Prognostic factors in avalanche resuscitation: a systematic review

Prevalence of airway patency and air pocket in critically buried avalanche victims - a scoping review

INTRODUCTION

Survival of critically buried avalanche victims is directly dependent on the patency of the airway and the victims' ability to breathe. While guidelines and avalanche research have consistently emphasized on the importance of airway patency, there is a notable lack of evidence regarding its prevalence.

OBJECTIVE

The aim of this review is to provide insight into the prevalence of airway patency and air pocket in critically buried avalanche victims.

METHODS

A scoping review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline extension for scoping reviews. MEDLINE and Cochrane databases, as well as additional manual searching was performed to identify literature reporting data on airway patency and the presence of an air pocket in critically buried avalanche victims. After eliminating duplicates, we screened abstracts and main texts to identify eligible studies.

RESULTS

Of 4,109 studies identified 154 were eligible for further screening. Twenty-four publications and three additional data sources with a total number of 566 cases were included in this review. The proportion of short-term (< 35 min) to long-term burial (≥ 35 min) in the analysed studies was 19% and 66%, respectively. The burial duration remained unknown in 12% of cases. The prevalence of airway patency in critically buried avalanche victims was 41% while that of airway obstruction was 12%, with an overall rate of reporting as low as 50%. An air pocket was present in 19% of cases, absent in 46% and unknown in 35% of the cases.

CONCLUSION

The present study found that in critically buried avalanche victims patent airways were more than three times more prevalent than obstructed, with the airway status reported only in half of the cases. This high rate of airway patency supports the ongoing development and the effectiveness of avalanche rescue systems which oppose asphyxiation in critically buried avalanche victims. Further effort should be done to improve the documentation of airway patency and the presence of an air pocket in avalanche victims and to identify factors affecting the rate of airway obstruction.

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.

Termination of Cardiopulmonary Resuscitation in Mountain Rescue: A Scoping Review and ICAR MedCom 2023 Recommendations

Lugnet, Viktor, Miles McDonough, Les Gordon, Mercedes Galindez, Nicolas Mena Reyes, Alison Sheets, Ken Zafren, and Peter Paal. Termination of cardiopulmonary resuscitation in mountain rescue: a scoping review and ICAR MedCom 2023 recommendations. High Alt Med Biol. 24:274-286, 2023. Background: In 2012, the International Commission for Mountain Emergency Medicine (ICAR MedCom) published recommendations for termination of cardiopulmonary resuscitation (CPR) in mountain rescue. New developments have necessitated an update. This is the 2023 update for termination of CPR in mountain rescue. Methods: For this scoping review, we searched the PubMed and Cochrane libraries, updated the recommendations, and obtained consensus approval within the writing group and the ICAR MedCom. Results: We screened a total of 9,102 articles, of which 120 articles met the inclusion criteria. We developed 17 recommendations graded according to the strength of recommendation and level of evidence. Conclusions: Most of the recommendations from 2012 are still valid. We made minor changes regarding the safety of rescuers and responses to primary or traumatic cardiac arrest. The criteria for termination of CPR remain unchanged. The principal changes include updated recommendations for mechanical chest compression, point of care ultrasound (POCUS), extracorporeal life support (ECLS) for hypothermia, the effects of water temperature in drowning, and the use of burial times in avalanche rescue.

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.

Cooling to Hypothermic Circulatory Arrest by Immersion vs. Cardiopulmonary Bypass (CPB): Worse Outcome After Rewarming in Immersion Cooled Pigs

Introduction

Cooling by cardiopulmonary bypass (CPB) to deep hypothermic cardiac arrest (HCA) for cardiac surgical interventions, followed by CPB-rewarming is performed on a routine basis with relatively low mortality. In contrast, victims of deep accidental hypothermia rewarmed with CPB generally have a much worse prognosis. Thus, we have developed an intact pig model to compare effects on perfusion pressures and global oxygen delivery (DO₂) during immersion cooling versus cooling by CPB. Further, we compared the effects of CPB-rewarming between groups, to restitute cardiovascular function, brain blood flow, and brain metabolism.

