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

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.

Comparison of catheter-related bloodstream infection rates in pediatric patients receiving parenteral nutrition with soybean oil-based intravenous fat emulsion versus a mixed oil fat emulsion

STUDY OBJECTIVE

To compare rates of catheter-related bloodstream infections (CR-BSI) in pediatric patients who received parenteral nutrition (PN) with either soybean oil-based intravenous fat emulsion (SO-IFE) or mixed oil-IFE (MO-IFE). We hypothesized that the use of MO-IFE would be independently associated with reduced infection rates compared with SO-IFE.

DESIGN

Retrospective cohort study.

SETTING

Tertiary referral children's hospital and its associated gastrointestinal rehabilitation clinic (01 January, 2015-31 July, 2019).

PATIENTS

Days of IFE exposure were counted for patients aged <18 years on IFE initiated during the review period, who had a central venous catheter (CVC) placed for PN administration, received IFE at least three times weekly, and for at least 7 days.

MEASUREMENTS

The primary outcome included total and categorical CR-BSI rates expressed as the average with standard error (SE) number of infections per 1000 fat emulsion days. The following categories were specified: Candida albicans, non-albicans Candida spp., coagulase-negative Staphylococcus (CoNS), Enterobacterales, methicillin-resistant S. aureus, methicillin-susceptible S. aureus, and Pseudomonadales. Average infection rate comparisons were quantified as incidence rate ratios (IRR) using generalized linear mixed modeling with a Poisson distribution.

MAIN RESULTS

Seven hundred and forty-three SO-IFE and 450 MO-IFE exposures were reviewed from 1131 patients, totaling 37,599 and 19,796 days of therapy, respectively. From those found significantly different, the average rate of infections with CoNS was 3.58 (SE 0.5)/1000 days of SO-IFE and 1.39 (SE 0.45)/1000 days of MO-IFE (IRR [95% confidence interval, CI]: 0.27 [0.16-0.46]; p < 0.01). Total average rates of infection were 7.33 (SE 0.76)/1000 days of SO-IFE and 4.52 (SE 0.75)/1000 days of MO-IFE (IRR [95% CI]: 0.60 [0.44-0.81]; p < 0.01). Other factors associated with higher infection rates include female gender, neonatal age, and inpatient-only IFE exposure.

CONCLUSIONS

Receipt of MO-IFE was associated with lower rates of CoNS and total CR-BSIs compared with SO-IFE in pediatric patients. These findings could have major implications on IFE selection for pediatric patients receiving PN.

Omega-6 sparing effects of parenteral lipid emulsions-an updated systematic review and meta-analysis on clinical outcomes in critically ill patients

BACKGROUND

Parenteral lipid emulsions in critical care are traditionally based on soybean oil (SO) and rich in pro-inflammatory omega-6 fatty acids (FAs). Parenteral nutrition (PN) strategies with the aim of reducing omega-6 FAs may potentially decrease the morbidity and mortality in critically ill patients.

METHODS

A systematic search of MEDLINE, EMBASE, CINAHL and CENTRAL was conducted to identify all randomized controlled trials in critically ill patients published from inception to June 2021, which investigated clinical omega-6 sparing effects. Two independent reviewers extracted bias risk, treatment details, patient characteristics and clinical outcomes. Random effect meta-analysis was performed.

RESULTS

1054 studies were identified in our electronic search, 136 trials were assessed for eligibility and 26 trials with 1733 critically ill patients were included. The median methodologic score was 9 out of 14 points (95% confidence interval [CI] 7, 10). Omega-6 FA sparing PN in comparison with traditional lipid emulsions did not decrease overall mortality (20 studies; risk ratio [RR] 0.91; 95% CI 0.76, 1.10; p = 0.34) but hospital length of stay was substantially reduced (6 studies; weighted mean difference [WMD] - 6.88; 95% CI - 11.27, - 2.49; p = 0.002). Among the different lipid emulsions, fish oil (FO) containing PN reduced the length of intensive care (8 studies; WMD - 3.53; 95% CI - 6.16, - 0.90; p = 0.009) and rate of infectious complications (4 studies; RR 0.65; 95% CI 0.44, 0.95; p = 0.03). When FO was administered as a stand-alone medication outside PN, potential mortality benefits were observed compared to standard care.

