Conference Coverage
SAN DIEGO – Having paramedics give intravenous magnesium to patients with acute stroke in the ambulance did not improve stroke-related disability 3 months later in a randomized, double-blind, placebo controlled trial of 1,700 patients.
Patients in both the magnesium and placebo groups had an average modified Rankin Scale score of 2.7, indicating slight to moderate levels of disability at 3 months.
But the negative results were balanced by the demonstration that stroke patients can receive potentially neuroprotective agents in the field, before arrival at a hospital, said Dr. Jeffrey L. Saver. The median time to treatment was 45 minutes after symptom onset and 74% of patients started treatment within an hour of symptoms, the "golden hour" when treatment may produce the best odds of survival and lowest odds of long-term neurological damage, he said at the International Stroke Conference. Another 25% of patients were treated within 1-2 hours of initial symptoms.
Sherry Boschert/Frontline Medical News
Dr. Jeffrey L. Saver (right) describes the failure and success of the FAST-MAG study while moderator Dr. Bruce Ovbiagele listens.
Already plans are underway to test other investigational therapies in the field, as researchers are encouraged by these results from the Field Administration of Stroke Therapy – Magnesium (FAST-MAG) trial, he said.
In a Danish trial, investigators are studying prehospital remote ischemic perconditioning for stroke patients. British and U.S. researchers are giving glyceryl trinitrate in the ambulance. Canadian researchers soon will start testing in-ambulance administration of NA-1, another potentially neuroprotective drug, said Dr. Saver, professor of neurology and director of the stroke center at the University of California, Los Angeles.
"We know that every minute that goes by without treatment, 2 million nerve cells are lost" after a stroke, he said at a press briefing.
The only approved treatment for strokes caused by clots is tissue plasminogen activator (TPA), which can’t be administered in ambulances because imaging studies are needed first to confirm a clot and avoid potentially harming patients with hemorrhagic stroke by giving them TPA.
The FAST-MAG study coordinated 315 ambulances, 40 emergency medical service agencies, 60 hospitals, and 2,988 paramedics in two California counties to evaluate 1,700 stroke patients in the field in 2005-2012 and begin IV treatment within 2 hours of symptom onset.
Patients aged 40-95 years with a likely stroke as identified by the Los Angeles Prehospital Stroke Screen received magnesium sulfate or matched saline placebo in the ambulance in a loading dose of 4 g over 15 minutes if they were within 2 hours of symptom onset and had neurological deficits present for 15 minutes or longer. When they arrived at the hospital, they received a maintenance infusion of 16 g magnesium or placebo over 24 hours.
"These were fairly severe stroke patients," with a mean pretreatment stroke severity score of 4 on the Los Angeles Motor Scale, which is roughly equivalent to a 13 on the National Institutes of Health Stroke Scale (NIHSS), he said at the conference, sponsored by the American Heart Association. They had a mean NIHSS score of 11 on arrival at emergency departments. The time from intake on the scene to the hospital door averaged 33 minutes, faster than an average 35 minutes in Los Angeles in prior data.
The final diagnoses included cerebral ischemia in 73% of patients, intracranial hemorrhage in 23%, and stroke mimics in 4%.
In six previous trials of neuroprotective agents in 5,345 patients, times from enrollment to treatment average longer than 3 hours in 92% of patients, 2-3 hours in 6%, 1-2 hours in 1%, and 0-1 hours in only 0.2% of patients, Dr. Saver said. (Percentages don’t equal 100% because of rounding.)
Overall rates of serious adverse events did not differ significantly between groups in the current study. The magnesium group had significantly higher rates of any respiratory complications (8% vs. 5%), hypotension (7% vs. 4%), and dyspnea or respiratory distress (4% vs. 2%), and a lower rate of neoplasms (1% vs. 2%), compared with the placebo group.
Previous animal studies found that IV magnesium dilated brain blood vessels and increased blood flow, and previous small trials in humans showed no overall harm or benefit but provided hints that magnesium might help if administered with a few hours of a stroke.
Dr. Saver reported having no financial disclosures. The trial was partly supported by the National Institute of Neurological Disorders and Stroke.
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