Physical stability of a total nutrient admixture for total parenteral nutrition.

The stability of a total nutrient admixture (TNA) has been postulated to be less than 7 days in refrigerated storage. When a TNA destabilizes, lipid particles coalesce and enlarge. Liposomes larger than 6 microns can obstruct pulmonary capillaries. A TNA containing 1500 ml of 7% Vamin, 1000 ml of 50% dextrose and 500 ml of 10% Intralipid, including the usual electrolytes, minerals and vitamins, was studied. Liposome size was measured in the original Intralipid and the TNA at intervals up to 14 days at 4 degrees C followed by 2 days at 22 degrees C. There was a small increase in liposome size up to 16 days. However, the number of particles larger than 6 microns was insignificant (by light microscopy, 3.9 +/- 2.4 [+/- SD] per 20 high-power fields; by Coulter counter, 99.8% smaller than 1.9 microns, with 0% larger than 6 microns; and by electron microscopy, 100% smaller than 2.0 microns). The osmolality and pH of the TNA were 1472 +/- 31 mOsm/kg and 5.5 +/- 0.1 respectively (mean +/- SD), with no significant change during the study times. The authors concluded that this TNA remains physically stable when refrigerated for 14 days and at room temperature for a further 2 days.