CONCLUSION

Overall, these findings highlight distinctive omega-6 sparing effects attributed to PN. Among the different lipid emulsions, FO in combination with PN or as a stand-alone treatment may have the greatest clinical impact. Trial registration PROSPERO international prospective database of systematic reviews (CRD42021259238).

Comparison of Biochemical and Pathological Parameters and Parenteral Nutrition of ICU Patients Under Supervision of Dietitians and Surgeons

Background: Nutrient imbalance can frequently occur in patients with indications for parenteral nutrition (PN) after gastrointestinal surgery. This study aimed to compare the recommendations of a surgeon to those of a dietitian in the field of parenteral nutrition.

Methods: This study was performed on 256 patients undergoing gastrointestinal surgery who received PN, which included 120 patients who received PN based on recommendations of the surgeons and 136 patients who were referred to receive PN under the supervision of a dietitian in Razi Hospital in Rasht, Iran. Data on PN and clinical outcomes of the patients were collected.

Results: Patients under the supervision of dietitians received higher vitamin B complex and lipids and lower vitamin A and vitamin E than the surgeon-supervised patients (all P < 0.001). In the group receiving PN under the supervision of a surgeon, the level of blood glucose (207 vs. 182, P < 0.01), sodium (138 vs. 136, P = 0.01), potassium (3.97 vs. 3.53, P < 0.01), and white blood cell count (9.83 vs. 9.28, P < 0.01) increased significantly at the end of the PN compared to baseline. In the group receiving PN under the supervision of a dietician, the level of serum Cr (1.23 vs. 1.32, P = 0.04), Mg (2.07 vs. 1.84, P < 0.01), and pH (7.45 vs. 7.5, P = 0.03) significantly improved after receiving parenteral nutrition compared to baseline.

Conclusion: The amounts of nutrients recommended for PN by the surgeon and dietitian were different. Implementation of dietitian recommendations in critically ill patients under PN can improve patients' clinical parameters.

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.

Clinical Nutrition in Critical Care Medicine - Guideline of the German Society for Nutritional Medicine (DGEM)

PURPOSE

Enteral and parenteral nutrition of adult critically ill patients varies in terms of the route of nutrient delivery, the amount and composition of macro- and micronutrients, and the choice of specific, immune-modulating substrates. Variations of clinical nutrition may affect clinical outcomes. The present guideline provides clinicians with updated consensus-based recommendations for clinical nutrition in adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function.

METHODS

The former guidelines of the German Society for Nutritional Medicine (DGEM) were updated according to the current instructions of the Association of the Scientific Medical Societies in Germany (AWMF) valid for a S2k-guideline. According to the S2k-guideline classification, no systematic review of the available evidence was required to make recommendations, which, therefore, do not state evidence- or recommendation grades. Nevertheless, we considered and commented the evidence from randomized-controlled trials, meta-analyses and observational studies with adequate sample size and high methodological quality (until May 2018) as well as from currently valid guidelines of other societies. The liability of each recommendation was described linguistically. Each recommendation was finally validated and consented through a Delphi process.

RESULTS

In the introduction the guideline describes a) the pathophysiological consequences of critical illness possibly affecting metabolism and nutrition of critically ill patients, b) potential definitions for different disease phases during the course of illness, and c) methodological shortcomings of clinical trials on nutrition. Then, we make 69 consented recommendations for essential, practice-relevant elements of clinical nutrition in critically ill patients. Among others, recommendations include the assessment of nutrition status, the indication for clinical nutrition, the timing and route of nutrient delivery, and the amount and composition of substrates (macro- and micronutrients); furthermore, we discuss distinctive aspects of nutrition therapy in obese critically ill patients and those treated with extracorporeal support devices.

