Background: Donation after circulatory death (DCD) can reduce organ transplant waiting times. When defining death using circulatory criteria, brain function is usually not assessed. Residual brain function and the state of consciousness at the time of circulatory arrest is unknown. We have an ethical responsibility to ensure the donor is free of pain and psychological distress. Methods: We performed a scoping review of the literature to determine the time intervals associated with the loss brain function after circulatory arrest. Results: A total of 1133 articles were reviewed and 38 were included in the review. In humans, 8 studies showed loss of EEG activity under 30 seconds. Four studies revealed loss of EEG between 39.6 and 66 seconds. Clinically, loss of consciousness was shown to occur between 4 and 21 seconds. In animals, 13 studies also revealed loss of EEG under 30 seconds. In four other animal studies, EEG was lost between 37 and 120 seconds. Conclusion: The time required to lose brain function varied according to clinical context and method by which this function is measured. Existing literature is scarce and limited to observational studies and case reports.