Phosphorus depletion in children on long-term total parenteral nutrition

The retention of nitrogen, calcium and phosphorus was studied in nine infants on total parenteral nutrition. The amounts of calcium, nitrogen and phosphorus were varied singly or simultaneously. The results demonstrate close interrelationships in the retention of these three elements. Not only the absolute amount of phosphorus perfused daily but also the amounts of nitrogen and/or calcium perfused simultaneously account for the phosphorus depletion that may lead to severe hypophosphatemia. The decrease in serum phosphorus concentration with a simultaneous fall of urinary phosphorus excretion to undetectable levels and a rise in urinary calcium output to 10 mg/kg/24 hours or more are warning symptoms of phosphorus depletion. Such a complication was observed in our first seven children on total parenteral nutrition. Phosphorus depletion can be prevented by using the following amounts of these elements in the perfusate: per 100 Kcal/kg/24 hours, 400 mg/kg/24 hours of nitrogen, 35 mg/kg/24 hours of calcium and 40 mg/kg/24 hours of phosphorus. With such a technique no phosphorus depletion was observed in any of the 63 subsequent patients whom we treated with total parenteral nutrition for periods varying from 20 days to 9 months.