A client admitted 2 days ago for chest pain develops a regular wide-complex tachycardia at 170/min on the monitor. The QRS complexes are uniform in shape. The client is alert, reports palpitations, and denies chest pain or shortness of breath. BP 118/74 mm Hg (baseline 124/78), SpO2 97% on room air, skin warm and dry, capillary refill 2 seconds. Admission QTc was 420 ms; K 4.2 mmol/L and Mg 2.0 mg/dL this morning. A saline lock is in the right hand. Which actions should the nurse anticipate? Select all that apply.

Quick answer
Anticipate a 12-lead ECG, adenosine 6 mg rapid push, and a large-bore antecubital IV (options 4, 3, 2).

Why this is correct
First decide stable versus unstable. BP 118/74 near baseline, alert, no chest pain or dyspnea, and warm skin mean no signs of instability, so there is time for a 12-lead ECG to define the rhythm. The AHA adult tachycardia algorithm allows adenosine for a stable wide-QRS tachycardia only when it is regular and monomorphic, which this rhythm is. Adenosine has a half-life of seconds, so it must go through a proximal large vein with a rapid flush; a hand saline lock is too distal.

Easy analogy or mental picture
Think of a fire alarm: if people are collapsing (unstable) you pull everyone out immediately (cardioversion); if everyone is calm (stable) you first check which room the smoke is coming from (12-lead) before choosing the extinguisher.

Memory hook
Unstable = shock it; stable + regular + monomorphic = look (12-lead) and try adenosine.

NCLEX decision rule
In any tachycardia, classify stability first; the same rhythm gets electricity when unstable and diagnostic evaluation plus drugs when stable.

Why the other choices are wrong
Synchronized cardioversion first (option 1) is correct only when the client shows hypotension, altered mental status, shock, ischemic chest pain, or acute heart failure, none of which is present. Verapamil (option 6) is tempting because it treats narrow-complex SVT, but in a wide-complex rhythm that may be ventricular it can cause severe hypotension. Magnesium (option 5) is tempting because it appears in tachycardia protocols, but it is for polymorphic VT (torsades) with a long QT; this rhythm is uniform, the QTc is 420 ms, and the Mg is normal.