Accuracy of Emergency Medical Services–Reported Last Known Normal Times in Patients Suspected With Acute Stroke

Abstract

Background and Purpose The last known normal (LKN) time is a critical determinant of IV tPA eligibility; however, the accuracy of EMS-reported LKN times is unknown. We determined the congruence between EMS-reported and neurologist-determined LKN times and identified predictors of incongruent LKN times. Methods We prospectively collected EMS-reported LKN times for patients brought into the ED with suspected acute stroke and calculated the absolute difference between the EMS-reported and neurologist-determined LKN times (|ΔLKN|). We determined the rate of inappropriate IV tPA use if EMS-reported times had been used in place of neurologist-determined times. Univariate and multivariable linear regression assessed for any predictors of prolonged |ΔLKN|. Results Of 251 patients, mean and median |ΔLKN| were 28 and 0 minutes, respectively. |ΔLKN| was <15 min in 91% of the entire cohort and was <15 min in 80% of patients with a diagnosis of stroke (n=86). Of patients who received IV tPA, none would have been incorrectly excluded from IV tPA if the EMS LKN time had been used. Conversely, of patients who did not receive IV tPA, 6% would have been incorrectly included for IV tPA consideration had the EMS time been used. In patients with wake-up stroke symptoms, EMS underestimated LKN times: mean EMS LKN time - neurologist LKN time = −208 minutes. The presence of wake-up stroke symptoms (p<0.0001) and older age (p=0.019) were independent predictors of prolonged |ΔLKN|. Conclusions EMS-reported LKN times were largely congruent with neurologist-determined times. Focused EMS training regarding wake-up stroke symptoms may further improve accuracy.

Prehospital care delivery and triage of stroke with emergent large vessel occlusion (ELVO): report of the Standards and Guidelines Committee of the Society of Neurointerventional Surgery

“…Many treatment decisions related to acute stroke depend upon an accurate time of onset or LKN time, and this knowledge is critical in evaluation of the patient with ELVO stroke. Agreement between EMS-determined time of onset and hospital neurologist LKN times has been shown when personnel are appropriately trained 51. Factors associated with incongruence were older patient age and wake-up strokes.…”

Accuracy of First Recorded “Last Known Normal” Times of Stroke Code Patients

“…A recent study 5 with 251 patients showed overall consistency between EMS LKN time and revised time, with the difference in LKN being under 15 minutes in 91% of the cohort and under 15 minutes in 80% of stroke patients. In that study, among patients who received IV rt-PA, none would have been incorrectly excluded from IV rt-PA if the EMS LKN time had been used.…”

“…If a patient wakes up with stroke symptoms, the LKN time may reflect the time of awakening instead of the true LKN time (often the prior night). A recent study 5 with 251 patients showed that in patients with wake-up stroke symptoms, EMS underestimated LKN times with an average difference in LKN times of over 3 hours. The LKN time can also, unfortunately, be reported as ‘about an hour ago’ or similar phrase.…”

Is It Acute Stroke or Not? - A Prospective Observational Study from a Multidisciplinary Emergency Department

“…Patients erroneously presented as 'within TW' might lead to delayed treatment of patients who are really in the TW if these patients are presented simultaneously or within short time intervals. Underestimation of TW by the EMS, especially in patients with wake-up stroke [24] and elderly patients [25] has been reported. The reasons for these misinterpretations are probably multifactorial: in our study, we observed that persons involved in the acute situation were not all aware of the small but crucial difference between the terms 'symptom recognition' and 'symptom onset'.…”