Management of Cold Injuries

Management of Cold Injuries

Linda Laskowski-Jones

Lawrence J. Jones


Wilderness emergency medical services (WEMS) providers are exposed to a wide range of weather and environmental conditions. Extremes of cold, heat, rain, snow, humidity, wind, and solar energy can impact provider safety and performance, as well as the capability to care for team members and patients. For this reason, WEMS providers must have a keen awareness of the risk factors that lead to cold injuries. Equally important is developing the knowledge base to accurately discern clinical manifestations of the various cold injuries, so that appropriate medical management can be planned and executed. Failure to consider the physiologic consequences of cold injuries can lead to significant morbidity and mortality in a wilderness setting.

Having a fundamental understanding of the mechanisms and pathophysiology of cold injuries enables WEMS providers to better prepare for outdoor deployment, as well as employ best practice strategies for assuring personal safety and well-being. Scene safety is of significant importance and begins with appropriate trip preparation. The objective is to remain an asset in a rescue rather than become a casualty of the environment. Attention to weather forecasts, avalanche danger, thin ice, dangerous road and trail conditions, and the potential for falling tree limbs heavy with snow or ice are essential for planning risk mitigation strategies.


Cold injuries encompass a spectrum of disorders from minor, superficial manifestations without long-term consequences, to profound physiologic derangements that can ultimately lead to permanent disability and death. This chapter covers commonly encountered conditions that stem from exposure to cold and presents out-of-hospital treatment approaches that are pertinent to an austere or wilderness environment. Perhaps most vital is information that will enable EMS providers to plan and take the necessary actions to prevent these conditions from occurring in themselves and others.


The human body strives to maintain a narrow window of body temperature, at or near 37°C (98.6°F), through a dynamic balance of heat production and heat loss. Enzymatic functions required for normal human physiology are temperature dependent. If body temperature drops below the normal set point, metabolism increases to generate more heat and peripheral blood vessels constrict to reduce heat loss at the body surface and in the extremities. Shivering is a highly effective involuntary mechanism for thermogenesis, or heat production, through muscular activity. Cognitively intact humans also make conscious choices to promote warmth such as adding clothing, increasing activity, seeking shelter and heat sources, and consuming food. When cognition is impaired—which, ironically, is an early effect of cold illness itself—the risk of heat loss due to maladaptive behaviors is significant.

Heat is lost from the body in four ways. The methods of heat transfer (loss) include conduction, convection, radiation, and evaporation.

Conduction is the heat transfer between two objects through direct contact. Body heat will move from a warmer object to a colder object. For example, sitting on a cold rock or lying on snow will result in conductive heat loss from the areas of the body that are in contact with the cold surface. Wet clothes or immersion in cold water exacerbates the heat transfer.

Convection is the process in which heat is carried away from the body by currents of air or water movement. The body warms the air or water in contact with the skin; the heat is carried away by the movement of the air or liquid and then is replaced by an unheated source. The heat loss is related to the relative temperature and the speed of the air or water. This is the reason why the outdoor temperature feels colder when the wind speed is high and is the basis for the concept of wind chill. The use of appropriate insulating clothing and windproof outerwear can decrease heat loss from convection.

Radiation is the loss of heat through infrared radiation. Heat from the warmer body radiates to the surrounding cooler environment. Radiant heat loss is much more significant in a colder environment because of the difference in temperature between the heat source and the surrounding environment. Insulating clothing, including wearing a hat, reduces radiant heat loss.

Evaporation is the energy lost through the process of converting liquid on the surface of the skin to a gas. Body heat is necessary to evaporate liquid (sweat) to a gas, thereby cooling the body and releasing that heat to the air. This process is much more effective in a dry environment, which is why it is so useful for cooling in the desert. Heat is also lost through warming and humidifying air in the lungs during the process of breathing or respiration. This form of heat loss can increase at high altitude because of the deeper and more rapid respiratory pattern that is common at elevation.

The pathophysiologic effects of cold injury are important to recognize to enable timely identification of cold-induced conditions. Cold that produces a lower than normal body temperature (hypothermia) acts as a central nervous system depressant. Effects worsen because body temperature continues to drop. Manifestations include impaired judgment, incoordination, slurred speech, and a decreased level of consciousness. In a wilderness environment, these pathophysiologic effects lead to maladaptive behaviors and a subsequent a high risk for injury.

