Cold Weather EMS Operations

By Cynthia Ross Tustin

In March 2007, Bradford, Ontario, firefighters responded to a 75-car pileup on one of Canada’s busiest highways. The blinding snow from the 70-kilometer winds caused zero visibility and windchill temperatures of –37˚C (–34.6˚F). That’s cold, even by Canadian standards! The incident ultimately closed the six-lane highway for more than 24 hours; miraculously, there were no fatalities. The number of allied emergency services that participated in the emergency made the incident management system (IMS) interesting. Some of the extrication techniques required to separate a tractor trailer load of car batteries from a leaking propane transport truck took skill and precision. And the burning bus full of senior citizens definitely complicated matters! Despite all these obstacles, our biggest issue was the weather.

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(1, 2) These are just a few of the vehicles involved at the accident scene. The photos do not do justice to the weather conditions. (Photos courtesy of author unless otherwise noted.)

The bone-chilling temperatures impacted everything from operations to patient care to the safety of on-scene personnel. Prolonged exposure to such temperatures is hard on staff, hard on equipment, and brutally hard on the injured. Although just about any aspect of this collision would make for interesting reading, I will focus on the physiology (how the body reacts to cold) and pathophysiology (how cold detrimentally affects the body), as well as some of the medical conditions. Treatment of the cold injuries on-scene was very limited, but there were some interesting lessons learned that can help you decrease the severity of cold injuries in your patients.

THE EFFECTS OF COLD ON THE BODY

Humans are warm-blooded mammals that maintain a constant temperature, about 98.6˚F. We generate heat primarily through internal metabolic processes. Muscle activity augments that heat. That makes us both homeothermic (constant temperature) and endothermic (heat produced internally). Heat is produced mainly through the organs and muscles and is removed as blood flows through the body and then dissipates through the skin and lungs. Sweating, for example, is the body’s response to being either too hot internally (because of vigorous exercise) or too hot externally (because of a hot, humid day). The point is that a healthy human body continually self-regulates to stay in the ideal balance and keep a consistent core temperature.

We have two ways of staying in the ideal balance—through voluntary and involuntary physical responses. The voluntary responses are obvious: turn up the furnace, put on another layer of clothing, get up and move around, or get out of the elements. Our trapped patient on the highway could do none of these things. He was entangled in the cab of his transport truck, with the trailer of another transport truck on top of his legs. We had to cut wreckage away and lift the other truck off before we could actually reach him. And remember, the howling winds made it –37˚C—no furnace, no extra clothes, no getting up and moving around, and getting out of the elements consisted of spreading out a canvas tarp.

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(3, 4) Bradford and New Tecumseh firefighters perform extrication. The fully loaded transport truck rested almost entirely on top of the cab of the propane tanker truck. The driver was pushed backward on impact, and his legs were trapped under the steering wheel. His legs were not crushed but were badly entangled. The salvage tarp is all the protection from the –37˚C temperature that was available. The driver was trapped for approximately three hours. Miraculously, he was treated and released from the hospital two days later.

Involuntary physical responses are the ones your body does naturally, through two means. The first, and most dominant, is through the hypothalamus in the brain. The hypothalamus is the human thermostat. The second temperature control feature is our skin. The blood vessels in our skin are able to react to temperature changes. The body responds to the temperature of the blood that circulates through the brain, core organs, and receptors in the skin and regulates itself accordingly. If the brain senses that it’s too hot, it implements heat-avoidance behavior, vasodilation (dilated blood vessels) and sweating. If it senses that it’s too cold, it implements heat-seeking behavior, vasoconstriction (blood vessels constrict) and shivering. The dilation and constriction of blood vessels happens first; sweating or shivering, second. So in this type of cold situation, the vasoconstriction and the shivering would increase in intensity as the body’s blood temperature decreases.

Vasoconstriction controls the blood flow throughout the body, and shivering controls the heat production. The body will naturally attempt to conserve heat. It will send less and less to the periphery, hands and feet, and keep the warm blood in the core. As less blood flows to the peripheral skin, less heat radiates away and less chilled blood returns to the core. Only muscle activity can substantially increase the internal body temperature, and shivering is the involuntary response. It is essentially an ineffective exercise. Shivering can occur before your patient becomes hypothermic (below normal body temperature). Shivering by itself is not overly dangerous, but it is a sign of cold stress; and because it’s muscle activity, it is tiring. So our patient on the highway only had involuntary physical responses at his disposal to keep warm.

Also consider the status of our patient: He regained consciousness trapped and entangled in the cab of the truck; and he was bleeding, in pain, in shock, and intensely claustrophobic (fear of confined spaces). These traumatic facts alone are enough to overwhelm the body’s ability to save itself from the cold. When you add in the –37˚C temperature, all of a sudden you have a life-threatening situation. The weather truly was the biggest threat to our patient.

(5) This heating unit is built into a cabinet on one of Lulea, Sweden’s, emergency response vehicles. Swedish response personnel have found ways to bring heat to wrecked vehicles. Flexible vent piping is connected to the heater and fan and warm air is blown into the vehicles as necessary. (Photos courtesy of Chief Patrik Bylin, Lulea, Sweden.)

The effects of the cold, once it starts to overwhelm the body’s ability to generate its own heat, can damage the body. This is the pathophysiology of cold. Once our bodies reach a certain temperature (and that’s different for each of us), our systems tend to slow down and everything becomes much less efficient.

