Intravenous lipid emulsions in the critically ill: an update

Parenteral Nutrition in the Critically Ill Adult: A Narrative Review

Malnutrition in adult intensive care unit patients is associated with poor clinical outcomes. Providing adequate nutritional support to the critically ill adult should be an important goal for the intensivist. This narrative review aims to delineate the role of parenteral nutrition (PN) in meeting nutritional goals. We examined the data regarding the safety and efficacy of PN compared to enteral nutrition. In addition, we describe practical considerations for the use of PN in the ICU including patient nutritional risk stratification, nutrient composition selection for PN, route of PN administration, and biochemical monitoring.

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.

Parenteral Nutrition, Sepsis, Acute Heart Failure and Hepatotoxic Drugs Are Related to Liver Test Disturbances in Critically Ill Patients

BACKGROUND

Parenteral nutrition (PN) is often associated with liver dysfunction in the ICU, although other factors such as sepsis, acute heart failure (AHF), and hepatotoxic drugs can be equally present. The relative impact of PN on liver dysfunction in critically ill patients is largely unknown.

METHODS

We recorded the presence of pre-existing liver disturbances, AHF, sepsis, daily PN volume, and commonly used hepatotoxic drugs in adult ICU patients, together with daily aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), alkalic phosphatase (AP), total bilirubin (TB), and INR values in patients with three or more PN treatment days. A linear mixed-effects model was used to assess the relative contribution of each liver parameter. Nutritional adequacy was defined as intake/needs.

RESULTS

We included 224 ICU patients with PN treatment lasting more than 3 days between 1 January 2017 and 31 December 2019. For AST, pre-existing liver disturbances (+180% ± 11%) and the presence of AHF (+75% ± 14%) were the main predictors of deterioration, whereas PN volume caused only a limited increase of 14% ± 1%/L. Similar results were observed for ALT. GGT, INR, and TB are mainly influenced by the presence of sepsis/septic shock and pre-existing liver disturbances, with no impact of PN or hepatotoxic drugs. Carbohydrate intake exceeded recommendations, and protein and lipid intake were insufficient in this study cohort.

CONCLUSIONS

Liver test disturbances in ICU patients on PN are multifactorial, with sepsis and AHF having the highest influence, with only limited impact from PN and hepatotoxic drugs. Feeding adequacy can be improved.

Three Lipid Emulsions Reduce Staphylococcus aureus-Stimulated Phagocytosis in Mouse RAW264.7 Cells

Soybean oil (SO)-, SO medium-chain triglyceride (MCT)-, olive oil (OO)-, and fish oil (FO)-based lipid emulsions are generally applied in clinical practice via intravenous injection for patients with nutritional requirements. The function of lipid emulsions on immune modulation remains inconsistent, and their effects on macrophages are limited. In the present study, we used a model of S. aureus-infected mouse RAW264.7 macrophages to determine the influence of three different compositions of lipid emulsions (Lipofundin, ClinOleic, and Omegaven) on reactive oxygen species (ROS) production, phagocytosis, and bacterial survival. The three individual lipid emulsions similarly enhanced bacterial survival but reduced S. aureus-stimulated ROS, phagocytosis of S. aureus bioparticles conjugate, polymerization of F-actin, and phosphorylation of AKT, JNK, and ERK. Compared with the JNK and ERK inhibitors, the PI3K inhibitor markedly suppressed the phagocytosis of S. aureus bioparticles conjugate and the polymerization of F-actin, whereas it significantly increased the bacterial survival. These results suggest that the three lipid emulsions diminished ROS production and phagocytosis, resulting in increased bacterial survival. PI3K predominantly mediated the inhibitory effects of the lipid emulsions on the phagocytosis of mouse RAW264.7 macrophages.

Lipid-Free PN is Associated with an Increased Risk of Hyperbilirubinemia in Surgical Critically Ill Patients with Admission Hepatic Disorder: A Retrospective Observational Study

Background

To evaluate the effect of different PN types on surgical critically ill trauma/acute care surgery patients with hepatic disorders at admission.

Methods

This is a retrospective study. The PN types included lipid-free, soybean oil/medium-chain triglyceride, olive oil-based, and fish oil-containing PNs. Patients admitted with liver injury or liver surgery, elevated serum AST/ALT level, and elevated serum total bilirubin level were included. The exclusion criteria are as follows: 1) age <18 years, 2) severe liver disease/cirrhosis, 3) received more than one type of PN and 4) serum total bilirubin >4.9 mg/dl at admission. Demographics, severity, comorbidities, blood stream infection, hyperbilirubinemia (total bilirubin > 6.0 mg/dl), and mortality were collected for analysis. We also performed analysis stratified by separated lipid doses (g/kg/day).

