Dysrhythmia management plays only a small role in the resuscitation of children. Because rhythm disturbances are usually secondary to hypoxia and not primary cardiac events, first provide ventilation and oxygenation, and correct hypoxia, acidosis, and fluid balance.
A child with an abnormal cardiac rhythm or rate, coupled with evidence of poor end-organ perfusion (cyanosis, mottled skin, lethargy, etc.) is unstable and requires immediate intervention. The parameters of clinical assessment and expression of instability vary with a child's age. In infants and children, variations in heart rate may be well tolerated clinically, and a blood pressure of 70 plus (age in years) divided by 2 mm Hg or less, coupled with evidence of poor end-organ perfusion, may be used to define instability. Figures 109-5, 107-6, and 109-7 summarize the approach to unstable cardiac rhythms in children, and Table 109-7 lists the weight-based electrical dose when cardioversion or defibrillation is indicated.8 American Heart Association guidelines for pediatric ALS are available at: http://circ.ahajournals.org/content/122/18_suppl_3.toc.
TABLE 109-7Energy Requirements for Defibrillation and Cardioversion ||Download (.pdf) TABLE 109-7 Energy Requirements for Defibrillation and Cardioversion
|Rhythm ||Type of Shock ||Initial Dose ||Subsequent Doses |
|Ventricular fibrillation or pulseless ventricular tachycardia ||Defibrillation (unsynchronized) ||2 J/kg ||4 J/kg to maximum of 10 J/kg or adult dose |
|Unstable supraventricular tachycardia or ventricular tachycardia with pulse but poor perfusion ||Synchronized cardioversion ||0.5–1 J/kg ||2 J/kg |
Pediatric pulseless arrest decision tree. PEA = pulseless electrical activity; VF = ventricular fibrillation; VT = ventricular tachycardia. [Reprinted with permission 2010 American Heart Association Guidelines For CPR and ECC Part 14: Pediatric Advanced Life Support Circulation. 2010;122[suppl 3]:S876-S908 © 2010, American Heart Association, Inc.]
Pediatric bradycardia decision tree. ABC = airway, breathing, circulation; AV = atrioventricular; HR = heart rate; ICP = intracranial pressure. [Reprinted with permission 2010 American Heart Association Guidelines For CPR and ECC Part 14: Pediatric Advanced Life Support Circulation. 2010;122[suppl 3]:S876-S908 ©2010, American Heart Association, Inc.]
Pediatric tachycardia decision tree for infants and children with rapid rhythm and poor perfusion. ABC = airway, breathing, circulation; bpm = beats per minute; HR = heart rate. [Reprinted with permission 2010 American Heart Association Guidelines For CPR and ECC Part 14: Pediatric Advanced Life Support Circulation.2010;122[suppl 3]:S876-S908 ©2010, American Heart Association, Inc.]
The most common rhythms seen in pediatric arrest are the bradycardias, which lead to asystole if untreated. Again, treatment consists of maximizing oxygenation and ventilation. Begin chest compression in children with a heart rate <60 beats/min and signs of poor perfusion.
Paroxysmal atrial tachycardia (supraventricular tachycardia) is seen most commonly in infants and most often presents as a narrow complex tachycardia with rates usually between 250 and 350 beats/min. Treatment of unstable patients consists of rapid synchronized cardioversion. Treatment of stable patients varies. Adenosine, vagal maneuvers, and cardioversion are used to treat stable supraventricular tachycardia. Adenosine (0.1 milligram/kg) is the current recommended drug for supraventricular tachycardia in children; administer via rapid IV push using a three-way-stopcock setup and normal saline flush in a proximal vein or intraosseous line. This dose can be doubled if the first dose is unsuccessful.
Differentiating a rapid secondary sinus tachycardia from a rapid primary cardiac tachycardia can be difficult but is critical to patient management. Although heart rates of 150 to 200 beats/min in adults are usually cardiac in origin, small infants and young children not uncommonly have compensatory sinus tachycardias as fast as 200 to 220 beats/min. A rate of >220 beats/min in an infant or >180 beats/min in a child is likely supraventricular tachycardia. ECG may not be very helpful, because identifiable P waves may not be readily apparent at very fast rates. History compatible with volume loss suggests sinus tachycardia. Congestive heart failure is more likely associated with a pathologic rhythm than a compensatory sinus tachycardia. Children can tolerate primary cardiac tachydysrhythmias for long periods before congestive heart failure or lethal dysrhythmias develop.
CARDIOVERSION, DEFIBRILLATION, AND PACING
Electric conversion is used on an emergency basis to treat ventricular fibrillation (defibrillation) and symptomatic tachydysrhythmia (cardioversion). Ventricular fibrillation is an unusual presenting rhythm in infants and children, but more common with advancing age, and may be present at some point in up to 27% of children with in-hospital cardiac arrest.7,8,33 Energy requirements for defibrillation and cardioversion are listed in Table 109-7.
