Cause of Death in Avalanche Fatalities

Wilderness Medical Society Clinical Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents: 2024 Update

To provide guidance to the general public, clinicians, and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to revise the evidence-based guidelines for the prevention, rescue, and resuscitation of avalanche and nonavalanche snow burial victims. The original panel authored the Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents in 2017. A second panel was convened to update these guidelines and make recommendations based on quality of supporting evidence.

Hypothermic cardiac arrest patients admitted to hospital who were not rewarmed with extracorporeal life support: A retrospective study

Aims

Our goal was to study hypothermic cardiac arrest (CA) patients who were not rewarmed by Extracorporeal Life Support (ECLS) but were admitted to a hospital equipped for it. The focus was on whether the decisions of non-rewarming, meaning termination of resuscitation, were compliant with international guidelines based on serum potassium at hospital admission.

Methods

We retrospectively included all hypothermic CA who were not rewarmed, from three Swiss centers between 1st January 2000 and 2nd May 2021. Data were extracted from medical charts and assembled into two groups for analysis according to serum potassium. We identified the criteria used to terminate resuscitation. We also retrospectively calculated the HOPE score, a multivariable tool predicting the survival probability in hypothermic CA undergoing ECLS rewarming.

Results

Thirty-eight victims were included in the study. The decision of non-rewarming was compliant with international guidelines for 12 (33%) patients. Among the 36 patients for whom the serum potassium was measured at hospital admission, 24 (67%) had a value that - alone - would have indicated ECLS. For 13 of these 24 (54%) patients, the HOPE score was <10%, meaning that ECLS was not indicated. The HOPE estimation of the survival probabilities, when used with a 10% threshold, supported 23 (68%) of the non-rewarming decisions made by the clinicians.

Conclusions

This study showed a low adherence to international guidelines for hypothermic CA patients. In contrast, most of these non-rewarming decisions made by clinicians would have been compliant with current guidelines based on the HOPE score.

Avalanche Airbag Usage and Risk Attitudes of Backcountry Skiers and Snowboarders in the American West

INTRODUCTION

Backcountry skiers and snowboarders are increasingly using avalanche airbags to improve safety. New safety devices can cause risk compensation, the concept in which users take more risks given the larger safety margin provided by the device. This may limit overall benefits. We sought to elucidate attitudes toward risk-taking behaviors and risk compensation in backcountry users relating to avalanche airbags.

METHODS

A convenience sample of 144 backcountry skiers and snowboarders was surveyed after a backcountry tour in the Wasatch Mountains of Utah and the Tetons of Wyoming during the winter 2020-21 season. Demographic and experiential data were compared with risk propensity scores and attitudes toward risk compensation. Respondents were stratified into high-, medium-, and low-risk groupings based on risk propensity scores and whether an airbag was carried.

RESULTS

Thirty-two (22%) respondents carried an airbag. Airbag users were more likely to endorse risk compensation behavior, ski terrain over 30 degrees, and fall into the high-risk cohort. The high-risk cohort was also more likely to endorse risk compensation behavior than medium- and low-risk individuals.

CONCLUSIONS

Risk compensation was more prevalent in 2 groups: 1) those carrying an airbag and 2) those falling within the high-risk cohort. Given the prevalence of avalanche airbags, risk compensation should be considered alongside other human factors in avalanche safety and education so that users can mitigate these effects. Although risk compensation appears to be occurring, the magnitude of this effect remains unknown and likely does not obviate the safety benefits of the airbag altogether.

On-site treatment of avalanche victims: Scoping review and 2023 recommendations of the international commission for mountain emergency medicine (ICAR MedCom)

INTRODUCTION

The International Commission for Mountain Emergency Medicine (ICAR MedCom) developed updated recommendations for the management of avalanche victims.

METHODS

ICAR MedCom created Population Intervention Comparator Outcome (PICO) questions and conducted a scoping review of the literature. We evaluated and graded the evidence using the American College of Chest Physicians system.

RESULTS

We included 120 studies including original data in the qualitative synthesis. There were 45 retrospective studies (38%), 44 case reports or case series (37%), and 18 prospective studies on volunteers (15%). The main cause of death from avalanche burial was asphyxia (range of all studies 65-100%). Trauma was the second most common cause of death (5-29%). Hypothermia accounted for few deaths (0-4%).

