Evidence Table and Reference List
Patients arriving to hospital using EMS (emergency medical services) following a stroke experience fewer delays in receiving appropriate diagnostic tests (e.g. brain imaging) and are more likely to receive t-PA, if eligible. Patients are also more likely to receive timely transportation and care when pre-notification systems, including the use of trained EMS dispatchers, are adopted. Watkins et al. (2013) reported that the percentage of patients whose final diagnosis was stroke increased significantly (63% to 80%, p<0.01) after EMS dispatchers completed training, aimed at improving their ability to detect suspected stroke patients. In a study that included 27,566 patients who were identified as suspected stroke patients by dispatchers, the mean times associated with transportation, including time to scene, time at scene, time from scene to destination and total transportation time were all significantly reduced, compared to persons whose final diagnosis was stroke, but who were not identified by dispatchers (Caceres et al. 2013). Berglund et al. (2012) reported that patients in the Hyper Acute STroke Alarm (HASTA) Study assigned an upgraded priority level by dispatching personnel experienced fewer delays along the chain of stroke care from symptom onset to arrival at a stroke unit and were more likely to be treated with t-PA compared with patients who had been assigned to a standard-priority level by the emergency medical communications centre. Patients classified as Priority Level 1 received thrombolysis more often than those classified as priority level 2 (24% vs. 10%, p<0.001) and a greater number arrived at the stroke unit within 3 hours of symptom onset (61% vs. 46%, p=0.008).
Hospital pre-notification typically involves informing emergency department physicians and other relevant personnel (blood and EKG technicians, radiologists and pharmacologists) of the arrival of a potential stroke patient. The results from several studies indicate that the process indicator associated with thrombolysis treatment may be shortened for patients arriving to hospitals by EMS with prenotification protocols. Lin et al. (2012) included data from 371,988 acute ischemic stroke patients from the Get with the Guidelines database and reported that among patients transported to hospital using EMS pre-notification, they had significantly shorter door-to-imaging time (26 vs 31 mins, p<0.001), door-to-needle time (78 vs 81 mins, p<0.001), and stroke onset-to-needle time (141 vs 145 mins, p<0.001). Furthermore, of those who arrived at hospital within 2 hours of stroke onset, patients with a pre-notification were significantly more likely than those without to receive t-PA within 3 hours of stroke onset (73% vs 64%, p<0.001). In another US study based on registry data (Patel et al. 2011), of 13,894 patients who whose discharge diagnosis was stroke, patients arriving by EMS with hospital pre-notification were more likely to have brain imaging completed within 25 min (RR= 3.0, 95% CI 2.1-4.1) and to have the results interpreted within 45 min (RR= 2.7, 95% CI 2.3-3.3) compared to arriving by private transport. Patients eligible for t-PA were more likely to receive it if arriving by EMS with pre-notification (RR=1.5, 95% CI 1.1-1.9). Dalloz et al. (2012) included the results from 10 studies in a systematic review examining the use of pre-hospital stroke codes. A stroke code system was defined as efforts to improve the identification, transport and presentation of suspected stroke patients to the emergency department. The odds of treatment with thrombolysis were highest in settings that had a pre-hospital stroke code system in place compared with facilities with no stroke code (OR= 5.43, 95% CI: 3.84-7.73, p<0.001), and were lower in studies comparing pre-hospital stroke code with in-hospital stroke codes (OR=1.97, 95% CI: 1.53-2.54, p<0.001).
In the last several years, as endovascular techniques are becoming more widely available, several on-scene screening tools to identify patients with large vessel occlusions (LVO), designed for use by EMS technicians, have emerged. Examples of these scales include Field Assessment Stroke Triage for Emergency Destination (FAST-ED) (Lima et al. 2016), Vision, Aphasia, and Neglect (VAN) (Taleb et al. 2016), the Prehospital Acute Stroke Severity Scale (PASS) (Hastrup et al. 2016), Cincinnati Prehospital Stroke Severity Scale (CPSSS) (Katz et al. 2015), and The Los Angeles Motor Scale (LAMS) (Nazliel et al. 2008). Most of these scales are based on 3-6 selected items from the National Institutes of Health Stroke Scale. The sensitivities and specificities associated with these scales range from 61% to 100% and 40% to 92%, respectively. Smith et al. (2018) included the results from 36 studies evaluating the accuracy of LVO prediction scales in patients with suspected stroke or presumed acute ischemic stroke in pre-hospital or emergency department settings. The authors concluded that no scale had both high sensitivity and specificity to determine the presence vs. absence of LVO, and that in clinical practice that the probability of LVO given a negative test could still be ≥10%.
The use of mobile stroke units, ambulances which are equipped with specialized equipment, such as on-site laboratories and CT scanners, and are staffed with additional personnel with stroke expertise, are now appearing in some large, urban cities. Their feasible and effectiveness are the subjects of ongoing investigation. Kunz et al. (2016) compared the outcomes of patients who received thrombolysis therapy using the mobile stroke unit, STEMO from 2011-2015 with patients who received thrombolysis, but arrived at hospital via traditional emergency medical services. A significantly higher proportion of patients in the STEMO group were treated ≤ 90 minutes of stroke (62% vs. 35%, p<0.0005) and were living without severe disability at 3 months (83% vs. 74%, p=0.004). The 3-month mortality was also significantly lower in the STEMO group (6% vs. 10%, p=0.022). However, there was no significant difference in the primary outcome, the number of patients who achieved an excellent outcome (mRS 0-1) at 3 months (53% STEMO vs. 47% conventional, p=0.14). There were no significant differences in the safety outcomes between the 2 groups (sICH 3% vs. 5%, p=0.27 and 7-day mortality 2% vs. 4%, p=0.23). Adjusting for baseline characteristics, STEMO was an independent predictor of living without severe disability at 3 months (OR=1.86, 95% CI 1.20-2.88, p=0.006), but not for the primary outcome (OR=1.40, 95% CI 1.00-1.97, p=0.052). In an earlier study examining the use of STEMO, (Ebinger et al. 2014), among patients for whom STEMO was deployed, the mean alarm-to-treatment time for patients who received thrombolysis was reduced by 25 minutes, compared with control weeks. Of the eligible patients, t-PA was used in 32.6% of STEMO deployment cases, 29% during STEMO weeks, and 21.1% during control weeks.