Muscle Protein Synthesis Following Protein Administration in Critical Illness

The urea-to-creatinine ratio as an emerging biomarker in critical care: a scoping review and meta-analysis

BACKGROUND

Severe protein catabolism is a major aspect of critical illness and leads to pronounced muscle wasting and, consequently, extended intensive care unit (ICU) stay and increased mortality. The urea-to-creatinine ratio (UCR) has emerged as a promising biomarker for assessing protein catabolism in critical illness, which is currently lacking. This review aims to elucidate the role of UCR in the context of critical illness.

METHODS

This scoping review adhered to the PRISMA Extension for Scoping Reviews guidelines. A comprehensive literature search was conducted on the 3rd of September 2024, across Embase, PubMed, ScienceDirect, and Cochrane Library to identify studies related to (1) critically ill adult patients and (2) reporting at least a single UCR value. A meta-analysis was conducted for ≥ 5 studies with identical outcome parameters.

RESULTS

Out of 1,450 studies retrieved, 47 were included in this review, focusing on UCR's relation to protein catabolism and persistent critical illness (10 studies), mortality (16 studies), dietary protein interventions (2 studies), and other outcomes (19 studies), such as delirium, and neurological and cardiac adverse events. UCR is inversely correlated to muscle cross-sectional area over time and associated to length of ICU stay, emphasising its potential role in identifying patients with ongoing protein catabolism. A UCR (BUN-to-creatinine in mg/dL) of ≥ 20 (equivalent to a urea-to-creatinine in mmol/L of approximately 80) upon ICU admission, in comparison with a value < 20, was associated with a relative risk of 1.60 (95% CI 1.27-2.00) and an adjusted hazard ratio of 1.29 (95% CI 0.89-1.86) for in-hospital mortality.

DISCUSSION

UCR elevations during critical illness potentially indicate muscle protein catabolism and the progression to persistent critical illness, and high levels at ICU admission could be associated with mortality. UCR increments during ICU stay may also indicate excessive exogenous dietary protein intake, overwhelming the body's ability to use it for whole-body or muscle protein synthesis. Dehydration, gastrointestinal bleeding, kidney and liver dysfunction, and renal replacement therapy may also influence UCR and are considered potential pitfalls when assessing catabolic phases of critical illness by UCR. Patient group-specific cut-off values are warranted to ensure its validity and application in clinical practice.

Recognizing malnutrition in adults with critical illness: Guidance statements from the Global Leadership Initiative on Malnutrition

BACKGROUND

Patients with critical illness may present with disease-related malnutrition upon intensive care unit (ICU) admission. They are at risk of development and progression of malnutrition over the disease trajectory because of inflammation, dysregulated metabolism, and challenges with feeding.

METHODS

The Global Leadership Initiative on Malnutrition (GLIM) convened a panel of 36 clinical nutrition experts to develop consensus-based guidance statements addressing the diagnosis of malnutrition during critical illness using a modified Delphi approach with a requirement of ≥75% agreement.

RESULTS

(1) To identify pre-existing malnutrition, we suggest evaluation within 48 h of ICU admission when feasible (100% agreement) or within 4 days (94% agreement). (2) To identify the development and progression of malnutrition, we suggest re-evaluation of all patients every 7-10 days (97% agreement). (3) To identify progressive loss of muscle mass, we suggest evaluation of muscle mass as soon as feasible (92% agreement) and again after 7-10 days (89% agreement). (4) To identify the development and progression of malnutrition before and after ICU discharge, we suggest re-evaluating nutrition status before ICU discharge and during clinical visits that follow (100% agreement).

CONCLUSION

Research using consistent etiologic and phenotypic variables offers great potential to assess the efficacy of nutrition interventions for critically ill patients with malnutrition. Assessment of these variables during and beyond the ICU stay will clarify the trajectory of malnutrition and enable exploration of impactful treatment modalities at each juncture. GLIM offers a diagnostic approach that can be used to identify malnutrition in critically ill patients.

Levodopa and nutrition support: A case report of Parkinsonism-hyperpyrexia syndrome

Levodopa is competitively inhibited by amino acids for absorption across the intestinal wall and blood-brain barrier. An acute withdrawal of levodopa increases the risk of Parkinsonism-hyperpyrexia syndrome, a life-threatening condition characterized by muscular rigidity, mental status changes, hyperthermia, and autonomic instability. This report discusses the case of a patient with Parkinson's disease who was critically ill who developed Parkinsonism-hyperpyrexia syndrome while receiving enteral and parenteral nutrition support. Clinicians should be aware of this potential drug-nutrient interaction when prescribing nutrition support to patients taking levodopa.

Body Composition Assessment in Critically Ill Adults - Where are We now?

This narrative review provides an overview of body composition methods available for use in critically ill patients. It focuses on the relevance and discussion of the most commonly used techniques. Further, we discuss the validity of these methods with a focus on muscle mass assessment, measuring changes over time and the identification of patients with lower-than-normal muscularity. Current available evidence, as well as future directions is highlighted.

Advancements in nutritional support for critically ill patients

PURPOSE OF REVIEW

To summarize the clinical evidence on nutritional support for critically ill patients, the (patho)physiological mechanisms involved, and areas of future research.

RECENT FINDINGS

Large randomized controlled trials have shown that early nutrition induces dose-dependent harm in critically ill patients, regardless of the feeding route, and that early high-dose amino acids are harmful. Harm has been attributed to feeding-induced suppression of cellular repair pathways including autophagy and ketogenesis, to aggravation of hyperglycemia and insulin needs, and to increased urea cycle activity. Additionally, acute critical illness was shown to be a state of anabolic resistance. The absence of benefit of early enhanced nutritional support on short- and long-term outcomes was observed in all studied subgroups.

SUMMARY

While early high-dose nutrition should be avoided in all critically ill patients, the optimal initiation time of nutrition support for the individual patient, as well as ideal composition and dosing of nutrition over time remain unclear. Future studies should elucidate how fasting-induced repair pathways can be activated while avoiding prolonged starvation, and how hyperglycemia and high insulin need could be prevented. Potential strategies include intermittent fasting, ketogenic diets, ketone supplements, and alternative glucose-lowering agents, whether or not in combination with exercise.

Why One-Size-Fits-All Doesn't Work in Intensive Care Unit Nutrition?

Nutrition therapy is a complex intervention with several underlying considerations that may influence effectiveness. Considerations include the mechanism of action of the intervention and the patient phenotype, including sex, ethnicity, body composition, and the patients' nutritional and inflammatory status. Energy and protein targets are elements of nutrition therapy that may be particularly influenced by individual patient factors. Biomarkers may provide a useful tool to monitor and individualize nutrition therapy in the future. The considerations mentioned, with many yet to be studied, highlight the rationale for more individualized interventions moving away from a 'one-size-fits-all' approach.

Skeletal Muscle: A Critical Organ for Survival and Recovery in Critical Illness

The intensive care unit (ICU) environment is one of the most challenging for skeletal muscle health. Atrophy associated with clinical care is distinct from that seen with inactivity or immobilization in the absence of disease and is exacerbated by aging. The substantial muscle loss in the ICU is likely due to the presence of inflammation, elevated proteolysis, bedrest, and undernutrition. Skeletal muscle parameters at admission are predictive of mortality and other clinically important outcomes. Treatment goals to mitigate muscle loss are early mobilization and adequate nutrient supply, especially protein, using an individualized approach to support skeletal muscle maintenance and recovery.

Recognizing malnutrition in adults with critical illness: Guidance statements from the Global Leadership Initiative on Malnutrition

BACKGROUND

Patients with critical illness may present with disease-related malnutrition upon intensive care unit (ICU) admission. They are at risk of development and progression of malnutrition over the disease trajectory because of inflammation, dysregulated metabolism, and challenges with feeding.

METHODS

The Global Leadership Initiative on Malnutrition (GLIM) convened a panel of 36 clinical nutrition experts to develop consensus-based guidance statements addressing the diagnosis of malnutrition during critical illness, using a modified Delphi approach with a requirement of ≥75% agreement.

RESULTS

CONCLUSION: Research using consistent etiologic and phenotypic variables offers great potential to assess the efficacy of nutrition interventions for critically ill patients with malnutrition. Assessment of these variables at during and beyond the ICU stay will clarify the trajectory of malnutrition and enable exploration of impactful treatment modalities at each juncture. GLIM offers a diagnostic approach that can be used to identify malnutrition in critically ill patients.

