3.1 Pediatric Dysrhythmias & ECG Analysis
Key Takeaways
- Pediatric dysrhythmias are overwhelmingly secondary to hypoxia, severe acidosis, or structural heart disease, requiring immediate oxygenation and ventilation as primary PALS resuscitation steps.
- Sinus Tachycardia (infant HR <220, child HR <180) exhibits rate variability and present P waves, whereas Supraventricular Tachycardia (infant HR ≥220, child HR ≥180) features abrupt onset, fixed rate, and hidden P waves.
- Pediatric bradycardia with HR <60 beats/min and signs of poor perfusion despite effective oxygenation/ventilation requires immediate chest compressions and Epinephrine (0.01 mg/kg IV/IO).
- Adenosine (initial dose 0.1 mg/kg, max 6 mg) is the first-line chemical cardioversion for stable SVT and MUST be administered via rapid two-syringe push technique followed immediately by a 5–10 mL saline flush.
- Unstable dysrhythmias with pulse (SVT, VT) require synchronized cardioversion starting at 0.5 to 1 J/kg, while shockable pulseless arrest rhythms (pVT/VF) require immediate unsynchronized defibrillation at 2 J/kg.
Pediatric Dysrhythmias & ECG Analysis
Pediatric cardiac dysrhythmias present unique clinical challenges in the emergency department because children rarely present with primary cardiac pathology. In pediatric patients, dysrhythmias are most frequently secondary to hypoxia, acidosis, electrolyte derangements, toxicological ingestions, or congenital heart abnormalities. Pediatric emergency nurses must rapidly recognize abnormal cardiac rhythms, distinguish malignant dysrhythmias from physiological compensatory mechanisms, and execute Pediatric Advanced Life Support (PALS) protocols without delay.
Normal Pediatric ECG Differences & Conduction Physiology
Interpreting a pediatric 12-lead electrocardiogram (ECG) requires a clear understanding of age-specific developmental differences. Infants are born with right ventricular dominance due to high fetal pulmonary vascular resistance. As the child grows, left ventricular mass increases, shifting the electrical axis.
Key Age-Dependent ECG Features
- Heart Rate: Baseline heart rates are significantly faster in neonates (100–160 bpm) and infants, gradually decreasing toward adult ranges by adolescence.
- QRS Axis: Right-axis deviation (+90° to +180°) is normal in newborns. Left-axis deviation in a neonate suggests congenital structural defects such as tricuspid atresia or an atrioventricular canal defect.
- Interval Duration: PR intervals, QRS duration, and QTc intervals are shorter in infants and young children due to smaller cardiac mass and faster conduction velocities (normal infant QRS is <0.08 seconds; child <0.09 seconds).
- T-Wave Progression: T waves in leads V1 through V3 are inverted in healthy children from age 1 week up to early adolescence (termed the juvenile T-wave pattern). An upright T wave in V1 after 7 days of life indicates right ventricular hypertrophy.
Sinus Tachycardia vs. Supraventricular Tachycardia (SVT)
Differentiating Sinus Tachycardia (ST) from Supraventricular Tachycardia (SVT) is one of the most critical diagnostic challenges in pediatric emergency nursing. Misdiagnosing SVT as ST delays essential cardioversion, while misdiagnosing ST as SVT risks administering AV-nodal blocking agents to a patient experiencing compensatory shock.
| Diagnostic Parameter | Sinus Tachycardia (ST) | Supraventricular Tachycardia (SVT) |
|---|---|---|
| Infant Heart Rate | Typically <220 beats/min | Typically ≥220 beats/min |
| Child Heart Rate | Typically <180 beats/min | Typically ≥180 beats/min |
| Onset & Offset | Gradual acceleration and deceleration | Abrupt, sudden onset ("on/off switch") |
| Rate Variability | Varies continuously with activity, fever, or pain | Fixed, monomorphic rate; no beat-to-beat variability |
| P-Wave Morphology | Normal P waves present before every QRS complex | Absent, hidden in T wave, or retrograde/inverted P waves |
| Underlying History | Fever, dehydration, hypovolemia, sepsis, pain, anxiety | History of irritability, poor feeding, tachypnea, or sudden pallor |
| Response to Therapy | Rate slows as underlying cause is treated (e.g., fluid bolus) | Unaffected by antipyretics or fluid resuscitation |
Pediatric Bradycardia Management
In pediatric patients, bradycardia is an ominous sign of impending cardiac arrest. Unlike adults, where bradycardia is frequently primary cardiac in origin (e.g., ischemia), pediatric bradycardia is almost exclusively caused by profound tissue hypoxia, severe hypovolemia, or hypercapnia.
Clinical Threshold & PALS Algorithm
- Initial Assessment: Assess airway, breathing, and circulation. Administer 100% supplemental oxygen and provide effective bag-valve-mask (BVM) ventilation if respiratory effort is inadequate.
