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

Impact of critical illness on cholesterol and fatty acids: insights into pathophysiology and therapeutic targets

Critical illness is characterized by a hypercatabolic response encompassing endocrine and metabolic alterations. Not only the uptake, synthesis and metabolism of glucose and amino acids is majorly affected, but also the homeostasis of lipids and cholesterol is altered during acute and prolonged critical illness. Patients who suffer from critically ill conditions such as sepsis, major trauma, surgery or burn wounds display an immediate and sustained reduction in low plasma LDL-, HDL- and total cholesterol concentrations, together with a, less pronounced, increase in plasma free fatty acids. The severity of these alterations is associated with severity of illness, but the underlying pathophysiological mechanisms are multifactorial and only partly clarified. This narrative review aims to provide an overview of the current knowledge of how lipid and cholesterol uptake, synthesis and metabolism is affected during critical illness. Reduced nutritional uptake, increased scavenging of lipoproteins as well as an increased conversion to cortisol or other cholesterol-derived metabolites might all play a role in the decrease in plasma cholesterol. The acute stress response to critical illness creates a lipolytic cocktail, which might explain the increase in plasma free fatty acids, although reduced uptake and oxidation, but also increased lipogenesis, especially in prolonged critical illness, will also affect the circulating levels. Whether a disturbed lipid homeostasis warrants intervention or should primarily be interpreted as a signal of severity of illness requires further research.

Omega-3 fatty acids in parenteral nutrition - A systematic review with network meta-analysis on clinical outcomes

BACKGROUND & AIMS

Accumulating scientific evidence supports the benefits of parenteral nutrition (PN) with fish oil (FO) containing intravenous lipid emulsions (ILEs) on clinical outcomes. Yet, the question of the most effective ILE remains controversial. We conducted a network meta-analysis (NMA) to compare and rank different types of ILEs in terms of their effects on infections, sepsis, ICU and hospital length of stay, and in-hospital mortality in adult patients.

METHODS

MEDLINE, EMBASE, and Web of Science databases were searched for randomized controlled trials (RCTs) published up to May 2022, investigating ILEs as a part of part of PN covering at least 70% of total energy provision. Lipid emulsions were classified in four categories: FO-ILEs, olive oil (OO)-ILEs, medium-chain triglyceride (MCT)/soybean oil (SO)-ILEs, and pure SO-ILEs. Data were statistically combined through Bayesian NMA and the Surface Under the Cumulative RAnking (SUCRA) was calculated for all outcomes.

RESULTS

1651 publications were retrieved in the original search, 47 RCTs were included in the NMA. For FO-ILEs, very highly credible reductions in infection risk versus SO-ILEs [odds ratio (OR) = 0.43 90% credibility interval (CrI) (0.29-0.63)], MCT/soybean oil-ILEs [0.59 (0.43-0.82)], and OO-ILEs [0.56 (0.33-0.91)], and in sepsis risk versus SO-ILEs [0.22 (0.08-0.59)], as well as substantial reductions in hospital length of stay versus SO-ILEs [mean difference (MD) = -2.31 (-3.14 to -1.59) days] and MCT/SO-ILEs (-2.01 (-2.82 to -1.22 days) were shown. According to SUCRA score, FO-ILEs were ranked first for all five outcomes.

CONCLUSIONS

In hospitalized patients, FO-ILEs provide significant clinical benefits over all other types of ILEs, ranking first for all outcomes investigated.

REGISTRATION NO

PROSPERO 2022 CRD42022328660.

Trends in liver profile and nutrition outcomes in children undergoing intestinal rehabilitation using a mixed lipid injectable emulsion

BACKGROUND

Pediatric patients undergoing intestinal rehabilitation (IR) using parenteral nutrition (PN) are at higher risk for intestinal failure-associated liver disease (IFALD). Nutrition support, growth, and liver enzymes must be closely monitored while incorporating hepatoprotective lipid injectable emulsions for optimal patient outcomes.

OBJECTIVE

Describe trends of liver profile and nutrition outcomes for pediatric patients undergoing IR using SMOFlipid[SO,MCT,OO,FO-ILE]).

METHODS

After IRB approval, patients undergoing IR using SO,MCT,OO,FO-ILE were observed prospectively from January 1, 2017, through December 1, 2019. The following values were documented monthly: aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TB), triene/tetraene ratio (TTR), micronutrient and trace element levels, z-scores for growth, and nutrition support regimen. Values were compared.

