Therapeutic hypothermia technique is a new treatment trauma surgeons have begun using on patients with uncontrollable blood loss. By drastically lowering the patient’s body temperature, the risk of brain damage following a period of massive blood loss resulting in cardiac arrest is greatly reduced. When a heart stops beating, oxygen does not sufficiently move to the brain. If revival occurs at normal body temperature (98.6° F) oxygen molecules form free radicals, which can cause damage and death to brain cells. Therapeutic hypothermia prevents this brain damage. Ice-cold fluids are flushed into the inferior vena cava, which spreads through the heart, brain, and rest of the body. The result is a large, but slow, drop in core temperature. Therapeutic hypothermia causes metabolic rates of the brain and heart to dramatically decrease, so less oxygen is necessary. When the patient is revived, their core temperature is gradually increased. The brain cells, having needed less oxygen, are able to withstand the reintroduction of oxygen molecules after resuscitation.
Studies have shown that induced hypothermia doubles the chances of survival in individuals with life-threatening traumatic injuries. With such promising results, as many as a quarter to a third of hospitals have added therapeutic hypothermia to their treatments for cardiac arrest.
There are, of course, risks associated with the treatment. Hypothermia inhibits blood clotting and may cause destruction to tissues.
The other complications of therapeutic hypothermia are ethical. Bioethicists are concerned because patient consent for those needing therapeutic hypothermia would be extremely difficult to attain, as a person bleeding to death is likely going to be unable to agree to the procedure. Instead, the research team, in collaboration with the FDA, will place signs, host informational meetings, and advertise online campaigns to inform residents in the area of the treatment. Residents worried about potential risks will be able to sign a list “opting out” in the case they were ever a potential candidate. Bioethicists, however, still worry that the “informed community” model cannot effectively cover the hazards.
Regardless of the possible risks, therapeutic hypothermia is becoming a mainstream treatment. In Colorado, it is protocol in Colorado Springs at Memorial Health. Is therapeutic hypothermia beneficial? Ethical? Or is it simply the “cool” new treatment?
References:
Clumpner M, Mobley J. Raising the dead: Prehospital hypothermia for cardiac arrest patients may improve neurological outcome and survival to discharge. EMS 37(9): 52-60, Sep 2008.
Holzer, Michael. “Mild Hypothermia to Improve the Neurologic Outcome After Cardiac Arrest.” New England Journal of Medicine. (2002) Vol. 346, No. 8.
Neergaard, Lauren. (14 November 2011). Hypothermia to save lives? Doctors to try deep-chilling trauma patients. Retrieved from: http://www.huffingtonpost.com/2011/11/14/deep-chilling-trauma-patients_n_1093546.html?ref=healthy-living-health-news
I thought your blog post was very interesting more so because it is of immediate concern in my field of EMS in pre-hospital treatment of cardiac arrest. In an instance of a cardiac arrest in the out-of-hospital setting where paramedics are needed to defibrillate, issue chest compressions, ventilate and deliver advanced pharmacological support, most of the patients who exhibit return of circulation following EMS resuscitation still remain unconscious in the field. By the time a patient had arrived at the hospital and a decision has been made to begin therapeutic hypothermia, the patient could have been “cooled” anywhere between 5 and 150 minutes prior (Kim et al., 2009) which could enhance their discharge with normal neurologic function by 39-55% (Kim et al., 2009).
ReplyDeleteIn a study that examined the safety, efficacy and feasibility of using rapid infusion of normal saline at 4 C by paramedics in the field following return of spontaneous circulation (ROSC), 63 of 125 patients who suffered from cardiac arrest from VF, asystole or PEA received rapid infusion of up to 2 liters of cold normal saline. In-field cooling did not show direct association with complications in HR, BP, arterial oxygenation or re-arrest and did show potential benefit for in-field cooling for VF patients (PEA and asystole patients did not show statistically relevant improvements). (Kim et al., 2009). Research also suggests benefit for during-arrest cooling of patients who are in the process of being resuscitated.
The research obviously shows a positive trend towards the initiation of therapeutic hypothermia both in the hospital as well as the pre-hospital setting. Few EMS agencies have adopted the protocol however, because of issues with the receiving hospitals in their area, all of which need to be able to continue therapeutically induced hypothermia protocols, once initiated. It has also been in debate that therapeutic hypothermia is expensive for EMS agencies if refrigeration units were needed in each ALS ambulance. The ethical issue, like you stated, is also of concern. Especially if a patient is picked up in the field with absolutely no medical history and/or access to a family member for consent.
Kim, F., Olsufka, M., Nichol, G., Copass, M., Cobb, L. (2009). The Use of Pre-Hospital Mild Hypothermia after Resuscitation from Out-of-Hospital Cardiac Arrest. The Journal of Neurotrauma, 26(3): 359-363. Retreived from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2741140/?tool=pubmed on November 27, 2011.
This article definitely caught my eye because I was finding many of the same studies and results when I posted my article on liquid breathing. You mention that the physicians use “ice-cold fluids” to induce the hypothermic state (these fluids are at -15oC!!). Well, in a little bit of shameless advertising, my liquid breathing article is directly correlated to these ice-cold fluids! Perfluorocarbons have been used to create this hypothermic state while still providing enough oxygen for the basic metabolism necessities (Staffey et al., 2008).
ReplyDeleteStaffey et al predicted that because external hypothermia was useful in improving odds of resuscitation, intrapulmonary hypothermia, and thereby direct contact with the tissues surrounding the heart, would produce the same results and better (2008). And in agreement with what you are mentioning, there was an 82% success rate for resuscitation using the cold perflurocarbons. One benefit to doing targeted hypothermia in this way is that it doesn’t put the rest of the body in a hypothermic state. Another advantage to doing targeted hypothermia via the pulmonary bed is it doesn’t take nearly as long to bring down the core body temperature to the hypothermic state (Staffey et al., 2008). This external cooling wastes valuable time that the cardiac arrest patient might not have. However, I’m not sure if the lack of systemic hypothermia would cause a problem with the free radical formation, and that most likely still being researched.
My opinion to your first question is that yes, from what I’ve seen, therapeutic hypothermia is definitely a beneficial treatment. The resuscitation rates are much higher (by 55%!!) and the free radical issue is taken care of.
Staffey, K.S., Dendi, R., Brooks, L.A., Pretorius, A.M., Ackermann, L.W., Zamba, K.D., Dickson, E., & Kerber, R.E. (2008). Liquid ventilation with perfluorocarbons facilitates resumption of spontaneous circulation in a swine cardiac arrest model. Resuscitation,78, 77-84. Doi: 10.1016/j.resuscitation.2008.02.008
I am curious about the negative effects that this could have. If the induced hypothermia can inhibit blood clotting, isn't there a concern for coagulation? And wouldn't the body try and warm itself up again? Do you know of any of the drugs that they administer during the induced hypothermia to counteract the body from shivering and such?
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