Author:

JordanMoskoff

Signs and Symptoms

• Mild (35-32.2°C/95-90°F):
  • Initial excitation phase to combat cold:
    • HTN
    • Shivering
    • Tachycardia
    • Early tachycardia followed by bradycardia
    • Tachypnea
    • Vasoconstriction
  • Over time with onset of fatigue:
    • Apathy
    • Ataxia
    • Cold diuresis
    • Defect in distal tubular reabsorption of sodium and water
    • Impaired judgment
• Moderate (32.2-28°C/90-82.4°F):
  • Atrial dysrhythmias
  • Bradycardia:
    • Decreased spontaneous depolarization of pacemaker cells
    • Refractory to atropine
  • Decreased level of consciousness
  • Decreased respiratory rate:
    • Progressive respiratory depression with CO₂ retention
  • Dilated pupils
  • Diminished gag reflex
  • Extinction of shivering
  • Hyporeflexia
  • Hypotension
  • J-wave (Osborn wave) on ECG
• Severe (<28°C/<82.4°F):
  • Apnea
  • Coma
  • Decreased or no activity on EEG
  • Nonreactive pupils
  • Oliguria:
    • Renal blood flow depressed 50%
  • Pulmonary edema
  • Ventricular dysrhythmias/asystole:
    • Cardiac cycle lengthens, resulting in increased intervals

Essential Workup

• Accurate core temperature confirms diagnosis
• Esophageal probe or bladder probe ideal

Diagnostic Tests & Interpretation

Differential Diagnosis

• Environmental
• Sepsis
• Primary CNS disorder
• Metabolic
• Drug induced

Prehospital

• Swiss staging system HT1-HT4 should be used to guide treatment and transport
  • HT I: Clear consciousness with shivering: 35-32°C
  • HT II: Impaired consciousness without shivering: 32-28°C
  • HT III: Unconscious: 28-24°C
  • HT IV: Apparent death: 24-13.7°C
  • HT V: Death due to irreversible hypothermia: less than 13.7°C
• Remove from the cold stress (as gently as possible)
• Keep as horizontal as possible
• Dry patient (when protected from the cold environment) and insulate from the ground
• Place in a hypothermia wrap consisting of insulation, a vapor barrier and preferably a heat source
• Patient is not dead until “warm and dead”:
  • CPR recommended during transport
• Prolonged palpation/auscultation for cardiac activity: 30-45 s
  • Apparent cardiovascular collapse may be depressed cardiac output, often sufficient to meet metabolic demand s
  • In cardiac arrest should be transferred to ECMO capable center

Initial Stabilization/Therapy

• ABCs:
  • Supplemental oxygen
  • Oral and nasotracheal intubation are safe
  • Place nasogastric (NG) tube postintubation
  • Cardiac monitor
  • Warmed D5.9 NS preferred over lactated Ringer:
    • Shivering depletes glycogen
• Remove wet clothing and begin passive external rewarming
• Administer Narcan, D₅₀W (or Accu-Chek), and thiamine to a patient with altered mental status
• Stress-dose steroids (Solu-Cortef 100 mg IV) for known adrenal insufficiency or treatment failure
• Obtain accurate core temperatures using rectal thermometer, esophageal or bladder probe