RESULTS

The group involved 16 pediatric patients for an average of 16.4 months on SO,MCT,OO,FO-ILE. By the end of the study, mean PN hours per day decreased by 34.7%, P < 0.0001. Mean PN calories per kilogram decreased from 60.4 to 48.3, P = 0.004. SO,MCT,OO,FO-ILE calories met the recommended dietary intake goal of 30% at the average 1.6 g/kg. Growth z-scores increased in those <2 YOA , although the body mass index decreased in our >2 YOA cohort. Total nutrition received from PN decreased to 62%: a 32% change, P = 0.001. There were no statistically significant changes in AST or ALT. TB decreased by 67.08%, P <0.05. No essential fatty acid deficiency was reported (TTR < 0.02). There were no changes in micronutrient and trace element deficiencies. There was zero new incidences of IFALD.

CONCLUSIONS

SO,MCT,OO,FO-ILE may be used long term in pediatric patients while promoting growth and development.

Trial Design in Critical Care Nutrition: The Past, Present and Future

The specialty of nutrition in critical care is relatively modern, and accordingly, trial design has progressed over recent decades. In the past, small observational and physiological studies evolved to become small single-centre comparative trials, but these had significant limitations by today’s standards. Power calculations were often not undertaken, outcomes were not specified a priori, and blinding and randomisation were not always rigorous. These trials have been superseded by larger, more carefully designed and conducted multi-centre trials. Progress in trial conduct has been facilitated by a greater understanding of statistical concepts and methodological design. In addition, larger numbers of potential study participants and increased access to funding support trials able to detect smaller differences in outcomes. This narrative review outlines why critical care nutrition research is unique and includes a historical critique of trial design to provide readers with an understanding of how and why things have changed. This review focuses on study methodology, population group, intervention, and outcomes, with a discussion as to how these factors have evolved, and concludes with an insight into what we believe trial design may look like in the future. This will provide perspective on the translation of the critical care nutrition literature into clinical practice.

Composition and Functionality of Lipid Emulsions in Parenteral Nutrition: Examining Evidence in Clinical Applications

Lipid emulsions (LEs), an integral component in parenteral nutrition (PN) feeding, have shifted from the primary aim of delivering non-protein calories and essential fatty acids to defined therapeutic outcomes such as reducing inflammation, and improving metabolic and clinical outcomes. Use of LEs in PN for surgical and critically ill patients is particularly well established, and there is enough literature assigning therapeutic and adverse effects to specific LEs. This narrative review contrarily puts into perspective the fatty acid compositional (FAC) nature of LE formulations, and discusses clinical applications and outcomes according to the biological function and structural functionality of fatty acids and co-factors such as phytosterols, α-tocopherol, emulsifiers and vitamin K. In addition to soybean oil-based LEs, this review covers clinical studies using the alternate LEs that incorporates physical mixtures combining medium- and long-chain triglycerides or structured triglycerides or the unusual olive oil or fish oil. The Jaded score was applied to assess the quality of these studies, and we report outcomes categorized as per immuno-inflammatory, nutritional, clinical, and cellular level FAC changes. It appears that the FAC nature of LEs is the primary determinant of desired clinical outcomes, and we conclude that one type of LE alone cannot be uniformly applied to patient care.

New Parenteral Lipid Emulsions for Clinical Use

Routine use of parenteral lipid emulsions (LE) in clinical practice began in 1961, with the development of soybean oil (SO) - based LE. Although clinically safe, experimental reports indicated that SO-based LE could exert a negative influence on immunological functions. Those findings were related to its absolute and relative excess of omega-6 polyunsaturated fatty acids (PUFA) and the low amount of omega-3 PUFA and also to its high PUFA content with an increased peroxidation risk. This motivated the development of new LE basically designed along the reduction of omega-6 PUFA and the omega-3 PUFA addition in order to obtain balanced levels of the omega-6/omega-3 ratio. The new LE for clinical use (available in Europe and South America) are differentiated by their content in polyunsaturated (omega-6 and omega-3), monounsaturated, and saturated fatty acids (FA), as well as FA source of their origin, including soy, coconut, olive, and fish oil. This article presents the new LE nutrition and energy functions but also its biochemical, metabolic, and immunomodulating aspects, according to their FA content. LE at 20% when infused from 1.0 to 2.0 g/kg body weight/day rates, either alone or in association with amino acids and glucose, are safe and well tolerated in routine clinical practice. LE combining SO with medium-chain triglycerides and/or olive oil have less omega-6 PUFA and are better metabolized, with less inflammatory and immunosuppressive effects than in relation to pure SO-based LE. The omega-3 PUFA used alone or as component of a new and complex LE (soy, MCT, olive and fish oil) has demonstrated anti-inflammatory and immunomodulatory effects.

