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 B: Potassium. Furosemide is a loop diuretic that can cause potassium depletion as a side effect. Low potassium levels can lead to cardiac arrhythmias, which can worsen heart failure. Reviewing potassium levels before administering furosemide helps the nurse monitor the client's electrolyte balance and prevent potential complications.
Incorrect options:
A: Bicarbonate - Bicarbonate levels are not directly affected by furosemide administration.
C: Phosphate - Furosemide does not significantly impact phosphate levels.
D: Carbon dioxide - Carbon dioxide levels are not typically monitored in relation to furosemide therapy.