Answering the Fat Emulsion Contamination Question: Three in One Admixture vs Conventional Total Parenteral Nutrition in a Clinical Setting

Fat emulsions (FE) support microbial growth when inoculated in vitro; dextrose/amino acid solutions (D/ AA) do not. Can FE be safely added to D/AA when delivered over 24 hrs? We attempted to answer this question by culturing both conventional (C) total parenteral nutrition (TPN), in which the FE and D/AA are given separately, and the 3-in-1 admixture TPN, in which all components are delivered in one bag. Two-hundred TPN fluid cultures were obtained serially by collecting 1 ml of fluid from the distal-most connection when the TPN was changed every 24 hrs. Quantitative and qualitative cultures were obtained. One hundred sixty-six (83%) were negative. Of the 34 (17%) positive cultures, 15 (17% of 88) were from the conventional system whereas 19 (17% of 112) were from the 3-in-1 system. Six clinically septic patients furnished 11 TPN fluid specimens which grew >400 colonies/ ml. Seven (8% of 88) of these were from the conventional system whereas four (3.6% of 112) were from the 3-in-1 system. All had distant sites of sepsis. The 23 remaining positive TPN fluid cultures grew less than 25 colonies/ml, with 20 growing Staphylococcus epidermidis. All of these patients were clinically well and there was no significant difference in the distribution of positive cultures between the conventional system (9%) and the 3-in-1 system (13%). We therefore conclude: (1) the 3-in-1 admixture system does not have an increased risk of contamination compared to the conventional system; and (2) positive fluid cultures in clinically well patients may have been due to sampling technique with catheter hub rather than fluid contamination being the source of the positive culture. (Journal of Parenteral and Enteral Nutrition 12:356-359, 1988)