Does artificial nutrition improve outcome of critical illness?

[Immunometabolism in Sepsis]

Immunometabolism is a fascinating field of research that investigates the interactions between metabolic processes and the immune response. This intricate connection plays a pivotal role in regulating inflammatory reactions and consequently exerts a significant impact on the course of sepsis. The proinflammatory response during an immune reaction is closely tied to a high energy demand in immune cells. As a result, proinflammatory immune cells rapidly require substantial amounts of energy in the form of ATP, necessitating a fundamental and swift shift in their metabolism, i.e., their means of generating energy. This entails a marked increase in glycolysis within the proinflammatory response, thereby promptly meeting the energy requirements and providing essential metabolic building blocks for the biosynthesis of macromolecules. Alongside glycolysis, there is heightened activity in the pentose phosphate pathway (PPP). The PPP significantly contributes to NADPH production within the cell, thus maintaining redox equilibrium. Elevated PPP activity consequently leads to an increased NADPH level, resulting in enhanced production of reactive oxygen species (ROS) and nitric oxide (NO). While these molecules are crucial for pathogen elimination, an excess can also induce tissue damage. Simultaneously, there are dual interruptions in the citric acid cycle. In the cellular resting state, the citric acid cycle acts as a sort of "universal processor", where metabolic byproducts of glycolysis, fatty acid breakdown, and amino acid degradation are initially transformed into NADH and FADH2, subsequently yielding ATP. While the citric acid cycle and its connected oxidative phosphorylation predominantly generate energy at rest, it becomes downregulated in the proinflammatory phase of sepsis. The two interruptions lead to an accumulation of citrate and succinate within cells, reflecting mitochondrial dysfunction. Additionally, the significantly heightened glycolysis through fermentation yields lactate, a pivotal metabolite for sepsis diagnosis and prognosis. Conversely, cells in an anti-inflammatory state revert to a metabolic profile akin to the resting state: Glycolysis is attenuated, PPP is suppressed, and the citric acid cycle is reactivated. Of particular interest is that not only does the immune reaction influence metabolic pathways, but this connection also operates in reverse. Thus, modulation of metabolic pathways also modulates the immunity of the corresponding cell and thereby the state of the immune system itself. This could potentially serve as an intriguing avenue in sepsis therapy.

Inflammation and Nutrition: Friend or Foe?

The importance of the interplay between inflammation and nutrition has generated much interest in recent times. Inflammation has been identified as a key driver for disease-related malnutrition, leading to anorexia, reduced food intake, muscle catabolism, and insulin resistance, which are stimulating a catabolic state. Interesting recent data suggest that inflammation also modulates the response to nutritional treatment. Studies have demonstrated that patients with high inflammation show no response to nutritional interventions, while patients with lower levels of inflammation do. This may explain the contradictory results of nutritional trials to date. Several studies of heterogeneous patient populations, or in the critically ill or advanced cancer patients, have not found significant benefits on clinical outcome. Vice versa, several dietary patterns and nutrients with pro- or anti-inflammatory properties have been identified, demonstrating that nutrition influences inflammation. Within this review, we summarize and discuss recent advances in both the role of inflammation in malnutrition and the effect of nutrition on inflammation.

Toward nutrition improving outcome of critically ill patients: How to interpret recent feeding RCTs?

Although numerous observational studies associated underfeeding with poor outcome, recent randomized controlled trials (RCTs) have shown that early full nutritional support does not benefit critically ill patients and may induce dose-dependent harm. Some researchers have suggested that the absence of benefit in RCTs may be attributed to overrepresentation of patients deemed at low nutritional risk, or to a too low amino acid versus non-protein energy dose in the nutritional formula. However, these hypotheses have not been confirmed by strong evidence. RCTs have not revealed any subgroup benefiting from early full nutritional support, nor benefit from increased amino acid doses or from indirect calorimetry-based energy dosing targeted at 100% of energy expenditure. Mechanistic studies attributed the absence of benefit of early feeding to anabolic resistance and futile catabolism of extra provided amino acids, and to feeding-induced suppression of recovery-enhancing pathways such as autophagy and ketogenesis, which opened perspectives for fasting-mimicking diets and ketone supplementation. Yet, the presence or absence of an anabolic response to feeding cannot be predicted or monitored and likely differs over time and among patients. In the absence of such monitor, the value of indirect calorimetry seems obscure, especially in the acute phase of illness. Until now, large feeding RCTs have focused on interventions that were initiated in the first week of critical illness. There are no large RCTs that investigated the impact of different feeding strategies initiated after the acute phase and continued after discharge from the intensive care unit in patients recovering from critical illness.

Evaluation of the effect of high protein supply on diaphragm atrophy in critically ill patients receiving prolonged mechanical ventilation

BACKGROUND

Our aim was to evaluate the effect of high protein to the target of 2.0 g/kg/d on diaphragm atrophy and clinical prognosis of patients receiving prolonged mechanical ventilation (MV).

METHODS

This prospective, randomized, controlled, single-center study included 41 patients who were treated with ≥7 days' MV. The patients were randomly divided into a standard nutrition treatment (SNT) group and intensive nutrition treatment (INT) group, followed by evaluation of computer tomography-analyzed diaphragm volume, the level of butyrylcholinesterase (BChE) as a muscle mass indicator, and respiratory mechanics indices weekly to observe and compare the differences between the groups.

