Harvey Pynn / Consultant in Emergency Medicine / Bristol Royal Infirmary
Barry Roberts / Expedition Skier
Winter is here again and with it the promise of glorious powder and crisp, blue, water ice. As we all know, avalanche safety and management are core topics for the medic in winter. So, we asked Harvey Pynn and Barry Roberts to remind us of the fundamentals. Harvey Pynn is a Consultant in Emergency Medicine and Pre-Hospital Care in the South-West, with extensive expedition experience. Barry Roberts is an experienced expedition skier (Greenland, Nepal, Pakistan and Tibet), the co-author (with Doug Gurr) of Staying Alive Off Piste and the Commercial Director of Wilderness Medical Training.
Introduction
Like a climber, pushing their grade with sketchy protection and being confronted with a sudden possibility of a bad fall, the back country skier’s situation can quickly go from a state of pleasure and flow, to one of fear and panic when they realise they are in dodgy terrain. Retreat is usually not easy. Carrying on may be lethal.
Avalanche safety is a big topic. Indeed, people have devoted their professional lives to snow pack analysis, snow crystal metamorphosis and optimal search and rescue strategies. For this article, we have purposely steered clear of these areas (interesting and important though they are), choosing to focus instead on three tried and tested axioms to help to keep you safe in the back country. We will then go through the medical management of the avalanche victim.
Axiom 1 – Don’t go if you don’t know
In a managed ski domain, professional ski patrollers monitor, assess, manage and publicise the risks over the ski season. Once you venture out of bounds, you’re on your own and this especially applies to the remote expedition setting above the snowline, which may be winter or summer in the highest mountains. You have to rely on your judgment. Look out for red flags including:
Obvious avalanche activity / Clearly evidence of instability
Recent significant snowfall (+10-20cm) / Especially if associated with strong winds. Wind moves the snow around, “loading” certain slopes and aspects with packed snow. This is particular true in the lee of the wind.
Rapidly rising temperatures / Increase instability.
Most areas publish a local hazard level, based on a professional assessment of the snowpack. It is worth noting that while a hazard level of ‘3’ on a five-point scale may seem ‘average’, the risk is actually described as ‘considerable’. Indeed, most avalanche accidents happen when the risks are rated at 3. The ratings can change daily. For example, over the recent Christmas 2014 period in Chamonix the hazard level ranged from 1-4.
Everyone in the party should be equipped with an avalanche shovel, transceiver and probe. Don’t head out if you can’t use these confidently
Axiom 2 – Think terrain, not snow
If snow is the problem, then terrain is the solution. Plan and follow a route that avoids:
Steep slopes / Over 20°-25°
Convex slopes / The snowpack is weakened by the arc or “bend” over convex terrain.
Slopes loaded by snow / For example, lee-side slopes.
Terrain traps / Any ground feature that makes being caught in an avalanche more lethal. For example in a couloirs that funnels the snow, or being swept into a bowl, over a cliff or into a boulder field.
So, follow a low angled route, over high ground where the snow is shallow. Plan your route to travel between “islands of safety” avoiding steep slopes, gulleys and terrain traps.
(Image: New Zealand Avalanche Centre)
Axiom 3 – Human Factors
No group is immune to human factors. Group dynamics, leadership and experience all play a part in safely navigating avalanche terrain. Indeed, the concept of heuristic traps is a hot topic in avalanche safety. Heuristics are problem solving strategies, short-cuts and rules of thumb developed from experience. We use them to deal with complex yet familiar situations when there isn’t time or the mental capacity to consciously analyse everything.
They become heuristic traps when they are unconsciously applied to situations for which they are inappropriate. Ian McCammon has suggested six heuristic traps that off piste skiers may fall into. Here are just three of them. They should ring true no matter what your outdoor sport.
Familiarity / In avalanche terrain, familiarity can lead us to take chances we might not take in otherwise unfamiliar territory. “I’ve never seen that slope slide”. “I’ve skied this before in fresh snow and it was OK”.
