Abstract 195: Drip and Ship vs. Mothership: a Comparison of Two Different Conditional Probability Models

Abstract

Introduction: There is uncertainty about the best treatment method for patients with suspected large vessel occlusion (LVO) stroke. The drip and ship [alteplase at a Primary Stroke Centre (PSC) and then transfer to a Comprehensive Stroke Centre (CSC) for endovascular therapy (EVT)] and mothership (bypassing the PSC in pursuit of EVT at a CSC) transport methods have been proposed. Earlier, these two methods were evaluated for patients with assumed known LVO. As LVO cannot be diagnosed without imaging we present an update for patients with suspected LVO using the Los Angeles Motor Scale (LAMS) screening tool. Methods: The expected distribution of LVO, non-LVO occlusions (nLVO), intracranial hemorrhages (ICH), and stroke mimics (SM) for patients with LAMS≥4 was combined with time dependent probability of good outcome for alteplase (for LVO and nLVO) and EVT, and probability of good outcome for ICH and SM to create conditional probability models for drip and ship and mothership scenarios. Results were mapped and compared with the previous model. Results: For patients with LAMS≥4 drip and ship and mothership predict equivalent outcomes in most areas (Figure-Panel A). Drip and ship is only relevant at PSCs that are far from CSCs. Increasing door to needle time (DNT) decreases the size of drip and ship areas. This contrasts with the prior model (Figure-Panel B) where mothership is more dominant especially as DNT increases. Conclusions: The inclusion of nLVO, ICH, and SM patients introduces important differences in modelling patient transport. This diagnosis uncertainty decreases the relative difference between the probabilities of good outcome for the two transport options.