Accidental Hypothermia

Thresholds

  • <35 C/95F = Hypothermia
  • <32C/89.6 F – Active rewarming measures
  • <30C/86F – Some avoid external rewarming
  • <28C/82.4F – Indication for ECMO
  • Can shock 3 times then defer further attempts until > 30C

Without Vital Signs

Resuscitate?

Outcomes after resuscitation in hypothermic arrest are not correlated w/ length of CPR time. Properly selected pts can undergo hours of CPR and have neuro intact outcomes. Consider transport to ECMO center in all hypothermic arrest pts.

In general, resuscitation indicated if hypothermia is the cause of arrest – i.e. the pt cooled to below 32 or 28 deg C before arresting. Do not resus if:

  • History or findings of arrest prior to cooling
  • Completely frozen solid – e.g. can’t compress chest
  • Asystole and temp >32 (really even >28)
  • Trauma + hypothermia (dismal prognosis)
  • K+ > 12 (though there is a survivor w/ K+ of 11.9)

Special circumstances:

Drowning: reasonable to resuscitate if cooling before arrest

  • Submersion: Hypoxic arrest before cooling – Do not resus
  • Immersion: Cooling first, then slide below water and arrest – reasonable to resus
  • Peds: Small children can cool very rapidly in cold water and can get protective degree of hypothermia prior to hypoxia even with submersion. Reasonable to attempt resus if you think they might have cooled rapidly.

Avalanche: Victims die of trauma, hypoxia or hypothermia

  • Most rapid rate of cooling would get person cold enough to arrest at 35 minutes
  • If rescued in < 35 min and dead, hypothermia didn’t cause arrest, do not resus
  • If rescued > 35 min and – airway clear, no evidence of massive trauma – reasonable to attempt resus b/c hypothermia could have caused arrest.

 

Resuscitation

  • Trial of shock for V fib
  • Then shock q 1 deg rise in temperature
  • Early consideration for ECMO

 

With Vital Signs

Normal aberrancies in hypothermia:

  • Afib
  • Bradycardia
  • Mild hypotension

Survival of hypothermia + cardiac arrest is 10% in regular hospitals but 50% in ECMO centers. Transport to ECMO center if instability like:

  • Hypotension out of proportion to hypothermia (e.g.SBP <90)
  • Temp < 28 C (especially < 24 C – high risk for malignant dysrhythmia)

Management

  • Low threshold for trauma w/u
  • Some avoid active external rewarming w/ severe cases  (e.g. temp <  30 C)
  • Cautious w/ CVC placement – high risk for precipitating dysrhythmia
  • V-fib – 1-2 trials of defibrillation followed by rewarming and additional trials
  • Thoracic or peritoneal lavage – instill warm water (~42 C) q 15 min followed by drainage
  • Alsius for moderate to severe but stable – rewarming rate (~2-3 F/hr)

ECMO

  • Hypothermic arrest
  • Temp < 28C
  • 66% neuro intact survival for hypothermic arrest at HCMC