A client with heart failure is prescribed digoxin 0.125 mg daily. Before administration, which assessment is the PRIORITY?

DIGOXIN (a cardiac glycoside) has a narrow therapeutic index and specific assessment requirements before administration. PRIORITY ASSESSMENT: APICAL PULSE — measure for a full 60 seconds; HOLD and notify provider if: below 60 bpm in adults; below 70 bpm in children; below 90 bpm in infants; POTASSIUM (K+) — hypokalemia sensitises the myocardium to digoxin toxicity; even therapeutic digoxin levels can cause toxicity when potassium is low; target K+ 3.5-5.0 mEq/L; DIGOXIN LEVEL — therapeutic range 0.5-2.0 ng/mL (though lower end preferred for heart failure); DIGOXIN TOXICITY SIGNS — early: nausea, vomiting, anorexia, visual disturbances (yellow-green halos around lights, blurred vision); cardiac: bradycardia, heart block, any new dysrhythmia; MANAGEMENT OF TOXICITY: hold digoxin; check serum level and electrolytes; provide potassium supplementation if hypokalemic; severe toxicity: Digoxin Immune Fab (DigiFab/Digibind) — specific antidote; MEDICATIONS THAT INCREASE DIGOXIN TOXICITY: hypokalemia-causing agents (loop diuretics, thiazides); antiarrhythmics (amiodarone, quinidine increase digoxin levels); verapamil. NURSING RULE: Count the pulse, check the potassium, then give digoxin.