Hypocaloric Feeding of the Critically Ill

High-Protein Hypocaloric Nutrition for Non-Obese Critically Ill Patients

High-protein hypocaloric nutrition, tailored to each patient's muscle mass, protein-catabolic severity, and exogenous energy tolerance, is the most plausible nutrition therapy in protein-catabolic critical illness. Sufficient protein provision could mitigate the rapid muscle atrophy characteristic of this disease while providing urgently needed amino acids to the central protein compartment and sites of tissue injury. The protein dose may range from 1.5 to 2.5 g protein (1.8-3.0 g free amino acids)/kg dry body weight per day. Nutrition should be low in energy (≈70% of energy expenditure or ≈15 kcal/kg dry body weight per day) because efforts to match energy provision to energy expenditure are physiologically irrational, risk toxic energy overfeeding, and have repeatedly failed in large clinical trials to demonstrate clinical benefit. The American Society for Parenteral and Enteral Nutrition currently suggests high-protein hypocaloric nutrition for obese critically ill patients. Short-term high-protein hypocaloric nutrition is physiologically and clinically sensible for most protein-catabolic critically ill patients, whether obese or not.

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.

Nutritional support for critically ill children

BACKGROUND

Nutritional support in the critically ill child has not been well investigated and is a controversial topic within paediatric intensive care. There are no clear guidelines as to the best form or timing of nutrition in critically ill infants and children. This is an update of a review that was originally published in 2009. .

OBJECTIVES

The objective of this review was to assess the impact of enteral and parenteral nutrition given in the first week of illness on clinically important outcomes in critically ill children. There were two primary hypotheses:1. the mortality rate of critically ill children fed enterally or parenterally is different to that of children who are given no nutrition;2. the mortality rate of critically ill children fed enterally is different to that of children fed parenterally.We planned to conduct subgroup analyses, pending available data, to examine whether the treatment effect was altered by:a. age (infants less than one year versus children greater than or equal to one year old);b. type of patient (medical, where purpose of admission to intensive care unit (ICU) is for medical illness (without surgical intervention immediately prior to admission), versus surgical, where purpose of admission to ICU is for postoperative care or care after trauma).We also proposed the following secondary hypotheses (a priori), pending other clinical trials becoming available, to examine nutrition more distinctly:3. the mortality rate is different in children who are given enteral nutrition alone versus enteral and parenteral combined;4. the mortality rate is different in children who are given both enteral feeds and parenteral nutrition versus no nutrition.

SEARCH METHODS

In this updated review we searched: the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 2); Ovid MEDLINE (1966 to February 2016); Ovid EMBASE (1988 to February 2016); OVID Evidence-Based Medicine Reviews; ISI Web of Science - Science Citation Index Expanded (1965 to February 2016); WebSPIRS Biological Abstracts (1969 to February 2016); and WebSPIRS CAB Abstracts (1972 to February 2016). We also searched trial registries, reviewed reference lists of all potentially relevant studies, handsearched relevant conference proceedings, and contacted experts in the area and manufacturers of enteral and parenteral nutrition products. We did not limit the search by language or publication status.

SELECTION CRITERIA

We included studies if they were randomized controlled trials; involved paediatric patients, aged one day to 18 years of age, who were cared for in a paediatric intensive care unit setting (PICU) and had received nutrition within the first seven days of admission; and reported data for at least one of the pre-specified outcomes (30-day or PICU mortality; length of stay in PICU or hospital; number of ventilator days; and morbid complications, such as nosocomial infections). We excluded studies if they only reported nutritional outcomes, quality of life assessments, or economic implications. Furthermore, we did not address other areas of paediatric nutrition, such as immunonutrition and different routes of delivering enteral nutrition, in this review.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the searches, applied the inclusion criteria, and performed 'Risk of bias' assessments. We resolved discrepancies through discussion and consensus. One author extracted data and a second checked data for accuracy and completeness. We graded the evidence based on the following domains: study limitations, consistency of effect, imprecision, indirectness, and publication bias.