The respiratory system initially responds to the cold through an increased respiratory rate. However, a progressive drop in body temperature leads to respiratory depression with a corresponding decrease in carbon dioxide production.1 Cold-induced pulmonary edema can develop. With severe cold, the thorax can become stiff and noncompliant, furthering respiratory failure.

The cardiovascular system is initially stimulated via the autonomic nervous system and responds with tachycardia, peripheral vasoconstriction to conserve heat, and blood pressure elevation. However, as body temperature drops, cardiac conduction slows and contractility decreases, producing bradycardia, decreased cardiac output, and hypotension. Because cold induces cardiac conduction system impairment and irritability, all manner of atrial and ventricular dysrhythmias can occur. A characteristic electrocardiographic finding is the appearance of an Osborn or J wave at the junction of the QRS complex and the ST segment when body temperature falls to 32.2°C (90°F) or below.1 These waves become more pronounced as body temperature drops further and can mimic the appearance of a myocardial infarction.

Peripheral vasoconstriction is a heat conservation response to shunt peripheral blood from the cold extremities to the core. Conversely, if an individual is rewarmed, particularly through heat application to the skin, peripheral vasodilation occurs. When the cold peripheral blood mixes with the warmer core blood as circulation is stimulated during active rewarming, core temperature afterdrop ensues. In afterdrop, body temperature will continue to drop for a period of time even after rewarming interventions because of this counter-current mixing effect of cold peripheral blood and warm core blood. Keep in mind that cardiac irritability increases with this drop in temperature.

The renal system is also impacted by peripheral vasoconstriction. Because vasoconstriction in the extremities pushes more blood volume into the core, there is greater blood flow to the kidneys. This increased volume load produces a significant diuresis of dilute urine, even in dehydrated individuals. Consuming alcohol can double the volume of this diuresis.1

Cold also impacts the ability of blood to clot normally. Blood clotting is a temperature-dependent process; the enzymes responsible for normal coagulation are able to function only across a very narrow temperature range. A core body temperature less than 36°C (96.8°F) produces a coagulopathy that is unresponsive to the administration of blood products.2 This coagulopathy is especially detrimental to individuals with injuries because they will suffer increased blood loss.

Cold can also affect the body at the tissue level, particularly in skin without adequate protection from cold and wet environmental conditions. Skin that is exposed to cold can suffer various forms of damage, including nonfreezing injuries as well as superficial to deep tissue freezing with ice crystal formation. Adequate blood circulation plays a key role in maintaining warmth. When the skin is exposed to temperatures below 15°C (59°F), vasoconstriction starts to occur, which can promote a further drop in skin temperature from the reduction in circulation.3 If the skin becomes numb, the individual can lose awareness of the cold sensation and fail to recognize the early stages of tissue freezing. Without timely preventive measures at this stage, blood circulation will be further reduced, the tissue temperature will continue to drop and, ultimately, the skin can take on the temperature of the environment.

The pathophysiology of frostbite includes extracellular and intracellular ice crystal formation, cellular dehydration and shrinkage, derangement of intracellular electrolyte concentrations, endothelial damage, vasoconstriction, thrombosis, ischemia, and ultimately tissue necrosis.4

Inflammatory mediators such as thromboxane, arachidonic acid, and prostaglandins play a significant role in tissue destruction. Both the degree of tissue damage and the prognosis for recovery are related to the depth of the cold injury.


Cold injuries occur when heat production by the body or heat conservation is inadequate to compensate for heat loss. Freezing temperatures are not necessary for these conditions to develop. Cold injuries are possible even in moderate temperature climates. Predisposing environmental factors in a wilderness setting include an ambient temperature below 26.6°C (80°F), wet conditions, altitude, and wind chill. Wind chill, a function of wind velocity and air temperature, can exacerbate cold effects as a result of increased air movement across the body surface.

Physical factors in the at-risk individual include fatigue or exhaustion, inadequate clothing, wet clothing from perspiration, immersion, or weather conditions, poor conditioning, and insufficient food or fluid intake. Alcohol consumption and intoxication, illicit drug use, and certain medications (eg, antidepressants, opioids, and antianxiety agents) also promote cold injuries. Other significant precipitating factors include trauma, burns, dehydration, cardiovascular disease, infection, psychiatric illness, and any disease state that slows the metabolic rate or impairs thermoregulation such as diabetes hypothyroidism, adrenal insufficiency, and stroke. The use of nicotine products elevates the incidence of cold-induced tissue injury because of its vasoconstriction effects.



