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

Effects of a medium-chain triacylglycerol/long-chain triacylglycerol fat emulsion containing a reduced ratio of phospholipid to triacylglycerol in pediatric surgical patients

OBJECTIVE

Medium-chain triacylglycerol (MCT) has been shown to provide better nutritional support than long-chain triacylglycerol (LCT). We compared the efficacy of MCT/LCT fat emulsions containing a usual (0.12) or a decreased (0.06) ratio of phospholipid to triacylglycerol (PL:TG) in pediatric patients under surgical stress.

METHODS

Three patient groups (n=10 in each) received equivalent amounts of glucose (12 g.kg(-1).d(-1)) and amino acids (2 g.kg(-1).d(-1)), but group A received a 10% MCT fat emulsion (PL:TG 0.06), group B received a 20% MCT fat emulsion (PL:TG 0.06), and group C received a 10% MCT/LCT fat emulsion (PL:TG 0.12) in amounts of 1.5 g.kg(-1).d(-1) in a randomized study. Total parenteral nutrition was given for 7 d. Blood samples were collected before total parenteral nutrition administration and on days 4 and 7 for determination of various biochemical indexes.

RESULTS

Serum phospholipid concentrations were significantly higher in group C than in group A or B on days 4 and 7 (P<0.05). Serum triacylglycerol and cholesterol concentrations and the very-low-density lipoprotein percentage were also significantly higher in group C than in group A or B on days 4 and 7 (P<0.05). The high-density lipoprotein percentage was significantly higher in group B on days 4 and 7 (P<0.05).

CONCLUSIONS

In pediatric patients under surgical stress, a total parenteral nutrition regimen containing an MCT/LCT fat emulsion with a decreased PL:TG ratio (0.06) is likely to result in partly better lipid and lipoprotein metabolism than an emulsion containing the usual ratio (0.12).

Propofol use precludes prescription of estimated nitrogen requirements

The objective was to determine whether reducing enteral nutrition to accommodate 1% Propofol-derived energy results in suboptimal nitrogen prescription. This was a prospective observational study of 85 consecutive patients requiring mechanical ventilation and receiving 1% Propofol. Enteral nutrition prescription often failed to meet nitrogen requirements (<90%, in 50.6%; <80%, in 21.1%), whereas fat provided 51% of total energy input, exceeding 2 g fat/kg/d in 20%. However, gastroparesis was common, resulting in suboptimal nutrition (median of requirements: energy 71%; nitrogen 57%). If energy balance had been strictly maintained, substituting 1% with 2% Propofol would reduce the number of patients failing to meet nitrogen requirements (1% vs 2%: <90%: in 58.8% vs 17.6%, P< .001; <80% in 35.3% vs 4.7%, P< .014). These effects are directly related to the amount of fat delivered with Propofol. Intensive care unit-associated gastroparesis commonly reduces enteral nutrition input. However, even where this is overcome, use of 1% Propofol frequently precludes prescription of estimated nitrogen requirements; either 2% Propofol or a non-Propofol alternative should be considered.

Home parenteral lipids in AIDS: a three-month study

Parenteral nutrition is a part of the nutritional support regimen of patients with AIDS-associated wasting syndrome and gastrointestinal dysfunction. The cholesterol (CHOL) level in human immunodeficiency virus (HIV) membrane is very high, and recent lipid formulations with high phospholipid (PL) content have demonstrated the ability to trap CHOL from endogenous sources, modifying the composition of cell membranes. We administered lipid-based home parenteral nutrition for 3 mo to malnourished AIDS patients. The patients were randomly divided into two groups: 23 received the regular 20% fat emulsion formulation, and 27 received a 2% formulation enriched 10-fold with PLs but containing the same amount of triglycerides. All patients gained weight and improved their activity level. Those receiving the high-PL composition showed increased serum CHOL concentrations (from 147 to 241 mg/dL; P < 0.01), but no increase was seen in the number of CD4 cells or improvement in immune function. HIV infectivity was not modified. Patients receiving regular PLs had significantly decreased (P < 0.02) IgA concentrations (from 776 to 300 mg/dL) and improved mitogen response to phytohemagglutinin and to concanavalin A. This formula, too, had no effect on HIV infectivity. We conclude that standard parenteral nutritional influences the nutritional and immune status of malnourished AIDS patients. A PL-enriched parenteral formulation can trap CHOL, but it does not affect the immune profile or HIV infectivity in patients with advanced disease.

