Wilderness Medical Society practice guidelines for the out-of-hospital evaluation and treatment of accidental hypothermia

The Outcome of Walking Cold Patients with Potential Mild Hypothermia to Safety-A Mountain Rescue Case Series

INTRODUCTION

Some experts recommend that ambulant hypothermic patients should be rewarmed, fed, and not permitted to exercise for 30 min because of concerns that afterdrop can cause cardiac instability. We investigated the outcome of ambulant hypothermic patients in a case series from mountain rescue teams in Great Britain.

METHODS

A questionnaire was used to collect information on a series of adult patients with a clinical diagnosis of mild hypothermia. All patients were alert on the AVPU scale and evacuated by walking from the mountain. The outcome measures were survival or a change in management because of medical deterioration during evacuation.

RESULTS

A series of 108 eligible cases were reported over a 5-year period. When rescuers arrived on the scene, 98 (91%) patients were stationary, and 10 (9%) were still mobile. Thirty-eight (39%) of the stationary cases were walked immediately off the mountain without any on-scene delay. In the remaining 60 (61%) stationary cases, the decision was taken to delay evacuation to provide food, drinks, and additional clothing. In 3 cases, the use of heat packs indicated an intention to actively rewarm. In cases where the on-scene time was reported, 27 (79%) were known to be mobile again within 20 min. All patients survived, and no adverse medical events occurred in all 108 cases.

CONCLUSIONS

In this study, no adverse events occurred because of immediate mobilization, suggesting that in these cases, there appears to be minimal risk of early activity.

Environmental Hypothermia

Although a rare diagnosis in the Emergency Department, hypothermia affects patients in all environments, from urban to mountainous settings. Classic signs of death cannot be interpreted in the hypothermic patient, thus resulting in the mantra, "No one is dead until they're warm and dead." This comprehensive review of environmental hypothermia covers the clinical significance and pathophysiology of hypothermia, pearls and pitfalls in the prehospital management of hypothermia (including temperature measurement techniques and advanced cardiac life support deviations), necessary Emergency Department diagnostics, available rewarming modalities including extracorporeal life support, and criteria for termination of resuscitation.

Prehospital clinical practice guidelines for unintentional injuries: a scoping review and prioritisation process

BACKGROUND

Globally, millions of people die and many more develop disabilities resulting from injuries each year. Most people who die from injuries do so before they are transported to hospital. Thus, reliable, pragmatic, and evidence-based prehospital guidance for various injuries is essential. We systematically mapped and described prehospital clinical practice guidelines (CPGs) for injuries in the global context, as well as prioritised injury topics for guidance development and adolopment.

METHODS

This study was sequentially conducted in three phases: a scoping review for CPGs (Phase I), identification and refinement of gaps in CPGs (Phase II), and ranking and prioritisation of gaps in CPGs (Phase III). For Phase I, we searched PubMed, SCOPUS, and Trip Database; guideline repositories and websites up to 23^rd May 2021. Two authors in duplicate independently screened titles and abstract, and full-text as well as extracted data of eligible CPGs. Guidelines had to meet 60% minimum methodological quality according to rigour of development domain in AGREE II. The second and third phases involved 17 participants from 9 African countries and 1 from Europe who participated in a virtual stakeholder engagement workshop held on 5 April 2022, and followed by an online ranking process.

RESULTS

Fifty-eight CPGs were included out of 3,427 guidance documents obtained and screened. 39/58 (67%) were developed de novo compared to 19 that were developed using alternative approaches. Twenty-five out of 58 guidelines (43%) were developed by bodies in countries within the WHO European Region, while only one guideline was targeted to the African context. Twenty-five (43%) CPGs targeted emergency medical service providers, while 13 (22%) targeted first aid providers (laypeople). Forty-three CPGs (74%) targeted people of all ages. The 58 guidance documents contained 32 injury topics. Injuries linked to road traffic accidents such as traumatic brain injuries and chest injuries were among the top prioritised topics for future guideline development by the workshop participants.

CONCLUSION

This study highlights the availability, gaps and priority injury topics for future guideline development/adolopment, especially for the African context. Further research is needed to evaluate the recommendations in the 58 included CPGs for possible adaptation to the African context.

Wilderness Medicine: Impacts from the Weather, Water, and World

Pediatricians play an important role in the prevention of injuries and provide families with anticipatory guidance regularly. As more families are traveling and spending time outdoors, we must be adept at providing them with knowledge and resources to set them up for success on their adventures. Prevention and preparation frequently can help limit injuries sustained in the wilderness. This article will focus specifically on injuries related to the environment (eg, cold weather injuries, heat-related illnesses) and travel location (eg, high-altitude illness, marine-related injuries, diving medicine). [Pediatr Ann. 2022;51(6):e212-217.].