CONCLUSIONS AND RECOMMENDATIONS

For a victim with a burial time ≤ 60 minutes without signs of life, presume asphyxia and provide rescue breaths as soon as possible, regardless of airway patency. For a victim with a burial time > 60 minutes, no signs of life but a patent airway or airway with unknown patency, presume that a primary hypothermic CA has occurred and initiate cardiopulmonary resuscitation (CPR) unless temperature can be measured to rule out hypothermic cardiac arrest. For a victim buried > 60 minutes without signs of life and with an obstructed airway, if core temperature cannot be measured, rescuers can presume asphyxia-induced CA, and should not initiate CPR. If core temperature can be measured, for a victim without signs of life, with a patent airway, and with a core temperature < 30 °C attempt resuscitation, regardless of burial duration.

Effectiveness and Use of Avalanche Airbags in Mortality Reduction among Winter-Recreationists

RATIONALE FOR REVIEW

the number of backcountry skiers and snowboarder surged in the last years, especially during the COVID-19 pandemic, as ski resorts shut down. Inevitably, this led to an increase in avalanche-related injuries and death. As avalanche rescue device, avalanche airbags are increasingly becoming part of the standard winter mountaineering equipment. This study provides a review of available data and an updated perspective on avalanche airbags, discussing their function and efficacy to reduce mortality and their limitations.

KEY FINDINGS

causes of death in individuals caught by avalanches are multiple. Airbags seem to reduce mortality by decreasing chances of critical burial, the most determining risk factor. However, there is scarcity of reliable scientific research on the topic, and the way in which airbags reduce mortality and to what extent is still debated. Several elements seem to influence airbags efficacy, and their use still yields several limitations linked to manufacturing, proper use, users education, and risk compensation.

CONCLUSIONS/RECOMMENDATIONS

avalanche airbags seem to be an important tool in reducing mortality in backcountry expeditions. However, more research and standardized data collection is needed to fill the knowledge gap, mountain communities should promote adequate education of winter-recreationists on how to prevent and react to an avalanche, and on the correct use of airbags in combination with already available tools such as transceivers, probes and shovels, and manufacturing companies should ensure higher efficacy of the survival avalanche equipment for better prevention of burial, asphyxia, and trauma.

Quality Indicators for Avalanche Victim Management and Rescue

Decisions in the management and rescue of avalanche victims are complex and must be made in difficult, sometimes dangerous, environments. Our goal was to identify indicators for quality measurement in the management and rescue of avalanche victims. The International Commission for Mountain Emergency Medicine (ICAR MedCom) convened a group of internal and external experts. We used brainstorming and a five-round modified nominal group technique to identify the most relevant quality indicators (QIs) according to the National Quality Forum Measure Evaluation Criteria. Using a consensus process, we identified a set of 23 QIs to measure the quality of the management and rescue of avalanche victims. These QIs may be a valuable tool for continuous quality improvement. They allow objective feedback to rescuers regarding clinical performance and identify areas that should be the foci of further quality improvement efforts in avalanche rescue.

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.

Mortality in Different Mountain Sports Activities Primarily Practiced in the Winter Season-A Narrative Review

Annually, millions of people engage in mountain sports activities all over the world. These activities are associated with health benefits, but concurrently with a risk for injury and death. Knowledge on death rates is considered important for the categorization of high-risk sports in literature and for the development of effective preventive measures. The death risk has been reported to vary across different mountain sports primarily practiced in the summer season. To complete the spectrum, the aim of the present review is to compare mortality rates across different mountain sports activities primarily practiced in winter. A comprehensive literature search was performed on the death risk (mortality) during such activities, i.e., alpine (downhill) skiing, snowboarding, cross-country skiing, ski touring, and sledging. With the exception of ski touring (4.4 deaths per 1 million exposure days), the mortality risk was low across different winter sports, with small activity-specific variation (0.3–0.8 deaths per 1 million exposure days). Traumatic (e.g., falls) and non-traumatic (e.g., cardiac death) incidents and avalanche burial in ski tourers were the predominant causes of death. Preventive measures include the improvement of sport-specific skills and fitness, the use of protective gear, well-targeted and intensive training programs concerning avalanche hazards, and sports-medical counseling for elderly and those with pre-existing diseases.

