A 67-year-old, 60-kg homeless man has been in the intensive care unit (ICU) for a week after an emergency laparotomy and sigmoid resection for perforated diverticulitis. His serum albumin is 1.1 g/dL. He was just weaned from mechanical ventilation. His colostomy is not functioning. You start total parenteral nutrition (TPN) to deliver 1800 kcal/24 h. Two days later, the patient is in respiratory distress and requires reintubation and mechanical ventilation. You should check the level of serum

Rapid institution of full nutritional support can cause "refeeding syndrome" in malnourished patients. The hall mark of this condition is hypophosphatemia. Phosphate is taken up by phosphate-depleted cells trying to metabolize the nutrition and levels of ATP fall precipitously. This leads to respiratory failure. Refeeding syndrome can be avoided by starting nutritional support at low levels and increasing slowly. The other substances listed are not associated with respiratory failure after starting nutritional support.