Successful Non-Extracorporeal Rewarming from Hypothermic Cardiac Arrest: 2 Cases

Accidental hypothermia (core temperature <35°C) is a complication in persons who have fallen into crevasses; hypothermic cardiac arrest is the most serious complication. Extracorporeal life support (ECLS) is the optimal method for rewarming hypothermic cardiac arrest patients, but it may not be readily available and non-ECLS rewarming may be required. We report the medical course of 2 patients with hypothermic cardiac arrest, each of whom had fallen into a crevasse. They were treated successfully with non-ECLS rewarming using peritoneal and thoracic lavage. We discuss non-ECLS treatment options for hypothermic cardiac arrest and describe successful non-ECLS rewarming in an outlying hospital without ECLS rewarming capability in the Grossglockner region of Austria in 1990 and 2003. Both patients survived neurologically intact. Non-ECLS rewarming in a trauma center without ECLS capabilities is feasible and can result in a good outcome when ECLS is not available. The best non-ECLS rewarming method for hypothermic cardiac arrest patients has not yet been established. Non-ECLS rewarming should be adapted to local capabilities. To obtain more robust evidence, it seems reasonable to pool data on the treatment and outcome of non-ECLS rewarming in hypothermic cardiac arrest patients.

Vital Signs in Accidental Hypothermia

Pasquier, Mathieu, Evelien Cools, Ken Zafren, Pierre-Nicolas Carron, Vincent Frochaux, and Valentin Rousson. Vital signs in accidental hypothermia. High Alt Med Biol. 22: 142-147, 2021. Background: Clinical indicators are used to stage hypothermia and to guide management of hypothermic patients. We sought to better characterize the influence of hypothermia on vital signs, including level of consciousness, by studying cases of patients suffering from accidental hypothermia. Materials and Methods: We retrospectively included patients aged ≥18 years admitted to the hospital with a core temperature below 35°C. We identified the cases from a literature review and from a retrospective case series of hypothermic patients admitted to the hospital between 1994 and 2016. Patients who experienced cardiac arrest, as well as those with potential confounders such as concomitant diseases or intoxications, were excluded. Relationships between core temperature and heart rate, systolic blood pressure, respiratory rate, and level of consciousness were explored via correlations and regression. Results: Of the 305 cases reviewed, 216 met the criteria for inclusion. The mean temperature was 29.7°C ± 4.2°C (range 19.3°C-34.9°C). The relationships between temperature and each of the four vital signs were generally linear and significantly positive, with Spearman correlations for respiratory rate, heart rate, systolic blood pressure, and Glasgow Coma Score (GCS) of 0.29 (p = 0.024), 0.44 (p < 0.001), 0.47 (p < 0.001), and 0.78 (p < 0.001), respectively. Based on linear regression, the mean decrease of a vital sign associated with a 1°C decrease of temperature was estimated to be 0.50 minute^-1 for respiratory rate, 2.54 minutes^-1 for heart rate, 4.36 mmHg for systolic blood pressure, and 0.88 for GCS. Conclusions: There is a significant positive correlation between core temperature and heart rate, systolic blood pressure, respiratory rate, and GCS. The relationship between vital signs and temperature is generally linear. This knowledge might help clinicians make appropriate decisions when determining whether the clinical condition of a patient should be attributed to hypothermia. This could enhance clinical care and help to guide future research.

Human torpor: translating insights from nature into manned deep space expedition

During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (T_b ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.

Cardiac Arrest Secondary to Accidental Hypothermia: Who Should We Resuscitate?

Cardiac arrest with a degree of concurrent hypothermia is not a rare presentation. This presentation, often in remote areas, poses a challenge for the prehospital physician because the cause of the arrest will significantly alter decision making and prognostication. Survival from cardiac arrest secondary to accidental hypothermia is significantly greater than that of normothermic arrests when appropriate triage and management decisions are made. The complexity of this decision benefits from a specific algorithm to follow in the event of such a casualty presenting. This article systematically reviews the literature on cardiac arrest secondary to accidental hypothermia and provides recommendations in addition to a novel algorithm to aid the responding prehospital clinician in deciding if a hypothermic resuscitation standard operating procedure should be implemented.

