Accidental Hypothermia & Frostbite: Cold-Related Conditions James J. O’Connell, MD Denise A. Petrella, RN, CS, ANP Richard F. Regan, PA-C ankind has struggled with injuries from the extremes of weather throughout history. While ancient physicians such as Hippocrates and MGalen wrote extensively about hypothermia, most reports of cold injuries in the literature come from military history. Hannibal lost half of his army crossing the Alps in 218 B.C. During Napoleon’s retreat from Moscow in the fall and winter of 1812, as many as 50,000 soldiers died of hypothermia. During the Great World Wars of the first half of the 20th century, ground troops on the march and in the trenches of Europe succumbed to the severe effects of the cold. High altitude frostbite was described in 1943, accounting for more injuries to heavy bomber crews in World War II than all other causes combined. And during the Korean War, 10% of the total US casualties were due to the cold. Homeless persons who wander our urban cities sunny day of 55°F (13°C) was followed by rain and Early Frostbite and rural areas are vulnerable to the extremes of a fall in temperature to 34°F (1.1°C) in the evening. of the Hand. This man left the weather and exposure. Our goal in this chapter is Our patient’s body temperature was 59°F (15°C), Accident Floor at to review how best to recognize, evaluate, and treat and he survived after undergoing cardio-pulmonary Boston Medical the common but preventable cold-related injuries of bypass therapy at Massachusetts General Hospital. Center on a clear hypothermia and frostbite. January morning Definition and Pathogenesis with a temperature of 18°F and no Hypothermia Hypothermia is defined as a core body tempera- wind. We found During the twenty-year period from 1979- ture below 95°F (35°C), and can be helpfully him one hour later 1998, hypothermia was the cause of death for categorized as follows: with frostbite of his approximately 700 persons annually in the USA, • mild hypothermia: 90°-95°F (32°-35°C) fingers. This picture was taken several with half of these deaths attributed to extremely cold • moderate hypothermia: 82°-90°F days later. The weather. Mortality rates in accidental hypothermia (28°-32°C) blisters are bloody, have ranged from 30-80%. • severe hypothermia: below 82°F (28°C) and he eventually Hypothermia occurs not only during the bitter The body generates heat through the metabo- lost two fingers. cold. Other important contributing factors include lism of food and water, the work of the muscles, Photo by James O’Connell MD wind speed, moisture, alcohol, drugs, and the and certain chemical reactions. The body’s heat is duration of exposure to the cold. Our worst case of lost primarily through the skin and lungs in four hypothermia among Boston’s homeless population important ways: occurred in early October several years ago, when a • radiation accounts for 65% of heat loss. The Health Care of Homeless Persons - Part II - Accidental Hypothermia and Frostbite 189 Wind Chill Chart. Courtesy of the National Weather Service Forecast Office The most glaring example is the uncov- the cells begins to crystallize, and cell death results. ered head, which can dissipate up to 50% The hypothalamus attempts to stimulate heat of the body’s heat; production through shivering and by increasing • conduction is the direct transfer of heat catecholamine and adrenal activity. To minimize to a nearby object that is cooler than the heat loss, blood flow to the peripheral tissues is body. This is usually only a small frac- reduced by vasoconstriction. tion of the heat lost by the body, but wet clothing causes a 20-fold increase in heat Causes of Hypothermia loss from the body, and submersion in In a study of 85 consecutive patients with cold water increases the heat loss by 32 hypothermia at San Francisco General Hospital, times; underlying infection or sepsis was the primary cause • convection occurs when the warm layer of in 33 (39%) and alcohol ingestion in 27 (32%). heat near the body is lost by the move- Exposure accounted for only 9 cases. Almost half ment of air, and the degree of heat loss is (49%) of these cases of hypothermia resulted in dependent on the speed of the wind. For death. example, a wind of 12 mph increases heat Thus the differential diagnosis of hypothermia loss by 5 times; is important to keep in mind. In addition to • evaporation is the heat lost when liquids environmental exposure, several medical conditions are converted to gas. The evaporation of can either cause or increase the risk of hypothermia, water cools the body at the rate of 0.6 kcal including: sepsis, hypoglycemia, neuromuscular per gram. This occurs through sweating disease, malnutrition, hypothyroidism, and adrenal and respiration, which together account insufficiency. Some medications can hinder the for about 20% of the body’s heat loss. body’s response to the cold and increase the risk of When hypothermia occurs, cell membranes hypothermia, such as beta-blockers (e.g. propranolol allow intracellular fluid to leak out, and enzymes or Inderal™), clonidine (Catapres™), meperidine begin to malfunction. Electrolyte imbalance (Demerol™), and neuroleptics (e.g. haloperidol occurs, especially hyperkalemia (increased potas- or Haldol™). Alcohol is particularly dangerous sium in the bloodstream). Water inside and outside because it not only alters the ability to feel the cold 190 The Health Care of Homeless Persons - Part II - Accidental Hypothermia and Frostbite The Health Care of Homeless Persons - Part II - Accidental Hypothermia and Frostbite 191 Table 1: Factors that predispose to hypothermia occur. Cardiac arrhythmias are common; Environment • severe hypothermia, below 82°F (28°C): hy- Time of year potension, slow pulse, pulmonary edema, Ambient temperature coma, ventricular arrhythmias (including Wind chill ventricular fibrillation). The heart can Water chill stop beating completely (asystole or “flat Behavior Inadequate or wet clothing line” on the EKG). Immersion Prolonged exposure Diagnostic Evaluation Lack of fitness Early recognition is critical. Clinicians caring Fatigue for homeless persons should maintain a high degree Inadequate shelter and heat of suspicion for hypothermia whenever the weather Drugs turns cold. The astute clinician needs to be alert Alcohol Nicotine to any of the signs and symptoms described above. Opiates Most standard thermometers are not accurate below Barbiturates 93°F (34°C) and are not suitable for measuring the Benzodiazepines degree of hypothermia. The tympanic thermom- Tricyclic antidepressants eters that are commonly used are unproven to date Phenothiazines for assessing hypothermia. Decreased thermoregulation The physical examination can be perplexing, Age extremes Central nervous system trauma especially in moderate and severe hypothermia. Stroke Patients can appear dead: comatose, the blood Wernicke’s encephalopathy pressure difficult to hear, respirations shallow to Burns absent, the pulse not palpable, the pupils dilated, Sepsis deep tendon reflexes absent, and when shivering Acute myocardial infarction stops (usually around 85°-89°F or 30°-32°C) the Chronic renal failure muscle tone increases and can appear similar to rigor Pancreatitis mortis. Helpful findings are signs of frostbite, sites Neoplasms Decrease heat production Hypothyroidism Hypoglycemia Hypoadrenal states Anorexia and impairs judgment, but also causes peripheral vasodilation that further enhances the loss of heat. Plantar Frostbite. This elderly man slept Symptoms and Clinical Presentation for several cold nights Everyone caring for homeless persons in shelters in an abandoned car and on the streets should become familiar with the in South Boston. He signs and symptoms of hypothermia: has severe frostbite , 90°-95°F (32°-35°C): involving the toes • mild hypothermia and soles of his feet. increased heart rate and respiratory rate, Photo by hyperventilation, difficulty walking, James O’Connell MD slurred speech, impaired judgment, pro- nounced shivering, and frequent urination due to the “cold diuresis”; • moderate hypothermia, 82°-90°F (28°- 32°C): the pulse drops, breathing becomes shallow with a slowed respiratory rate, shivering stops, the reflexes are slowed, and the person can become very confused and disoriented. Paradoxical undressing may 190 The Health Care of Homeless Persons - Part II - Accidental Hypothermia and Frostbite The Health Care of Homeless Persons - Part II - Accidental Hypothermia and Frostbite 191 should be able to generate heat through Table 2: Interesting Hypothermia Facts shivering. The half life of morphine is 1.5 hours at 98.6°F (37°C), • Active external rewarming. This means but 36 hours at 77°F (25°C). the utilization of warm blankets, warm Pancreatitis is seen in about 50% of patients after they baths, or heating pads to warm the patient. are warmed. This is generally sufficient in moderate hypothermia, as well as for anyone who At core temp of 86°F (30°C), urine flow is three times normal. has failed to respond to passive external rewarming. There is a risk with this pro- With every 1°C drop in core body temperature: cess which is called “afterdrop”. When • blood flow in the brain decreases 7% • viscosity of blood increases 5% both the extremities and the trunk are • hematocrit increases 2% warmed together, the cold blood which Advance life support protocols, especially defibrillation, has been pooled in the extremities returns may be ineffective when the core temperature is less to the central circulation and can cause a than 86°F (30°C). drop in the core temperature. At the same time, peripheral vasodilation begins as the of insulin or drug injection, and evidence of head extremities are warmed, and this flow of trauma. The rule is to assume that no one is dead blood away from the core can cause a sud- “until warm and dead”; thus resuscitation efforts den drop in blood pressure and result in should continue until the body temperature reaches dangerous arrhythmias.