Pediatric cardiac arrest (PCA) is the cessation of the heart’s mechanical activity, resulting in the absence of a pulse and unresponsiveness. Unlike the sudden collapse often seen in adults, the mechanism of PCA is physiologically distinct and typically represents the final stage of a prolonged period of deterioration. Understanding this root cause is essential for effective prevention and response.
The Primary Driver of Pediatric Cardiac Arrest
The most common cause of cardiac arrest in pediatric patients is not a sudden electrical malfunction of the heart but an event secondary to a lack of oxygen. This is known as an asphyxial arrest, resulting from progressive respiratory failure or uncorrected circulatory shock. The child’s heart muscle is usually healthy but is highly sensitive to oxygen deprivation, referred to as hypoxia.
When the body cannot maintain adequate oxygenation or circulation, the heart muscle begins to fail. The first measurable sign of this failure is often a slow heart rate, or bradycardia, as the heart attempts to conserve energy in the low-oxygen environment. Bradycardia indicates the heart is struggling to pump blood effectively.
If the oxygen debt continues, the heart’s electrical activity eventually becomes disorganized and ceases to produce a palpable pulse. The final rhythm is most frequently asystole (a flatline) or pulseless electrical activity (PEA), where electrical activity exists but does not generate a sufficient heartbeat. This progressive sequence—hypoxia, bradycardia, and then asystole—is the hallmark of the majority of pediatric cardiac arrests.
Common Underlying Events and Conditions
While the final physiological driver is hypoxia, the specific triggers that initiate respiratory failure or shock are varied. Respiratory causes are the most prevalent category, accounting for a majority of pediatric cardiac arrests. These include severe infections, such as bronchiolitis or pneumonia, or sudden mechanical obstructions, like foreign body aspiration or drowning.
Circulatory shock is the second major pathway to asphyxial arrest, where inadequate blood flow leads to poor oxygen delivery to the tissues. Sepsis, a widespread infection causing organ dysfunction, is a significant trigger, as it causes massive dilation of blood vessels and a drop in blood pressure. Severe trauma, particularly involving head or chest injuries, can cause profound blood loss or damage to the respiratory system, rapidly leading to shock.
Other specific conditions, such as sudden infant death syndrome (SIDS), are also classified under this umbrella, as they are often associated with respiratory or arousal failure. In all these cases, the heart stops working because the body’s inability to deliver oxygen and nutrients overwhelms the cardiovascular system.
The Difference from Adult Cardiac Arrest
The mechanism of pediatric cardiac arrest differs from the most common presentation in adults, which is a primary cardiac event. Adult cardiac arrests are caused by underlying heart disease, such as coronary artery disease, leading to a sudden, chaotic electrical rhythm called ventricular fibrillation (VF). This means the adult heart is often the initial problem while the lungs are still functioning.
In children, VF and pulseless ventricular tachycardia (VT) are the initial arrest rhythms in only a small percentage of cases, ranging from 5% to 15%. This distinction dictates the initial steps of resuscitation. Adult cardiac arrest prioritizes immediate chest compressions and defibrillation to correct the electrical problem.
Because the pediatric heart stops due to a lack of oxygen, resuscitation efforts must prioritize ventilation and oxygen delivery to reverse the process. The focus is on correcting the underlying respiratory or circulatory failure rather than a sudden electrical malfunction.
Recognizing and Responding to Pediatric Distress
Since cardiac arrest in children is the culmination of a deteriorating state, recognizing the signs of impending respiratory failure or shock is the most effective defense. Early signs of respiratory distress include an increased rate of breathing, flaring of the nostrils, or retractions, where the skin pulls in between the ribs or at the neck during inhalation.
A child may also make audible sounds like grunting or wheezing, indicating a struggle for air.
Signs of poor circulation, or shock, can manifest as cool, pale, or mottled skin, especially on the extremities. The child may also appear lethargic, unresponsive, or irritable, indicating poor blood flow to the brain. The presence of marked bradycardia, a very slow heart rate, in a sick child is a sign that the system is failing.
The immediate priority for intervention is to address the underlying lack of oxygen and ventilation. For an unresponsive child who is not breathing or is only gasping, high-quality cardiopulmonary resuscitation (CPR) must be initiated immediately. Providing effective rescue breaths and chest compressions is the primary way to deliver oxygen and attempt to reverse the hypoxia-induced cascade.