Elsevier

Injury

Volume 49, Issue 2, February 2018, Pages 149-164
Injury

Review article
The prehospital management of hypothermia — An up-to-date overview

https://doi.org/10.1016/j.injury.2017.11.001Get rights and content

Abstract

Background

Accidental hypothermia concerns a body core temperature of less than 35 °C without a primary defect in the thermoregulatory system. It is a serious threat to prehospital patients and especially injured patients, since it can induce a vicious cycle of the synergistic effects of hypothermia, acidosis and coagulopathy; referred to as the trauma triad of death. To prevent or manage deterioration of a cold patient, treatment of hypothermia should ideally begin prehospital. Little effort has been made to integrate existent literature about prehospital temperature management. The aim of this study is to provide an up-to-date systematic overview of the currently available treatment modalities and their effectiveness for prehospital hypothermia management.

Data sources

Databases PubMed, EMbase and MEDLINE were searched using the terms: “hypothermia”, “accidental hypothermia”, “Emergency Medical Services” and “prehospital”. Articles with publications dates up to October 2017 were included and selected by the authors based on relevance.

Results

The literature search produced 903 articles, out of which 51 focused on passive insulation and/or active heating. The most effective insulation systems combined insulation with a vapor barrier. Active external rewarming interventions include chemical, electrical and charcoal-burning heat packs; chemical or electrical heated blankets; and forced air warming. Mildly hypothermic patients, with significant endogenous heat production from shivering, will likely be able to rewarm themselves with only insulation and a vapor barrier, although active warming will still provide comfort and an energy-saving benefit. For colder, non-shivering patients, the addition of active warming is indicated as a non-shivering patient will not rewarm spontaneously. All intravenous fluids must be reliably warmed before infusion.

Conclusion

Although it is now accepted that prehospital warming is safe and advantageous, especially for a non-shivering hypothermic patient, this review reveals that no insulation/heating combinations stand significantly above all the others. However, modern designs of hypothermia wraps have shown promise and battery-powered inline fluid warmers are practical devices to warm intravenous fluids prior to infusion. Future research in this field is necessary to assess the effectiveness expressed in patient outcomes.

Introduction

Accidental hypothermia is defined as an unintentional decrease in body temperature to below 35 °C, without the presence of a primary defect in the patient’s thermoregulatory mechanism. It can be subdivided into mild (35–32 °C), moderate (32–28 °C) and severe ( <28 °C) hypothermia; a temperature below which cardiac arrest or low flow state can occur [1]. Hypothermia negatively affects multiple organ systems [2], [3], [4], [5], [6], and is associated with poor outcomes including death [7], [8], [9], [10], [11], [12], [13]. In the United States, approximately 1500 people die of primary hypothermia each year [14]. The etiology of hypothermia is multifactorial and the assumed main causes of accidental hypothermia in injured patients are heat loss due to environmental exposure, the administration of cold intravenous fluids, hemorrhagic shock and the effects of anesthesia or sedation on thermoregulation [15], [16], [17].

All prehospital patients could become hypothermic due to their sickness or injury. Especially in the severely injured trauma patients its incidence ranges from 13.3% to 43% in various prehospital environments worldwide [11], [13], [18], [19], [20]. In studies of trauma patients who were hypothermic on arrival at the emergency department, the average core temperature was 33.5 °C [13], [18], [19], [21], [22]. Hypothermia is one of the components of the trauma triad of death, which is a vicious cycle caused by the synergistic effects that hypothermia, coagulopathy and acidosis have on each other [18], [25], [26], [27].

One of the effects of hypothermia is poor tissue oxygenation throughout the body caused by peripheral vasoconstriction, decreased myocardial contractility and decreased oxygen release from hemoglobin to tissue [16], [23], [24], [25]. This effect on tissue oxygenation causes an increase in the cell metabolism’s proportion of anaerobic metabolism. Normally, during aerobic metabolism, heat is produced by the hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP); in contrast, the anaerobic metabolism results in decreased ATP synthesis and consequently decreased heat production. Anaerobic metabolism also produces higher lactate levels and causes metabolic acidosis [24].

