Phosphorus levels during infusion of parenteral nutrition with calorie-based phosphorus concentration: A case series

Abstract

Summary Background & aims Hypophosphatemia occurs frequently in patients on parenteral nutrition, mainly when malnutrition is present, and is related to phosphorus concentration in the solution. In spite of hypophosphatemia's potentially fatal outcome, there is no consensus on the adequate concentration of phosphorus in parenteral nutrition solutions. Increasing phosphorus concentration in the solution has not decreased the disorder, causing hyperphosphatemia instead. This study aims to evaluate blood phosphorus balance during infusion of a parenteral solution with a phosphorus concentration based on total energy. Methods Thirty-six non-critically ill patients (50% male, 36% undernourished, 51.4 ± 17.2 years) received total parenteral nutrition with phosphorus concentration varying from 9.6 to 10 mMol per 1000 kcal. Blood samples for serum phosphorus levels were collected in three periods up to the seventh day of nutritional treatment. Only moderate and severe hypophosphatemia with levels below 2.2 mg/dl were considered. Clinical data and laboratory values had normal distribution and were analyzed with Chi-square for proportions and by ANOVA for repetitive measures. Results The incidence of hypophosphatemia was 11.1% (95% CI 4.5–25%) initially, 5.9% (95% CI 1.7–18%) in the second period (3rd to 4th day) and 5.3% (95% CI 1.0–16%) in the third period (5th to 7th day) (p = N.S.). Median phosphorus levels were 3.35 mg/dl (95% CI 2.7–3.4 mg/dl), 3.2 mg/dl (95% CI 2.9–3.6 mg/dl) and 3.1 mg/dl (95% CI 2.9–3.7 mg/dl), in these three periods respectively, without a statistically significant difference (p = N.S.). No adverse events associated with phosphorus disturbances were observed throughout parenteral nutrition therapy. Conclusions Phosphorus concentration from 9.6 to 10 mMol/1000 kcal in parenteral nutrition resulted in lower than expected rates of hypophosphatemia in non-critically ill patients with no significant side effects related to this phosphorus concentration.