With patients presenting in SVT, it is important to begin with the basic PALS algorithms and immediately differentiate stable versus unstable. If the patient is unstable, simply remember 2 joules per kilogram synced cardioversion, but if the patient is stable, recognize there are multiple treatment options available. As far as recognizing the unstable infant, look for evidence of heart failure, significant pallor, or decreased level of consciousness in addition to simply checking a blood pressure. If the patient requires cardioversion, PALS recommends 0.5-2.0 J/Kg delivered synchronously. Pediatric pads are preferred, but adult pads are an option if no pediatric pads are readily available.
It is important to keep in mind that wide complex tachycardia often has significantly different underlying pathology than narrow complex and should be treated as such. The cutoff for a wide complex tachycardia in pediatrics is a QRS > 0.09 seconds. 1
The preferred vagal maneuver in infants is the diving reflex. The infant should be placed in a sitting position, and a bag of ice should be placed on the infant’s face while simultaneously laying the infant back quickly. A second option is rectal stimulation using a thermometer. The concept behind both is to elicit a strong vagal response in a patient unable to voluntarily valsalva. One retrospective study found vagal maneuvers to be successful in 63% of SVT in Children.
If ice applied to the patient’s face does not work in the stable infant in SVT, have you had success with continued efforts at vagal maneuvers or do you move on to pharmacologic therapy?
If vagal maneuvers fail, adenosine is considered the drug of choice as it is a short acting but quite powerful AV nodal blocking agent that interrupts the reentrant conduction pathways causing the arrhythmia.  The recommended dosage in pediatrics is 0.1 mg/kg. If this is not successful, providers may reattempt with 0.2 mg/kg (max of 6mg and 12mg respectively). 1