Successful Defibrillation at a Core Temperature of 18.2 Degrees Celsius

Both the temperature at which defibrillation can be effectively used and how often it should be repeated in severe accidental hypothermia have not been definitely established. Current recommendations are based mainly on expert opinion and suggest withholding defibrillation after 3 shocks when the core temperature is below 30°C (86°F). However, growing evidence supports the effectiveness of defibrillation in patients with a core temperature below 30°C (86°F). We present a case of successful defibrillation of a 54-y-old, severely hypothermic patient with a core temperature of 18.2°C (64.8°F). The shock was delivered automatically by an implanted cardioverter-defibrillator shortly after the implementation of extracorporeal rewarming. The patient survived and was discharged from the hospital neurologically intact. It might be reasonable to consider defibrillation attempts in severely hypothermic patients despite current guidelines to the contrary. Increasing coronary perfusion using extracorporeal circulation may result in a better response to defibrillation.

Cardiac Arrest Secondary to Accidental Hypothermia: The Physiology Leading to Hypothermic Arrest

Cardiac arrest secondary to accidental hypothermia is rare in the United Kingdom. However, some evidence suggests that it is under-reported; furthermore, recognizing hypothermia as the cause of death is difficult in the postmortem setting. Urban and rural residents are exposed to cold winter conditions both at home and while undertaking recreational activities. Understanding the physiology underpinning hypothermic cardiac arrest is crucial in order to make informed clinical decisions in regard to triage and management by air ambulance services and in prevention of this rare presentation. This article discusses the epidemiology and pathophysiology of accidental hypothermic to explain how personnel can survive after 8 hours 40 minutes of cardiac arrest.

Comparison of Electric Resistive Heating Pads and Forced-Air Warming for Pre-hospital Warming of Non-shivering Hypothermic Subjects

INTRODUCTION

Victims of severe hypothermia require external rewarming, as self-rewarming through shivering heat production is either minimal or absent. The US Military commonly uses forced-air warming in field hospitals, but these systems require significant power (600-800 W) and are not portable. This study compared the rewarming effectiveness of an electric resistive heating pad system (requiring 80 W) to forced-air rewarming on cold subjects in whom shivering was pharmacologically inhibited.

MATERIALS AND METHODS

Shivering was inhibited by intravenous meperidine (1.5 mg/kg), administered during the last 10 min of cold-water immersion. Subjects then exited from the cold water, were dried and lay on a rescue bag for 120 min in one of the following conditions: spontaneous rewarming only (rescue bag closed); electric resistive heating pads (EHP) wrapped from the anterior to posterior torso (rescue bag closed); or, forced-air warming (FAW) over the anterior surface of the body (rescue bag left open and cotton blanket draped over warming blanket). Supplemental meperidine (to a maximum cumulative dose of 3.3 mg/kg) was administered as required during rewarming to suppress shivering.

RESULTS

Six healthy subjects (3 m, 3 f) were cooled on three different occasions, each in 8°C water to an average nadir core temperature of 34.4 ± 0.6°C (including afterdrop). There were no significant differences between core rewarming rates (spontaneous; 0.6 ± 0.3, FAW; 0.7 ± 0.2, RHP; 0.6 ± 0.2°C/h) or post-cooling afterdrop (spontaneous; 1.9 ± 0.4, FAW; 1.9 ± 0.3, RHP; 1.6 ± 0.2°C) in any of the 3 conditions. There were also no significant differences between metabolic heat production (S; 74 ± 20, FAW; 66 ± 12, RHP; 63 ± 9 W). Total heat gain was greater with FAW (36 W gain) than EHP (13 W gain) and spontaneous (13 W loss) warming (p < 0.005).

CONCLUSIONS

Total heat gain was greater in FAW than both EHP, and spontaneous rewarming conditions, however, there were no observed differences found in rewarming rates, post-cooling afterdrop or metabolic heat production. The electric heat pad system provided similar rewarming performance to a forced-air warming system commonly used in US military field hospitals for hypothermic patients. A battery-powered version of this system would not only relieve pressure on the field hospital power supply but could also potentially allow extending use to locations closer to the field of operations and during transport. Such a system could be studied in larger groups in prospective trials on colder patients.

