Use of a lipid containing medium chain triglycerides in patients receiving TPN: a randomized prospective trial

Efficacy of Medium-chain Triglycerides Compared with Long-chain Triglycerides in Total Parenteral Nutrition in Patients with Digestive Tract Cancer Undergoing Surgery

The objectives of this prospective, randomized study were to evaluate the efficacy and tolerability of the short-term use of medium-chain triglyceride/long-chain triglyceride (MCT/LCT) fat emulsions, and to compare the hematologic and biochemical effects of MCT/LCT fat emulsions with LCT fat emulsions in gastrointestinal (GI) tract cancer patients following surgery. Thirty patients with GI tract cancer requiring total parenteral nutrition (TPN) were equally randomized to receive MCT/LCT or LCT emulsions for 7 days. After 7 days, no sign of complications directly related to administration of fat emulsions was observed and there were no marked differences in anthropometry, length of hospital stay, and surgical complication rates between the two groups. However, MCT/LCT significantly improved plasma prealbumin concentration (p = 0.005). Changes in complements C3 and C4, total lymphocyte count, and immunoglobulins after TPN were not significantly different between the groups. Serum triglyceride and cholesterol levels remained constant. The serum insulin level in the MCT/LCT group was higher than in the LCT group (p = 0.048). Our data revealed that MCT/LCT fat emulsions significantly enhanced nutritional status in patients with GI tract cancer, indicated by higher prealbumin levels, which might be partially due to the higher circulating insulin levels in the MCT/LCT group.

Clinical and metabolic effects of two lipid emulsions on the parenteral nutrition of septic patients

OBJECTIVE

We compared the metabolic and clinical effects of two lipid emulsions, long-chain triacylglycerols (LCT) and a mixture of medium- and long-chain triacylglycerols (MCT/LCT), in septic patients.

METHODS

Both groups received total parenteral nutrition (TPN) with a solution enriched with branched-chain amino acids (BCAA). Seventy-two septic patients received TPN with MCT/LCT (group 1) or LCT (group 2). Before starting TPN (basal) and 10 d after (final), various parameters were evaluated.

RESULTS

Twenty-six subjects in each group completed the study. Both groups showed an increase in cholestasis enzymes, with no significant changes in lipid parameters. The rise of retinol-binding protein and the recovery of nitrogen balance were significantly greater in group 1. A multivariate analysis of nutritional markers and catabolic parameters showed a better evolution in group 1 (P = 0.002). The MCT/LCT group exhibited a significant increase of insulin levels. Overall mortality and length of stay in the intensive care unit were not affected by the lipid emulsion.

CONCLUSIONS

In septic patients who received TPN with a solution enriched with BCAAs, the use of an emulsion containing MCT provided them with a greater recovery of their nutrition status than the traditional LCT formula, without influencing the outcome.

Constant infusion rates of lipid emulsions to stabilize plasma triglyceride concentrations: medium-chain triglyceride/long-chain triglyceride emulsions (MCT/LCT) versus LCT

As medium-chain triglyceride emulsions (MCT) are more rapidly hydrolyzed than long-chain triglyceride emulsions (LCT), MCT/LCT tends to be infused faster than LCT. The purpose of the present study was to determine the most appropriate infusion rate for MCT/LCT to stabilize plasma concentrations of triglyceride (TG), being equivalent to the optimal infusion rate of the emulsion. A TG clamp was set up by raising the mean +/- SD concentrations of TG in plasma, being 1.08 +/- 0.18 delta mmol l(-1) for LCT, and 1.65 +/- 0.31 delta mmol l(-1) for MCT/LCT after a 50-min priming infusion of each emulsion. Thereafter, the infusion rate of lipid was controlled every 10 min to maintain a steady concentration of TG for a period of 150 min. A constant infusion of glucose at 0.32 g/kg body weight (BW) per h was administered for the test period. The weight-based rate of the infusion to maintain a steady state of plasma TG concentrations did not differ between MCT/LCT and LCT, being 0.125 +/- 0.013 vs 0.117 +/- 0.021 g/kg BW per h, while the molar-based infusion rate was 0.203 +/- 0.021 mmol/kg BW per h for MCT/LCT and 0.132 +/- 0.023 mmol/kg BW per h for LCT (P < 0.05). These results suggest that although 54% more molar MCT/LCT-TG can be hydrolyzed during a constant infusion, MCT/LCT should not be infused at a rate faster than 0.1 g/kg BW per h under a steady state.

