BACKGROUND: The total amount of heparin administered through flush fluids in stroke patients is not considered in recent trials, possibly influencing main results. We investigated the use of heparin among treating physicians worldwide. METHODS: We conducted a survey from November 2022 to January 2023 to identify the variability of heparin administration during stroke endovascular treatment (EVT). We calculated the total heparin dose per hour (IU/h) by adding the intravenous (IV)-bolus dose to the amount administered through flush fluids, calculated by a multiplication of the number of infusion bags, drip rate[mL/h] and heparin concentration[IU/L]. RESULTS: A total of 315 participants from different countries worldwide completed the survey and 231/315(73%) respondents administer heparin during EVT. The majority administered heparin only through flush fluids (168/231
72.7%), followed by both IV-bolus and flush fluids (36/231
16%), and those who used only an IV-bolus (27/231
11.7%). From the participants that administer heparin through flush fluids, the median heparin concentration was 2000 IU/L (range:100 IU/L-10000 IU/L). The total heparin dose (administered through flush fluids and IV-bolus) among 23 respondents showed a median of 4650 IU/h (IQR:3432-5900). Among the respondents who administer heparin through IV-bolus only, the median was 5250 IU (IQR:3750-7500). CONCLUSION: This survey revealed variable heparin doses administered by physicians worldwide during EVT and reflects the lack of international guidelines. Caution is warranted, specifically during complex/long EVT procedures. Furthermore, heparin flush doses should be considered in future trials regarding periprocedural anticoagulants, since imbalances could potentially confound results.