A 60-year-old man with chronic alcoholism and a 20-pound wei…

A 60-year-old man with chronic alcoholism and a 20-pound weight loss over 2 months is admitted with pneumonia. He has had minimal oral intake for 10 days. Enteral nutrition is initiated at full caloric requirements. Within 48 hours, he develops confusion, muscle weakness, and arrhythmias. Labs: phosphate 1.1 mg/dL, potassium 2.8 mEq/L, magnesium 1.0 mg/dL.Which of the following best explains his clinical decline?