Results

A total of 156 patients were enrolled. There were no demographic differences among groups. The lipid-free group was associated with the highest mortality rate and incidence of hyperbilirubinemia. Compared to the lipid-free group, the olive oil-based group had the lowest risk of hyperbilirubinemia. After being stratified by separated lipid doses, the incidence of hyperbilirubinemia decreased when the lipid dosage increased. Regarding different types of lipids, patients who received more than the median dosage of lipids showed a significantly lower risk of hyperbilirubinemia, except in the fish oil-containing group.

Conclusion

Our result suggested that lipid-free PN is associated with an increased risk of hyperbilirubinemia in surgical critically ill patients with admission hepatic disorder. Further studies are warranted.

Lipid-Free Parenteral Nutrition Is Associated with an Increased Risk of Hepatic Dysfunction in Surgical Critically Ill Patients: A Retrospective Observational Study

To evaluate the effects of lipid-free parenteral nutrition (PN) and various intravenous fat emulsions (IVFEs) on hepatic function in surgical critically ill trauma/acute care surgery patients. We retrospectively reviewed trauma/acute care surgery patients without admission hepatic disorder that received PN. The PN groups include lipid-free, soybean oil/medium-chain triglyceride, olive oil-based, and fish-oil contained PN. We excluded patients with (1) age <18 years, (2) without surgery, (3) preexisting liver injury/diseases, (4) hyperbilirubinemia at admission, (5) received more than one type of PN, and (6) repeated ICU episodes in the same hospitalization. Hepatic dysfunction was considered as serum total–bilirubin >6.0 mg/dL. The demographics, severity score, comorbidities, blood stream infection, and mortality were collected for analyses. The major outcome is hepatic function. We also performed analyses stratified by separated lipid doses (g/kg/day). A total of 249 patients were enrolled. There were no demographic differences among groups. The lipid-free PN group had a higher incidence of hepatic dysfunction and mortality. Compared to the lipid-free group, the other three IVFEs had significantly lower risks of hepatic dysfunction, while the olive oil-based group had a significantly lower risk of 30 and 90-day mortality. After being stratified by separating lipid doses, the soybean oils showed a decreasing trend of hepatic dysfunction and mortality with increased dosage. Fish oil >0.05 g/kg/day was associated with lower hepatic dysfunction incidences. Our findings suggest that, when compared to IVFEs, surgical critically ill patients with trauma/acute care surgery that received lipid-free PN are associated with an increased risk of hepatic dysfunction. In addition, the olive oil-based group had a significantly lower risk of mortality, while fish oil >0.05 g/kg/day was associated with lower incidences of hepatic dysfunction; however, further studies are warranted.

Acute Hypertriglyceridemia in Patients with COVID-19 Receiving Parenteral Nutrition

Hypertriglyceridemia is a metabolic complication associated with parenteral nutrition (PN). It is unknown if patients with acute respiratory distress syndrome (ARDS) secondary to COVID-19 are more at risk. Our aim was to describe the incidence, risk factors and clinical impact of hypertriglyceridemia in critically ill patients with ARDS-COVID-19 receiving PN. We designed a cohort study of patients with ARDS-COVID-19 infection that required admission to critical care units and nutritional support with PN. Individual PN prescriptions for macronutrients and insulin were provided. Lipid emulsion contained fish oil (SMOFlipid® or Lipoplus®). Hypertriglyceridemia was defined as plasma levels above 400 mg/dL. Eighty-seven patients, 66.6% men, 60.1 ± 10.8 years old, BMI 29.1 ± 5.6 kg/m2, 71% of whom received lopinavir/ritonavir, 56% received Propofol and 55% received Tocilizumab were included. The incidence of hypertriglyceridemia was 37 × 100 patient-days with PN. This complication was more frequent in obese patients (OR 3.34; 95% CI, 2.35-4.33) and in those treated with lopinavir/ritonavir (OR 4.98; 95% CI, 3.60-6.29) or Propofol (OR 2.45; 95% CI, 1.55-3.35). Total mortality was 33.3%, similar between the type of lipid emulsion (p = 0.478). On average, patients with hypertriglyceridemia had a longer requirement of PN compared to the group without elevated triglycerides (TG), probably because of their longer survival (p = 0.001). TG higher than 400 mg/dL was not a protective factor for mortality (OR 0.31; 95% CI, 0.01-1.30). In conclusion, the incidence of hypertriglyceridemia was 37 × 100 patient-days with PN. The risk of this complication is associated with obesity and the use of lopinavir/ritonavir or Propofol.

Interfacial kinetics in olive oil-in-water nanoemulsions: Relationships between rates of initiation of lipid peroxidation, induction times and effective interfacial antioxidant concentrations

HYPOTHESIS

A detailed quantitative description of the effects of antioxidants in inhibiting lipid peroxidation in oil-in-water emulsions can be achieved by determining the relationships between the rates of initiation of the lipid peroxidation reaction, the length of the induction period preceding the propagation step of the radical oxidation process and the effective antioxidant interfacial concentrations.