The medical literature varies widely in regard to the specific temperature ranges that characterize the severity levels of hypothermia, with many sources listing subtle differences in the numeric values. For the purpose of this chapter, hypothermia will be categorized as defined by the Wilderness Medical Society: mild (35°C to 32°C [95°F to 89.6°F]), moderate (32°C to 28°C [89.6°F to 82.4°F]), and severe or profound (less than 28°C [82.4°F]).7

Each severity level of hypothermia is typically associated with clinical manifestations that correspond with the pathophysiologic changes that occur in the body due to cold injury. Not all patients will exhibit these manifestations in a predictable manner, however. There may be significant variation from person to person. It is also critical to recognize that there are multiple disease and injury entities that may mimic the clinical presentation of hypothermia such as head injury, stroke, alcoholism, hypothyroidism, and hypoglycemia. Any of these conditions can occur together with hypothermia. For that reason, maintain a high index of suspicion that the patient may be experiencing multiple disorders and require care beyond that which is indicated for hypothermia alone.

Prior to the development of true accidental hypothermia at the threshold of 35°C (95°F), an individual can experience cold stress from the effects of cold temperature on the skin and may start to shiver. Of note, this person will have a body temperature of 35°C (95°F) to 37°C (98.6°F) and a normal mental status.7 Early recognition is essential: If heat production
remains inadequate and heat loss continues, accidental hypothermia will ensue.

Mild hypothermia (35°C [95°F] to 32°C [89.6°F]) results in autonomic nervous system stimulation along with depression of the central nervous system.1 Patients can often be identified at this stage when their skin is cold and pale and they exhibit the “umbles”: They stumble, mumble, fumble, and grumble. In a wilderness environment, these individuals are more likely to lose their footing when walking or climbing, become difficult to understand when speaking because of trouble forming words, be unable to perform fine motor functions with their hands (such as closing a zipper), and show evidence of mental status changes. These behaviors include becoming inappropriately argumentative, apathetic, moody, or flat in affect. The key take-away point is that these individuals are at high risk of injury due to significantly impaired coordination as well as the loss of intact judgment. As temperature continues to drop, the individual can become incapacitated and unable to function.

Shivering is pronounced and uncontrollable in mild hypothermia; it serves as an important compensatory mechanism that generates heat through muscle activity. Shivering requires calories to burn for heat production. Inadequate nutrition will negatively impact this essential physiologic response and will promote worsening of the hypothermic condition.

Vital signs in mild hypothermia reflect increased levels of circulating catecholamines, which produce tachycardia, elevated blood pressure, and increased respiratory rate. Because cold-induced peripheral vasoconstriction shunts blood to the core of the body, the kidneys respond by producing large quantities of dilute urine. Patients subsequently experience a cold-induced diuresis that will result in frequent urination, worsen any preexisting dehydration, and promote further cold injury.

Moderate hypothermia (32°C [89.6°F] to 28°C [82.4°F]) is characterized by cardiopulmonary depression and further central nervous system impairment. Cellular energy stores are depleted. Patients develop hypotension, bradycardia, and have a slow respiratory rate. Atrial and ventricular cardiac dysrhythmias are common and can be further exacerbated by rough handling. Shivering may still occur, but ultimately stops altogether. Speech becomes slurred to incomprehensible, and the level of consciousness declines to unresponsiveness as the condition worsens.

It is at this stage of hypothermia that the unusual phenomenon of paradoxical undressing can occur: Patients may shed their clothing in a profoundly cold environment because they suddenly feel very hot. Although this action seems completely counter to what a hypothermic patient should do, this phenomenon is best explained by understanding that the sensation of hot or cold is related to the perception of temperature at the skin surface.8 Because cellular energy is required to maintain peripheral vasoconstriction in hypothermia, when the body no longer has enough energy to maintain peripheral vasoconstriction, widespread peripheral vasodilation occurs.8 Therefore, the individual with an impaired mental status experiences a rush of warmth as blood flows into the cold extremities. Because the person is unable to process what is happening and respond in a logical way to this critical survival situation, he or she removes articles of clothing and casts them aside in an attempt to cool down. The resulting clothing trail serves as an ominous preterminal sign for rescue parties who are searching for a missing person in cold weather. Rescuers have found such missing persons naked in the snow with a predictably poor outcome for survival.

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Oct 16, 2018 | Posted by in EMERGENCY MEDICINE | Comments Off on Management of Cold Injuries
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