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Accidental Hypothermia
Laura Klouda, MD
• Definition
– Unintentional drop in body temperature of about 2°C from
“normal” (normal = 37.2-37.7°)
• Contributing factors/stressors
Extremes of age
Nutritional status/dehydration
Pre-existing health conditions
Intoxicants/medications that potentially decrease thermostability
Exposure type
Fatigue and lack of sleep
Wet clothing
• Treatment depends on duration and severity of
hypothermia and contributing factors/stressors
Nervous system effects
• Shivering (more effective at producing heat than voluntary
muscle contraction)
• Memory loss
• Impaired judgment
• Decreased level of consciousness
• Slurring of speech
Cardiovascular effects
• Bradycardia
– Due to slowed pace-maker cell depolarization
refractory to atropine
• Decreased cardiac output
• EKG changes
– Prolonged PR, QRS, and QTc
– J (Osborn) waves
• Dysrhythmias
• All of these can be worsened during afterdrop
– Afterdrop is a drop in core temp after the warming
process has begun
Respiratory effects
• Initially tachypnea
• Bradypnea as hypothermia worsens
– Thus CO2 retention and respiratory acidosis
• Noncardiogenic pulmonary edema
• Increased and thickened secretions
Renal effects
• Decreased blood flow to kidneys 
decreased glomerular filtration rate 
results in build up of nitrogenous waste
• An initial large diuresis results in
hemoconcentration. Then followed by
Effects on coagulation
• Bleeding
– Due to cold-induced hypercoagulability and
– Appears similar to DIC (disseminated
intravascular coagulation)
• Hyperviscosity of blood due to
hemoconcentration from diuresis and also
from stiffening of red blood cells
Physical exam findings
– Mydriasis, decreased extraocular movements, facial edema and/or flushing,
epistaxis and/or rhinorrhea
• Cardiovascular
– Initial tachycardia followed by bradycardia, dysrhythmia, jugular venous
distension, hypotension
• Respiratory
– Initial tachypnea followed by bradypnea/apnea, increased adventitious lung
– Constipation, abdominal distension, emesis, polyuria to anuria
• Neuro
– Decreased LOC, ataxia, amnesia, initial hyperreflexia followed by areflexia,
mood/personality changes
• Skin/Musculoskeletal
– Shivering, increased muscle tone, erythema, pallor, cyanosis, frostbite, edema
Pre-hospital management
• Basic principles:
Rescue and remove from cold exposure
Physical exam
Remove wet clothing, stabilize injuries, cover wounds
Body temperature IV fluids if possible
• Place bag under patient’s buttocks or in a compressor
• Warm fluids by taping hand/feet warmers to fluid bag
– Limit rewarming to:
• Hot water bottles covered in stockings/mittens placed in patient’s
– Be cautious not to burn the patient
• Heated insulation
• Inhalation of heated humidified oxygen
– Patient should remain horizontal
– Insulate and wrap patient
• Sleeping bags, clothing, tents, etc.
– Transport to hospital
– Only consider surface re-warming if medical care is unavailable
• Body-body contact, warm objects, radiant heat
Pre-hospital life support
• Avoid jostling or quick movements of comatose
– They are extremely likely to go into ventricular
fibrillation if jostled
• Primary objective = prevent further heat loss
• Never assume death when patient is still cold.
“No one is dead until warm and dead”
IV glucose, naloxone, and flumazenil
Pre-hospital life support
• Rescue breathing may be difficult due to stiffened muscles
• Common problem is overventilation causing hypocapnic ventricular
• Indications for intubation are the same as for a normothermic
– Avoid overinflation of the cuff in freezing temperatures. The cuff will
expand upon reaching warmer temps  can kink tube and/or damage
• Palpate/auscultate pulses for a full minute before deciding if patient
requires chest compressions
– Often bradycardic with low cardiac output
– Unnecessary chest compressions can cause ventricular fibrillation
• If cardiac monitor and defibrillator available:
– Defibrillate if ventricular fibrillation or asystole
– Pads generally don’t stick well to cold skin
• May need tincture of benzoin
Emergency Department Care
• IV/O2/Monitor
• Warmed IV normal saline
• Monitor vitals and confirm hypothermia
– Doppler may be needed to obtain a pulse
– Rectal thermometer inserted 15cm or esophageal temps are generally
• Thermal stabilization
– Heat via conduction/convection/radiation/respiration
• Maintain tissue oxygenation
– CPR/rescue breathing
• Determine 1° vs 2° hypothermia
• Obtain labs: CBC, blood gas, CMP, INR, PTT, fibrinogen
• Rewarm
– Passive external, active external, and/or active core rewarming
• Treat injuries, infections, underlying medical problems
Passive external rewarming
• Ideal for mild hypothermia
• Insulation with blankets, aluminized body
covers, etc.
Active Rewarming
• For moderate-severe hypothermia (T<32°C),
passive warming failure, peripheral vasodilation,
secondary hypothermia, endocrine insufficiency
External warming
– Hot water bottles, forced circulated hot air e.g. Bair
Hugger, heating blankets, etcapply to THORAX, not
• Core warming
– Heated humidified oxygen, heated IV fluids,
gastric/colonic/mediastinal/thoracic/peritoneal lavage
with warm saline, extracorporeal blood rewarming
Medications in hypothermia
• Medications are temperature dependent
• Often ineffective during hypothermia then
become toxic during warming
Poor GI absorbtiondo not give oral meds
Erratic intramuscular absorbtionavoid IM meds
Hypothermia summary
• Symptoms often vague, wide variety of presenting symptoms
• Pre-hospital treatment
Remove wet clothing, stabilize injuries
Limit rewarming
Gentle handling, keep horizontal
Transport to hospital
Warmed IV normal saline
CPR/rescue breathing
Passive external, active external, and/or active core rewarming
Treat injuries, infections, underlying medical problems
• Emergency Dept Treatment
• Reference:
• Auerbach, P.S. (1995), Wilderness
Medicine, 3rd edition. Mosby.