Cut-off values of serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest: A retrospective multi-centre study

AIM

Evidence of existing guidelines for the on-site triage of avalanche victims is limited and adherence suboptimal. This study attempted to find reliable cut-off values for the identification of hypothermic avalanche victims with reversible out-of-hospital cardiac arrest (OHCA) at hospital admission. This may enable hospitals to allocate extracorporeal life support (ECLS) resources more appropriately while increasing the proportion of survivors among rewarmed victims.

METHODS

All avalanche victims with OHCA admitted to seven centres in Europe capable of ECLS from 1995 to 2016 were included. Optimal cut-off values, for parameters identified by logistic regression, were determined by means of bootstrapping and exact binomial distribution and served to calculate sensitivity, rate of overtriage, positive and negative predictive values, and receiver operating curves.

RESULTS

In total, 103 avalanche victims with OHCA were included. Of the 103 patients 61 (58%) were rewarmed by ECLS. Six (10%) of the rewarmed patients survived whilst 55 (90%) died. We obtained optimal cut-off values of 7 mmol/L for serum potassium and 30 °C for core temperature.

CONCLUSION

For in-hospital triage of avalanche victims admitted with OHCA, serum potassium accurately predicts survival. The combination of the cut-offs 7 mmol/L for serum potassium and 30 °C for core temperature achieved the lowest overtriage rate (47%) and the highest positive predictive value (19%), with a sensitivity of 100% for survivors. The presence of vital signs at extrication is strongly associated with survival. For further optimisation of in-hospital triage, larger datasets are needed to include additional parameters.

Cause of Death in Utah Avalanche Fatalities, 2006-2007 through 2017-2018 Winter Seasons

INTRODUCTION

Understanding patterns of avalanche fatalities can aid prevention and rescue strategies. In 2007, we published a report reviewing avalanche deaths in Utah between the 1989-1990 and 2005-2006 winter seasons. In the current report, we discuss Utah avalanche fatalities from the 2006-2007 to 2017-2018 seasons.

METHODS

Avalanche fatality data were obtained from the Utah Avalanche Center and Utah State Office of the Medical Examiner. Autopsy reports were reviewed to determine demographic information, type of autopsy (external vs internal), injuries, and cause of death.

RESULTS

Thirty-two avalanche deaths occurred in Utah during the study period. The mean (±SD) age of victims was 32±13 (8-54) y. Thirty victims (94%) were male and 2 (6%) were female. Seventy-two percent of deaths were from asphyxiation, 19% from trauma alone, and 9% from a combination of asphyxiation and trauma. Snowmobilers accounted for the largest percentage of avalanche fatalities (15 victims; 47%) during the 2007-2018 period.

CONCLUSIONS

Asphyxia continues to be the most prevalent killer in avalanche burial. Patterns of ongoing avalanche deaths continue to suggest that rapid recovery and techniques that prolong survival while buried may decrease fatality rates. Trauma is a significant factor in many avalanche fatalities. Education and technologies focused on reducing traumatic injuries such as improved education in techniques for avalanche risk avoidance and/or use of avalanche airbags may further decrease fatality rates. Snowmobilers represent an increasing percentage of Utah avalanche deaths and now make up the majority of victims; increased education targeting this demographic in the basics of avalanche rescue gear and avalanche rescue may also reduce fatalities.

On-Site Treatment of Snow Avalanche Victims: From Bench to Mountainside

The number of avalanche accidents involving winter recreationists has notably increased in recent decades due to the increasing popularity of outdoor winter activities. The International Liaison Committee on Cardiopulmonary Resuscitation, the International Commission for Mountain Emergency Medicine (ICAR Medcom), and the Wilderness Medical Society have recently published evidenced-based recommendations for the on-site treatment of snow avalanche victims. Despite these recommendations, recent studies found poor knowledge and compliance by both healthcare providers and laypersons. The aim of this nonsystematic review is to provide an updated overview of avalanche accident epidemiology, to present recent advances in snow avalanche pathophysiology, and to discuss recent advancements in on-site treatment of snow avalanche victims.

Causes of Death Among Avalanche Fatalities in Colorado: A 21-Year Review

INTRODUCTION

A better understanding of the nature of morbidity and mortality in avalanche accidents helps direct both rescue efforts as well as preventive strategies to reduce fatalities.

