Characterizing the physiology of circulatory arrest in humans.

The dying process from circulatory arrest is an underexplored domain in humans and has transdisciplinary pertinence. Here we conducted a prospective, observational cohort study of the dying process in 39 adults, with a multimodal assessment of cerebrovascular and cardiovascular physiology. We found that cerebral blood velocities and brain tissue oxygen tensions ceased before systemic hemodynamics. The brain exhibited diffusion limitation of oxygen extraction during the dying process compared with extracranial tissues. Anterior and posterior brain circulations had differences in timing of cessation of circulation and physiologic responses during the dying process. Blood-based neurologic biomarkers from the brain did not change during the associated ischemia related to the dying process. Heart pathology was associated with the length of the dying process. This study provides proof-of-concept of an in vivo human model to comprehensively investigate severe cerebral ischemia and the human dying process. ClinicalTrials.gov registration: NCT06130033 .