CONCLUSION

The current guideline provides clinicians with up-to-date recommendations for enteral and parenteral nutrition of adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. The period of validity of the guideline is approximately fixed at five years (2018-2023).

Intravenous Fat Emulsion Formulations for the Adult and Pediatric Patient: Understanding the Differences

Intravenous fat emulsions (IVFEs) provide essential fatty acids (EFAs) and are a dense source of energy in parenteral nutrition (PN). Parenterally administered lipid was introduced in the 17th century but plagued with side effects. The formulation of IVFEs later on made it a relatively safe component for administration to patients. Many ingredients are common to all IVFEs, yet the oil source(s) and its (their) percentage(s) makes them different from each other. The oil used dictates how IVFEs are metabolized and cleared from the body. The fatty acids (FAs) present in each type of oil provide unique beneficial and detrimental properties. This review provides an overview of IVFEs and discusses factors that would help clinicians choose the optimal product for their patients.

Lipid emulsions for parenteral nutrition in critical illness

Critical illness is a life-threatening multisystem process that can result in significant morbidity and mortality. In most patients, critical illness is preceded by a physiological deterioration, characterized by a catabolic state and intense metabolic changes, resulting in malnutrition and impaired immune functions. In this context, parenteral lipid emulsions may modulate inflammatory and immune reactions, depending on their fatty acid composition. These effects appear to be based on complex modifications in the composition and structure of cell membranes, through eicosanoid and cytokine synthesis and by modulation of gene expression. The pathophysiological mechanisms underlying these fatty acid-induced immune function alterations in critical ill patients are however complex and partially understood. Indeed, despite a very abundant literature, experimental and clinical data remain contradictory. The optimization of lipid emulsion composition thus represents a major challenge for clinical medicine, to adequately modulate the inflammatory pathways. In the present review, we first address the metabolic response to aggression, the effects of parenteral lipid emulsions on inflammation and immunity, and finally the controversial place of these lipid emulsions during critical illness. The analysis furthermore highlights the pathophysiological mechanisms underlying the differential effects of lipid emulsions and their potential for improving the handling of critically ill patients.

Addition of lipids to parenteral nutrition does not cause fungal infections

Parenteral nutrition (PN) that includes lipid emulsion is considered to increase both bacterial and fungal central venous catheter-related bloodstream infections. This concept is based on several erroneous metrics: Reports in age-old literature at a time when preparing PN admixtures lacked stringent quality control, when its infusion, the techniques of insertion, maintenance of vascular access devices, and delivery systems were not well identified or enforced. Additionally, concepts of glucohomeostasis were different and higher glucose levels were accepted. We provide updated information with supporting literature to show that associating PN with lipids with an increase in bloodstream infections is not justified.

The effects of different IV fat emulsions on clinical outcomes in critically ill patients

OBJECTIVE

To examine the effects of different IV fat emulsions on clinical outcomes in critically ill patients.

DESIGN

Secondary analysis of data from a prospective multicenter study.

SETTING

An international sample of ICUs.

PATIENTS

Adult patients who were admitted to the ICU for more than 72 hours, were mechanically ventilated within 48 hours, received exclusive parenteral nutrition for more than or equal to 5 days, and did not change IV fat emulsion type during the data collection period.

INTERVENTIONS

Demographic and clinical data were collected for up to 12 days, until death, or discharge from the ICU, whichever came first. Clinical outcomes were recorded at 60 days following ICU admission.

MEASUREMENTS

Lipid-free, soybean, medium-chain triglyceride, olive, and fish oils in parenteral nutrition were compared using an adjusted Cox proportional hazard model to examine time to termination of mechanical ventilation alive, time to ICU discharge alive, and time to hospital discharge alive.