METHODS

We reviewed all avalanche fatalities from the avalanche years beginning in 1994 to 2015 in the state of Colorado, United States, using the database maintained by the Colorado Avalanche Information Center. For each fatality, we obtained the coroner's official determination of cause of death, and autopsy records if one was performed. We used these records to determine cause of death. Injury severity scores (0-75 scale) were calculated for those victims who underwent autopsy.

RESULTS

Mortality information was available for 110 fatalities occurring during the 21-year study period. Of these, 64 underwent autopsy. Asphyxia was the cause of death in 65% of fatalities (72/110). Trauma was the cause of death in 29% of the fatalities (32/110). Of these, the primary cause was multiple system trauma in 38% (12/32), head trauma in 31% (10/32), and spinal injuries in 19% (6/32). Of the victims who died of asphyxia and had autopsy, only 10% (4/42) also had significant trauma, defined as an injury severity score greater than 15. There were 6 fatalities from other causes, including hypothermia, drowning, and primary cardiac arrest. There was no correlation between trauma and mode of travel, avalanche type, or starting zone elevation.

CONCLUSIONS

Asphyxia was the primary cause of death in avalanche fatalities in Colorado during our study period. The incidence of fatal trauma was 29% and did not correlate with user group demographics or avalanche characteristics.

Does Avalanche Shovel Shape Affect Excavation Time: A Pilot Study

In Europe and North America, approximately 150 fatalities occur as a result of avalanches every year. However, it is unclear whether certain shovel shapes are more effective than others in snow removal during avalanche victim recovery. The objective was to determine the performance parameters with a developed standardized test using different shovel shapes and to determine sex-specific differences. Hence, several parameters were determined for clearing the snow from a snow filled box (15 men, 14 women). A flat (F) and a deep (D) shovel blade with the shaft connected straight (S) or in clearing mode (C) were used for the investigation of the shovel shapes FS, DC and the subsequent use of DC&DS. Mean snow mass shifted per unit time increased significantly from 1.50 kg/s with FS to 1.71 kg/s (14%) with DS and further to 1.79 kg/s (4%) with DC&DS for all participants. Snow mass shifted per unit time was 44% higher (p < 0.05) for men than for women. In excavation operations, the sex-specific physical performance should be taken into account. The results were limited to barely binding snow, because only with this snow did the tests show a high reliability.

Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents

To provide guidance to clinicians and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the prevention, rescue, and medical management of avalanche and nonavalanche snow burial victims. Recommendations are graded on the basis of quality of supporting evidence according to the classification scheme of the American College of Chest Physicians.

Contributing Causes of Injury or Death in Grain Entrapment, Engulfment, and Extrication

OBJECTIVES

Grain entrapments and engulfments are one of most common hazards associated with grain storage facilities, with over 1,140 such entrapments/engulfments documented since the 1970s. The objective of the study was to determine the factors that contribute to injury or death in grain entrapment, engulfment, and extrication cases.

METHODS

A literature review, including data contained in the Purdue Agricultural Confined Spaces Incident Database (PACSID), was conducted to determine the conditions that the body experiences during an entrapment or engulfment in grains and during extrication efforts.

RESULTS

Based on the review, the conditions a human body faces during an entrapment, engulfment, or extraction can be split into two broad categories-environmental and physiological/psychological. The environmental factors depend on the grain's properties, depth of entrapment or engulfment, position of the victim's body, and characteristics of the storage unit, which include the grain's lateral pressure, vertical pressure, and weight, as well as friction, oxygen availability and diffusion rate, and grain temperature. The physiological and psychological factors are related to the individual's age and physical and psychological conditions, and manifest themselves in terms of oxygen consumption, asphyxiation (including aspiration, lack of oxygen, compression or splinting of the thorax), blood flow, and heart rate.

CONCLUSION

Of all the above factors, a review of fatality data contained in the PACSID indicate that aspiration, asphyxiation, grain weight, and lateral pressure are most likely the primary cause of death for most entrapment victims. Research gaps found by this study include an understanding of the impact of lateral pressure on lung expansion and oxygen availability and consumption rate, and the need for more case studies to accurately determine cause of death.

Serum potassium concentration predicts brain hypoxia on CT after avalanche-induced cardiac arrest

BACKGROUND

Brain anoxia after complete avalanche burial and cardiac arrest (CA) may occur despite adequate on-site triage.