Reduction of Arterial Oxygen Saturation Among Rescuers During Cardiopulmonary Resuscitation in a Hypobaric Hypoxic Environment

We experienced a case involving prolonged cardiopulmonary resuscitation (CPR) during cardiac arrest on Mt. Fuji (3776 m), demanding lengthy exertion by the rescuers performing CPR. Considering the effects of exertion on the rescuers, we examined their percutaneous arterial oxygen saturation during simulated CPR and compared the effects of compression-only and conventional CPR at 3700 m above sea level. The effects of CPR on the physical condition of rescuers were examined at the summit of Mt. Fuji: three rescue staff equipped with pulse-oximeters performed CPR with or without breaths using a CPR mannequin. At 3700 m, the rescuers' heart rate increased during CPR regardless of the presence or absence of rescue breathing. Percutaneous arterial oxygen saturation measured in such an environment was reduced only when CPR without rescue breathing was performed. Scores on the Borg scale, a subjective score of fatigue, after CPR in a 3700 m environment were 13 to 15 of 20 (somewhat hard to hard). Performing CPR at high altitude exerts a significant physical effect upon the condition of rescuers. Compression-only CPR at high altitude may cause a deterioration in rescuer oxygenation, whereas CPR with rescue breathing might ameliorate such deterioration.

Cardiac Arrest Secondary to Accidental Hypothermia: Rewarming Strategies in the Field

Hypothermic cardiac arrest is rare and poses a challenge to prehospital responders. Standard cardiac arrest protocols advise treating reversible causes of arrest; however, rewarming the cold casualty is not easily achieved in the field. This article aimed to review the literature on hypothermia in order to produce evidence-based recommendations on rewarming that could realistically be applied to hypothermic cardiac arrest patients.

Intra-patient potassium variability after hypothermic cardiac arrest: a multicentre, prospective study

Background

To date, the decision to set up therapeutic extra-corporeal life support (ECLS) in hypothermia-related cardiac arrest is based on the potassium value only. However, no information is available about how the analysis should be performed. Our goal was to compare intra-individual variation in serum potassium values depending on the sampling site and analytical technique in hypothermia-related cardiac arrests.

Methods

Adult patients with suspected hypothermia-related refractory cardiac arrest, admitted to three hospitals with ECLS facilities were included. Blood samples were obtained from the femoral vein, a peripheral vein and the femoral artery. Serum potassium was analysed using blood gas (BGA) and clinical laboratory analysis (CL).

Results

Of the 15 consecutive patients included, 12 met the principal criteria, and 5 (33%) survived. The difference in average potassium values between sites or analytical method used was ≤1 mmol/L. The agreement between potassium values according to the three different sampling sites was poor. The ranges of the differences in potassium using BGA measurement were − 1.6 to + 1.7 mmol/L; − 1.18 to + 2.7 mmol/L and − 0.87 to + 2 mmol/L when comparing respectively central venous and peripheral venous, central venous and arterial, and peripheral venous and arterial potassium.

Conclusions

We found important and clinically relevant variability in potassium values between sampling sites. Clinical decisions should not rely on one biological indicator. However, according to our results, the site of lowest potassium, and therefore the preferred site for a single potassium sampling is central venous blood. The use of multivariable prediction tools may help to mitigate the risks inherent in the limits of potassium measurement.

Trial registration

ClinicalTrials.gov Identifier: NCT03096561.

Hypothermie accidentelle

L’hypothermie accidentelle est définie comme une baisse non intentionnelle de la température centrale du corps en dessous de 35 °C. La prévention de l’hypothermie est essentielle. La mesure de la température centrale est nécessaire au diagnostic d’hypothermie et permet d’en juger la sévérité. En présence de signes de vie, et en présence d’une hypothermie pure, l’instabilité hémodynamique apparente ne devrait en principe pas faire l’objet d’une prise en charge spécifique. Un risque d’arrêt cardiaque (AC) est présent si la température chute en dessous de 30–32 °C. En raison du risque d’AC, un patient hypotherme devrait bénéficier de l’application d’un monitoring avant toute mobilisation, laquelle devra être prudente. En cas d’AC, seule la mesure de la température oesophagienne est fiable. Si l’hypothermie est suspectée comme étant potentiellement responsable de l’AC du patient, celui-ci doit être transporté sous réanimation cardiopulmonaire vers un hôpital disposant d’une méthode de réchauffement par circulation extracorporelle (CEC). La valeur de la kaliémie ainsi que les autres paramètres à disposition (âge, sexe, valeur de la température corporelle, durée du low flow, présence d’une asphyxie) permettront de décider de l’indication d’une CEC de réchauffement. Le pronostic des patients victimes d’un AC sur hypothermie est potentiellement excellent, y compris sur le plan neurologique.