Use of a mixture of medium-chain triglycerides and longchain triglycerides versus long-chain triglycerides in critically ill surgical patients: a randomized prospective double-blind study

Twenty critically-ill surgical patients who needed total parenteral nutrition were randomly enrolled in a double-blind study comparing two intravenous fat emulsions: one containing a mixture of 50% medium-chain triglycerides and 50% long-chain triglycerides and another containing 100% longchain triglycerides. The purpose of this study was to investigate metabolic and biochemical differences between both emulsions with special reference to liver enzymes. After a baseline period of 24 h with only glucose and NaCl infusion, the lipid emulsion was added continuously during 24 h over 5 days. The parenteral nutrition was administered in mixture bags containing amino-acids, glucose and lipids together. Two-thirds of the non-protein calories were administered as glucose 40% and one third as either long-chain triglycerides or a mixture of medium-chain triglycerides and long-chain triglycerides. The total amount of non-protein calories received was the measured energy expenditure during the baseline period plus 10% and was fixed during the study. Plasma substrate concentrations, energy expenditure, and nitrogen balance were determined and arterial blood samples were taken. No toxic effects or complications attributable to one of the two emulsions were observed. There was no significant difference in energy expenditure, nitrogen balance, liver function tests, carnitine, transferrin, pre-albumin, albumin, cholesterol, triglycerides and free fatty acids. The only parameter that showed a different pattern of reaction between the two emulsions was serum bilirubin concentration. In this study no evidence of any advantageous effect of a mixture of medium-chain triglycerides and long-chain triglycerides was seen.

Parenteral use of medium-chain triglycerides: a reappraisal

Over the last two decades, the clinical use of intravenous fat emulsions for the nutritional support of hospitalized patients has become routine. During this time long-chain triglycerides (LCT) derived from soybean and/or safflower oils were the exclusive lipid source for these emulsions, providing both a safe calorically dense alternative to dextrose and essential fatty acids needed for biologic membranes and the maintenance of immune function. During the past decade, the availability of novel experimental triglycerides for parenteral use has generated interest in the use of these substrates for nutritional and metabolic support. Medium-chain triglycerides (MCT), long advocated as a superior substrate for parenteral use, possess many unique physiochemical and metabolic properties that make them theoretically advantageous over their LCT counterparts. Although not yet approved in the United States, preparations containing MCT have been widely available in Europe. Intravenous MCT preparations, either as physical mixtures or structured lipids, have been used clinically in patients with immunosuppresion, critical illness, liver and pulmonary disease and in premature infants. Despite great promise, the clinical data comparing the efficacy of MCT-based lipid emulsions to their LCT counterparts has been equivocal. This may be due in part to the limited nature of the published clinical trials. Measures of efficacy for parenteral or enteral nutritional products has taken on new meaning, in light of the reported experience using immunomodulatory nutrients. Current concerns about cost of medical care and resource use warrant careful deliberation about the utility of any new and expensive therapy. Until clinical data can fulfill expectations derived from animal studies, it is difficult to advocate the general use of MCT-based lipid emulsions. Future clinical studies with MCT-based emulsions should have clear outcome objectives sufficient to prove their theorized metabolic superiority.

Kinetics of medium-chain triglycerides and free fatty acids in healthy volunteers and surgically stressed patients

To determine the hydrolysis rate of medium-chain triglycerides (MCTs) to medium-chain free fatty acids (MCFAs) and the disposition rate of MCFAs, five healthy volunteers (H) and eight surgically stressed patients (S) received 0.5 mL of Lipofundin 20% per kilogram body weight as an intravenous bolus. Serum MCTs (C8 and C10) and MCFAs were measured by high-performance liquid chromatography during the 120 minutes postinjection. A linear two-compartment model was found to be descriptive and robust: the apparent volumes of distribution were found to be similar in healthy and surgical subjects for both MCTs and MCFAs. The first-order transformation rate constant (hydrolysis) from MCTs to MCFAs was not significantly different between the H and S groups (overall 0.112 +/- 0.022/min, C8; 0.078 +/- 0.020/min, C10). The rate constant for tissue MCFA uptake from plasma was significantly different between S and H subjects both for C10 alone (H: 0.0337 +/- 0.0078; S: 0.1194 +/- 0.0240; p = .020) and for C8 and C10 together (H: 0.0382 +/- 0.0054; S: 0.1012 +/- 0.0168; p = .008), whereas it failed to attain significance when C8 alone was considered (H: 0.047 +/- 0.0077; S: 0.0829 +/- 0.0230; p = .210). These results show that use of MCTs is increased in surgical patients because of enhanced tissue uptake of the corresponding free fatty acids, whereas there does not seem to be an increase of MCT hydrolysis in response to acute disease. This would indicate that the stressed patient is in fact able to effectively use this alternative lipid substrate in the face of increased metabolic demand.

Medium- and long-chain triglycerides have different effects on the synthesis of tumor necrosis factor by human mononuclear cells in patients under total parenteral nutrition

OBJECTIVE

Lipid emulsions containing both long- and medium-chain triglycerides (LCT/MCT) have been used in total parenteral nutrition (TPN) regimens and seem to have certain advantages for seriously ill patients. The aim of the present study was to investigate the effect of lipid emulsions containing 100% LCT or 50% LCT/50% MCT on tumor necrosis factor (TNF) production by human mononuclear cells.

STUDY DESIGN

This was a prospective study, in which 20 malnourished patients were randomly allocated to receive either 100% LCT or 50% LCT/50% MCT for > 30 days. We measured TNF synthesis before initiation of TPN, as well as at 15 and 30 days during TPN.

SETTING

Departments of Medicine and Surgery, Patras University Medical School, Patras, Greece.

PARTICIPANTS

Members of the staff of the Departments of Medicine and Surgery, Patras University Medical School.