PURPOSE

To investigate clinical and biological parameters associated with brain hypoxia in a cohort of avalanche victims with whole body computed tomographic (CT) scan.

METHODS

Retrospective study of patients with CA and whole body CT scan following complete avalanche burial admitted in a level-I trauma center.

MAIN FINDINGS

Out of 19 buried patients with whole body CT scan, eight patients had refractory CA and 11 patients had pre-hospital return of spontaneous circulation. Six patients survived at hospital discharge and only two had good neurologic outcome. Twelve patients had signs of brain hypoxia on initial CT scan, defined as brain edema, loss of gray/white matter differentiation and/or hypodensity of basal ganglia. No clinical pre-hospital parameter was associated with brain anoxia. Serum potassium concentration at admission was higher in patients with brain anoxia as compared to patients with normal CT scan: 5.5 (4.1-7.2) mmol/L versus 3.3 (3.0-4.2) mmol/L, respectively (P<.01). A threshold of 4.35 mmol/L serum potassium had 100% specificity to predict brain anoxia on brain CT scan.

CONCLUSIONS

Serum potassium concentration had good predictive value for brain anoxia after complete avalanche burial. This finding further supports the use of serum potassium concentration for extracorporeal life support insertion at hospital admission in this context.

Risk of Avalanche Involvement in Winter Backcountry Recreation: The Advantage of Small Groups

OBJECTIVE

Avalanches are the primary hazard for winter backcountry recreationists and cause numerous deaths and injuries annually. Although recreationists usually travel in groups, there is little empirical knowledge on group-related risk factors. This study aims to explore the relative risk of avalanche accidents with respect to group size and to discuss underlying reasons for different risk levels.

METHODS

We compared backcountry usage data in regions in Switzerland and Italy with avalanche accident data in these regions.

RESULTS

We found higher avalanche risk for groups of 4 or more people and lower risk for people traveling alone and in groups of 2. The relative risk of group size 4, 5, and 6 was higher compared with the reference group size of 2 in the Swiss and Italian dataset. The relative risk for people traveling alone was not significantly different compared with the reference group size of 2 in the Italian dataset but was lower in the Swiss dataset.

CONCLUSIONS

These findings are in accordance with avalanche safety recommendations regarding the higher risk of large groups but not regarding lower risks of people traveling alone in avalanche terrain, which is not recommended and requires great caution. Further studies on backcountry usage are necessary to improve our understanding of human behavior and risk factors. New techniques (eg, video monitoring) may be useful for acquiring reliable data on backcountry usage.

Work of Breathing into Snow in the Presence versus Absence of an Artificial Air Pocket Affects Hypoxia and Hypercapnia of a Victim Covered with Avalanche Snow: A Randomized Double Blind Crossover Study

Presence of an air pocket and its size play an important role in survival of victims buried in the avalanche snow. Even small air pockets facilitate breathing. We hypothesize that the size of the air pocket significantly affects the airflow resistance and work of breathing. The aims of the study are (1) to investigate the effect of the presence of an air pocket on gas exchange and work of breathing in subjects breathing into the simulated avalanche snow and (2) to test whether it is possible to breathe with no air pocket. The prospective interventional double-blinded study involved 12 male volunteers, from which 10 completed the whole protocol. Each volunteer underwent two phases of the experiment in a random order: phase “AP”—breathing into the snow with a one-liter air pocket, and phase “NP”—breathing into the snow with no air pocket. Physiological parameters, fractions of oxygen and carbon dioxide in the airways and work of breathing expressed as pressure-time product were recorded continuously. The main finding of the study is that it is possible to breath in the avalanche snow even with no air pocket (0 L volume), but breathing under this condition is associated with significantly increased work of breathing. The significant differences were initially observed for end-tidal values of the respiratory gases (EtO₂ and EtCO₂) and peripheral oxygen saturation (SpO₂) between AP and NP phases, whereas significant differences in inspiratory fractions occurred much later (for F_IO₂) or never (for F_ICO₂). The limiting factor in no air pocket conditions is excessive increase in work of breathing that induces increase in metabolism accompanied by higher oxygen consumption and carbon dioxide production. The presence of even a small air pocket reduces significantly the work of breathing.

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.