The Japanese Critical Care Nutrition Guideline 2024

Nutrition therapy is important in the management of critically ill patients and is continuously evolving as new evidence emerges. The Japanese Critical Care Nutrition Guideline 2024 (JCCNG 2024) is specific to Japan and is the latest set of clinical practice guidelines for nutrition therapy in critical care that was revised from JCCNG 2016 by the Japanese Society of Intensive Care Medicine. An English version of these guidelines was created based on the contents of the original Japanese version. These guidelines were developed to help health care providers understand and provide nutrition therapy that will improve the outcomes of children and adults admitted to intensive care units or requiring intensive care, regardless of the disease. The intended users of these guidelines are all healthcare professionals involved in intensive care, including those who are not familiar with nutrition therapy. JCCNG 2024 consists of 37 clinical questions and 24 recommendations, covering immunomodulation therapy, nutrition therapy for special conditions, and nutrition therapy for children. These guidelines were developed in accordance with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system by experts from various healthcare professionals related to nutrition therapy and/or critical care. All GRADE-based recommendations, good practice statements (GPS), future research questions, and answers to background questions were finalized by consensus using the modified Delphi method. Strong recommendations for adults include early enteral nutrition (EN) within 48 h and the provision of pre/synbiotics. Weak recommendations for adults include the use of a nutrition protocol, EN rather than parenteral nutrition, the provision of higher protein doses, post-pyloric EN, continuous EN, omega-3 fatty acid-enriched EN, the provision of probiotics, and indirect calorimetry use. Weak recommendations for children include early EN within 48 h, bolus EN, and energy/protein-dense EN formulas. A nutritional assessment is recommended by GPS for both adults and children. JCCNG 2024 will be disseminated through educational activities mainly by the JCCNG Committee at various scientific meetings and seminars. Since studies on nutritional treatment for critically ill patients are being reported worldwide, these guidelines will be revised in 4 to 6 years. We hope that these guidelines will be used in clinical practice for critically ill patients and in future research.

Combined Effects of Early Mobilization and Nutrition on ICU-Acquired Weakness

Intensive Care Unit-Acquired Weakness (ICUAW) is a very common condition in patients admitted to intensive care units (ICUs), even after relatively short stays. This weakness can develop with a pre-existing background of sarcopenia or cachexia, although these conditions are not always the direct cause. Over the years, much of the literature has focused on the nutritional aspect of the issue, leading to the development of widely accepted guidelines recommending the initiation of early nutrition, with the goal of achieving caloric and protein targets within the first five days of ICU admission. Despite adherence to these guidelines, several studies have shown a significant loss of muscle mass in critically ill patients, which directly impacts their ability to generate strength. However, it has become increasingly evident that nutrition alone is not sufficient to counteract this muscle loss, which is often closely linked to the prolonged immobility experienced by ICU patients due to a variety of clinical and logistical factors. In particular, there is growing evidence suggesting that even the introduction of early and minimal rehabilitation-including passive mobilization-when combined with appropriate nutritional support, can be a valuable strategy to help reduce the incidence of ICUAW. In this narrative review, we aim to summarize the current scientific knowledge on this topic, emphasizing the importance of an integrated approach that combines nutrition and early mobilization. Such a combined strategy not only holds the potential to reduce the acute incidence of ICUAW but also contributes to better recovery outcomes and, eventually, improved quality of life for these patients.

Feasibility challenges in protein supplementation research: Insights from the convalescence of functional outcomes after intensive care unit stay in a Randomised Controlled Trial

BACKGROUND & AIMS

Dietary protein supplementation may benefit physical outcomes in post-intensive care unit (ICU) patients suffering ICU-acquired weakness (ICU-AW). This study examines the impact of a six-week protein supplementation compared to an isocaloric carbohydrate on physical functioning outcomes in post-ICU patients with a follow-up of 12 weeks after ICU discharge. This paper presents descriptive data, feasibility outcomes, and the barriers faced while conducting this nutritional intervention study in post-ICU patients.

METHODS

This two-arm, randomised, double-blind controlled intervention trial involved adult patients (≥18 y) who were admitted to the ICU for ≥72 h with moderate ICU-AW (Medical Research Council (MRC) score 24-48). Patients were randomly assigned to receive 22 g of collagen peptides supplementation or an isocaloric carbohydrate twice daily. The primary outcome was a composite score for physical functioning comprising handgrip strength, leg muscle strength, arm muscle strength, and exercise capacity, adjusted for age, sex, and body weight. Secondary endpoints included nutritional intake and biomarkers, scores in other post-intensive care syndrome (PICS) domains, and mortality rates. Descriptive data is presented, no between-intervention group analyses were conducted due to incomplete sample size.

RESULTS

A total of 900 patients were screened for eligibility to participate in the study, of whom 59 met the requisite criteria between April 2022 and December 2023. The most common reasons for exclusion were treatment limitations, diabetes mellitus, or an MRC score <24 or above >48. Of the 59 patients deemed eligible, 15 patients were included to participate in the study. Due to the slow inclusion rate, the study was terminated early (at ∼20 % of anticipated sample size). At baseline (ICU discharge), patients initially had lower physical scores than reference values but showed improved (higher) scores at three months post-ICU discharge. Differences between the groups regarding the primary outcome (composite score of physical functioning) could not be identified due to early termination. Factors affecting the feasibility of nutrition research in post-ICU patients were identified, including slow patient recruitment rates, low adherence to the intervention, and the inability to complete outcome assessments.

CONCLUSIONS

Patients exhibited initial physical functioning scores below the reference values yet demonstrated substantial physical recuperation by the 12-week mark following their ICU discharge in both groups. Patients exhibited lower scores in all domains of PICS compared to reference values, emphasising the necessity for further investigation into the potential role of nutrition interventions in preventing and alleviating PICS symptoms. Furthermore, this study describes the factors affecting the feasibility of post-ICU intervention studies and provides recommendations for future studies on effective design and conduction of studies to address PICS (This study was supported by Rousselot; Confucius ClinicalTrials.gov number, NCT05405764).

On how to feed critically ill children in intensive care: A slowly shifting paradigm

Critically ill children requiring treatment in a pediatric intensive care unit (PICU) suffer from anorexia and/or feeding intolerance. The resulting macronutrient deficit associates with poor outcome. Until recently, this association formed the basis for initiating enteral or parenteral feeding early to improve outcome. The multicenter "Early-versus-Late-Parenteral-Nutrition-in-the-Pediatric-Intensive-Care-Unit" randomized controlled trial (PEPaNIC-RCT) addressed whether this association is causal. It showed that early supplementation of insufficient/contraindicated enteral nutrition with parenteral nutrition, as compared with accepting a macronutrient deficit throughout the first week in the PICU, did not improve outcome. On the contrary, it caused more infections and prolonged organ support and PICU stay, and adversely affected neurodevelopmental outcomes 2 and 4 years later. Harm was present in all subgroups and appeared explained by the macronutrient dose, more specifically the amino-acid dose, not lipid or glucose doses. These findings corroborated results from large-scale adult RCTs. Mechanisms of harm from early enhanced nutrition comprised suppressed cellular repair pathways like autophagy and ketogenesis, suppressed illness-induced alterations in thyroid hormone metabolism, more iatrogenic hyperglycemia, increased urea cycle activity through anabolic resistance, and induction of epigenetic modifications that mediate longer-term developmental impairments. These results came unexpected to many pediatric intensivists. Hence, the paradigm has only slowly begun to shift toward more restrictive macronutrient administration in the acute phase of critical illness. Benefits of early fasting responses have become clear, provided micronutrients are given to prevent deficiencies and refeeding syndrome. These insights open perspectives for studies investigating novel nutritional strategies to activate fasting-induced cellular repair while avoiding prolonged starvation.

Higher Versus Lower Protein Delivery in Critically Ill Patients: A Systematic Review and Bayesian Meta-Analysis

OBJECTIVES

Recent multicenter trials suggest that higher protein delivery may result in worse outcomes in critically ill patients, but uncertainty remains. An updated Bayesian meta-analysis of recent evidence was conducted to estimate the probabilities of beneficial and harmful treatment effects.

DATA SOURCES

An updated systematic search was performed in three databases until September 4, 2024. The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines and the protocol was preregistered in PROSPERO (CRD42024546387).

STUDY SELECTION

Randomized controlled trials that studied adult critically ill patients comparing protein doses delivered enterally and/or parenterally with similar energy delivery between groups were included.

DATA EXTRACTION

Data extraction was performed by two authors independently, using a predefined worksheet. The primary outcome was mortality. Posterior probabilities of any benefit (relative risk [RR] < 1.00) or harm (RR > 1.00) and other important beneficial and harmful effect size thresholds were estimated. Risk of bias assessment was performed using the risk of bias 2.0 tool. All analyses were performed using a Bayesian hierarchical random-effects models, under vague priors.

DATA SYNTHESIS

Twenty-two randomized trials ( n = 4164 patients) were included. The mean protein delivery in the higher and lower protein groups was 1.5 ± 0.6 vs. 0.9 ± 0.4 g/kg/d. The median RR for mortality was 1.01 (95% credible interval, 0.84-1.16). The posterior probability of any mortality benefit from higher protein delivery was 43.6%, while the probability of any harm was 56.4%. The probabilities of a 1% (RR < 0.99) and 5% (RR < 0.95) mortality reduction by higher protein delivery were 38.7% and 22.9%, respectively. Conversely, the probabilities of a 1% (RR > 1.01) and 5% (RR > 1.05) mortality increase were 51.5% and 32.4%, respectively.

CONCLUSIONS

There is a considerable probability of an increased mortality risk with higher protein delivery in critically ill patients, although a clinically beneficial effect cannot be completely eliminated based on the current data.

Muscle Dysfunction and Physical Recovery After Critical Illness

During critical illness, patients experience significant and rapid onsets of muscle wasting and dysfunction with loss of strength, mass, and power. These deficits often persist long after the ICU, leading to impairments in physical function including reduced exercise capacity and increased frailty and disability. While there are numerous studies describing the epidemiology of impaired muscle and physical function in the ICU, there are significantly fewer data investigating mechanisms of prolonged and persistent impairments in ICU survivors. Additionally, while several potential clinical risk factors associated with poor physical recovery have been identified, there remains a dearth of interventions that have effectively improved outcomes long-term among survivors. In this article, we aim to provide a thorough, evidence-based review of the current state of knowledge regarding muscle dysfunction and physical function after critical illness with a focus on post-ICU and post-hospitalization phase of recovery.