Materials and Methods

Total sixteen healthy, anesthetized juvenile (2–3 months) castrated male pigs were randomized in a prospective, open placebo-controlled experimental study to immersion cooling (IMM_c, n = 8), or cooling by CPB (CPB_c, n = 8). After 75 minutes of deep HCA in both groups, pigs were rewarmed by CPB. After weaning from CPB surviving animals were observed for 2 h before euthanasia.

Results

Survival rates at 2 h after completed rewarming were 4 out of 8 in the IMM_c group, and 8 out of 8 in the CPB_c group. Compared with the CPB_c-group, IMM_c animals showed significant reduction in DO₂, mean arterial pressure (MAP), cerebral perfusion pressure, and blood flow during cooling below 25°C as well as after weaning from CPB after rewarming. After rewarming, brain blood flow returned to control in CPB_c animals only, and brain micro dialysate-data showed a significantly increase in the lactate/pyruvate ratio in IMM_c vs. CPB_c animals.

Conclusion

Our data indicate that, although global O₂ consumption was independent of DO₂, regional ischemic damage may have taken place during cooling in the brain of IMM_c animals below 25°C. The need for prolonged extracorporeal membrane oxygenation (ECMO) should be considered in all victims of accidental hypothermic arrest that cannot be weaned from CPB immediately after rewarming.

Solid Organ Donation From Brain-dead Donors With Cardiorespiratory Arrest After Snow Avalanche Burial: A Retrospective Single-center Study

BACKGROUND

Complete snow avalanche burial is associated with high mortality. The aim of this study was to assess the feasibility and incidence of organ retrieval in brain-dead donors following cardiorespiratory arrest due to avalanche burial and to evaluate the function of transplanted organs.

METHODS

The transplant registry of the Medical University of Innsbruck was searched for organ donors with a history of avalanche burial, and the function and survival of transplanted organs were assessed.

RESULTS

Thirty-three organs were procured from eight donors and 31 organs (13 kidneys, 6 livers, 3 pancreases, 5 hearts, and 4 lungs) were ultimately transplanted. Allograft and recipient 1-y survival were 100% and both initial and long-term graft function were good. Only one-third of all avalanche victims who died in the intensive care unit with signs of irreversible hypoxic brain injury became organ donors.

CONCLUSIONS

Initial experience from this retrospective study suggests that organs from brain-dead avalanche victims can be transplanted with good results. Starting a Donation after Circulatory Determination of Death program might be an option for increasing the number of organ donations from avalanche victims with irreversible hypoxic brain injury.

Prevention of Hypothermia in the Aftermath of Natural Disasters in Areas at Risk of Avalanches, Earthquakes, Tsunamis and Floods

Throughout history, accidental hypothermia has accompanied natural disasters in cold, temperate, and even subtropical regions. We conducted a non-systematic review of the causes and means of preventing accidental hypothermia after natural disasters caused by avalanches, earthquakes, tsunamis, and floods. Before a disaster occurs, preventive measures are required, such as accurate disaster risk analysis for given areas, hazard mapping and warning, protecting existing structures within hazard zones to the greatest extent possible, building structures outside hazard zones, and organising rapid and effective rescue. After the event, post hoc analyses of failures, and implementation of corrective actions will reduce the risk of accidental hypothermia in future disasters.

Pediatric Hypothermia: An Ambiguous Issue

Hypothermia in pediatrics is mainly about small body size. The key thermal factor here is the large surface-to-volume ratio. Although small mammals, including human infants and children, are adapted to higher heat losses through their elevated metabolic rate and thermogenic capacity, they are still at risk of hypothermia because of a small regulatory range and an impending metabolic exhaustion. However, some small mammalian species (hibernators) use reduced metabolic rates and lowered body temperatures as adaptations to impaired energy supply. Similar to nature, hypothermia has contradictory effects in clinical pediatrics as well: In neonates, it is a serious risk factor affecting respiratory adaptation in term and developmental outcome in preterm infants. On the other hand, it is an important self-protective response to neonatal hypoxia and an evidence-based treatment option for asphyxiated babies. In children, hypothermia first enabled the surgical repair of congenital heart defects and promotes favorable outcome after ice water drowning. Yet, it is also a major threat in various prehospital and clinical settings and has no proven therapeutic benefit in pediatric critical care. All in all, pediatric hypothermia is an ambiguous issue whose harmful or beneficial effects strongly depend on the particular circumstances.

