Emergency physicians in 3 different cities encounter 3 distinct patients with 1 thing in common: a low core body temperature.
Minneapolis, Minnesota: On a cold winter day, an emergency physician receives a call from EMS asking for advice: They were called to a nearby park where an unidentified middle-aged woman was found on the ground near a park bench. She has no palpable pulse, and there is an unknown downtime. On exam, her pupils are fixed and dilated, and her body feels cold to the touch. The paramedic is concerned that any resuscitation efforts would be futile and asks if any interventions should be made.
Portland, Oregon: A 22-year-old woman is brought to the ED after being rescued from a hiking expedition gone awry. The rescue team reports that she was lost on a mountain overnight without proper equipment or clothing. She was found lethargic, bradycardic, and hypotensive, but pulses were present. When she arrives in the ED, her condition is unchanged. You wonder what the best rewarming strategy would be.
Phoenix, Arizona: An 82-year-old man with multiple medical problems is transported to the ED from his nursing home due to altered mental status. Initial vital signs show that he is tachycardic, hypotensive, and has a rectal temperature of 33°C. There is no history of known cold exposure, and nursing home staff assures the doctor that he has been in bed for days with plenty of blankets. What is the differential diagnosis, and how should this patient be treated?
Accidental hypothermia is defined as the unintentional drop in core body temperature below 35°C (95°F).1 While accidental hypothermia is most common in cool climates during winter months, it can also occur in warm climates, in any season, and in individuals without a history of outdoor exposure. Accidental hypothermia can occur in a variety of populations, including those in an urban environment. Those at highest risk include homeless individuals, the very young and very old, and individuals with psychiatric disease, serious underlying medical conditions, traumatic injuries, or drug or alcohol intoxication.2,3 These groups often have impaired thermoregulation, but they also lack the ability to perform the behavioral adaptations to protect themselves from the cold, such as seeking shelter and putting on extra clothing.
The United States Centers for Disease Control and Prevention (CDC) reported that in the United States during the years of 1999 to 2011, there were an average of 1301 deaths from environmental cold exposure per year.4 Approximately half of the deaths attributed to hypothermia occur in patients over the age of 65. Inhospital mortality of patients with moderate or severe hypothermia is as high as 40%.3 Despite the high mortality rate, there have been survivors with good neurologic outcomes who were resuscitated from extremely low temperatures, the lowest of which was 13.7°C.5 There have also been case reports of individuals surviving neurologically intact after prolonged cardiac arrest, the longest being in cardiac arrest for 8 hours and 40 minutes.6
In this issue of Emergency Medicine Practice, we will review the definition, pathophysiology, differential diagnosis, prehospital management, and emergency department (ED) evaluation and management of patients presenting with accidental hypothermia.
Searches of numerous evidence-based medicine sources were performed, including PubMed, MEDLINE®, Cochrane Database of Systemic Reviews, Database of Abstracts of Reviews of Effectiveness (DARE), and the National Guideline Clearinghouse, using the key terms accidental hypothermia and accidental hypothermic arrest. A systematic review published in 2014 describing the use of extracorporeal-assisted rewarming in the management of accidental deep hypothermic cardiac arrest was the sole review that met criteria for inclusion on DARE.7
Several sets of guidelines for the treatment of accidental hypothermia exist. In 2010, the American Heart Association and European Resuscitation Council both published guidelines on treatment of accidental hypothermia within the larger context of general guidelines for cardiopulmonary resuscitation (CPR).8,9 The State of Alaska Cold Injuries Guidelines were last updated in 2014 and include a section on accidental hypothermia.10 In 2013, the International Commission for Alpine Rescue- International Commission for Mountain Emergency Medicine (ICAR-MEDCOM) also developed recommendations for on-site medical treatment for acci dental hypothermia.11
Additionally, in 2014, the Wilderness Medical Society developed practice guidelines for out-of-hospital care of accidental hypothermia.12 These guidelines are based on the available literature as described above. Although the literature is not strong, the volume of data, available guidelines, and expert opinion do allow a treating physician to make a logical treatment plan for a patient with hypothermia according to available resources.
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.
To help the reader judge the strength of each reference, pertinent information about the study are included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the authors, will be noted by an asterisk (*) next to the number of the reference.
Megan L. Rischall, MD; Andrea Rowland-Fisher, MD
January 1, 2016
January 31, 2019
Upon completion of this article, participants should be able to:
Date of Original Release: January 1, 2016. Date of most recent review: December 10, 2015. Termination date: January 1, 2019.
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