Insulin Instability in Parenteral Nutrition Admixtures

Background Biosynthetic human recombinant short-acting insulin is added to parenteral nutrition (PN) admixtures to nourish glucose-intolerant patients. Insulin, however, is electrostatically attracted and inactivated by ethyl-vinyl-acetate (EVA) bags and filling system tubes. Our aim was to verify and quantify the presence of insulin in PN with and without intravenous lipid emulsion (ILE), just after addition (T0) until the infusion's end (T24). Methods Four undiluted samples of 12 different PN complete admixtures (6 with ILE and 6 without), each containing 250 g of glucose in a 2000 mL volume, were taken and analyzed at T0 and T24 by an automated electrochemiluminescence immunoassay after the addition of biosynthetic human recombinant short-acting insulin at increasing doses (from 6 to 72 IU/bag) by an automated compounding device. Assay sensitivity was set at 2 μIU/mL. Admixtures with and without ILE were compared in terms of insulin-detected amounts at T0 and T24. Results Regardless of the amount initially provided, insulin was missing in PN without ILE. In admixtures with ILE, the greater the insulin and ILE doses initially included, the higher the insulin availability at T0 and T24, both in absolute terms and as a percentage of the initial amount (from 3 to 81% at T0 and from 2.5 to 72.5% at T24). ILE may prevent insulin attraction to plastic surfaces. Conclusions Insulin is recovered in the presence of ILE in PN even though considerable amounts are untraceable. This aspect needs verification. Until then, insulin should safely be injected in a different manner in uncontrolled situations.