Some of the greatest EMS bloggers are doing series lately on what they think is most important in their rig, what medications they think are the most beneficial, etc. I’ve decided to focus on a series as well. Of the list I wrote yesterday, I will each day pick what I want most and work downwards to what I want, but can live without. My views aren’t necessarily reflective on what might be most useful or do the most overall good. My countdown will simply focus on what I want the most. That being said, I will give reasons as to why I believe my wants are important.
#1: Therapeutic (Induced) Hypothermia post-ROSC
First, I will provide a brief background on Hypothermia Therapy. Secondly, I will move into the use of Hypothermia in EMS. Third, I will focus on success – why is this most important to me?
Part I: Background
I have been a proponent of Hypothermia Therapy for a while. It sounds almost medieval: make someone very cold to ultimately keep them alive longer. Sounds like one of those medical myths that we end up thinking 30 years later: “Why in the world did we do that?!” However, while this therapy is fairly new to the United States, it has been successfully performed all across the world for decades. It’s success is not deniable. I have had the honor of meeting someone who went into cardiac arrest (ventricular fibrillation) with a still-unknown position at the age of 39, received prompt aeromedical hypothermia treatment en route to a major trauma center on the east coast, and woke up five days later fully alert and oriented. He is now 41 years old and a flight paramedic. Hard to argue with that.
Hypothermia Therapy is used for many different reasons – traumatic brain injury, prolonged high fever, as an adjunct to anesthesia in some surgeries, or as this entry will examine, as a neuroprotective aid after return of spontaneous circulation (ROSC) post-cardiac arrest.1 Protocols are different, and I’ll examine them more later. I will describe the therapy now using the protocol employed by Inova Fairfax Hospital in Virginia. Their indications for use include: age 18 or older, survived cardiac arrest with eight hours previous, significant alteration in neurological function (comatose but not brain dead), systolic blood pressure equal to or above 90 mmHg, and mechanical ventilation. Contraindications: irreversible neurological damage, platelet count less than 75,000 mm3, pregnancy, and terminal illness.2
Once patients meet the indications, they are pre-treated with 1 gram of magnesium in 100 mL normal saline over the course of one hour to decrease shivering (since shivering attempts to rewarm the body). The patient’s face, hands, and feet are counter-warmed, perhaps using a Bear Hugger blanket. They are administered 25-50 mg Demerol IV. Finally, they are given 2 liters of cold normal saline over 30 minutes. The goal is to cool to 33.5 degrees C as quickly as possible, preferably within two hours.
During the entire hypothermia process, patient’s vital signs and chemistries are monitored constantly. Blood pressure, heart rate, temperature, SpO2, and output are constantly assessed. Every eight hours, laboratory studies are taken– a full chemistry (K, Mg, Phosphate, ionized calcium), CBC, Coagulation, Lactate, and Troponin. Continuous sedatives, analgestics, and paralytics are administered. The patient receives no heat from the ventilator, insulin on a drip, DVT prophylaxis, GI prophylaxis, and no electrolyte replacement for eight hours before rewarming.
When it is time to rewarm, Acetaminophen is given before and every six hours after warming (to prevent overshoot). Rewarming is accomplished in incriments of 0.5 degrees C per hour up until the target of 37 degrees C (about 6 to 8 hours). At 36 degrees, paralytics are discontinued, and at 37 degrees, sedation is attempted to be removed. To prevent overshoot into rebound hyperthermia, the Arctic Sun counter-rewarming is set up for at least 24 hours.
Initiating this therapy has lead 57% of patients receiving this therapy at this hospital facility to have good neurologic outcome. According to a New England Journal of Medicine study in 2002, 55% of patients in induced hypothermia have a good neurological outcome as compared to 39% of patients without the therapy.3
This therapy comes highly recommended. The Advanced Life Support Task Force of the International Liaison Committee on Resuscitation in conjunction with the American Heart Association Science Advisory and Coordinating Committee recommended in 2002 that “unconscious adult patients with spontaneous circulation after out-of-hospital cardiac arrest should be cooled to 32 degrees C to 34 degrees C for 12 to 24 hours when the initial rhythm was ventricular fibrillation. Such cooling may also be beneficial for other rhythms or in-hospital cardiac arrest.”4 ACLS guidelines hold the same criteria as a level IIA recommendation – or otherwise, highly recommended.
But what does therapeutic hypothermia do?
Primarily, it affects brain injury and reperfusion response. It is the only post-arrest therapy that has proven itself to increase survival rates post-ROSC. Brain injury is the cause of death in 68% of out-of-hospital cardiac arrest compounded by the brain’s limited tolerance of ischemia. The therapy can reduce intercranial pressure, reduce heart rate, and reduce demand in the brain for oxygen.5 All of those things can leave a patient with increased neurological function upon re-waking after their hypothermia-induced stupor – or simply put, these patients will not end up as an ICU vegetable, but have a higher chance of going home with the same neurological function as they had prior to arrest.
