Final answer:
A nurse should prioritize assessing the blood pressure and heart rate before administering ivabradine to a client with heart failure to ensure medication safety and effectiveness. Therefore, the correct option is b.
Step-by-step explanation:
When a nurse is preparing to administer ivabradine to a client with heart failure, the preadministration assessment that should be prioritized is B) Blood pressure and heart rate. Ivabradine works by reducing the heart rate, without affecting blood pressure significantly, and is used to treat certain types of chronic heart failure. It is crucial to assess the blood pressure and heart rate to ensure the safety and effectiveness of the medication, as well as to establish a baseline for future comparisons. Administering ivabradine to a patient with too low of a heart rate or blood pressure could potentially exacerbate their condition, hence, these vital signs are critical in guiding dosage and monitoring for adverse effects.