in rural settings; use of optimal thresholds as compared with a 15 minute-threshold saved 0 to 0.11 and 0 to 0.37 disability-adjusted life years per triage case, respectively. Assuming slower treatment times at primary stroke centers and CSCs yielded longer permissible additional delays.

Conclusions—

Our results suggest that patients with acute ischemic stroke with suspected large vessel occlusion should be redirected to a CSC if the additional delay to IVT is <30 minutes in urban and 50 minutes in rural settings.

Effect of Interhospital Transfer on Endovascular Treatment for Acute Ischemic Stroke

Background and Purpose- To assess the effect of inter-hospital transfer on time to treatment and functional outcome after endovascular treatment (EVT) for acute ischemic stroke, we compared patients transferred from a primary stroke center to patients directly admitted to an intervention center in a large nationwide registry. Methods- MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) Registry is an ongoing, prospective, observational study in all centers that perform EVT in the Netherlands. We included adult patients with an acute anterior circulation stroke who received EVT between March 2014 to June 2016. Primary outcome was time from arrival at the first hospital to arterial groin puncture. Secondary outcomes included the 90-day modified Rankin Scale score and functional independence (modified Rankin Scale score of 0-2). Results- In total 821/1526 patients, (54%) were transferred from a primary stroke center. Transferred patients less often had prestroke disability (227/800 [28%] versus 255/699 [36%]; P=0.02) and more often received intravenous thrombolytics (659/819 [81%] versus 511/704 [73%]; P<0.01). Time from first presentation to groin puncture was longer for transferred patients (164 versus 104 minutes; P<0.01, adjusted delay 57 minutes [95% CI, 51-62]). Transferred patients had worse functional outcome (adjusted common OR, 0.75 [95% CI, 0.62-0.90]) and less often achieved functional independence (244/720 [34%] versus 289/681 [42%], absolute risk difference -8.5% [95% CI, -8.7 to -8.3]). Conclusions- Interhospital transfer of patients with acute ischemic stroke is associated with delay of EVT and worse outcomes in routine clinical practice, even in a country where between-center distances are short. Direct transportation of patients potentially eligible for EVT to an intervention center may improve functional outcome.

Modeling the Optimal Transportation for Acute Stroke Treatment: The Impact of the Drip-and-Drive Paradigm

Background and Purpose- Health systems are faced with the challenge of ensuring fast access to appropriate therapy for patients with acute stroke. The paradigms primarily discussed are mothership and drip and ship. Less attention has been focused on the drip-and-drive (DD) paradigm. Our aim was to analyze whether and under what conditions DD would predict the greatest probability of good outcome for patients with suspected ischemic stroke in Northwestern Germany. Methods- Conditional probability models based on the decay curves for endovascular therapy and intravenous thrombolysis were created to determine the best transport paradigm, and results were displayed using map visualizations. Our study area consisted of the federal states of Lower Saxony, Hamburg, and Schleswig-Holstein in Northwestern Germany covering an area of 64 065 km² with a population of 12 703 561 in 2017 (198 persons per km²). In several scenarios, the catchment area, that is, the region that would result in the greatest probability of good outcomes, was calculated for each of the mothership, drip-and-ship, and the DD paradigms. Several different treatment time parameters were varied including onset-to-first-medical-response time, ambulance-on-scene time, door-to-needle time at primary stroke center, needle-to-door time, door-to-needle time at comprehensive stroke center, door-to-groin-puncture time, needle-to-interventionalist-leave time, and interventionalist-arrival-to-groin-puncture time. Results- The mothership paradigm had the largest catchment area; however, the DD catchment area was larger than the drip-and-ship catchment area so long as the needle-to-interventionalist-leave time and the interventionalist-arrival-to-groin-puncture time remain <40 minutes each. A slowed workflow in the DD paradigm resulted in a decrease of the DD catchment area to 1221 km² (2%). Conclusions- Our study suggests the largest catchment area for the mothership paradigm and a larger catchment area of DD paradigm compared with the drip-and-ship paradigm in Northwestern Germany in most scenarios. The existence of different paradigms allows the spread of capacities, shares the cost and hospital income, and gives primary stroke centers the possibility to provide endovascular therapy services 24/7.

