II. Definition

  1. Core Temperature <95 F (35 C)

III. Epidemiology

  1. U.S. Deaths: 700 per year (50% are over age 65 years)

IV. Risk Factors

  1. Extremes of age
  2. Alcohol Intoxication
  3. Comorbid illness

V. Causes

VI. Mechanism

  1. Radiative heat loss (50% of heat loss)
    1. Majority of radiative Hair Loss via head (60%)
  2. Conductive heat loss (2-3% of heat loss)
    1. Wet clothing: Heat loss increases x5
    2. Cold water immersion: Heat loss increases x25
  3. Convective heat loss (10%)
    1. Important in windy conditions
    2. Convective loss increases with shivering
  4. Evaporative heat loss (Up to 27%)
  5. Respiratory heat loss (Up to 9%)

VII. Exam: Core Temperature

  1. Precautions
    1. Oral or infrared tympanic thermometers should not be used
    2. Use calibrated, low-reading thermistor
  2. Utility
    1. Most useful to define when core Temperature >32 degrees C (90 F)
  3. Methods
    1. Esophageal (preferred)
      1. Insert to level distal to carina
    2. Rectal
      1. Insert to at least 15 cm depth
      2. Reading may lag true core Temperature during rewarming efforts

VIII. Signs: General

  1. Altered Mental Status
  2. Shivering
  3. Flushing
  4. Facial edema
  5. Initial Tachycardia progresses to Bradycardia
  6. Hypotension
  7. Paradoxical undressing
  8. Respiratory depression
  9. Ataxia
  10. Decreased Corneal Reflex

IX. Signs: Mild Hypothermia (Hypothermia Stage I)

  1. Core Temperature: 95 to 90 F (35 to 32.2 C)
  2. Initial reaction to cold
    1. Shivering
    2. Increased Respiratory Rate, pulse and Blood Pressure
    3. Vasoconstriction
  3. Later with glycogen depletion and Fatigue
    1. Amnesia
    2. Ataxia
    3. Apathy
    4. Hypovolemia
    5. Cold diuresis
    6. Dysarthria
    7. Poor judgment

X. Signs: Moderate Hypothermia (Hypothermia Stage II)

  1. Core Temperature: 90 to 82.4 F (32 to 28 C)
  2. Cardiac arrhythmia
    1. Atrial arrhythmia
    2. EKG with J Wave
  3. Altered Level of Consciousness to stupor
  4. Loss of reflexes
  5. Mydriasis
  6. Decreased Respiratory Rate, pulse and Blood Pressure
    1. Bradycardia: Heart Rate decreases by 50%
  7. Loss of voluntary control

XI. Signs: Severe Hypothermia (Hypothermia Stage III)

  1. Core Temperature: 82.4 to 75 degrees F (28 to 24 C)
  2. Major acid-base disturbance (Metabolic Acidosis)
  3. Pupils do not react and no Corneal Reflex
  4. Apnea
  5. Coma
  6. Flat or decreased Electroencephalogram (EEG) activity
  7. Ventricular arrhythmias (e.g. Ventricular Tachycardia, Ventricular Fibrillation)
  8. Oliguria

XII. Signs: Very Severe Hypothermia (Hypothermia Stage IV)

  1. Core Temperature: < 75 degrees F (24 C)
  2. Asystole

XIII. Labs

  1. Bedside Glucose
    1. Hypoglycemia
  2. Basic metabolic panel
    1. Acute Renal Failure
      1. Acute Tubular Necrosis due to Rhabdomyolysis
    2. Serum Potassium may change rapidly with rewarming
    3. Serum Glucose (see above)
  3. Creatine Phosphokinase (CPK)
    1. Evaluate for Rhabdomyolysis
  4. Arterial Blood Gas
  5. Coagulation studies
    1. Often normal despite cold-induced coagulopathy

XIV. Diagnostics: Electrocardiogram (EKG)

  1. General findings
    1. PR Prolongation
    2. QRS prolongation
    3. QT Prolongation
    4. J Waves
    5. Findings may mimic Acute Coronary Syndrome
  2. Dysrhythmias
    1. Atrial Fibrillation
    2. Ventricular Fibrillation
    3. Asystole

XVI. Complications

  1. Arrhythmia
  2. Acute Coronary Syndrome
    1. Cold-related Vasoconstriction increases cardiac workload
    2. Increased Afterload is also a risk for Congestive Heart Failure
  3. Coagulopathy
    1. Usually resolves with rewarming
    2. Coagulation labs may be normal (PTT, INR, platelets) despite severe cold-induced coagulopathy

XVII. Precautions: Cardinal Rule

  1. ECMO is very effective in increasing survival rates from severe Hypothermia
    1. See Hypothermia Management
  2. Not dead until warm and dead unless already dead
    1. Patients have survived after low of 56 F (13 C)
  3. Do not cease Resuscitation until rewarmed
    1. Reevaluate after core temp >89.6 F (32 C)
    2. See Hypothermia Management for exceptions

XVIII. References

  1. Herbert and Brown in Herbert (2014) EM:Rap 14(1):1-4
  2. Danzl in Marx (2002) Rosen's Emergency Med, p. 1979-96
  3. Danzl in Auerbach (2001) Wilderness Med, p. 135-77
  4. McCullough (2004) Am Fam Physician 70:2325-32 [PubMed]

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Ontology: Hypothermia, natural (C0020672)

Definition (MSH) Lower than normal body temperature, especially in warm-blooded animals.
Definition (CCC) Abnormal low body temperature
Definition (MEDLINEPLUS)

Cold weather can affect your body in different ways. You can get frostbite, which is frozen body tissue. Your body can also lose heat faster than you can produce it. The result is hypothermia, or abnormally low body temperature. It can make you sleepy, confused and clumsy. Because it happens gradually and affects your thinking, you may not realize you need help. That makes it especially dangerous. A body temperature below 95![DEGREE SIGN]! F is a medical emergency and can lead to death if not treated promptly.