- Indications for CPR: If the heart rate remains <60 beats/min with signs of poor systemic perfusion (altered mental status, weak central pulses, delayed capillary refill >3 seconds, hypotension) despite adequate oxygenation and ventilation, immediately initiate chest compressions.
- Pharmacological Interventions:
- Epinephrine: First-line medication for symptomatic bradycardia refractory to ventilation. Dosage: 0.01 mg/kg IV/IO (0.1 mL/kg of 0.1 mg/mL concentration). Repeat every 3 to 5 minutes.
- Atropine: Indicated instead of epinephrine if bradycardia is caused by increased vagal tone (e.g., post-endotracheal intubation suctioning), primary AV block, or organophosphate poisoning. Dosage: 0.02 mg/kg IV/IO (minimum single dose 0.1 mg to avoid paradoxical bradycardia; maximum single dose 0.5 mg in children, 1.0 mg in adolescents).
Pediatric Cardiac Arrest Rhythms
Pediatric cardiac arrest is classified into non-shockable and shockable rhythms. Non-shockable rhythms account for over 80–90% of out-of-hospital pediatric cardiac arrests.
Non-Shockable Rhythms: Asystole & Pulseless Electrical Activity (PEA)
- Pathophysiology: Result from progressive respiratory failure, hypoxic-ischemic collapse, or uncompensated shock.
- Management: High-quality CPR (15:2 compression-to-ventilation ratio for two rescuers), continuous chest compressions once an advanced airway is placed (1 ventilation every 2–3 seconds), and Epinephrine 0.01 mg/kg IV/IO administered as early as possible (within 5 minutes of arrest onset). Search for and treat reversible causes (H's and T's).
Shockable Rhythms: Pulseless Ventricular Tachycardia (pVT) & Ventricular Fibrillation (VF)
- Pathophysiology: Primary cardiac events, electrolyte abnormalities (hyperkalemia), drug toxicities (tricyclic antidepressants, digoxin), or commotio cordis.
- Defibrillation Energy Dosing:
- First Shock: 2 J/kg (unsynchronized).
- Second Shock: 4 J/kg.
- Subsequent Shocks: ≥4 J/kg (up to a maximum of 10 J/kg or adult standard dose of 200 J).
- Medication Timing: Resume CPR immediately after each shock for 2 minutes before re-evaluating rhythm. Administer Epinephrine 0.01 mg/kg IV/IO after the second shock. Administer Amiodarone 5 mg/kg IV/IO bolus (or Lidocaine 1 mg/kg IV/IO) after the third shock for refractory pVT/VF.
Adenosine Administration & Synchronized Cardioversion Rules
Adenosine Dosing & Administration Technique
Adenosine is the primary pharmacological treatment for stable SVT when vagal maneuvers (e.g., applying an ice bag to the upper face without occluding the nose/mouth for 15–20 seconds) fail.
- First Dose: 0.1 mg/kg IV/IO rapid push (maximum initial dose 6 mg).
- Second Dose: 0.2 mg/kg IV/IO rapid push (maximum second dose 12 mg).
- Critical Administration Rule: Adenosine has an extremely short half-life (<10 seconds). It must be administered using a two-syringe rapid flush technique via a 3-way stopcock inserted as close to the patient's heart as possible (antecubital or central line). Syringe 1 contains adenosine; Syringe 2 contains a 5 to 10 mL normal saline flush. Push adenosine as a rapid IV bolus, instantly turn the stopcock, and slam the saline flush immediately behind it. Continuous 12-lead ECG monitoring must record the conversion.
Synchronized Cardioversion for Unstable Dysrhythmias
If a child with SVT or Ventricular Tachycardia with a pulse exhibits signs of instability (hypotension, poor perfusion, lethargy):
- Initial Energy: 0.5 to 1 J/kg (synchronized to the R wave).
- Subsequent Energy: Increase to 2 J/kg if the initial attempt is unsuccessful.
- Clinical Caution: Ensure the "SYNC" mode is selected on the defibrillator to prevent delivering a shock during the vulnerable T-wave period, which could precipitate VF. Sedate if time permits, but never delay cardioversion in an unstable patient.
An 8-month-old infant is brought to the emergency department for extreme irritability and poor feeding. The monitor reveals a narrow-complex tachycardia at a rate of 230 beats/min with no beat-to-beat variability and unidentifiable P waves. The infant's blood pressure is normal, and capillary refill is 2 seconds. Which intervention should the nurse anticipate first?
A 4-year-old child presents to the resuscitation bay with severe respiratory distress, lethargy, and a heart rate of 48 beats/min. Despite opening the airway, providing 100% oxygen, and delivering effective bag-valve-mask ventilations for 1 minute, the heart rate remains 50 beats/min with central cyanosis and weak pulses. What is the immediate priority nursing action?
A 6-year-old child weighing 20 kg with SVT becomes altered, cold, and hypotensive. The physician orders synchronized cardioversion. What energy setting should the emergency nurse select for the initial shock?