On-Site Medical Management of Avalanche Victims-A Narrative Review

Avalanche accidents are common in mountain regions and approximately 100 fatalities are counted in Europe each year. The average mortality rate is about 25% and survival chances are mainly determined by the degree and duration of avalanche burial, the patency of the airway, the presence of an air pocket, snow characteristics, and the severity of traumatic injuries. The most common cause of death in completely buried avalanche victims is asphyxia followed by trauma. Hypothermia accounts for a minority of deaths; however, hypothermic cardiac arrest has a favorable prognosis and prolonged resuscitation and extracorporeal rewarming are indicated. In this article, we give an overview on the pathophysiology and on-site management of avalanche victims.

Rewarming From Hypothermic Cardiac Arrest Applying Extracorporeal Life Support: A Systematic Review and Meta-Analysis

Introduction: This systematic review and meta-analysis aims at comparing outcomes of rewarming after accidental hypothermic cardiac arrest (HCA) with cardiopulmonary bypass (CPB) or/and extracorporeal membrane oxygenation (ECMO). Material and Methods: Literature searches were limited to references with an abstract in English, French or German. Additionally, we searched reference lists of included papers. Primary outcome was survival to hospital discharge. We assessed neurological outcome, differences in relative risks (RR) of surviving, as related to the applied rewarming technique, sex, asphyxia, and witnessed or unwitnessed HCA. We calculated hypothermia outcome prediction probability score after extracorporeal life support (HOPE) in patients in whom we found individual data. P < 0.05 considered significant. Results: Twenty-three case observation studies comprising 464 patients were included in a meta-analysis comparing outcomes of rewarming with CPB or/and ECMO. One-hundred-and-seventy-two patients (37%) survived to hospital discharge, 76 of 245 (31%) after CPB and 96 of 219 (44 %) after ECMO; 87 and 75%, respectively, had good neurological outcomes. Overall chance of surviving was 41% higher (P = 0.005) with ECMO as compared with CPB. A man and a woman had 46% (P = 0.043) and 31% (P = 0.115) higher chance, respectively, of surviving with ECMO as compared with CPB. Avalanche victims had the lowest chance of surviving, followed by drowning and people losing consciousness in cold environments. Assessed by logistic regression, asphyxia, unwitnessed HCA, male sex, high initial body temperature, low pH and high serum potassium (s-K+) levels were associated with reduced chance of surviving. In patients displaying individual data, overall mean predictive surviving probability (HOPE score; n = 134) was 33.9 ± 33.6% with no significant difference between ECMO and CPB-treated patients. We also surveyed 80 case reports with 96 victims of HCA, who underwent resuscitation with CPB or ECMO, without including them in the meta-analysis. Conclusions: The chance of surviving was significantly higher after rewarming with ECMO, as compared to CPB, and in patients with witnessed compared to unwitnessed HCA. Avalanche victims had the lowest probability of surviving. Male sex, high initial body temperature, low pH, and high s-K+ were factors associated with low surviving chances.

Effects of Climate Change on Avalanche Accidents and Survival

Avalanches are major natural hazards in snow-covered mountains, threatening people and infrastructure. With ongoing climate change, the frequency and types of snow avalanches may change, affecting the rates of avalanche burial and survival. With a wetter and warmer snow climate, consequences of burial may become more severe. In this review, we assess the potential effects of climate change on the frequency and characteristics of avalanches. We then discuss how these changes might affect the survival rates of subjects buried by avalanches and might influence the responses of search and rescue (SAR) teams and health care providers. While climate change is inevitable, the effects on avalanches remain elusive. The frequency of human triggered avalanches may not change, because this depends largely on the number and behavior of winter recreationists. Blunt trauma and secondary injuries will likely become more frequent as terrain roughness is expected to rise and snow cover to become thinner. Higher snow densities in avalanche debris will likely interfere with the respiration of completely buried victims. Asphyxia and trauma, as causes of avalanche death, may increase. It is unlikely that SAR and health care providers involved in avalanche rescue will have to change their strategies in areas where they are already established. The effects of climate change might foster the expansion of mitigation strategies and the establishment of mountain rescue services in areas subject to increased avalanche hazards caused by changes in snow cover and land use.