Prevalence of ketosis, ketonuria, and ketoacidosis during liberal glycemic control in critically ill patients with diabetes: an observational study

Background

It is uncertain whether liberal glucose control in critically ill diabetic patients leads to increased ketone production and ketoacidosis. Therefore, we aimed to assess the prevalence of ketosis, ketonuria and ketoacidosis in critically ill diabetic patients treated in accordance with a liberal glycemic control protocol.

Methods

We performed a prospective observational cohort study of 60 critically ill diabetic patients with blood and/or urine ketone bodies tested in ICU. All patients were treated according to a liberal glucose protocol targeting a blood glucose level (BGL) between 10 and 14 mmol/l in a single tertiary intensive care unit in Australia. We measured quantitative bedside blood 3-beta-hydroxybutyrate (β-OHB) and semi-quantitative urine ketones on ICU admission and daily during ICU stay, for a maximum of 10 consecutive days.

Results

Median blood β-OHB level on admission was 0.3 (0.1, 0.8) mmol/l. Ketoacidosis was rare (3 %), but some level of ketosis (β-OHB ≥0.6 mmol/l) was found in 38 patients (63 %) early during their ICU stay. However, there was no significant difference in prevalence or severity of ketonemia and ketonuria among patients with BGL above (permissive hyperglycemia) or below 10 mmol/l. On multivariable linear regression analysis there was no association between blood ketone levels and BGL, HbA1c, lactate levels, hematocrit, catecholamine infusion or APACHE III score. In contrast, blood ketone levels tended to be higher after cardiopulmonary bypass surgery (P = 0.06).

Conclusions

Liberal glycemic control in critically ill diabetic patients does not appear to be associated with a high prevalence of ketoacidosis or ketonemia. Moreover, ketosis is typically present on admission and resolves rapidly. Finally, cardiopulmonary bypass surgery may be an important trigger of ketone body production.

Trial registration

Australian New Zealand Clinical Trials Registry (ACTRN12615000216516; trial registration date 5 March 2015).

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1462-7) contains supplementary material, which is available to authorized users.

Lipid Emulsion Attenuates Acetylcholine-Induced Relaxation in Isolated Rat Aorta

We investigated the effect of Lipofundin MCT/LCT and Intralipid on acetylcholine-induced nitric oxide- (NO-) mediated relaxation in rat aorta to determine which lipid emulsion (LE) is more potent in terms of inhibition of NO-induced relaxation. Dose-response curves of responses induced by acetylcholine, the calcium ionophore A23187, and sodium nitroprusside were generated using isolated rat aorta with or without LE. The effect of Lipofundin MCT/LCT on acetylcholine-induced endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells (HUVECs) was investigated using western blotting. Lipofundin MCT/LCT (0.1 and 0.2%) attenuated acetylcholine-induced relaxation in endothelium-intact aorta with or without tiron, whereas 0.2% Intralipid only inhibited relaxation. Lipofundin MCT/LCT inhibited relaxation induced by the calcium ionophore A23187 and sodium nitroprusside in endothelium-intact aorta, but Lipofundin MCT/LCT had no effect on sodium nitroprusside-induced relaxation in the endothelium-denuded aorta. Combined pretreatment with l-arginine plus Lipofundin MCT/LCT increased acetylcholine-induced maximal relaxation in endothelium-intact aorta compared with Lipofundin MCT/LCT alone. l-Arginine attenuated Lipofundin MCT/LCT-mediated inhibition of acetylcholine-induced eNOS phosphorylation in HUVECs. Taken together, Lipofundin MCT/LCT attenuated acetylcholine-induced NO-mediated relaxation via an inhibitory effect on the endothelium including eNOS, which is proximal to activation of guanylyl cyclase.

Lipid emulsions in parenteral nutrition: current applications and future developments

INTRODUCTION

A parenteral lipid emulsion (LE), used as a key source of energy, essential fatty acids (FAs), and fat-soluble vitamins, is an integral part of a parenteral nutrition (PN) regimen. The conventional LEs, such as soybean oil (SO)-based emulsions, have caused concerns about the potential adverse effects involving oxidative stress, inflammation, and immune response probably because of undesirable FA composition.

AREAS COVERED

Recently, alternative LEs, optimizing the FA composition with partial substitution of SO with medium-chain triglyceride (MCT), olive oil (OO), and fish oil (FO), have been developed and applied in clinical practice. This review summarizes the characteristics and beneficial clinical effects of alternative parenteral LEs in critically ill, pediatric, and long-term PN patients.

EXPERT OPINION

More clinical data from sufficiently high-powered studies are required to characterize the integral biological properties of alternative LEs for further selection to fit individual needs and disease characteristics. Simultaneously, potential lipid sources with desirable FA compositions and biological properties should be selected to develop new therapeutic LEs. As supplements to current parenteral lipids, the new LEs with different therapeutic effects are expected to fit specified subpopulations of patients with different diseases. Great efforts should be devoted to the development of parenteral LEs.