Nutrition provision over time in longer stay critically ill patients: A post hoc analysis of The Augmented vs Routine Approach to Giving Energy Trial

BACKGROUND

Limited literature exists on nutrition practices for long-stay patients in the intensive care unit (ICU). We aimed to compare nutrition practices in the first and second weeks of an ICU admission.

METHOD

A post hoc exploratory analysis of The Augmented vs Routine Approach to Giving Energy Trial (TARGET) randomized controlled trial (RCT) was undertaken. Inclusion criteria were: enrolled in TARGET on day 1 or 2 of ICU admission and ICU length of stay (LOS) >14 days. Clinical characteristics are described, and nutrition delivery and management compared between days 1-7 and 8-14. Data are n (%), mean ± SD, median (interquartile range [IQR]), or mean difference (MD) and 95% confidence interval (95% CI), with P < 0.05 considered significant.

RESULTS

Data from 664 patients were analyzed (56.2 ± 16.3 years; 61% male; body mass index 29.2 ± 7.5 kg/m2 and APACHE II 21.9 ± 8.1). When comparing days 1-7 to 8-14: (1) energy delivery was greater (all sources: 1826 ± 603 vs 1729 ± 689 (MD: 97 [95% CI: 52-140] kcal/day, P < 0.001) and nonnutrition sources: 317 ± 230 vs 192 ± 197 (MD 125 [95% CI: 111-139] kcal/day; P < 0.001); (2) protein delivery was similar (66 ± 20 vs 68 ± 24 (MD: -1.4 [95% CI: -3.2 to 0.4] g/day; P = 0.125]); and (3) fewer patients received parenteral nutrition (PN) (5% vs 9%, P < 0.001) or small intestine feeding (3% vs 8%; P < 0.001).

CONCLUSION

In this post hoc analysis, patients with an ICU LOS >14 days had greater energy delivery and fewer patients received PN or small intestine feeding during days 1-7 than days 8-14. Uncertainty remains regarding whether these data reflect usual practice and the clinical implications of this.

Toward Precision in Nutrition Therapy

Precision in critical care nutrition is paramount, as it focuses nutrition interventions on those patients most likely to benefit, or those who might potentially be harmed. Critical care nutrition must therefore be tailored to individual metabolic needs as determined by factors that control the capacity for tissue homeostasis and anabolic responses. This ideally involves the accurate and timely assessment of macronutrient and micronutrient requirements, a careful evaluation of metabolic response mechanisms and the identification of circumstances that might interfere with the productive utilization of dietary substrates. Specific surrogate markers of metabolic response, such as blood glucose levels, urea levels, or nitrogen balance, might be used to evaluate the metabolic readiness for nutrition and to establish the timing, nature, and clinical effectiveness of nutrition interventions. Despite the pressing need to further develop more targeted approaches in critically ill patients, indices of immediate metabolic responses that correlate with favorable clinical outcomes are lacking. In addition, the development of precision approaches might address timely adjustments in protein, energy, or micronutrient supplementation based on evolving clinical conditions. Here, we review why precision tools are needed in critical care nutrition, our progress thus far, as well as promising approaches and technologies by which multidisciplinary healthcare teams can improve quality of care and clinical outcomes by individualizing nutrition interventions.

Intensive care unit acquired weakness and physical rehabilitation in the ICU

Approximately half of critically ill adults experience intensive care unit acquired weakness (ICUAW). Patients who develop ICUAW may have negative outcomes, including longer duration of mechanical ventilation, greater length of stay, and worse mobility, physical functioning, quality of life, and mortality. Early physical rehabilitation interventions have potential for improving ICUAW; however, randomized trials show inconsistent findings on the efficacy of these interventions. This review summarizes the latest evidence on the definition, diagnosis, epidemiology, pathophysiology, risks factors, implications, and management of ICUAW. It specifically highlights research gaps and challenges, with considerations for future research for physical rehabilitation interventions.

Early urea-to-creatinine ratio to predict rapid muscle loss in critically ill patients with sepsis: a single-center retrospective observational study

BACKGROUND

Patients with sepsis in the intensive care unit (ICU) often experience rapid muscle loss. The urea-to-creatinine ratio (UCR) is thought to reflect muscle breakdown (creatinine) and catabolism (urea) and is commonly used to assess nutritional and metabolic status. This study aimed to investigate whether changes in UCR (ΔUCR) can predict the development of rapid muscle loss in patients with sepsis.

METHODS

This retrospective observational study was conducted in a university ICU between 2014 and 2021, involving adult patients (≥ 18 years) diagnosed with sepsis. The primary outcome was the incidence of rapid muscle loss during ICU hospitalization. Changes in the cross-sectional muscle area at the third lumbar vertebra (L3SMA) were measured using CT images to evaluate muscle loss. Rapid muscle loss was defined as a change in ΔL3SMA greater than 2% per day. Multivariable logistic regression was used to examine the association between UCR or ΔUCR and rapid muscle loss. The area under the receiver operating characteristic curve (AUC) was calculated to assess the predictive performance of UCR or ΔUCR for rapid muscle loss.

RESULTS

Of the 482 patients, 141 (29.2%) experienced rapid muscle loss during their ICU stay. Multivariable logistic regression analysis revealed that ΔUCR was significantly associated with an increased risk of rapid muscle loss, with an odds ratio (OR) of 1.02 [95% CI: 1.01, 1.02]. The AUC for ΔUCR in predicting rapid muscle loss was 0.76 [95% CI: 0.68-0.83], with a threshold value of 19.4 µmol urea/µmol creatinine for ΔUCR.

CONCLUSION

The results demonstrate that ΔUCR is independently associated with rapid muscle loss in patients with sepsis and the AUC of the ROC curve for the ability of ΔUCR to predict rapid muscle loss was 0.76. Though additional prospective data are needed, our results suggest that ΔUCR may be useful in the early identification of critically ill patients with sepsis at risk of rapid muscle loss.

The impact of a tailored nutrition intervention delivered for the duration of hospitalisation on daily energy delivery for patients with critical illness (INTENT): a phase II randomised controlled trial

BACKGROUND

Nutrition interventions commenced in ICU and continued through to hospital discharge have not been definitively tested in critical care to date. To commence a program of research, we aimed to determine if a tailored nutrition intervention delivered for the duration of hospitalisation delivers more energy than usual care to patients initially admitted to the Intensive Care Unit (ICU).

METHODS

A multicentre, unblinded, parallel-group, phase II trial was conducted in twenty-two hospitals in Australia and New Zealand. Adult patients, requiring invasive mechanical ventilation (MV) for 72-120 h within ICU, and receiving < 80% estimated energy requirements from enteral nutrition (EN) were included. The intervention (tailored nutrition) commenced in ICU and included EN and supplemental parenteral nutrition (PN), and EN, PN, and/or oral nutrition after liberation from MV, and was continued until hospital discharge or study day 28. The primary outcome was daily energy delivery from nutrition (kcal). Secondary outcomes included duration of hospital stay, ventilator free days at day 28 and total blood stream infection rate.

MAIN RESULTS

The modified intention to treat analysis included 237 patients (n = 119 intervention and n = 118 usual care). Baseline characteristics were balanced; the median [interquartile range] intervention period was 19 [14-35] and 19 [13-32] days in the tailored nutrition and usual care groups respectively. Energy delivery was 1796 ± 31 kcal/day (tailored nutrition) versus 1482 ± 32 kcal/day (usual care)-adjusted mean difference 271 kcal/day, 95% CI 189-354 kcal. No differences were observed in any secondary outcomes.

CONCLUSIONS

A tailored nutrition intervention commenced in the ICU and continued until hospital discharge achieved a significant increase in energy delivery over the duration of hospitalisation for patients initially admitted to the ICU. Trial registration ClinicalTrials.gov Identifier NCT03292237 . First registered 25th September 2017. Last updated 10th Feb 2023.

Dietary protein in the ICU in relation to health outcomes

PURPOSE OF REVIEW

Critical care nutrition guidelines recommend provision of higher protein doses than recommended in health. These recommendations have been predominately based on lower quality evidence and physiological rationale that greater protein doses may attenuate the significant muscle loss observed in critically ill patients. This review discusses the mechanistic action of protein in the critically ill, details results from recent trials on health outcomes, discusses considerations for interpretation of trial results, and provides an overview of future directions.

RECENT FINDINGS

Two recent large clinical trials have investigated different protein doses and the effect on clinical outcome. Important findings revealed potential harm in certain sub-groups of patients. This harm must be balanced with the potential for beneficial effects on muscle mass and physical function given that two recent systematic reviews with meta-analyses demonstrated attenuation of muscle loss with higher protein doses. Utilizing biological markers such as urea: creatinine ratio or urea levels may prove useful in monitoring harm from higher protein doses.

SUMMARY

Future research should focus on prospectively investigating biological signatures of harm as well as taking into the consideration elements that will likely enhance the effectiveness of protein dose.