Outcome of avalanche victims with out-of-hospital cardiac arrest

STUDY BACKGROUND

Previous studies focused on the outcome of avalanche victims with out-of-hospital cardiac arrest (OHCA) after long duration of burial (>35min); the outcome of victims with short duration (≤35min) remains obscure.

AIM OF THE STUDY

To investigate outcome of avalanche victims with OHCA.

METHODS

Retrospective analysis of avalanche victims with OHCA between 2008 and 2013 in the Tyrolean Alps.

RESULTS

55 avalanche victims were identified, 32 of whom were declared dead after extrication without cardiopulmonary resuscitation (CPR), all with long duration of burial. In the remaining 23 CPR was initiated at scene; three were partially and 20 completely buried, nine of whom suffered short and 11 long duration of burial. All nine victims with short duration of burial underwent restoration of spontaneous circulation (ROSC) at scene, four of them after bystander CPR, five after advanced life support by the emergency physician. Two patients with ROSC after short duration of burial and bystander CPR survived to hospital discharge with cerebral performance category 1. None of the 11 victims with long duration of burial survived to hospital discharge, although six were transported to hospital with ongoing CPR and three were supported with extracorporeal circulation.

CONCLUSIONS

In this case series survival with favourable neurological outcome was observed in avalanche victims with short duration of burial only if bystander CPR was immediately performed and ROSC achieved. Strategies for reducing avalanche mortality should focus on prompt extrication from the snow and immediate bystander CPR by uninjured companions.

Effect of head and face insulation on cooling rate during snow burial

OBJECTIVES

Avalanche victims are subjected to a number of physiological stressors during burial. We simulated avalanche burial to monitor physiological data and determine whether wearing head and face insulation slows cooling rate during snow burial. In addition, we sought to compare 3 different types of temperature measurement methods.

METHODS

Nine subjects underwent 2 burials each, 1 with head and face insulation and 1 without. Burials consisted of a 60-minute burial phase followed by a 60-minute rewarming phase. Temperature was measured via 3 methods: esophageal probe, ingestible capsule, and rectal probe.

RESULTS

Cooling and rewarming rates were not statistically different between the 2 testing conditions when measured by the 3 measurement methods. All temperature measurement methods correlated significantly.

CONCLUSIONS

Head and face insulation did not protect the simulated avalanche victim from faster cooling or rewarming. Because the 3 temperature measurement methods correlated, the ingestible capsule may provide an advantageous noninvasive method for snow burial and future hypothermia studies if interruptions in data transmission can be minimized.

Survival after avalanche-induced cardiac arrest

AIM

Criteria to prolong resuscitation after cardiac arrest (CA) induced by complete avalanche burial are critical since profound hypothermia could be involved. We sought parameters associated with survival in a cohort of victims of complete avalanche burial.

METHODS

Retrospective observational study of patients suffering CA on-scene after avalanche burial in the Northern French Alps between 1994 and 2013. Criteria associated with survival at discharge from the intensive care unit (ICU) were collected on scene and upon admission to Level-1 trauma center. Neurological outcome was assessed at 3 months using cerebral performance category score.

RESULTS

Forty-eight patients were studied. They were buried for a median time of 43 min (25-76 min; 25-75th percentiles) and had a pre-hospital body core temperature of 28.0°C (26.0-30.7). Eighteen patients (37.5%) had pre-hospital return of spontaneous circulation and 30 had refractory CA. Rewarming of 21 patients (43.7%) was performed using extracorporeal life support. Eight patients (16.7%) survived and were discharged from the ICU, three (6.3%) had favorable neurological outcome at 3 months. Pre-hospital parameters associated with survival were the presence of an air pocket and rescue collapse. On admission, survivors had lower serum potassium concentrations than non-survivors: 3.2 mmol/L (2.7-4.0) versus 5.6 mmol/L (4.2-8.0), respectively (P<0.01). They also had normal values for prothrombin and activated partial thromboplastin compared to non-survivors.

CONCLUSIONS

Our findings indicate that survival after avalanche burial and on-scene CA is rarely associated with favorable neurological outcome. Among criteria associated with survival, normal blood coagulation on admission warrants further investigation.

The effectiveness of avalanche airbags

AIM

Asphyxia is the primary cause of death among avalanche victims. Avalanche airbags can lower mortality by directly reducing grade of burial, the single most important factor for survival. This study aims to provide an updated perspective on the effectiveness of this safety device.