Protein sparing during general anesthesia with a propofol solution containing medium-chain triglycerides for gastrectomy: comparison with sevoflurane anesthesia

PURPOSE

Despite the importance of the inhibition of catabolic response to surgery, the effects of different anesthetic techniques on the catabolic response in surgical patients are controversial. This study compared the endocrine-metabolic responses and protein catabolism during gastrectomy in patients who received either sevoflurane or propofol anesthesia with remifentanil.

METHODS

Thirty-seven patients (American Society of Anesthesiologists status I-III) aged 20-79 years undergoing elective gastrectomy were randomly assigned to receive sevoflurane anesthesia with remifentanil (n = 19) or intravenous propofol anesthesia (Propofol-Lipuro(®) 1 %; B. Braun, Melshungen AG, Germany) with remifentanil (n = 18). Urine samples were collected every 1 h after skin incision (0 h) and the urinary 3-methylhistidine:creatinine ratio (3-MH/Cr ratio) was used as a marker of protein catabolism. Respiratory quotient was measured during a 1 h period following skin incision.

RESULTS

The 3-MH/Cr ratio significantly increased at 1-2 and 2-3 h compared to 0 and 0-1 h in both groups, but the propofol group exhibited a lower 3-MH/Cr ratio (nmol/μmol) than the sevoflurane group at 1-2 h (15.7 vs. 18.2, P = 0.012) and 2-3 h (15.9 vs. 18.1, P = 0.025). A difference was observed in the respiratory quotient between the sevoflurane and propofol groups (0.726 vs. 0.707, P = 0.003).

CONCLUSION

A lower 3-MH/Cr ratio and a lower respiratory quotient during propofol anesthesia, compared to those exhibited during sevoflurane anesthesia, suggest that protein sparing probably occurs through the utilization of medium-chain triglycerides contained in the fat emulsion of propofol solution as a fuel source.

The effect of FABP2 promoter haplotype on response to a diet with medium-chain triacylglycerols

The fatty-acid-binding protein-2 (FABP2) gene has been proposed as a candidate gene for diabetes because the encoded protein is involved in fatty acid absorption and therefore may affect insulin sensitivity and glucose metabolism. The rare haplotype (B) of its promoter was shown to be associated with a lower risk for type 2 diabetes. The aim of this study was to investigate whether a polymorphism in the FABP2 promoter does affect the metabolic response to either an medium-chain triacylglycerol (MCT) or an long-chain triacylglycerol (LCT) diet, which were suggested to differ in transport mechanisms, in affinity to FABP2, in activating transcription factors binding to the FABP2 promoter and in their effects on insulin sensitivity. We studied 82 healthy male subjects varying in the FABP2 promoter (42 homozygous for common haplotype (A), 40 homozygous for the rare haplotype (B)) in an interventional study with either an MCT or LCT diet over 2 weeks to examine gene-nutrient interaction. The saturation grade of MCT was adjusted to that of the LCT fat. We determined glucose, insulin, triacylglycerols (TGs), chylomicron triacylglycerols and cholesterol before and after a standardised mixed meal before and after the intervention. HDL cholesterol increased in all groups, which was most pronounced in subjects homozygous for the common promoter haplotype A who received MCT diet (P = 0.001), but not significant in homozygous rare haplotype B subjects who received MCT fat. Subjects homozygous for FABP2 haplotype A showed a significant decrease in fasting and postprandial glucose (P = 0.01, 0.04, respectively) and a decrease in insulin resistance (HOMA-IR, P = 0.04) during LCT diet. After correction for multiple testing, those effects did not remain significant. Fasting and postprandial triacylglycerols, LDL cholesterol, chylomicron TGs and cholesterol were not affected by genotype or diet. MCT diet increased HDL cholesterol dependent on the FABP2 promoter haplotype. The effects of the promoter haplotype B could be mediated by PPARγ, which is upregulated by medium-chain fatty acids.

Lipid emulsions in parenteral nutrition of intensive care patients: current thinking and future directions

Background

Energy deficit is a common and serious problem in intensive care units and is associated with increased rates of complications, length of stay, and mortality. Parenteral nutrition (PN), either alone or in combination with enteral nutrition, can improve nutrient delivery to critically ill patients. Lipids provide a key source of calories within PN formulations, preventing or correcting energy deficits and improving outcomes.

