Emergency Medicine Book

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Accidental Hypothermia

Aka: Accidental Hypothermia, Hypothermia, Hypothermia due to Exposure
  1. See Also
    1. Hypothermia Causes
    2. Hypothermia Management
    3. Rewarming Methods in Hypothermia
    4. Hypothermia Management in the Wilderness
  2. Definition
    1. Core Temperature <95 F (35 C)
  3. Epidemiology
    1. U.S. Deaths: 1500 per year (50% are over age 65 years)
  4. Risk Factors
    1. Extremes of age
    2. Alcohol Intoxication or other Chemical Intoxication
    3. Comorbid illness
    4. Poor
    5. Homeless
  5. Causes
    1. See Hypothermia Causes
  6. Mechanism
    1. Radiative heat loss (50% of heat loss)
      1. Majority of radiative heat 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%)
  7. 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, esp. if intubated)
        1. Insert to level distal to carina
        2. Altered when using warm, humidified oxygen
      2. Bladder
        1. Second most accurate (behind esophageal)
        2. Altered with peritoneal or Bladder lavage
      3. Rectal
        1. Insert to at least 15 cm depth
        2. Reading may lag true core Temperature by as much as 1 hour during rewarming efforts
        3. Altered if inserted into cold stool, or by peritoneal lavage fluid Temperature
  8. Exam: Other Vital Signs
    1. Pulses
      1. Palpate femoral artery or Carotid Artery for 60 seconds (Heart Rate may drop to 0-10 in severe Hypothermia)
    2. Oxygen Saturation
      1. Forehead Pulse Oximetry
  9. 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
  10. 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 (Catecholamine induced)
      3. Vasoconstriction
    3. Later with glycogen depletion and Fatigue
      1. Hypovolemia
      2. Cold diuresis (urine frequency)
      3. Amnesia
      4. Ataxia
      5. Apathy
      6. Fine motor skill difficulty
      7. Poor judgment
  11. Signs: Moderate Hypothermia (Hypothermia Stage II)
    1. Core Temperature: 90 to 82.4 F (32 to 28 C)
    2. Shivering response stops at Body Temperature of 86 F (30 C)
    3. Cardiac arrhythmia (esp. if electrolyte abnormality or acidosis)
      1. Atrial arrhythmia (esp. Atrial Fibrillation)
      2. EKG with J Wave
      3. QT Prolongation
    4. Neurologic changes
      1. Cerebral blood flow drops 6-7% with each 1 C below 30 C
      2. Dysarthria
      3. Agitation or confusion
      4. Altered Level of Consciousness to stupor
      5. Hyporeflexia or loss of reflexes
      6. Loss of voluntary control
    5. Mydriasis (Pupil Dilation)
    6. Hypercoagulable
    7. Decreased Respiratory Rate, pulse and Blood Pressure
      1. Bradycardia: Heart Rate decreases by 50%
      2. Respiratory Acidosis may occur
  12. 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. Coma
    4. Pupils do not react and no Corneal Reflex
    5. Apnea
    6. Muscle rigidity (Rhabdomyolysis may occur)
    7. Flat or decreased Electroencephalogram (EEG) activity
    8. Ventricular arrhythmias (e.g. Ventricular Tachycardia, Ventricular Fibrillation)
    9. Oliguria
    10. Disseminated Intravascular Coagulation may occur
    11. Profoundly decreased Respiratory Rate, pulse and Blood Pressure
      1. Significant Hypotension and pulses may barely be palpable
  13. Signs: Very Severe Hypothermia (Hypothermia Stage IV)
    1. Core Temperature: < 75 degrees F (24 C)
    2. Brainstem reflexes absent
    3. Vital Signs absent
    4. Asystole
  14. Labs
    1. Bedside Glucose
      1. Hypoglycemia and Hyperglycemia may occur
      2. Initial Hyperglycemia (impaired Insulin release and activity, increased sympathetic tone)
        1. Avoid correcting Hyperglycemia (unless severe) until patient rewarmed to >86 F (30 C)
