[Weight monitoring in parenteral nutrition]

To assess the usefulness of weight monitoring as a routine quality assurance method in the preparation of parenteral nutrient units (PUNs).

In accordance with their frequency of use, two parenteral nutrition formulations were chosen, one prepared externally (NP-I) and the other internally (NPH-2500). The relative difference between the experimental weight and the theoretical weight was used as the response variable. This difference, expressed as a percentage, defines the preparation gravimetric error (EGP in its Spanish acronym) Weight monitoring was effected on 615 PUNs, of which 337 (55%) corresponded to the NPH-2500 formulation and 278 (45%) to the NP-I formulation. The quality of the preparation of the PUNs was established by means of the calculation of the exactness (mean EGP) and precision (square root of the mean of the squares of the EGP values), and the alert and invalidation limits for these parameters were defined. The usefulness of weight monitoring was established by the time needed to detect a preparation gravimetric error of more than 5%.

The overall prevalence of EGP in excess of 5% was less than 0.6% (95% CI: 0.0 to 0.6%). The overall exactness was 1.01% (95% CI: 0.96 to 1.05%). The difference between the exactness of NPH-2500, 0.66% (95% CI: 0.62 to 0.70%), and NP-I, 1.42% (95% CI: 1.36 to 1.49%), was statistically significant. The percentage of PUNs located outside the limits of invalidation for precision was significantly higher in the NPH-2500 formulation, 2.67% (95% CI: 2.36 to 3.00%), than in the NP-I formulation, 0.36% (95% CI: 0.25 to 0.49%). No statistically significant differences were detected in the remaining cases.

Weight monitoring is a strategy that, possibly in combination with other methods, may complement the quality assurance processes defined to improve the preparation of parenteral nutrient units.