Discussion

In this article, we review the role of parenteral lipid emulsions (LEs) in the management of critically ill patients and highlight important biologic activities associated with lipids. Soybean-oil-based LEs with high contents of polyunsaturated fatty acids (PUFA) were the first widely used formulations in the intensive care setting. However, they may be associated with increased rates of infection and lipid peroxidation, which can exacerbate oxidative stress. More recently developed parenteral LEs employ partial substitution of soybean oil with oils providing medium-chain triglycerides, ω-9 monounsaturated fatty acids or ω-3 PUFA. Many of these LEs have demonstrated reduced effects on oxidative stress, immune responses, and inflammation. However, the effects of these LEs on clinical outcomes have not been extensively evaluated.

Conclusions

Ongoing research using adequately designed and well-controlled studies that characterize the biologic properties of LEs should assist clinicians in selecting LEs within the critical care setting. Prescription of PN containing LEs should be based on available clinical data, while considering the individual patient’s physiologic profile and therapeutic requirements.

Lipid emulsions - Guidelines on Parenteral Nutrition, Chapter 6

The infusion of lipid emulsions allows a high energy supply, facilitates the prevention of high glucose infusion rates and is indispensable for the supply with essential fatty acids. The administration of lipid emulsions is recommended within ≤7 days after starting PN (parenteral nutrition) to avoid deficiency of essential fatty acids. Low-fat PN with a high glucose intake increases the risk of hyperglycaemia. In parenterally fed patients with a tendency to hyperglycaemia, an increase in the lipid-glucose ratio should be considered. In critically ill patients the glucose infusion should not exceed 50% of energy intake. The use of lipid emulsions with a low phospholipid/triglyceride ratio is recommended and should be provided with the usual PN to prevent depletion of essential fatty acids, lower the risk of hyperglycaemia, and prevent hepatic steatosis. Biologically active vitamin E (α-tocopherol) should continuously be administered along with lipid emulsions to reduce lipid peroxidation. Parenteral lipids should provide about 25–40% of the parenteral non-protein energy supply. In certain situations (i.e. critically ill, respiratory insufficiency) a lipid intake of up to 50 or 60% of non-protein energy may be reasonable. The recommended daily dose for parenteral lipids in adults is 0.7–1.3 g triglycerides/kg body weight. Serum triglyceride concentrations should be monitored regularly with dosage reduction at levels >400 mg/dl (>4.6 mmol/l) and interruption of lipid infusion at levels >1000 mg/dl (>11.4 mmol/l). There is little evidence at this time that the choice of different available lipid emulsions affects clinical endpoints.

ESPEN Guidelines on Parenteral Nutrition: intensive care

Nutritional support in the intensive care setting represents a challenge but it is fortunate that its delivery and monitoring can be followed closely. Enteral feeding guidelines have shown the evidence in favor of early delivery and the efficacy of use of the gastrointestinal tract. Parenteral nutrition (PN) represents an alternative or additional approach when other routes are not succeeding (not necessarily having failed completely) or when it is not possible or would be unsafe to use other routes. The main goal of PN is to deliver a nutrient mixture closely related to requirements safely and to avoid complications. This nutritional approach has been a subject of debate over the past decades. PN carries the considerable risk of overfeeding which can be as deleterious as underfeeding. Therefore the authors will present not only the evidence available regarding the indications for PN, its implementation, the energy required, its possible complementary use with enteral nutrition, but also the relative importance of the macro- and micronutrients in the formula proposed for the critically ill patient. Data on long-term survival (expressed as 6 month survival) will also be considered a relevant outcome measure. Since there is a wide range of interpretations regarding the content of PN and great diversity in its practice, our guidance will necessarily reflect these different views. The papers available are very heterogeneous in quality and methodology (amount of calories, nutrients, proportion of nutrients, patients, etc.) and the different meta-analyses have not always taken this into account. Use of exclusive PN or complementary PN can lead to confusion, calorie targets are rarely achieved, and different nutrients continue to be used in different proportions. The present guidelines are the result of the analysis of the available literature, and acknowledging these limitations, our recommendations are intentionally largely expressed as expert opinions.

Immune modulation by parenteral lipid emulsions

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

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.

Effects of medium-chain fatty acids and oleic acid on blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities

BACKGROUND

Dietary medium-chain fatty acids (MCFAs) are of nutritional interest because they are more easily absorbed from dietary medium-chain triacylglycerols (MCTs) than are long-chain fatty acids from, for example, vegetable oils. It has generally been claimed that MCFAs do not increase plasma cholesterol, although this claim is poorly documented.

OBJECTIVE

We compared the effects of a diet rich in either MCFAs or oleic acid on fasting blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities in healthy men.