MAIN RESULTS

A total of 451 patients were included in this study: 70 (15.5%) in the lipid-free group, 223 (49.5%) in the soybean oil group, 65 (14.4%) in the medium-chain triglyceride group, 74 (16.4%) in the olive oil group, and 19 (4.9%) in the fish oil group. When compared with lipid-free parenteral nutrition, patients who received fish oil had a faster time to ICU discharge alive (hazard ratio, 1.84; 95% CI, 1.01-3.34; p = 0.05). When compared with soybean oil, patients who received olive oil or fish oil had a shorter time to termination of mechanical ventilation alive (hazard ratio, 1.43; 95% CI, 1.06-1.93; p = 0.02 and hazard ratio, 1.67; 95% CI, 1.00-2.81; p = 0.05, respectively) and a shorter time to ICU discharge alive (hazard ratio, 1.76; 95% CI, 1.30-2.39; p < 0.001 and hazard ratio, 2.40; 95% CI, 1.43-4.03; p = 0.001, respectively).

CONCLUSIONS

Use of alternative IV fat emulsions in parenteral nutrition, particularly olive and fish oil, was associated with improved clinical outcomes.

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.

Alternative lipid emulsions in the critically ill: a systematic review of the evidence

PURPOSE

Parenteral lipid emulsions (LEs) are commonly rich in long-chain triglycerides derived from soybean oil (SO). SO-containing emulsions may promote systemic inflammation and therefore may adversely affect clinical outcomes. We hypothesized that alternative oil-based LEs (SO-sparing strategies) may improve clinical outcomes in critically ill adult patients compared to products containing SO emulsion only. The purpose of this systematic review was to evaluate the effect of parenteral SO-sparing strategies on clinical outcomes in intensive care unit (ICU) patients.

METHODS

We searched computerized databases from 1980 to 2013. We included randomized controlled trials (RCTs) conducted in critically ill adult patients that evaluated SO-sparing strategies versus SO-based LEs in the context of parenteral nutrition.

RESULTS

A total of 12 RCTs met the inclusion criteria. When the results of these RCTs were statistically aggregated, SO-sparing strategies were associated with clinically important reductions in mortality (risk ratio, RR 0.83; 95 % confidence intervals, CI 0.62, 1.11; P = 0.20), in duration of ventilation (weighted mean difference, WMD -2.57; 95 % CI -5.51, 0.37; P = 0.09), and in ICU length of stay (LOS) (WMD -2.31; 95 % CI -5.28, 0.66; P = 0.13) but none of these differences were statistically significant. SO-sparing strategies had no effect on infectious complications (RR 1.13; 95 % CI 0.87, 1.46; P = 0.35).

CONCLUSION

Alternative oil-based LEs may be associated with clinically important reductions in mortality, duration of ventilation, and ICU LOS but lack of statistical precision precludes any clinical recommendations at this time. Further research is warranted to confirm these potential positive treatment effects.

[Guidelines for specialized nutritional and metabolic support in the critically-ill patient. Update. Consensus of the Spanish Society of Intensive Care Medicine and Coronary Units-Spanish Society of Parenteral and Enteral Nutrition (SEMICYUC-SENPE): macro-and micronutrient requirements]

Energy requirements are altered in critically-ill patients and are influenced by the clinical situation, treatment, and phase of the process. Therefore, the most appropriate method to calculate calorie intake is indirect calorimetry. In the absence of this technique, fixed calorie intake (between 25 and 35 kcal/kg/day) or predictive equations such as the Penn State formula can be used to obtain a more accurate evaluation of metabolic rate. Carbohydrate administration should be limited to a maximum of 4 g/kg/day and a minimum of 2g/kg/day. Plasma glycemia should be controlled to avoid hyperglycemia. Fat intake should be between 1 and 1.5 g/kg/day. The recommended protein intake is 1-1.5 g/kg/day but can vary according to the patient's clinical status. Particular attention should be paid to micronutrient intake. Consensus is lacking on micronutrient requirements. Some vitamins (A, B, C, E) are highly important in critically-ill patients, especially those undergoing continuous renal replacement techniques, patients with severe burns and alcoholics, although the specific requirements in each of these types of patient have not yet been established. Energy and protein intake in critically-ill patients is complex, since both clinical factors and the stage of the process must be taken into account. The first step is to calculate each patient's energy requirements and then proceed to distribute calorie intake among its three components: proteins, carbohydrates and fat. Micronutrient requirements must also be considered.

