Terry O’Connor, MD
16:30pm. The ranger station is still. The storm clouds are clearing. Inside, the rolling glow of embers fade in the fireplace, as outside, the amber alpenglow lights the fresh coat of snow on the mountain above.
A knock on the door breaks the silence.
“Hey are you a Ranger?, I just snowshoed down from Panorama Point. When the clouds cleared I saw a single set of ski tracks ending in an avalanche path below the Paradise Glacier. . I didn’t see any ski tracks out”
Looking out to the parking lot, you see a single car, out of state plates, coated in the last few cm of today’s storm snow. A sticker is still visible on the rear view window . . . ‘ No friends on powder days ‘ . A single set of footprints leads to a skin track with a single set of pole plants. Damn.
You place a call the SAR coordinator.
In a previous post we challenged the assumption that all prolonged avalanche burials or delayed rescue attempts are inevitable body recoveries. In reviewing the latest data and survival curves we were reminded that indeed the best chance of recovery occurs within the first thirty minutes of burial, as most victims succumb to either trauma or asphyxiation within this window. However, in review of our most robust avalanche survival data set to date, we discovered that burial over a half hour does not necessarily mean 0% chance of survival, but perhaps anywhere from 5-20% chance of survival. These are the victims slowly succumbing to the insidious impacts of hypothermia, lack of oxygen and accumulation of carbon dioxide.
Now, knowing that all prolonged burial victims still deserve our sense of urgency in response, we will dig a bit deeper into how we determine who actually has a chance, how to identify them, and what we can do to give them the best chance possible. It turns out that some of those who we recover looking dead, may not be dead yet.
17:00pm. Signal search has led you and the hasty team to the toe of the slide overlying the creek bed. A ski pole sticks out bent over in the loose blocky debris. Your probe finds a soft thud instead of frozen earth.
Digging down through the loose debris you find a young skier, unresponsive, head dangling into the open moat of the creek bed below, mouth free of snow. As you slowly uncover his body you find no obvious gross bleeding, no gross deformities, clothing cold and drenched, his chest under his jacket feels cool to touch with your ungloved hand.
Your partner can’t feel a pulse and he starts CPR. You break the SAR coordinators conversation with helicopter ops for emergency traffic. Comm patches you into med control. Before you can start with your assessment, and ask what to do, the doctor interrupts . . .
‘Did he have an airway? How long was he buried? Does he feel cold?’
Let’s highlight the key game changing principals in avalanche victim resuscitation that have been born out of latest medical research.
The recently updated International Commission on Alpine Rescue protocols include more sophisticated metrics and interventions that are not common in our typical North American austere medical rescue settings. Here our first line of rescue is often a WFR, EMT, or paramedic without the resources of a physician on helicopter. So we propose a simplified algorithm for your perusal for now. We’ll step back to our scenario to help hit the highlights that are the foundation for the IKAR guidelines.
Avalanche Rescue Algorithm. 1 Routine CPR care for cardiac arrest as recommended by American Heart Asssociation. 2 Modified hypothermia cardiac arrest treatment (see Figure 3)
Let’s first review what has not changed. Speed in locating the victim and clearing the airway, tempered by an assessment of scene safety still comes first and is paramount. This should, of course, not be a surprise as we have just reviewed the best chance of survival occurs within the first 15-30 minute window. Also, the ‘obviously dead’ (i.e. decapitation, frozen) are still obviously dead. In addition, the walking wounded (those who are alert with vital signs who can tell you what hurts and what is wrong) still receive standard care. That is, to protect from further heat loss, assess and manage injuries in your trauma survey and transport to appropriate care.
The main change to the rest of the decision tree is to identify who may benefit from prolonged CPR and why.
Now back to our case to help clarify this. In the scene size up the ranger found no obvious signs of trauma incompatible with life. Nor was the patient one of the ‘walking wounded’, as he was unconscious and unresponsive. His partner could not find a pulse, the patient appeared ‘dead’, and so he appropriately started CPR.
Medical control asked whether patient had a patent airway and air pocket, because a buried patient will first succumb to asphyxia well before hypothermia if unable to breathe.