DESIGN

In a study with a double-blind, randomized, crossover design, 17 healthy young men replaced part of their habitual dietary fat intake with 70 g MCTs (66% 8:0 and 34% 10:0) or high-oleic sunflower oil (89.4% 18:1). Each intervention period lasted 21 d, and the 2 periods were separated by a washout period of 2 wk. Blood samples were taken before and after the intervention periods.

RESULTS

Compared with the intake of high-oleic sunflower oil, MCT intake resulted in 11% higher plasma total cholesterol (P = 0.0005), 12% higher LDL cholesterol (P = 0.0001), 32% higher VLDL cholesterol (P = 0.080), a 12% higher ratio of LDL to HDL cholesterol (P = 0.002), 22% higher plasma total triacylglycerol (P = 0.0361), and higher plasma glucose (P = 0.033). Plasma HDL-cholesterol and insulin concentrations and activities of cholesterol ester transfer protein and phospholipid transfer protein did not differ significantly between the diets.

CONCLUSIONS

Compared with fat high in oleic acid, MCT fat unfavorably affected lipid profiles in healthy young men by increasing plasma LDL cholesterol and triacylglycerol. No changes in the activities of phospholipid transfer protein and cholesterol ester transfer protein were evident.

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.

Long-chain versus medium-chain lipids in acute pancreatitis complicated by acute respiratory distress syndrome: effects on pulmonary hemodynamics and gas exchange

BACKGROUND AND AIMS

In order to assess the effects of fat emulsions in patients with acute pancreatitis and acute respiratory distress syndrome (ARDS) before the pancreatic injury was complicated by infection, pulmonary hemodynamics and gas exchange were investigated during the administration of long-(LCTs) or medium-chain triacylglycerols (MCTs).

METHODS

This prospective trial included nine patients with acute pancreatitis and ARDS; each patient was used as his/her own control. In all cases, the needle aspiration culture of the pancreas was negative. Fat emulsion provided 50% of the energy expenditure. The patients were infused, in random order, with pure LCTs and a 1:1 mixture of LCTs/MCTs on days 1 and 2, over an 8 h period.

RESULTS

LCT infusion increased the mean pulmonary artery pressure (MPAP) from 28+/-5 to 35+/-3 mmHg, pulmonary venous admixture (Qva/Qt) from 26+/-5% to 36+/-5% and decreased arterial PO2(PaO2)/fractional inspired oxygen (FIO2) from 210+/-20 to 170+/-20 (P<0.05). The infusion of LCT/MCT 1:1 emulsions increased oxygen consumption (VO2) from 340+/-10 to 398+/-15 ml/min, cardiac output (CO) from 8.8+/-0.2 to 9.5+/-0.5 L/min and CO2 production (VCO2) from 247+/-12 to 282+/-14 mL/min (P<0.05).

CONCLUSION

LCT/MCT 1:1 mixtures are recommended in cases of acute pancreatitis and ARDS, even though infusion over a short period increases the metabolic demand.

Fish oil-supplemented parenteral diets normalize splanchnic blood flow and improve killing of translocated bacteria in a low-dose endotoxin rat model

OBJECTIVE

Intestinal ischemia decreases barrier function of the gut and enhances translocation of bacteria and toxins. Several studies indicate that fish oil can modulate prostaglandin formation and thus, regional blood flow and immune function. This study was performed to determine the effects of parenteral diets with omega-3 fatty acids on microcirculation and barrier function of the gut.0

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University laboratory.

SUBJECTS

A total of 64 male Sprague-Dawley CD rats.

INTERVENTIONS AND MEASUREMENTS

For 48 hrs, eight groups of eight rats each received total parenteral nutrition with four different types of lipids. The source of fat in group L was soybean oil only and in group L-M a mixture of soybean oil and medium-chain triglycerides. In groups FO-20 and FO-40, 20% or 40%, respectively, of the soybean oil in group L-M was replaced by fish oil. The other four groups received an additional continuous infusion of endotoxin (0.1 mg/100 g body weight per day) for the last 24 hrs. Blood flow was measured with microspheres, and translocation was determined by microbiological methods and instillation of radioactive-marked bacteria into the gut.

MAIN RESULTS

In the animals without fish oil, the endotoxin application reduced the blood flow to the intestine approximately 25%. Animals with fish oil in their diets showed normal values. Translocation of gut bacteria was increased significantly in all endotoxin groups. However, less-viable bacteria could be detected in the animals with fish oil diets in their mesenteric lymph nodes and livers.

CONCLUSIONS

In this model, diets enriched with fish oil abolish the endotoxin-induced decrease of nutritive blood flow to the gut and ameliorate the bactericidal defense of the splanchnic region. The lower count of viable bacteria in the fish oil groups is more related to an improved killing of translocated bacteria than a reduction of the translocation rate.

