02.05 Brain Death v. Comatose

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This is a topic that both Jon and myself are very passionate about. It’s something that is NOT taught well in nursing school and creates some tense, stressful times in the clinical setting if you don’t really understand this. That is the difference between a patient who is Comatose and one who is Brain Dead. The media and Hollywood throw around the term “Brain Dead” very liberally and it creates misunderstandings in family members. So we want to help you understand this, and be able to help patients’ families through this difficult situation.

So remember from the levels of consciousness lesson that Comatose is a description of a level of consciousness where the patient is unresponsive. However, comatose patients will continue to have blood flow to the brain and some brain activity. You can see this is a cerebral angiogram and you can see all the arteries coming up past the brainstem and spreading throughout the brain. You can be comatose, or even in a persistent vegetative state, and still have flow and NOT be brain dead. Brain death, on the other hand is an actual clinical diagnosis. It indicates that the patient has an absence of all brainstem reflexes. What do we mean by that? Well the brainstem is responsible for all of the most basic functions of life - breathing, digestion, cough/gag/corneal reflexes, etc. Someone who is brain dead will have ZERO reflexes present. We will also see an absence of blood flow to the brain and a complete lack of brain wave activity. If you were doing this angiogram on a brain dead patient, it would be completely black - it’s kind of eerie.

There are a number of ways we diagnose brain death - one is with apnea testing. Remember we said that the brainstem controls breathing, right? So if they have no brainstem activity, they will not be able to initiate breaths at all. Normally when our CO2 levels rise, our brain signals for us to breathe - it is involuntary. So to test this, we will stabilize their vital signs and get their CO2 to a normal level (between 35 and 45). We will also hyperoxygenate them beforehand. Then, we will disconnect the ventilator for up to 10 minutes. If at any point they show ANY indication of respiratory effort (chest wall movement, gasping, etc.) or if they become hemodynamically unstable, we abort and put them back on the vent. But, if not, once 10 minutes passes, we quickly draw a blood gas, then put them back on the ventilator. If their CO2 has risen to over 60 mmHg, that is considered confirmation of brain death. Again, in a normal person a CO2 that high would have caused them to breathe. We will typically not even go to apnea testing until all other non-invasive tests have shown brain death - they should have NO response to pain and NO reflexes. No cough, gag, corneal, not even a babinski. Their doll’s eyes reflex will be positive - meaning their eyes turn with their head as if they were painted on. Then, finally we can use cerebral blood flow studies. These studies can be very eerie - if you remember what it looked like to have flow throughout the brain…..**click** this is what a nuclear scan looks like in someone who is brain dead. There is ZERO flow past the brain stem. This is also considered confirmatory for brain death.

Now, this is where it gets difficult. According to the National Institutes of Health - “Brain death is defined as the irreversible loss of all functions of the brain, including the brainstem. ... A patient determined to be brain dead is legally and clinically dead.” It’s just as final as cardiac death. At this point we are supposed to disconnect the ventilator and remove all forms of life support. Patients’ families find this difficult to understand because we have them on the ventilator - so as far as they can tell the patient is still breathing and their heart is still beating. But remember that the heart is electrically independent from the brain, so it will continue to beat as long as it is effectively oxygenated and doesn’t experience damage. We have about 24 hours before circulating toxins from the rest of the body shutting down begin to affect the heart. That is the time-frame in which we look to organ donation.

So just remember that brain death is considered legal and clinical death, just like cardiac death. It means there is no blood flow, no reflexes, and no brain activity. This is a very difficult thing for families to understand because of the common misunderstandings and misuse of the term brain dead. These patients are ideal candidates to be organ donors if their family consents, BUT - HUGE note here - you should NEVER approach a family about organ donation. If you have a patient who may be brain dead, contact your local Organ PRocurement Organization - they will take care of those details - YOU just take care of the patient and their family.

We hope this has helped you understand the reality of brain death. Coming from an ICU background, especially in the Neuro ICU, Jon and I have seen this dozens of times between the two of us. One of those stories will be represented in the Case Study in the Cerebral Perfusion Pressure lesson, so make sure you check it out! It’s so important that we can help families through this difficult time by giving them the right information! Now, go out and be THAT nurse. We love you guys! Happy nursing!
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