It's not the same as a coma — and the distinction is what makes donation possible.
Brain death is the permanent and irreversible loss of all brain function, including the brainstem. Unlike a coma, where the brain is still active and potentially healing, a brain-dead patient has no electrical activity or consciousness. We determine this state only after rigorous testing confirms that the brain will never function again.
Two independent doctors perform standardized clinical exams to confirm the diagnosis. They check for reflexes like pupil response to light, blinking, and the ability to trigger a breath. If the brain does not respond to these physical stimuli, it indicates that the brainstem is no longer sending signals to the rest of the body.
Sometimes doctors use extra tests to be absolutely certain. An apnea test checks if the patient can take a breath on their own when removed from a ventilator for a brief period. We may also use imaging, such as a cerebral blood flow study, to prove that no blood is circulating to the brain.
A patient declared brain dead is legally and medically considered deceased. Because the heart and lungs can be kept moving temporarily with mechanical support and medication, this state allows for the possibility of organ donation. This is why the process of declaration is so formal, transparent, and strictly regulated by law.