Personalized Nutrition in the Pediatric ICU: Steering the Shift from Acute Stress to Metabolic Recovery and Rehabilitation

BACKGROUND

Nutrition significantly impacts the outcomes of critically ill children in intensive care units (ICUs). Due to the evolving metabolic, neuroendocrine, and immunological disorders associated with severe illness or trauma, there are dynamically changing phases of energy needs requiring tailored macronutrient intake.

OBJECTIVES

This study aims to assess the changing dietary needs from the acute phase through recovery, provide recommendations for implementing evidence-based strategies to ensure adequate energy and nutrient provision in pediatric ICUs, and optimize patient outcomes.

METHODS

A comprehensive search of the MEDLINE-PubMed database was conducted, focusing on randomized controlled trials, meta-analyses, and systematic reviews related to the nutrition of critically ill children. The study highlights recent guidelines using the GRADE approach, supplemented by relevant adult studies, current clinical practices, challenges, gaps in knowledge, and future directions for research aimed at improving nutritional interventions.

RESULTS

Early personalized, incremental enteral feeding helps mitigate the negative energy balance during the acute phase, aids organ function restoration in the stabilization phase, and supports growth during the recovery phase and beyond. Conversely, early full nutritional support, high protein doses, or isolated micronutrient administration have not demonstrated benefits due to anabolic resistance in these patients. Moreover, early parenteral nutrition during the acute phase may suppress autophagy and lead to worse outcomes. Accurate assessment of nutritional status and monitoring of daily energy and protein needs are crucial.

CONCLUSIONS

Strong evidence supports the establishment of a dedicated nutritional team and the implementation of individualized nutritional protocols in the ICU to reduce morbidity and mortality in critically ill children.

A systematic review to assess the impact of amino acids or their derivatives on skeletal muscle wasting in critically ill patients

BACKGROUND

It is plausible that supplementation with specific amino acids or metabolites could attenuate skeletal muscle wasting during critical illness. The aim of this systematic review was to explore if amino acids or their derivatives impact skeletal muscle wastage in critically ill adults.

METHODS

Four databases were systematically searched to identify randomised control trials which delivered enteral supplemental amino acids, or their metabolites compared with placebo, standard care or no intervention, to critically ill patients and reported outcomes of skeletal muscle mass, plasma amino acids, nitrogen balance, or muscle strength. Two authors independently completed screening, data extraction, and risk of bias assessment using the Cochrane Risk of Bias 2 Tool. A meta-analysis was planned but heterogeneity in the type of intervention used and outcome assessment precluded this. Therefore, data were synthesised using vote counting.

RESULTS

Thirty randomised control trials, comprising 1976 patients were included. The most frequently studied interventional amino acid or metabolite was glutamine (n = 12 trials), a combination (n = 9), arginine (n = 6), β-hydroxy β-methylbutyrate (HMB) (n = 2) or ornithine (n = 1). Six trials (including 284 participants) measured skeletal muscle following supplementation, four of which used HMB alone or in combination as the intervention. Of these, one trial observed an attenuation of muscle wasting with a combination of amino acids, one observed an exacerbation of muscle wasting with HMB, three trials observed no impact on muscle wasting with HMB or a combination of amino acids and one trial reported no information.

CONCLUSION

Six trials have investigated the effect of enteral amino acid or amino acid metabolite supplementation on muscle mass in critically ill. Heterogeneity of interventions, outcome assessments and direction of effects limits the certainty regarding the effect of supplemental amino acids, or their metabolites, on skeletal muscle wasting during critical illness. The trial protocol is registered on PROSPERO (CRD42021275989).

Dietary protein splanchnic uptake and digestibility via stable isotope tracers

PURPOSE OF REVIEW

Dietary proteins are broken down into peptides across the gastrointestinal tract, with skeletal muscle being a primary deposition site for amino acids in the form of incorporation into, for example, metabolic and structural proteins. It follows that key research questions remain as to the role of amino acid bioavailability, of which protein digestibility and splanchnic sequestration (absorption and utilization) of amino acids are determining factors, impact upon muscle protein synthesis (MPS) in clinical states.

RECENT FINDINGS

Elevated splanchnic amino acid uptake has been implicated in anabolic resistance (i.e. attenuated anabolic responses to protein intake) observed in ageing, though it is unclear whether this limits MPS. The novel 'dual stable isotope tracer technique' offers a promising, minimally invasive approach to quantify the digestion of any protein source(s). Current work is focused on the validation of this technique against established methods, with scope to apply this to clinical and elderly populations to help inform mechanistic and interventional insights.

SUMMARY

Considerations should be made for all facets of protein quality; digestibility of the protein, absorption/utilization and subsequent peripheral bioavailability of amino acids, and resultant stimulation of MPS. Stable isotope tracer techniques offer a minimally invasive approach to achieve this, with wide-ranging clinical application.

Nutrition delivery and the relationship with changes in muscle mass in adult patients receiving extracorporeal membrane oxygenation: A retrospective observational study

BACKGROUND

Adverse changes in muscle health (size and quality) are common in patients receiving extracorporeal membrane oxygenation (ECMO). Nutrition delivery may attenuate such changes, yet the relationship with muscle health remains poorly understood. This study explored the association between energy and protein delivery and changes in muscle health measured using ultrasound from baseline to day 10 and 20 in patients receiving ECMO.

METHODS

A secondary analysis of data from a prospective study quantifying changes in muscle health using ultrasound in adults receiving ECMO was completed. Patients were eligible for inclusion if they were prescribed artificial nutrition within 3 days of enrolment and had >1 ultrasound measurement. The primary outcome was the association between protein delivery (grams delivered and percentage of targets received) and change in rectus femoris cross-sectional area (RF-CSA) till day 20. Secondary outcomes were the association between energy and protein delivery and change in RF-CSA till day 10, RF-echogenicity, and quadriceps muscle layer thickness to day 10 and 20. Associations were assessed using Spearman's rank correlation.

RESULTS

Twenty-three patients (age: 48 [standard deviation {SD}: 14], 44% male) were included. Mean energy and protein delivery were 1633 kcal (SD: 374 kcal) and 70 g (SD: 17 g) equating to 79% (SD: 19%) of energy and 73% (SD: 17%) of protein targets. No association was observed between protein delivery (r = 0.167; p = 0.495) or the percentage of targets received (r = 0.096; p = 0.694) and change in RF-CSA till day 20. No other significant associations were found between energy or protein delivery and change in RF-CSA, echogenicity, or quadriceps muscle layer thickness at any time point.

CONCLUSIONS

This exploratory study observed no association between nutrition delivery and changes in muscle health measured using ultrasound in patients receiving ECMO. Larger prospective studies are required to investigate the association between nutrition delivery and changes in muscle health in patients receiving ECMO.

Nutrition considerations for patients with persistent critical illness: A narrative review

Critically ill patients experience high rates of malnutrition and significant muscle loss during their intensive care unit (ICU) admission, impacting recovery. Nutrition is likely to play an important role in mitigating the development and progression of malnutrition and muscle loss observed in ICU, yet definitive clinical trials of nutrition interventions in ICU have failed to show benefit. As improvements in the quality of medical care mean that sicker patients are able to survive the initial insult, combined with an aging and increasingly comorbid population, it is anticipated that ICU length of stay will continue to increase. This review aims to discuss nutrition considerations unique to critically ill patients who have persistent critical illness, defined as an ICU stay of >10 days. A discussion of nutrition concepts relevant to patients with persistent critical illness will include energy and protein metabolism, prescription, and delivery; monitoring of nutrition at the bedside; and the role of the healthcare team in optimizing nutrition support.

A review of perioperative immune-modulating and metabolic-modulating nutrition strategies for bowel resection surgery

Focused perioperative nutrition strategies have proven benefits on the outcomes for patients undergoing major abdominal surgery. In this brief article, we will review these strategies and the evidence to support them with a focus on gastrointestinal anastomotic healing. We will elaborate the risks and benefits of enteral feeds, immune- and metabolic-modulating formulas, prebiotics and probiotics, and prehabilitation in preparation for surgery. Additionally, we will discuss the role of fish oils (eicosapentaenoic acid and docosahexaenoic acid) in the surgical patient and new data on specialized proresolving mediators in inflammation resolution. Finally, this article will consider the harmful impact surgical trauma has on the microbiome and the potential for perioperative dietary modulation to attenuate these negative effects.

The Association Between Malnutrition and High Protein Treatment on Outcomes in Critically Ill Patients: A Post Hoc Analysis of the EFFORT Protein Randomized Trial

BACKGROUND

Preexisting malnutrition in critically ill patients is associated with adverse clinical outcomes. Malnutrition can be diagnosed with the Global Leadership Initiative on Malnutrition using parameters such as weight loss, muscle wasting, and BMI. International critical care nutrition guidelines recommend high protein treatment to improve clinical outcomes in critically ill patients diagnosed with preexisting malnutrition. However, this recommendation is based on expert opinion.

RESEARCH QUESTION

In critically ill patients, what is the association between preexisting malnutrition and time to discharge alive (TTDA), and does high protein treatment modify this association?

STUDY DESIGN AND METHODS

This multicenter randomized controlled trial involving 16 countries was designed to investigate the effects of high vs usual protein treatment in 1,301 critically ill patients. The primary outcome was TTDA. Multivariable regression was used to identify if preexisting malnutrition was associated with TTDA and if protein delivery modified their association.

