When the brain goes, what goes next?

April 3, 2010 3:30 PM

If the brain goes first, in what order would a person's organs fail? What would be last?

Suppose brain function is immediately terminated (or cut off from the rest of the body, I guess). In what order would organs or systems fail, which would be last, and how long would it take?

posted by snorkels to Health & Fitness (11 answers total)

Given that your heart kind on counts on the brain to tell what to beat so it's arguable first. Most of the other active function type organs won't really be doing their thing if blood flow stops, so once could argue that a lot of systems would cease to function immediately.

This is one of those things where the exact definition you use for "fail" will strongly effect the answer.
posted by Kid Charlemagne at 3:42 PM on April 3, 2010

Most often the heart can continue on its own. Occasionally, interruption of the spinal cord in injury leads to arrhythmia but not too often, lack of brain is essentially the equivalent of a spinal cord injury in terms of cardiac function. Given this, respiration would fail. The lack of oxygen would result in myocardial death and eventually cessation of heart function (think around 10-15 minutes). The lack of blood flow and oxygen transport then would lead to death of other organs, beginning with the lungs. Next probably would be intestines. Liver and kidney are more resilient and in donation after cardiac death are still viable for up to an hour. The last organ to die would probably be skin, taking several hours. The cause of failure in all cases would be the lack of oxygen which is why brain dead individuals can be kept alive with artificial respiration (except in some cases where cardiac pacing is needed).
posted by Brennus at 3:54 PM on April 3, 2010 [1 favorite]

Failure isn't all-or-nothing. For most of your body it's a more gradual process. To create an order you need a specific defined time when failure happens for any given organ, and there isn't one.

Given that your heart kind on counts on the brain to tell what to beat...

Sorry, not correct. There's an oscillator local to the heart that does that. That's why people who are braindead don't automatically suffer from heart failure. When the brain wants to affect heart function it uses hormones (e.g. adrenaline).
posted by Chocolate Pickle at 3:56 PM on April 3, 2010

Given that your heart kind on counts on the brain to tell what to beat so it's arguable first.

The heart has its own pacemaker, the sinoatrial node. It takes some input from the brainstem through the vagal and other nerves but really in most cases can beat without brain input. In heart transplants the heart is actually not innervated at all and recipients do just fine most of the time.
posted by Brennus at 3:57 PM on April 3, 2010 [1 favorite]

"The brain" doesn't go. There are a shitload of different parts of the brain, and their connections to different organs are also varied. A better question might be: if you severed the spinal cord, in what order would the tissue inside various organs die? However, because all organs work on different time scales, it's really difficult to say in which order they "fail."
posted by solipsophistocracy at 4:10 PM on April 3, 2010

If we take the case of the severed spinal cord as your definition of the brain "going," (ie no activity at the brainstem and above), the lungs go first. No spinal cord means no spontaneous breathing. Lungs go, oxygen levels go doen, CO2 levels go up, pH goes down, heat develops fatal arrhythmia and stops.
posted by drpynchon at 4:41 PM on April 3, 2010 [1 favorite]

That's heart not heat.
posted by drpynchon at 4:42 PM on April 3, 2010

Now that I think of it, I guess technically the musculoskeletal system (if you think of it as an organ) "goes" even before the lungs as that is what is needed to continue respiration.
posted by drpynchon at 5:04 PM on April 3, 2010

It also really depends on how the brain "goes." If by large caliber, supersonic, hollow point handgun bullet, or shotgun slug, which expands rapidly on its trajectory from the throat to the top of the head, blowing the majority of the brain matter and 2/3 of the skull all over the place, the heart may continue pumping effectively enough to substantially exsanguinate the body within a couple of minutes through the remnants of the head, greatly accelerating organ death through secondary massive blood loss.
posted by paulsc at 5:59 PM on April 3, 2010

Note that there is a difference between 'fail' and 'die'. To say an organ fails is only to say that it ceases to perform its function. In some organs this is easier to distinguish than in others, i.e. you can easily measure cardiac output, and everyone agrees that cardiac output is what the heart is all about, but how would we say that our braindead patient's stomach has 'failed' given that they are not going to be eating anything anytime soon?

Really though the most important part of the brain in terms of short-term survival is the brainstem, which contains the centres for automatic respiratory control. This is what keeps you breathing when you're not thinking about it. If you cut off the brain completely, you'll stop breathing immediately. Then it's just a matter of what's going to starve to death from hypoxia first.

So your lungs are going to fail first, followed quickly by your heart. Because these two organs are the big ones in terms of short survival, can you say really talk about the rest of the body - liver, pancreas, stomach, intestines, kidneys, spleen, skin, bones, etc. - in terms of 'failure'? No, not really.
posted by schmichael at 7:48 PM on April 3, 2010

Yeah, echoing Schmichael. Assuming the hindbrain goes, it'll be the lungs first, followed in short order by the heart and the rest of the brain. The heart and brain are the two organs most sensitive to a loss in oxygen, because they're the most metabolically-intensive parts of the body. They can't survive more than a few minutes without a steady supply of oxygen.
posted by dephlogisticated at 9:36 PM on April 3, 2010