EMS stroke field triage improves outcomes

LOS ANGELES – An emergency medical services protocol to identify large vessel occlusions and deliver patients to a comprehensive stroke center if it is within 30 minutes of travel time reduced the time to recanalization when compared against a separate protocol that optimized transfer of such patients from primary to comprehensive stroke centers.

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 emergency medical services (EMS) units will improve outcomes, because field stroke severity scores won’t always be accurate, and longer travel to a comprehensive stroke center (CSC) could delay treatment to a patient who doesn’t need thrombectomy.

^{Jim Kling/Frontline Medical News}

Dr. Ryan McTaggart

The region where the study was carried out has one CSC and eight primary stroke centers (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), followed by CT and CT angiography. They then shared the resulting images with the CSC, which could make a decision whether to transfer the patient.

The field-based protocol relied on a LAMS score assessment by EMS personnel. Patients scoring 4 or 5 would then be delivered to the CSC if it was within 30 minutes from their current location. Patients scoring less than 4 would be brought to the nearest facility. In cases when the field LAMS score was 4 or greater and the nearest CSC was more than 30 miles 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 a CSC, process outcomes were better with the field triage protocol. “Despite 8 additional minutes of transport time, IV TPA 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 2 or 3, so you have this tremendously powerful treatment effect for these patients. If you can get it to them an hour earlier, it’s a no-brainer to me that they need to go to the right place the first time,” he said.

Instituting the changes was no picnic. Dr. McTaggart spent thousands of hours working with EMS personnel and emergency department physicians at PSCs. “It’s 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’re potentially saving patients from disability health care costs,” he said.

The study population included consecutive stroke patients in the region whose first contact was with EMS personnel during three time periods: before either change was made: (pre PSC-CSC transfer optimization, pre field triage, July 2015 to January 2016), after PSC optimization but only voluntary field triage (January 2016 to January 2017), and when both PSC optimization and field triage were mandatory (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 (PSC or CSC) to alteplase treatment, arterial puncture, and recanalization. Clinical measures included favorable outcomes (modified Rankin scale score 0-2) at 90 days, or discharge with a National Institutes of Health 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 change, 100 after PSC optimization, and 94 after both PSC optimization and field triage were implemented. A Google Maps analysis showed that the median additional time required to travel to a CSC instead of a PSC was 8 minutes (interquartile range 4-12).

The time to first use of IV alteplase dropped from 54 minutes before any change to 49 minutes after PSC optimization, and 36 minutes after both PSC optimization and field triage. Similar drops were seen in time to arterial puncture (105 minutes, 101 minutes, 88 minutes) and time to recanalization (156 minutes, 132 minutes, 116 minutes). These differences did not reach statistical significance.

The clinical outcomes also became more favorable: 58% had a favorable outcome at 90 days with both protocols in place, compared with 51% with only PSC optimization and 31% before any changes (P = .049 for 31% to 58% comparison).

The researchers conducted a subanalysis of 150 patients for whom the PSC was closest. Of these, 94 went to a CSC and 56 went to a PSC. The elapsed time between EMS leaving the scene with the patient aboard and IV TPA treatment was an average of 51 minutes in patients taken to the CSC, compared with 68 minutes in patients taken to PSCs (P = .012). The time to arterial puncture was also shorter (98 minutes versus 155 minutes; P less than .001), as was time to recanalization (131 minutes versus 174 minutes; P less than .001).

CSC patients were more likely to have a favorable outcome (65% versus 42%; P = .01).

The study received no external funding. Dr. McTaggart reported having no financial disclosures.