RESULTS

The prevalence of preexisting malnutrition was 43.8%, and the cumulative incidence of live hospital discharge by day 60 was 41.2% vs 52.9% in the groups with and without preexisting malnutrition, respectively. The average protein delivery in the high vs usual treatment groups was 1.6 g/kg per day vs 0.9 g/kg per day. Preexisting malnutrition was independently associated with slower TTDA (adjusted hazard ratio, 0.81; 95% CI, 0.67-0.98). However, high protein treatment in patients with and without preexisting malnutrition was not associated with TTDA (adjusted hazard ratios of 0.84 [95% CI, 0.63-1.11] and 0.97 [95% CI, 0.77-1.21]). Furthermore, no effect modification was observed (ratio of adjusted hazard ratio, 0.84; 95% CI, 0.58-1.20).

INTERPRETATION

Malnutrition was associated with slower TTDA, but high protein treatment did not modify the association. These findings challenge current international critical care nutrition guidelines.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT03160547; URL: www.

CLINICALTRIALS

gov.

Plasma beta-hydroxy-beta-methylbutyrate availability after enteral administration during critical illness after trauma: An exploratory study

BACKGROUND

During critical illness skeletal muscle wasting occurs rapidly. Although beta-hydroxy-beta-methylbutyrate (HMB) is a potential treatment to attenuate this process, the plasma appearance and muscle concentration is uncertain.

METHODS

This was an exploratory study nested within a blinded, parallel group, randomized clinical trial in which critically ill patients after trauma received enteral HMB (3 g daily) or placebo. Plasma samples were collected at 0, 60, and 180 min after study supplement administration on day 1. Needle biopsies of the vastus lateralis muscle were collected (baseline and day 7 of the HMB treatment intervention period). An external standard curve was used to calculate HMB concentrations in plasma and muscle.

RESULTS

Data were available for 16 participants (male n = 12 (75%), median [interquartile range] age 50 [29-58] years) who received placebo and 18 participants (male n = 14 (78%), age 49 [34-55] years) who received HMB. Plasma HMB concentrations were similar at baseline but increased after HMB (T = 60 min: placebo 0.60 [0.44-1.31]  µM; intervention 51.65 [22.76-64.72]  µM). Paired muscle biopsies were collected from 11 participants (placebo n = 7, HMB n = 4). Muscle HMB concentrations were similar at baseline between groups (2.35 [2.17-2.95]; 2.07 [1.78-2.31] µM). For participants in the intervention group who had the repeat biopsy within 4 h of HMB administration, concentrations were greater (7.2 and 12.3 µM) than those who had the repeat biopsy >4 h after HMB (2.7 and 2.1 µM).

CONCLUSION

In this exploratory study, enteral HMB administration increased plasma HMB availability. The small sample size limits interpretation of the muscle HMB findings.

Critical illness-associated limb and diaphragmatic weakness

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on the diagnosis, prevention and treatment of critical illness weakness (CIW) and critical illness associated diaphragmatic weakness (CIDW).

RECENT FINDINGS

In the ICU, several risk factors can lead to CIW and CIDW. Recent evidence suggests that they have different pathophysiological mechanisms and impact on outcomes, although they share common risk factors and may overlap in several patients. Their diagnosis is challenging, because CIW diagnosis is primarily clinical and, therefore, difficult to obtain in the ICU population, and CIDW diagnosis is complex and not easily performed at the bedside. All of these issues lead to underdiagnosis of CIW and CIDW, which significantly increases the risk of complications and the impact on both short and long term outcomes. Moreover, recent studies have explored promising diagnostic techniques that are may be easily implemented in daily clinical practice. In addition, this review summarizes the latest research aimed at improving how to prevent and treat CIW and CIDW.

SUMMARY

This review aims to clarify some uncertain aspects and provide helpful information on developing monitoring techniques and therapeutic interventions for managing CIW and CIDW.

Persistent inflammation, immunosuppression, and catabolism syndrome (PICS): a review of definitions, potential therapies, and research priorities

Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS) is a clinical endotype of chronic critical illness. PICS consists of a self-perpetuating cycle of ongoing organ dysfunction, inflammation, and catabolism resulting in sarcopenia, immunosuppression leading to recurrent infections, metabolic derangements, and changes in bone marrow function. There is heterogeneity regarding the definition of PICS. Currently, there are no licensed treatments specifically for PICS. However, findings can be extrapolated from studies in other conditions with similar features to repurpose drugs, and in animal models. Drugs that can restore immune homeostasis by stimulating lymphocyte production could have potential efficacy. Another treatment could be modifying myeloid-derived suppressor cell (MDSC) activation after day 14 when they are immunosuppressive. Drugs such as interleukin (IL)-1 and IL-6 receptor antagonists might reduce persistent inflammation, although they need to be given at specific time points to avoid adverse effects. Antioxidants could treat the oxidative stress caused by mitochondrial dysfunction in PICS. Possible anti-catabolic agents include testosterone, oxandrolone, IGF-1 (insulin-like growth factor-1), bortezomib, and MURF1 (muscle RING-finger protein-1) inhibitors. Nutritional support strategies that could slow PICS progression include ketogenic feeding and probiotics. The field would benefit from a consensus definition of PICS using biologically based cut-off values. Future research should focus on expanding knowledge on underlying pathophysiological mechanisms of PICS to identify and validate other potential endotypes of chronic critical illness and subsequent treatable traits. There is unlikely to be a universal treatment for PICS, and a multimodal, timely, and personalised therapeutic strategy will be needed to improve outcomes for this growing cohort of patients.

Administration of Free Amino Acids Improves Exogenous Amino Acid Availability when Compared with Intact Protein in Critically Ill Patients: A Randomized Controlled Study

BACKGROUND

Protein digestion and amino acid absorption appear compromised in critical illness. The provision of enteral feeds with free amino acids rather than intact protein may improve postprandial amino acid availability.

OBJECTIVE

Our objective was to quantify the uptake of diet-derived phenylalanine after the enteral administration of intact protein compared with an equivalent amount of free amino acids in critically ill patients.

METHODS

Sixteen patients who were mechanically ventilated in intensive care unit (ICU) at risk of malabsorption received a primed continuous infusion of L-[ring-2H5]-phenylalanine and L-[ring-3,5-2H2]-tyrosine after an overnight fast. Patients were randomly allocated to receive 20 g intrinsically L-[1-13C]-phenylalanine-labeled milk protein or an equivalent amount of amino acids labeled with free L-[1-13C]-phenylalanine via a nasogastric tube over a 2-h period. Protein digestion and amino acid absorption kinetics and whole-body protein net balance were assessed throughout a 6-h period.

RESULTS

After enteral nutrient infusion, both plasma phenylalanine and leucine concentrations increased (P-time < 0.001), with a more rapid and greater rise after free amino acid compared with intact protein administration (P-time × treatment = 0.003). Diet-derived phenylalanine released into the circulation was 25% greater after free amino acids compared with intact protein administration [68.7% (confidence interval {CI}: 62.3, 75.1%) compared with 43.8% (CI: 32.4, 55.2%), respectively; P < 0.001]. Whole-body protein net balance became positive after nutrient administration (P-time < 0.001) and tended to be more positive after free amino acid in provision (P-time × treatment = 0.07).

CONCLUSIONS

The administration of free amino acids as opposed to intact protein further increases postprandial plasma amino acid availability in critically ill patients, allowing more diet-derived phenylalanine to become available to peripheral tissues. This trial was registered at clinicaltrials.gov as NCT04791774.

Combining proteins with n-3 PUFAs (EPA + DHA) and their inflammation pro-resolution mediators for preservation of skeletal muscle mass

The optimal feeding strategy for critically ill patients is still debated, but feeding must be adapted to individual patient needs. Critically ill patients are at risk of muscle catabolism, leading to loss of muscle mass and its consequent clinical impacts. Timing of introduction of feeding and protein targets have been explored in recent trials. These suggest that "moderate" protein provision (maximum 1.2 g/kg/day) is best during the initial stages of illness. Unresolved inflammation may be a key factor in driving muscle catabolism. The omega-3 (n-3) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are substrates for synthesis of mediators termed specialized pro-resolving mediators or SPMs that actively resolve inflammation. There is evidence from other settings that high-dose oral EPA + DHA increases muscle protein synthesis, decreases muscle protein breakdown, and maintains muscle mass. SPMs may be responsible for some of these effects, especially upon muscle protein breakdown. Given these findings, provision of EPA and DHA as part of medical nutritional therapy in critically ill patients at risk of loss of muscle mass seems to be a strategy to prevent the persistence of inflammation and the related anabolic resistance and muscle loss.

High protein intake and nitrogen balance in patients receiving venovenous extracorporeal membrane oxygenation: A descriptive cohort study

BACKGROUND

This retrospective cohort study sought to describe the ability of high protein regimens to achieve nitrogen equilibrium in patients receiving venovenous extracorporeal membrane oxygenation (VV ECMO).

METHODS

Patients aged ≥18 years with a documented nitrogen balance study (NB) on VV ECMO between February 2018 and December 2021 were included. Studies with incomplete 24-h urine collections or changes in blood urea nitrogen ≥10 mg/dl were excluded. Data were summarized, correlation between first NB and potentially contributing variables was assessed with Kendall tau. Subanalysis described findings after stratifying for weight class (obese vs nonobese) and duration of VV ECMO at the time of NB.

