A 71-year-old man develops dysphagia for both solids and liquids and weight loss of 60 lb over the past 6 months. He undergoes endoscopy, demonstrating a distal esophageal lesion, and biopsies are consistent with squamous cell carcinoma. He is scheduled for neoadjuvant chemoradiation followed by an esophagectomy. Preoperatively he is staed on total parenteral nutrition, given his severe malnutrition reflected by an albumin of less than 1. Which of the following is most likely to be a concern initially in staing total parenteral nutrition in this patient?

Hypophosphatemia is a complication of refeeding syndrome, which occurs in malnourished patients who are administered with intravenous glucose. During periods of starvation, electrolytes are shifted to the extracellular space to maintain adequate serum concentrations. With refeeding, insulin levels rise and electrolytes are shifted back intracellularly, resulting in potential hypokalemia, hypomagnesemia, and hypophosphatemia. Additionally, refeeding results in an increased cellular need for phosphorus for energy production (ATP) and glucose metabolism. Early complications of TPN also include hyperglycemia, hyperchloremic acidosis, and volume overload with resultant hea failure. TPN, paicularly in the extremely malnourished patient, should be staed slowly; magnesium, potassium, and phosphate levels should be repleted; and dextrose infusions should be limited to prevent complications of refeeding.