Description

• Accidental hypothermia is the result of an unanticipated environmental exposure to cold temperatures. It is manifested as a core temperature of <35°C (95°F) and it may take hours to days to develop (1).
• Although patients with cold-water immersion may appear dead, they can sometimes be resuscitated; therefore, it is important to evaluate, treat as indicated, rewarm, and reassess (2).
• System(s) affected: all body systems
• Synonym(s): accidental hypothermia

Epidemiology

• Predominant age: young children and elderly
• Predominant sex: male > female

Geriatric Considerations
More common in elderly due to lower metabolic rate, impaired ability to maintain normal body temperature, and impaired ability to detect temperature changes (2)

Incidence
From 1999 to 2011, the CDC reported 16,911 deaths due to hypothermia.

Prevalence
Estimates vary widely; typically a secondary issue

Etiology and Pathophysiology

Core temperature is typically tightly maintained between 36.5 and 37.5°C. Accidental hypothermia is most often the result of overwhelming environmental cold stress. Other contributing factors include the following (1):

• Decreased heat production (e.g., hypopituitarism; hypothyroidism; adrenal insufficiency) (1)
• Increased heat loss (e.g., immersion—this is the most commonly encountered form of hypothermia in emergency situations—or burns) (1)
• Alcohol consumption (contributes in up to 68% of cases) (1)
• Impaired thermoregulation (e.g., stroke, central nervous system [CNS] tumors) (1)

Pediatric Considerations

• Children are at greater risk for hypothermia due to a larger ratio of surface area to body mass (2).
• Young infants cannot increase heat production through shivering and children have limited glycogen stores to maintain heat production.
• Children and infants have a decreased ability to recognize, avoid, or escape hypothermic exposure. Also, the history may not suggest hypothermia. Hypothermia does not require extreme exposure in children. Nonaccidental trauma may contribute.

Risk Factors

• Alcohol consumption; drug intoxication
• Bronchopneumonia
• Cardiovascular disease; cardiac arrest
• Cold-water immersion; prolonged environmental exposure
• Dermal dysfunction (burns, erythrodermas)
• Endocrinopathies (myxedema, severe hypoglycemia)
• Excessive fluid loss, malnutrition
• Hepatic failure; renal failure/uremia; sepsis
• Hypothalamic and CNS dysfunction
• Mental illness; Alzheimer disease
• Trauma (especially head) (1),(2)

General Prevention

• Appropriate clothing, with particular attention to head, feet, and hands (1).
• For outdoor activities, carry survival bags with rescue foil blanket and dry clothes for use if stranded or injured.
• Avoid alcohol.
• Remain alert to early symptoms and initiate preventive steps (e.g., drinking warm fluids, getting out of the cold) (1).
• Identify medications that may predispose to hypothermia (e.g., neuroleptics, sedatives, hypnotics, tranquilizers) (1).

Commonly Associated Conditions

• Addison disease; hypothyroidism; hypopituitarism; diabetes; ketoacidosis (2)
• CNS dysfunction
• Congestive heart failure
• Pulmonary infection; sepsis
• Uremia