An older adult client is taking digitalis (Digoxin) 0.25 mg…
An older adult client is taking digitalis (Digoxin) 0.25 mg twice a day and furosemide( Lasix) 40 mg daily for heart failure (HF). She has complained of increasing lethargy and nausea over the past 2 days; however she is still able to take her medication. Her blood pressure is 150/98 mm Hg; pulse is 110 beats/min and irregular; respiratory rate is 18 breaths/min. What laboratory information is most important for the nurse to evaluate?