Hypoxia and hypercapnia effects on cerebral oxygen saturation in avalanche burial: A pilot human experimental study

BACKGROUND

A sufficient supply of oxygen is crucial to avoid hypoxic cardiac arrest and brain damage within 30 min in completely-buried avalanche victims. Snow density influences levels of hypoxia and hypercapnia. The goal of this study was to investigate the effects of hypoxia and hypercapnia on cerebral oxygenation (ScO₂) in humans breathing into an artificial air pocket.

METHODS

Each subject breathed into a closed system (air-tight face mask - plastic tube - snow air-pocket of 4 L) up to 30 min. Each subject performed three tests in different snow densities. ScO₂ was measured by a near-infrared spectroscopy (NIRS) device. Measurements included peripheral oxygen saturation (SpO₂), end-tidal carbon dioxide (ETCO₂), air pocket gases and blood gases. Snow density was assessed via standard methods and micro-computed tomography. Based on predetermined criteria, tests were classified based on whether they were terminated before 30 min and the reason for termination. The categories were: completed tests (30 min), tests terminated before 30 min when SpO₂ dropped to ≤75% and tests that were terminated before 30 min by requests of the subjects. General linear models were used to compare termination groups for changes in ScO₂, ETCO₂, SpO₂ and air pocket gases, and a multivariate analysis was used to detect factor independent effects on ScO₂.

RESULTS

ScO₂ was decreased in the group in which the tests were terminated for SpO₂ ≤ 75% caused by a decrease in oxygen supply in high snow densities. In the completed tests, an increase in ScO₂ occurred despite decreased oxygen supply and decreased carbon dioxide removal.

CONCLUSIONS

Our data show that ScO₂ determined by NIRS was not always impaired in humans breathing into an artificial air pocket despite decreased oxygen supply and decreased carbon dioxide removal. This may indicate that in medium to low snow densities brain oxygenation can be sufficient, which may reflect the initial stage of the triple H (hypothermia, hypoxia, and hypercapnia) syndrome. In high snow densities, ScO₂ showed a significant decrease caused by a critical decrease in oxygen supply. This could lead to a higher risk of hypoxic cardiac arrest and brain damage.

Total TauProtein as Investigated by Cerebral Microdialysis Increases in Hypothermic Cardiac Arrest: A Pig Study

The understanding and neurological prognostication of hypoxic ischemic encephalopathy (HIE) after hypothermic cardiac arrest (CA) is limited. Recent data suggest that the protein tau (total tau) might be a useful marker for outcome in patients with HIE. This translational porcine study aimed to analyze brain physiology in relation to total tau protein release during hypothermic CA. Eight domestic pigs were studied as part of a prospective porcine study using cerebral microdialysis (CMD). CMD samples for tau analysis were collected at baseline, after reaching the targeted core temperature of 28°C (hypothermia), after hypoxic hypercapnia (partial asphyxia), and finally 20 minutes after cardiopulmonary resuscitation. CMD-total tau-protein was analyzed using enzyme-linked immunosorbent essay. Cerebral tau protein was slightly elevated at baseline most likely due to an insertion trauma, remained stable during hypercapnic hypoxia, and significantly (p = 0.009) increased in 8/8 pigs during resuscitation to 1335 pg/mL (interquartile range: 705-2100). CMD-tau release was associated with lower levels of brain tissue oxygen tension (p = 0.011), higher CMD-lactate/pyruvate ratio, higher CMD-lactate, CMD-glutamate, and CMD-glycerol levels (p < 0.001, respectively), but not with cerebral perfusion pressure, intracranial pressure, or CMD-glucose levels. This study demonstrates an immediate tau protein release accompanied by deranged cerebral metabolism and decreased brain tissue oxygen tension during mechanical resuscitation in hypothermic CA. Understanding tau physiology and release kinetics is important for the design and interpretation of studies investigating tau as a biomarker of HIE.

