New York, NY: McGraw-Hill, 201 1, pp. 1193-1 198.

Hypothermia

Michael T. Cudnik, MD

Key Points

• Intoxication with either alcohol or drugs is very common in patients with hypothermia.

• Most emergency thermometers can not accurately read

body temperatures below 34.4°( (94°F).

• Many hypothermic patients have serious underlying

ill nesses that help contribute to their presentation,

INTRODUCTION

Clinical hypothermia is defined as a core body temperature of

less than 35°C (95°F) and can be clinically stratified by the

core temperature into mild (35°-32°C/95°-89.6°F), moderate

(32°-30°C/89.S0-86°F), and severe ( <30°C/86°F) subtypes.

Hypothermia occurs as the body loses heat from 1 of 4 major

mechanisms: conduction, convection, evaporation, and radiation. Convective (windy environments) and conductive

(cold and wet exposures) mechanisms are responsible for

most cases of accidental hypothermia. Hypothermia can be

further classified as either primary or secondary. Primary

hypothermia occurs when an otherwise healthy person is

unable to compensate for an excessive exposure to cold temperatures. Secondary hypothermia occurs when a comorbid

medical condition (eg, hypothyroidism, sepsis, intoxication)

disrupts a patient's normal thermoregulatory processes.

Although most common in colder climates, hypothermia can occur in any environment. Case reports during

summer months and in hospitalized patients are not

uncommon. In the United States, hypothermia is responsible for approximately 700 deaths annually, with more

than half occurring in patients older than 65 years. Patients

with an initial core body temperature <23°C (73.4°) typically do not survive, and the overall mortality rate of

patients with hypothermia is approximately 40%.

and it is imperative to aggressively identify and treat

these conditions.

• Resuscitative efforts should not be terminated until

defi bri llation remains unsuccessful despite a rewarmed

core body temperature of at least 32°C.

CLINICAL PRESENTATION

..... History

The potential for hypothermia is usually obvious in

patients with significant exposures. Patients may present in

wet clothing, be found outdoors in the cold weather, or be

inappropriately dressed for the environment in which they

live. In the United States, most hypothermic patients are

either intoxicated or suffer from an underlying psychiatric

illness or dementia.

The history or presentation may be less obvious for

patients with mild hypothermia or unknown exposures.

Said patients typically present with nonspecific neurologic

findings, including dizziness, confusion, slurred speech, or

ataxia. Patients with severe hyperthermia may present

comatose or in cardiac arrest.

..... Physical Examination

As with all emergency department (ED) patients, start by

assessing and addressing the patient's airway, breathing,

and circulation (ABCs) and vital signs. Hypothermic

patients may present with unstable airways or absent

pulses. Carefully measure the patient's c ore body temperature by inserting a specialized "low-reading" probe into the

bladder, rectum, or esophagus as this will be pivotal to

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