Personalized Prehospital Triage in Acute Ischemic Stroke

Supplemental Digital Content is available in the text.

Background and Purpose—

Direct transportation to a center with facilities for endovascular treatment might be beneficial for patients with acute ischemic stroke, but it can also cause harm by delay of intravenous treatment. Our aim was to determine the optimal prehospital transportation strategy for individual patients and to assess which factors influence this decision.

Methods—

We constructed a decision tree model to compare outcome of ischemic stroke patients after transportation to a primary stroke center versus a more distant intervention center. The optimal strategy was estimated based on individual patient characteristics, geographic location, and workflow times. In the base case scenario, the primary stroke center was located at 20 minutes and the intervention center at 45 minutes. Additional sensitivity analyses included an urban scenario (10 versus 20 minutes) and a rural scenario (30 versus 90 minutes).

Results—

Direct transportation to the intervention center led to better outcomes in the base case scenario when the likelihood of a large vessel occlusion as a cause of the ischemic stroke was >33%. With a high likelihood of large vessel occlusion (66%, comparable with a Rapid Arterial Occlusion Evaluation score of 5 or above), the benefit of direct transportation to the intervention center was 0.10 quality-adjusted life years (=36 days in full health). In the urban scenario, direct transportation to an intervention center was beneficial when the risk of large vessel occlusion was 24% or higher. In the rural scenario, this threshold was 49%. Other factors influencing the decision included door-to-needle times, door-to-groin times, and the door-in-door-out time.

Conclusions—

The preferred prehospital transportation strategy for suspected stroke patients depends mainly on the likelihood of large vessel occlusion, driving times, and in-hospital workflow times. We constructed a robust model that combines these characteristics and can be used to personalize prehospital triage, especially in more remote areas.

Optimization of Prehospital Triage of Patients With Suspected Ischemic Stroke

Background and Purpose- Prehospital routing algorithms for patients with suspected stroke because of large vessel occlusions should account for likelihood of benefit from endovascular therapy (EVT), risk of alteplase delays, and transport times. We built a mathematical model to give a real-time, location-based optimal emergency medical service routing location based on local resources, transport times, and patient characteristics. Methods- Using location, onset time, age, sex, and prehospital stroke severity, we calculated odds of a favorable outcome for a patient with suspected large vessel occlusions under 2 scenarios: direct to EVT-capable hospital versus transport to the nearest alteplase-capable hospital with transfer to EVT-capable hospital if appropriate. We project lifetime outcomes incorporating disability, quality of life utility, and cost. Multiple parameter sets of center-specific times (eg, door to alteplase) were randomly selected within a clinically plausible range to account for the model sensitivity to these estimates; for each iteration, the optimal strategy was defined as the most cost-effective outcome (threshold, $100 000 per quality-adjusted life-years gained). After 1000 simulations, the most frequently occurring optimal strategy was the final recommendation, with its strength measured as the proportion of runs for which it was optimal. Results- Routing recommendations were highly sensitive to small changes in model input parameters. Under many scenarios, the recommendations for direct transfer to the EVT site increased with increasing stroke severity and geographic proximity but did not vary substantially with respect to sex, age, or onset time. Conclusions- We present a mathematical decision model that determines ideal prehospital routing recommendations for patients with suspected stroke because of large vessel occlusions, with consideration of patient characteristics and location at onset. This model may be further refined by incorporating real-time data on traffic patterns and actual EVT and alteplase timeliness performance. Further studies are needed to verify model predictions.