ED Treatment/Procedures

• Cardiac arrest resuscitation:
  • Arrange for extracorporeal rewarming
  • Most dysrhythmias correct with rewarming alone
  • Ventricular fibrillation induction occurs with rough hand ling, chest compressions, hypoxia, and acid-base changes
  • CPR is less effective owing to decreased chest wall elasticity
  • Withhold epinephrine until temp >30°C, then double interval time until temp >35°C
  • Defibrillation is rarely successful at temperatures <28-30°C
    • Defibrillate 1-3 times and then again post rewarming
    • Once >30°C, if ventricular fibrillation persists consider amiodarone
    • Direct current results in myocardial damage
• Dysrhythmia management:
  • Atrial fibrillation:
    • Commonly <32°C
    • Usually converts spontaneously
  • Malignant ventricular dysrhythmias:
    • Amiodarone drug of choice though limited proof of effectiveness
• Rewarming techniques:
  • Faster rewarming rates (1-2°C/hr) generally have better prognosis than slower rewarming rates (<0.5°C/hr)
  • Active rewarming is necessary at core temperature of <32°C:
    • Internal thermogenesis insufficient to increase body temperature
    • Shivering extinguished
• Passive external rewarming:
  • Ideal technique for most healthy patients with mild hypothermia
  • Must have intact thermoregulatory mechanisms, normal endocrine function, and adequate energy stores
  • Cover the patient with dry insulating material
  • Endogenous thermogenesis must generate an acceptable rate of rewarming:
    • Must increase 0.5-2°C/hr
  • Disadvantage: Core rises very slowly
• Active external rewarming:
  • Delivers heat directly to the skin
  • Safe in previously healthy, young, acutely hypothermic victims
  • Requires intact circulation to remove peripherally rewarmed blood to core
  • Associated with core temperature afterdrop
  • Rewarming shock: Venous pooling in warmed extremities secondary to vasodilatation
  • Cover trunk preferentially
  • Bair Hugger device provides forced warm air: Prevents shock or afterdrop
• Active core rewarming techniques:
  • Airway rewarming (complete humidification at 40-45°C):
    • Administer to all patients
  • Heated IV (40-42°C) D5.9 NS:
    • Administer to all patients
    • Need increased amounts to counteract cold diuresis and vasodilation during rewarming
    • Use blood warmer or calibrated microwave
  • Heated gastric irrigation via NG or orogastric tubes:
    • Not recommended
    • Low amount of surface area
    • Aspiration risk if airway not secured
  • Pleural irrigation (0.9 NS at 30-42°C):
    • Use in severe hypothermia without cardiac activity
    • 2-4 chest tubes; midaxillary and midclavicular bilaterally
    • Contraindicated in patients with cardiac rhythm because the chest tube may induce ventricular fibrillation
  • Heated peritoneal lavage (0.9 NS at 40-45°C):
    • Use in unstable hypothermic patients or stable patients with severe hypothermia whose rewarming rates are <1°C/hr
    • 1-2 catheters
    • Advantageous in patients with overdose or rhabdomyolysis
• Extracorporeal rewarming:
  • Most effective rewarming method
  • Hemodialysis:
    • Initiate for patients with drug overdoses or severe electrolyte disturbances
  • Continuous arteriovenous rewarming:
    • BP must be >60 mmHg
    • Blood circulated through warmer from percutaneously inserted femoral arterial and contralateral venous catheters
  • Extracorporeal venovenous rewarming:
    • Blood is removed via central venous catheter, heated to 40°C, and returned via second central or large peripheral venous catheter
  • Cardiopulmonary bypass:
    • Treatment of choice in severe hypothermia with cardiac arrest
• Additional therapy:
  • Methylprednisolone or hydrocortisone for suspicion of adrenocortical insufficiency or steroid dependence
  • Empiric treatment with levothyroxine only for myxedematous patients

Medication

• Amiodarone: 300 mg IV push (IVP) for ventricular fibrillation followed by 1 mg/min infusion
• Dextrose: D₅₀W 1 amp—50 mL or 25 g (peds: D₂₅W 2-4 mL/kg) IV
• Hydrocortisone: 250 mg IVP
• Levothyroxine: 50-500 mcg IV over several minutes
• Methylprednisolone: 30 mg/kg IVP
• Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IV/IM initial dose
• Thiamine (vitamin B₁): 100 mg (peds: 50 mg) IV/IM

Disposition

Follow-up Recommendations

Social work follow-up for homeless patients with cold exposure and hypothermia

• BrownD, BruggerH, BoydJ, et al. Accidental hypothermia . N Engl JMed. 2012;367:1930-1938.
• HaverkampFJC, GiesbrechtGG, TanECTH. The prehospital management of hypothermia—An up-to-date overview . Injury Int. J. Care Injured. 2018;49(2):149-164.
• PaalP, GordonL, StrapazzonG, et al. Accidental hypothermia-an update . Scand J Trauma, Resusc Emerg Med. 2016;24:111.
• PetroneP, AsensioJA, MariniCP. Management of accidental hypothermia and cold injury . Curr Prob Surg. 2014;51:417-431.
• ZafrenK. Out-of-hospital evaluation and treatment of accidental hypothermia . Emerg Med Clin N Am. 2017;35:261-279.

See Also (Topic, Algorithm, Electronic Media Element)

Frostbite

ICD9

• 778.3 Other hypothermia of newborn

• 780.65 Hypothermia not associated with low environmental temperature

• 991.6 Hypothermia

ICD10

• P80.9 Hypothermia of newborn, unspecified

• R68.0 Hypothermia, not associated w low environmental temperature

• T68.XXXA Hypothermia, initial encounter

SNOMED

• 386689009 Hypothermia (finding)

• 123461000119109 Hypothermia not associated with low environmental temperature (finding)

• 13629008 Hypothermia of newborn (disorder)

• 212916004 Hypothermia - accidental