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.

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.

Successful resuscitation for cardiac arrest due to severe accidental hypothermia accompanied by mandibular rigidity: a case of cold stiffening mimicking rigor mortis

Background

In cases of severe accidental hypothermia, it was recommended that resuscitation should be continued until the patient has rewarmed, as hypothermia itself can preserve cerebral function, and hypothermic cardiac arrest is reversible. During cardiopulmonary resuscitation for normothermic patients, muscle rigidity suggests the initiation of postmortem changes such as rigor mortis and can lead to the termination of resuscitation. Currently, the prognosis of cardiac arrest due to severe accidental hypothermia accompanied by rigidity is unknown.

Case presentation

A 29-year-old woman was found unresponsive near a snowy mountain trail. Upon discovery, she was found to be in cardiac arrest with an initial asystole rhythm and exhibited mandibular rigidity. On admission, her core temperature was 22 °C. Although cardiac arrest continued, and she showed no response to normal resuscitation, blood gas analysis revealed that her initial serum potassium level was 5.4 mmol/L. Extracorporeal membrane oxygenation (ECMO) for systemic perfusion and rewarming was initiated. After ECMO was introduced, return of spontaneous circulation was achieved. She showed no neurological impairments at discharge.

Conclusions

Muscle rigidity does not rule out the possibility of resuscitation in patients with severe accidental hypothermia under cardiac arrest. Serum potassium levels may assist in deciding whether ECMO should be introduced, even if a patient is in asystole. This knowledge may help emergency physicians to save the lives of such patients.

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.

Prehospital management and outcome of avalanche patients with out-of-hospital cardiac arrest: a retrospective study in Tyrol, Austria

AIM

The aim of this study is to describe the prehospital management and outcome of avalanche patients with out-of-hospital cardiac arrest in Tyrol, Austria, for the first time since the introduction of international guidelines in 1996.

PATIENTS AND METHODS

This study involved a retrospective analysis of all avalanche accidents involving out-of-hospital cardiac arrest between 1996 and 2009 in Tyrol, Austria.

RESULTS

A total of 170 completely buried avalanche patients were included. Twenty-eight victims were declared dead at the scene. Of 34 patients with short burial, cardiopulmonary resuscitation (CPR) was performed in 27 (79%); 15 of these patients (56%) were transported to hospital with ongoing CPR and four patients were rewarmed with extracorporeal circulation; no patient survived. Of 108 patients with long burial, 49 patients had patent or unknown airway status; CPR was performed in 25 of these patients (51%) and 14 patients (29%) were transported to hospital. Four patients were rewarmed, but only one patient with witnessed cardiac arrest survived. Since the introduction of guidelines in 1996, there has been a marginally significant increase in the rate of documenting airway assessment, but no change in documenting the duration of burial or CPR.

CONCLUSION

CPR is continued to hospital admission in patients with short burial and asphyxial cardiac arrest, but withheld or terminated at the scene in patients with long burial and possible hypothermic cardiac arrest. Insufficient transfer of information from the accident site to the hospital may partially explain the poor outcome of avalanche victims with out-of-hospital cardiac arrest treated with emergency cardiac care.

Identification of the technical and medical requirements for HEMS avalanche rescue missions through a 15-year retrospective analysis in a HEMS in Switzerland: a necessary step for quality improvement

BACKGROUND

Avalanche rescues mostly rely on helicopter emergency medical services (HEMS) and include technical rescue and complex medical situations under difficult conditions. The adequacy of avalanche victim management has been shown to be unexpectedly low, suggesting the need for quality improvement. We analyse the technical rescue and medical competency requirements of HEMS crewmembers for avalanche rescue missions, as well as their clinical exposure. The study aims to identify areas that should be the focus of future quality improvement efforts.

METHODS

This 15-year retrospective study of avalanche rescue by the Swiss HEMS Rega includes all missions where at least one patient had been caught by an avalanche, found within 24 h of the alarm being raised, and transported.