Part II: Hypothermia Therapy in EMS
Looking at the criteria I described above in Part I, the therapy is obviously complicated and carefully monitered. How would we as field providers be able to know if someone is pregnant? We certainly can’t perform a platelet count. How would we keep the saline regulated to an exact temperature? Counter-rewarming? The questions are endless.
But several agencies across the country have found ways to at least initiate therapy. Wake County EMS in North Carolina was a pioneer in this therapy. If their patients meet a select few criteria: ROSC not due to blunt/penetrating trauma, age 12 or older, temperature greater than 34 degrees C after ROSC, and an advanced airway in place, Hypothermia Therapy can be considered. See their algorithm below for a detailed process of how and when the therapy is initiated and maintained.6
Wake County EMS then monitors Mean Arterial Pressure (MAP) using the Lifepack 12 to keep it between 90 and 100. If MAP is not naturally between this range, Dopamine is used as a pressor.
Another progressive area, North Central Connecticut EMS Council, also utilizes the hypothermia protocol in their post-resuscitation care. Their protocols, dated June 2009, require a patient to have ROSC post-arrest not related to trauma or hemorrhage, be older than 18 years old, have no obvious gravid uterus, no signs of initial hypothermia, no purposeful response to pain, and be intubated. After meeting these criteria, they have an algorithm quite similar to Wake County’s. See below for their algorithm—7
Is this therapy used? Yes, it’s expected. It’s an ACLS algorithm in these protocols. Just as a provider would treat ventricular fibrillation or pulseless electrical activity with a certain protocol, this is an expected part of treatment for patients meeting the criteria.
In an e-mail message on March 6, 2010, I discussed this therapy with a career paramedic in one of these councils that utilizes induced hypothermia on a regular basis. He informed me that he had in fact used the therapy three times that day, but all the patients all ended up passing away in the ICU. The therapy is not foolproof, but side affects are fairly limited as compared to the potentials.
EMS worldwide, particularly in Australia, also uses induced hypothermia – although hospitals in many areas outside of the United States are quite fewer and far between than we are accustomed to here.
Part III: Why #1?
Well, as I stated, the side affects are few compared to the possible outcome. The science is proven by AHA, New England Journal of Medicine, and countless other studies and agencies.
The therapy isn’t expensive. The main proponents are cold saline and some additional medications. No fancy equipment or maintenance cost. No expensive training. And it truly changes people’s lives. To be able to be in cardiac arrest, and several days later, have the possibility of leaving the hospital with normal neurological function shows what strides in medicine that we are making.
Would it be used routinely? Depends on how many cardiac arrests your area gets. It has the potential for wide use.
The downside is that only 27% of hospitals in the United States are using this therapy now.8 Obviously, a provider cannot initiate something that the hospital can’t finish. There are no hospitals within 60 miles from my primary agency that has this therapy, so wishing for this as my number one is moot at this point. The closest center is in my state’s capital at a major trauma center.
My solution: fly out. If I had a patient meeting the major criteria, I wouldn’t hesitate to call aeromedical to fly my patient down to a hospital that does support this therapy. The therapy is not something that can be postponed to get evaluated at another hospital, then transport considered, etc. It needs to happen quickly.
My protocols state: “The use of helicopter […] may be considered in situations where the use of the helicopter would speed a patient’s arrival to a hospital capable of providing definitive care and that is felt to be significant to the patient’s condition.”9 Sounds good to me – I think I could probably get away with flying out a patient post-cardiac arrest if I feel he would benefit from and receive this therapy. I would certainly call a patient walking away with neurological function in tact “providing definitive care.”
In the words of Peter Safar – “We need to treat brains that are too good to die.”
1. Mosby’s Dictionary of Medicine, Nursing, and Health Professions, 2009, pg 924.
2. Linda Schakenbach, presentation – “Cool Therapy”, February 2010.
3. Ibid.
4. J. P Nolan et al, “Therapeutic Hypothermia After Cardiac Arrest,” Circulation 108, (2003): 108-121.
5. Nancy Diepenbrock, Quick Reference to Critical Care, (Philadelphia: Wolters Kluwer Health, 2008),191.
6. http://wakeems.com/ICE2008/index.html
7. http://www.northcentralctems.org/Online_Forms.htm
8. Linda Schakenbach, presentation – “Cool Therapy”, February 2010.
9. Rappahannock EMS Council Pre-Hospital Patient Care Protocols, 19.
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