Medical control then asked how long the victim had been buried and if he felt cold. Why is 60 minutes important? Based on research, the quickest an avalanche victim could reach a temperature cold enough to result in cardiac arrest due to hypothermia (roughly 30-32C) is 35 min with the majority taking 60min or more. This may occur faster in special circumstances such as cold water immersion. In addition a body that feels warm to touch is unlikely to have had hypothermic arrest.
Most importantly, the current medical literature supports that only those buried more than 60 minutes have had successful resuscitation from hypothermic arrest.
So if we have excluded death from obvious trauma, if a patent airway was identified on extrication, if the patient’s core feels cold, if he was buried for more than 60 minutes, or if we can confirm a core temp < 30C is it possible our patient without vital signs looks ‘dead’ because he got severely hypothermic?
Yes it is. Now why does that matter?
It matters because the latest medical literature is replete with evidence of individuals who have cardiopulmonary arrest due to hypothermia and survive to full neurologic function despite prolonged recovery times and even delayed CPR. If your scene size up can support the case that your victim may be dead because he got too cold then some modifications in basic life support and CPR measures are warranted and acceptable (figure 3).
Figure 3. Modifications to standard basic life support and advanced life support in cases of hypothermic cardiac arrest
Severe hypothermia can be thought of as a state of suspended animation. This state is reflected in some abnormal or absent vital signs. Viable heart rates could be as low as just a few a minute so pulse checks should last up to 60 seconds. The heart tissue at low temperatures is extremely succeptible to arrhythmias and cardiac arrest so premature chest compressions should be avoided and all patients handled gently.
If cardiac arrest does occur the body can sustain an exceptional amount of insult due to its metabolic hibernation. With normal body temperatures, CPR is often terminated after 30 minutes of resuscitative efforts if all lifesaving maneuvers have been exhausted. Whereas individuals in hypothermic arrest have survived cardiac arrest lasting up to 8 hours.
In field rescue situations, continuous CPR may not be feasible or safe for first responders. It is also impossible to deliver high quality manual CPR for prolonged periods of time. Therefore, mechanical CPR devices are highly recommended in these situations if available. If mechanical devices are not available, there is a body of evidence gathered from hypothermia induced cardiac procedures and field case reports showing intermittent CPR in patients undergoing cardiac arrest after hypothermia, may be acceptable and life saving. Current recommendations suggest that those with a core temperature <28C can receive 5 minutes of CPR followed by <5 minutes of pause in CPR. Those with a core temperature <20C can receive alternating 5 min continuous CPR and <10 min pause in CPR.
Termination of CPR efforts in hypothermic arrest cases rarely occurs in the field. Severely hypothermic patients ultimately require transfer to a medical facility that can perform rapid rewarming, typically through use of cardiopulmonary bypass technologies before defibrillation efforts are successful or before medical direction can definitively terminate resuscitation efforts.
17:20pm. Medical control advocated for prolonged CPR efforts given chance of hypothermic arrest. You recheck for a pulse over a full minute interval and confirm need to continue CPR. An AED is attached and shock is advised. Initial defibrillation attempt is successful, but patient loses pulse again within a few minutes of movement. You understand patient will likely need cardiopulmonary bypass rewarming before successful defibrillation and confirm helicopter is planning on delivery to appropriate facility. You allow for occasional pauses up to 5 minutes in CPR to facilitate the technical components of transfer as you perform a low angle lower to the LZ.
En route to hospital flight nursing staff intubates patient. An esophageal temperature probe is placed confirming core temp of 28C so no further defibrillation efforts are pursued. Two interosseous lines are placed and warm IV fluids are initiated. CPR continues. Flight nurse staff calls ahead to hospital to ready the cardiac team for emergent rewarming bypass.
The next day the flight nurse calls you back with follow up. Patient was rewarmed and afterwards converted out of ventricular fibrillation with return of spontaneous circulation. This morning he’s sitting upright eating eggs for breakfast acting normally. His only complaint is chest pain, . . . probably a result of the 3 hours of CPR.