Prehospital resuscitation of the buried avalanche victim

Alternative techniques for cardiopulmonary resuscitation in extreme environments - A scoping review

Background

Cardiopulmonary resuscitation (CPR) is essential for saving lives during cardiac arrest, but performing CPR in extreme environments poses unique challenges. In scenarios ranging from hypogravity or microgravity to confined spaces like aeroplanes and underwater scenarios, traditional CPR techniques may be inadequate. This scoping review aims to identify alternative chest compression techniques, synthesise current knowledge, and pinpoint research gaps in resuscitation for cardiac arrest in extreme conditions.

Methods

PubMed and the Cochrane Register of Controlled Trials as well as the website of ResearchGate was searched to identify relevant literature. Studies were eligible for inclusion if they evaluated alternative chest compression techniques, including manual or mixed CPR approaches, whilst assessing feasibility and effectiveness based on compression depth, rate, and/or impact on rescuer effort.

Results

The database search yielded 9499 references. After screening 26 studies covering 6 different extreme environments were included (hypogravity: 2; microgravity: 9, helicopter: 1, aeroplane: 1, confined space: 11; avalanche: 2). 13 alternative chest compression techniques were identified, all of which tested using manikins to simulate cardiac arrest scenarios.

Conclusion

To address the unique challenges in extreme environments, novel CPR techniques are emerging. However, evidence supporting their effectiveness remains limited.

Advancing the scientific study of prehospital mass casualty response through a Translational Science process: the T1 scoping literature review stage

PURPOSE

The European Union Horizon 2020 research and innovation funding program awarded the NIGHTINGALE grant to develop a toolkit to support first responders engaged in prehospital (PH) mass casualty incident (MCI) response. To reach the projects' objectives, the NIGHTINGALE consortium used a Translational Science (TS) process. The present work is the first TS stage (T1) aimed to extract data relevant for the subsequent modified Delphi study (T2) statements.

METHODS

The authors were divided into three work groups (WGs) MCI Triage, PH Life Support and Damage Control (PHLSDC), and PH Processes (PHP). Each WG conducted simultaneous literature searches following the PRISMA extension for scoping reviews. Relevant data were extracted from the included articles and indexed using pre-identified PH MCI response themes and subthemes.

RESULTS

The initial search yielded 925 total references to be considered for title and abstract review (MCI Triage 311, PHLSDC 329, PHP 285), then 483 articles for full reference review (MCI Triage 111, PHLSDC 216, PHP 156), and finally 152 articles for the database extraction process (MCI Triage 27, PHLSDC 37, PHP 88). Most frequent subthemes and novel concepts have been identified as a basis for the elaboration of draft statements for the T2 modified Delphi study.

CONCLUSION

The three simultaneous scoping reviews allowed the extraction of relevant PH MCI subthemes and novel concepts that will enable the NIGHTINGALE consortium to create scientifically anchored statements in the T2 modified Delphi study.

Experimental study on individual risk in crowds based on exerted force and human perceptions

Frequent and intense interactions between individuals inevitably occur in crowd disasters. Previous studies indicate that the primary risk evaluation parameters for individuals in crowds during these interactions are exerted force and its duration. In this study, a series of controlled laboratory experiments simulating static and fluctuant loads were conducted to obtain real-time exerted force data and the associated individual subjective feelings. An individual risk evaluation method is then established to assign a specific individual risk value to each data set of exerted force and its duration according to the individuals' feelings. This method divides the range of risk value into three zones: comfortable zone, uncomfortable zone and crisis zone. The transition from an uncomfortable zone to crisis zone is not a single numerical value but a range that considers individual differences. The method presented in this paper can assist in developing pedestrian simulation models as well as managing crowd events. Practitioner summary: Accident surveys indicate that casualties and injuries usually occur under a long-term static load or heavy dynamic load. We tested human body extrusion experiments in four conditions, measured the real-time load intensity and duration of the individual's action on the thoracic cavity during the mutual extrusion process, and an individual risk evaluation method has been established based on the force exerted on the body and its duration to prevent crowd disasters. Abbreviations: NIST: National Institute of Standards and Technology; IREM: individual risk evaluation method; CPR: cardiopulmonary resuscitation.

Cardiac Arrest in Special Circumstances-Recent Advances in Resuscitation

BACKGROUND

Cardiopulmonary resuscitation (CPR) in special circumstances includes the emergency intervention for special causes, special environments, and special patients. Special causes cover the potential reversible causes of cardiac arrest that must be identified or excluded during any resuscitation act. The special environments section includes recommendations for the treatment of cardiac arrest occurring in specific locations: cardiac surgery, catheterization laboratory, dialysis unit, dental surgery, commercial airplanes or air ambulances, playing field, difficult environment (eg, drowning, high altitude, avalanche, and electrical injuries) or mass casualty incident. CPR for special patients gives guidance for the patients with severe comorbidities (asthma, heart failure with ventricular assist devices, neurological disease, and obesity) and pregnant women or older people.

AREAS OF UNCERTAINTY

There are no generally worldwide accepted resuscitation guidelines for special circumstance, and there are still few studies investigating the safety and outcome of cardiac arrest in special circumstances. Applying standard advanced life support (ALS) guidelines in this situation is not enough to obtain better results from CPR, for example, cardiac arrest caused by electrolyte abnormalities require also the treatment of that electrolyte disturbance, not only standard CPR, or in the case of severe hypothermia, when standard ALS approach is not recommended until a temperature threshold is reached after warming measures. Data sources for this article are scientific articles describing retrospective studies conducted in CPR performed in special circumstances, experts' consensus, and related published opinion of experts in CPR.

THERAPEUTIC ADVANCES

The newest advance in therapeutics applied to resuscitation field for these particular situations is the use of extracorporeal life support/extracorporeal membrane oxygenation devices during CPR.

CONCLUSIONS

In special circumstances, ALS guidelines require modification and special attention for causes, environment, and patient particularities, with specific therapeutic intervention concomitant with standard ALS.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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.

Apparent Cooling Rate of 7°C per Hour in an Avalanche Victim

Avalanche victims can become hypothermic within 35 minutes of snow burial. However, reported cooling rates for avalanche victims are highly variable and it is poorly understood how much cooling is influenced by general factors (body composition, clothing, ambient conditions, duration of burial, and metabolism), unknown inter-individual factors or other phenomena (e.g., afterdrop). We report an apparent cooling rate of ∼7°C in ∼60 minutes in a healthy backcountry skier who was rewarmed with forced air and warm fluids and was discharged after 2 weeks without neurological sequelae.

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 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.

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.