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Brain & Nervous System Health Center

What 'Brain-Dead' Means

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Brain-stem reflexes are often the last to go, he says. These reflexes include the dilation of pupils when someone shines a light in the eyes and coughing or gagging when the vocal chords are tickled. 

When there’s no evidence of higher brain function or brain-stem reflexes, and when other factors that could mimic brain death, such as drugs or low blood pressure, have been ruled out, “that’s when we’ll approach the family” and explain the need for a formal brain-death evaluation, Tawil says.

Q. How do doctors determine that a patient is brain-dead?

A. A formal brain-death evaluation takes about 20 minutes, Tawil says. 

First, the doctor will check to see if the patient flinches in response to something that can cause pain, like pinching the skin. Next, the doctor will make sure that there are no brain stem reflexes. Finally, the doctor will disconnect the patient from the respirator and check to see whether rising carbon dioxide levels in the blood stimulate the brain. If none of these three findings is present, a second doctor is called to confirm brain death, Tawil says.

(At its annual meeting in 2013, the European Society of Anaesthesiology called for an international agreement on the criteria for determining brain death, such as the number of doctors needed to agree on the diagnosis, and how many and which reflexes need to be examined.)

Q. Why continue mechanical support of a patient who’s brain-dead?

A. When doctors pronounce brain death, they’ve got to be clear to the patient’s loved ones that such support is going to stop, Caplan says. Mechanical support might continue for a short period to give out-of-town relatives time to get to the hospital to say goodbye, he says.  

If the family agrees to donate the patient’s organs, though, mechanical support might be needed to keep the organs usable until they’re removed.

Q. Can a person who's been declared brain-dead be revived?

A. No. Brain death is death, plain and simple.

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