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.

Development of clinical application for a nutritional prescription support system for total parenteral/enteral nutrition

One of the important roles of pharmacists as members of a nutrition support team is nutritional prescription support. We developed a nutritional prescription support system (NPSS) that facilitates prescription support and analysis and evaluated its usefulness in nutritional therapy. An NPSS for prescription support and the management of patient information was created. With this NPSS, the nutritional status was assessed, and, on the basis of the results, such variables as the total energy expenditure were calculated. This system allows prescription support for parenteral nutrition (PN) therapy, enteral nutrition (EN) therapy, and the transition period between them. This system was used for 2 representative patients and evaluated. In a malnourished patient receiving oral warfarin, EN solutions were compared by means of the NPSS, and an appropriate EN solution was selected. In addition, the prothrombin time-international normalized ratio was monitored, and favorable results were obtained regarding the adjustment of the warfarin dose and nutritional management. In a patient with aspiration pneumonia, continuous nutritional management to EN from PN therapy was straightforwardly performed with the NPSS. This NPSS allows rapid, comprehensive nutritional management during the transition period to EN from PN therapy, despite these therapies being considered separately in conventional nutritional management. The NPSS is useful for simplifying prescription support and facilitating information sharing among members of a nutrition support team.

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.

Fish oil in critical illness

PURPOSE OF REVIEW

The aim of this review is to discuss recent advances in the role of n-3 lipids derived from fish oil in clinical nutrition in an intensive care setting.

RECENT FINDINGS

Fish oil supplies n-3 fatty acids which compete with arachidonic acid (n-6) for the conversion to lipid mediators, influence lipid-bound second messenger generation and dependent cellular functions, and are a source for resolvins necessary for the resolution of inflammation. Enteral nutrition with n-3 fatty acids improved ventilation time in patients with acute lung injury and in one study reduced mortality in septic patients. Using a high-dose short-term infusion of fish oil-based lipid emulsion, rapid immunologic changes and effects on the endotoxin-induced stress response may be achieved. Inclusion of n-3 fatty acids in parenteral nutrition improved immunologic parameters and length of stay in surgical patients.

SUMMARY

Inclusion of fish oil in nutrition may influence the immune response and clinical outcomes by balancing the negative effects of n-6 fatty acids. Application as a part of enteral immunonutrition in surgical or acute respiratory distress syndrome patients and in lipid emulsions in surgical patients has beneficial effects. In septic patients, data on enteral use are highly controversial. Prospective data from randomized trials, however, are lacking.

Immune function and leukocyte sequestration under the influence of parenteral lipid emulsions in healthy humans: a placebo-controlled crossover study

BACKGROUND

It remains unclear whether immune modulation by lipids contributes to the high risk of infectious complications that is associated with the use of parenteral nutrition. Although mixed long- and medium-chain triacylglycerol (LCT-MCT)-containing emulsions, but not pure LCT emulsions, activate neutrophils and impair crucial leukocyte functions in vitro, in vivo studies have failed to corroborate these findings.

OBJECTIVES

The present investigation was conducted to evaluate the effects of LCT and LCT-MCT on immune function in healthy humans and to assess whether the lack of in vivo effects results from sampling errors due to extravascular sequestration of activated neutrophils.

DESIGN

Saline, LCT-MCT, and LCT emulsions were administered intravenously for 4.5 h to 12 healthy volunteers in a randomized crossover design. Plasma triacylglycerol concentrations were clamped at a clinically relevant concentration of 3-5 mmol/L. Leukocyte population counts and neutrophil activation were assessed before and after infusion. Leukocyte sequestration was evaluated by monitoring the distribution of Technetium-99m-labeled autologous leukocytes during infusions.