Phospholipid-rich particles in commercial parenteral fat emulsions. An overview

In parenteral nutrition, the infusion of a fat EMU supplies both concentrated energy and covers the essential fatty acid requirements, the basic objective being to mimic as well as possible the input of chylomicrons into the blood. This objective is well met by the TAGRP of the EMU, which behave as true chylomicrons. However, commercial EMU also contain an excess of emulsifier in the form of PLRP. The number of these PLRP depends directly on the PL/TAG ratio of the EMU. They differ from the TAGRP by their composition (PL vs TAG and PL), their structure (PL in bilayer versus monolayer), and their granulometry (mean diameter 70-100 nm for PL vs 200-500 nm). The metabolic fate of the PLRP is similar in several ways to that of the TAGRP: exchanges of PL with the PL of the different cellular membranes and of the lipoproteins; captation of free CH from these same structures; and enrichment in apolipoproteins. However, because the TAGRP are the preferred substrates of the lipolytic enzymes, their clearance is much more rapid (half-life < 1 h) than that of the PLRP. As the infusion is continued, the PLRP end up accumulating and being transformed into LP-X (free CH/PL = 1; half-life of several days). As soon as the EMU is infused, the PLRP enter into competition with the TAGRP, in the lipolysis process as well as for sites of binding and for catabolism. The sites for catabolism of the two types of PAR are not the same: adipose tissues and muscles utilize the fatty acids and monoacylglycerols released by the lipolysis of the TAGRP; hepatocytes take up their remnants; the RES and the hepatocytes participate in the catabolism of the PLRP and the LP-X. Thus, prolonged infusion of EMU rich in PLRP leads to a hypercholesterolemia, or at least a dyslipoproteinemia, due to elevated LP-X, associated with a depletion of cells in CH, stimulating thus tissue cholesterogenesis. However, parenteral nutrition has evolved towards the utilization of EMU with a low PL/TAG ratio (availability of 30% formula) and less rapid delivery. For these reasons, the hypercholesterolemias that used to be observed with the 10% EMU have become much less spectacular or have even disappeared. It is interesting to note that patients on prolonged TPN, in particular those with a short small intestine, have weak cholesterolemia, reflecting a lowering of HDL and LDL not masked by elevated LP-X. At present, it seems difficult to produce sufficiently stable parenteral EMU devoid of PLRP. Notwithstanding, all the observations made since the introduction of the EMU in TPN are in favour of the use of PLRP-poor EMU. It is clear that the 10% formulas, and generally those with a PL/TAG ratio of 12/100, are ill-advised, especially in patients with a retarded clearance of circulating lipids.

Short-term effects of lipid-based parenteral nutrition in patients with acquired immunodeficiency syndrome and Pneumocystis carinii pneumonia

The human immunodeficiency virus (HIV) is surrounded by a rigid membrane rich in cholesterol. Extraction of cholesterol from the virus envelope reduces its infectivity in vitro. Large amounts of lipid emulsion phospholipids have the property of extracting cholesterol from cell membranes. The purpose of the present study was to observe the effects of high phospholipid loads on the lipid profile as well as HIV infectivity of patients with acquired immunodeficiency syndrome (AIDS). Fifty-nine patients with AIDS, weight loss, and presenting Pneumocystis carinii pneumonia (PCP) were included in a prospective, randomised, controlled study. In addition to standard therapy, patients received for 2 weeks 910 kcal of peripheral parenteral nutrition including 20% lipid emulsion (group 1) or a new 2% lipid emulsion with a high phospholipid/triglyceride ratio (1:1.7) (group 2). Activity level and biological, immune and HIV load and infectivity parameters were followed. Cholesterol increased from 113 +/- 44 to 228 +/- 103 mg/dl in the 2% group (P < 0.00001). Triglycerides also increased significantly (P < 0.02). IgA was decreased in the 2% group. HIV load and infectivity tests and leukocyte subsets did not demonstrate any effect of the lipid emulsions. It is concluded that the new 2% emulsion is a powerful cholesterol extractor. However, 2 weeks' administration failed to show any efficacy in modifying immune parameters or HIV infectivity in AIDS patients with PCP.