PHARMACOLOGICAL LEVELS OF HEPARIN DO NOT DESTABILIZE NEONATAL PARENTERAL-NUTRITION

Background: Calcium and heparin are known to destabilize the lipid emu lsion of total parenteral nutrition (TPN). However, these observations were made over long peri ods 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. Methods: Lipid emulsion s tability was assessed over 30 minutes by measuring viscosity at 10 mmo l/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 pre parations on emulsion stability also was observed. Results: Heparin ca used an immediate increase in viscosity of pure Intralipid 20% (Intral ipid; Kabi Pharmacia AB, Stockholm, Sweden), which eventually separate d 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. Conclusions: Heparin and calcium destabilize I ntralipid. This is unlikely to cause problems for most infants receivi ng TPN, provided low heparin concentrations are used. In all cases, es pecially where the lipid ratio is high, the risk of the lipid phase se parating out can be further minimized by (1) the addition of multivita min preparations containing detergent or an emulsifying agent and (2) by having the shortest possible delivery tube between the point of mix ing the Lipid and amino acid solutions of TPN and entry into the infan t.