Merck Manual

Please confirm that you are not located inside the Russian Federation

Loading
Quick Facts

Brain Death

By

The Manual's Editorial Staff

Last full review/revision Apr 2019| Content last modified Apr 2019
Click here for the Professional Version
Get the full details
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version

What is brain death?

Brain death is when a person's brain has completely stopped working but the body is being kept alive by breathing machines and drugs.

  • People who are brain dead are unaware and can't think or feel

  • They can't move or breathe

  • Their brain stops controlling automatic body functions such as heartbeat and blood pressure

  • People don't recover, and the body dies within a few days no matter what doctors do

  • People with brain death are considered legally dead

Machines can breathe for someone who is brain dead, and medicines can keep the heart beating for a short time. However, eventually, all the person’s organs stop working. If a person wanted to be an organ donor, doctors may be able to use the person's organs for transplant. But the organ donation has to be done before the organs stop working.

No one who's brain dead ever recovers. Brain death is different from coma. People in a coma have some brain function and sometimes recover.

What causes brain death?

Brain death is caused by severe brain damage from:

Such problems typically cause brain swelling. The brain swelling raises the pressure inside the person's head. That increased pressure eventually shuts off all blood flow to the brain. Once blood flow has been shut off, brain death occurs.

How can doctors tell if someone is brain dead?

Doctors first make sure the person doesn't have a medical problem that causes a deep coma similar to brain death. Such problems include:

  • Overdose of certain kinds of drugs

  • An extremely low body temperature (hypothermia)

If the person doesn't have one of those problems, doctors do a physical exam to look for signs of brain activity including:

  • Trying to breathe if the ventilator is turned off

  • Flinching or moving if the person is pinched or poked by a needle

  • Gagging on something put in the back of the throat

  • Blinking if something touches an eyeball

  • Pupils narrowing in response to a flashlight

If there's no sign of brain activity, doctors sometimes test again 6 to 24 hours later to make sure the person again shows no response. After testing twice with no response, doctors know that the person is brain dead.

Instead of waiting a day to repeat the examination, doctors may do:

  • Brainwave tests (EEG) to see if the brain has any electrical activity

  • Blood flow tests to see if any blood is getting to the brain

People with no electrical activity or blood flow in the brain have brain death. But these tests aren't required.

What do doctors do if someone is brain dead?

Because brain death means someone is legally dead, the person's organs can be donated to someone in need of an organ transplant. Donation doesn't have to wait for the person's heart to stop beating. Organs are taken only if the person or family wishes to donate them. The ventilator and supportive medicines are kept going until this is done. The organs are removed carefully, and the body is treated with great respect. Then doctors:

  • Turn off the ventilator

  • Stop any medicines

  • Release the body to the coroner's office or the funeral home

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest

Videos

View All
Spinal Tap (Lumbar Puncture)
Video
Spinal Tap (Lumbar Puncture)
The spinal cord is a bundle of nerves that run from the base of the brain all the way down...
3D Models
View All
Spinal Column and Spinal Cord
3D Model
Spinal Column and Spinal Cord

SOCIAL MEDIA

TOP