RESULTS

In the INT group, the actual protein (1.70 ± 0.21 vs 1.06 ± 0.21 g/kg/d, P < .001) and calorie intake (33.46 ± 2.78 vs 25.75 ± 4.81 kcal/kg/d, P < .001) were significantly different from those of the SNT group. Compared with the SNT group, the INT group's diaphragm atrophy improved in the fourth and fifth weeks (all P < .05). The BChE after the third week was higher (all P < .05). No significant differences in respiratory mechanical indices and clinical outcomes were found in the surviving patients between the groups.

CONCLUSION

INT improved the diaphragm atrophy and muscle mass of critically ill patients receiving prolonged MV. There was no evidence that increasing protein to the target amount of 2.0 g/kg/d is related to improvement in clinical prognosis for patients receiving prolonged MV.

Aggressive nutrition therapy in malnutrition and sarcopenia

Aggressive nutrition therapy is essential to improve nutrition and function in patients with malnutrition and sarcopenia. Malnutrition and sarcopenia negatively affect functional recovery and activities of daily living. Nutrition improvement is associated with better functional recovery. Target energy intake in aggressive nutrition therapy is defined as total energy expenditure (TEE) plus the amount of energy accumulated. The amount of energy accumulation per 1 kg of body weight is generally 7500 kcal. If the goal is to gain 1 kg of weight over 30 d, TEE + 250 kcal is the target daily energy intake. Aggressive nutrition therapy is implemented using a rehabilitation nutrition care process, which consists of five steps: assessment and diagnostic reasoning, diagnosis, goal setting, intervention, and monitoring. Aggressive nutrition therapy sets clear goals using the Specific, Measurable, Achievable, Relevant, and Time-bound principles. The application and effect of aggressive nutrition therapy differs depending on the etiology and condition of malnutrition. Precachexia, short bowel syndrome, and older people with mild to moderate dementia are indications for aggressive nutrition therapy. Nevertheless, aggressive nutrition therapy is usually contraindicated in cases of refractory cachexia, acute disease or injury with severe inflammation, and bedridden patients with severe dementia and reduced activity. Aggressive nutrition therapy should be combined with aggressive exercise and rehabilitation. Enhanced nutritional therapy combined with rehabilitation in patients with cerebrovascular disease, hip fracture, or acute disease is recommended in the 2018 clinical practice guidelines for rehabilitation nutrition. Further evidence for aggressive nutrition therapy is however required.

Mitochondrial Dysfunction in Critical Illness: Implications for Nutritional Therapy

PURPOSE OF THE REVIEW

This paper will review the evidence for mitochondrial dysfunction in critical illness, describe the mechanisms which lead to multiple organ failure, and detail the implications of this pathophysiologic process on nutritional therapy.

RECENT FINDINGS

Mitochondria are particularly sensitive to increased oxidative stress in critical illness. The functional and structural abnormalities which occur in this organelle contribute further to the excessive production of reactive oxygen species and the reduction in generation of adenosine triphosphate (ATP). To reduce metabolic demand, mitochondrial dysfunction develops (a process likened to hibernation), which helps sustain the life of the cell at a cost of organ system failure. Aggressive feeding in the early phases of critical illness might inappropriately increase demand at a time when ATP production is limited, further jeopardizing cell survival and potentiating the processes leading to multiple organ failure. Several potential therapies exist which would promote mitochondrial function in the intensive care setting through support of autophagy, antioxidant defense systems, and the biogenesis and recovery of the organelle itself. Nutritional therapy should supplement micronutrients required in the mitochondrial metabolic pathways and provide reduced delivery of macronutrients through slower advancement of feeding in the early phases of critical illness. A better understanding of mitochondrial dysfunction in the critically ill patient should lead to more innovative therapies in the future.

Clinical nutrition for the gastroenterologist: bedside strategies for feeding the hospitalized patient

PURPOSE OF REVIEW

The timing, advancement, and use of appropriate monitors determine whether the hospitalized patient experiences the full benefit of nutritional therapy. This article reviews management strategies in delivering the optimal nutrition regimen capable of improving outcomes in the hospitalized patient.

RECENT FINDINGS

Enteral nutrition should be initiated in the first 24-36 h after admission. Determination of nutritional risk helps guide the urgency with which nutritional therapy is provided and predicts the likelihood for difficulties in delivering the prescribed regimen. Feeds should be advanced slowly over 3-4 days to meet 70-80% of goal for calories (20 kcal/kg/day) and 100% for protein (2.0 gm/kg/day). Reaching protein goals early on may be more important than achieving energy goals. Patients should be monitored for hemodynamic stability, evidence of refeeding syndrome, and tolerance in the setting of gastrointestinal dysfunction. Parenteral nutrition should be utilized in select high-risk patients where the feasibility of full enteral nutrition is questioned.

SUMMARY

Timing with early initiation of enteral nutrition, avoidance of overfeeding, and step-wise advancement of feeds are required to safely realize the benefits of such therapy.

