Is the ‘platinum half-hour’ achievable for stroke treatment?


By Rosanne Barrett

19 May 2022

Moving beyond the “golden hour” to treat stroke patients within a “platinum half-hour” timeframe has been demonstrated as an attainable target — though the impact of the rapid intervention has been questioned.

A cohort study, published in Stroke, found about one in eight (12.1%) patients during the 2005 to 2013 research period were able to receive neuroprotective therapies within 30 minutes of their last-known-well time across counties in California.

However an Australian expert has cast doubt on the study’s current relevance, given the contemporary best practice requirement for CT scans and other testing before the administration of therapy in the event of stroke.

University of Melbourne Co-Chair of the Melbourne Mobile Stroke Unit and the Chair of Translational Neuroscience at the Royal Melbourne Hospital, Professor Steven Davis, said it was not realistic to treat patients within 30 minutes and the goal should remain the “golden hour”, treatment within 60 minutes of the onset of symptoms.

“I don’t think this study is relevant to contemporary stroke care, although it does emphasise the principle that ‘time is brain’ and the aim should be to treat as quickly as possible,” he said.

“We are treating about 18% of patients in the ‘golden hour’, and we treat virtually no one in 30 minutes.

“To get within 30 minutes — and this is with a mobile stroke unit — the patient has to be picked up, they have to have the scan, they have to have all the eligibility testing for thrombolysis which previously wasn’t routine [at the time of this study].

“[This] study used standard ambulances without CT scanners.

“It [30 minutes] was only achievable in this study because they didn’t need to do CT before giving the magnesium sulphate.”

The Field Administration of Stroke Therapy — Magnesium trial tested treatment and outcomes of patients with cerebral ischaemia and intracranial haemorrhage in a randomised, double-blind, phase 3 clinical trial. It ran from 2005 to 2013 in 40 emergency medical system agencies, 315 ambulances and 60 acute care-receiving hospitals in Los Angeles and Orange Counties.

It built on the foundation of the “golden hour” for stroke treatment, to improve patient functional outcomes, given magnesium sulphate neuroprotective agents were highly time-dependent.

“The terms platinum 30 minutes and platinum 10 minutes have been advanced for the most challenging and most beneficial time windows for intervention, when disease processes are least advanced and most reversible,” the study said.

“To our knowledge, the frequency, characteristics, and outcomes of platinum 30-minute patients has not been previously well characterised.”

The study found a stronger association between younger people experiencing more severe deficits after both acute cerebral ischaemia, (which accounted for 71.8% of patients, including ischaemic stroke, 61.5% and TIA 10.3%), and those who experienced intracranial haemorrhage (26.1%).

Authors noted this was likely due to younger people having more social engagement, meaning more people could witness the event, and the discomforting symptoms of the haemorrhage leading people to call emergency services.

While patients were more likely to be younger, with greater pre-hospital deficits, their outcome at three months was comparable to patients who were treated outside the 30-minute window.

“It is noteworthy that three-month outcomes did not differ among platinum half-hour patients and later-treated patients,” the authors said.

“This result indicates that platinum half-hour presentation, compared with slightly later presentation, has only limited prognostic value regarding final outcome. However, once a beneficial therapy able to be started in ambulances becomes available, platinum half-hour treatment is likely to be associated with maximal intervention benefit. Platinum half-hour status would then be a biomarker that is predictive but not prognostic.”

Professor Davis said pre-hospital treatment was the vanguard of stroke treatment, pointing to the Melbourne mobile stroke unit model that achieved 18% of patients treated with thrombolysis within 60 minutes, compared to 1.5% of patients treated within an hour in emergency departments.

“Mobile stroke units not only shorten the time for treatment, but they have proven to improve clinical outcomes,” he said.

He said in a standard emergency department about 13% of patients were treated in 90 minutes [the “silver hour”], while 50% were treated within the same time period with a mobile stroke unit.

“I think the ‘golden hour’ or the ‘silver hour’ should be the main targets,” he said.

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