An evaluation of the Swiss staging model for hypothermia using hospital cases and case reports from the literature

BACKGROUND

The Swiss staging model for hypothermia uses clinical indicators to stage hypothermia and guide the management of hypothermic patients. The proposed temperature range for clinical stage 1 is < 35-32 °C, for stage 2 is < 32-28 °C, for stage 3 is < 28-24 °C, and for stage 4 is below 24 °C. Our previous study using 183 case reports from the literature showed that the measured temperature only corresponded to the clinical stage in the Swiss staging model in approximately 50% of cases. This study, however, included few patients with moderate hypothermia. We aimed to expand this database by adding cases of hypothermic patients admitted to hospital to perform a more comprehensive evaluation of the staging model.

METHODS

We retrospectively included patients aged ≥18 y admitted to hospital between 1.1.1994 and 15.7.2016 with a core temperature below 35 °C. We added the cases identified through our previously published literature review to estimate the percentage of those patients who were correctly classified and compare the theoretical with the observed temperature ranges for each clinical stage.

RESULTS

We included 305 cases (122 patients from the hospital sampling and the 183 previously published). Using the theoretically derived temperature ranges for clinical stages resulted in 185/305 (61%) patients being assigned to the correct temperature range. Temperature was overestimated using the clinical stage in 55/305 cases (18%) and underestimated in 65/305 cases (21%); important overlaps in temperature existed among the four stage groups. The optimal temperature thresholds for discriminating between the four stages (32.1 °C, 27.5 °C, and 24.1 °C) were close to those proposed historically (32 °C, 28 °C, and 24 °C).

CONCLUSIONS

Our results provide further evidence of the relationship between the clinical state of patients and their temperature. The historical proposed temperature thresholds were almost optimal for discriminating between the different stages. Adding overlapping temperature ranges for each clinical stage might help clinicians to make appropriate decisions when using clinical signs to infer temperature. An update of the Swiss staging model for hypothermia including our methodology and findings could positively impact clinical care and future research.

Human Responses to 5 Heated Hypothermia Wrap Systems in a Cold Environment

INTRODUCTION

We compared the effectiveness of 5 heated hypothermia wrap systems.

METHODS

Physiologic and subjective responses were determined in 5 normothermic subjects (1 female) for 5 heated hypothermia wraps (with vapor barrier and chemical heat sources) during 60 min of exposure to a temperature of -22°C. The 5 systems were 1) user-assembled; 2) Doctor Down Rescue Wrap; 3) hypothermia prevention and management kit (HPMK); 4) MARSARS Hypothermia Stabilizer Bag; and 5) Wiggy's Victims Casualty Hypothermia Bag. Core and skin temperature, metabolic heat production, skin heat loss, and body net heat gain were determined. Subjective responses were also evaluated for whole body cold discomfort, overall shivering rating, overall temperature rating, and preferential ranking.

RESULTS

The Doctor Down and user-assembled systems were generally more effective, with higher skin temperatures and lower metabolic heat production; they allowed less heat loss, resulting in higher net heat gain (P<0.05). HPMK had the lowest skin temperature and highest shivering heat production and scored worse than the other 4 systems for the "whole body cold discomfort" and "overall temperature" ratings (P<0.05).

CONCLUSIONS

The user-assembled and Doctor Down systems were most effective, and subjects were coldest with the HPMK system. However, it is likely that any of the tested systems would be viable options for wilderness responders, and the choice would depend on considerations of cost; volume, as it relates to available space; and weight, as it relates to ability to carry or transport the system to the patient.

Management of accidental hypothermia: A narrative review

A narrative review is presented on the diagnosis, treatment and management of accidental hypothermia. Although all these processes form a continuum, for descriptive purposes in this manuscript the recommendations are organized into the prehospital and in-hospital settings. At prehospital level, it is advised to: a) perform high-quality cardiopulmonary resuscitation for cardiac arrest patients, regardless of body temperature; b) establish measures to minimize further cooling; c) initiate rewarming; d) prevent rescue collapse and continued cooling (afterdrop); and (e) select the appropriate hospital based on the clinical and hemodynamic situation of the patient. Extracorporeal life support has revolutionized rewarming of the hemodynamically unstable victim or patients suffering cardiac arrest, with survival rates of up to 100%. The new evidences indicate that the management of accidental hypothermia has evolved favorably, with substantial improvement of the final outcomes.