METHODS

A retrospective analysis of avalanche accidents involving at least one airbag user between 1994 and 2012 in Austria, Canada, France, Norway, Slovakia, Switzerland and the United States. A multivariate analysis was used to calculate adjusted absolute risk reduction and estimate the effectiveness of airbags on grade of burial and mortality. A univariate analysis was used to examine causes of non-deployment.

RESULTS

Binomial linear regression models showed main effects for airbag use, avalanche size and injuries on critical burial, and for grade of burial, injuries and avalanche size on mortality. The adjusted risk of critical burial is 47% with non-inflated airbags and 20% with inflated airbags. The adjusted mortality is 44% for critically buried victims and 3% for non-critically buried victims. The adjusted absolute mortality reduction for inflated airbags is -11 percentage points (22% to 11%; 95% confidence interval: -4 to -18 percentage points) and adjusted risk ratio is 0.51 (95% confidence interval: 0.29 to 0.72). Overall non-inflation rate is 20%, 60% of which is attributed to deployment failure by the user.

CONCLUSION

Although the impact on survival is smaller than previously reported, these results confirm the effectiveness of airbags. Non-deployment remains the most considerable limitation to effectiveness. Development of standardized data collection protocols is encouraged to facilitate further research.

Wilderness medicine

BACKGROUND

Human activity in wilderness areas has increased globally in recent decades, leading to increased risk of injury and illness. Wilderness medicine has developed in response to both need and interest.

METHODS

The field of wilderness medicine encompasses many areas of interest. Some focus on special circumstances (such as avalanches) while others have a broader scope (such as trauma care). Several core areas of key interest within wilderness medicine are discussed in this study.

RESULTS

Wilderness medicine is characterized by remote and improvised care of patients with routine or exotic illnesses or trauma, limited resources and manpower, and delayed evacuation to definitive care. Wilderness medicine is developing rapidly and draws from the breadth of medical and surgical subspecialties as well as the technical fields of mountaineering, climbing, and diving. Research, epidemiology, and evidence-based guidelines are evolving. A hallmark of this field is injury prevention and risk mitigation. The range of topics encompasses high-altitude cerebral edema, decompression sickness, snake envenomation, lightning injury, extremity trauma, and gastroenteritis. Several professional societies, academic fellowships, and training organizations offer education and resources for laypeople and health care professionals.

CONCLUSIONS

THE FUTURE OF WILDERNESS MEDICINE IS UNFOLDING ON MULTIPLE FRONTS: education, research, training, technology, communications, and environment. Although wilderness medicine research is technically difficult to perform, it is essential to deepening our understanding of the contribution of specific techniques in achieving improvements in clinical outcomes.

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

BACKGROUND

In North America and Europe ∼150 persons are killed by avalanches every year.

METHODS

The International Commission for Mountain Emergency Medicine (ICAR MEDCOM) systematically developed evidence-based guidelines and an algorithm for the management of avalanche victims using a worksheet of 27 Population Intervention Comparator Outcome questions. Classification of recommendations and level of evidence are ranked using the American Heart Association system.

RESULTS AND CONCLUSIONS

If lethal injuries are excluded and the body is not frozen, the rescue strategy is governed by the duration of snow burial and, if not available, by the victim's core-temperature. If burial time ≤35 min (or core-temperature ≥32 °C) rapid extrication and standard ALS is important. If burial time >35 min and core-temperature <32 °C, treatment of hypothermia including gentle extrication, full body insulation, ECG and core-temperature monitoring is recommended, and advanced airway management if appropriate. Unresponsive patients presenting with vital signs should be transported to a hospital capable of active external and minimally invasive rewarming such as forced air rewarming. Patients with cardiac instability or in cardiac arrest (with a patent airway) should be transported to a hospital for extracorporeal membrane oxygenation or cardiopulmonary bypass rewarming. Patients in cardiac arrest should receive uninterrupted CPR; with asystole, CPR may be terminated (or withheld) if a patient is lethally injured or completely frozen, the airway is blocked and duration of burial >35 min, serum potassium >12 mmol L(-1), risk to the rescuers is unacceptably high or a valid do-not-resuscitate order exists. Management should include spinal precautions and other trauma care as indicated.

