Plasma lipid and plasma lipoprotein concentrations in low birth weight infants given parenteral nutrition with twenty or ten percent lipid emulsion

Lipid composition and structure of commercial parenteral emulsions

In order to study the influence of the phospholipid/triacylglycerol (PL/TG) ratio of parenteral emulsions on the distribution and the physico-chemical properties of their fat particles, commercial 10, 20 or 30% fat formulas were fractionated by centrifugation into an upper lipid cake (resuspended in aqueous glycerol) and a subnatant or mesophase, from which a PL-rich subfraction (d = 1.010-1.030 g/l) was purified by density gradient ultracentrifugation. Chemical and 31P-NMR analyses of these fractions indicated that at least two types of fat particles coexist in parenteral emulsions: (i) TG-rich particles (mean diameter: 330, 400, 470 nm in the 10, 20, 30% emulsion) which contain practically all the TG and esterified phytosterols of native emulsions, but only a fraction of their PL, unesterified cholesterol and phytosterols, and other minor lipids; (ii) PL-bilayer particles or liposomes (mean diameter: 80-100 nm) which are constituted with the remaining PL and relatively very small amounts of TG and other lipids. The higher the oil content of the emulsion, the lower the amount of these PL-rich particles, which represent the major particle population of the mesophase. Indeed, minute amounts of TG-rich particles (probably the smallest ones) are also present in the mesophase, even in the PL-rich subfraction which contains the bulk of liposomal PL. Since the PL-rich particles of the infused emulsion generate lipoprotein X-like particles, only the large TG-rich particles can be considered as true chylomicron counterparts.

Nutrient needs of the preterm infant

Preterm infants exhibit special nutrient needs that differ substantially from other patient populations. Special characteristics include increased energy and protein requirements that must be addressed to prevent tissue catabolism and support growth. The immaturity of some organ systems may also complicate the administration of nutrition support. This article describes important characteristics of enteral and parenteral nutrition as it applies to the preterm infant.

Effects of intravenously infused egg phospholipids on lipid and lipoprotein metabolism in postoperative trauma

Lipid emulsions contain not only triglyceride (TG)-rich particles but also phospholipid (PL)-rich particles that are believed to trap free cholesterol and apoprotein E, when they are infused in excess. The present study was designed to evaluate the effects of such abnormal PL-rich particles on lipid metabolism during a 5-day infusion in man. Eighteen patients undergoing esophagectomy were evenly randomized to receive intravenously during 5 days 1.75 g.kg-1.d-1 long-chain TG from either a 10% lipid emulsion with a PL/TG weight ratio of 0.12 (group A), a 10% emulsion with a PL/TG weight ratio of 0.06 (group B), or a 20% emulsion with a PL/TG weight ratio of 0.06 (group C). Plasma PL, free cholesterol, and apoprotein E increased progressively in group A (4.1 +/- 0.3 mmol/L, 2.4 +/- 0.3 mmol/L, and 0.089 +/- 0.012 g/L on day 5, respectively) but not in groups B (2.7 +/- 0.3 mmol/L, 1.3 +/- 0.2 mmol/L, and 0.048 +/- 0.007 g/L) and C (2.4 +/- 0.2 mmol/L, 1.2 +/- 0.1 mmol/L, and 0.050 +/- 0.006 g/L). Free fatty acids and TGs remained constant and similar in each group postoperatively. After fat infusion had been stopped at the end of the fifth day, the elimination of plasma TGs over the next 4 hours was comparable in the three groups. We conclude that excess egg PLs induce alterations of plasma lipids even within a few days.

Feeding premature infants

We have tried to offer a rational approach to the methods of premature infant feeding. Most of our information is incomplete, and many of the presumptions used in deciding feeding technique are not based on reliable scientific data. The calculations presented in this discussion are valuable as teaching methods in the nursery. The complexity of the questions about premature infant feeding makes it necessary for personnel in the neonatal unit to focus regularly on infant feeding and to allow for time dedicated to considering their suggestions.

