Cardiac Arrest: Medically Induced Hypothermia to Spare Brain Tissue
Guest: Dr. Ed Jauch – Emergency Medicine, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing Dr. Ed Jauch, who is a physician in the Emergency Department. Dr. Jauch, we have a really interesting topic to talk about that I, frankly, know nothing about; it’s very new, which is the use of hypothermia for the treatment of patients who’ve had CPR, or defibrillation. First, I guess, just to think about those terms, what, exactly, is hypothermia?
Dr. Ed Jauch: Well, there are two forms of hypothermia. There’s the form that we’re at risk for now; given the cold weather, where your body’s ability to generate heat is outpaced by how much it loses. So, that’s more the environmental form of hypothermia. They type that we’re talking about today is the medicinal form, or medically-induced hypothermia. This is where we deliberately cause the body’s core temperature to drop to a fixed point in an effort to blunt the injuries to the brain that are experienced when the body doesn’t give enough blood to it.
Dr. Linda Austin: Give us some background on this. Why would that be a concern to begin with in a situation where a patient; a person, out in the community might have had CPR, or defibrillation?
Dr. Ed Jauch: Well, we’ve learned a lot just from observation. So, a lot of the early work stemmed from the observation that patients who had cardiac arrest in cold climates; or patients who had submersion events, like they ran their car off the road into the cold water, actually had a better chance for a functional outcome when their body temperatures were lower, compared to similar patients who had cardiac arrest in warm environments. So, there was something protective about those experiences in the cold weather that saved some parts of their brain, or all of their brain, after a cardiac arrest. It gave them better outcomes.
So, after animal studies, and observational studies in humans, we’ve actually seen several trials in the last four or five years that have demonstrated that patients who have deliberate cooling of their brain after they’ve had a cardiac arrest; and we’ve been able to shock them back or, as you said, defibrillate them back to a normal a cardiac rhythm, have better functional outcomes at discharge. They’re more likely to be admitted to the hospital versus dying in the field. They’re more likely to be discharged to home versus dying in the hospital. And they’re more likely to be discharged to home with a good functional recovery than if we didn’t induce hypothermia. So, this is where we’re deliberately cooling the brain down to a target temperature and keeping them that way for, roughly, about a day, and then gently rewarming them, and trying to improve the body’s ability to blunt the injuries to the brain after their cardiac arrest.
Dr. Linda Austin: How do you go about doing that?
Dr. Ed Jauch: Well, that’s a good question. So, we’re really looking at doing this as quickly as possible. That, really, means that we need to do it in the prehospital setting. So, in the prehospital setting, the goal is to have some form of cold agent available to the paramedics, and that consists of two here in Charleston. One is they’ll have ice packs, at 32 degrees, that they’ll be able to place on critical parts of the body. So, if you stick them in the axillary, or armpits, in the groin, and around the neck, those are areas where very large blood vessels are underneath the skin, and it’s a way for us to cool the blood. The other way is to actually give cold saline through the veins; IV. So, we have bags of normal saline, which is the fluid we give our patients in the prehospital setting, that have also been chilled to just above freezing. By delivering that directly into your blood, it’s a way to start the cooling process in the prehospital setting.
Dr. Linda Austin: Now, when you say prehospital, you mean somebody’s house, for example, where EMS has been called, or out on the golf course, or something like that?
Dr. Ed Jauch: Exactly. So, an example would be somebody, like you said, has a cardiac arrest on the golf course and the bystanders that witnessed this do the right things, which are to call 911 and begin CPR. And it, really, is the quality of CPR prior to the arrival of EMS agencies that really give the patient the best chance for having a successful defibrillation. So, knowing CPR is critical. Once the paramedics arrive and place the defibrillator on the patient, and find a rhythm that is amenable, or appropriate, to be shocked, if they’re able to shock the patient and get the heart back into a normal rhythm, then those are the patients that we consider for hypothermia.
They can start by giving the fluids in the prehospital setting, or in the back of the ambulance, or even on the golf course, at that point. And, during their transport to hospitals that have hypothermia protocols, they’ll continue to give a couple bags of the cold fluid. They’ll continue to place the ice on the critical parts of the body. So, once they’ve arrived in the emergency department, even with short transport times, say 10, 15 minutes, the cooling process has begun. And we continue that in the hospital until we’re able to get the temperature down to the desire target, and we keep them there for roughly a day. Then we allow them to gently rewarm.
Dr. Linda Austin: Are they conscious during that time?
Dr. Ed Jauch: No. So, there are different severities, if you will, of brain injury after cardiac arrest. Some patients, remarkably, can be shocked back to life, wake up, and say thank you. That’s not the norm. The majority of patients have experienced some form or neurologic injury; or temporary neurologic injury. Most of these patients that we see, and only those who are not conscious, are eligible for hypothermia. So, there are criteria as to whom we can give this therapy to. But you have to have a spontaneous rhythm; your heart has to be beating on its own. You have to be comatose. Otherwise, you wouldn’t like being cooled. It produces shivering and things like that. And, we do this only in adults right now. We don’t have enough information that this applicable to children. And, gratefully, we don’t see many cardiac arrests in children.
Dr. Linda Austin: Now, you mentioned, when you were describing this, that you start the cooling process after you’ve established a normal heart rhythm. If one were in a setting like, let’s say, a golf course, or a family barbeque, and somebody has a cardiac arrest; CPR has started and you’ve called 911, would it be a good thing to do to take bags of ice, if you happen to have them, and put them under their armpits, and on their neck, and around their head. Would that make sense?
Dr. Ed Jauch: That’s a great question. The problem with that is that the heart is fairly sensitive to hypothermia. So, our biggest problem in patients who have environmental hypothermia; say you’re left out in the cold too long, is that the heart is very sensitive to that and it develops arrhythmias. It actually develops abnormal heart beats when it gets too cold. So, the only reason why we induce hypothermia after the return of spontaneous circulation is that the heart has gone back to breathing at a normal rhythm and it’s continuing to do that. It’s harder to shock a cold heart back to life than it is a warm heart. So, we don’t want to do anything that makes that shocking process harder for the patient. So, the patients have to come back to a normal, what we call perfusing, rhythm, where the heart is beating on its own. It’s circulating the blood. Then, we consider the use of hypothermia.
Dr. Linda Austin: I see. Okay. So, don’t do the Linda Austin technique of ice bags? Okay.
Dr. Ed Jauch: Correct.
Dr. Linda Austin: Good. I heard a story on public radio, I think, the other day; I’m sure you did too, where a woman fell in the snow and was found after several hours with a core body temperature of 70 degrees, and was revived. Of course, they did that very slowly and gradually, and with a great deal of support in the emergency room.
Dr. Ed Jauch: Yes. Those are very challenging cases. Again, there are a lot of problems that can occur with that; kidney failure. But probably the biggest problem is that the heart is extremely irritable when it gets even below 90 degrees. So, even moving the patient can produce a fatal arrhythmia, or a fatal heart rate. So, they’re very difficult and challenging patients and, luckily, something we don’t see too frequently here in Charleston.
Dr. Linda Austin: Dr. Jauch, thank you so much.
Dr. Ed Jauch: My pleasure.
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