RESULTS

We found that TNF production was significantly (p < 0.01) elevated at 30 days in the LCT group, while no significant differences were detected in the LCT/MCT group.

CONCLUSIONS

It is concluded that long-term TPN formulas, where LCT have been partially replaced by MCT, do not change TNF synthesis by peripheral blood mononuclear cells, and this may be beneficial in seriously ill, cachectic patients.

Parenteral nutrition in the critically ill: use of a medium chain triglyceride emulsion

OBJECTIVES

The study investigated the use of an intravenous lipid emulsion containing medium chain triglycerides (MCTs) in critically ill patients, and compared the effects with those of a conventional long chain triglyceride (LCT) preparation.

DESIGN

Patients received a parenteral nutrition regime including either 500 ml 20% Lipofundin MCT/LCT (1/1) per day, or 500 ml 20% Lipofundin S (LCT) infused over 8 h each evening.

SETTING

The patients were receiving treatment, including assisted ventilation, in the Intensive Care Unit of a large teaching hospital. All patients on this unit for at least 3 days and who were likely to receive parenteral nutrition for at least a week were considered, unless they had severe renal or liver disease, or trauma/major surgery in the previous 3 days. Because ICU patients are a heterogenous group, subjects were randomised within clinical groups to receive either lipid. There were 24 patients entered into the study and the data on 20 matched patients is reported.

MEASUREMENTS AND RESULTS

Blood specimens were collected pre-TPN, daily at 0800 and after 5 h lipid infusion on days 1 and 6. Urine collections (24 h) were also performed. There were no apparent adverse effects due to the new MCT/LCT emulsion. Plasma ketone and glycerol concentrations were higher during MCT/LCT infusion, but 8 h post infusion plasma levels of ketones, triglycerides, non-esterified fatty acids and glucose were similar. Urinary carnitine excretion was high in all patients and was not significantly different between the groups. Nitrogen balance was less negative in patients receiving MCT/LCT on days 6 and 9.

CONCLUSION

MCTs are rapidly hydrolysed and oxidised to fatty acids and ketones which can be readily utilised. This study indicates that intravenous lipid emulsion containing MCT are safe in critically ill patients and may have advantages over LCT. The number and range of patients studied was, however, small and larger studies are needed.

[Energy substrates in parenteral nutrition]

The most appropriate nutriment for total parenteral feeding (TPF) must be nutritionally efficient, safe and easy to use. Glucose is the most used carbohydrate as it has most of these qualities, as well as a high rate of metabolism by all tissues. It has not been clearly demonstrated that the administration of exogenous insulin with glucose improves nitrogen retention. Substitutes for glucose, such as fructose, maltose, galactose or polyols (xylitol, surbitol, glycerol) are not really superior to glucose itself. On the other hand, they have major side-effects. Therefore, they are not much used as energy substrates for TPF, at least not for long term TPF. Intravenous fat emulsions have taken an important place as a source of energy during TPF. Fat emulsions containing long chain triglycerides (LCT) supply essential fatty acids (EFA) (linolenic and linoleic acids), thus preventing EFA deficiency. The metabolism of fat emulsions is influenced by various factors: age, metabolic and nutritional status, the amount of glucose intake, insulin deficiency, sepsis, heparin therapy. Recently, medium chain triglycerides (MCT) have been proposed as an alternative energy source. The latter are cleared more rapidly from the blood, and are therefore less liable to be deposited in the liver and adipose tissue; they are also oxidized more quickly and more completely. MCT are safe to use at a rate of less than 0.12 g.kg-1.h-1 and with a MCT/LCT ratio less than 3 to 1. The simultaneous administration of glucose prevents an acceleration of ketogenesis. MCT/LCT emulsions are a safe and effective source of calories. It is important that those patients for whom such nutriment may be of particular interest should be identified. Fat emulsions associated with glucose seem to be more efficient in terms of nitrogen sparing effect than glucose alone. They also avoid the problems due to the infusion of large amounts of glucose (excessive carbon dioxide production, fatty infiltration of the liver), while there is no EFA deficiency. If the infusion of TPF nutriment must be continuous in intensive care patients, or during the postoperative period, cyclic nocturnal parenteral nutrition over a 12 or 16 hour period may be used in patients who are not in a catabolic state, or only mildly so. This is a safe and efficient method of nutritional support, which reduces the incidence rate of TPF-induced cholestasis.

Comparison of medium and long chain triglyceride metabolism in intensive care patients on parenteral nutrition

The metabolic effects of an intravenous lipid emulsion containing medium chain triglycerides (MCTs) were studied in eleven critically ill, ventilated patients receiving parenteral nutrition. The effects were compared in a cross-over study with those of a conventional emulsion containing only long chain triglycerides (LCTs). The lipid was well tolerated, but there were differences in the metabolic effects with a significantly greater increase in the plasma concentrations of glycerol and ketones during MCT/LCT infusion compared to LCT. The plasma concentration of non esterified fatty acids was also higher. This fell rapidly post infusion. Since non esterified fatty acids and ketones are readily available energy sources for tissues lipid emulsions containing MCT may prove valuable for catabolic, critically ill patients.