1 figure omitted
Hypothermia, a preventable lowering of the core body temperature to
<95°F (<35°C),1 causes approximately 600 deaths each
year in the United States.2 Exposure to excessive cold (or excessive
exposure to cold) slows enzymatic activity throughout the body, leading to
potentially fatal rhabdomyolysis, coagulopathy, renal failure, and dysrhythmias.3 Alcohol intake, activity level, and type of clothing are among the
modifiable factors associated with hypothermia.4 Understanding
the epidemiology and pathophysiology of hypothermia is important to preventing
hypothermia-related mortality. This report describes three cases of fatal
hypothermia that occurred during 2003, reviews national statistics on mortality
from cold exposure in 2001, and provides recommendations for the diagnosis,
treatment, and prevention of hypothermia. Public health strategies tailored
to U.S. populations at increased risk for exposure to excessive cold can help
reduce mortality and morbidity from hypothermia.
Case 1. In the fall of 2003, a man aged 44
years was found dead outdoors in Vermont. He wore a T-shirt, long-sleeved
shirt, two sweatshirts, underpants, pants, socks, and boots. His clothes were
wet, and an empty vodka bottle was nearby. Local investigators reported that
he looked as though he "lay down and went to sleep." Overnight, the temperature
had dropped to <32°F (<0°C). Autopsy findings were unremarkable
except for a fatty liver. A toxicology screen was negative except for an elevated
blood alcohol concentration (BAC) of 0.30 g/dL, nearly four times the legal
intoxication limit of 0.08 g/dL in Vermont. Cause of death was certified as
hypothermia, with alcohol intoxication as a contributing factor.
Case 2. In the spring of 2003, a man aged 76
years with Alzheimer's disease was reported missing from his home in Vermont.
The next day, a farmer found the man lying in a swampy area where his car
had become stuck in the mud. Overnight, the temperature had dropped to <32°F
(<0°C). The man was pronounced dead at the scene; cause of death was
hypothermia precipitated by a cold, wet environment.
Case 3. In the fall of 2003, Alaska state troopers
reported that a hiker aged 35 years was found dead alongside a highway. The
hiker was not clothed from the waist up and was missing a shoe. The overnight
temperature was 44°F (6.7°C), but conditions were wet and windy. The
hiker's BAC was 0.28 g/dL, nearly four times the legal intoxication limit
of 0.08 g/dL in Alaska; his toxicology screen was positive for cocaine and
marijuana. Cause of death was hypothermia, with drug and alcohol intoxication
as contributing factors.
In the United States, certain populations (e.g., alcoholics; drug users;
elderly, homeless, and chronically ill persons; and those with preexisting
heart disease) are at increased risk for dying from hypothermia. During 2001,
a total of 599 persons in the United States2 died from "exposure
to excessive natural cold" (code X31), as categorized in the International Classification of Diseases, Tenth Revision. Of these
victims, 67% were male, and 51% were aged >65 years. As persons age, their
risk for dying from hypothermia increases. Approximately 71% of the hypothermia-related
deaths in 2001 occurred during November-February. The three states with the
highest rates of death from hypothermia were Montana (1.44 persons per 100,000
population), Alaska (1.42), and New Mexico (1.04).
S Shapiro, MD, P Morrow, MD, Vermont Dept of Health. F Fallico, MD,
Alaska Dept of Health and Social Svcs. E Azziz Baumgartner, MD, EIS Officer,
Hypothermia causes multiple dysfunctions, including cardiac arrhythmias,
renal insufficiency, and hemoconcentration. In late stages of hypothermia,
brain function deteriorates, predisposing persons to poor judgment and increasing
their risk for further exposure to excessive cold.
Improper clothing and comorbidities can interfere with the balance between
the body's heat production and cooling. Wet clothing cannot retain body heat;
warm clothing keeps the body dry and helps to decrease heat loss, which can
save a person's life during excessively cold weather. Advanced age, immobility,
and existing medical conditions can increase the risk for hypothermia and
death during cold weather. Certain medical conditions (e.g., hypothyroidism,
congestive heart failure, and diabetes) can affect a person's ability to recognize
warning symptoms of hypothermia, compensate for the cold, or to seek shelter
from the cold.
Use of alcohol or other mood-altering drugs often is associated with
cases of hypothermia. The vasodilatation caused by alcohol provides a sensation
of warmth but also increases heat loss through radiation. In addition, alcohol
and other drugs impair hand coordination, mobility, and decision-making abilities.
Treatment of hypothermia focuses on returning the core body temperature
to normal while providing supportive care. The method chosen to rewarm a patient
depends on the severity of the hypothermia (see box ).
With rewarming and supportive care, even persons who appear to be dead might
Prevention of hypothermia requires public health strategies that target
persons at greatest risk. Such strategies can include creating community programs
for checking on the well-being of elderly persons, opening temporary shelters
for the homeless, and urging persons with cardiovascular disease to avoid
outdoor exercise during cold weather.6
References: 6 available
Hypothermia-Related Deaths—United States, 2003. JAMA. 2004;291(13):1556-1557. doi:10.1001/jama.291.13.1556