SGEM#330: Should You Be Going Mobile to Treat Acute Ischemic Stroke?

Date: May 6th, 2021 Guest Skeptic: Dr. Daniel Schwerin is employed with Prisma Health-Upstate as a clinical assistant professor, emergency medicine GME director for emergency medical services and medical director for several local EMS agencies and has lectured on prehospital stroke management. Reference: Fatima et al. Mobile stroke unit versus standard medical care in the management of patients with acute stroke: A systematic review and meta-analysis. International Journal of Stroke 2020 Case: A 70-year-old man develops sudden right-sided weakness beginning shortly after breakfast and his partner appropriately calls emergency medical services (EMS). Their local EMS service arrives quickly with a conventional ambulance. He has heard about these special ambulances with CT Scanners and wonders if that will make an important difference for his partner. Background: We have discussed stroke so many times on the SGEM. It is one of the five most popular topics like TXA, PE, POCUS and ketamine. Justin Morgenstern from First10EM and I recently downgraded the NNT website recommendation for tPA in acute ischemic stroke to “yellow”. A yellow recommendation means the benefits and harms are unclear due to the uncertainty in data. But something that often comes up when discussing stroke treatment is we need to go fast because time is brain. The term “time is brain” was coined by Dr. Camilo Gomez back in 1993. He modified his position in 2018 and said: “It is no longer reasonable to believe that the effect of time on the ischaemic process represents an absolute paradigm. It is increasingly evident that the volume of injured tissue within a given interval after the estimated time of onset shows considerable variability in large part due to the beneficial effect of a robust collateral circulation.” We never did have high-quality evidence to support the position that treating stroke patients earlier was better. All we had was an association because there were no RCTs that randomized stroke patients into getting thrombolytics early or late. This means there could have been unmeasured confounders responsible for the observed effect. The largest placebo controlled RCT looking at tPA for acute ischemic stroke was IST-3 which was covered on SGEM#29. There were several serious problems with that trial including: * Largely unblinded trial (91%) * Stopped early * Self-reported outcome by telephone or mailed questionnaire * No superiority for primary outcome * 4% absolute increase in early mortality Another interesting point about IST-3 is the subgroup analysis did not support the claim that time was brain. There was no statistical difference between the <3hrs, 3-4.5hrs and >4.5hrs. However, the point estimate favored tPA in <3hrs, then placebo between 3-4.5hrs and then back to tPA in >4.5hrs? You also need to look very carefully at the figure to see they used the 99% confidence interval instead of the standard 95% confidence intervals. If calculating the Odds Ratio for the 3-4.5hr group you find it is statistically significant favouring the placebo group. Clinical Question: Does a mobile stroke unit (MSU) with earlier imaging and delivery of tPA improve outcomes, or is the downstream effect of improved resources at a comprehensive stroke center that improves outcomes for patients with strokes? Reference: Fatima et al. Mobile stroke unit versus standard medical care in the management of patients with acute stroke: A systematic review and meta-analysis. International Journal of Stroke 2020