Rhythm Disturbances and Electrical Therapy
Treat the child, not the tracing. Bradycardia with a pulse and poor perfusion is usually hypoxic: ventilate with oxygen first, and if the rate remains below 60 per minute with poor perfusion despite effective ventilation, begin CPR. Epinephrine is the drug of choice; atropine is reserved for vagal-mediated or primary AV block bradycardia.
For tachycardia with a pulse, decide whether the QRS is narrow or wide and whether the child is stable. Sinus tachycardia has an explanation (fever, pain, dehydration, sepsis), visible P waves, and variable R-R intervals, and rarely exceeds 220 in infants or 180 in children. SVT is abrupt in onset, has absent or abnormal P waves, a fixed R-R interval, and usually exceeds those rates.
Unstable SVT - hypotension, altered mental status, ischemic pain, shock - gets synchronized cardioversion at 0.5–1 J/kg, escalating to 2 J/kg. Stable SVT gets vagal maneuvers (ice bag over the face in an infant), then adenosine 0.1 mg/kg (max 6 mg) as a rapid push, with a second dose of 0.2 mg/kg (max 12 mg). Wide-complex tachycardia is presumed ventricular.
Pulseless VF and pulseless VT are defibrillated with unsynchronized shocks: 2 J/kg, then 4 J/kg, then 4 J/kg or higher up to 10 J/kg or the adult dose. Give epinephrine and an antiarrhythmic between shocks and resume compressions immediately.
Traps: shocking asystole, applying a synchronized shock to VF, or giving adenosine to an unstable child who needs electricity. Never delay cardioversion to obtain IV access.
Worked example: a 6-month-old with a narrow-complex rate of 280 who is cold and lethargic receives synchronized cardioversion at 0.5–1 J/kg.