LOS ANGELES—An emergency medical services (EMS) protocol to identify large-vessel occlusions and deliver patients to a comprehensive stroke center (CSC) within 30 minutes reduced the time to recanalization, when compared with a protocol that optimized the transfer of such patients from primary stroke centers (PSCs) to CSCs. The study was presented at the International Stroke Conference 2018.
The findings, which come from a sequential study conducted in an urban Rhode Island region, offer evidence to resolve the controversy over whether field triage in EMS units will improve outcomes. The controversy arose from concerns that stroke severity scores measured in the field are not always accurate, and that longer travel to a CSC could delay treatment for a patient who does not need thrombectomy.
“A lot of people have done mathematical modeling, but nobody has done the work to change the system so we can see what happens. This is the first study that has shown a real-world example of what it means for patients,” said Ryan McTaggart, MD, Director of Interventional Neuroradiology at Brown University Rhode Island Hospital in Providence.
Ryan McTaggart, MD
Instituting a Transfer Protocol
The region where the study was carried out has one CSC and eight PSCs. The large-vessel occlusions transfer protocol instructed PSCs to contact the CSC when a patient scored 4 or 5 on the Los Angeles Motor Scale (LAMS) and to conduct CT and CT angiography. The PSC was instructed to share the images with the CSC, which decided whether to transfer the patient.
The field-based protocol relied on a LAMS score assessment by EMS personnel. Patients scoring 4 or 5 would be delivered to the CSC if it was within 30 minutes of their current location. Patients scoring less than 4 would be brought to the nearest facility. When the field LAMS score was 4 or greater and the nearest CSC was more than 30 minutes away, EMS personnel were instructed to travel to the closest PSC, but immediately send word of an inbound patient that might need a transfer to a CSC. In those cases, the PSC’s goal was to get images to the CSC for review within 45 minutes. The protocol was executed out to 24 hours after the patient was last known well.
Even in patients who were closer to a PSC than the CSC, process outcomes were better with the field triage protocol. “Despite eight additional minutes of transport time, IV t-PA was given 17 minutes earlier, and recanalization occurred almost an hour earlier,” said Dr. McTaggart. “That would indicate that perhaps even a 30-minute window is too conservative of a protocol, because the number needed to treat for mechanical thrombectomy is two or three, so you have this tremendously powerful treatment effect for these patients. If you can get it to them an hour earlier, it is a no-brainer to me that they need to go to the right place the first time,” he said.
Instituting the changes was difficult. Dr. McTaggart spent thousands of hours working with EMS personnel and emergency department physicians at PSCs. “It is a lot of work, but the downstream gains are huge, not only from a disability standpoint for patients, but for the economics of the health care system. We are potentially saving patients from disability health care costs,” he said.
Travel Time Increased
The study population included consecutive stroke patients in the region whose first contact was with EMS personnel during the following three time periods: before PSC–CSC transfer optimization and before field triage (ie, July 2015 to January 2016), after transfer optimization and with voluntary field triage (ie, January 2016 to January 2017), and when transfer optimization and field triage were mandatory (ie, January 2017 to January 2018).
The patients had an anterior large-vessel occlusion and mild-to-moderate early ischemic change. Outcomes included time from hospital arrival (ie, PSC or CSC) to alteplase treatment, arterial puncture, and recanalization. Clinical measures included favorable outcomes (ie, modified Rankin scale score 0–2) at 90 days, or discharge with an NIH Stroke Scale score of 4 or less, in cases where 90-day follow-up did not occur.
A total of 38 patients were seen before any procedural change occurred, 100 after transfer optimization, and 94 after transfer optimization and field triage were implemented. A Google Maps analysis showed that the median additional time required to travel to the CSC instead of a PSC was eight minutes.
The time to first use of IV alteplase decreased from 54 minutes before any procedural change to 49 minutes after transfer optimization and to 36 minutes after transfer optimization and field triage. Similar decreases were seen in time to arterial puncture (105 minutes, 101 minutes, and 88 minutes, respectively) and time to recanalization (156 minutes, 132 minutes, and 116 minutes, respectively). These differences did not reach statistical significance.
The clinical outcomes also became more favorable. Approximately 58% of patients had a favorable outcome at 90 days with both protocols in place, compared with 51% with only transfer optimization and 31% before any procedural changes.
The researchers conducted a subanalysis of 150 patients for whom a PSC was closer than the CSC. Of these patients, 94 went to the CSC and 56 went to a PSC. The elapsed time between EMS leaving the scene with the patient aboard and IV t-PA treatment was an average of 51 minutes in patients taken to the CSC, compared with 68 minutes in patients taken to PSCs. The time to arterial puncture was also shorter (98 minutes vs 155 minutes), as was time to recanalization (131 minutes vs 174 minutes).
Patients taken to the CSC were more likely to have a favorable outcome (65% vs 42%).
The study received no external funding. Dr. McTaggart reported no financial disclosures.
—Jim Kling