Effect of liposomal content of lipid emulsions on plasma lipid concentrations in low birth weight infants receiving parenteral nutrition

We studied the effects of phospholipid liposomes present in intravenously administered lipid emulsions on plasma lipid levels in preterm infants given 10% and 20% lipid emulsions. Twenty premature infants (birth weight 1454 +/- 54 gm) on a parenteral nutrition regimen received up to 4 gm triglycerides per kilogram per day in a 20% lipid emulsion for 2 weeks, and then received the 10% emulsion at 2 gm triglycerides per kilogram per day, which delivered the same total phospholipid load but twice the amount of liposomes. Triglyceride, total cholesterol, and phospholipid concentrations increased significantly when the infants were given 2 gm triglycerides per kilogram per day in the 10% emulsion rather than 4 gm/kg per day in the 20% emulsion (44 +/- 4 to 57 +/- 5 mg/dl, 134 +/- 6 to 162 +/- 9 mg/dl, and 204 +/- 8 to 251 +/- 10 mg/dl, respectively). Lipoprotein analysis indicated the presence of lipoprotein X-like particles in the low-density lipoprotein fraction and an increase of the intermediate-density lipoprotein fraction in infants who received the 10% emulsion. The presence of excess phospholipids in the 10% emulsion was associated with greater plasma lipid alterations. Therefore the use of 20% rather than 10% emulsion allows for more efficient triglyceride clearance, even at a higher triglyceride intake. Administration of emulsions that are relatively poor in phospholipid liposomes may allow delivery of > 2 gm triglycerides per kilogram per day to low birth weight infants.

Modification of erythrocyte membrane lipid composition induced by a single intravenous infusion of phospholipid-triacylglycerol emulsions in man

The study aimed to investigate whether, during short term infusion of lipid emulsions in man, red blood cell (RBC) membrane lipid composition was altered and RBC-free cholesterol (FC) could serve as a source of FC accumulated in the plasma. 3 normal subjects were infused intravenously with either 10% Intralipid [10% IL; PL:triglyceride (TG) weight ratio of 0.12] at the rates of 0.1, 0.2 and 0.3 g TG.kg(-1).h(-1) (providing PL intakes of 12, 24, 36 mg.kg(-1).h(-1), respectively) or with 30% Intralipid (30% IL; PL:TG ratio of 0.04) at the rate of 0.3 g TG.kg(-1).h(-1) (providing 12 mg PL.kg(-1).h(-1)). Infusion of 10% IL at a slow rate and 30% IL at a high rate caused no change in RBC and plasma FC content. However, 10% IL infusion at intermediate and high rates induced a significant decrease in RBC-FC: PL ratio. This change was still present at 18 h after the cessation of high rate infusion. RBC-FC: PL ratio and plasma PL measured during infusion were significantly correlated (r = -0.87, p < 0.001). FC efflux from RBC appears to contribute to the rise in plasma FC. This study indicates that the excessive amount of PL present as liposomes in some intravenous lipid emulsions can alter erythrocyte membrane lipid composition.

Practical aspects of achieving positive energy balance in low birth weight infants

For the low birth weight (LBW) infant, energy balance during the first several days of life usually is equated to absorption of sufficient energy to match energy expenditure. Most studies show that energy expenditure of nongrowing LBW infants is 45 to 55 kcal/kg/day. Hence, for energy equilibrium, energy intake minus energy losses (i.e., metabolizable energy intake) must be at least 50 kcal/kg/day. Intakes above this amount result in energy storage or positive energy balance, whereas lesser intakes necessitate mobilization of endogenous energy stores (negative energy balance). Some of the problems of achieving positive energy balance in LBW infants (e.g., feeding intolerance and fear of necrotizing enterocolitis) can be circumvented by use of parenterally delivered nutrients. On balance, virtually all LBW infants will tolerate parenteral amino acid, glucose, and lipid intakes, respectively, of 2, 5, and 1 gm/kg/day or an energy intake of about 40 kcal/kg/day. It usually is possible to increase energy intake of most infants by an additional 10 kcal/kg/day. Whether this is achieved with enterally delivered nutrients or additional parenteral glucose or lipid intake, including the necessary modifications to enhance tolerance (e.g., insulin, 20% vs 10% lipid emulsions, and lipid emulsions containing medium-chain fatty acids), must be decided for each infant based on his or her underlying condition, likelihood of tolerating either substrate, and the impact of intolerance on the underlying condition. The consequences of not providing an essential nutrient during the immediate postnatal period also must be considered. The fact that essential fatty acid deficiency develops more rapidly in infants receiving isocaloric (60 kcal/kg/day) parenteral intakes with versus without amino acids, the likelihood that brain growth continues despite negative energy balance, and the possibility that LBW infants may not be able to desaturate/elongate linoleic and linolenic acids to the more unsaturated, longer-chain fatty acids that are deposited in the developing brain suggest that these infants may require exogenous intakes of specific fatty acids.

