Hypothermia Algorithm

  • Mild hypothermia → tachypnea, tachycardia, hyperventilation, ataxia, shivering, impaired judgment, “cold diuresis”
  • Moderate → bradycardia, hypoventilation, CNS depression, loss of shivering, slow A-fib + other arrhythmias
  • Severe → pulmonary edema, oliguria, coma, pupils fixed/dilated, ventricular arrhythmias, asystole
Hypothermia Algorithm
Hypothermia Algorithm

Cardiac Arrest from Hypothermia

Futile? Consider termination of efforts if :

  • Irreversible injury ?
    • Decapitation, truncal transection, decomposition of the whole body, and a chest wall that is not compressible (the whole body is frozen solid)
  • K+ (potassium) > 10-12 mmol/L
  • Cardiac arrest prior to cooling
    • Difficult to differentiate from a patient that died and then became hypothermic → resuscitation would obviously be futile
    • Better outcome if patients were cooled before heart stopped
  • Asystole and Temp > 32°​C
    • Hypothermia is then not the cause of arrest

Special Cases (trauma, drowning, avalanche)

  • Trauma
    • Hypothermia will decrease survival of blunt trauma
  • Drowning
    • Submersion
      • Patient under water immediately → drowns → hypoxic arrest → then cools down
      • Worse prognosis, case report of survival
    • Immersion (rare)
      • Patient in water and continues breathing → cools → hypothermic arrest
  • Avalanche (3 ways to die)
    • Traumatic arrest
    • Hypoxic arrest (airway filled with snow)
    • Hypothermic arrest
      • Patient must be buried long enough to cool → then arrest
      • Rate of cooling 10oC/h so must be buried at least 35 minutes

Continued CPR/Resuscitation

  • Because of neuroprotective effects of hypothermia → complete recovery is possible even if prolonged resuscitation (hours)
    • Survival and neurological recovery reported in temperatures as low as 13.7°C and cardiac arrest > 9 hours (Lancet 2000;355:375-6)
    • Continue resuscitation until temperature is 32-35°C

Modified ACLS

  • CPR, Intubation
  • Rapid re-warming: ECMO/CPB
  • Resuscitate until temp >32°C (90°F)
  • Defibrillate x1 (VF) trial then rewarm
  • Epinephrine x 1 trial then rewarm vs up to 3 doses
  • ACLS recommendations


  • Define: Extracorporeal Membrane Oxygenation(ECMO) / Cardiopulmonary Bypass (CPB)
  • Indications:
    • Cardiac arrest (Hypothermia stage IV)
      • Hypothermic patients who experience cardiac arrest have a survival rate of 50% when treated in an ECMO center but only 10% in a non-ECMO center
    • Cardiac instability refractory to medical management (Hypothermia stage III)
      • SBP < 90, ventricular arrhythmias, temp < 28oC
  • In patients with ROSC, multiorgan failure is expected → respiratory support with ECMO may be required.

Termination of CPR

  • Consider termination if temp > 32oC and persistent cardiac arrest, not responsive to epinephrine and defibrillation

Hypothermia Resuscitation


  • Risk of causing VF very low and outweighed by benefits of reliable ventilation, oxygenation, prevention of aspiration – especially if comatose or respiratory failure


  • Treat all patients empirically for sepsis
  • IVF (warmed), antibiotics, labs, blood cultures, lactate
  • See Sepsis algorithm

Re-warming and Hypothermia Stages


  • Degree of hypothermia and mortality will determine the aggressiveness of re-warming
Hypothermia Stage I32-35 °​CConscious Shivering
Hypothermia Stage II28-32 °​CImpaired consciousness, No shivering
Hypothermia Stage III24-28 °​CUnconscious, No shiver, Patient has vital signs
Hypothermia Stage IV<24 °​CNo vital signs
Hypothermia Stages

Hypothermia Stage I

  • Clinical: conscious, shivering
  • Treatment
    • Passive External Rewarming (0.5-2°C/h)
      • Remove wet clothing
      • Warm room/blankets