      3. Hypoglycemia occurs with rewarming or with gradual onset Hypothermia (glycogen depletion)
        1. See Hypoglycemia Management
    2. Basic metabolic panel (consider comprehensive metabolic panel to include LFTs)
      1. Acute Renal Failure
        1. Cold diuresis (distal tubules fail to reabsorb water, despite vasopressin) and dehydration results
        2. Rhabdomyolysis causes Acute Tubular Necrosis
        3. Cold-Induced decreased Cardiac Function results in decreased Glomerular Filtration Rate
      2. Serum Potassium
        1. Monitor closely for both Hyperkalemia and Hypokalemia (may change rapidly with rewarming)
        2. Hypokalemia is a response to cooling with intracellular Potassium shift and Na-K pump dysfunction
        3. Hyperkalemia occurs with acidosis and cell death (marker of worse prognosis)
      3. Serum Glucose (see above)
      4. Other electrolytes (Na, Ca, Mg, Cl) are typically stable at core Temperatures above 77 F (25 C)
    3. Creatine Phosphokinase (CPK)
      1. Evaluate for Rhabdomyolysis
    4. Arterial Blood Gas
    5. Complete Blood Count
      1. Hematocrit rises 2% for each 1 C drop
      2. White Blood Cell Count transiently increases with shivering, and then decreases as Hypothermia advances
      3. Thrombocytopenia
    6. Coagulation studies (INR, PTT, Fibrinogen)
      1. Often normal despite cold-induced coagulopathy (but may also be markedly abnormal)
      2. Even minor drops in core Temperature, reduce Clotting Cascade factor activity significantly
      3. After rewarming, Coagulation Factor (and platelet) activity may not return to normal for >1 hour
      4. Consider Fibrinogen in severe Hypothermia (to assess for DIC)
    7. Serum Lipase
      1. Acute Pancreatitis is common in severe Hypothermia
    8. Serum lactate
      1. May be used to help guide fluid Resuscitation
    9. Other labs to consider (contributing factors, or markers of systemic dysfunction)
      1. Serum Troponin
      2. Urine Tox Screen
      3. Thyroid Stimulating Hormone
      4. ACTH and cortisol levels (for Adrenal Insufficiency)
        1. Consider Stress Dose Steroids (Hydrocortisone) in refractory Hypothermia
  15. Diagnostics: Electrocardiogram (EKG)
    1. General findings
      1. PR Prolongation (AV Block)
      2. QRS prolongation (and QRS amplitude decreased)
      3. QT Prolongation
      4. J Waves or Osborn Wave
      5. Findings may mimic Acute Coronary Syndrome (ST changes, T Wave inversion)
    2. Dysrhythmias
      1. Bradycardia
        1. Heart Rate decreases with Temperature
        2. In primary Hypothermia, with core temp 82.4 F or 28 C, Heart Rate of 30-40 bpm is expected
        3. Hypothermia without Bradycardia suggests possible Secondary Hypothermia cause
      2. Atrial Fibrillation
        1. In Hypothermia, Heart Rate with Atrial Fibrillation is typically 60-80 bpm
      3. Ventricular Tachycardia or Ventricular Fibrillation (esp. below 80.6 F or 27 C)
        1. Increased risk with electrolyte abnormalities (e.g. Hyperkalemia or Hypokalemia)
      4. Asystole
  16. Management
    1. See Hypothermia Management
    2. See Rewarming Methods in Hypothermia
    3. See Hypothermia Management in the Wilderness
    4. Field Triage
      1. Mild Hypothermia
        1. Initiate passive and Active External Rewarming
        2. Transport to hospital if any associated injury (e.g. Frostbite, Trauma, Drowning)
      2. Moderate to severe Hypothermia
        1. Initiate passive and Active External Rewarming
        2. Transport to hospital capable of invasive rewarming
        3. If hemodynamic instability or core Temperature <82 F (28 C)
          1. Transport to ECMO capable facility if available (otherwise to nearest hospital with ICU)
