Effect of total parenteral nutrition on biliary lipids in neonates

To study the effect of total parenteral nutrition (TPN) on biliary lipids in critically ill neonates, biliary lipid concentrations were determined in 13 neonates before starting TPN, in 8 receiving TPN for up to 2 weeks and in 9 receiving TPN for up to 8 weeks. Bile was very dilute in the 13 neonates not receiving TPN owing to a low concentration of bile acids. In many the bile-acid concentration was below the critical micellar concentration, thus cholesterol in bile was not dissolved. The neonates receiving TPN for up to 2 weeks showed a marked increase in bile-acid content and had levels above the critical micellar concentration. This apparently beneficial effect of TPN disappeared after 2 weeks and neonates who received TPN for 3 to 8 weeks again had bile-acid levels below the critical micellar concentration. Three conclusions may be drawn from this study: (a) in the fasting state before TPN is begun, the cholesterol content of bile relative to phospholipid and bile acids increased in linear fashion during the fasting period; (b) short-term TPN of up to 2 weeks' duration was associated with an increased bile-acid content to levels at which cholesterol could be dissolved; (c) neonates on long-term TPN and no oral intake secrete extremely dilute bile with an insufficient concentration of bile-acid molecules to form micelles to dissolve cholesterol. This finding may explain some of the adverse hepatobiliary changes associated with long-term administration of TPN.