The activity of coagulation enzymes decreases with acidosis [15] and lower body temperatures. In addition, hypothermia causes a defect in the aggregation and adhesion of platelets and a decrease of fibrinogen availability, resulting in prolonged bleeding times [26], [27]. These abnormalities can be reversed by rewarming [26].

Early recognition and treatment of hypothermia is essential to oppose the deterioration of a patient’s condition. Treatment ideally begins in the prehospital setting and should focus on reducing heat loss, promoting cardiovascular stability, restoring fluid volumes and reversing core cooling. Regarding core temperature maintenance, there is considerable laboratory-based literature specifically regarding properties of insulation materials and heat sources, as well as randomized controlled trials on rewarming methods for cold subjects, but little effort has been made to integrate all of this information. The most recent reviews, which focused primarily on the prehospital treatment of hypothermia, were performed 16 years ago [28], [29]. As well, there is a shortage of large randomized controlled trials conducted in the pre-hospital setting.

The aim of this review article is to provide an up-to-date systematic overview of the available treatment modalities relating to insulation and/or application of heat for the prehospital management of hypothermic patients and to present the best available evidence for their effectiveness to improve patient care.

Section snippets

Methods

The databases PubMed, EMbase (OvidSP) and MEDLINE (OvidSP) were searched using various keywords and strategies; which are listed in Table 1. Articles with publication dates up to October 2017 were reviewed. The relevance of the articles was judged by their title; abstract and full-text; which were all screened by two authors (FH; ET) and discussed with the third author (GG). Articles were included if they contained information about treatment modalities for hypothermia that could be applied

Results

The literature search returned 903 potential inclusions for consideration, of which 51 focused on insulation only (with or without a vapor barrier) (to decrease heat loss) and/or active heating (Fig. 1). An overview of these studies is displayed in Table 2. The interventions are categorized into insulation/vapor barrier materials, external heat sources and heat sources with internal heat transfer. The term ‘hypothermia wrap’ refers to insulation with or without vapor barrier and a heat source.

Discussion

The current practice of prehospital hypothermia management is based on considerable laboratory research but minimal controlled studies on actual patients in the field. In contrast, in-hospital management of cold patients has been studied more thoroughly; effective rewarming methods are available for in-hospital use, such as warm fluid lavage of body cavities or extracorporeal rewarming [81]. Extracorporeal rewarming can be accomplished by hemodialysis, continuous arteriovenous rewarming,

Limitations and strengths

This article provides an up-to-date systematic overview of interventions used for the management of hypothermia in the prehospital setting, after the last review on this topic was performed 16 years ago. A broad literature search was performed by searching multiple databases, using broad search terms without limitations on publication dates.

It is hard to combine the available data and consequently make recommendations about the usefulness of each treatment modality because of the differences in

Conclusion

On the basis of our literature review it can be stated that the best way to manage hypothermia in a prehospital setting is to reduce further heat loss by placing the patient in a warm and dry environment and applying insulation in combination with a vapor barrier. The addition of an active rewarming method such as heat packs or blankets is not compulsory in vigorously shivering patients who will likely warm up eventually, but must be considered when treating severe hypothermic patients who will

Funding

No funding was received for the performance of this study.

Author contributions

Literature search: F.H., E.T.

Study design F.H., E.T.

Data collection: F.H., E.T.

Data analysis: F.H., E.T., G.G.

Data interpretation: F.H., E.T., G.G.

Drafting the manuscript: F.H.

Critical revision of the manuscript: E.T., G.G.

Approval of the version of the manuscript to be published: F.H., E.T., G.G.

References (85)

  • R.S. Hamilton et al.

    The diagnosis and treatment of hypothermia by mountain rescue teams: a survey

    Wilderness Environ Med

    (1996)
  • A. Kober et al.

    Effectiveness of resistive heating compared with passive warming in treating hypothermia associated with minor trauma: a randomized trial

    Mayo Clin Proc

    (2001)
  • R. Greif et al.

    Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial

    Ann Emerg Med

    (2000)
  • E. Kornberger et al.

    Forced air surface rewarming in patients with severe accidental hypothermia

    Resuscitation

    (1999)
  • M.T. Steele et al.

    Forced air speeds rewarming in accidental hypothermia

    Ann Emerg Med

    (1996)
  • J.A. Sterba

    Efficacy and safety of prehospital rewarming techniques to treat accidental hypothermia

    Ann Emerg Med

    (1991)
  • R. Wheeler et al.