Hypothermia Stage II

  • Clinical: Impaired consciousness, not shivering
  • Treatment
    • Avoid arrhythmias
      • Cardiac monitor
      • Minimal/cautious movements
      • Horizontal position and immobilization
    • Active external/minimally invasive Re-warming (1-2.5°C/h)
      • Bair Hugger
      • Heat pads/blankets
      • Trunk only
      • Warm IV Fluids (38-42°​C)
      • Indications (N Eng J Med 1994;331:1756-60):
        • i. Cardiovascular instability, poikilothermia (T<32°C), failure to re-warm, comorbidities

Hypothermia Stage III

  • Clinical: Impaired consciousness, not shivering, patient has vital signs
  • Treatment
    • Hypothermia Stage II treatments
    • Airway management as required
    • ECMO/CPB (cardiac instability refractory to medical management)

Hypothermia Stage IV

  • Clinical: Cardiac arrest, no vital signs
  • Treatment
    • Hypothermia Stage II and III treatments
    • ACLS: CPR, Intubation, epinephrine, defibrillation
    • ECMO/CPB if available (N Engl J Med 1997;337:1500-5) (Resuscitation 2003;59:285-90)
      • Rate of survival without neurologic impairment is 47 to 63% (vs 37% without ECMO/CPB)
      • Cardiopulmonary bypass (CPB) for severe hypothermia and cardiac arrest showed survival rate of 47-63% with minimal to no cerebral impairment, even after prolonged cardiac arrest
    • Active external and alternative internal rewarming (ECMO/CPB not available)
      • Thoracic lavage with chest tubes
      • Bladder lavage?

Complications of Hypothermia

  • Rescue collapse
    • Define: cardiac arrest that is related to the extrication and transport of a patient with deep hypothermia (stage Hypothermia III)
    • Cause: circulatory collapse due to hypovolemia, cardiac arrhythmias triggered by interventions, and further cooling
  • Core temperature after drop
    • Extremities and trunk are warmed simultaneously → cold, acidemic blood in periphery returns to core → drop in temperature and acidosis
  • Rewarming shock
    • Peripheral vasodilation → hypotension, low coronary perfusion → fatal arrhythmias (VF)
    • Prevention: maintain horizontal, re-warm trunk before extremities
  • Arrhythmias
    • Avoid jarring pt, no high central lines, gentle movement of patient → irritating myocardium may cause VF
    • Most (A-fib, A-flutter) resolve spontaneously during re-warming
    • Normal course: bradycardia → slow A-fib → VF → Asystole (refractory to conventional tx, must be rewarmed!)
    • EKG changes with hypothermia
      • Intervals prolonged: PR, QRS, QT
      • J point elevation (Osborne wave – characteristic but not pathognomonic: also seen in hypercalcemia and head injury)
  • Failure to re-warm
    • Evaluate for adequate aggressiveness for severity of hypothermia
    • Evaluate for reversible causes (hypoglycemia)
    • Underlying infection?
  • Coagulopathy
    • Cold directly inhibits enzymes of coagulation cascade and platelets → normal laboratory evaluation
    • Hypercoagulability also present → can lead to thromboembolism; DIC
  • Cold induced bronchorrhea
    • Intubation? Airway protection → prevent aspiration
  • Cold induced diuresis
    • Usually diuresed 2-5L, replace with warmed IV Fluids
  • Rhabdomyolysis
    • Tissue ischemia and cellular destruction by freezing tissue

Causes of Hypothermia

  • Environment
    • Urban hypothermia
      • Most common cause is environmental exposure with acute alcohol intoxication
    • Expedition hypothermia
  • Sepsis/Infection
    • Treat all patients empirically for sepsis
    • Associated with slower re-warming rates (above)
    • Begin empiric broad spectrum antibiotics and sepsis work-up
  • Hypothyroidism/Myxedema Coma