Nutritional Management of Medical Inpatients

Malnutrition is a common condition in hospitalized patients that is often underdiagnosed and undertreated. Hospital malnutrition has multifactorial causes and is associated with negative clinical and economic outcomes. There is now growing evidence from clinical trials for the efficiency and efficacy of nutritional support in the medical inpatient population. Since many medical inpatients at nutritional risk or malnourished are polymorbid (i.e., suffer from multiple comorbidities), this makes the provision of adequate nutritional support a challenging task, given that most of the clinical nutrition guidelines are dedicated to single diseases. This review summarizes the current level of evidence for nutritional support in not critically ill polymorbid medical inpatients.

Individualised nutritional support in medical inpatients at nutritional risk: a randomised clinical trial

BACKGROUND

Guidelines recommend the use of nutritional support during hospital stays for medical patients (patients not critically ill and not undergoing surgical procedures) at risk of malnutrition. However, the supporting evidence for this recommendation is insufficient, and there is growing concern about the possible negative effects of nutritional therapy during acute illness on recovery and clinical outcomes. Our aim was thus to test the hypothesis that protocol-guided individualised nutritional support to reach protein and caloric goals reduces the risk of adverse clinical outcomes in medical inpatients at nutritional risk.

METHODS

The Effect of early nutritional support on Frailty, Functional Outcomes, and Recovery of malnourished medical inpatients Trial (EFFORT) is a pragmatic, investigator-initiated, open-label, multicentre study. We recruited medical patients at nutritional risk (nutritional risk screening 2002 [NRS 2002] score ≥3 points) and with an expected length of hospital stay of more than 4 days from eight Swiss hospitals. These participants were randomly assigned (1:1) to receive either protocol-guided individualised nutritional support to reach protein and caloric goals (intervention group) or standard hospital food (control group). Randomisation was done with variable block sizes and stratification according to study site and severity of malnutrition using an interactive web-response system. In the intervention group, individualised nutritional support goals were defined by specialist dietitians and nutritional support was initiated no later than 48 h after admission. Patients in the control group received no dietary consultation. The composite primary endpoint was any adverse clinical outcome defined as all-cause mortality, admission to intensive care, non-elective hospital readmission, major complications, and decline in functional status at 30 days, and it was measured in all randomised patients who completed the trial. This trial is registered with ClinicalTrials.gov, number NCT02517476.

FINDINGS

5015 patients were screened, and 2088 were recruited and monitored between April 1, 2014, and Feb 28, 2018. 1050 patients were assigned to the intervention group and 1038 to the control group. 60 patients withdrew consent during the course of the trial (35 in the intervention group and 25 in the control group). During the hospital stay, caloric goals were reached in 800 (79%) and protein goals in 770 (76%) of 1015 patients in the intervention group. By 30 days, 232 (23%) patients in the intervention group experienced an adverse clinical outcome, compared with 272 (27%) of 1013 patients in the control group (adjusted odds ratio [OR] 0·79 [95% CI 0·64-0·97], p=0·023). By day 30, 73 [7%] patients had died in the intervention group compared with 100 [10%] patients in the control group (adjusted OR 0·65 [0·47-0·91], p=0·011). There was no difference in the proportion of patients who experienced side-effects from nutritional support between the intervention and the control group (162 [16%] vs 145 [14%], adjusted OR 1·16 [0·90-1·51], p=0·26).

INTERPRETATION

In medical inpatients at nutritional risk, the use of individualised nutritional support during the hospital stay improved important clinical outcomes, including survival, compared with standard hospital food. These findings strongly support the concept of systematically screening medical inpatients on hospital admission regarding nutritional risk, independent of their medical condition, followed by a nutritional assessment and introduction of individualised nutritional support in patients at risk.

FUNDING

The Swiss National Science Foundation and the Research Council of the Kantonsspital Aarau, Switzerland.

Gut rest strategy and trophic feeding in the acute phase of critical illness with acute gastrointestinal injury

Critically ill patients frequently suffer from gastrointestinal dysfunction as the intestine is a vulnerable organ. In critically ill patients who require nutritional support, the current guidelines recommend the use of enteral nutrition within 24-48 h and advancing towards optimal nutritional goals over the next 48-72 h; however, this may be contraindicated in patients with acute gastrointestinal injury because overuse of the gut in the acute phase of critical illness may have an adverse effect on the prognosis. We propose that trophic feeding after 72 h, as a partial gut rest strategy, should be provided to critically ill patients during the acute phase of illness as an organ-protective strategy, especially for those with acute gastrointestinal injury.

Nutritional support in the recovery phase of critically ill children

PURPOSE OF REVIEW

The metabolic stress response of a critically ill child evolves over time and thus it seems reasonable that nutritional requirements change during their course of illness as well. This review proposes strategies and considerations for nutritional support during the recovery phase to gain optimal (catch-up) growth with preservation of lean body mass.

RECENT FINDINGS

Critical illness impairs nutritional status, muscle mass and function, and neurocognition, but early and high intakes of artificial nutrition during the acute phase cannot resolve this. Although (parenteral) nutrient restriction during the acute phase appears to be beneficial, persistent nutrient restriction, when the metabolic stress response resolves, has short-term and long-term detrimental consequences. Requirements increase markedly during the recovery phase to enable recovery and catch-up growth. Such large amounts of intake demand for alternate approach, especially when intestinal problems constitute a barrier for full enteral feeding. As part of the nutritional recovery, mobilization and exercise are essential to achieve catch-up growth with an optimal body composition.

