Title: Chris Price - Optimising pre-hospital assessment for acute stroke due to large artery occlusion.
Funder: Stroke Association

Abstract: SCIENTIFIC: Mechanical thrombectomy (MT) improves outcomes for large artery occlusion stroke (LAOS) but must be performed rapidly on highly selected patients. Pre-hospital identification of LAOS could facilitate treatment via pre-notification and/or patient re-direction to regional MT providers. Paramedics do not specifically identify LAOS. Published symptom checklists lack specificity/sensitivity and have significant service/training implications. Whole blood purine concentration (WBPC) is a promising new point of care biomarker for ischaemic brain tissue volume. “Mobile stroke units” are not cost-effective but ambulance telemedicine is evolving. This programme seeks to develop and evaluate a pre-hospital pathway containing an optimal combination of symptom checklist and/or WBPC assay +/- ambulance telemedicine to identify and respond to LAOS. Objectives are to conduct: 1. A systematic review of LAOS identification checklists. 2. A narrative review describing ambulance telemedicine feasibility. 3. A hospital-based diagnostic accuracy study to confirm whether a WBPC assay in addition to clinical characteristics improves early identification of patients i) requiring radiological screening and ii) a subset with proven LAOS. 4. Construction of pre-hospital models for i) and ii). 5. Stakeholder interviews about the content and implications of a pre-hospital LAOS pathway. 6. A feasibility evaluation of the pathway. 7. A pragmatic clinical trial of the pathway. LAY TITLE: A new paramedic assessment to speed up treatment of stroke due to a blocked large artery. LAY: Approximately 80% of stroke is caused by a blocked blood vessel. One third of these patients have blockage of a large vessel in the neck or brain known as large artery occlusion stroke (LAOS). This often causes severe problems, but chances of recovery are greater if the blockage is removed quickly. It has recently been shown that pulling the blockage out of the artery (mechanical thrombectomy) within 6 hours of the symptoms starting is more effective than a clot-dissolving injection by itself (intravenous thrombolysis). However there are few hospitals providing thrombectomy, and most patients with a large artery blockage will need to be identified first at local stroke units and then taken to regional centres. An initial scan of the brain’s arteries (CT angiogaphy) and an additional ambulance journey is required. This often creates a delay of one hour before the patient arrives at the thrombectomy hospital, and chances of a good recovery will be lower than if they had been taken there directly. But as only 10% of stroke patients overall are suitable for thrombectomy, it would be inefficient for all to be taken directly to the regional hospital first. This programme will develop and test a new care pathway for paramedics to recognise those patients who are likely to have a large artery blockage, so that this group can be taken directly to the thrombectomy hospital. The assessment will reflect a combination of the best published evidence about symptom checklists to identify patients; a new fingerprick blood test for measuring natural chemicals (purines) which increase when body tissues are starved of oxygen, as higher levels may reflect blockage of a larger artery; the use of telephone or video in the ambulance to enable a hospital stroke specialist to review the patient; and stakeholder views about feasibility and acceptability.

Lay abstract: SCIENTIFIC: Mechanical thrombectomy (MT) improves outcomes for large artery occlusion stroke (LAOS) but must be performed rapidly on highly selected patients. Pre-hospital identification of LAOS could facilitate treatment via pre-notification and/or patient re-direction to regional MT providers. Paramedics do not specifically identify LAOS. Published symptom checklists lack specificity/sensitivity and have significant service/training implications. Whole blood purine concentration (WBPC) is a promising new point of care biomarker for ischaemic brain tissue volume. “Mobile stroke units” are not cost-effective but ambulance telemedicine is evolving. This programme seeks to develop and evaluate a pre-hospital pathway containing an optimal combination of symptom checklist and/or WBPC assay +/- ambulance telemedicine to identify and respond to LAOS. Objectives are to conduct: 1. A systematic review of LAOS identification checklists. 2. A narrative review describing ambulance telemedicine feasibility. 3. A hospital-based diagnostic accuracy study to confirm whether a WBPC assay in addition to clinical characteristics improves early identification of patients i) requiring radiological screening and ii) a subset with proven LAOS. 4. Construction of pre-hospital models for i) and ii). 5. Stakeholder interviews about the content and implications of a pre-hospital LAOS pathway. 6. A feasibility evaluation of the pathway. 7. A pragmatic clinical trial of the pathway. LAY TITLE: A new paramedic assessment to speed up treatment of stroke due to a blocked large artery. LAY: Approximately 80% of stroke is caused by a blocked blood vessel. One third of these patients have blockage of a large vessel in the neck or brain known as large artery occlusion stroke (LAOS). This often causes severe problems, but chances of recovery are greater if the blockage is removed quickly. It has recently been shown that pulling the blockage out of the artery (mechanical thrombectomy) within 6 hours of the symptoms starting is more effective than a clot-dissolving injection by itself (intravenous thrombolysis). However there are few hospitals providing thrombectomy, and most patients with a large artery blockage will need to be identified first at local stroke units and then taken to regional centres. An initial scan of the brain’s arteries (CT angiogaphy) and an additional ambulance journey is required. This often creates a delay of one hour before the patient arrives at the thrombectomy hospital, and chances of a good recovery will be lower than if they had been taken there directly. But as only 10% of stroke patients overall are suitable for thrombectomy, it would be inefficient for all to be taken directly to the regional hospital first. This programme will develop and test a new care pathway for paramedics to recognise those patients who are likely to have a large artery blockage, so that this group can be taken directly to the thrombectomy hospital. The assessment will reflect a combination of the best published evidence about symptom checklists to identify patients; a new fingerprick blood test for measuring natural chemicals (purines) which increase when body tissues are starved of oxygen, as higher levels may reflect blockage of a larger artery; the use of telephone or video in the ambulance to enable a hospital stroke specialist to review the patient; and stakeholder views about feasibility and acceptability.

Research activity codes: 8.1 ORGANISATION AND DELIVERY OF SERVICES
Health categories: STROKE