A nurse is reviewing the laboratory results for a client who is receiving digoxin and notes a decreased potassium level. The nurse should monitor the client for which of the following adverse effects?

Digoxin is a cardiac glycoside used to improve myocardial contractility and control ventricular rate in certain arrhythmias such as atrial fibrillation. Its therapeutic window is narrow, meaning small changes in serum levels or electrolytes can lead to toxicity. Potassium plays a critical role in digoxin binding to myocardial cells, and low potassium levels increase the risk of toxicity. Therefore, electrolyte imbalances must be closely monitored to prevent life-threatening cardiac complications. Rationale: A. Dysrhythmias are a major and potentially life-threatening adverse effect when potassium levels are decreased in a client receiving digoxin. Hypokalemia enhances digoxin binding to myocardial sodium-potassium ATPase pumps, increasing its toxic effects on cardiac conduction. This can lead to arrhythmias such as atrial tachycardia with block, ventricular tachycardia, or fibrillation. B. Urinary retention is not associated with digoxin toxicity or hypokalemia. Digoxin primarily affects cardiac conduction and contractility rather than bladder function. Therefore, this is not an expected adverse effect in this clinical situation. C. Respiratory depression is not a characteristic effect of digoxin toxicity. This finding is more commonly associated with central nervous system depressants such as opioids or sedatives. Digoxin toxicity primarily affects the cardiovascular and gastrointestinal systems rather than respiratory drive. D. Tachycardia is not the most expected finding in digoxin toxicity related to hypokalemia; instead, various dysrhythmias are more typical. Although some arrhythmias may present with increased heart rate, digoxin toxicity often produces irregular rhythms or bradyarrhythmias as well. Therefore, dysrhythmia remains the most accurate and clinically significant concern.