A linear regression model to predict the pH of neonatal parenteral nutrition solution

Introduction: Providing the high calcium intake necessary for normal bone m ineralization in rapidly growing very low birth weight infants is difficult because calcium and phosphorus solubility is limited in the range of paren teral nutrition pH. A major determinant of calcium and phosphorus solubilit y in vitro is solution pH. The objective of this study was to develop and a ssess the accuracy of a method to predict the final parenteral solution pH as a linear function of the individual parenteral component concentrations. Methods: pH values were measured for 205 neonatal parenteral nutrition solu tions prepared during a 5-week period. Concentrations of the 13 components used to synthesize parenteral nutrition were determined for each solution. Data from 135 samples were used to develop a linear regression coefficient model with pH as the dependent variable. From the regression model the pH w as predicted for the remaining 70 samples using the seven significant solut ion component concentrations, and the predicted and measured solution pH va lues were compared. Results: The mean measured parenteral nutrition pH for all solutions was 5. 364 +/- 0.110 (mean +/- SD, range 5.03-5.73). The absolute mean pH differen ce between the predicted and measured value for the 70 test samples was 0.0 4 +/- 0.04. pH estimated with the model correlated highly with measured pH (r(2) = 0.77). The seven components in the regression model accounted for 8 1% of the pH variance. Conclusion: The pH of neonatal parenteral nutrition solutions can be predic ted accurately as a linear function of the solution concentrations of the f ollowing seven components: sodium acetate, sodium phosphate, potassium phos phate, potassium acetate, magnesium sulphate, amino acid solution and dextr ose. The absolute mean difference between measured pH and predicted pH was 0.04. Applying this method to estimate pH with the interactive properties o f computer-based ordering systems could enhance calcium and phosphorus admi nistration to very low birth weight infants.