A 6-year-old girl with a heart rate of 170 beats/min shows signs of lethargy and tachycardia. What is the most appropriate intervention?

In this scenario, the most appropriate intervention is to administer a 20-mL/kg normal saline bolus. This choice is grounded in the understanding of pediatric patients, particularly in the presence of tachycardia and lethargy, which may indicate dehydration or inadequate perfusion.

In children, a rapid heart rate can be a compensatory response to low blood volume or shock. Administering a normal saline bolus can help to quickly restore intravascular volume, improve circulation, and subsequently reduce the heart rate toward a normal range. This fluid resuscitation is critical, especially if the child is showing signs of lethargy, which can indicate significant distress or impaired perfusion.

Transporting the patient immediately while establishing vascular access, while important, does not address the immediate need for volume resuscitation. Starting an IV line and administering adenosine is not indicated at this stage; adenosine is typically used for specific arrhythmias and may not be appropriate without clear identification of a particular tachyarrhythmia. Applying chemical ice packs to the face might be an effective technique for specific types of supraventricular tachycardia in adults but is not a frontline treatment in a pediatric patient presenting with lethargy and