The relationship between cessation of brain and systemic circulation after withdrawal of life-sustaining measures

In donation after circulatory death, it is assumed that cessation of brain activity and brain blood flow occur close to the time of circulatory arrest. However, this assumption lacks direct empirical data that would support current death determination guidelines, ensure donor safety, and maintain public trust. We conducted a single-center prospective observational study of adult patients undergoing controlled withdrawal of life-sustaining measures. We measured systemic circulation using an indwelling arterial cannula and assessed brain blood flow with transcranial Doppler. In a subset of patients, we also recorded brain electrical activity using electroencephalography. Our results demonstrate that brain blood flow consistently stopped before or simultaneously with systemic circulation (median, -179 seconds; range, -458 to 0 seconds; P = .016) and at a higher mean arterial pressure (median, 30 mm Hg; range, 24-36 mm Hg; P = .003) and pulse pressure (median, 13 mm Hg; range, 0-24 mm Hg; P = .006). Among patients with both transcranial Doppler and electroencephalography data, brain activity generally stopped after brain blood flow but before circulatory arrest. These findings support current death determination guidelines, strengthening confidence in donor safety protocols and reinforcing public trust in organ donation.