LONDON—A specialized ambulance may enable more patients with acute ischemic stroke to receive thrombolytic therapy than standard emergency response vehicles do. According to preliminary results of the randomized controlled PHANTOM-S study, patients with stroke received IV t-PA 25 minutes sooner when the stroke emergency mobile (STEMO) unit was in service than when it was not.
“We have shown that the STEMO concept can be integrated into a metropolitan emergency medical system,” said Heinrich Audebert, MD, at the 2013 European Stroke Conference. Dr. Audebert, the leader of the STEMO project, which is based at Charité-Universitätsmedizin Berlin, added that the approach was “safe and superior to regular [emergency] care, regarding the quality of care, the proportion of patients receiving t-PA, and the time to treatment.” The mobile stroke unit also could treat patients with intracranial hemorrhage and triage for interventional treatment, he suggested.
The PHANTOM-S study
The STEMO project aims to improve stroke patients’ clinical care by enabling t-PA to be administered before the patient arrives at the hospital. To achieve this goal, an ambulance owned by the Berlin Fire Department was adapted to accommodate an on-board CT scanner, a point-of-care laboratory, and a teleradiography system. A paramedic, a neurologist with training in emergency medicine, and a radiographer formed the staff of this specialized mobile stroke unit.
The PHANTOM-S (Pre-Hospital Acute Neurological Treatment and Optimization of Medical Care in Stroke) study followed a three-month pilot study that provided proof of concept for the STEMO unit in 23 hospitals in the Berlin area. The larger, randomized study involved 28 hospitals in the region that provide emergency services to approximately 1.3 million people.
During the PHANTOM-S study, the STEMO vehicle was in service during alternating weeks. The weeks when the specialized ambulance was not deployed were used as the control period. The investigators used their previously developed stroke identification algorithm to decide whether to deploy the STEMO unit to an emergency call.
Over a 21-month study period, 7,098 patients with suspected stroke were enrolled, and 6,573 were transported to the nearest adequately equipped hospital. Approximately half of subjects were evaluated during the weeks that the STEMO vehicle was in service. During the in-service weeks, the STEMO vehicle was deployed a total of 2,027 times out of 3,668 calls. The researchers gathered enough data for study evaluation for 1,804 patients examined by the unit. Of these subjects, 201 of 614 (33%) patients with acute ischemic stroke were given t-PA before reaching the hospital.
Approximately 29% of patients with stroke received prehospital thrombolysis when the STEMO unit was in service, compared with 21% of patients evaluated during control weeks. The difference between the two study arms was statistically significant. The percentage of patients subsequently transported to a hospital with a dedicated stroke unit was also higher during the weeks when the STEMO unit was in service than during the control weeks (93% vs 87%).
STEMO Was Associated With Decreased Time to t-PA
The mean time from deployment to treatment was 77 minutes when the specialized ambulance was not in use, compared with 62 minutes when it was, said Dr. Audebert. This time was reduced to 52 minutes if the STEMO unit was deployed and decreased to 48 minutes for patients who received t-PA in the mobile unit. In-hospital death rates in confirmed stroke cases were 4.4% for the STEMO in-service weeks (3.8% if the unit was deployed) and 4.5% for control weeks.
Among patients who received t-PA, there was a nonsignificant trend toward a lower incidence of intracranial hemorrhage if t-PA was delivered in the STEMO unit. Approximately 3.5% of patients treated in the STEMO unit had intracranial hemorrhage, compared with 4.8% of subjects overall during intervention weeks and 6.0% of subjects overall during control weeks.
“The current response time is about 16 minutes,” said Dr. Martin Ebinger, MD, PhD, one of the study’s coinvestigators, at a press briefing. “Sometimes there were multiple, simultaneous calls,” he added. If there were two mobile stroke units, then more people in the catchment area could be evaluated, and response time could possibly be halved, he explained.
“We need a good, independent cost-effectiveness analysis,” observed Dr. Ebinger. Discussions with patient insurance groups and politicians have been initiated to determine how best to conduct such an analysis.
“It certainly makes sense to get the treatment to patients as quickly as possible, but we need a CT scan of every patient before we give the treatment,” said Martin Brown, MD, Professor of Stroke Medicine at University College London, in an interview. The real question is whether it is more efficient to get the patient to the hospital as quickly as possible or whether neurologists should follow the STEMO model and seek funding for more expensive ambulances, he added.