MAIN RESULTS

We identified only one trial as relevant. Seventy-seven children in intensive care with burns involving more than 25% of the total body surface area were randomized to either enteral nutrition within 24 hours or after at least 48 hours. No statistically significant differences were observed for mortality, sepsis, ventilator days, length of stay, unexpected adverse events, resting energy expenditure, nitrogen balance, or albumin levels. We assessed the trial as having unclear risk of bias. We consider the quality of the evidence to be very low due to there being only one small trial. In the most recent search update we identified a protocol for a relevant randomized controlled trial examining the impact of withholding early parenteral nutrition completing enteral nutrition in pediatric critically ill patients; no results have been published.

AUTHORS' CONCLUSIONS

There was only one randomized trial relevant to the review question. Research is urgently needed to identify best practices regarding the timing and forms of nutrition for critically ill infants and children.

High-protein hypocaloric vs normocaloric enteral nutrition in critically ill patients: A randomized clinical trial

PURPOSE

Appropriate caloric intake in critically ill patients receiving enteral nutrition is controversial. This study evaluates the impact of different caloric regimens on severity of organ failure measured with Sequential Organ Failure Assessment (SOFA).

MATERIALS AND METHODS

We conducted a randomized prospective controlled trial. Study population included adult intensive care unit (ICU) patients expected to require enteral nutrition for more than 96 hours. Goals in the intervention group were hypocaloric (15 kcal/kg per day) enteral nutrition compared to normocaloric (25 kcal/kg per day) enteral nutrition, both with hyperproteic intake (1.7 g of protein/kg per day). Primary end point was change in SOFA score (ΔSOFA) from baseline at 48 hours. Secondary end points were ΔSOFA at 96 hours, insulin requirements, hyperglycemia or hypoglycemic episodes, length of ICU stay, days on ventilator, and 28-day mortality.

RESULTS

After screening 443 patients, 120 patients were analyzed. There were no differences between groups in baseline characteristics. We did not find a statistically significant difference in ΔSOFA at 48 hours. Patients in the hypocaloric group showed lower average daily insulin requirements and percentage of patients requiring any insulin.

CONCLUSIONS

Hyperproteic, hypocaloric nutrition did not show different outcomes compared to normocaloric nutrition, except lower insulin requirements. Hypocaloric nutrition could provide a more physiologic approach with lower need for care and metabolic impact.

Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults

BACKGROUND

The appropriate caloric goal for critically ill adults is unclear. We evaluated the effect of restriction of nonprotein calories (permissive underfeeding), as compared with standard enteral feeding, on 90-day mortality among critically ill adults, with maintenance of the full recommended amount of protein in both groups.

METHODS

At seven centers, we randomly assigned 894 critically ill adults with a medical, surgical, or trauma admission category to permissive underfeeding (40 to 60% of calculated caloric requirements) or standard enteral feeding (70 to 100%) for up to 14 days while maintaining a similar protein intake in the two groups. The primary outcome was 90-day mortality.

RESULTS

Baseline characteristics were similar in the two groups; 96.8% of the patients were receiving mechanical ventilation. During the intervention period, the permissive-underfeeding group received fewer mean (±SD) calories than did the standard-feeding group (835±297 kcal per day vs. 1299±467 kcal per day, P<0.001; 46±14% vs. 71±22% of caloric requirements, P<0.001). Protein intake was similar in the two groups (57±24 g per day and 59±25 g per day, respectively; P=0.29). The 90-day mortality was similar: 121 of 445 patients (27.2%) in the permissive-underfeeding group and 127 of 440 patients (28.9%) in the standard-feeding group died (relative risk with permissive underfeeding, 0.94; 95% confidence interval [CI], 0.76 to 1.16; P=0.58). No serious adverse events were reported; there were no significant between-group differences with respect to feeding intolerance, diarrhea, infections acquired in the intensive care unit (ICU), or ICU or hospital length of stay.

CONCLUSIONS

Enteral feeding to deliver a moderate amount of nonprotein calories to critically ill adults was not associated with lower mortality than that associated with planned delivery of a full amount of nonprotein calories. (Funded by the King Abdullah International Medical Research Center; PermiT Current Controlled Trials number, ISRCTN68144998.).