EXPERIMENTS

We successfully prepared and characterized a series of olive oil-in-water nanoemulsions and allowed them to spontaneously oxidize. Their oxidative stability was evaluated by carrying out in the presence, and absence, of antioxidants derived from gallic acid, by monitoring the formation of primary oxidation products with time, by determining the corresponding induction periods, and by determining the effective interfacial concentrations of the antioxidants in the intact emulsions.

FINDINGS

Results show that both, the length of the induction periods and the antioxidant interfacial concentrations change concomitantly, increasing with the hydrophobicity of the antioxidant up to a maximum at the octyl derivative; longer aliphatic chains decrease their efficiency. The ratio between the interfacial antioxidant concentration and the induction period remains constant independently of the antioxidant, demonstrating that the effective concentrations of antioxidant at the interface control their efficiencies in emulsions.

ESPEN guideline on clinical nutrition in the intensive care unit

Following the new ESPEN Standard Operating Procedures, the previous guidelines to provide best medical nutritional therapy to critically ill patients have been updated. These guidelines define who are the patients at risk, how to assess nutritional status of an ICU patient, how to define the amount of energy to provide, the route to choose and how to adapt according to various clinical conditions. When to start and how to progress in the administration of adequate provision of nutrients is also described. The best determination of amount and nature of carbohydrates, fat and protein are suggested. Special attention is given to glutamine and omega-3 fatty acids. Particular conditions frequently observed in intensive care such as patients with dysphagia, frail patients, multiple trauma patients, abdominal surgery, sepsis, and obesity are discussed to guide the practitioner toward the best evidence based therapy. Monitoring of this nutritional therapy is discussed in a separate document.

Tailoring nutrition therapy to illness and recovery

Without doubt, in medicine as in life, one size does not fit all. We do not administer the same drug or dose to every patient at all times, so why then would we live under the illusion that we should give the same nutrition at all times in the continuum of critical illness? We have long lived under the assumption that critical illness and trauma lead to a consistent early increase in metabolic/caloric need, the so-called “hypermetabolism” of critical illness. What if this is incorrect? Recent data indicate that early underfeeding of calories (trophic feeding) may have benefits and may require consideration in well-nourished patients. However, we must confront the reality that currently ICU nutrition delivery worldwide is actually leading to “starvation” of our patients and is likely a major contributor to poor long-term quality of life outcomes. To begin to ascertain the actual calorie and protein delivery required for optimal ICU recovery, an understanding of “starvation” and recovery from starvation and lean body mass (LBM) loss is needed. To begin to answer this question, we must look to the landmark Minnesota Starvation Study from 1945. This trial defines much of the world’s knowledge about starvation, and most importantly what is required for recovery from starvation and massive LBM loss as occurs in the ICU. Recent and historic data indicate that critical illness is characterized by early massive catabolism, LBM loss, and escalating hypermetabolism that can persist for months or years. Early enteral nutrition during the acute phase should attempt to correct micronutrient/vitamin deficiencies, deliver adequate protein, and moderate nonprotein calories in well-nourished patients, as in the acute phase they are capable of generating significant endogenous energy. Post resuscitation, increasing protein (1.5–2.0 g/kg/day) and calories are needed to attenuate LBM loss and promote recovery. Malnutrition screening is essential and parenteral nutrition can be safely added following resuscitation when enteral nutrition is failing based on pre-illness malnutrition and LBM status. Following the ICU stay, significant protein/calorie delivery for months or years is required to facilitate functional and LBM recovery, with high-protein oral supplements being essential to achieve adequate nutrition.

Omega-3 Polyunsaturated Fatty Acids in Critical Illness: Anti-Inflammatory, Proresolving, or Both?

Prognosis and outcomes of critically ill patients are strictly related with inflammatory status. Inflammation involves a multitude of interactions between different cell types and chemical mediators. Omega-3 polyunsaturated fatty acids (PUFAs), mainly represented by eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are able to inhibit different pathways including leukocyte chemotaxis, adhesion molecule expression and interactions, and production of inflammatory cytokines, through the action of specialized proresolving mediators (SPMs). SPMs from omega-6 fatty acids, such as lipoxins, and from omega-3 fatty acids such as resolvins, protectins, and maresins, act in reducing/resolving the inflammatory process in critical diseases, stimulating the phases of resolution of inflammation. In this light, the resolution of inflammation is nowadays considered as an active process, instead of a passive process. In critical illness, SPMs regulate the excessive posttrauma inflammatory response, protecting organs from damage. This review focuses on the role of omega-3 PUFAs as pharma nutrition agents in acute inflammatory conditions, highlighting their effects as anti-inflammatory or proresolving agents.