An Unresponsive 38-Year-Old Man

Lars Grimm, MD, MHS; Malkeet Gupta, MS, MD; Joshua M. Kosowsky, MD


March 15, 2016

This case is an example of primary hypothermia, or accidental hypothermia from environmental exposure. This generally occurs when an unprepared individual is put in a situation of unanticipated exposure. In primary hypothermia, the body loses heat despite normal thermoregulatory mechanisms. To prevent excessive heat loss, the body's thermoregulatory center in the hypothalamus conserves and produces heat as needed. Shivering and the release of hypermetabolic hormones will increase the basal metabolic rate and produce heat; however, these productive capacities can be overrun if the rate of heat loss is too great or the energy stores are depleted over time.

Primary hypothermia must be distinguished from intentional hypothermia, in which an individual is placed in an induced state of hypothermia for neuroprotection.[4] It must also be distinguished from secondary hypothermia, in which the low body temperature is the result of a medical illness that causes the body's temperature set-point to be reduced. Other conditions, including infection, metabolic abnormalities (eg, hypoglycemia), drug or alcohol overdose, and endocrine problems (eg, hypothyroidism), often coexist, although these conditions may be the cause of secondary hypothermia.

The clinical presentation is dependent on the degree and duration of hypothermia.[3] Mild hypothermia is defined as a core body temperature of 90-95°F, and patients may initially show signs of shivering, tachycardia, vasoconstriction, and tachypnea. Later signs include apathy, ataxia, impaired judgment, and diuresis. Moderate hypothermia is a core body temperature of 82.4-89.9°F, and patients may stop shivering and shows signs of dysrhythmia, bradycardia, hypotension, J waves on ECG, diminished reflexes, dilated pupils, and a decreased level of consciousness.

Severe hypothermia is a core body temperature less than 82.4°F, at which point patients may begin to experience apnea, decreased activity on electroencephalography (EEG), nonreactive pupils, oliguria, pulmonary edema, coagulopathy, hemoconcentration, and more severe arrhythmia. In general, the life-threatening cardiovascular complications of hypothermia are cardiogenic shock and malignant dysrhythmias.[3]

Initial stabilization begins with establishing an accurate, continuous means of measuring the core body temperature in order to detect the degree of hypothermia and the response to therapy. Electronic oral thermometers may report an error at low temperatures; therefore, patients may need to have a rectal, esophageal, or bladder thermometer inserted for continuous measurements. Any wet clothing should be removed immediately.

Patients in respiratory failure should be intubated; mechanically ventilated; and given warmed, humidified, supplemental oxygen. Oral intubation is preferred because of the risk for epistaxis in these coagulopathic patients. Volume resuscitation should be initiated with warmed (104-113°F) normal saline—not lactated Ringer solution, because the shocked liver cannot metabolize the lactate.[3]


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