RESULTS

Our analyses included 422 missions (596 patients). Crews were frequently confronted with technical rescue aspects, including winching (29%) and patient location and extrication (48%), as well as multiple casualty accidents (32%). Forty-seven percent of the patients suffered potential or overt vital threat; 29% were in cardiac arrest. The on-site medical management of the victims required a large array of basic and advanced medical skills. Clinical exposure was low, as 56% of the physicians were involved in only one avalanche rescue mission over the study period.

CONCLUSIONS

Our data provide a solid baseline measure and valuable starting point for improving our understanding of the challenges encountered during avalanche rescue missions. We further suggest QI interventions, that might be immediately useful for HEMS operating under similar settings. A coordinated approach using a consensus process to determine quality indicators and a minimal dataset for the specific setting of avalanche rescue would be the logical next step.

Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia

Accidental hypothermia is an unintentional drop in core temperature to 35°C or below. Core temperature is best measured by esophageal probe. If core temperature cannot be measured, the degree should be estimated using clinical signs. Treatment is to protect from further heat loss, minimize afterdrop, and prevent cardiovascular collapse during rescue and resuscitation. The patient should be handled gently, kept horizontal, insulated, and actively rewarmed. Active rewarming is also beneficial in mild hypothermia but passive rewarming usually suffices. Cardiopulmonary resuscitation should be performed if there are no contraindications to resuscitation. CPR may be delayed or intermittent.

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.

Outcome After Rewarming From Accidental Hypothermia by Use of Extracorporeal Circulation

BACKGROUND

Accidental hypothermia with arrested circulation remains a condition associated with high mortality. In our institution, extracorporeal circulation (ECC) rewarming has been the cornerstone in treating such patients since 1987. We here explore characteristics and outcomes of this treatment, to identify significant merits and challenges from 3 decades of experience in ECC rewarming.

METHODS

Sixty-nine patients rewarmed by ECC during the period from December 1987 to December 2015 were analyzed. One patient was excluded from the analyses because of combined traumatic cerebral injury. The analysis was focused on patient characteristics, treatment procedures, and outcomes were focused. Survivors were evaluated according to the cerebral performance categories scale. Simple statistics with nonparametric tests and χ² tests were used. Median value and range are reported.

RESULTS

Median age was 30 years (minimum 1.5, maximum 76), and the cause of accidental hypothermia was cold exposure (27.9%), avalanche (5.9%), and immersion/submersion accidents (66.2%). Eighteen patients survived (26.5%). The survival rate did not improve during the years. Survivors had lower serum potassium (p = 0.002), higher pH (p = 0.03), lower core temperature (p = 0.02), and shorter cardiopulmonary resuscitation time (p = 0.001), but ranges were wide. Although suspected primary hypoxia and hypothermia were associated with lower survival, we observed a 10.5% survival of these victims. Sixteen survivors had good outcome (cerebral performance category 1 or 2), whereas 2 patients with suspected primary hypoxia survived with severe cerebral disability (cerebral performance category 3).

CONCLUSIONS

Despite extended experience with ECC rewarming, improved handling strategies, and intensive care, no overall improvement in survival was observed. Good outcome was observed even among patients with a dismal prognosis.

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.

Is extracorporeal rewarming indicated in avalanche victims with unwitnessed hypothermic cardiorespiratory arrest?

International guidelines recommend using extracorporeal rewarming in all hypothermic avalanche victims with prolonged cardiac arrest if they have patent airways and a plasma potassium level≤12 mmol/L. The aim of this study was to evaluate outcome data to determine if available experience with extracorporeal rewarming of avalanche victims supports this recommendation. At Innsbruck Medical University Hospital, 28 patients with hypothermic cardiac arrest following an avalanche accident were resuscitated using extracorporeal circulation. Of these patients, 25 were extricated from the snow masses with no vital signs and did not survive to hospital discharge. Three patients had witnessed cardiac arrest after extrication and a core temperature of 21.7°C, 22°C, and 24.0°C, two of whom survived long-term with full neurological recovery. A search of the literature revealed only one asystolic avalanche victim with unwitnessed hypothermic cardiac arrest (core temperature 19°C) surviving long-term. All other avalanche victims in the medical literature surviving prolonged hypothermic cardiac arrest suffered witnessed arrest after extrication with a core temperature below 24°C. Our results suggest that prognosis of hypothermic avalanche victims with unwitnessed asystolic cardiac arrest and a core temperature>24°C is extremely poor. Available outcome data do not support the use of extracorporeal rewarming in these patients.