SUMMARY

During the recovery phase of paediatric critical illness (catch-up) growth and muscle recovery require nutritional intakes at least two times the resting energy expenditure.

The Effect of Higher Protein Dosing in Critically Ill Patients: A Multicenter Registry-Based Randomized Trial: The EFFORT Trial

Current randomized trials and observational studies evaluating higher versus lower protein doses in critically ill patients yield inconclusive results. Because of few studies and methodologic limitations, clinical guidelines suggest a wide range of protein intake based on weak evidence. Clinical equipoise about protein dosing exists. The purpose of the current manuscript is to provide the rationale and protocol for a randomized controlled trial (RCT) of 4000 critically ill patients randomly allocated to receive a higher or lower protein dose. We propose a global, volunteer-driven, registry-based RCT involving >100 intensive care units (ICUs). We will enroll mechanically ventilated patients with high nutrition risk, identified by low (≤25) or high (≥35) body mass index, moderate to severe malnutrition, frailty, sarcopenia, or when >96-hour duration of mechanical ventilation is expected. Exclusion criteria include patients who are >96 hours since initiation of mechanical ventilation, moribund, or pregnant, and where the clinician lacks clinical equipoise regarding protein dose. The intervention consists of higher (≥2.2 g/kg/d) or lower (≤1.2 g/kg/d) protein dose, achieved by enteral nutrition, parenteral nutrition, or both. The primary outcome will be 60-day mortality. Key secondary outcomes include time-to-discharge alive from hospital, ICU and hospital survival, and length of stay. As this is research based on existing medical practice, we will apply for a waiver of informed consent, where possible. The large sample size is a reflection of the small signal we expect to see in this large, pragmatic trial.

Enteral versus parenteral nutrition and enteral versus a combination of enteral and parenteral nutrition for adults in the intensive care unit

BACKGROUND

Critically ill people are at increased risk of malnutrition. Acute and chronic illness, trauma and inflammation induce stress-related catabolism, and drug-induced adverse effects may reduce appetite or increase nausea and vomiting. In addition, patient management in the intensive care unit (ICU) may also interrupt feeding routines. Methods to deliver nutritional requirements include provision of enteral nutrition (EN), or parenteral nutrition (PN), or a combination of both (EN and PN). However, each method is problematic. This review aimed to determine the route of delivery that optimizes uptake of nutrition.

OBJECTIVES

To compare the effects of enteral versus parenteral methods of nutrition, and the effects of enteral versus a combination of enteral and parenteral methods of nutrition, among critically ill adults, in terms of mortality, number of ICU-free days up to day 28, and adverse events.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase on 3 October 2017. We searched clinical trials registries and grey literature, and handsearched reference lists of included studies and related reviews.

SELECTION CRITERIA

We included randomized controlled studies (RCTs) and quasi-randomized studies comparing EN given to adults in the ICU versus PN or versus EN and PN. We included participants that were trauma, emergency, and postsurgical patients in the ICU.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, extracted data, and assessed risk of bias. We assessed the certainty of evidence with GRADE.

MAIN RESULTS

We included 25 studies with 8816 participants; 23 studies were RCTs and two were quasi-randomized studies. All included participants were critically ill in the ICU with a wide range of diagnoses; mechanical ventilation status between study participants varied. We identified 11 studies awaiting classification for which we were unable to assess eligibility, and two ongoing studies.Seventeen studies compared EN versus PN, six compared EN versus EN and PN, two were multi-arm studies comparing EN versus PN versus EN and PN. Most studies reported randomization and allocation concealment inadequately. Most studies reported no methods to blind personnel or outcome assessors to nutrition groups; one study used adequate methods to reduce risk of performance bias.Enteral nutrition versus parenteral nutritionWe found that one feeding route rather than the other (EN or PN) may make little or no difference to mortality in hospital (risk ratio (RR) 1.19, 95% confidence interval (CI) 0.80 to 1.77; 361 participants; 6 studies; low-certainty evidence), or mortality within 30 days (RR 1.02, 95% CI 0.92 to 1.13; 3148 participants; 11 studies; low-certainty evidence). It is uncertain whether one feeding route rather than the other reduces mortality within 90 days because the certainty of the evidence is very low (RR 1.06, 95% CI 0.95 to 1.17; 2461 participants; 3 studies). One study reported mortality at one to four months and we did not combine this in the analysis; we reported this data as mortality within 180 days and it is uncertain whether EN or PN affects the number of deaths within 180 days because the certainty of the evidence is very low (RR 0.33, 95% CI 0.04 to 2.97; 46 participants).No studies reported number of ICU-free days up to day 28, and one study reported number of ventilator-free days up to day 28 and it is uncertain whether one feeding route rather than the other reduces the number of ventilator-free days up to day 28 because the certainty of the evidence is very low (mean difference, inverse variance, 0.00, 95% CI -0.97 to 0.97; 2388 participants).We combined data for adverse events reported by more than one study. It is uncertain whether EN or PN affects aspiration because the certainty of the evidence is very low (RR 1.53, 95% CI 0.46 to 5.03; 2437 participants; 2 studies), and we found that one feeding route rather than the other may make little or no difference to pneumonia (RR 1.10, 95% CI 0.82 to 1.48; 415 participants; 7 studies; low-certainty evidence). We found that EN may reduce sepsis (RR 0.59, 95% CI 0.37 to 0.95; 361 participants; 7 studies; low-certainty evidence), and it is uncertain whether PN reduces vomiting because the certainty of the evidence is very low (RR 3.42, 95% CI 1.15 to 10.16; 2525 participants; 3 studies).Enteral nutrition versus enteral nutrition and parenteral nutritionWe found that one feeding regimen rather than another (EN or combined EN or PN) may make little or no difference to mortality in hospital (RR 0.99, 95% CI 0.84 to 1.16; 5111 participants; 5 studies; low-certainty evidence), and at 90 days (RR 1.00, 95% CI 0.86 to 1.18; 4760 participants; 2 studies; low-certainty evidence). It is uncertain whether combined EN and PN leads to fewer deaths at 30 days because the certainty of the evidence is very low (RR 1.64, 95% CI 1.06 to 2.54; 409 participants; 3 studies). It is uncertain whether one feeding regimen rather than another reduces mortality within 180 days because the certainty of the evidence is very low (RR 1.00, 95% CI 0.65 to 1.55; 120 participants; 1 study).No studies reported number of ICU-free days or ventilator-free days up to day 28. It is uncertain whether either feeding method reduces pneumonia because the certainty of the evidence is very low (RR 1.40, 95% CI 0.91 to 2.15; 205 participants; 2 studies). No studies reported aspiration, sepsis, or vomiting.