Accidental hypothermia in recreational activities in the mountains: A narrative review

The popularity of recreational activities in the mountains worldwide has led to an increase in the total number of persons exposed to cold and extreme environments through recreation. There is little conclusive evidence about the risk of hypothermia for specific activities or populations, nor is it clear which activities are represented in the literature. This is a non-systematic review of accidental hypothermia in different recreational activities in the mountains, with a specific focus on outdoor or winter activities that potentially involve cold exposure. Cases of hypothermia have been reported in the literature in mountaineering, trekking, hiking, skiing, activities performed in the backcountry, ultra-endurance events, and databases from search and rescue services that include various types of recreation. Of these activities, hypothermia as a primary illness occurs most commonly during mountaineering in the highest elevation areas in the world and during recreation practiced in more northern or remote areas. Hypothermia in skiers, snowboarders, and glacier-based activities is most often associated with accidents occurring off-piste or in the backcountry (crevasse, avalanche). Organizers of outdoor events also have a role in reducing the incidence of hypothermia through medical screening and other preparedness measures. More complete collection and reporting of data on mild hypothermia and temperature measurement would improve our understanding of the incidence of hypothermia in outdoor recreation in future.

Challenges of Military Health Service Support in Mountain Warfare

INTRODUCTION

History is full of examples of the influence of the mountain environment on warfare. The aim of this article is to identify the main environmental hazards and summarize countermeasures to mitigate the impact of this unique environment.

METHODS

A selective PubMed and Internet search was conducted. Additionally, we searched bibliographies for useful supplemental literature and included the recommendations of the leading mountain medicine and wilderness medicine societies.

RESULTS

A definition of mountain warfare mainly derived from environmental influences on body functions is introduced to help identify the main environmental hazards. Cold, rugged terrain, hypoxic exposure, and often a combination and mutual aggravation of these factors are the most important environmental factors of mountain environment. Underestimating this environmental influence has decreased combat strength and caused thousands of casualties during past conflicts. Some marked differences between military and civilian mountaineering further complicate mission planning and operational sustainability.

CONCLUSIONS

To overcome the restrictions of mountain environments, proper planning and preparation, including sustained mountain mobility training, in-depth mountain medicine training with a special emphasize on prolonged field care, knowledge of acclimatization strategies, adapted time calculations, mountain-specific equipment, air rescue strategies and makeshift evacuation strategies, and thorough personnel selection, are vital to guarantee the best possible medical support. The specifics of managing risks in mountain environments are also critical for civilian rescue missions and humanitarian aid.

Severe Hypothermia Management in Mountain Rescue: A Survey Study

Podsiadło, Paweł, Tomasz Darocha, Sylweriusz Kosiński, Kinga Sałapa, Mirosław Ziętkiewicz, Tomasz Sanak, Rachel Turner, and Hermann Brugger. Severe hypothermia management in mountain rescue: A survey study. High Alt Med Biol 18:411–416, 2017.

Introduction: Severe hypothermia is a rare but demanding medical emergency. Although mortality is high, if well managed, the neurological outcome of survivors can be excellent. The aim of the study was to assess whether mountain rescue teams (MRTs) are able to meet the guidelines in the management of severe hypothermia, regarding their equipment and procedures.

Methods: Between August and December 2016, an online questionnaire, with 24 questions to be completed using Google Forms, was sent to 123 MRTs in 27 countries.

Results: Twenty-eight MRTs from 10 countries returned the completed questionnaire. Seventy-five percent of MRTs reportedly provide advanced life support (ALS) on-site and 89% are regularly trained in hypothermia management. Thirty-two percent of MRTs transport hypothermic patients in cardiac arrest to the nearest hospital instead of an Extracorporeal Life Support facility; 39% are equipped with mechanical chest compression devices; 36% measure core body temperature on-site and no MRT is equipped with a device to measure serum potassium concentration on-site in avalanche victims.

Conclusions: Most MRTs are regularly trained in the treatment of severe hypothermia and provide ALS. The majority are not equipped to follow standard procedural guidelines for the treatment of severely hypothermic patients, especially with cardiac arrest. However, the low response rate—23% (28/123)—could have induced a bias.

Brief Rewarming Blunts Hypothermia-Induced Alterations in Sensation, Motor Drive and Cognition

Background: It is well known that cold exposure experienced during occupational or recreational activities may adversely affect motor, cognitive performance, and health. Most research has used prolonged passive external rewarming modalities and focused on the direct effects on the kinetics of physiological and psychological responses in hypothermic subjects. However, the brief whole body rewarming effects on physiological and psychological responses in parallel with functional consequences on cognitive and neurophysiological functions have not been investigated. This study explores these effects in 12 healthy young men.

