title: AGREEMENT BETWEEN DIFFERENT EQUATIONS TO ESTIMATE OSMOLARITY OF PARENTERAL NUTRITION SOLUTIONS.
abstract: BACKGROUND
  our aim was to measure the osmolality of several PN formulas at different component concentrations to determine if equations described in literature to calculate osmolarity accurately predict osmolalality in other experimental conditions different than these used to develop them.
  
  
  METHODS
  osmolality of 12 different types of PN solutions, 9 for central and 3 for peripheral perfusion were measured by using freezing point depression in cross-sectional study. We evaluated the agreement (Pearson correlation test) and differential bias between measured osmolality and calculated osmolarity for three different equations described in the literature: Pereira Da Silva, ASPEN Practice Manual and ASPEN guidelines.
  
  
  RESULTS
  mean ± SD osmolality of PN solutions was 1789 ± 256 (range 1 540 - 2 372) and 751 ± 64 mOsm/kg (range 689 - 817) for central and peripheral infusion, respectively. The osmolality of PN formulations was mainly due to glucose (r = 0.975) and amino acids (r = 0.948). All studied equations had a good correlation in the bivariate analysis (p = 0.000). All equations had a trend to underestimate the osmolality compared with the measured value. However, ASPEN guidelines equation overestimated the osmolality for peripheral PN.
  
  
  CONCLUSIONS
  measurement of osmolality of peripheral PN solutions is important to reduce the risk of phlebitis. The different equations described previously show a good correlation between them although in general underestimate the osmolality.
authors.affiliation: Clinical Nutrition Unit. Department of Endocrinology and Nutrition. Hospital Universitario 12 de Octubre, Madrid.. mvalero.hdoc@salud.madrid.org.
authors.forename: M A
authors.initials: MA
authors.lastname: Valero Zanuy
authors.affiliation: Department of Pharmacy. Hospital Universitario 12 de Octubre, Madrid.. spablos.hdoc@salud.madrid.org.
authors.forename: S
authors.initials: S
authors.lastname: Pablos Bravo
authors.affiliation: Department of Pharmacy. Hospital Universitario 12 de Octubre, Madrid.. alazaro.hdoc@salud.madrid.org.
authors.forename: A
authors.initials: A
authors.lastname: Lazaro Cebas
authors.affiliation: Department of Clinical Biochemistry. Hospital Universitario 12 de Octubre, Madrid, Spain.. mjsanchez.hdoc@salud.madrid.org.
authors.forename: J
authors.initials: J
authors.lastname: Garcia Sanchez
authors.affiliation: Department of Pharmacy. Hospital Universitario 12 de Octubre, Madrid.. pgomis.hdoc@salud.madrid.org.
authors.forename: P
authors.initials: P
authors.lastname: Gomis Muñoz
authors.affiliation: Clinical Nutrition Unit. Department of Endocrinology and Nutrition. Hospital Universitario 12 de Octubre, Madrid.. jmmoreno.hdoc@salud.madrid.org.
authors.forename: J M
authors.initials: JM
authors.lastname: Moreno Villares
authors.affiliation: Clinical Nutrition Unit. Department of Endocrinology and Nutrition. Hospital Universitario 12 de Octubre, Madrid.. mleon@h12o.es.
authors.forename: M
authors.initials: M
authors.lastname: Leon Sanz
mesh_terms: D000465:Algorithms; D003430:Cross-Sectional Studies; D006801:Humans; D009994:Osmolar Concentration; D010288:Parenteral Nutrition; D057947:Parenteral Nutrition Solutions / Q000737:chemistry*
chemical_list: D057947:Parenteral Nutrition Solutions