Energy expenditure of patients on ECMO: A prospective pilot study

Nutritional support in the cardiac intensive care unit

Optimal care of critically ill patients in the cardiac intensive care unit includes adequate nutritional support. This review highlights the high prevalence of malnutrition in acute heart failure, acute coronary syndrome, cardiogenic shock, and post-cardiac arrest and its adverse impact on prognosis. There is a lack of robust evidence regarding appropriate nutritional support in this patient population. Initiation of nutritional support with a comprehensive assessment of the patient's nutritional status is critical. High-risk cardiac patients who are not critically ill can receive oral nutrition adapted to individual risk factors or deficiencies, although overfeeding should be avoided in the acute phase. For critically ill patients at risk of or with malnutrition on admission, general principles include initiation of nutritional support within 48 h of admission, preference for enteral over parenteral nutrition, preference for hypocaloric nutrition in the first week of intensive care unit admission, and adequate micronutrient supplementation. Enteral nutrition in haemodynamically unstable patients carries a risk, albeit low, of intestinal ischaemia. In the case of malnutrition, the risk of refeeding syndrome should always be considered.

Measurement and estimation of energy in the critically ill

PURPOSE OF REVIEW

Recent changes in guidelines recommendation during early phase of critical illness and use of indirect calorimetry. The aim of this review is to discuss methods of determining energy requirements in the critically ill and highlight factors impacting resting energy expenditure.

RECENT FINDING

An appraisal of recent literature discussing indirect calorimetry guided-nutrition potential benefits or pitfalls. Recent attempts to devise strategy and pilot indirect calorimetry use in the critically ill patients requiring continuous renal replacement therapy or extracorporeal membrane oxygenation are also discussed. Additionally, we briefly touched on variability between guidelines recommended energy target and measured energy expenditure for adult critically ill patients with obesity.

SUMMARY

While energy requirement in the critically ill continues to be an area of controversy, recent guidelines recommendations shift toward providing less aggressive calories during acute phase of illness in the first week of ICU.Use of indirect calorimetry may provide more accurate energy target compared to the use of predictive equations. Despite the absence of literature to support long term mortality benefits, there are many potential benefits for the use of indirect calorimetry when available.

Challenges of Nutrition Support in Pediatric Patients Requiring Extracorporeal Membrane Oxygenation

Nutrition support in critically ill infants and children remains an integral part of providing optimal care for these patients. The pediatric patient requiring extracorporeal membrane oxygenation therapy faces specific challenges to the provision of suitable nutrition support. In this review, we aimed to summarize the existing literature around some of the more challenging aspects of delivering appropriate nutrition to children receiving extracorporeal membrane oxygenation.

Nutrition support for patients on mechanical circulatory support

PURPOSE OF REVIEW

No specific guidelines on medical nutrition therapy (MNT) in patients on different types of mechanical circulatory support (MCS) devices yet exist and overall evidence is limited. The purpose of this narrative review is to provide an overview about current existing evidence, which might be of underrecognized importance for the patients' short-term and long-term clinical and functional outcomes.

RECENT FINDINGS

Patients on MCS inherit substantial metabolic, endocrinologic, inflammatory, and immunologic alterations, and together with the specificities of MCS therapy, technical modalities of respective devices, and concomitant medication, the consideration of individualized MNT approaches is indicated in routine clinical practice. Exemplarily, the evaluation of the patients' individual nutrition status, determination of nutrition targets, progressive increase of energy and protein supply throughout the different phases of disease, prevention of micronutrient deficiencies, implementation of nutrition protocols, appropriate monitoring strategies, and continuous quality improvement are essential elements of MNT in patients on MCS.

SUMMARY

The importance of MNT for patients on MCS still often remains underrecognized, which might be of particular relevance in view of the significant metabolic alterations, the long treatment period, and severity of illness in these patients. Further research on more targeted MNT approaches in those patients is urgently needed for the generation of evidence-based guidelines for this specific cohort of critically ill patients.

Modified indirect calorimetry for patients on venoarterial extracorporeal membrane oxygenation: a pilot feasibility study

BACKGROUND/OBJECTIVES

Traditional indirect calorimetry is unable to capture complete gas exchange in patients receiving venoarterial extracorporeal membrane oxygenation (VA ECMO). We aimed to determine the feasibility of using a modified indirect calorimetry protocol in patients receiving VA ECMO, report measured energy expenditure (EE) and compare EE to control critically ill patients.

SUBJECTS/METHODS

Mechanically ventilated adult patients receiving VA ECMO were included. EE was measured within 72 h of VA ECMO commencement (timepoint one [T1]) and on approximately day seven of Intensive Care Unit (ICU) admission (timepoint two [T2]). Traditional indirect calorimetry via the ventilator was combined with calculations of oxygen consumption and carbon dioxide production derived from pre- and post-ECMO membrane blood gas analyses. Completion of ≥60% EE measurements was deemed feasible. Measured EE was compared between T1 and T2 and to control patients not receiving VA ECMO. Data is presented as n(%) and median[interquartile range (IQR)].