Methods: Subjects (20 ± 1 years) participated in 4 randomized trials, which were designed to compare the effects of whole-body brief (5-min) rewarming in 37°C water with rewarming for the same duration in 24°C (air) thermoneutral environment in mildly hypothermic subjects. After each rewarming, indicators of neuromuscular function (reflexes, central activation ratio, electromyography of exercising muscle, and contractile properties of calf muscles) and cognitive function (attention, simple motor speed, and information processing speed) were assessed.

Results: Compared to rewarming in thermoneutral environment, after brief rewarming in 37°C water, significantly lower metabolic heat production (MHP) (206 ± 33.4 vs. 121.9 ± 24.3 W·m², P < 0.01), heart rate (76 ± 16 vs. 60 ± 12 b·min⁻¹, P < 0.01), cold strain (6.4 ± 3.1 vs. 5.3 ± 2.7, P < 0.01), improved thermal comfort and induced cessation of shivering were found. Electrically induced maximum torque amplitudes increased (P100, 102.8 ± 21.3 vs. 109.2 ± 17.5 Nm and PTT100, 83.1 ± 17.1 vs. 92.7 ± 16.0 Nm, P < 0.05), contraction half-relaxation time decreased (599.0 ± 53.8 vs. 589.0 ± 56.3 ms, P < 0.05), and M_max-wave latency shortened (17.5 ± 2.2 vs. 15.6 ± 2.0 ms, P < 0.05) after 37°C water rewarming. Unlike rewarming in thermoneutral environment, 37°C water rewarming blunted the hypothermia-induced alterations in neural drive transmission (4.3 ± 0.5 vs. 3.4 ± 0.8 mV H-reflex and 4.9 ± 0.2 vs. 4.4 ± 0.4 mV V-wave, P < 0.05), which increased central fatigue during a 2-min maximum load (P < 0.05). Furthermore, only in brief warm water rewarming cerebral alterations were restored to the control level and it was indicated by shortened reaction times (P < 0.05).

Conclusions: Brief rewarming in warm water rather than the same duration rewarming in thermoneutral environment blunted the hypothermia-induced alterations for sensation, motor drive, and cognition, despite the fact that rectal and deep muscle temperature remained lowered.

Extracorporeal Life Support for Refractory Cardiac Arrest from Accidental Hypothermia: A 10-Year Experience in Edinburgh

BACKGROUND

Cardiac arrest caused by accidental hypothermia is a rare phenomenon with a significant mortality rate if untreated. The consensus is that these patients should be rewarmed with extracorporeal life support (ECLS) with the potential for excellent survival and neurologic outcomes. However, given the lack of robust data and clinical trials, the optimal management of such patients remains elusive.

OBJECTIVE

In this single-center study, we looked at the outcomes of all adult patients undergoing salvage ECLS for cardiac arrest caused by accidental hypothermia over a 10-year period from June 2006 to June 2016.

METHODS

These data were obtained from the Royal Infirmary of Edinburgh cardiothoracic surgery database. The patients' hard copy case notes, TrakCare (InterSystems Corp, Cambridge, MA), picture archiving and communications system (PACS), and WardWatcher databases were used to cross-check the accuracy of the acquired data.

RESULTS

Eleven patients met the inclusion criteria. The etiology of hypothermia was exposure to cold air (64%) and cold water immersion (36%). Two (18%) were treated with extracorporeal membrane oxygenation and the rest with cardiopulmonary bypass. The mean age was 51 years (range 32-73), and the mean core body temperature on admission was 20.6°C (range <18-24°C). The overall survival rate to hospital discharge was 72%, with 75% of survivors having no chronic neurologic impairment.

CONCLUSION

Our case series shows the remarkable salvageability of patients suffering prolonged cardiac arrest caused by accidental hypothermia, particularly in the absence of asphyxia, trauma, or severe hyperkalemia. ECLS is a safe and effective rewarming treatment and should be used to aggressively manage this patient group.

Dull Brains and Frozen Feet: A Historical Essay on Cold

This essay will review historical and medical aspects of cold exposure, hypothermia, and frostbite during the Napoleonic era. The 19th century writings of Dominique Jean Larrey, Pierre Jean Moricheau-Beaupré, and others are used to provide an evocative supporting narrative to illustrate some of the cold illnesses, physiology, and theory of both an earlier era and the present time. Medical care for over a century followed the how but not the why of treating frostbite and hypothermia slowly with snow or cold water rather than heat. There were 2 main reasons: First was a practical attempt to limit gangrene. Less known, and long forgotten, is a major rationale based on the erroneous theory of heat called "the caloric." Because of these 2 reasons, the slow method of "cold warming" remained standard medical practice well into the 20th century. Although these recommendations are now known to be flawed, some of the reasons behind them will be discussed, along with early but correct observations on afterdrop and circumrescue collapse. There is a long backstory of treatment from 1812 to the present.

Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

The Role of Hypothermia Coordinator: A Case of Hypothermic Cardiac Arrest Treated with ECMO

Darocha, Tomasz, Sylweriusz Kosinski, Maciej Moskwa, Anna Jarosz, Dorota Sobczyk, Robert Galazkowski, Marcin Slowik, and Rafal Drwila. The role of hypothermia coordinator: A case of hypothermic cardiac arrest treated with ECMO. High Alt Biol Med 16:352-355, 2015.—We present a description of emergency medical rescue procedures in a patient suffering from severe hypothermia who was found in the Babia Gora mountain range (Poland). After diagnosing the symptoms of II/III stage hypothermia according to the Swiss Staging System, the Mountain Rescue Service notified the coordinator from the Severe Accidental Hypothermia Center (CLHG) Coordinator in Krakow and then kept in constant touch with him. In accordance with the protocol for managing such situations, the coordinator started the procedure for patients in severe hypothermia with the option of extracorporeal warming and secured access to a device for continuous mechanical chest compression. After reaching the hospital, extracorporeal warming with ECMO support in the arteriovenuous configuration was started. The total duration of circulatory arrest was 150 minutes. The rescue procedures were supervised by the coordinator, who was on 24-hour duty and was reached by means of an alarm phone. The task of the coordinator is to consult the management of hypothermia cases, use his knowledge and experience to help in the diagnosis and treatment. and if the need arises refer the patient for ECMO at CLHG. Good coordination, planning, predicting possible problems, and acting in accordance with the agreed procedures in the scheme, make it possible to shorten the time of reaching the destination hospital and implement effective treatment.

New diastolic cardiomyopathy in patients with severe accidental hypothermia after ECMO rewarming: a case-series observational study

Introduction

Accidental hypothermia is a condition associated with significant morbidity and mortality. Hypothermia has been reported to affect left ventricular systolic and diastolic function. However, most of the data come from animal experimental studies.

Aim of the study

The purpose of the present study was to assess the impact of severe accidental hypothermia on systolic and diastolic ventricular function in patients treated using veno-arterial extracorporeal membrane oxygenation (ECMO).

Methods

We prospectively assessed nine hypothermic patients (8 male, age 25–78 years) who were transferred to the Severe Accidental Hypothermia Center and treated with ECMO. Transthoracic echocardiography was performed on admission (in patients without cardiac arrest) and on discharge from ICU after achieving cardiovascular stability. Cardiorespiratory stability and full neurologic recovery was achieved in all patients.

Results

Biomarkers of myocardial damage (CK, CKMB, hsTnT) were significantly elevated in all study patients. Admission echocardiography performed in patients in sinus rhythm, revealed moderate-severe bi-ventricular systolic dysfunction and moderate bi-ventricular diastolic dysfunction. Discharge echocardiography showed persistent mild bi-ventricular diastolic dysfunction, although systolic function of both ventricles returned to normal. Discharge echocardiography in patients admitted with cardiac arrest showed normal (5 patients) or moderately impaired (1 patient) global LV systolic function on discharge. However, mild or moderate LV diastolic dysfunction was observed in all 6 patients. Discharge RV systolic function was normal, whereas mild RV diastolic dysfunction was present in these patients.

Conclusion

After severe accidental hypothermia bi-ventricular diastolic dysfunction persists despite systolic function recovery in survivors treated with ECMO.

The prehospital management of avalanche victims

Avalanche accidents are frequently lethal events with an overall mortality of 23%. Mortality increases dramatically to 50% in instances of complete burial. With modern day dense networks of ambulance services and rescue helicopters, health workers often become involved during the early stages of avalanche rescue. Historically, some of the most devastating avalanche accidents have involved military personnel. Armed forces are frequently deployed to mountain regions in order to train for mountain warfare or as part of ongoing conflicts. Furthermore, military units are frequently called to assist civilian organised rescue in avalanche rescue operations. It is therefore important that clinicians associated with units operating in mountain regions have an understanding of, the medical management of avalanche victims, and of the preceding rescue phase. The ensuing review of the available literature aims to describe the pathophysiology particular to avalanche victims and to outline a structured approach to the search, rescue and prehospital medical management.