RESULTS

A total of 68 NBs in 30 patients were included; 47% of the cohort had obesity. The number of NBs per patient was 2.2 ± 1.1, which were completed on a median of 31.5 (interquartile range: 16, 53.8) days receiving ECMO. Nitrogen equilibrium or positive balance was achieved in 72% of studies despite elevated nitrogen excretion. Patients received 87.9 ± 16.8% of prescribed protein on NB days for average intakes of 2.4 ± 0.4 g/kg of actual weight per day and 2.4 ± 0.5 g/kg of ideal weight per day in patients without and with obesity. Median NB in patients without obesity was -1.46 (-8.96, 2.98) g/day and -0.21 (-10.58, 4.04) g/day in patients with obesity. A difference in median NB after stratification for timing was observed (P = 0.029).

CONCLUSION

Nitrogen equilibrium can be achieved with high protein intake in adults receiving VV ECMO. NB monitoring is one tool to individualize protein prescriptions throughout the course of VV ECMO.

Association between urea trajectory and protein dose in critically ill adults: a secondary exploratory analysis of the effort protein trial (RE-EFFORT)

BACKGROUND

Delivering higher doses of protein to mechanically ventilated critically ill patients did not improve patient outcomes and may have caused harm. Longitudinal urea measurements could provide additional information about the treatment effect of higher protein doses. We hypothesised that higher urea values over time could explain the potential harmful treatment effects of higher doses of protein.

METHODS

We conducted a reanalysis of a randomised controlled trial of higher protein doses in critical illness (EFFORT Protein). We applied Bayesian joint models to estimate the strength of association of urea with 30-day survival and understand the treatment effect of higher protein doses.

RESULTS

Of the 1301 patients included in EFFORT Protein, 1277 were included in this analysis. There were 344 deaths at 30 days post-randomisation. By day 6, median urea was 2.1 mmol/L higher in the high protein group (95% CI 1.1-3.2), increasing to 3.0 mmol/L (95% CI 1.3-4.7) by day 12. A twofold rise in urea was associated with an increased risk of death at 30 days (hazard ratio 1.34, 95% credible interval 1.21-1.48), following adjustment of baseline characteristics including age, illness severity, renal replacement therapy, and presence of AKI. This association persisted over the duration of 30-day follow-up and in models adjusting for evolution of organ failure over time.

CONCLUSIONS

The increased risk of death in patients randomised to a higher protein dose in the EFFORT Protein trial was estimated to be mediated by increased urea cycle activity, of which serum urea is a biological signature. Serum urea should be taken into consideration when initiating and continuing protein delivery in critically ill patients.

CLINICALTRIALS

gov Identifier: NCT03160547 (2017-05-17).

Nasogastric bolus administration of a protein-rich drink augments insulinaemia and aminoacidaemia but not whole-body protein turnover or muscle protein synthesis versus oral administration

Nasogastric feeding of protein-rich liquids is a nutritional support therapy that attenuates muscle mass loss. However, whether administration via a nasogastric tube per se augments whole-body or muscle protein anabolism compared with oral administration is unknown. Healthy participants were administered a protein-rich drink (225 ml containing 21 g protein) orally (ORAL; n=13; age 21 ± 1 year; BMI 22.2 ± 0.6 kg·m-2) or via a nasogastric tube (NG; n=13; age 21 ± 1 yr; BMI 23.9 ± 0.9 kg·m-2) in a parallel group design, balanced for sex. L-[ring-2H5]-phenylalanine and L-[3,3-2H2]-tyrosine were infused to measure postabsorptive and postprandial whole-body protein turnover. Skeletal muscle biopsies were collected at -120, 0, 120 and 300 min relative to drink administration to quantify temporal myofibrillar fractional synthetic rates (myoFSR). Drink administration increased serum insulin and plasma amino acid concentrations, and to a greater extent and duration in NG versus ORAL (all interactions P<0.05). Drink administration increased whole-body protein synthesis (P<0.01), suppressed protein breakdown (P<0.001), and created positive net protein balance (P<0.001), but to a similar degree in ORAL and NG (interactions P>0.05). Drink administration increased myoFSR from the postabsorptive state (P<0.01), regardless of route of administration in ORAL and in NG (interaction P>0.05). Nasogastric bolus administration of a protein-rich drink induces insulinaemia and aminoacidaemia to a greater extent than oral administration, but the postprandial increase in whole-body protein turnover and muscle protein synthesis was equivalent between administration routes. Nasogastric administration is a potent intervention to increase postprandial amino acid availability. Future work should assess its utility in overcoming impaired sensitivity to protein feeding, such as that seen in ageing, disuse, and critical care.

The effects of higher versus lower protein delivery in critically ill patients: an updated systematic review and meta-analysis of randomized controlled trials with trial sequential analysis

BACKGROUND

A recent large multicentre trial found no difference in clinical outcomes but identified a possibility of increased mortality rates in patients with acute kidney injury (AKI) receiving higher protein. These alarming findings highlighted the urgent need to conduct an updated systematic review and meta-analysis to inform clinical practice.

METHODS

From personal files, citation searching, and three databases searched up to 29-5-2023, we included randomized controlled trials (RCTs) of adult critically ill patients that compared higher vs lower protein delivery with similar energy delivery between groups and reported clinical and/or patient-centred outcomes. We conducted random-effect meta-analyses and subsequently trial sequential analyses (TSA) to control for type-1 and type-2 errors. The main subgroup analysis investigated studies with and without combined early physical rehabilitation intervention. A subgroup analysis of AKI vs no/not known AKI was also conducted.

RESULTS

Twenty-three RCTs (n = 3303) with protein delivery of 1.49 ± 0.48 vs 0.92 ± 0.30 g/kg/d were included. Higher protein delivery was not associated with overall mortality (risk ratio [RR]: 0.99, 95% confidence interval [CI] 0.88-1.11; I2 = 0%; 21 studies; low certainty) and other clinical outcomes. In 2 small studies, higher protein combined with early physical rehabilitation showed a trend towards improved self-reported quality-of-life physical function measurements at day-90 (standardized mean difference 0.40, 95% CI - 0.04 to 0.84; I2 = 30%). In the AKI subgroup, higher protein delivery significantly increased mortality (RR 1.42, 95% CI 1.11-1.82; I2 = 0%; 3 studies; confirmed by TSA with high certainty, and the number needed to harm is 7). Higher protein delivery also significantly increased serum urea (mean difference 2.31 mmol/L, 95% CI 1.64-2.97; I2 = 0%; 7 studies).

CONCLUSION

Higher, compared with lower protein delivery, does not appear to affect clinical outcomes in general critically ill patients but may increase mortality rates in patients with AKI. Further investigation of the combined early physical rehabilitation intervention in non-AKI patients is warranted.

PROSPERO ID

CRD42023441059.

Protein and energy intake in intensive care unit survivors during the first year of recovery: A descriptive cohort study

BACKGROUND

Many intensive care unit (ICU) survivors suffer long-term health issues that affect their quality of life. Nutrition inadequacy can limit their rehabilitation potential. This study investigates nutrition intake and support during ICU admission and recovery.

METHODS

In this prospective cohort study, 81 adult ICU patients with stays ≥48 h were included. Data on dietary intake, feeding strategies, baseline and ICU characteristics, and 1-year outcomes (physical health and readmission rates) were collected. The number of patients achieving 1.2 gram per kilogram per day of protein and 25 kilocalories per kilogram per day at 3 months, 6 months, and 12 months after ICU admission was recorded. The impact of dietary supplementation during the year was assessed. Baseline characteristics, intake barriers, and rehabilitation's influence on nutrition intake at 12 months were evaluated, along with the effect of inadequate intake on outcomes.

RESULTS

After 12 months, only 10% of 60 patients achieved 1.2 g/kg/day protein intake, whereas 28% reached the advised 25 kcal/kg/day energy target. Supplementary feeding significantly increased protein intake at 3, 6, and 12 months (P = 0.003, P = 0.012, and P = 0.033, respectively) and energy intake at 3 months (P = 0.003). A positive relation was found between female sex and energy intake at 12 months after ICU admission (β = 4.145; P = 0.043) and taste issues were independently associated with higher protein intake (β = 0.363; P = 0.036). However, achieving upper-quartile protein or energy intake did not translate into improved physical health outcomes.

CONCLUSION

Continuous and improved nutrition care is urgently needed to support patients in reaching nutrition adequacy.

Amino acid kinetics in the critically ill

PURPOSE OF REVIEW

Stable isotope methods have been used for many years to assess whole body protein and amino acid kinetics in critically ill patients. In recent years, new isotope approaches and tracer insights have been developed. The tracer pulse approach has some advantages above the established primed-continuous tracer infusion approach because of the high amount of metabolic information obtained, easy applicability, and low tracer costs. Effects of disease severity and sex on amino acid kinetics in ICU patients will also be addressed.

RECENT FINDINGS

Current knowledge was synthesized on specific perturbations in amino acid metabolism in critically ill patients, employing novel methodologies such as the pulse tracer approach and computational modeling. Variations were evaluated in amino acid production and linked to severity of critical illness, as measured by SOFA score, and sex. Production of the branched-chain amino acids (BCAAs), glutamine, tau-methylhistidine and hydroxyproline were elevated in critical illness, likely related to increased transamination of the individual BCAAs or increased breakdown of proteins. Citrulline production was reduced, indicative of impaired gut mucosa function. Sex and disease severity independently influenced amino acid kinetics in ICU patients.

