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  Cardiac arrest is defined by a triad of derangements:

  
  
  
  
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    Pulselessness

    
    
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    Apnea

    
    
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    Unresponsiveness

  
  
  
  
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  This state leads to progressive tissue ischemia and organ dysfunction, which, if not rapidly corrected, can result in irreversible deterioration of cardiac and neurologic function.

  
  
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  Cardiac arrest occurs in 2% to 6% of pediatric patients who are admitted to the pediatric intensive care unit.

  
  
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  Cardiac arrest occurs in approximately 16,000 children out of hospital in the United States each year.

  
  
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  Because of the relative infrequency of out-of-hospital events, pediatric resuscitations are not common for providers outside of the pediatric intensive care unit.

  
  
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  There continues to be a significant difference in outcomes (e.g., favorable vs. nonfavorable) between patients with in-hospital vs. out-of-hospital events.

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  In general, the cause of cardiac arrest falls into one of three categories:

  
  
  
  
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    Asphyxia

    
    
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    Ischemia

    
    
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    Arrhythmia

  
  
  
  
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  Adults with cardiac arrest often have sudden, unexpected ventricular fibrillation and often have underlying coronary artery disease, which leads to myocardial ischemia.

  
  
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  In contrast, pediatric cardiac arrest is rarely caused by a sudden coronary event or arrhythmia.

  
  
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  Cardiac arrest in children is most often caused by progressive asphyxia from acute hypoxia or hypercarbia, which leads to acidosis and nutrient depletion.

  
  
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  Ischemic events are the second most common etiology in pediatrics.

  
  
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  Ischemic events occur secondary to inadequate myocardial oxygen delivery, which in children occurs most commonly in the setting of sepsis, hypovolemia, or myocardial dysfunction.

  
  
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  Arrhythmias account for the smallest number of cardiac arrest events in pediatric patients, comprising only 10% of events.

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  Cardiac arrest can be broken down into four phases:

  
  
  
  
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    Prearrest

    
    
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    No flow (untreated cardiac arrest)

    
    
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    Low flow (cardiopulmonary resuscitation [CPR])

    
    
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    Postresuscitation

  
  

PREARREST

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  Pediatric patients with in-hospital cardiac arrest may have physiologic changes in the hours leading up to their arrest.

  
  
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  Because the majority of pediatric cardiac arrests occur secondary to progressive asphyxia or ischemia, recognition and treatment of respiratory failure and shock states may prevent a number of arrest events from occurring.

  
  
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  The Pediatric Advanced Life Support (PALS) course was designed to reduce the number of cardiac arrests by improving the early recognition of these conditions.

  
  
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  Care during this phase should focus on:

  
  
  
  
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    Identifying and treating reversible conditions

    
    
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    Optimizing patient monitoring

    
    
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    Providing rapid emergency response for patients not already in a health care setting

  
  

NO FLOW (UNTREATED CARDIAC ARREST)

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  During untreated cardiac arrest, circulation has stopped.

  
  
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  Responders to cardiac arrest should minimize time in this state in order to optimize patient outcomes.

  
  
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  Interventions should focus on the initiation of Basic and Advanced Life Support techniques.

LOW FLOW (CPR)

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  The low-flow phase begins with the initiation of resuscitation measures (chest compressions).

  
  
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  Effective CPR improves coronary perfusion pressure and provides cardiac output to support organ viability.

  
  
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  Even with optimal CPR, cardiac output is only 10% to 25% of normal. Basic Life Support (BLS) and PALS guidelines should be followed during the resuscitation phase.

  
  
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  Responders should push hard and fast and should allow for complete chest recoil to maximize cardiac filling.

  
  
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  Care should be taken to minimize interruptions to CPR and to avoid overventilation.

  
  
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  Code medications should be administered according to PALS guidelines. See Table 7-1.

  
  
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  Further research on goal-directed endpoints (end tidal CO₂, etc.) is necessary, but a sudden increase in end-tidal CO₂ suggests return of spontaneous circulation.