Cincinnati Prehospital Stroke Scale for EMS Redirection of Large Vessel Occlusion Stroke

Introduction:

Prehospital identification of large vessel occlusion (LVO) stroke may expedite treatment by direct transport to comprehensive stroke centers (CSCs) with endovascular capabilities. The Cincinnati Prehospital Stroke Scale (CPSS) is commonly used for prehospital stroke detection. We aimed to assess whether (1) a high CPSS score can identify LVO and (2) an Emergency Medical Service (EMS) redirection protocol based on high CPSS accelerated endovascular treatment (EVT).

Methods:

A retrospective comparison of patients transported by EMSs for suspected stroke to a high-volume CSC over a 16-month period, before and after implementation of an EMS redirection protocol based on high CPSS score (3/3). Charts were reviewed to determine the presence of LVO. Time to EVT and 3-month outcomes were compared before and after implementation.

Results:

A prehospital CPSS 3/3 score was found in 223 (59%) patients, demonstrating positive and negative predictive values for LVO of 29% and 94%, respectively. CPSS-based EMS redirection increased the proportion of EVT performed after direct transport to CSC [before: 21 (36%), after: 45 (63%), p < 0.01] and decreased median first door-to-groin puncture time by 28 minutes [109 (interquartile range (IQR) 64–116) versus 81 (IQR 56–130), p = 0.03]. At 3 months, the proportion of patients achieving functional independence (modified Rankin score 0–2) went from 20/57 (35%) to 29/68 (43%) (p = 0.39) following implementation.

Conclusions:

CPSS-based EMS redirection accelerated identification of LVO strokes in the out-of-hospital setting and decreased time to EVT. Nevertheless, this protocol was also associated with high rates of non-LVO stroke. Impact on clinical outcomes should be evaluated in a larger cohort.

Comparative Evaluation of 10 Prehospital Triage Strategy Paradigms for Patients With Suspected Acute Ischemic Stroke

Background

The best strategy to identify patients with suspected acute ischemic stroke and unknown vessel status (large vessel occlusion) for direct transport to a comprehensive stroke center instead of a nearer primary stroke center is unknown.

Methods and Results

We used mathematical modeling to estimate the impact of 10 increasingly complex prehospital triage strategy paradigms on the reduction of population‐wide stroke‐related disability. The model was applied to suspected acute ischemic stroke patients in (1) abstract geographies, and (2) 3 real‐world urban and rural geographies in Germany. Transport times were estimated based on stroke center location and road infrastructure; spatial distribution of emergency medical services calls was derived from census data with high spatial granularity. Parameter uncertainty was quantified in sensitivity analyses. The mothership strategy was associated with a statistically significant population‐wide gain of 8 to 18 disability‐adjusted life years in the 3 real‐world geographies and in most simulated abstract geographies (net gain −4 to 66 disability‐adjusted life years). Of the more complex paradigms, transportation of patients with clinically suspected large vessel occlusion based on a dichotomous large vessel occlusion detection scale to the nearest comprehensive stroke center yielded an additional clinical benefit of up to 12 disability‐adjusted life years in some rural but not in urban geographies. Triage strategy paradigms based on probabilistic conditional modeling added an additional benefit of 0 to 4 disability‐adjusted life years over less complex strategies if based on variable cutoff scores.

Conclusions

Variable stroke severity cutoff scores were associated with the highest reduction in stroke‐related disability. The mothership strategy yielded better clinical outcome than the drip‐‘n'‐ship strategy in most geographies.

Availability of Hospital Resources and Specialty Services for Stroke Care in North Carolina

OBJECTIVES

Effective regionalization of acute stroke care requires assessment and coordination of limited hospital resources. We described the availability of stroke-specific hospital resources (neurology specialty physicians and neuro-intensive care unit [neuro-ICU] bed capacity) for North Carolina overall and by region and population density. We also assessed daily trends in hospital bed availability.

METHODS

This statewide descriptive study was conducted with data from the State Medical Asset Resource Tracking Tool (SMARTT), a Web-based system used by North Carolina to track available medical resources within the state. The SMARTT system was queried for stroke-specific physician and bed resources at each North Carolina hospital during a 1-year period (June 2015-May 2016), including daily availability of neuro-ICU beds. We compared hospital resources by geographic region and population density (metropolitan, urban, and rural).

