In children, cardiac arrest which can be treated by a cardio doctor is usually secondary, and the most common cause is hypoxemia, which leads to hypoxia and tissue acidosis, followed by asystole. 1 Sudden circulatory collapse due to primary cardiac arrest resulting from ventricular fibrillation is the leading cause of cardiac arrest in adults. However, it occurs in approximately 5 to 15% of all prehospital cardiac arrests in children. Fibrillation and pulseless ventricular tachycardia are more frequent with increasing age. In the hospital setting, fibrillation can occur in about 10% of cases as the initial cardiac arrest rhythm in children. During the cardiopulmonary resuscitation procedure, it can occur in about 25% of cases.
Survival from cardiopulmonary arrest is generally low and varies depending on where it occurs and the type of rhythm at the time of the arrest. Survival is, of course, higher if the event took place in a hospital environment, ranging from 2 to 10% of cases. The same goes for the incidence of neurological sequelae. In addition, compared to asystole, the chances of survival are also higher when the initial present rhythm is ventricular fibrillation or pulseless ventricular tachycardia. In these cases, the chances of survival have an average of 33% of cases, while in asystole, the average is 7 to 11% of cases. However, if fibrillation develops during the resuscitation procedure, after an initial rhythm of asystole, the prognosis is worse.
We can understand this fact if we consider that arrhythmia can start acutely in a healthy heart, still well-oxygenated and with reasonable metabolic reserves. In contrast, asystole usually occurs when the coronary perfusion’s compensatory mechanisms are exhausted, leaving the myocardium in great suffering from hypoxia and acidosis. 1 This cardiopulmonary arrest, called hypoxic, is the most common mechanism of cardiac arrest in infants and children up to adolescence and refers to the terminal event triggered by respiratory failure or shock. The common terminal pathway leading to hypoxic cardiac arrest is a cardiopulmonary failure, regardless of the initial event.
In children, arrhythmias that cause cardiac arrest are often associated with underlying conditions, such as acute infectious heart disease (myocarditis), hypertrophic or anomalous coronary cardiomyopathies, long QT syndrome, drug intoxication, electrolytes, or electrolytes, or chest trauma (cardiac concussion). Therefore, the causes of cardiac arrest vary according to the patient’s age, the underlying diseases they may have, and the triggering event.
In infants younger than 6 months, rebreathing syndrome or sudden infant death syndrome is the leading cause of death. From 6 months onwards, the main reason is trauma, 1 which leads to cardiopulmonary failure, mainly due to impaired breathing, tension pneumothorax, circulatory failure resulting from acute and severe hemorrhages or head trauma. In addition, in trauma, even in the face of these last two conditions, the event that usually leads to rapid cardiopulmonary deterioration is the compromise of the airways and, consequently, breathing. Therefore, immediate airway support should be prioritized, regardless of the type and extent of traumatic injuries.
Respiratory failure occurs due to upper airway obstruction (choking, acute infections); lower airway obstruction (asthma, bronchiolitis); lung parenchymal diseases (ARDS, pneumonia, intoxications); or central uncontrolled breathing (head trauma, seizures, drowning). The shock can be: compensated (with normotension), decompensated (with hypotension), hypovolemic (severe bleeding, dehydration), cardiogenic (primary heart diseases, acute infarctions, arrhythmias, intoxications); distributive (septic, neurogenic); or obstructive (cardiac tamponade, pneumothorax). Cardiopulmonary failure is often avoided in a hospital environment with the appropriate approach and continuous monitoring of the conditions described above. Cardiopulmonary failure is a state in which the physiological mechanisms of compensation have already been exhausted. Consequently, respiratory failure and decompensated shock coexist. Ventilation, oxygenation, and tissue perfusion are severely compromised. The patient has generalized cyanosis, breathing is irregular or agonizing, and the heart rate declines rapidly. At this point, cardiac arrest is imminent.
Cardiac arrest can be recognized by the clinical signs of apnea, absence of a detectable central pulse, and unconsciousness. Studies show that even healthcare professionals often have difficulty determining the presence or absence of pulses. Due to this fact and considering the severity of the condition, as well as the need for immediate action, it is recommended that, in case of doubt or difficulty in palpating the pulses, the cardiac arrest should be considered the condition in which there is no response to stimulation, and there is apnea or agonizing breathing.
The clinical condition of apnea, absence of pulse, and lack of response to stimulation is defined as circulatory collapse rhythm. In this condition, there are four possibilities for the patient’s heart rhythms: (i) asystole, when the heart is stopped and has no electrical activity; (ii) ventricular fibrillation, when the heart has disorganized electrical activity and does not pump blood; (iii) pulseless ventricular tachycardia, when the rhythm is an advanced stage ventricular tachycardia and the heart can no longer pump blood to generate the pulse wave; or (iv) pulseless electrical activity (PEA). Asystole and PEA are the most common rhythms in cardiac arrests in children, both in out-of-hospital and in-hospital environments. Asystole may be preceded by bradycardia or pulseless electrical activity, usually an abnormal rhythm with wide QRS. In cases of sudden collapses witnessed, we must consider the high probability of ventricular fibrillation. This is of great importance because it determines the priorities for action.