Paddle size is 4.5 cm for infants (who weigh <10 kg) and 8 cm for children. The paddle should be in contact with the chest wall over its entire surface area. The larger, 8-cm paddles can be used for infants in the anteroposterior position.
Electrode cream, electrode paste, and saline-soaked gauze pads are acceptable. Alcohol pads should not be used because serious burns may occur. Make sure that the interface substance from one paddle does not come in contact with the substance from the other paddle. Contact creates a short circuit, and insufficient energy may be delivered to the heart. Many defibrillation devices use cables with integrated adhesive pads for delivery of energy. Adhesive pads are used with the same general guidelines as metal paddles, including the recommendations on sizing and positioning.
Place one paddle to the right of the sternum at the second intercostal space. Place the other paddle at the left midclavicular line at the level of the xiphoid. The anteroposterior approach also can be used, although improved success with anteroposterior positioning has not been documented.8
Defibrillate as quickly as possible for pulseless ventricular tachycardia or ventricular fibrillation. The first shock success rate during cardiac arrest due to ventricular arrhythmia is 18% to 50%.8 Initially, use 2 J/kg. Immediately after defibrillation, and before additional attempts at defibrillation, provide 2 minutes of high-quality uninterrupted CPR to restore coronary perfusion and improve delivery of oxygen to the myocardium. If the first defibrillation attempt is unsuccessful, double the defibrillation energy to 4 J/kg, and use this higher energy level for all additional defibrillation attempts; refractory ventricular fibrillation may require higher energy to a maximum of 10 J/kg or the maximum adult dose.8
Provide 2 minutes of chest compressions with ventilations after each defibrillation attempt, regardless of the postdefibrillation rhythm. Nearly all patients will be in a low-perfusion state after defibrillation, and external chest compressions (with ventilations) will improve the perfusion of the vital organs.
If medications such as epinephrine are administered, they are probably most effective when given 1 to 2 minutes before repeating a defibrillation attempt.
Tachydysrhythmias are generally very sensitive to electric conversion. The initial dose is 0.5 J/kg, in the synchronized mode (Table 109-7). Double the energy level if the first attempt is unsuccessful. If the device has only a few energy settings available, choose the one closest to the desired energy setting. If the device does not provide the synchronized mode, then obviously the unsynchronized mode must be used.
Severe bradycardia or asystole due to an intrinsic myocardial block may respond to transcutaneous pacing. Oxygenation, chest compressions, and medications should precede attempts at pacing in children with severe symptomatic bradycardia due to heart block or sinus node dysfunction. Pacing is not indicated if the bradycardia is due to hypoxic or ischemic myocardial injury or if due to respiratory failure.
Use adult pacing patches in children who weigh >15 kg.34 Anterior-posterior positioning does not appear to have an advantage over the standard anterior positioning. If using the anterior-posterior positioning, place the negative electrode patch on the anterior chest at V3, and place the positive electrode patch on the posterior chest between the shoulder blades at the T4 vertebral level. Ventricular capture is determined by the palpation of a pulse or the appearance of an arterial waveform, if an arterial pressure catheter is present. Maximal energy output is used until ventricular capture occurs, then the energy setting is decreased progressively until the lowest setting is found that allows ventricular capture. Set the pacing rate slightly higher than the normal rate for age.
Transcutaneous pacing has not been associated with greatly improved survival rates, but may be advantageous in a child with sudden asystole or bradycardia due to intrinsic atrioventricular node or sinus node dysfunction and with congenital or acquired heart disease.
Automated External Defibrillators
Because children ≥8 years old may have life-threatening arrhythmias similar to those in adults and because their body weights approach those of adults, an automated external defibrillator (AED) can be used. A child ≥8 years and weighing >25 kg with sudden collapse should have an AED applied as soon as possible. An AED with a pediatric dose attenuator is ideal for a child 1 to 8 years of age because this feature allows the delivery of a lower dose of energy in pediatric patients. More AEDs are available that allow changing the cardioversion energy levels. If an AED with a pediatric dose attenuator is not available, then use a standard AED. AEDs may be used in infants, but a manual defibrillator is preferred.
Because ventricular fibrillation is an uncommon presentation in children, it is uncertain whether there is greater benefit from providing five cycles of CPR before application of the AED or withholding CPR until the AED has completed its analysis of the heart rhythm. Guidelines for adults recommend 2 minutes of chest compressions before allowing the AED to analyze the rhythm in unwitnessed arrests or when the time since collapse is >5 minutes.10 For witnessed arrests and arrests in the hospital, the AED should be applied and allowed to analyze as soon as possible. Start chest compressions the instant cardiac arrest is confirmed, and continue compressions until the moment the AED is in place and ready to analyze the rhythm. Realistically, with more than one rescuer, a cycle or two of chest compressions can be provided before the AED is able to analyze the rhythm. If the AED does not recommend defibrillation, then continue CPR. Keep the AED applied until other means of cardiac monitoring become available.