Reducing onset-to-door times through the implementation of a prehospital large vessel occlusion bypass protocol: the Oahu experience

Q: What are the key findings of this study?

Implementation of an island-wide prehospital LVO bypass protocol significantly reduced onset-to-door times by 66 minutes, though it did not significantly improve 90-day functional outcomes.

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Acute Ischemic Stroke with Large Vessel Occlusion (n=351). Intervention: Prehospital LVO bypass protocol vs. Standard EMS transport to nearest hospital (pre-bypass era). Primary outcome: Onset-to-door time (66-min reduction, p=0.0046).

Q: What does this research mean for the field?

Implementation of a prehospital large vessel occlusion bypass protocol significantly reduces onset-to-door and onset-to-reperfusion times but does not significantly improve 90-day functional outcomes. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

Chung-Huan Johnny Sun; Ian K. H. Chun; Kazuma Nakagawa; Stacy Brown; Samuel Tsappidi; Ferdinand Hui; Rony Salem; Guangxiang Zhang; Daniel J. Galanis; Matthew A. Koenig

doi:10.3389/fstro.2026.1903852

September 3, 2026Frontiers in StrokeOpen Access

Reducing onset-to-door times through the implementation of a prehospital large vessel occlusion bypass protocol: the Oahu experience

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Key result

Prehospital LVO bypass cuts onset-to-door time by ~66 minutes without improving 90-day functional outcomes.

66-min reduction
P=0.0046
n=351

Why the study?

The impact of an island-wide prehospital large vessel occlusion bypass protocol on endovascular treatment times and patient outcomes was not well established.

Does the implementation of a prehospital large vessel occlusion bypass protocol reduce treatment times and improve 90-day clinical outcomes in patients with suspected LVO stroke?

Key Points

To evaluate the impact of an emergency medical services large vessel occlusion bypass protocol on endovascular treatment intervals and 90-day clinical outcomes.
Retrospective preimplementation-postimplementation study analyzing 351 patients (102 pre-bypass vs. 249 post-bypass) with confirmed anterior circulation large vessel occlusions treated within 8 hours between January 1, 2017, and January 1, 2023.
Evaluated primary time metrics using interrupted time series analysis and clinical functional outcomes via multivariate logistic regression modeling.
Interrupted time series analysis showed a sustained 66-min reduction in onset-to-door time (p = 0.0046) and a 41-min reduction in onset-to-reperfusion time (p = 0.08), alongside a 5-fold drop in interfacility transfers (55.9% to 11.6%; p < 0.001).
The post-bypass era did not independently associate with improved 90-day good outcomes (mRS 0–2: 40.2% vs. 44.6%; adjusted OR 0.98, 95% CI 0.57–1.69; p = 0.93) or a shift in disability (adjusted OR 0.93, 95% CI 0.60–1.41; p = 0.72).
Every 30-min delay in onset-to-reperfusion was independently associated with a 6% increase in the odds of worse 90-day functional disability (OR 1.062, 95% CI 1.001–1.125, p = 0.033).

Study Design

Type

Observational (n=351)

Blinding

Single-blind (outcome assessors)

Multicenter

No

Structured PICO

Does the implementation of a prehospital large vessel occlusion bypass protocol reduce treatment times and improve 90-day clinical outcomes in patients with suspected LVO stroke?

P

Population

351 patients with acute anterior circulation large vessel occlusion stroke managed by EMS within 8 hours of symptom onset, compared before and after the implementation of an island-wide prehospital bypass protocol.

I

Intervention

Implementation of an island-wide prehospital large vessel occlusion (LVO) bypass protocol, where patients with C-STAT scores ≥2 (suspected LVO) bypassed the nearest local hospital and were transported directly to the island's only Comprehensive Stroke Center (CSC) for evaluation and potential endovascular therapy.

C

Comparator

Pre-implementation standard EMS protocol, where patients were taken to the nearest hospital regardless of stroke severity, and interfacility transfers were coordinated if endovascular therapy was indicated.

O

Outcome

Treatment times including: 'onset-to-door' (stroke onset to arrival at the CSC), 'door-to-puncture' (arrival at the CSC to arterial puncture), and overall 'onset-to-reperfusion' (onset time to successful TICI2b reperfusion).