Wilderness Medical Society practice guidelines for the out-of-hospital evaluation and treatment of accidental hypothermia: 2014 update

To provide guidance to clinicians, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations. This is an updated version of the original Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia published in Wilderness & Environmental Medicine 2014;25(4):425-445.

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.

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

To provide guidance to clinicians, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations.

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.

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.

Emergency medical helicopter operations for avalanche accidents

BACKGROUND

In the European Alps emergency medical helicopter services are regularly involved in avalanche rescue missions. How the helicopter emergency medical system best supports avalanche rescue missions is controversial.

AIM OF THE STUDY

To study advantages and limitations of the early dispatch of emergency medical helicopters after avalanche accidents.

METHODS

Data on rescue mission characteristics and patterns and severity of medical emergencies were obtained for 221 helicopter avalanche rescue missions performed in the Austrian province of Tyrol between October 2008 and June 2011.

RESULTS

A buried avalanche victim had to be searched for in only 12 (5.5%) of the 221 rescue missions, whereas medical emergencies were encountered at the scene in 24 missions (11%). Survival rate for totally buried victims extricated after helicopter arrival was significantly lower than for victims extricated before helicopter arrival (19% versus 74%, p=0.0002). In 124 missions (56%) no victim was present at the scene when the helicopter arrived. Medical emergencies involved normothermic cardiac arrest (n=11), severe accidental hypothermia (n=6), critical trauma (n=7) and hypothermia combined with critical trauma (n=1). Survival rate at hospital discharge was 27% for arrested normothermic patients and 50% for trauma and hypothermia patients.

CONCLUSIONS

Medical emergencies are encountered at avalanche scenes twice as often as there is need to search for totally buried victims, clearly supporting the immediate dispatch of medical crew members to the accident site. The high rate of emergency medical helicopter operations to avalanche incidents where no victim is injured or buried may be characteristic for densely populated mountainous regions and can be reduced by a restrictive dispatch policy after avalanche accidents without clear information about human involvement.

Factors affecting survival from avalanche burial--a randomised prospective porcine pilot study

BACKGROUND AND AIM

The majority of avalanche victims who sustain complete burial die within 35min due to asphyxia and injuries. After 35min, survival is possible only in the presence of a patent airway, and an accompanying air pocket around the face may improve survival. At this stage hypothermia is assumed to be an important factor for survival because rapid cooling decreases oxygen consumption; if deep hypothermia develops before cardiac arrest, hypothermia may be protective and prolong the time that cardiac arrest can be survived. The aim of the study was to investigate the combined effects of hypoxia, hypercapnia and hypothermia in a porcine model of avalanche burial.

METHODS

Eight piglets were anaesthetised, intubated and buried under snow, randomly assigned to an air pocket (n=5) or ambient air (n=3) group.

RESULTS

Mean cooling rates in the first 10min of burial were -19.7±4.7°Ch(-1) in the air pocket group and -13.0±4.4°Ch(-1) in the ambient air group (P=0.095); overall cooling rates between baseline and asystole were -4.7±1.4°Ch(-1) and -4.6±0.2°Ch(-1) (P=0.855), respectively. In the air pocket group cardiac output (P=0.002), arterial oxygen partial pressure (P=0.001), arterial pH (P=0.002) and time to asystole (P=0.025) were lower, while arterial carbon dioxide partial pressure (P=0.007) and serum potassium (P=0.042) were higher compared to the ambient air group.

CONCLUSION

Our results demonstrate that hypothermia may develop in the early phase of avalanche burial and severe asphyxia may occur even in the presence of an air pocket.