SUMMARY

Novel tracer and computational approaches have been developed to simultaneously measure postabsorptive kinetics of multiple amino acids that can be used in critical illness. The collective findings lay the groundwork for targeted individualized nutritional strategies in ICU settings aimed at enhancing patient outcomes taking into account disease severity and sex.

A pilot study of alternative substrates in the critically Ill subject using a ketogenic feed

Bioenergetic failure caused by impaired utilisation of glucose and fatty acids contributes to organ dysfunction across multiple tissues in critical illness. Ketone bodies may form an alternative substrate source, but the feasibility and safety of inducing a ketogenic state in physiologically unstable patients is not known. Twenty-nine mechanically ventilated adults with multi-organ failure managed on intensive care units were randomised (Ketogenic n = 14, Control n = 15) into a two-centre pilot open-label trial of ketogenic versus standard enteral feeding. The primary endpoints were assessment of feasibility and safety, recruitment and retention rates and achievement of ketosis and glucose control. Ketogenic feeding was feasible, safe, well tolerated and resulted in ketosis in all patients in the intervention group, with a refusal rate of 4.1% and 82.8% retention. Patients who received ketogenic feeding had fewer hypoglycaemic events (0.0% vs. 1.6%), required less exogenous international units of insulin (0 (Interquartile range 0-16) vs.78 (Interquartile range 0-412) but had slightly more daily episodes of diarrhoea (53.5% vs. 42.9%) over the trial period. Ketogenic feeding was feasible and may be an intervention for addressing bioenergetic failure in critically ill patients. Clinical Trials.gov registration: NCT04101071.

A systematic review and meta-analysis of the clinimetric properties of the core outcome measurement instruments for clinical effectiveness trials of nutritional and metabolic interventions in critical illness (CONCISE)

BACKGROUND

CONCISE is an internationally agreed minimum set of outcomes for use in nutritional and metabolic clinical research in critically ill adults. Clinicians and researchers need to be aware of the clinimetric properties of these instruments and understand any limitations to ensure valid and reliable research. This systematic review and meta-analysis were undertaken to evaluate the clinimetric properties of the measurement instruments identified in CONCISE.

METHODS

Four electronic databases were searched from inception to December 2022 (MEDLINE via Ovid, EMBASE via Ovid, CINAHL via Healthcare Databases Advanced Search, CENTRAL via Cochrane). Studies were included if they examined at least one clinimetric property of a CONCISE measurement instrument or recognised variation in adults ≥ 18 years with critical illness or recovering from critical illness in any language. The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist for systematic reviews of Patient-Reported Outcome Measures was used. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were used in line with COSMIN guidance. The COSMIN checklist was used to evaluate the risk of bias and the quality of clinimetric properties. Overall certainty of the evidence was rated using a modified Grading of Recommendations, Assessment, Development and Evaluation approach. Narrative synthesis was performed and where possible, meta-analysis was conducted.

RESULTS

A total of 4316 studies were screened. Forty-seven were included in the review, reporting data for 12308 participants. The Short Form-36 Questionnaire (Physical Component Score and Physical Functioning), sit-to-stand test, 6-m walk test and Barthel Index had the strongest clinimetric properties and certainty of evidence. The Short Physical Performance Battery, Katz Index and handgrip strength had less favourable results. There was limited data for Lawson Instrumental Activities of Daily Living and the Global Leadership Initiative on Malnutrition criteria. The risk of bias ranged from inadequate to very good. The certainty of the evidence ranged from very low to high.

CONCLUSIONS

Variable evidence exists to support the clinimetric properties of the CONCISE measurement instruments. We suggest using this review alongside CONCISE to guide outcome selection for future trials of nutrition and metabolic interventions in critical illness.

TRIAL REGISTRATION

PROSPERO (CRD42023438187). Registered 21/06/2023.

The metabolic effects of intermittent versus continuous feeding in critically ill patients

Intermittent (or bolus) feeding regimens in critically ill patients have been of increasing interest to clinicians and scientists. Changes in amino acid, fat and carbohydrate metabolites over time might yet deliver other benefits (e.g. modulation of the circadian rhythm and sleep, and impacts on ghrelin secretion, insulin resistance and autophagy). We set out to characterise these changes in metabolite concentration. The Intermittent versus Continuous Feeding in Critically Ill paitents study (NCT02358512) was an eight-centre single-blinded randomised controlled trial. Patients were randomised to received a continuous (control arm) or intermittent (6x/day, intervention arm) enteral feeding regimen. Blood samples were taken on trial days 1, 7 and 10 immediately before and 30 min after intermittent feeds, and at equivalent timepoints in the control arm. A pre-planned targeted metabolomic analysis was performend using Nuclear Resonance Spectroscopy. Five hundred and ninety four samples were analysed from 75 patients. A total of 24 amino acid-, 19 lipid based-, and 44 small molecule metabolite features. Across the main two axes of variation (40-60% and 6-8% of variance), no broad patterns distinguished between intermittent or continuous feeding arms, across intra-day sampling times or over the 10 days from initial ICU admission. Logfold decreases in abundance were seen in metabolites related to amino acids (Glutamine - 0.682; Alanine - 0.594), ketone body metabolism (Acetone - 0.64; 3-Hydroxybutyric Acid - 0.632; Acetonacetic Acid - 0.586), fatty acid (carnitine - 0.509) and carbohydrate metabolism ( Maltose - 0.510; Citric Acid - 0.485). 2-3 Butanediol, a by-product of sugar-fermenting microbial metabolism also decreased (- 0.489). No correlation was seen with change in quadriceps muscle mass for any of the 20 metabolites varying with time (all p > 0.05). Increasing severity of organ failure was related to increasing ketone body metabolism (3 Hydroxybutyric Acid-1 and - 3; p = 0.056 and p = 0.014), carnitine deficiency (p = 0.002) and alanine abundancy (p - 0.005). A 6-times a day intermittent feeding regimen did not alter metabolite patterns across time compared to continuous feeding in critically ill patients, either within a 24 h period or across 10 days of intervention. Future research on intermittent feeding regimens should focus on clinical process benefits, or extended gut rest and fasting.

Inflammation and altered metabolism impede efficacy of functional electrical stimulation in critically ill patients

BACKGROUND

Critically ill patients suffer from acute muscle wasting, which is associated with significant physical functional impairment. We describe data from nested muscle biopsy studies from two trials of functional electrical stimulation (FES) that did not shown improvements in physical function.

METHODS

Primary cohort: single-centre randomized controlled trial. Additional healthy volunteer data from patients undergoing elective hip arthroplasty. Validation cohort: Four-centre randomized controlled trial.

INTERVENTION

FES cycling for 60-90min/day.

ANALYSES

Skeletal muscle mRNA expression of 223 genes underwent hierarchal clustering for targeted analysis and validation.

RESULTS

Positively enriched pathways between healthy volunteers and ICU participants were "stress response", "response to stimuli" and "protein metabolism", in keeping with published data. Positively enriched pathways between admission and day 7 ICU participants were "FOXO-mediated transcription" (admission = 0.48 ± 0.94, day 7 = - 0.47 ± 1.04 mean log2 fold change; P = 0.042), "Fatty acid metabolism" (admission = 0.50 ± 0.67, day 7 = 0.07 ± 1.65 mean log2 fold change; P = 0.042) and "Interleukin-1 processing" (admission = 0.88 ± 0.50, day 7 = 0.97 ± 0.76 mean log2 fold change; P = 0.054). Muscle mRNA expression of UCP3 (P = 0.030) and DGKD (P = 0.040) decreased in both cohorts with no between group differences. Changes in IL-18 were not observed in the validation cohort (P = 0.268). Targeted analyses related to intramuscular mitochondrial substrate oxidation, fatty acid oxidation and intramuscular inflammation showed PPARγ-C1α; (P < 0.001), SLC25A20 (P = 0.017) and UCP3 (P < 0.001) decreased between admission and day 7 in both arms. LPIN-1 (P < 0.001) and SPT1 (P = 0.044) decreased between admission and day 7. IL-18 (P = 0.011) and TNFRSF12A (P = 0.009) increased in both arms between admission and day 7. IL-1β (P = 0.007), its receptor IL-1R1 (P = 0.005) and IL-6R (P = 0.001) decreased in both arms between admission and day 7. No between group differences were seen in any of these (all p > 0.05).

CONCLUSIONS

Intramuscular inflammation and altered substrate utilization are persistent in skeletal muscle during first week of critical illness and are not improved by the application of Functional Electrical Stimulation-assisted exercise. Future trials of exercise to prevent muscle wasting and physical impairment are unlikely to be successful unless these processes are addressed by other means than exercise alone.

Predictors of acute muscle loss in the intensive care unit: A secondary analysis of an in-bed cycling trial for critically ill patients

PURPOSE

The purpose of this study was to assist clinicians to identify critically ill patients at greatest risk of acute muscle loss and to analyse the associations between protein intake and exercise on acute muscle loss.

