HPE HPE 85 – Spring 2017 - Page 43

Practical therapeutics Issue 85 | Spring 2017 glucose to fat is an energy inefficient process, which leads to increased energy expenditure, increased oxygen consumption and increased carbon dioxide production. Excessive glucose intakes are thought to increase carbon dioxide production, which may have an effect on the weaning infants off artificial ventilation and contribute towards the development of liver impairment due to steatosis. Lipid requirements Lipid emulsions are an important component of a balanced PN regimen. They provide high energy needs without carbohydrate overload, improve the net nitrogen balance and prevent essential fatty acids deficiency. Lipids are incorporated into the structural components of cell and plasma membranes and are used for prostaglandin synthesis and platelet function. Lipid intake should usually cover 25–40% of non-protein calories in fully parenterally fed patients. Maximum fat oxidation occurs when lipids provide 40% of the non-protein PN calories in newborns and 50% in infants. Traditional lipid emulsions contain a mixture of egg phospholipids, soybean oil and glycerol. The soybean oil provides essential linoleic (omega 6), alpha- linolenic acid (omega 3) and other long chain polyunsaturated fatty acids (LC-PUFA). Long chain fatty acids are essential to the newborn for brain and retina development and so should be introduced on day 1 of PN. Biochemical evidence of essential fatty acid deficiency may develop in one to two days in the premature infant, where there are limited fat stores, and a diet without lipid. The recommended minimum linoleic acid content for premature infants is 0.25g/ kg/day and 0.1g/kg/day in term infants; 1 this requirement can be met using a traditional lipid emulsion in 0.5g/kg/day of a 20% solution. Omega 3 essential fatty acids (eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) are more Newer lipid emulsions have become available on the market and are licensed in paediatric patients. All contain LCT in varying proportions, which provide the essential fatty acids. These new lipid emulsions contain a combination of soybean oil and either olive oil, or medium chain triglycerides (LCT/MCT) or a combination of lipids (LCT/MCT/ olive oil/fish oil) (Table 1). important than omega 6 for brain development and complex neural function. They have positive effects on the immune system and are anti-inflammatory. Small-for-gestational-age neonates and low-birth weight infants may have a limited ability to metabolise fat and should have their serum triglyceride concentrations monitored. Lipid clearance is maximised when the solution is infused over 24 hours as a continuous rather than an intermittent infusion 1 . If plasma triglyceride concentrations during infusion exceed 250mg/dl or 2.82mmol/l, a reduction of lipid intake in newborns, premature and young infants should be considered. There is no evidence to support routine lipid reduction in critically ill or infected patients and lipid may be the preferred energy source in sepsis. Lipid emulsions have been shown to inhibit bacterial c