AUTHORS' CONCLUSIONS

We found insufficient evidence to determine whether EN is better or worse than PN, or than combined EN and PN for mortality in hospital, at 90 days and at 180 days, and on the number of ventilator-free days and adverse events. We found fewer deaths at 30 days when studies gave combined EN and PN, and reduced sepsis for EN rather than PN. We found no studies that reported number of ICU-free days up to day 28. Certainty of the evidence for all outcomes is either low or very low. The 11 studies awaiting classification may alter the conclusions of the review once assessed.

Calorie intake and short-term survival of critically ill patients

BACKGROUND & AIMS

The association between calorie supply and outcome of critically ill patients is unclear. Results from observational studies contradict findings of randomized studies, and have been questioned because of unrecognized confounding by indication. The present study wanted to re-examine the associations between the daily amount of calorie intake and short-term survival of critically ill patients using several novel statistical approaches.

METHODS

9661 critically ill patients from 451 ICUs were extracted from an international database. We examined associations between survival time and three pragmatic nutritional categories (I: <30% of target, II: 30-70%, III: >70%) reflecting different amounts of total daily calorie intake. We compared hazard ratios for the 30-day risk of dying estimated for different hypothetical nutrition support plans (different categories of daily calorie intake during the first 11 days after ICU admission). To minimize indication bias, we used a lag time between nutrition and outcome, we particularly considered daily amounts of calorie intake, and we adjusted results to the route of calorie supply (enteral, parenteral, oral).

RESULTS

1974 patients (20.4%) died in hospital before day 30. Median of daily artificial calorie intake was 1.0 kcal/kg [IQR 0.0-4.1] in category I, 12.3 kcal/kg [9.4-15.4] in category II, and 23.5 kcal/kg [19.5-27.8] in category III. When compared to a plan providing daily minimal amounts of calories (category I), the adjusted minimal hazard ratios for a delayed (from day 5-11) or an early (from day 1-11) mildly hypocaloric nutrition (category II) were 0.71 (95% confidence interval [CI], 0.54 to 0.94) and 0.56 (95% CI, 0.38 to 0.82), respectively. No substantial hazard change could be detected, when a delayed or an early, near target calorie intake (category III) was compared to an early, mildly hypocaloric nutrition.

CONCLUSIONS

Compared to a severely hypocaloric nutrition, a mildly hypocaloric nutrition is associated with a decreased risk of death. In unselected critically ill patients, this risk cannot be reduced further by providing amounts of calories close to the calculated target.

STUDY REGISTRATION

ID number ISRCTN17829198, website http://www.isrctn.org.

Controversies Surrounding Critical Care Nutrition: An Appraisal of Permissive Underfeeding, Protein, and Outcomes

Over the past few years, numerous studies have called into question the optimal dose, timing, composition, and advancement rate of nutrition during the early acute phase of critical illness. These studies suggest permissive underfeeding with slow advancement may be more beneficial than aggressive full feeding. These counterintuitive results were possibly explained by enhanced autophagy, less hyperglycemia, or prevention of refeeding syndrome. This review underscores the controversies surrounding permissive underfeeding, aims to answer whether permissive underfeeding is appropriate for all critically ill patients, describes the impact of optimal protein delivery on critical care outcomes, discusses nutrition risk, and cogitates on the impact of nutrition on critical care outcomes.