Consistency / Consistency is rooted in “staying the course” and persisting with a plan of action even in the face of contradictory information. The “stick to the plan – no turning back” mentality is particularly hazardous in areas where the weather changes very rapidly, such as the Scottish Highlands, or on competitive expeditions to a set goal.
Expert halo / Interestingly, McGammon also found that groups without a recognised leader exposed themselves to less risk than those with clear leadership. Designating a leader, and following them, simplifies the group response to a challenging situation. However when we follow someone because of their personality and ‘perceived expertise’ rather than their actual skills and qualifications we can be lead astray.
Medical Management and the ICAR Guidelines
In Europe and North America, approximately 150 people are killed each year by avalanches, most often triggered by skiers, climbers and snowmobilers[1]. The number of victims in the developing world far exceeds this figure. Indeed, we will all be familiar with the tragic events in the Khumbu icefall, Manaslu and the Annapurna region of Nepal this last year.
The Medical Committee of the International Committee of Alpine Rescue (IKAR-MEDCOM) have developed extensive guidelines and algorithms regarding the medical management of Avalanche victims.[2] So, what should our strategy be when faced with the victims of an avalanche?
Dig, Dig, Dig…
The overall survival rate of Avalanche victims is 77%.[3] Survival depends on the duration and depth of burial as well as the degree of asphyxia, hypothermia and other traumatic injuries.
Being in an avalanche is akin to being in a washing machine. The physical forces exerted on the body by the turbulent snow, notwithstanding any obstacles such as trees that are in the path of the falling victim, can cause high acuity traumatic injuries.
Alongside the high incidence of trauma is the high risk of asphyxia due to being buried. The single biggest predictor of survival is how deeply a person is buried. According to a Swiss study, 39% of individuals were buried in avalanches overall, but there was a 95% chance of survival if the head was above the snow, compared to only 50% if completely buried.
There is a progressive, non-linear reduction in survival as duration of burial increases. As the graph above[2] shows, there are three distinct phases. There is a survival phase for the first 10-18 minutes of the burial whereby survival approaches 80% if the patient is extracted in this time. Death in this first phase is due to trauma. Then, casualties will enter the asphyxia phase where mortality increases. Finally, there is another increase in mortality at approximately 90 minutes due to hypothermia, in conjunction with hypoxia and hypercapnia, in those patients who may have initially had the benefit of an air pocket. The times for each phase will vary with snow densities and the geographical region of the world.
The message from these death rates is clear: survivors of avalanches or those first on scene must make every effort to extract casualties as quickly as possible for the best hope of resuscitation. Hence, dig, dig, dig.
Assess the airway / Decide whether to commence CPR
A systematic review[4] found that a patent airway (and air pocket) was essential for survival with burial times greater than 35 minutes. Those casualties who are extricated beyond 35 minutes with a non-patent airway/air pocket will be unlikely to survive. However, it can be difficult to tell in practice, as often any air pocket that was present will be destroyed by digging.
Any attempts at resuscitation in cardiac arrest following an avalanche must involve attempts at oxygenation. Compression only CPR (as advocated in ALS 2010 for ‘standard’ cardiac arrest patients) will not be successful. Those buried for >35 minutes in an asystolic rhythm with an obstructed airway may have CPR commenced but consideration for termination should be made even if the patient is hypothermic. This is in contrast to the ‘a patient is not dead until they are warm and dead’ adage but reflects the importance of oxygenation in survival and the risks to rescuers of CPR in the field.
Interventions to secure and protect the airway should be undertaken as soon as safely possible if the patient is in cardiac arrest if the appropriate skill set is available. Endotracheal intubation will allow for more effective ventilation and subsequent oxygenation and also protect against aspiration. If it is not possible, a supra glottic airway device should be considered.
If the body temperature is below 30 degrees, defibrillation in cardiac arrest may not be successful. The costs of applying repeated pulses of electricity to a cold unstable myocardium may outweigh the benefits (if 3 shocks are unsuccessful, withhold further shocks until the body temperature is >30 degrees). In addition, as the benefits of adrenaline in cardiac arrest are questionable even in normothermia, withholding adrenaline in a cold vasoconstricted patient should be considered.
