Fig. 4

Effect estimates of undergoing general anesthesia on the good functional outcome (mRS 0–2 at 90 days) from four statistical methods of A-1 logistic regression, A-2 generalized estimating equation, B ecological analysis, and C instrumental variable analysis. ^# Case-mix variables in the models are including age, sex, medical history, NIHSS score baseline, and time from onset to arrival at the ED of intervention hospital. Hospital volume was also added to the instrumental variable analysis. * Difference in the absolute probability of a good functional outcome for every 1% of the cases receiving general anesthesia. For example, the unadjusted coefficient implies that the absolute probability of a good functional outcome is 0.05% higher for a patient treated at a hospital utilizing general anesthesia in 1% of the cases compared with one not utilizing the intervention