Energy, Protein, Carbohydrate, and Lipid Intakes and Their Effects on Morbidity and Mortality in Critically Ill Adult Patients: A Systematic Review

The guidelines for nutritional support in critically ill adult patients differ in various aspects. The optimal amount of energy and nutritional substrates supplied is important for reducing morbidity and mortality, but unfortunately this is not well known, because the topic is complex and every patient is individual. The aim of this review was to gather recent pertinent information concerning the nutritional support of critically ill patients in the intensive care unit (ICU) with respect to the energy, protein, carbohydrate, and lipid intakes and the effect of their specific utilization on morbidity and mortality. Enteral nutrition (EN) is generally recommended over parenteral nutrition (PN) and is beneficial when administered within 24-48 h after ICU admission. In contrast, early PN does not provide substantial advantages in terms of morbidity and mortality, and the time when it is safe and beneficial remains unclear. The most advantageous recommendation seems to be administration of a hypocaloric (<20 kcal · kg^-1 · d^-1), high-protein diet (amino acids at doses of ≥2 g · kg^-1 · d^-1), at least during the first week of critical illness. Another important factor for reducing morbidity is the maintenance of blood glucose concentrations at 120-150 mg/dL, which is accomplished with the use of insulin and lower doses of glucose of 1-2 g · kg^-1 · d^-1, because this prevents the risk of hypoglycemia and is associated with a better prognosis according to recent studies. A fat emulsion is used as a source of required calories because of insulin resistance in the majority of patients. In addition, lipid oxidation in these patients is ∼25% higher than in healthy subjects.

Effect of Calories Delivered on Clinical Outcomes in Critically Ill Patients: Systemic Review and Meta-analysis

Introduction:

International guidelines are promoting early enteral nutrition (EN) as a means of feeding critically ill adult patients to improve clinical outcomes. The question of how much calorie intake is enough to improve the outcomes still remained inconclusive. Therefore, we carried out a meta-analysis to evaluate the effect of low calorie (LC) versus high calorie (HC) delivery on critically ill patients' outcomes.

Methods:

We included randomized clinical trials (RCTs) that compared LC EN with or without supplemental parenteral nutrition with HC delivery in this meta-analysis irrespective of the site of nutritional delivery in the gastrointestinal tract. We searched PubMed, EMBASE, and Cochrane central register of controlled trials electronic databases to identify RCTs that compared the effects of initially different calorie intake in critical illness. The primary outcome was overall mortality.

Results:

This meta-analysis included 17 RCTs with a total of 3,593 participants. The result of analysis showed that there was no significant difference between the LC group and HC group in overall mortality (risk ratio [RR], 0.98; 95% confidence interval [CI], 0.87–1.10; P = 0.74; I² = 6%; P = 0.38), or new-onset pneumonia (RR, 0.92; 95% CI, 0.73–1.16, P = 0.46; I² = 38%, P = 0. 11).

Conclusion:

The current meta-analysis showed that there was no significant difference in mortality of critically ill patients initially between the two groups.

Editorial on the original article entitled "Permissive underfeeding of standard enteral feeding in critically ill adults" published in the New England Journal of Medicine on June 18, 2015

On June 18, 2015, the New England Journal of Medicine published an article entitled "Permissive underfeeding of standard enteral feeding in critically ill adults", which reports the results of a study that examined the impact of prolonged nutritional energy restriction for critically ill patients. The study design was unique in the sense that patients in both groups received similar doses of protein during the intervention, while the non-protein energy intake was reduced in the intervention group. The study showed no differences in outcome between the two study groups. These results add to a growing body of high quality evidence against the dogmatic belief that full enteral or parenteral feeding should be given as early as possible during critical illness to prevent complications. Further research is now needed to address the question of the optimal timing to provide more nutritional support for the benefit of the patients, possibly guided by improved biomarkers that need to be developed and validated, and to investigate underlying mechanisms.

Nutrition in the pediatric population in the intensive care unit

Nutrition is an essential component of patient management in the pediatric intensive care unit (PICU). Poor nutrition status accompanies many childhood chronic illnesses. A thorough assessment of the critically ill child is required to inform the plan for nutrition support. Accurate and clinically relevant nutritional assessment, including growth measurements, provides important guidance. Indirect calorimetry provides the most accurate measurement of resting energy expenditure, but is too often unavailable in the PICU. To prevent inappropriate caloric intake, reassessment of the child's nutrition status is imperative. Enteral nutrition is the recommended route of intake. Human milk is preferred for infants.

Pros and cons of feeding the septic intensive care unit patient

Sepsis is a common disease seen in critically ill patients. Many patients with sepsis are unable to provide nutrition for themselves, and therefore initiating artificial nutrition has become part of routine care for these patients. However, studies investigating the optimal route, composition, volume, and duration of nutrition in critically ill patients with sepsis are lacking. The best recommendations have to be extrapolated from studies in heterogeneous populations of critically ill patients or in those with syndromes such as acute lung injury or acute respiratory distress syndrome (ARDS) where sepsis is a common predisposing etiology. In this review, we summarize pertinent studies that inform clinical practice on providing artificial nutrition to critically ill patients with severe sepsis and make recommendations as to how these studies influence clinical care of these patients.