Lipid infusion with different triglyceride cores (long-chain vs medium-chain/long-chain triglycerides): effect on plasma lipids and bilirubin binding in premature infants

The possible beneficial effects of infusing a lipid emulsion containing 50% by weight of medium-chain triglycerides (MCT) compared with a standard long-chain triglyceride (LCT) emulsion were studied in 18 premature neonates (gestational age less than 34 weeks) requiring parenteral nutrition. The infants were assigned in a double-blind manner to receive one of the two lipid emulsions over 17 hours a day as a supplemental regimen for total parenteral nutrition. A lipid load of 1 g/kg per day was initiated on the third day of life and was increased at the rate of 1 g/kg per day until a maximal dose of 3 g/kg per day was obtained on the fifth day of life and maintained thereafter. Both bound and unbound bilirubin decreased with both infusion regimens during the study period. Despite a marked increase in plasma free fatty acid levels (260% in the MCT/LCT group compared with 210% in the LCT group), the fraction of unbound (free) bilirubin was significantly lower in the MCT/LCT group (34% vs 13%). Free fatty acid levels, corrected to albumin, were positively correlated to the percentage of free bilirubin only for the LCT lipid infusion. The finding of a significant elevation of plasma cholesterol levels only in the MCT/LCT group is now under investigation. Use of the MCT-containing emulsion was not associated with a higher frequency of adverse effects than the commonly used LCT-containing emulsion.(ABSTRACT TRUNCATED AT 250 WORDS)

Introduction of intravenous lipid administration on the first day of life in the very low birth weight neonate

OBJECTIVE

To investigate lipid tolerance in sick, ventilator-dependent, very low birth weight infants from the first day of life and the effects of early introduction of intravenously administered lipid (IVL) on glucose homeostasis.

METHOD

Twenty-nine infants in the neonatal intensive care unit with birth weight less than 1500 gm received isocaloric, isonitrogenous parenteral feedings from day 1 with either IVL, 1 gm/kg from day 1 to 3 gm/kg from day 4 (group I; n = 16), or IVL added only from day 8 (group II; n = 13). Possible adverse clinical effects were monitored. Blood metabolites, nonesterified fatty acids, serum triglycerides, and insulin levels were determined daily. Arterial blood gases were measured and changes in partial pressures of oxygen and of carbon dioxide in arterial blood were compared between the two groups.

RESULTS

Early lipid infusion did not appear to have deleterious effects on blood gas tensions or to increase respiratory morbidity. The incidence of other adverse clinical effects that may be associated with IVL was not increased by earlier introduction of lipid. Serum lipid values were comparable to those of preterm infants receiving IVL at a later postnatal age. Blood glucose concentrations were higher in group II (mean, 7.50 (SEM 0.43) mmol/L) than in group I (mean, 6.01 (SEM 0.28) mmol/L; p less than 0.05). There was no evidence of increased gluconeogenesis in infants in group I and no correlation between blood glucose concentrations and serum nonesterified fatty acid concentrations.

CONCLUSION

When given infusion rates not exceeding 0.15 gm/kg/hr, sick, very low birth weight infants can tolerate IVL with stepwise dose increases from the first day of life without an increased incidence of possible adverse effects.

Increased lipoprotein X causes hyperlipidemia during intravenous administration of 10% fat emulsion in man

To clarify the mechanisms of hyperlipidemia during intravenous Intralipid 10%, lipoprotein profiles including lipoprotein X were studied in 13 patients receiving 2.0 g of fat per kilogram per day by Intralipid 10% over a period of 8 weeks. All patients were fed exclusively by total parenteral nutrition providing 1.1 g of amino acid and 30 kcal/kg per day. Intravenous administration of Intralipid 10% caused a marked increase of low-density lipoprotein (LDL), phospholipid, and cholesterol, especially free cholesterol, whereas triglyceride, very-low-density lipoprotein, and high-density lipoprotein remained within the normal range. Lipid composition of LDL approximated that of lipoprotein X progressively with the intravenous Intralipid 10%. Quantification of lipoprotein X revealed that its increase was proportionate with that of LDL and total lipid. From these findings, hyperlipidemia during intravenous Intralipid 10% is induced almost exclusively by the increased lipoprotein X.