With medium-chain triglycerides, higher and faster oxygen radical production by stimulated polymorphonuclear leukocytes occurs

BACKGROUND

Parenteral lipid emulsions are suspected of suppressing the immune function. However, study results are contradictory and mainly concern the conventional long-chain triglyceride emulsions.

METHODS

Polymorphonuclear leukocytes were preincubated with parenteral lipid emulsions. The influence of the lipid emulsions on the production of oxygen radicals by these stimulated leukocytes was studied by measuring chemiluminescence. Three different parenteral lipid emulsions were tested: long-chain triglycerides, a physical mixture of medium- and long-chain triglycerides, and structured triglycerides. Structured triglycerides consist of triglycerides where the medium- and long-chain fatty acids are attached to the same glycerol molecule.

RESULTS

Stimulated polymorphonuclear leukocytes preincubated with the physical mixture of medium- and long-chain triglycerides showed higher levels of oxygen radicals (p < .005) and faster production of oxygen radicals (p < .005) compared with polymorphonuclear leukocytes preincubated with long-chain triglycerides or structured triglycerides. Additional studies indicated that differences in results of various lipid emulsions were not caused by differences in emulsifier. The overall production of oxygen radicals was significantly lower after preincubation with the three lipid emulsions compared with controls without lipid emulsion.

CONCLUSIONS

A physical mixture of medium- and long-chain triglycerides induced faster production of oxygen radicals, resulting in higher levels of oxygen radicals, compared with long-chain triglycerides or structured triglycerides. This can be detrimental in cases where oxygen radicals play either a pathogenic role or a beneficial one, such as when rapid phagocytosis and killing of bacteria is needed. The observed lower production of oxygen radicals by polymorphonuclear leukocytes in the presence of parenteral lipid emulsions may result in immunosuppression by these lipids.

Medium-chain triglycerides inhibit growth of Malassezia: implications for prevention of systemic infection

OBJECTIVE

Lipophilic Malassezia species may induce catheter-associated sepsis in newborns and immunocompromised patients receiving parenteral lipids. Therefore, we tested whether M. furfur and six other Malassezia species can use commercially available infusions as a lipid source.

DESIGN

Prospective in vitro study.

SETTING

Research laboratory in a university hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

With the exception of M. restricta, all Malassezia species grow on lipid infusions. There are no substantial differences among the different brands. The most rapid growth is shown by M. furfur, which grows better on agar containing a 20% rather than a 10% lipid infusion. Growth of M. furdur and M. sympodialis can be reduced by infusions containing medium-chain triglycerides. Incubated in triglycerides, M. furfur is strongly suppressed by 50% medium-chain triglycerides and M. sympodialis by 8% medium-chain triglycerides. When medium-chain free fatty acids are added to triglycerides, both species can be suppressed by about 1% free fatty acids.

CONCLUSION

Medium-chain triglycerides and medium-chain free fatty acids are toxic for Malassezia species. Commercially available infusions containing medium-chain triglycerides might be used to prevent systemic Malassezia infections.

Leucine metabolism in preterm infants receiving parenteral nutrition with medium-chain compared with long-chain triacylglycerol emulsions

BACKGROUND

Although medium-chain triacylglycerols (MCTs) may be utilized more efficiently than long-chain triacylglycerols (LCTs), their effect on protein metabolism remains controversial.

OBJECTIVE

The aim of the study was to compare the effects of mixed MCT-LCT and pure LCT emulsions on leucine metabolism in preterm infants.

DESIGN

Fourteen preterm [gestational age: 30+/-1 wk; birth weight: 1409+/-78 g (x +/- SE)] neonates were randomly assigned to receive, from the first day of life, either a 50:50 MCT-LCT (mixed MCT group; n = 7) or an LCT (LCT group; n = 7) lipid emulsion as part of an isonitrogenous, isoenergetic total parenteral nutrition program. On the fourth day, infants received intravenous feeding providing 3 g lipid, 15 g glucose, and 3 g amino acids kg(-1) x d(-1) and underwent 1) indirect calorimetry and 2) a primed, 2-h infusion of H13CO3Na to assess the recovery of 13C in breath, immediately followed by 3) a 3-h infusion of L-[1-13C]leucine.

RESULTS

The respiratory quotient tended to be slightly but not significantly higher in the mixed MCT than in the LCT group (0.96+/-0.06 compared with 0.93+/-0.03). We did not detect a significant difference between the mixed MCT and LCT groups with regard to release of leucine from protein breakdown (B; 309+/-40 compared with 257+/-46 micromol x kg(-1) x h(-1)) and nonoxidative leucine disposal (NOLD; 296+/-36 compared with 285+/-49 micromol x kg(-1) x h(-1)). In contrast, leucine oxidation was greater in the mixed MCT than in the LCT group (113+/-10 compared with 67+/-10 micromol x kg(-1) x h(-1); P = 0.007). Net leucine balance (NOLD - B) was less positive in the mixed MCT than in the LCT group (-14+/-9 compared with 28+/-10 micromol x kg(-1) x h(-1); P = 0.011).

