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BACKGROUND AND OBJECTIVES The effect of anesthesia choice on endovascular thrombectomy(EVT) outcomes is unclear. Collateral status on perfusion imaging may help identify the optimal anesthesia choice. METHODS In a pooled patient level analysis of EXTEND-IA, EXTEND-IA TNK, EXTEND-IA TNK part II and SELECT, EVT functional outcomes(mRS distribution) were compared between general anesthesia(GA) vs non-general anesthesia(non-GA) in a propensity matched sample. Further, we evaluated the association of collateral flow on perfusion imaging, assessed by hypoperfusion intensity ratio(HIR) - Tmax>10s/Tmax>6s(good collaterals - HIR<0.4, poor collaterals - HIR≥0.4) on the association between anesthesia type and EVT outcomes. RESULTS Of 725 treated with EVT, 299(41%) received GA and 426(59%) non-GA. The baseline characteristics differed in presentation NIHSS(median[IQR]-GA:18[13-22], non-GA:16[11-20],p<0.001) and ischemic core volume(GA:15.0mL[3.2-38.0] vs non-GA:9.0mL[0.0-31.0],p<0.001). Additionally, GA was associated with longer last-known-well(LKW) to arterial access (203min[157-267] vs 186min[138-252],p=0.002), but similar procedural time (35.5min[23-59] vs 34min[22-54],p=0.51). Of 182 matched pairs using propensity scores, baseline characteristics were similar. In the PS-matched pairs, GA was independently associated with worse functional outcomes(adj cOR:0.64,95%CI:0.44-0.93,p=0.021) and higher neurological worsening(GA:14.9% vs non-GA:8.9%, aOR:2.10,95%CI: 1.02-4.33,p=0.045). Patients with poor collaterals had worse functional outcomes with GA(adj cOR:0.47,95%CI:0.29-0.76,p=0.002), while no difference was observed in those with good collaterals(adj. cOR:0.93,95%CI:0.50-1.74,p=0.82), Pinteraction:0.07. No difference was observed in infarct growth overall and in patients with good collaterals, whereas patients with poor collaterals demonstrated larger infarct growth with GA with a significant interaction between collaterals and anesthesia type on infarct growth rate(Pinteraction:0.020). CONCLUSION GA was associated with worse functional outcomes after EVT, particularly in patients with poor collaterals in a PS matched analysis from a pooled, patient-level cohort from 3 randomized trials and one prospective cohort study. The confounding by indication may persist despite the doubly robust nature of the analysis. These findings have implications for randomized trials of GA vs non-GA and may be of utility for clinicians when making anesthesia type choice. CLASSIFICATION OF EVIDENCE This study provides Class III evidence that that use of general anesthesia is associated with worse functional outcome in patients undergoing endovascular thrombectomy. TRIAL REGISTRATIONS EXTEND-IA:ClinicalTrials.gov (NCT01492725); EXTEND-IA TNK:ClinicalTrials.gov (NCT02388061); EXTEND-IA TNK part II:ClinicalTrials.gov (NCT03340493); SELECT:ClinicalTrials.gov (NCT02446587).