Pharmacologic levels of heparin do not destabilize neonatal parenteral nutrition

Calcium and heparin are known to destabilize the lipid emulsion of total parenteral nutrition (TPN). However, these observations were made over long periods of time, using 5 to 10 times the amount of heparin used in a neonatal intensive care unit. We investigated the effects of lower heparin concentrations with lipid-to-nutrient ratios normally administered to premature infants.

Lipid emulsion stability was assessed over 30 minutes by measuring viscosity at 10 mmol/L calcium after the addition of 0, 0.5, 1, and 5 IU heparin/mL. This was done at a range of lipid-to-nutrient ratios in clinical use. The effect of varying calcium concentration and different multivitamin preparations on emulsion stability also was observed.

Heparin caused an immediate increase in viscosity of pure Intralipid 20% (Intralipid; Kabi Pharmacia AB, Stockholm, Sweden), which eventually separated into two phases. Although changes in viscosity were observed at 1:1 lipid-to-nutrient ratios, no effect was seen at a 1:9 ratio. With the 1:1 ratio, the multivitamin preparations, MVI Pediatric (Rhone-Poulec Rorer, Montreal, Canada) and Vitlipid (Kabi Pharmacia AB), reduced the increase in viscosity.

Heparin and calcium destabilize Intralipid. This is unlikely to cause problems for most infants receiving TPN, provided low heparin concentrations are used. In all cases, especially where the lipid ratio is high, the risk of the lipid phase separating out can be further minimized by (1) the addition of multivitamin preparations containing detergent or an emulsifying agent and (2) by having the shortest possible delivery tube between the point of mixing the lipid and amino acid solutions of TPN and entry into the infant.