Anyone who spends much time outdoors in cold weather can get hypothermia. You can also get it from being cold and wet, or under cold water for too long. Babies and old people are especially at risk. Babies can get it from sleeping in a cold room.

Centers for Disease Control and Prevention

Definition (NCI_CTCAE) A disorder characterized by an abnormally low body temperature. Treatment is required when the body temperature is 35C (95F) or below.
Definition (NCI) Abnormally low body temperature.
Definition (NCI_FDA) Abnormally low body temperature.
Definition (NCI) Abnormally low body temperature.
Definition (NAN) Body temperature below normal range
Definition (CSP) abnormally low body temperature.
Concepts Finding (T033)
MSH D007035
ICD10 T68
SnomedCT 111949007, 3051004, 248428004, 386689009
LNC MTHU013244
English Hypothermia, Hypothermias, HYPOPYREXIA, TEMPERATURE BODY DECREASE, Decreased Core Body Temperature, hypothermia (physical finding), hypothermia, hypothermia was observed, Body temperature decrease, Body temperature decreased, Temperature body decrease, Hypothermia [Disease/Finding], rndx hypothermia, rndx hypothermia (diagnosis), Hypothermia, natural, body temperature low, subnormal temperature, below normal body temperature, decreased body temperature, subnormal temperatures, body temperature below normal, hypothermic, low body temperature, Hypothermia NOS, Decreased body temperature (finding), Hypothermia - disorder, Body temperature below normal (finding), BODY TEMPERATURE, DECREASED, TEMPERATURE, DECREASED BODY, HYPOTHERMIA, DECREASED BODY TEMPERATURE, State of hypothermia, Decreased body temperature, Body temperature below normal, Temperature subnormal, Hypothermia (finding), hypopyrexia, Hypopyrexia
French HYPOTHERMIE, Température corporelle diminuée, Hypopyrexie, ABAISSEMENT TEMPERATURE GENERALE, HYPOPYREXIE, Température diminuée, Hypothermie
Portuguese HIPOTERMIA, Hipopirexia, Diminuição da temperatura corporal, DIM. DA TERMPERATURA CORPORAL, HIPOPIREXIA, Temperatura corporal diminuída, Hipotermia
Spanish HIPOTERMIA, HIPOPIREXIA, TEMPERATURA CORPORAL DISMINUIDA, temperatura corporal inferior a lo normal, temperatura corporal disminuida (concepto no activo), temperatura corporal disminuida, estado de hipotermia, hipotermia (hallazgo), hipotermia, Temperatura corporal disminuida, Hipotermia
German HYPOTHERMIE, Temperatur des Koerpers erniedrigt, Hypopyrexie, ABSINKEN KOERPERTEMPERATUR, HYPOPYREXIE, Koerpertemperatur erniedrigt, Hypothermie, Unterkühlung
Italian Temperatura corporea diminuita, Ipopiressia, Diminuzione della temperatura corporea, Ipotermia
Dutch temperatuur lichaam verlaging, lichaamstemperatuur verlaging, hypopyrexie, lichaamstemperatuur verlaagd, Hypothermie, Onderkoeling
Japanese 体温低下, 低体温, タイオンテイカ, テイタイオン, 低体温症, 体温異常降下, 低体温(疾患), 低温症
Swedish Sänkt kroppstemperatur
Czech hypotermie, podchlazení, Hypopyrexie, Tělesná teplota snížená, Snížená tělesná teplota
Finnish Hypotermia
Polish Hipotermia
Hungarian Testhőmérséklet csökkenés, Hypopyrexia, Testhőmérséklet csökkent
Norwegian Hypotermi, Kroppsnedkjøling, Lav kroppstemperatur

Ontology: Hypothermia, Accidental (C0274285)

Concepts Injury or Poisoning (T037)
MSH D007035
ICD10 T68
SnomedCT 157720000, 54505002, 212916004
French Hypothermie accidentelle
English accidental hypothermia, Hypothermia - accidental (disorder), Accidental hypothermia, Hypothermia - accidental, Accidental hypothermia (disorder), Hypothermia - accidental (finding), Hypothermia, Accidental, Hypothermias, Accidental, Accidental Hypothermias, Accidental Hypothermia
Norwegian Aksidentell hypotermi
Czech náhodná hypotermie
Spanish hipotermia accidental (hallazgo), hipotermia accidental (trastorno), hipotermia accidental

Ontology: Hypothermia due to exposure (C0413252)

Concepts Injury or Poisoning (T037)
ICD9 991.6
ICD10 T68
SnomedCT 241970005
English Hypothermia, hypothermia (diagnosis), hypothermia, Hypothermia due to exposure (disorder), Hypothermia due to exposure
Italian Ipotermia
Japanese 低体温, テイタイオン
Czech Hypotermie
Korean 저체온증
Hungarian Hypothermia
Dutch Hypothermie, hypothermie
Spanish hipotermia por exposición (trastorno), hipotermia por exposición, Hipotermia
Portuguese Hipotermia
French Hypothermie
German Hypothermie