MATERIALS AND METHODS

Secondary analysis of a single-centre randomised clinical trial of in-bed cycling using a mixed effects model was undertaken to examine the association between key variables and rectus femoris cross-sectional area (RFCSA). Groups were combined, and key variables for the cohort were modified Nutrition Risk in the Critically Ill (mNUTRIC) scores within the first days following intensive care unit admission, longitudinal RFCSA measurements, percent of daily recommended protein intake, and group allocation (usual care, in-bed cycling). RFCSA ultrasound measurements were taken at baseline and days 3, 7, and 10 to quantify acute muscle loss. All patients received usual care nutritional intake while in the intensive care unit. Patients allocated to the cycling group commenced in-bed cycling once safety criteria were met.

RESULTS

Analysis included all 72 participants, of which 69% were male, with a mean (standard deviation) age of 56 (17) years. Patients received a mean (standard deviation) of 59% (26%) of the minimum protein dose recommended for critically ill patients. Mixed-effects model results indicated that patients with higher mNUTRIC scores experienced greater RFCSA loss (estimate = -0.41; 95% confidence interval [CI] = -0.59 to -0.23). RFCSA did not share a statistically significant association with cycling group allocation (estimate = -0.59, 95% CI = -1.53 to 0.34), the percentage of protein requirements received (estimate = -0.48; 95% CI = -1.16 to 0.19), or a combination of cycling group allocation and higher protein intake (estimate = 0.33, 95% CI = -0.76 to 1.43).

CONCLUSIONS AND RELEVANCE

We found that a higher mNUTRIC score was associated with greater muscle loss, but we did not observe a relationship between combined protein delivery and in-bed cycling and muscle loss. The low protein doses achieved may have impacted the potential for exercise or nutrition strategies to reduce acute muscle loss.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry (ACTRN 12616000948493).

Beta-hydroxy-beta-methylbutyrate supplementation and functional outcomes in multitrauma patients: A pilot randomized controlled trial

BACKGROUND

Beta-hydroxy-beta-methylbutyrate (HMB) is a nutrition supplement that may attenuate muscle wasting from critical illness. This trial aimed to determine feasibility of administering a blinded nutrition supplement in the intensive care unit (ICU) and continuing it after ICU discharge.

METHODS

Single-center, parallel-group, blinded, placebo-controlled, randomized feasibility trial. After traumatic injury necessitating admission to ICU, participants were randomized to receive an enteral study supplement of 3 g of HMB (intervention) or placebo daily for 28 days or until hospital discharge. Primary outcome was feasibility of administering the study supplement, quantified as protocol adherence. Secondary outcomes included change in quadriceps muscle thickness, measured weekly until day 28 or hospital discharge by using ultrasound and analyzed by using a linear mixed model.

RESULTS

Fifty randomized participants (intervention, n = 26; placebo, n = 24) showed comparable baseline characteristics. Participants received 862 (84.3%) of the 1022 prescribed supplements during hospitalization with 543 (62.8%) delivered via an enteral feeding tube. The median (IQR) number of study supplements successfully administered per participant was 19.5 (13.0-24.0) in the intervention group and 16.5 (8.5-23.5) in the placebo group. Marked loss of quadriceps muscle thickness occurred in both groups, with the point estimate favoring attenuated muscle loss with the intervention, albeit with wide CIs (mean intervention difference after 28 days, 0.26 cm [95% CI, -0.13 to 0.64]).

CONCLUSION

A blinded, placebo-controlled, randomized clinical trial of daily enteral HMB supplementation for up to 28 days in hospital is feasible. Any effect of HMB supplementation to attenuate muscle wasting after traumatic injury remains uncertain.

The impact of higher protein dosing on outcomes in critically ill patients with acute kidney injury: a post hoc analysis of the EFFORT protein trial

BACKGROUND

Based on low-quality evidence, current nutrition guidelines recommend the delivery of high-dose protein in critically ill patients. The EFFORT Protein trial showed that higher protein dose is not associated with improved outcomes, whereas the effects in critically ill patients who developed acute kidney injury (AKI) need further evaluation. The overall aim is to evaluate the effects of high-dose protein in critically ill patients who developed different stages of AKI.

METHODS

In this post hoc analysis of the EFFORT Protein trial, we investigated the effect of high versus usual protein dose (≥ 2.2 vs. ≤ 1.2 g/kg body weight/day) on time-to-discharge alive from the hospital (TTDA) and 60-day mortality and in different subgroups in critically ill patients with AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria within 7 days of ICU admission. The associations of protein dose with incidence and duration of kidney replacement therapy (KRT) were also investigated.

RESULTS

Of the 1329 randomized patients, 312 developed AKI and were included in this analysis (163 in the high and 149 in the usual protein dose group). High protein was associated with a slower time-to-discharge alive from the hospital (TTDA) (hazard ratio 0.5, 95% CI 0.4-0.8) and higher 60-day mortality (relative risk 1.4 (95% CI 1.1-1.8). Effect modification was not statistically significant for any subgroup, and no subgroups suggested a beneficial effect of higher protein, although the harmful effect of higher protein target appeared to disappear in patients who received kidney replacement therapy (KRT). Protein dose was not significantly associated with the incidence of AKI and KRT or duration of KRT.

CONCLUSIONS

In critically ill patients with AKI, high protein may be associated with worse outcomes in all AKI stages. Recommendation of higher protein dosing in AKI patients should be carefully re-evaluated to avoid potential harmful effects especially in patients who were not treated with KRT.

TRIAL REGISTRATION

This study is registered at ClinicalTrials.gov (NCT03160547) on May 17th 2017.

Loss of ZBED6 Protects Against Sepsis-Induced Muscle Atrophy by Upregulating DOCK3-Mediated RAC1/PI3K/AKT Signaling Pathway in Pigs

Sepsis-induced muscle atrophy often increases morbidity and mortality in intensive care unit (ICU) patients, yet neither therapeutic target nor optimal animal model is available for this disease. Here, by modifying the surgical strategy of cecal ligation and puncture (CLP), a novel sepsis pig model is created that for the first time recapitulates the whole course of sepsis in humans. With this model and sepsis patients, increased levels of the transcription factor zinc finger BED-type containing 6 (ZBED6) in skeletal muscle are shown. Protection against sepsis-induced muscle wasting in ZBED6-deficient pigs is further demonstrated. Mechanistically, integrated analysis of RNA-seq and ChIP-seq reveals dedicator of cytokinesis 3 (DOCK3) as the direct target of ZBED6. In septic ZBED6-deficient pigs, DOCK3 expression is increased in skeletal muscle and myocytes, activating the RAC1/PI3K/AKT pathway and protecting against sepsis-induced muscle wasting. Conversely, opposite gene expression patterns and exacerbated muscle wasting are observed in septic ZBED6-overexpressing myotubes. Notably, sepsis patients show increased ZBED6 expression along with reduced DOCK3 and downregulated RAC1/PI3K/AKT pathway. These findings suggest that ZBED6 is a potential therapeutic target for sepsis-induced muscle atrophy, and the established sepsis pig model is a valuable tool for understanding sepsis pathogenesis and developing its therapeutics.

Nutrition dose in the early acute phase of critical illness: Finding the sweet spot and heeding the lessons from the NUTRIREA trials

The landmark NUTRIREA-2 and NUTRIREA-3 trials compared the route and dose of nutrition, respectively, in critically ill patients with circulatory shock. The results of both trials support a "less-is-more" paradigm shift in the early acute phase of critical illness. In this review, the authors outline and appraise the results of the NUTRIREA-2 and NUTRIREA-3 trials, introduce the concept of identifying the "sweet spot" for nutrition dose based on severity of illness/nutrition risk and nutrition dose, and identify the unintended consequences of delivering full-dose nutrition in sicker critically ill patients during the early acute phase of critical illness.

Personalized nutrition therapy in critical care: 10 expert recommendations

Personalization of ICU nutrition is essential to future of critical care. Recommendations from American/European guidelines and practice suggestions incorporating recent literature are presented. Low-dose enteral nutrition (EN) or parenteral nutrition (PN) can be started within 48 h of admission. While EN is preferred route of delivery, new data highlight PN can be given safely without increased risk; thus, when early EN is not feasible, provision of isocaloric PN is effective and results in similar outcomes. Indirect calorimetry (IC) measurement of energy expenditure (EE) is recommended by both European/American guidelines after stabilization post-ICU admission. Below-measured EE (~ 70%) targets should be used during early phase and increased to match EE later in stay. Low-dose protein delivery can be used early (~ D1-2) (< 0.8 g/kg/d) and progressed to ≥ 1.2 g/kg/d as patients stabilize, with consideration of avoiding higher protein in unstable patients and in acute kidney injury not on CRRT. Intermittent-feeding schedules hold promise for further research. Clinicians must be aware of delivered energy/protein and what percentage of targets delivered nutrition represents. Computerized nutrition monitoring systems/platforms have become widely available. In patients at risk of micronutrient/vitamin losses (i.e., CRRT), evaluation of micronutrient levels should be considered post-ICU days 5-7 with repletion of deficiencies where indicated. In future, we hope use of muscle monitors such as ultrasound, CT scan, and/or BIA will be utilized to assess nutrition risk and monitor response to nutrition. Use of specialized anabolic nutrients such as HMB, creatine, and leucine to improve strength/muscle mass is promising in other populations and deserves future study. In post-ICU setting, continued use of IC measurement and other muscle measures should be considered to guide nutrition. Research on using rehabilitation interventions such as cardiopulmonary exercise testing (CPET) to guide post-ICU exercise/rehabilitation prescription and using anabolic agents such as testosterone/oxandrolone to promote post-ICU recovery is needed.