RESULTS

Data from 108 acute care hospitals located in 75 of 100 counties in North Carolina were included in the analysis. Fifty-seven percent of hospitals had no neurology specialty physicians. Western and eastern North Carolina had the lowest prevalence of these physicians. Most hospitals (88%) had general ICUs, whereas only 17 hospitals (16%) had neuro-ICUs. Neuro-ICUs were concentrated in metropolitan areas and in central North Carolina. On average, there were 276 general ICU and 27 neuro-ICU beds available statewide each day. Daily neuro-ICU bed availability was lowest in eastern and southeastern regions and during the week compared with weekends.

CONCLUSIONS

In North Carolina, stroke-specific hospital subspecialists and resources are not distributed evenly across the state. Daily bed availability, particularly in neuro-ICUs, is lacking in rural areas and noncentral regions and appears to decrease on weekdays. Regionalization of stroke care needs to consider the geographic distribution and daily variability of hospital resources.

Pre-hospital Triage of Acute Ischemic Stroke Patients-Importance of Considering More Than Two Transport Options

Background: Patients with acute ischemic stroke (AIS) and large vessel occlusion benefit from rapid access to mechanical thrombectomy in addition to intravenous thrombolysis. Prehospital triage algorithms to determine the optimal transport destination for AIS patients with unknown vessel status have so far only considered two alternatives: the nearest comprehensive (CSC) and the nearest primary stroke center (PSC). Objective: This study explores the importance of considering a larger number of PSCs during pre-hospital triage of AIS patients. Methods: Analysis was performed in random two-dimensional abstract geographic stroke care infrastructure environments and two models based on real-world geographic scenarios. Transport times to CSCs and PSCs were calculated to define sub-regions with specific triage properties. Possible transport destinations included the nearest CSC, the nearest PSC, and any of the remaining PSCs that are not closest to the scene, but transport to which would imply a shorter total time-to-CSC-via-PSC. Results: In abstract geographic environments, the median relative size of the sub-region where a triage decision is required ranged from 34 to 92%. The median relative size of the sub-region where more than two triage options need to be considered ranged from 0 to 56%. The achievable reduction in time-to-thrombectomy ("benefit") exceeded the increase in time-to-thrombolysis ("harm") by a factor of 2 in 30.5-37.0% of the sub-region where more than two triage options need to be considered. Results were confirmed in geographic environments based on real-world urban and rural stroke care infrastructures. Conclusion: Pre-hospital triage algorithms for AIS patients that only take into account the nearest CSC and the nearest PSC as transport destinations may be unable to identify the optimal transport destination for a significant proportion of patients.

Efficacy of ‘drive and retrieve’ as a cooperative method for prompt endovascular treatment for acute ischemic stroke

Background

Outcomes of endovascular treatment for acute ischemic stroke depend on the time interval from onset to reperfusion. Although the centralized ‘mothership’ method is considered preferable, the required transportation time increases the risk that a patient with a stroke may not receive intravenous or endovascular therapy. In contrast, ‘drive and retrieve’ describes a system wherein doctors from comprehensive stroke centers travel to primary stroke centers and provide endovascular treatment for acute ischemic stroke.

Objective

To describe the drive and retrieve system and verify the effects of this new collaboration on outcomes in patients with acute ischemic stroke among facilities.

Methods

This non-randomized, single-arm study retrospectively analyzed patients who met the inclusion criteria for endovascular treatment provided through a drive and retrieve system. Among the 122 patients treated by this system, we analyzed the time of onset to recanalization as the primary outcome. We also analyzed the efficacy of the drive and retrieve system using geographic information system analysis.

