The nurse is caring for a client in the telemetry unit and notices the rhythm below. The client is unresponsive and pulseless. After calling for assistance, what should be the nurse's next action?

A. The P-P and R-R distances are equal and regular: Equal and regular spacing between P-P and R-R intervals indicates that both atrial and ventricular rhythms are regular. This is a fundamental aspect of rhythm interpretation, helping to distinguish between regular and irregular rhythms such as atrial fibrillation or sinus arrhythmia.

B. The rhythm rate using a 3-second strip: Assessing the heart rate using a 3-second or 6-second ECG strip helps determine whether the rhythm is bradycardic, tachycardic, or within normal limits, which is crucial for accurate rhythm classification.

C. The duration of the U waves: U waves are typically small and follow the T wave. Although their presence can suggest conditions like hypokalemia, they are not routinely assessed in basic rhythm identification. Evaluating U wave duration is more relevant in electrolyte imbalance analysis than in identifying rhythm type.

D. There is a QRS complex after each P wave: A consistent QRS following every P wave indicates effective conduction from the atria to the ventricles. Each atrial depolarization (P wave) should be followed by a ventricular depolarization (QRS complex) if the signal is being conducted properly through the AV node. This finding supports a diagnosis of sinus rhythm and helps rule out AV blocks, where conduction may be delayed or blocked entirely.

E. P waves are present, upright and rounded: P waves that are upright and rounded in lead II suggest the electrical impulse is originating from the SA node. Their presence and morphology are essential criteria for identifying sinus rhythm and differentiating it from atrial arrhythmias like flutter or fibrillation.

A. Dopamine and 50% non-rebreather mask: Dopamine is a vasopressor used in hypotension or shock, an inotropic agent used to improve cardiac output, not typically first-line for anxiety or respiratory distress. A non-rebreather mask may provide high oxygen levels but can be overwhelming and exacerbate anxiety if not well tolerated.

B. Nesiritide IV infusion and digoxin PO: Nesiritide is a vasodilator which may reduce preload and afterload in heart failure, and digoxin is a positive inotrope that can improve contractility, but neither offers rapid relief for anxiety and dyspnea. These medications have slower onset and are not used primarily for symptom control in acute distress.

C. Diazepam IV push and metoprolol IV: While diazepam may reduce anxiety, it can depress respiration, which is dangerous in decompensated heart failure with potential pulmonary edema. Metoprolol reduces heart rate and contractility and must be used cautiously in acute settings.

D. Morphine IV and oxygen 2 liters via nasal cannula: Morphine reduces preload, anxiety, and the sensation of breathlessness, making it ideal in acute decompensated heart failure. Low-flow oxygen improves oxygenation without overwhelming the patient. This combination directly targets both physiologic and psychological distress.