    5. General Resuscitation
      1. Feel for a pulse for 1 minute at femoral or carotid (weak, slow pulses are common)
      2. Start CPR if pulseless and perform as would in normothermia
      3. Amplify QRS Complex on highest setting (typically low amplitude spikes in Hypothermia)
      4. Monitoring with End-Tidal CO2, Bedside Ultrasound
      5. Defibrillation (when indicated) is often unsuccessful at core Temperature <86 F (30 C)
        1. Attempt Defibrillation at maximum joules at lower Temperature
        2. Reattempt Defibrillation once Temperature increases above 86 F (30 C)
      6. Other ACLS algorithms may be followed when core Temperature >86 F (30 C)
        1. However, when core Temperature 86-96.8 F (30-35 C), double interval between doses
        2. Anti-arrhythmics are ineffective when core Temperature <86 F (30 C)
        3. Cardiac pacing may be used in refractory Bradycardia with Hypotension despite rewarming
    6. Advanced Airway Management
      1. Same Advanced Airway indications for normothermic patients (regardless of myocardial irritability)
      2. Trismus refractory to paralytics may require Nasotracheal Intubation or Cricothyrotomy
      3. Endotracheal Tube cuff should be underinflated to allow for expansion with re-heating
      4. Use lower doses and longer intervals of anesthetic and neuromuscular agents
      5. Decrease ventilation rates to 4-5 breaths per min with Advanced Airway (8-10 without)
        1. Maintains cerebral blood flow, and oxygen demand, CO2 retention is lower in Hypothermia
    7. Access and Medications
      1. Femoral Central Line is preferred over IJ or Subclavian (less myocardial irritability risk)
      2. Medications should be delivered intravenously (not IM, SQ or PO/NG due to poor absorption)
  17. Complications
    1. Arrhythmia (Ventricular Fibrillation, Ventricular Tachycardia, Atrial Fibrillation)
      1. Risk of Rescue Collapse (Cardiac Arrest during patient extrication and transport) due to myocardial irritability
    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 Factor replacement is not typically recommended
      3. Coagulation labs may be normal (PTT, INR, platelets) despite severe cold-induced coagulopathy
      4. Microinfarctions are common in severe Hypothermia
        1. Related to increased cryofibrinogen resulting in increased blood viscosity
    4. Multisystem organ failure (esp. Trauma patients)
      1. Provoked by Hypothermia, coagulopathy and acidosis
  18. Precautions: Cardinal Rules
    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 55.6 F (13 C), and after 6 hours of CPR
    3. Do not cease Resuscitation until rewarmed
      1. Reevaluate after core temp >89.6 F (32 C)
      2. See Hypothermia Management for exceptions
  19. References
    1. Civitarese and Sciano (2018) Crit Dec Emerg Med 32(2): 3-16
    2. Herbert and Brown in Herbert (2014) EM:Rap 14(1):1-4
    3. Danzl in Marx (2002) Rosen's Emergency Med, p. 1979-96
    4. Danzl in Auerbach (2001) Wilderness Med, p. 135-77
    5. McCullough (2004) Am Fam Physician 70:2325-32 [PubMed]

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
Russian GIPOTERMIIA, ГИПОТЕРМИЯ
Croatian HIPOTERMIJA
Polish Hipotermia
Hungarian Testhőmérséklet csökkenés, Hypopyrexia, Testhőmérséklet csökkent
Norwegian Hypotermi, Kroppsnedkjøling, Lav kroppstemperatur
Sources
Derived from the NIH UMLS (Unified Medical Language System)


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
Sources
Derived from the NIH UMLS (Unified Medical Language System)


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
Sources
Derived from the NIH UMLS (Unified Medical Language System)


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