0071643192.pdf

ENVIRONMENTAL EMERGENCIES

Hypothermia is clinically defined as mild, moderate, or severe.

■ Mild hypothermia (32°– 35 °C):

■ Excitation stage: Characterized by physiologic responses to generate

heat

■ Moderate hypothermia (30°– 32 °C):

■ As temperature drops below 32°C, shivering ceases and victim enters a

stage of general slowing of body functions = adynamic stage.

■ Severe hypothermia (<30°C)

■ Patient appears dead. Ventricular fibrillation risk increases.

PATHOPHYSIOLOGY

■ As core temperature ↓→peripheral vasoconstriction (to limit further radiant

heat loss) and shivering (to increase heat production).

■ Further decrease in temperature →generalized slowing of body functions.

■ Leftward shift of oxyhemoglobin dissociation curve→decreased release

of O 2 to tissues.

■ Renal dysfunction and peripheral vasoconstriction (central hypervolemia)

→cold diuresis→dehydration.

SYMPTOMS/EXAM

■ Mild hypothermia:

■ Tachycardia and tachypnea

■ Hyperactive reflexes

■ Shivering

■ Moderate to severe hypothermia:

■ Mental status change ranging from poor judgment to lethargy to coma

■ Pupils may become fixed and dilated.

■ Poor coordination, dysarthria

■ Bradycardia or ANY atrial/ventricular dysrhythmia

■ Hypoactive reflexes, muscular rigidity

DIAGNOSIS

■ Based on history of exposure and core body temperature

■ ECG:

■ Classic ECG = Osborne (“J”) waves appear at junction of QRS com-

plex (see Figure 13.4).

■ ST segment and QT interval are often prolonged.

■ Anydysrhythmia may occur.

■ ABG:

■ Must be corrected for core body temperature

■ Laboratory studies:

■ Hemoconcentration is common.

■ Clotting factor dysfunction

■ Thrombocytopenia

■ Hyperglycemia or hypoglycemia may be present.

■ Others, as indicated

TREATMENT

■ Start with ABCs:

■ Continuous core temperature measurement

■ Passive rewarming:

■ For mild hypothermia

■ Blankets

With temperatures <30°C

(severe hypothermia), the

patient appears dead and the

VFib risk increases.

Patients with exposure to cold

develop a “cold diuresis,”

resulting in dehydration.

Osborne “J” waves are classic

for moderate to severe

hypothermia, but may be seen

in other conditions.

Three general methods of

rewarming:

Passive (noninvasive)

rewarming

Active external rewarming

Active core rewarming