Results

The median time from onset to recanalization was 229 min (IQR 170–307 min, 95% CI 201 to 252 min). The upper limit of the 95% CI for the time from onset to recanalization was shorter than the median times reported in two previous trials. Geographic information system analysis revealed an upward trend in the population coverage rate in each secondary medical area after the drive and retrieve method was introduced.

Conclusion

The drive and retrieve method may be an effective form of cooperation between facilities located within 1 hour of a comprehensive stroke center.

Effect of routing paradigm on patient centered outcomes in acute ischemic stroke

Background

To compare performance of routing paradigms for patients with acute ischemic stroke using clinical outcomes.

Methods

We simulated different routing paradigms in a system comprising one primary stroke center (PSC) and one comprehensive stroke center (CSC), separated by distances representative of urban, suburban, and rural environments. In the nearest center paradigm, patients are initially sent to the nearest center, while in CSC first, patients are sent to the CSC. In the Rhode Island and distributive paradigms, patients with a FAST-ED (Facial palsy, Arm weakness, Speech changes, Time, Eye deviation, and Denial/neglect) score ≥4 are sent to the CSC, while others are sent to the nearest center or PSC, respectively. Performance and efficiency were compared using rates of good clinical outcome, determined by type and timing of treatment using clinical trial data, and number needed to bypass (NNB).

Results

Good clinical outcome was achieved in 43.76% of patients in nearest center, 44.48% in CSC first, and 44.44% in Rhode Island and distributive in an urban setting; 43.38% in nearest center, 44.19% in CSC first, and 44.17% in Rhode Island in a suburban setting; and 41.10% in nearest center, 43.20% in CSC first, and 42.73% in Rhode Island in a rural setting. In all settings, NNB was generally higher for CSC first compared with Rhode Island or distributive.

Conclusion

Routing paradigms that allow bypass of nearer hospitals for thrombectomy capable centers improve population level patient outcomes. Differences are more pronounced with increasing distance between hospitals; therefore, paradigm choice may be most impactful in rural settings. Selective bypass, as implemented in the Rhode Island and distributive paradigms, improves system efficiency with minimal impact on outcomes.

A review of acute ischemic stroke triage protocol evidence: a context for discussion

Endovascular thrombectomy (EVT) is now the standard of care for eligible patients with acute ischemic stroke (AIS) secondary to emergent large vessel occlusion (ELVO). However, there remains uncertainty in how hospital systems can most efficiently route patients with suspected ELVO for EVT treatment. Given the relative geographic distribution of centers with and without endovascular capabilities, the value of prehospital triage directly to centers with the ability to provide EVT remains debated. While there are no randomized trial data available to date, there is substantial evidence in the literature that may offer guidance on the subject. In this review we examine the available data in the context of improving the existing AIS triage systems and discuss how prehospital triage directly to endovascular-capable centers may confer clinical benefits for patients with suspected ELVO.

Effect of routing paradigm on patient-centered outcomes in acute ischemic stroke

OBJECTIVE

To compare performance of routing paradigms for patients with acute ischemic stroke using clinical outcomes.

METHODS

We simulated different routing paradigms in a system comprising one primary stroke center (PSC) and onecomprehensive stroke center (CSC), separated by distances representative of urban, suburban, and rural environments. In the Nearest Center paradigm, patients are initially sent to the nearest center, while in CSC First, patients are sent to the CSC. In Rhode Island and Distributive paradigms, patients with Field Assessment Stroke Triage for Emergency Destination (FAST-ED) score ≥4 are sent to the CSC, while others are sent to the nearest center or PSC, respectively. Performance and efficiency were compared using rates of good clinical outcome determined by type and timing of treatment using clinical trial data and number needed to bypass (NNB).

RESULTS

Good clinical outcome was achieved in 43.67% of patients in Nearest Center and 44.62% in CSC First, Rhode Island, and Distributive in an urban setting; 42.79% in Nearest Center and 43.97% in CSC First and Rhode Island in a suburban setting; and 39.76% in Nearest Center, 41.73% in CSC First, and 41.59% in Rhode Island in a rural setting. In all settings, the NNB was considerably higher for CSC First than for Rhode Island or Distributive.