    Blood administration in helicopter emergency medical services patients associated with hypothermia

    Air Med J

    (2013)
  • H. Brugger et al.

    Resuscitation of avalanche victims: evidence-based guidelines of the international commission for mountain emergency medicine (ICAR MEDCOM): intended for physicians and other advanced life support personnel

    Resuscitation

    (2013)
  • P. Petrone et al.

    Management of accidental hypothermia and cold injury

    Curr Probl Surg

    (2014)
  • J. Milligan et al.

    Performance comparison of improvised prehospital blood warming techniques and a commercial blood warmer

    Injury

    (2016)
  • B.L. Bennett et al.

    Battlefield trauma-induced hypothermia: transitioning the preferred method of casualty rewarming

    Wilderness Environ Med

    (2017)
  • T.F. Platts-Mills et al.

    An experimental study of warming intravenous fluid in a cold environment

    Wilderness Environ Med

    (2007)
  • M.P. DeClerck et al.

    A Chemical Heat Pack-Based Method For Consistent Heating of Intravenous Fluids

    Wilderness Environ Med

    (2015)
  • M. Pasquier et al.

    Deep accidental hypothermia with core temperature below 24 degrees c presenting with vital signs

    High Alt Med Biol

    (2014)
  • M. Diaz et al.

    Thermoregulation: physiological and clinical considerations during sedation and general anesthesia

    Anesth Prog

    (2010)
  • M.L. Mallet

    Pathophysiology of accidental hypothermia

    QJM

    (2002)
  • M.J. Rohrer et al.

    Effect of hypothermia on the coagulation cascade

    Crit Care Med

    (1992)
  • D.B. Staab et al.

    Coagulation defects resulting from ambient temperature-induced hypothermia

    J Trauma

    (1994)
  • D.D. Watts et al.

    Hypothermic coagulopathy in trauma: effect of varying levels of hypothermia on enzyme speed, platelet function, and fibrinolytic activity

    J Trauma.

    (1998)
  • H.E. Wang et al.

    Admission hypothermia and outcome after major trauma

    Crit Care Med

    (2005)
  • G.J. Jurkovich et al.

    Hypothermia in trauma victims: an ominous predictor of survival

    J Trauma

    (1987)
  • M. Bukur et al.

    Impact of prehospital hypothermia on transfusion requirements and outcomes

    J Trauma Acute Care Surg

    (2012)
  • L.M. Gentilello et al.

    Is hypothermia in the victim of major trauma protective or harmful? A randomized, prospective study

    Ann Surg

    (1997)
  • D.J. Brown et al.

    Accidental hypothermia

    N Engl J Med

    (2012)
  • H.M. Kaafarani et al.

    Damage control resuscitation in trauma

    Scand J Surg

    (2014)
  • A. Langhelle et al.

    Body temperature of trauma patients on admission to hospital: a comparison of anaesthetised and non-anaesthetised patients

    Emerg Med J

    (2012)
  • G.J. Beilman et al.

    Early hypothermia in severely injured trauma patients is a significant risk factor for multiple organ dysfunction syndrome but not mortality

    Ann Surg

    (2009)
  • F. Lapostolle et al.

    Hypothermia in trauma victims at first arrival of ambulance personnel: an observational study with assessment of risk factors

    Scand J Trauma Resusc Emerg Med

    (2017)
  • S. Kosinski et al.

    Accidental hypothermia in Poland – estimation of prevalence, diagnostic methods and treatment

    Scand J Trauma Resusc Emerg Med

    (2015)
  • M.R. Cassar et al.

    A study of hypothermic patients presenting to a Mediterranean emergency department

    Eur J Emerg Med

    (2015)
  • R. Gerecht

    The lethal triad. Hypothermia, acidosis & coagulopathy create a deadly cycle for trauma patients

    JEMS

    (2014)
  • T. Kheirbek et al.

    Hypothermia in bleeding trauma: a friend or a foe?

    Scand J Trauma Resusc Emerg Med

    (2009)
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    A previous version of the abstract of this article was presented as a poster at the European Congress of Trauma and Emergency Surgery from May 7th to May 9th 2017, Boekarest, Romania.

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