(6) Lulea Fire Rescue crews at a motor vehicle accident introduce heat into the wrecked vehicle. This is valuable to the patient and helpful to EMS crews inside who do not wear the same level of thermal personal protective equipment that firefighters wear.

Consider your core organs to be like a car. Fluids in extremely cold weather become thick (oil, hydraulic fluid), and flexible substances such as plastic and rubber become stiff and not pliant (skin, muscles, and tendons). Oxygen will become more soluble and will not be as readily available to the hemoglobin. When the circulatory system slows down, it is no longer able to send oxygen-rich blood to the vital core organs, nor is it able to effectively take away carbon dioxide and other toxins from vital core organs. CO remains in the bloodstream, lactic acid remains in the muscles (and remember, they’ve been working overtime shivering), excess water won’t go to the kidneys, and there is decreased oxygen to the brain.

(7) Here heat is being introduced to a stranded train car by a portable heating unit from Lulea Fire Rescue. The department is prepared to handle many situations requiring supplying heat to victims.

Once your patient’s core body temperature approaches 90˚F, it will start to lose the ability to generate its own heat. After the body passes this core temperature, shivering will stop and core functions such as metabolism, ventilation, heart rate, and cardiac output will decrease. This means an altered mental status and slowed vital signs. The natural vasoconstriction from the involuntary physical response, plus continued cold exposure, can lead to frostbite, although, in the case of our patient, the constricted peripheral blood flow helped reduce the external bleeding from his cuts.

PERSONNEL’S CONCERNS AND ACTIONS

The fire crew and the on-scene paramedics had much to be concerned about. We were essentially helpless to alleviate any of the medical problems—the ones from the accident and the extreme cold—until we gained access to the patient. This took approximately three hours.

Exposure to this type of extremely cold weather generally causes two types of cold-related injuries—hypothermia and frostbite. Our patient suffered both. Table 1 outlines the three levels of hypothermia, the core temperatures associated with each, and what you can expect to see with your patient. The symptoms range from mild shivering to spontaneous ventricular fibrillation.

Frostbite is the freezing of tissues and tends to affect areas where there are decreased blood flow and little or no heat-producing muscles. That’s why body parts such as fingers, toes, hands, feet, ears, and the nose are the most prone to frostbite. The body’s natural heat-preservation mechanism practically invites frostbite! This means there are basically two mechanisms for frostbite. First is the actual freezing of cells and tissue. The second is tissue death from prolonged lack of oxygenated blood to that particular area.

Our patient suffered mild frostbite and ultimately lost a few layers of skin, which will grow back, and had some decreased sensation in his fingertips. He was fortunate enough to keep all of his digits. He was also on the borderline between mild and moderate hypothermia.

So what interventions, aside from extrication, were we able to do? Initially, we attempted to protect him from the wind with a heavy salvage tarp. Ordinarily, this is fairly helpful at extrication scenes. In this case, the wind made it grossly insufficient, and it was a hindrance at times during extrication. He was given a toque (knitted hat) to keep his head and ears warm, although this was done out of thoughtfulness rather than design. (We had no formal standard operating guidelines to deal with cold weather extrication.) We wrapped him in blankets and stayed with him constantly. The blankets helped for short periods; the driving snow made it wet quickly. The paramedic staff took his vital signs frequently and monitored him. Once we cut him free, we handled him gently, wrapped him in more blankets, and took him to a warm ambulance to be rushed to the hospital. Paramedics in our area do not carry IV fluids, but they would not have been helpful anyway because there was no way to keep them warm.

LESSONS LEARNED

Hindsight, coupled with my attending a conference on cold weather emergencies, has led to the following operational changes for our department:

• When the weather starts to turn cold, we carry a warm clothing kit on the trucks specifically for patients—it contains gloves, toques, and a winter coat.
• If the exposure to the elements is prolonged, we’ll place a water-resistive covering over the blankets.
• We put tarps in place sooner.
• We’re exploring one of the techniques used in Sweden during cold weather extrication. Fire Chief Patrik Bylin from Lulea, Sweden, was a guest speaker at the conference I attended and explained many of Sweden’s operational issues. In Sweden, response personnel have found ways to introduce heat into the wrecked vehicle from an external source. Sometimes a small electric heater can be placed inside the vehicle. Other times, an intrinsically safe heat source may be required (our patient was in a leaking propane tanker—no ignition sources allowed). In those cases, fire crews in Sweden placed heaters farther away and used piping similar to dryer venting to bring heat to the trapped patients.

The other speaker of interest at the conference was Dr. Gordon Giesbrecht, known as “Dr. Popsicle.” He is an expert in extreme cold emergencies, be it from weather or ice water immersion. After our 75-car winter pileup, I wanted to learn more, and the best and most current information was coming from him and a book he co-authored called Hypothermia Frostbite and Other Cold Injuries (The Mountaineers Books, 2006). The book provided a great deal of technical information for this article and is now a reference for our staff.

Cynthia Ross Tustin is deputy chief of the Bradford West Gwillimbury Fire and Emergency Services in Ontario, Canada. In her 21 years of fire service experience, she has served as a volunteer firefighter; a fire service adviser and a fire protection adviser in the Office of the Fire Marshal; and assistant chief of the Barrie Fire and Emergency Service, responsible for the Fire Prevention and Development Branch. She is a registered nurse and has worked in emergency rooms and trauma units in several large urban centers. She has been a contributor to several fire service publications and speaks at conferences in Canada and the United States.