CONCLUSION

Routing paradigms that allow bypass of nearer hospitals for thrombectomy-capable centers improve population-level patient outcomes. Differences are more pronounced with increasing distance between hospitals; therefore, the choice of model may have greater effect in rural settings. Selective bypass, as implemented in Rhode Island and Distributive paradigms, improves system efficiency with minimal effect on outcomes.

Evolution of a US County System for Acute Comprehensive Stroke Care

BACKGROUND AND PURPOSE

In Orange County, California, patients with suspected acute stroke are taken to stroke neurology receiving centers that are designated by County Emergency Medical Services authorities as either hubs or spokes based on endovascular treatment capability. We examined relationships between stroke details, reperfusion therapies, hospital transfers, and their change over time.

METHODS

All patients from January 1, 2013, to December 31, 2015, for whom 911 was called within 7 hours of onset in whom Emergency Medical Services personnel suspected acute stroke were evaluated.

RESULTS

Among 6132 patients, 3924 (64%) had confirmed diagnosis of stroke (74% ischemic/26% hemorrhagic), yielding diagnostic precision of 64% in the field. Of the 2892 patients with acute ischemic stroke, acute reperfusion therapy was given to 29.2% (21.7% intravenous tPA [tissue-type plasminogen activator] only and 7.5% endovascular treatment). Rates of endovascular treatment of patients with ischemic stroke increased over time, more than doubling from 5.6% in 2013 to 12.5% (odds ratio per 3-month quarter=1.09; 95% confidence interval, 1.04-1.14; P<0.0001). Only 3.4% of patients with acute ischemic stroke were transferred from a spoke to a hub hospital; transfer rates were inversely related to age (P<0.0001), and reperfusion therapy rates did not vary according to transfer status.

CONCLUSIONS

Favorable features of this acute stroke care system include reperfusion therapy in 29.2% of patients with ischemic stroke and substantial increases in endovascular treatment rates over time. Continued efforts to optimize acute stroke systems of care can be directed toward improving access to best acute stroke therapies.

Diagnosis and Management of Acute Ischemic Stroke

Acute ischemic stroke (AIS) is among the leading causes of death and long-term disability. Intravenous tissue plasminogen activator has been the mainstay of acute therapy. Recently, several prospective randomized trials documented the value of endovascular revascularization in selected patients with large-vessel occlusion within the anterior circulation. This finding has led to a paradigm shift in the management of AIS, including wide adoption of noninvasive neuroimaging to assess vessel patency and tissue viability, with the supplemental and independent use of intravenous tissue plasminogen activator to improve clinical outcomes. In this article, we review the landmark studies on management of AIS and the current position on the diagnosis and management of AIS. The review also highlights the importance of early stabilization and prompt initiation of therapeutic interventions before, during, and after the diagnosis of AIS within and outside of the hospital.

Clinical benefit of improved Prehospital stroke scales to detect stroke patients with large vessel occlusions: results from a conditional probabilistic model

Background

Clinical scales to detect large vessel occlusion (LVO) may help to determine the optimal transport destination for patients with suspected acute ischemic stroke (AIS). The clinical benefit associated with improved diagnostic accuracy of these scales has not been quantified.

Methods

We used a previously reported conditional model to estimate the probability of good outcome (modified Rankin scale sore ≤2) for patients with AIS and unknown vessel status occurring in regions with greater proximity to a primary than to a comprehensive stroke center. Optimal rapid arterial occlusion evaluation (RACE) scale cutoff scores were calculated based on time-dependent effect-size estimates from recent randomized controlled trials. Probabilities of good outcome were compared between a triage strategy based on these cutoffs and a strategy based on a hypothetical perfect LVO detection tool with 100% diagnostic accuracy.

