A nurse is caring for a client who develops third-degree heart block with a heart rate of 30/min. Which of the following actions should the nurse take?

A. Administer digoxin by IV bolus: Digoxin slows conduction through the AV node and can worsen a complete heart block. It is contraindicated in this condition and may lead to further bradycardia or cardiac arrest. B. Prepare the client for temporary pacing:Third-degree (complete) heart block results in electrical dissociation between atria and ventricles, leading to dangerously low heart rates and inadequate perfusion. The definitive treatment is temporary pacing to stabilize the cardiac rhythm until permanent pacing can be arranged. C. Instruct the client to perform the Valsalva maneuver: This maneuver is used to terminate supraventricular tachycardias by stimulating the vagus nerve. It is not indicated in bradyarrhythmias like third-degree heart block and could further lower the heart rate. D. Perform carotid sinus massage: This is another vagal maneuver used to treat tachycardias, not bradycardias. Performing it in a client with third-degree heart block could dangerously reduce the heart rate further and is therefore inappropriate.