A nurse is caring for a client who has heart failure and a new prescription for furosemide. Which of the following laboratory values should the nurse review before administering furosemide?

The correct answer is A: Potassium. When administering furosemide, a loop diuretic, the nurse should review potassium levels as furosemide can cause potassium depletion. Hypokalemia can lead to cardiac dysrhythmias, which can be dangerous for a client with heart failure. Reviewing potassium levels before administering furosemide allows the nurse to identify any potential imbalances and take appropriate actions such as adjusting the medication dosage or providing potassium supplements if necessary. The other choices (B: Phosphate, C: Carbon dioxide, D: Bicarbonate) are not directly affected by furosemide administration and are not typically monitored specifically for this medication.