Metabolic and nutritional support of critically ill patients: consensus and controversies

The results of recent large-scale clinical trials have led us to review our understanding of the metabolic response to stress and the most appropriate means of managing nutrition in critically ill patients. This review presents an update in this field, identifying and discussing a number of areas for which consensus has been reached and others where controversy remains and presenting areas for future research. We discuss optimal calorie and protein intake, the incidence and management of re-feeding syndrome, the role of gastric residual volume monitoring, the place of supplemental parenteral nutrition when enteral feeding is deemed insufficient, the role of indirect calorimetry, and potential indications for several pharmaconutrients.

Comparison of different definitions of feeding intolerance: A retrospective observational study

BACKGROUND & AIMS

While feeding intolerance (FI) is clinically important in the critically ill it is inconsistently defined. By evaluating definitions of FI based on relationships between symptoms and signs of gastrointestinal (GI) dysfunction and mortality the objective was to define FI using the definition that was most strongly associated with subsequent mortality.

METHODS

Data from all adult patients admitted to a single ICU between 2004 and 2011, and who were receiving enteral nutrition (EN), were analysed. The amount of EN administered, presence of absent bowel sounds (BS), vomiting and/or regurgitation, diarrhoea, bowel distension, and large gastric residual volumes (GRVs) were documented daily. A GRV ≥500 ml/day was considered as large and the sum of gastrointestinal (GI) symptoms including large GRV was calculated daily. Various definitions of FI were modelled. Definitions using only GRV, or GRV with other GI symptoms, or GRV and failure to reach preset EN targets were evaluated. The predictive power of FI on mortality was tested by adding the presence of FI (different definitions were tested one-by-one) into multiple regression analyses together with admission day demographic and severity of illness variables.

RESULTS

Of the 1712 patients included, 221 (12.9%) died in ICU and 495 (28.9%) had died within 90 days after ICU admission. The definition of FI based on the presence of at least three out of five GI symptoms was most strongly related to ICU-mortality (6.3% prevalence in survivors vs. 23.5% in non-survivors, p < 0.001, odds ratio (95%CI) 3.39 (2.23-5.14)), whereas EN <23% of caloric target was the strongest predictor for mortality 90 days after admission (50.7% prevalence among survivors vs 75.2% in non-survivors, p < 0.001, odds ratio (95% CI) 2.34 (1.80-3.04)).

CONCLUSIONS

FI is associated with increased mortality but the strength of this relationship depends on the definition used. The 'best' definition of FI for prediction of ICU-mortality is based on a complex assessment of GI symptoms (including large GRV), whereas enteral underfeeding is the definition of FI that is the strongest predictor of death within 90 days of admission. Our 'best' definitions are not immediately generalizable, but should help building up future studies.

Timing of (supplemental) parenteral nutrition in critically ill patients: a systematic review

Supplemental parenteral nutrition (SPN) is used in a step-up approach when full enteral support is contraindicated or fails to reach caloric targets. Recent nutrition guidelines present divergent advices regarding timing of SPN in critically ill patients ranging from early SPN (<48 h after admission; EPN) to postponing initiation of SPN until day 8 after Intensive Care Unit (ICU) admission (LPN). This systematic review summarizes results of prospective studies among adult ICU patients addressing the best timing of (supplemental) parenteral nutrition (S)PN. A structured PubMed search was conducted to identify eligible articles. Articles were screened and selected using predetermined criteria and appraised for relevance and validity. After critical appraisal, four randomized controlled trials (RCTs) and two prospective observational studies remained. One RCT found a higher percentage of alive discharge from the ICU at day 8 in the LPN group compared to EPN group (p = 0.007) but no differences in ICU and in-hospital mortality. None of the other RCTs found differences in ICU or in-hospital mortality rates. Contradicting or divergent results on other secondary outcomes were found for ICU length of stay, hospital length of stay, infection rates, nutrition targets, duration of mechanical ventilation, glucose control, duration of renal replacement therapy, muscle wasting and fat loss. Although the heterogeneity in quality and design of relevant studies precludes firm conclusions, it is reasonable to assume that in adult critically ill patients, there are no clinically relevant benefits of EPN compared with LPN with respect to morbidity or mortality end points, when full enteral support is contraindicated or fails to reach caloric targets. However, considering that infectious morbidity and resolution of organ failure may be negatively affected through mechanisms not yet clearly understood and acquisition costs of parenteral nutrition are higher, the early administration of parenteral nutrition cannot be recommended.

Nutrition in the ICU: an evidence-based approach

Providing artificial nutrition is an important part of caring for critically ill patients. However, because of a paucity of robust data, the practice has been highly variable and often based more on dogma than evidence. A number of studies have been published investigating many different aspects of critical care nutrition. Although the influx of data has better informed the practice, the results have often been conflicting or counter to prevailing thought, resulting in discordant opinions and different interpretations by experts in the field. In this article, we review and summarize the data from a number of the published studies, including studies investigating enteral vs parenteral nutrition, supplementing enteral with parenteral nutrition, and use of immunonutrition. In addition, published studies informing the practice of how best to provide enteral nutrition will be reviewed, including the use of trophic feedings, gastric residual volumes, and gastric vs postpyloric tube placement.

