How does one wake up after induced coma after cardiac arrest?

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How long time does it take for person to fully wake up if brain was not extremely damaged? How soon after stopping medication is known if brain damage is not compatible with life? How does death in case of big brain damage happen?

In: Biology

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After an MI, the patient is cooled down to a lower body temp for 24 hours. Then the rewarming process takes another 12 to 24 hours. During this time, the patient is usually heavy sedated, and heavy sedation can sometimes alter the results of our neurological assessments. This “heavy sedation” is the induced coma. We still try to assess neurological function, but we take into consideration that the medicines could be changing the way the person responds. Once the body is warmed back up to a normal temp, the sedation is weaned off and then the “real” neuro assessments starts. We look for equal, round pupils that are reactive to light; gag and pain reflexes; and eventually the ability to follow basic commands (thumbs up, wiggle your toes) with equal movement and strength on both sides of the body. If any of these are abnormal, it can indicate a brain injury, and we will do a CT scan of the head to look for damage.

If there is brain damage, it can appear anywhere from immediately to a few days, depending on the severity. In a cardiac arrest, typically the brain damage is from a lack of oxygen so those changes can be seen on a CT scan within 12 to 24 hours. These changes can be seen whether patient being sedated or not. Brain damage by itself will not necessarily kill you. The “consciousness” could be gone but their reflexes could be intact. In that case, we withdraw life-sustaining measures and let the person pass naturally. This usually means removing the ventilator, and any devices that are helping the heart pump. If the heart is severely damaged, it will eventually slow down and stop beating on its own. The heart “dies” because it needs a lot of oxygen itself and it is too weak to pump as long and as strong as it used to.

If the heart is only minimally damaged but the brain is severely damaged (not very common), that’s an entirely different story. That’s where you end up with patients in long-term care with various levels of coma and vegetative states.

Edit: typos