Low-carbohydrate, high-fat enteral formulas for managing glycemic control in patients who are critically ill: A review of the evidence

Nutritional Ketosis as a Therapeutic Approach in Critical Illness: A Systematic Review

Critical illness encompasses the dysfunction of vital organs, the risk of death, and potential reversibility; it is a major cause of morbidity and mortality globally. The pathophysiology underlying many critical illnesses includes bioenergetic failure, inflammation, and oxidative stress. This systematic review aims to explore the use of nutritional ketosis (ketogenic feeds and exogenous ketone body administration) as a potential therapy, affecting the aforementioned pathways in patients with critical illnesses. This study was conducted, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. The search was conducted, systematically using PubMed, PubMed Central (PMC), Google Scholar, and the ScienceDirect databases in February 2024. The inclusion criteria were set to free full-text articles published within the past five years: human and animal studies, literature reviews, systematic reviews, meta-analyses, observational studies, randomized controlled trials, case reports, book chapters, gray literature, studies investigating adult samples, and articles in the English language. Exclusion criteria included pediatric studies as the topic has been studied more extensively in children, and this review aims to explore potential benefits in adult patients. The search was conducted through four databases; after the screening process, the remaining studies were assessed through quality appraisal tools appropriate to each study type. In the end, 11 studies were selected, including eight narrative reviews, one cohort study, one animal study, and one randomized controlled trial. The results of this review demonstrated that nutritional ketosis has potential safe and effective benefits for humans and animals. Nutritional ketosis shows therapeutic benefits for a vast variety of complications commonly associated with critical illness, status epilepticus, sepsis, viral infections, and glycemic control. In the end, both randomized and nonrandomized clinical trials are necessary for more conclusive findings.

The role of low-carbohydrate diets in the intensive care unit

Low-carbohydrate, high-fat (LCHF) nutrition therapy is characterized by carbohydrates comprising <26% of the daily caloric intake and a higher proportion of fat. LCHF therapies reduce exogenous glucose load, improve glycemic control, decrease inflammation, and improve clinical outcomes such as respiratory function. Given the altered metabolism in critically ill patients, LCHF nutrition therapy may be especially beneficial as it enables the conservation of protein and glucose for metabolic roles beyond energy use. In critical illness, LCHF diets have the potential to reduce hyperglycemia, improve ventilation, decrease hospital length of stay and reduce hospital costs. The purpose of this commentary piece is to describe LCHF nutrition therapy, summarize its impact on health outcomes, and discuss its role in the intensive care unit (ICU). Additional research on the effects of LCHF nutrition therapy on critically ill patients is warranted, including a focus on COVID-19.

Lipid emulsions in clinical nutrition: Enteral and parenteral nutrition

Clinical nutrition emulsions are important products that can be life-saving for many patients suffering from gastrointestinal tract disorders, swallowing impairment, cancer, liver diseases, and many other clinical conditions. The transfer of lipids to the human body can be either intravenously (Parenteral Nutrition, PN) or through the gastrointestinal tract (Enteral Nutrition, EN). PN emulsions are considered pharmaceuticals and thus regulated accordingly. On the other hand, EN emulsions are classified as Food for Specific Medical Purposes (FSMP) and do not follow pharmaceutical regulations. Regarding product design, PN emulsions must follow theoretical emulsion formulation and production aspects, but special requirements regarding droplet size distribution must be followed to comply with national pharmacopeia monographs. Furthermore, a full clinical program on clinical evidence to prove safety and efficacy must be provided for marketing approval. On the contrary, EN emulsions require limited clinical evidence to substantiate health or clinical benefits. A short introduction to clinical nutrition with a focus on lipid emulsions is presented in this chapter. Furthermore, a general overview of the composition and main ingredients of clinical nutrition lipid emulsions is reviewed. Main clinical aspects are also mentioned here, highlighting the difficulties of clinically proving the efficacy of these products. The manufacturing and control of clinical nutrition emulsions are also reviewed, focusing on PN products and the main regulatory requirements related to the safety of these intravenous emulsions. Finally, stability and physicochemical properties are reviewed, and examples of commercially available products are used to illustrate these properties linked to the stability of these products. Lipids in clinical nutrition is a moving field and we do hope this chapter may remain a valuable source to understand newly emerging research on this topic.