RESULTS

Whereas LCT exerted no greater effects than did saline, LCT-MCT significantly decreased lymphocyte counts. However, no evidence for neutrophil activation was found with either lipid. Moreover, the clearance of radiolabeled leukocytes from the liver, spleen, and lungs was not altered by any lipid, which suggested that lipid emulsions do not induce leukocyte sequestration.

CONCLUSIONS

Short-term infusion of LCT-MCT (but not LCT) to healthy humans modulates leukocyte population counts but, in clear contrast with the in vitro situation, does not induce neutrophil activation. These disparate findings cannot be explained by MCT-induced leukocyte sequestration.

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.

Effect of different lipid emulsions on the immunological function in humans: a systematic review with meta-analysis

BACKGROUND & AIMS

Reports regarding the pro- or anti-inflammatory effects of lipid emulsion used in parenteral nutrition are conflicting. Aim was to assess the effect of different intravenous lipid emulsions on immunological function in humans.

METHODS

We performed a computerized bibliographic search, searched reference lists in trial reports, hand-searched journals and contacted experts in the field. Randomized clinical trials evaluating the immunological effects of different parenteral lipid emulsions were included. Three authors independently performed data extraction, statistical processes were performed by two experts. Immunological parameters were classified by two immunologists as marker of improved or worsened immune function. A meta-analysis with standardized effect size estimation was performed for the comparison between long-chain triglycerides vs. glucose or other fat emulsions.

RESULTS

Of 682 assessed studies, 120 compared the immunological effects of intravenously applied lipid emulsions. Of 30 randomized trials, 14 were included in the meta-analysis. None of the lipid regimens showed any clear effect on the evolution of the immunological status or mortality in humans. Length of hospital stay and stay in the intensive care unit could not be evaluated.

CONCLUSION

We found no evidence that lipid emulsions and in particular those containing long-chain triglycerides have an unfavorable effect on immune function.

Lipids in the nutritional support of the critically ill patients

PURPOSE OF REVIEW

This review reports recent findings on lipid use in artificial nutrition in patients with acute respiratory failure or severe sepsis or undergoing major surgery. It examines current knowledge of fatty acid safety, biologic effects, and the impact on patients' morbidity and mortality. The newly emerging area of genotypic influence and timing of immunonutrition is also discussed.

RECENT FINDINGS

In acute respiratory distress syndrome, the debate concerning the use of long-chain fatty acids as opposed to physical mixtures of medium- and long-chain fatty acids, specifically regarding their effects on gas exchange and pulmonary hemodynamics, still remains unresolved. By contrast, providing fish oil fatty acids (mainly eicosapentaenoic and docosahexaenoic acids) and/or gamma-linolenic acid, seems to decrease harmful excessive inflammatory/immune activation and to improve clinical outcome. Similar effects, although not conclusively demonstrated, have been reported for n-3 fatty acid-enriched lipid emulsions in patients with sepsis. Few recent studies examined the impact of n-3 fatty acid-enriched enteral formulas on patients undergoing major surgery. Most studies focused on intravenous fish oil and suggest beneficial effects both on inflammatory/immune parameters and patient outcome. Studies suggest that lipid use in critically ill patients may be improved by increased knowledge of genetic determinants of severity of injury and response to therapeutic agents as well as by the development of tools that allow better timing of immunonutritional intervention.

SUMMARY

Overall, lipids, in particular n-3 fatty acids, emerge as powerful nutrients with pharmacologic properties potentially improving prognosis in critically ill patients. However, heterogeneity in study design makes the interpretation of available studies difficult. Consequently, larger prospective, randomized, double-blind trials with comparable methodologies are necessary for detailed evaluation of the pharmacologic impact of lipids. In addition, a better knowledge of the influence of genotypic variation and postinjury inflammatory/immune temporal patterns may improve our current therapeutic use of various fatty acids.