Prehospital resuscitation of the buried avalanche victim

In North America and Europe, approximately 150 people die of avalanches per year, and fatalities are presumed to be many times higher in developing countries. Four factors are decisive for survival: grade of burial, duration of burial, presence of an air pocket and a free airway, and severity of trauma. According to Swiss data, the overall mortality rate with avalanche burial is 23%, but it largely depends on the grade of burial. While the mortality rate is 52.4% in completely buried (head below the snow) victims in the Swiss population, it is only 4.2% in partially buried (head free) victims. Additionally, survival in completely buried victims drops to 30% within the first 35 min, initially due to death from lethal trauma, followed by asphyxia in 20-35 min. Thereafter, survival decreases more gradually and victims who are not fatally injured and are able to breath under the snow slowly succumb to hypoxia, hypercapnia, and hypothermia. In the absence of fatal injuries, rescue strategies depend on the duration of burial and the victim's core temperature. With a burial time<35 min, survival depends on preventing asphyxia by rapid extrication, adequate airway management, and cardiopulmonary resuscitation. With a burial time>35 min, tackling hypothermia is of utmost importance. Therefore, gentle extrication and continuous core temperature and electrocardiogram monitoring are recommended. Pulseless victims with a patent airway and a core temperature<32°C should receive uninterrupted cardiopulmonary resuscitation and be transported to a hospital with extracorporeal rewarming facilities.

Prognostic factors in avalanche resuscitation: a systematic review

OBJECTIVE

Avalanche resuscitation will save lives if focussed on victims that have the potential to survive. The purpose of this systematic review was to examine 4 critical prognostic factors for burial victims in cardiac arrest.

METHODS

Time of burial, airway patency, core temperature and serum potassium level were analyzed as PICO (Patient/population, Intervention, Comparator, Outcome) questions within the 2010 Consensus on Science process of the International Liaison Committee on Resuscitation. The electronic databases of Medline via PubMed, EMBASE via OVID and the Cochrane Database of Systematic Reviews were searched using combinations of the search terms "avalanche", "air pocket", "hypothermia" and "serum potassium".

RESULTS

Of 1910 publications that were identified 30 were found relevant. The predictive value for survival of a short time of burial or a patent airway after 35 min of burial is supported by 10 retrospective case-control studies, 4 case series and 2 experimental studies, while no studies are neutral or opposed. A core temperature of less than 32 degrees C with a patent airway is supported by 2 retrospective case-control studies and 3 case series, while 10 studies are neutral. Serum potassium level is supported by 6 retrospective case-control studies and 3 case reports, while 3 retrospective case-control studies and 1 animal model are neutral.

CONCLUSION

After 35 min of burial, or where the core temperature is less than 32 degrees C, a patent airway is associated with survival to hospital discharge. A serum potassium of less than 7 mmol/L may be a valuable indicator for survival when other indicators are unclear. These findings should modify the current avalanche resuscitation scheme.

Patterns of death among avalanche fatalities: a 21-year review

BACKGROUND

Avalanches are a significant cause of winter recreational fatalities in mountain regions. The purpose of this study was to determine the relative contributions of trauma and asphyxia to avalanche deaths.

METHODS

We reviewed all avalanche fatalities between 1984 and 2005 that had been investigated by the offices of the British Columbia Coroners Service and the Chief Medical Examiner of Alberta. In addition, we searched the database of the Canadian Avalanche Centre for fatal avalanche details. We calculated injury severity scores for all victims who underwent autopsy.

RESULTS

There were 204 avalanche fatalities with mortality information over the 21-year study period. Of these, 117 victims underwent autopsy, and 87 underwent forensic external examination. Asphyxia caused 154 (75%) deaths. Trauma caused 48 (24%) deaths, with the rate of death from trauma ranging from 9% (4/44) for snowmobilers to 42% (5/12) for ice climbers. In addition, 13% (12/92) of the asphyxia victims who underwent autopsy had major trauma, defined as an injury severity score of greater than 15. Only 48% (23/48) of victims for whom trauma was the primary cause of death had been completely buried.

INTERPRETATION

Asphyxia and severe trauma caused most avalanche fatalities in western Canada. The relative rates differed between snowmobilers and those engaged in other mountain activities. Our findings should guide recommendations for safety devices, safety measures and resuscitation.