A nurse is caring for a client who is postoperative and has an NG tube that has drained 2,500 mL in the past 6 hr. The nurse should monitor the client for which of the following electrolyte imbalances?

A. Decreased calcium level: Significant NG drainage is not a direct, primary cause of hypocalcemia; calcium changes are less directly related than potassium. B. Elevated sodium level: Large-volume gastric losses more commonly cause sodium depletion (or variable sodium changes) rather than an acute isolated sodium elevation. C. Elevated magnesium level: NG suctioning does not typically cause hypermagnesemia; losses may actually lower magnesium. D. Decreased potassium level: Gastric fluid contains potassium; high-volume nasogastric drainage predisposes the client to hypokalemia - monitor serum potassium and cardiac rhythm.