Hypocaloric Enteral Nutrition Protects against Hypoglycemia Associated with Intensive Insulin Therapy Better than Intravenous Dextrose

Intensive insulin therapy treats hyperglycemia but increases the risk of hypoglycemia. Typically, intravenous dextrose is given to prevent hypoglycemia; however, enteral nutrition is preferred. We hypothesized that the provision of hypocaloric enteral nutrition would protect against hypoglycemia. A retrospective analysis was performed evaluating patients treated with intensive insulin therapy comparing the use of enteral nutrition versus a dextrose-only intravenous solution. Nutrition in the 2 hours before each blood glucose test was assessed, and the association with hypoglycemia (50 mg/dL or less) evaluated. Risk of hypoglycemia as a function of nutrition type and rate was estimated by multivariable regression. A total of 26,140 blood glucose tests were collected on 1289 patients. Hypoglycemia occurred in 6.4 per cent of patients. In regression models, enteral nutrition was the strongest protective factor against hypoglycemia ( P < 0.001) with the largest risk reduction (steepest portion of the curve) occurring at 60 per cent goal. Hypocaloric enteral nutrition showed a greater risk reduction than a peripheral dextrose-only intravenous solution alone. In the setting of intensive insulin therapy, the provision of enteral nutrition, even if hypocaloric, is sufficient to protect against hypoglycemia. Future prospective studies should evaluate the efficacy of enteral nutrition in reducing the risk of hypoglycemia and whether lower rates of hypoglycemia correspond to improved outcomes.

Why critically ill patients are protein deprived

Critical illness dramatically increases muscle proteolysis and more than doubles the dietary protein requirement. Yet surprisingly, most critically ill patients receive less than half the recommended amount of protein during their stay in a modern intensive care unit. What could explain the wide gap between the recommendations in clinical care guidelines and actual clinical practice? We suggest that an important aspect of the problem is the failure of guidelines to explain the pathophysiology of protein-energy malnutrition and the ways critical illness modifies protein metabolism. The difficulty created by the lack of a framework for reasoning about appropriate protein provision in critical illness is compounded by the many ambiguous and often contradictory ways the word malnutrition is used in the critical care literature. Failing to elucidate these matters, the recommendations for protein provision in the guidelines are incoherent, unconvincing, and easy to ignore.

Appropriate protein provision in critical illness: a systematic and narrative review

BACKGROUND

Widely varying recommendations have been published with regard to the appropriate amount of protein or amino acids to provide in critical illness.

OBJECTIVE

We carried out a systematic review of clinical trials that compared the metabolic or clinical effects of different protein intakes in adult critical illness and comprehensively reviewed all of the available evidence pertinent to the safe upper limit of protein provision in this setting.

DESIGN

MEDLINE was searched for clinical trials published in English between 1948 and 2012 that provided original data comparing the effects of different levels of protein intake on clinically relevant outcomes and evidence pertinent to the safe upper limit of protein provision to critically ill adults.

RESULTS

The limited amount and poor quality of the evidence preclude conclusions or clinical recommendations but strongly suggest that 2.0-2.5 g protein substrate · kg normal body weight⁻¹ · d⁻¹ is safe and could be optimum for most critically ill patients. At the present time, most critically ill adults receive less than half of the most common current recommendation, 1.5 g protein · kg⁻¹ · d⁻¹, for the first week or longer of their stay in an intensive care unit.

CONCLUSION

There is an urgent need for well-designed clinical trials to identify the appropriate level of protein provision in critical illness.

Metabolic considerations in management of surgical patients

Metabolic changes after surgery, trauma, or serious illness have a complex pathophysiology. The early posttraumatic stress response is physiologic and associated with a state of hyperinflammation, increased oxygen consumption, and increased energy expenditure. These are part of a systemic reaction that encompasses a wide range of endocrinological, immunologic, and hematological effects. Surgery initiates changes in metabolism that can affect virtually all organs and tissues; the metabolic response results in hormone-mediated mobilization of endogenous substrates that leads to stress catabolism. Hypercatabolism has been associated with severe complications related to hyperglycemia, hypoproteinemia, and immunosuppression. Proper metabolic support is essential to restore homeostasis and ensure survival.

