Rosen & Barkin's 5-Minute Emergency Medicine Consult (385 page)

• Cardiac arrest resuscitation:
  
  • Most dysrhythmias correct with rewarming alone.
    
  • Ventricular fibrillation induction occurs with rough handling, chest compressions, hypoxia, and acid–base changes.
    
  • CPR is less effective owing to decreased chest wall elasticity.
    
  • 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.
      
    • High flow rates must be maintained.
      
    • 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.
      
    • 1–2 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 mm Hg.
      
    • 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 2nd 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
    

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

FOLLOW-UP

• Moderate to severe hypothermia (<32°C)
  
• Young, healthy patients with no comorbid illness who have mild accidental hypothermia (>32°C) that responds well to warming:
  
  • Admit to an observation area.
    
  • Discharge if asymptomatic after 8–12 hr and they remain asymptomatic.
    

• Young, healthy patients with no comorbid illness
  
• Very mild accidental hypothermia (>35°C) that responds well to warming
  
• Safe, warm environment to go to after discharge
  

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

• Defibrillation is rarely successful at temperatures <28–30°C:
  
  • Defibrillate 1–3 times and then again post rewarming.
    
• Atrial fibrillation usually converts spontaneously.
  
• Faster rewarming rates (1–2°C/hr) generally have better prognosis than slower rewarming rates (<0.5°C/hr).
  
• Afterdrop is the continued decline in core temp after removed from cold
  
  • Ongoing conduction of heat from core warming periphery prior to the core
    
• Rewarming shock
  
  • Hypovolemic shock secondary to failure to replete volume during resuscitation.
    

• Brown D,Brugger H, BoydJ, et al. Accidental hypothermia.
  N Engl JMed
  . 2012;367:1930–1938.
  
• Corneli HM. Accidental hypothermia.
  Pediatr Emerg Care.
  2012;28(5):475–480.
  
• Jurkovich GJ. Environmental cold-induced injury.
  Surg Clin North Am
  . 2007;87:247–267.
  
• Laniewicz M, Lyn-Kew K, Silbergleit R. Rapid endovascular warming for profound hypothermia.
  Ann Emerg Med
  . 2008;51(2):160–163.
  
• McCullough L, Arora S. Diagnosis and treatment of hypothermia.
  Am Fam Physician
  . 2004;70:2325–2332.
  

See Also (Topic, Algorithm, Electronic Media Element)

Frostbite

CODES

• 778.3 Other hypothermia of newborn
  
• 780.65 Hypothermia not associated with low environmental temperature
  
• 991.6 Hypothermia
  

BASICS

• Decreased level of effective circulating thyroid hormone leads to decreased metabolic rate and decreased sensitivity to catecholamines.
  
• More common in woman and the elderly
  
• Myxedema coma is a rare, extreme form of hypothyroidism characterized by altered mental status and defective thermoregulation triggered by a precipitating event in a patient with hypothyroidism.
  

• Primary:
  
  • Idiopathic
    
  • Congenital
    
  • Autoimmune:
    
    • Thyroiditis
      
    • Hashimoto disease
      
  • Iatrogenic:
    
    • Postsurgical
      
    • External radiation
      
    • Radioiodine therapy
      
    • Drugs (iodides, lithium, amiodarone, sunitinib, bexarotene, interferons, narcotics, sedatives)
      
  • Neoplasm: Primary (carcinoma) or secondary (infiltration)
    
  • Infection: Viral (rarely aerobic or anaerobic bacteria)
    
  • Iodine deficiency (most common cause worldwide)
    
• Central (very rare):
  
  • Pituitary or hypothalamic disorder induced by drugs or severe illness
    
  • May have other associated hormone deficiencies
    
• Myxedema coma:
  
  • Critical decompensation of a patient with hypothyroidism due to a stress, often during winter months. Stressors include:
    
    • Infection
      
    • Hypothermia
      
    • Intoxication
      
    • Drugs
      
    • Cerebrovascular accident
      
    • Heart failure
      
    • Trauma