The Effect of Nutritional Status in the Pathogenesis of Critical Illness Myopathy (CIM)

The muscle wasting and loss of specific force associated with Critical Illness Myopathy (CIM) is, at least in part, due to a preferential loss of the molecular motor protein myosin. This acquired myopathy is common in critically ill immobilized and mechanically ventilated intensive care patients (ICU). There is a growing understanding of the mechanisms underlying CIM, but the role of nutritional factors triggering this serious complication of modern intensive care remains unknown. This study aims at establishing the effect of nutritional status in the pathogenesis of CIM. An experimental ICU model was used where animals are mechanically ventilated, pharmacologically paralysed post-synaptically and extensively monitored for up to 14 days. Due to the complexity of the experimental model, the number of animals included is small. After exposure to this ICU condition, animals develop a phenotype similar to patients with CIM. The results from this study show that the preferential myosin loss, decline in specific force and muscle fiber atrophy did not differ between low vs. eucaloric animals. In both experimental groups, passive mechanical loading had a sparing effect of muscle weight independent on nutritional status. Thus, this study confirms the strong impact of the mechanical silencing associated with the ICU condition in triggering CIM, overriding any potential effects of caloric intake in triggering CIM. In addition, the positive effects of passive mechanical loading on muscle fiber size and force generating capacity was not affected by the nutritional status in this study. However, due to the small sample size these pilot results need to be validated in a larger cohort.

The nutritional energy to clinical outcome relation revisited

In the previous issue of Critical Care, Dr Bellomo and colleagues reported an observational study of the relationship between nutritional intake and survival in the RENAL randomized controlled trial. In summary, the total energy intake in a very large and severely ill patient population was low. Higher average daily caloric energy intake was not associated with improved survival. The study illustrates the complexity of the interaction between disease and nutrition.

Calorie intake and patient outcomes in severe acute kidney injury: findings from The Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study trial

Introduction

Current practice in the delivery of caloric intake (DCI) in patients with severe acute kidney injury (AKI) receiving renal replacement therapy (RRT) is unknown. We aimed to describe calorie administration in patients enrolled in the Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study and to assess the association between DCI and clinical outcomes.

Methods

We performed a secondary analysis in 1456 patients from the RENAL trial. We measured the dose and evolution of DCI during treatment and analyzed its association with major clinical outcomes using multivariable logistic regression, Cox proportional hazards models, and time adjusted models.

Results

Overall, mean DCI during treatment in ICU was low at only 10.9 ± 9 Kcal/kg/day for non-survivors and 11 ± 9 Kcal/kg/day for survivors. Among patients with a lower DCI (below the median) 334 of 729 (45.8%) had died at 90-days after randomization compared with 316 of 727 (43.3%) patients with a higher DCI (above the median) (P = 0.34). On multivariable logistic regression analysis, mean DCI carried an odds ratio of 0.95 (95% confidence interval (CI): 0.91-1.00; P = 0.06) per 100 Kcal increase for 90-day mortality. DCI was not associated with significant differences in renal replacement (RRT) free days, mechanical ventilation free days, ICU free days and hospital free days. These findings remained essentially unaltered after time adjusted analysis and Cox proportional hazards modeling.

Conclusions

In the RENAL study, mean DCI was low. Within the limits of such low caloric intake, greater DCI was not associated with improved clinical outcomes.

Trial registration

ClinicalTrials.gov number, NCT00221013

Whey Peptide-Based Formulas With ω-3 Fatty Acids Are Protective in Lipopolysaccharide-Mediated Sepsis

BACKGROUND

Sepsis and septic shock syndrome are among the leading causes of death in critically ill patients. Lipopolysaccharide (LPS) released by bacteria within the colon may translocate across a compromised epithelium, leading to oxidative stress, inflammation, sepsis, and eventually death.

METHODS

We examined the effects of a whey-based enteral formula high in cysteine (antioxidant precursor) and the addition of ω-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), against a mouse model of LPS-induced sepsis. Mice were fed either a whey-based diet with EPA-DHA (PAF), a whey-based diet without EPA-DHA (PSTD), or a casein-based control diet (CONT).

RESULTS

Mice fed PAF or PSTD were protected against LPS-induced weight loss. Whey-based diets suppressed inflammatory cytokine release and oxidative stress damage. Furthermore, PAF and PSTD were able to inhibit autophagy, a mechanism in which the cell recycles damaged organelles. These anti-inflammatory and antioxidative effects of PSTD and PAF resulted in decreased liver inflammation and intestinal damage and promoted protective microbiota within the intestines.

CONCLUSIONS

These data suggest a clinical role for whey peptide-based diets in promoting healing and recovery in critically ill patients.

Does artificial nutrition improve outcome of critical illness? An alternative viewpoint!

Recent studies challenge the beneficial role of artificial nutrition provided to critically ill patients and point out the limitations of existing studies in this area. We take a differing view of the existing data and refute many of the arguments put forward by previous authors. We review the mechanistic, observational, and experimental data supporting a role for early enteral nutrition in the critically ill patient. We conclude without question that more, high-quality research is needed to better define the role of artificial nutrition in the critical care setting, but until then early and adequate delivery of enteral nutrition is a legitimate, evidence-based treatment recommendation and we see no evidence-based role for restricting enteral nutrition in critically ill patients. The role of early supplemental parenteral nutrition continues to be defined as new data emerge.