Reaching stroke patients in time to give life-saving treatment

The outcome

Eighteen per cent of stroke patients who get clot-dissolving drugs in the Mobile Stroke Unit (MSU) in Melbourne are treated within the ‘golden hour’ – the first hour after stroke onset. Only 1.5 per cent of stroke patients are treated in this time when they travel to hospital by standard ambulance.

Fifty-one per cent are treated within the ‘silver hour’ – the first 90 minutes after stroke onset – compared with 12 per cent who travel to hospital by standard ambulance. Early treatment for stroke is crucial to limit irreversible brain damage.

The MSU is a custom-built ambulance crewed by stroke specialists. They can diagnose and treat strokes at the scene, before patients get to hospital. Early diagnosis also ensures that the patient is taken to the best hospital for further treatment, which is not always the nearest.

Currently the only stroke ambulance in Australia, the MSU operates within a 20 kilometre radius of the Royal Melbourne Hospital. That area covers around 1.7 million people. Since its launch in November 2017, the MSU has attended an estimated 38 per cent of suspected stroke cases in this area during the times it was operating.

The MSU led to an estimated 44.84 disability-adjusted life years (DALYs) avoided across 200 days in 2018. One DALY is one year of healthy life lost as a result of disability or premature death.

The need

The earlier that stroke patients can be diagnosed and treated, the better their outcome.

In Australia, only 35 per cent of ischaemic stroke patients reach hospital in time to receive drug treatment. Ischaemic strokes are the most common type of stroke. They are caused by a blood clot blocking the supply of oxygen to the brain. Clot-dissolving drugs must be given within 4.5 hours of stroke onset. Treatment outside this window can be dangerous or even fatal. It is possible within 9 hours of stroke onset, but only after extensive brain imaging and risk analysis in hospital.

Strokes are a leading cause of death and disability worldwide. Each year, they affect more than 13 million people and cause 5.5 million deaths. By disrupting blood supply to the brain, strokes deprive brain cells of oxygen. For every minute that treatment is delayed, an average of 2 million neurons die. This causes irreversible damage to the brain.

Developing the solution

Professor Stephen Davis and Professor Geoffrey Donnan became interested in the idea of a specialised stroke ambulance after seeing them in early-stage development in Europe and North America. Their research is focused on stroke management, and they both have clinical positions at the Royal Melbourne Hospital.

In 2016, they embarked on a five-year project that aims to change how stroke is treated and managed – including before patients reach hospital.

The researchers worked with Ambulance Victoria to design a vehicle that would fit wherever a standard ambulance can go. Some stroke ambulances in other countries are far bigger, which limits their usefulness. Anonymous philanthropists contributed $A1 million to build the MSU on a Mercedes-Benz Sprinter chassis.

The MSU is equipped with a mobile CereTom® computed tomography (CT) scanner, which is used to scan a patient’s brain for immediate diagnosis. The CT scanner was donated by the Stroke Foundation. It is wireless and weighs around 500 kilograms. Regular hospital CT scanners can weigh up to 3000 kilograms. The MSU team can consult with hospital neurologists using an in-built two-way audio-visual system.

The MSU was launched in November 2017. It operates on weekdays from 8am to 6pm. When Ambulance Victoria receives a 000 (emergency) call for a suspected stroke, both the MSU and a normal ambulance are dispatched to the scene. This dual-dispatch model is the standard around the world.

Around 9 per cent of stroke patients who have received clot-dissolving drugs in the MSU were treated within 3.5–4.5 hours of stroke onset. This means they probably would not have made it to hospital in time for treatment.

More than half of the stroke patients the MSU attends cannot be treated with clot-dissolving drugs in the MSU. In some cases, 4.5 hours have already elapsed since their stroke occurred. In other cases, it’s not possible to tell if the stroke occurred within 4.5 hours (the window in which these drugs can be used without advanced imaging in hospital). Some patients ignore symptoms for too long. Others wake up with symptoms after a stroke sometime during the night. If a patient cannot be treated by the MSU, the standard ambulance takes them to the best hospital for treatment.

The MSU costs around $A1.6 million a year. This includes staffing, medical equipment and drugs, and vehicle costs. More than $A200 000 in annual healthcare costs is saved by the MSU, by reducing the use of emergency departments and the need to transfer stroke patients between hospitals. The MSU cost an estimated $A30 982 more than standard care for each DALY avoided in 2018. In Australia, an intervention that costs less than $A50 000 per DALY is typically considered to be cost-effective.

The MSU’s costs are paid by the Victorian Government, the National Health and Medical Research Council and the Medical Research Future Fund through funding for clinical trials. Stroke patients who are treated by the MSU have taken part in multiple clinical trials. One phase II trial (STOP-MSU) is testing whether tranexamic acid can slow bleeding in haemorrhagic strokes. This drug is currently used to control heavy bleeding during menstrual periods.

Based on the success of the MSU, Professors Davis and Donnan are now working with the Australian Stroke Alliance to create a new MSU with advanced technology in partnership with Siemens Healthineers, the healthcare division of Siemens.

Video: Australian Stroke Alliance

Partners

Royal Melbourne Hospital

Ambulance Victoria

Stroke Foundation

Royal Melbourne Hospital Neuroscience Foundation

Funding

NHMRC Program Grant (1113352) – Saving brain and changing practice in stroke.

Medical Research Future Fund, Lifting Clinical Trials and Registries Capacity

Victorian Government

Publications

Zhao H et al (2020) Melbourne Mobile Stroke Unit and reperfusion therapy: Greater clinical impact of thrombectomy than thrombolysis. Stroke 51: 922–930. doi: 10.1161/STROKEAHA.119.027843

Kim J et al (2020) Economic evaluation of the Melbourne Mobile Stroke Unit. International Journal of Stroke, doi: 10.1177/1747493020929944

Phan TG et al (2019) Googling boundaries for operating Mobile Stroke Unit for stroke codes. Frontiers in Neurology 10: 331. doi: 10.3389/fneur.2019.00331

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