Final answer:
The initial recommended dose of adenosine for SVT unresponsive to vagal maneuvers is 6 mg IV bolus, followed by a second 12 mg dose if needed.
Step-by-step explanation:
The recommended initial dose of adenosine for the management of supraventricular tachycardia (SVT) unresponsive to vagal maneuvers is 6 mg. This should be administered rapidly as an intravenous (IV) bolus. If the first dose does not result in termination of the SVT, a second dose of 12 mg can be administered 1 to 2 minutes after the first dose. It is important to follow up with continuous ECG monitoring during the administration due to the potential for transient side effects such as chest pain or arrhythmias.