FAT EMULSION PARTICLE-SIZE DISTRIBUTION IN TOTAL NUTRIENT ADMIXTURES

The fat particle-size distribution in and physical stability of two commercially available lipid emulsions before and after their use in total nutrient admixtures (TNAs) are reported. Four TNAs without electrolytes and four TNAs with electrolytes were prepared; each type of TNA was prepared with Liposyn II and with Intralipid. Particle size was measured in the <1-mum range by using photon correlation spectroscopy and in the 2-60-mum range by using light blockage. Admixtures with or without electrolytes were stored for two or nine days at 4-degrees-C followed by one day at 25-degrees-C. For the fraction of fat particles of <1 mum in diameter, Intralipid and Liposyn II had a mean particle size of 374 and 313 nm, respectively. The admixtures containing electrolytes showed a decrease in mean particle size of about 7%. Admixtures with Intralipid contained 2 x 10(7) particles larger than 2 mum per milliliter (1.7% of total fat), compared with 1 x 10(6) particles per milliliter (0.05-0.15% of total fat) for admixtures with Liposyn II. The addition of electrolytes increased the particle counts for Liposyn II-containing admixtures. Upon storage, Intralipid-containing admixtures with electrolytes showed an initial increase followed by a decrease in the mean diameter of particles of <1 mum. All the admixtures were stable in terms of pH and visual appearance. Intralipid-containing admixtures with electrolytes showed a decrease in the number of particles in the 2-60-mum size range, while Liposyn II-containing admixtures with electrolytes showed an increase. Despite this, the number of particles in Intralipid-containing admixtures at 10 days was 3-10 times higher than the number in corresponding Liposyn II-containing admixtures. Admixtures prepared from commercially available i.v. fat emulsions differed in the content of fat particles larger than chylomicrons. Large particles contributed as much as 1.0 g of fat per liter of admixture.