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A linear regression model to predict the pH of neonatal parenteral nutrition solution
P J Porcelli1, T M O'Shea, R G Dillard
1Department of Paediatrics, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. porcelli@wfubmc.edu
Introduction:
Providing the high calcium intake necessary for normal bone mineralization in rapidly growing very low birth weight infants is difficult because calcium and phosphorus solubility is limited in the range of parenteral nutrition pH. A major determinant of calcium and phosphorus solubility in vitro is solution pH. The objective of this study was to develop and assess 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 solutions 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 was predicted for the remaining 70 samples using the seven significant solution component concentrations, and the predicted and measured solution pH values 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 difference between the predicted and measured value for the 70 test samples was 0.04 +/- 0.04. pH estimated with the model correlated highly with measured pH (r2 = 0.77). The seven components in the regression model accounted for 81% of the pH variance.
Conclusion:
The pH of neonatal parenteral nutrition solutions can be predicted accurately as a linear function of the solution concentrations of the following seven components: sodium acetate, sodium phosphate, potassium phosphate, potassium acetate, magnesium sulphate, amino acid solution and dextrose. The absolute mean difference between measured pH and predicted pH was 0.04. Applying this method to estimate pH with the interactive properties of computer-based ordering systems could enhance calcium and phosphorus administration to very low birth weight infants.