Results

In our model, the additional benefit of a perfect LVO detection tool as compared to optimal transport-time dependent RACE cutoff scores ranges from 0 to 5%. It is largest for patients with medium stroke symptom severity (RACE score 5) and in geographic environments with longer transfer time between the primary and comprehensive stroke center.

Conclusion

Based on a probabilistic conditional model, the results of our simulation indicate that more accurate prehospital clinical LVO detections scales may be associated with only modest improvements in the expected probability of good outcome for patients with suspected acute ischemic stroke and unknown vessel status.

Electronic supplementary material

The online version of this article (10.1186/s12883-018-1021-8) contains supplementary material, which is available to authorized users.

Impact of Prehospital Triage Scales to Detect Large Vessel Occlusion on Resource Utilization and Time to Treatment

BACKGROUND AND PURPOSE

Prehospital stroke severity scales may help to triage acute ischemic stroke patients with large vessel occlusion (LVO) for direct transportation to a comprehensive stroke center. The impact on resource use and time to reperfusion treatment for patients with and without LVO is unknown.

METHODS

Based on empirical distributions of stroke symptom severity, prehospital delay times, and stroke symptom severity-dependent likelihood of LVO, we simulate prehospital incidents of stroke-like symptoms in abstract geographical environments to estimate the impact of prehospital triage strategies based on different cutoffs of the rapid arterial occlusion evaluation scale.

RESULTS

Compared with transporting each patient to the nearest stroke center, implementation of a prehospital triage strategy based on a rapid arterial occlusion evaluation scale cutoff score ≥5 is associated with more patients with suspected acute stroke at comprehensive stroke centers and less patients at primary stroke centers (+11.7% [95% confidence interval: +8.1% to +15.3%] and -18.4% [-19.1% to -17.7%], respectively). Mean time to groin puncture is reduced by 29.6 minutes (-35.2 to -24.7 minutes) while mean time to thrombolysis does not change significantly (±0.0 minutes [-0.3 to +0.3 minutes]). The total number of secondary transfers is reduced by 60.9% (-62.8% to -59.0%); mean time of ambulance use per patient is unchanged. Results are robust with regards to variation in model parameters.

CONCLUSIONS

Implementation of prehospital triage based on stroke severity scales would have strong impact on patient flow and distribution. The benefit of earlier thrombectomy for patients with LVO may outweigh the harm associated with delayed access to thrombolysis for some patients without LVO. Randomized trials using clinical stroke severity scales as a triage tool are needed to confirm our findings.

[Prehospital care for stroke patients]

The effectiveness of thrombolysis or mechanical recanalization for acute stroke is higher, the sooner these therapies are started. Therefore, acute stroke patients need to be evaluated by qualified staff for these therapies as soon as possible. Lay persons need to identify the typical symptoms of stroke as an emergency and act accordingly by calling the emergency medical system (EMS). The EMS team reassesses the symptoms and prompts cerebral imaging. Cerebral imaging is performed ideally in hospitals with a stroke unit where subsequent (stroke) treatments occur. On the way, the emergency team will measure and stabilize vital functions and obtain further important clinical information. Telemedicine allows communicating exact time of onset and severity of symptoms, as well as comorbidities and medication of the patient to the respective hospital. Thereby, the intrahospital workload will be disencumbered and accelerated. Some EMS vehicles now carry point-of-care laboratories and may measure lab values en route (glucose and INR [International Normalized Ratio] for example). Some ambulances are not only equipped with qualified staff, telemedicine technique, and point-of-care labs but even computer tomography (CT) to perform imaging. Such mobile stroke emergency mobiles (STEMO) or mobile stroke units may perform thrombolysis prehospitally. Prehospital thrombolysis has been proven to be initiated faster and is safe. Preliminary results even suggest superiority to intrahospital thrombolysis with respect to clinical outcome. Moreover, STEMO may perform CT-angiography and assess intracranial large-vessel status. If intracranial large-vessel occlusion is present, patients will be brought directly to hospitals able to perform mechanical recanalization. Thus, secondary transports are no longer required.