Brain Death Criteria and Deceased Organ Donation: A Comparative Review of Legal Standards and Clinical Practice

Abstract

Brain death, increasingly referred to as death by neurologic criteria, is an established medical and legal determination of death in many jurisdictions and is particularly relevant to deceased organ donation. Despite broad agreement on the essential clinical features, including permanent unconsciousness, absence of brainstem reflexes, and absence of spontaneous breathing, considerable variation exists in legal definitions, diagnostic prerequisites, examiner qualifications, apnea-testing procedures, observation periods, and ancillary investigations. This narrative review compares contemporary clinical and legal standards for brain-death determination and examines their implications for deceased organ donation, focusing on the United States, United Kingdom, Canada, India, and Australia/New Zealand. Relevant peer-reviewed literature, international consensus statements, professional guidelines, and statutory documents published between 1968 and September 2026 were reviewed, with particular attention to major international and national guidelines. Contemporary standards consistently require an established catastrophic brain injury, exclusion of reversible confounding factors, demonstration of unresponsiveness and absent brainstem reflexes, and formal assessment of apnea. However, important jurisdictional differences persist. The United States predominantly applies a whole-brain legal formulation, whereas the United Kingdom follows a brainstem-based clinical approach. Canada has adopted a unified brain-based definition of death, while India legally recognizes brainstem death within its transplantation framework. Additional differences concern repeat examinations, examiner requirements, and the indications for ancillary testing. These variations may affect diagnostic consistency, clinical training, family communication, and deceased organ donation practices. Greater international harmonization of terminology, diagnostic prerequisites, clinical examination procedures, documentation, and ancillary-testing standards may improve consistency and public confidence. Nevertheless, harmonization must respect national legal frameworks, and determination of death must remain clinically and ethically independent of transplant eligibility and authorization for organ donation.