CONCLUSION

Mixed MCTs may not be as effective as LCT-containing emulsions in promoting protein accretion in parenterally fed preterm neonates.

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.

A 10-year survey of nutritional support in a surgical ICU: 1986-1995

Total parenteral nutrition (TPN) has long been considered the optimal nutrition technique in critically ill patients, but recently the use of enteral nutrition (EN) has increased. This study describes the evolution of the different nutritional support techniques in a surgical intensive care unit (ICU) in a university hospital, through (1) a global survey over 10 y assessing the evolution of the use of EN and TPN, and (2) a prospective study performed over 6 mo. Severity of illness and diagnostic categories were stable (n = 11,539 patients). From 1986 to 1990, the proportion of TPN administered increased from 10-25% of ICU days, decreasing to 10% thereafter. EN was used in about 5% of ICU days in 1986, and had increased to 30% of total ICU treatment days in 1995. The proportion of nutrients actually delivered to the patients was 75% with EN and 88% with TPN. Major changes in nutritional support have been observed since 1986. The frequency of nutritional support provided in general has increased to 40% of ICU treatment days. TPN has been largely overtaken by EN, with the risk of insufficient energy delivery, related to the difficulties of EN in the critically ill. These results reinforce the importance of continuous quality control by daily assessment of nutrient supply.

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.

Effects of chemically defined structured lipid emulsions on reticuloendothelial system function and morphology of liver and lung in a continuous low-dose endotoxin rat model

BACKGROUND

This study was undertaken to determine the effect of chemically defined structured lipids on nonspecific host defense and on histologic patterns of liver and lungs compared with a physical mixture of long-chain triglycerides and medium-chain triglycerides in a continuous low-dose endotoxin rat model.

METHODS

Forty male Sprague-Dawley rats, divided into four feeding groups (structured lipids, structured lipids+endotoxin, physical mixture, physical mixture+endotoxin), received total parenteral nutrition for 48 hours. During the first part of the study, 24 animals were given an injection of live Escherichia coli labeled with radioactive iron (59Fe) to investigate the function of the reticuloendothelial system. During the second part of the study, the liver and lungs of 16 animals were histologically examined using light and electron microscopy.

RESULTS

Despite the similar values in the control groups, the animals receiving structured lipids+endotoxin sequestered a significantly greater percentage of bacteria in the liver and spleen (p < or = .01) and a significantly lesser percentage in the lung (p < or = .05) compared with the animals given physical mixture+endotoxin as part of their diet. Moreover, rats in the physical mixture+endotoxin group showed a microscopically evaluated higher fatty infiltration in the liver than did the structured lipids+endotoxin group.

CONCLUSIONS

The results of this study indicate that chemically defined structured lipids reduce fatty infiltration of the liver compared with a physical mixture of the same compounds in an animal model of metabolic stress. They were accompanied by a better function of the reticuloendothelial system and a lesser bacterial sequestration in the lungs.

[Effect of postoperative complications on nutritional status: therapeutic consequences]

The occurrence of a postoperative complication represents an additional stress factor for patients and leads in many cases rapidly to a malnutrition status. Thus a nutritional support is required as soon as the foreseeable duration of starvation has a longer duration than one week. Considering its lower risk of septic complications and lower cost, enteral feeding should be initiated as soon as possible. Appraisal of caloric needs with standard formulas often leads to inappropriate nutritional management. Therefore the requirements should be assessed by indirect calorimetry if available. Nutritional support is a part of the management of a postoperative septic patient. It must be initiated when initial phase of haemodynamic instability is amended. Branched chain amino acids, medium chain triglycerides and other specific nutrients have failed to demonstrate a real clinical beneficial effect. In case of acute respiratory failure, nutritional support must be cautious with regard to caloric load, as carbohydrates may increase CO2 production and lipids may worsen hypoxaemia. In case of postoperative acute renal failure, nutritional management is facilitated by continuous haemofiltration techniques allowing an unlimited nutrient intake. Solutions containing only essential amino acids are not recommended. During severe acute pancreatitis, enteral feeding is indicated when ileus does not permit the use of the intestinal tract. Jejunal access must be preferred to stomach or duodenum. Lipid emulsions can be used safely if serum triglyceride concentrations remain below 4 g.L-1 during infusion and below 2 g.L-1 between infusions.