Which of the following is NOT an approved vagal maneuver?

• A. Valsalva maneuver
• B. Head-down tilt with deep inspiration
• C. Activation of the diving reflex by facial immersion in ice water (unless ischemic heart disease is present)
• D. Administration of adenosine

Answer: (D)

Vagal maneuvers work by increasing parasympathetic (vagal) tone to slow conduction through the AV node and help terminate certain supraventricular tachycardias. The Valsalva maneuver accomplishes this by raising intrathoracic pressure and triggering a reflex increase in vagal activity, which slows AV conduction. Head-down tilt with deep inspiration also augments vagal tone and can provoke bradycardia through similar reflex pathways. The diving reflex, induced by cold facial immersion, promotes vagal output to the heart via a trigeminal-triggered reflex, producing bradycardia.

Administration of adenosine, however, is a pharmacologic action that directly blocks AV nodal conduction through receptor pathways, causing a brief pause in AV conduction to terminate SVT. It does not rely on increasing vagal tone, so it is not an approved vagal maneuver.