Main Result

Mean Difference: -66

Absolute Event Rate: 67% vs 149%

p-value: p=0.0046

Limitations

Findings may not be generalizable due to the closed geographic region with a single Comprehensive Stroke Center
Institutional changes over time in stroke recognition, patient selection, and thrombectomy volumes may have confounded results
Did not evaluate the protocol's impact on non-LVO stroke mimics or overall treatment eligibility
Unmeasured confounding from factors such as final infarct location and post-stroke rehabilitation
Results may not be generalizable due to the closed geographic region and single Comprehensive Stroke Center.
Temporal changes in institutional stroke recognition, patient selection, and imaging software adoption led to higher treatment volumes in the post-bypass era.
Study only evaluated patients treated with mechanical thrombectomy, missing the impact on treatment eligibility rates and false positive stroke mimics.
Did not capture other determinants of outcome like reperfusion injury, final infarct location, or post-stroke rehabilitation.
Included all patients evaluated by EMS, rather than restricting to true bypass cases, which may have diluted the clinical effect.

Implication

An EMS LVO bypass protocol successfully reduced onset-to-door times and interfacility transfers for stroke patients undergoing mechanical thrombectomy, but this did not translate into a statistically significant improvement in 90-day functional outcomes.

Abstract

Background The Oahu large vessel occlusion (LVO) bypass protocol is a real-world island-wide EMS initiative designed to identify patients with suspected LVOs in the field and triage them directly to a Comprehensive Stroke Center (CSC) for endovascular therapy (EVT). Methods A retrospective preimplementation-postimplementation study was conducted to investigate the impact of the bypass protocol on endovascular treatment times and patient outcomes between January 1, 2017 to January 1, 2023. Results A total of 351 patients met inclusion criteria (102 patients pre-bypass vs. 249 patients post-bypass). In an interrupted time series analysis, there was a sustained 66-min reduction in onset-to-CSC door time ( p = 0.0046), and a 41-min reduction in onset-to-reperfusion time ( p = 0.08) in the post-bypass period with no changes in temporal trends. Interfacility transfers for EVT declined 5-fold (55.9% to 11.6%; p < 0.001) with no delay in onset-to-thrombolytic time ( p = 0.13). In multivariate logistic regression modeling, longer onset-to-reperfusion times were independently associated with worse clinical outcomes, where every 30-min delay increased the odds of a higher 90-day mRS score by 6% (OR 1.062, 95% CI 1.001–1.125, p = 0.033). The post-bypass era, itself, however, was not associated with improved 90-day good outcomes (mRS 0–2: 40.2% vs. 44.6%; adjusted OR 0.98 [95% CI, 0.57–1.69]; p = 0.93) or a shift in 90-day mRS disability (adjusted OR 0.93 [0.60–1.41]; p = 0.72), though a nonsignificant trend toward improved 90-day excellent outcomes was observed (mRS 0–1: 23.5% vs. 34.5%; unadjusted OR 1.75 [1.01–2.90], p = 0.045; adjusted OR 1.51 [0.84–2.72], p = 0.17). Conclusions Implementation of a system-wide EMS LVO bypass protocol successfully reduced onset-to-door and onset-to-reperfusion times within a uniquely closed catchment geography. The impact on clinical outcomes, however, remains to be seen.

Discussion

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Cite This Study

Sun et al. (2026) conducted an observational in Acute Ischemic Stroke with Large Vessel Occlusion (n=351). Prehospital LVO bypass protocol vs. Standard EMS transport to nearest hospital (pre-bypass era) was evaluated on Onset-to-door time (66-min reduction, p=0.0046). Implementation of an island-wide prehospital LVO bypass protocol significantly reduced onset-to-door times by 66 minutes, though it did not significantly improve 90-day functional outcomes.

synapsesocial.com/papers/6ad0fcf615427f6a84040458 https://doi.org/10.3389/fstro.2026.1903852

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Reducing onset-to-door times through the implementation of a prehospital large vessel occlusion bypass protocol: the Oahu experience

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

Reducing onset-to-door times through the implementation of a prehospital large vessel occlusion bypass protocol: the Oahu experience

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

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