Review article: permissive underfeeding in short-term nutritional support

BACKGROUND

The importance of adequate nutritional support in selected patient groups is well established. Traditionally, the amounts of macronutrients provided have been based on a perceived need to achieve, if not exceed, energy and protein balance. In recent years, there has been increasing interest in the concept of 'permissive underfeeding'.

AIM

To determine whether or not there is evidence of benefit for permissive underfeeding in selected groups.

METHODS

Studies were identified from MEDLINE, Embase and PubMed databases and the Cochrane collaboration. The search was limited from January 1950 to January 2010. Further searches were made from the references of original articles. The literature search revealed 591 abstracts of relevant studies. All abstracts were initially reviewed by the primary author (AO) and those that did not fulfil the inclusion criteria were discarded. The remaining articles were requested and were reviewed independently by two authors (AO, JM).

RESULTS

Twelve studies were included in the final analysis. Eight of these were randomized interventional trials. Three were prospective cohort studies and one was a retrospective analysis.

CONCLUSION

This review suggests that permissive underfeeding may be associated with improved outcomes and reduced morbidity in patients requiring short-term nutritional support.

Considering energy deficit in the intensive care unit

PURPOSE OF REVIEW

A discrepancy has emerged between experts' recommendations on how to feed ICU patients according to their requirements using parenteral nutrition, if enteral nutrition is not reaching the target. This review describes the differences in the recent guidelines issued by the American Society of Parenteral and Enteral Nutrition (ASPEN) and the European Society of Clinical Nutrition and Metabolism (ESPEN) regarding these aspects.

RECENT FINDINGS

ASPEN/Society of Critical Care medicine (SCCM) experts hesitate to recommend the administration of parenteral nutrition to nonmalnourished ICU patients receiving some but not an adequate amount of enteral feeding during the first 7-10 days after admission. ESPEN guidelines recommend to compensate the deficit by adding parenteral nutrition after 24-48 h. These recommendations are mainly based on observational studies showing a strong correlation between negative energy balance and morbidity-mortality.

SUMMARY

The energy deficit accumulated by underfed ICU patients during the first days of stay may play an important role in ICU and hospital outcomes for long-staying ICU patients. To reach calorie requirements by artificial nutritional support without harming the patient is still a subject of debate. Future studies, some already on their way will clarify this discussion.

Feeding management of sick neonatal foals

Nutritional support of the foal can be challenging because of the constant changes in nutritional requirements and dietary composition during the transition from neonate to weanling. Additional complexity arises because of dilemmas regarding the means and route of delivery of nutrition to the foal, and the possibility that metabolic dysfunction may impair the ability of the foal to use nutrients appropriately. This article provides practical information on enteral and parenteral nutritional support of sick neonatal foals. The potential benefits of a conservative, hypocaloric feeding strategy, particularly in the very sick patient, are also discussed.

Nutritional support for critically ill children

BACKGROUND

Nutritional support in the critically ill child has not been well investigated and is a controversial topic within paediatric intensive care. There are no clear guidelines as to the best form or timing of nutrition in critically ill infants and children.

OBJECTIVES

To assess the impact of enteral and total parenteral nutrition on clinically important outcomes for critically ill children.

SEARCH STRATEGY

We searched: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 1); Ovid MEDLINE (1966 to February 2007); Ovid EMBASE (1988 to February 2007); OVID Evidence-Based Medicine Reviews; ISI Web of Science - Science Citation Index Expanded (1965 to February 2007); WebSPIRS Biological Abstracts (1969 to February 2007); and WebSPIRS CAB Abstracts (1972 to February 2007). We also searched trial registries; reviewed reference lists of all potentially relevant studies; handsearched relevant conference proceedings; and contacted experts in the area and manufacturers of enteral and parenteral nutrition products. We did not limit the search by language or publication status.