Serum potassium can be used to predict outcomes in avalanched patients in hypothermic cardiac arrest. Given the efforts involved in remote rescue, point of care testing may particularly helpful in making management decisions. A serum potassium of <8 mmol/l should indicate continued resuscitation whereas >12 mmol/l would indicate termination of resuscitation. A figure between would necessitate consideration of other factors.
Patients in cardiac arrest should be transferred to a hospital with intensive care facilities. The use of a mechanical chest compression device will enable more effective compressions to be delivered in transit.
Identify and manage traumatic injuries
Traumatic injuries are extremely common in avalanched patients. Trauma was the principal cause of death in 5-25% of avalanche victims. Variation will depend on factors such as open versus forested slopes. Spinal injuries should be suspected and patients should be carefully moved and packaged. Rescuers should be comfortable managing catastrophic haemorrhage, advanced airway management as well as the aggressive initial management of traumatic cardiac arrest.
Deal with hypothermia
Hypothermia is a significant complication of avalanche. It is rarely the sole cause of death and in fact there may be some protection of being hypothermic if in cardiac arrest. The cooling rate during burial is exacerbated by light, sweaty clothing in an exhausted casualty. The ‘3 H’ spiral of hypoxia, hypercapnia and hypothermia must be broken as soon as possible to decrease the cooling rate, which can otherwise be as much as 9°C per hour.[5]
The measurement of body temperature in the hypothermic patient presents challenges. The most accurate is a temperature probe placed in the lower part of the oesophagus in an intubated patient. Epitympanic membrane thermometers are reasonably accurate in non-intubated patients if the ear canals are not full of ice. Rather than worry about temperature measurement in the field, we can use the Swiss staging classification, which is based on clinical findings (Table: Brugger 2013): [2]
Exercise caution
It is of paramount importance to rescue hypothermic patients with care. Otherwise, they may suffer post-rescue collapse. Post-rescue collapse can occur for a number of reasons:
Mechanical irritation / Patients cooler than 32 degrees are at risk of VF from rough handling.
Lifting / Lifting patients upright can cause a brief reduction in venous return, leading to cardiovascular instability. Always transport patients horizontally.
Afterdrop / Occurs when increased venous return from warming extremities leads to a further drop in core temperature. Help prevent this by removing wet clothes and wrapping patients in wind proof and water resistant outer shells preferably with active warming (e.g. chemical heat packs).
Administration of oxygen may reduce post rescue collapse by improving myocardial stability.
Summary
1 / Gather information on the weather and snow pack
2 / Think about the terrain
3 / Be mindful of human factors
4 / Dig patients out quickly then extricate them gently
5 / Assess the airway – if obstructed and the patient is in asystolic cardiac arrest following a prolonged burial, consider the futility of commencing resuscitative efforts. If resuscitation of an arrested patient is commenced, transport to a hospital with ECMO or bypass facilities taking into account serum potassium.
6 / Assess degree of hypothermia using Swiss staging classification
7 / Actively rewarm and transport conscious casualties to the nearest ED
References
[1] Etter HJ. Report of the Avalanche subcomission at the general meeting of the ICAR. 2010
[2] Brugger H et al. Resuscitation of Avalanche victims. ICAR MEDCOM. Resuscitation 84(2013) 539-546
[3] Brugger H et al. Field Management of Avalanche victims. Resuscitation 2001;51:7-15
[4] Boyd et al. Prognostic factors in avalanche burial: a systematic review. Resuscitation 2010;81:645-652
[5] Oberhammer et al. Full recovery of an avalanche victim with profound hypothermia and prolonged cardiac arrest treated by ECMO. Resuscitation 2008;76:474-80
You can learn more from Harvey and Barry at WMT’s new Mountain Medicine on Skis Course (8-12 Feb 2015). The course includes four intensive days of technical on-slope ski instruction and coaching including off-piste skiing and an introduction to ski touring. An hour a day on the mountain will be dedicated to practical mountain medicine training in addition to 8 hours of intensive medical seminars après ski. Non-medic partners are welcome. For more information, you can contact Barry by email on wmt@wildernessmedicaltraining.co.uk.
