Which intervention was performed first before administering medication to the patient?

In the context of managing certain arrhythmias, especially in cases of paroxysmal supraventricular tachycardia (PSVT), vagal maneuvers are often the first intervention performed before administering medication. These maneuvers can include actions such as carotid sinus massage or the Valsalva maneuver, which aim to stimulate the vagus nerve to help slow down the heart rate and potentially restore normal rhythm.

The effectiveness of vagal maneuvers comes from the way they increase parasympathetic activity, leading to a transient effect on the heart's conduction system. If successful, these maneuvers can terminate the tachycardia without the need for pharmacological intervention or more invasive procedures. If vagal maneuvers do not resolve the arrhythmia, then medications or other interventions can be considered.

In contrast, other interventions listed may be used in different scenarios or as subsequent steps if vagal maneuvers are ineffective. For instance, synchronized cardioversion is usually indicated for more unstable tachyarrhythmias where immediate restoration of normal rhythm is required, while defibrillation is reserved for life-threatening rhythms like ventricular fibrillation. Atrial pacing may also be utilized in specific situations, such as poor response