SELECTION CRITERIA

We included studies if they were randomized controlled trials; involved paediatric patients, aged one day to 18 years of age, cared for in a paediatric intensive care unit setting (PICU) and received nutrition within the first seven days of admission; and reported data for at least one of the pre-specified outcomes (30-day or PICU mortality; length of stay in PICU or hospital; number of ventilator days; and morbid complications, such as nosocomial infections). We excluded studies if they only reported nutritional outcomes, quality of life assessments, or economic implications. Furthermore, other areas of paediatric nutrition, such as immunonutrition and different routes of delivering enteral nutrition, were not addressed in this review.

DATA COLLECTION AND ANALYSIS

Two authors independently screened searches, applied inclusion criteria, and performed quality assessments. We resolved discrepancies through discussion and consensus. One author extracted data and a second checked data for accuracy and completeness.

MAIN RESULTS

Only one trial was identified as relevant. Seventy-seven children in intensive care with burns involving > 25% of the total body surface area were randomized to either enteral nutrition within 24 hours or after at least 48 hours. No statistically significant differences were observed for mortality, sepsis, ventilator days, length of stay, unexpected adverse events, resting energy expenditure, nitrogen balance, or albumin levels. The trial was assessed as of low methodological quality (based on the Jadad scale) with an unclear risk of bias.

AUTHORS' CONCLUSIONS

There was only one randomized trial relevant to the review question. Research is urgently needed to identify best practices regarding the timing and forms of nutrition for critically ill infants and children.

Bench-to-bedside review: metabolism and nutrition

Acute kidney injury (AKI) develops mostly in the context of critical illness and multiple organ failure, characterized by alterations in substrate use, insulin resistance, and hypercatabolism. Optimal nutritional support of intensive care unit patients remains a matter of debate, mainly because of a lack of adequately designed clinical trials. Most guidelines are based on expert opinion rather than on solid evidence and are not fundamentally different for critically ill patients with or without AKI. In patients with a functional gastrointestinal tract, enteral nutrition is preferred over parenteral nutrition. The optimal timing of parenteral nutrition in those patients who cannot be fed enterally remains controversial. All nutritional regimens should include tight glycemic control. The recommended energy intake is 20 to 30 kcal/kg per day with a protein intake of 1.2 to 1.5 g/kg per day. Higher protein intakes have been suggested in patients with AKI on continuous renal replacement therapy (CRRT). However, the inadequate design of the trials does not allow firm conclusions. Nutritional support during CRRT should take into account the extracorporeal losses of glucose, amino acids, and micronutrients. Immunonutrients are the subject of intensive investigation but have not been evaluated specifically in patients with AKI. We suggest a protocolized nutritional strategy delivering enteral nutrition whenever possible and providing at least the daily requirements of trace elements and vitamins.

Hypocaloric feeding: pros and cons

PURPOSE OF REVIEW

Since the 1980s, hypocaloric feeding has been regularly proposed in the critically ill, although there is no clear definition available, nor evidence-based strategy to support it. We aim to define hypocaloric feeding based on indirect calorimetric data and to discuss patient-relevant clinical outcomes resulting from hypocaloric feeding.

RECENT FINDINGS

Overfeeding and underfeeding both have proven deleterious effects and should be avoided, which requires determination of the patient's total energy requirement. Indirect calorimetry appears as the only precise method to determine such requirements in clinical settings. We define hypocaloric feeding as the delivery of 0.5-0.9 times the resting energy expenditure, isocaloric feeding as 1.1-1.3 times the resting energy expenditure, whereas hypercaloric feeding delivers more than 1.5 times the resting energy expenditure. Whether the patients are lean or obese, all the available predictive equations of energy requirements are grossly inaccurate in more than 30% of cases.

SUMMARY

There is growing evidence that negative energy balances are associated with poor intensive-care-unit and hospital outcome. Using an evidence-based approach, hypocaloric feeding in the critically ill cannot be supported either. Whether the cutoff of tolerance for introducing feeding is 24 h or more is not yet defined and still awaits a prospective trial.