Enteral nutrition product formulations: A review of available products and indications for use

When oral nutrition is not feasible, enteral nutrition (EN) therapy is often considered the preferred route of nutrition support to meet the nutrient needs of individuals with a functional gastrointestinal tract across multiple levels of care (critical care, acute care, and home care). Enteral formulations have progressively evolved over the last 50 years from the simple blending of hospital food thin enough to run through a feeding tube, to the development of commercial standard formulas, followed by specialized formulas with immune-modulating and disease-specific qualities, to the most recent shift to food-based or blenderized EN composed of natural, whole foods with perceived health benefits. With the vast number of enteral formulations on the market, clinicians may be overwhelmed trying to determine proven vs theoretical benefits. This review is intended to explore differences in enteral formulations, identify implications for clinical practice, and review evidenced-based clinical guidelines to assist clinicians in enteral formula selection.

Nutrition support practices for critically ill patients with severe acute respiratory syndrome coronavirus-2: A multicentre observational study in Singapore

INTRODUCTION

To improve the nutritional care and resource allocation of critically ill patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), we described their characteristics, treatment modalities and clinical outcomes, and compared their nutrition interventions against the American Society for Parenteral and Enteral Nutrition (ASPEN) recommendations.

METHODS

This was a retrospective observational study conducted in 5 tertiary hospitals in Singapore. Characteristics, treatment modalities, clinical outcomes and nutrition interventions of critically ill patients with SARS-CoV-2 who received enteral and parenteral nutrition were collected between January and May 2020.

RESULTS

Among the 83 critically ill patients with SARS-CoV-2, 22 (28%) were obese, 45 (54%) had hypertension, and 21 (25%) had diabetes. Neuromuscular blockade, prone therapy and dialysis were applied in 70% (58), 47% (39) and 35% (29) of the patients, respectively. Refeeding hypophosphataemia and hospital mortality occurred respectively in 6% (5) and 18% (15) of the critically ill patients with SARS-CoV-2. Late enteral nutrition and cardiovascular comorbidities were associated with higher hospital mortality (adjusted relative risk 9.00, 95% confidence interval [CI] 2.25-35.99; 6.30, 95% CI 1.15-34.40, respectively). Prone therapy was not associated with a higher incidence of high gastric residual volume (≥250mL). The minimum caloric (15kcal/kg) and protein (1.2g/kg) recommendations of ASPEN were achieved in 54% (39) and 0% of the patients, respectively.

CONCLUSION

The high obesity prevalence and frequent usage of neuromuscular blockade, prone therapy, and dialysis had considerable implications for the nutritional care of critically ill patients with SARS-CoV-2. They also did not receive adequate calories and protein. More audits should be conducted to refine nutritional interventions and guidelines for this ever-evolving disease.

Enteral Nutrition Overview

Enteral nutrition (EN) provides critical macro and micronutrients to individuals who cannot maintain sufficient oral intake to meet their nutritional needs. EN is most commonly required for neurological conditions that impair swallow function, such as stroke, amytrophic lateral sclerosis, and Parkinson’s disease. An inability to swallow due to mechanical ventilation and altered mental status are also common conditions that necessitate the use of EN. EN can be short or long term and delivered gastrically or post-pylorically. The expected duration and site of feeding determine the type of feeding tube used. Many commercial EN formulas are available. In addition to standard formulations, disease specific, peptide-based, and blenderized formulas are also available. Several other factors should be considered when providing EN, including timing and rate of initiation, advancement regimen, feeding modality, and risk of complications. Careful and comprehensive assessment of the patient will help to ensure that nutritionally complete and clinically appropriate EN is delivered safely.