Final answer:
When a client's ECG changes from normal sinus rhythm to supraventricular tachycardia, the nurse should prepare to assist with vagal stimulation. This intervention is aimed at increasing parasympathetic tone to slow AV node conduction, which can potentially terminate SVT.
Step-by-step explanation:
When a nurse is monitoring a client's ECG monitor and notes a change from normal sinus rhythm to supraventricular tachycardia (SVT), the nurse should prepare to assist with specific interventions to restore a normal heart rhythm. Among the options provided, the most appropriate initial intervention for SVT is vagal stimulation. Vagal maneuvers can be performed to increase parasympathetic tone and potentially terminate the SVT by slowing electrical conduction through the atrioventricular (AV) node. These maneuvers include the Valsalva maneuver, carotid sinus massage, or immersing the face in cold water. If vagal maneuvers are not effective, intravenous adenosine may be administered in a clinical setting, as it can also help terminate SVT by briefly blocking AV node conduction. It is important to note that options such as defibrillation and delivery of a precordial thump are generally reserved for more severe arrhythmias like ventricular fibrillation or pulseless ventricular tachycardia, and not for stable SVT.