RESULTS

Twenty-one patients were recruited; 16(76%) male, aged 55[42-64] years. The protocol was feasible to complete at T1 (14(67%)) but not at T2 (7(33%)) due to predominantly ECMO decannulation, extubation or death. EE was 1454[1213-1860] at T1 and 1657[1570-2074] kcal/d at T2 (P = 0.043). In patients receiving VA ECMO versus controls, EE was 1577[1434-1801] versus 2092[1609-2272] kcal/d, respectively (P = 0.056).

CONCLUSION

Modified indirect calorimetry is feasible early in admission to ICU but is not possible in all patients receiving VA ECMO, especially later in admission. EE increases during the first week of ICU admission but may be lower than EE in control critically ill patients.

Nutrition Support in Critically Ill Cancer Patient Receiving Extracorporeal Membrane Oxygenation: A Case Report

Adequate nutritional support is crucial in preventing complications and improving outcomes in critically ill patients. Extracorporeal membrane oxygenation (ECMO) is a mode of supportive care for patients with respiratory and/or cardiac failure. ECMO patients frequently exhibit a hypermetabolic state characterized by protein catabolism and insulin resistance, which can lead to malnutrition. Nutritional therapy is a vital component of intensive care, but its optimal administration for ECMO patients is unknown. This case report aims to provide insights into effective nutritional management for critically ill patients undergoing ECMO therapy. The patient was a 72-year-old male with a history of gastric and lung cancer who underwent a lobectomy complicated by bronchopleural fistula, postoperative bleeding, pneumonia, and acute respiratory distress syndrome (ARDS). The patient's nutritional status was assessed indicating a high risk of malnutrition, using the modified Nutrition Risk in the Critically Ill (mNUTRIC) Score. Nutritional support was administered based on the recommendations of European Society for Clinical Nutrition and Metabolism (ESPEN) and the American Society for Parenteral and Enteral Nutrition (ASPEN), with energy requirements set at 25-30 kcal/kg/d and protein requirements set at 1.2-2.0 g/kg/day. The patient received parenteral nutrition until the enteral nutrition target amount was reached, with zinc supplements for wound healing. The study highlights the need for further research on proactive and effective nutritional support for ECMO patients to improve compliance and prognosis.

Medical nutrition therapy in patients receiving ECMO: Evidence-based guidance for clinical practice

Patients receiving extracorporeal membrane oxygenation (ECMO) inherit substantial disease-associated metabolic, endocrinologic, and immunologic modifications. Along with the technical components of ECMO, the aforementioned alterations may affect patients' needs and feasibility of adequate macronutrient and micronutrient supply and intake. Thus, patients receiving ECMO are at increased risk for iatrogenic malnutrition and require targeted individual medical nutrition therapy (MNT). However, specific recommendations for MNT in patients receiving ECMO are limited and, with some exceptions, based on an evidence base encompassing general patients who are critically ill. Consequently, clinician decision-making for MNT in patients receiving ECMO is unguided, which may further increase nutrition risk, culminating in iatrogenic malnutrition and ultimately affecting patient outcomes. The purpose of this article is to provide educational background and highlight specific points for MNT in adult patients receiving ECMO, which might serve as evidence-based guidance to develop institutional standard operating procedures and nutrition protocols for daily clinical practice.

Measuring the Resting Energy Expenditure in Children on Extracorporeal Membrane Oxygenation: A Prospective Pilot Study

Both overfeeding and underfeeding critically ill children are problematic. This prospective pilot study evaluated the resting energy expenditure in infants and children requiring extracorporeal membrane oxygenation (ECMO) support. An indirect calorimeter was used to measure oxygen consumption (VO 2 ) and carbon dioxide production (VCO 2 ) from the mechanical ventilator. Blood gases were used to determine VO 2 and VCO 2 from the ECMO circuit. Values from the mechanical ventilator and ECMO circuit were added, and the resting energy expenditure (REE) (Kcal/kg/day) was calculated. Measurements were obtained > 24 hours after ECMO support was initiated (day 2 of ECMO), 1 day before ECMO discontinuation or transfer, and 1 day after decannulation. Data were compared with the predicted energy expenditure. Seven patients aged 3 months to 13 years were included. The REE varied greatly both above and below predicted values, from 26 to 154 KCal/kg/day on day 2 of ECMO support. In patients with septic shock, the REE was > 300% above the predicted value on day 2 of ECMO. Before ECMO discontinuation, two of six (33%) children continued to have a REE > 110% of predicted. Three patients had measurements after decannulation, all with a REE < 90% of predicted. REE measurements can be obtained by indirect calorimetry in children receiving ECMO support. ECMO may not provide metabolic rest for all children as a wide variation in REE was observed. For optimal care, individual testing should be considered to match calories provided with the metabolic demand.

Resting Energy Expenditure of Patients on Venovenous Extracorporeal Membrane Oxygenation for Adult Respiratory Distress Syndrome: A Pilot Study

OBJECTIVES

The objectives of this study were to 1) in patients without pulmonary function, determine resting energy expenditure (REE) in venovenous extracorporeal membrane oxygenation (ECMO) acute respiratory distress syndrome (ARDS) patients by paralysis status and 2) determine the threshold tidal volume (TV) associated with meaningful gas exchange as determined by measurable end-tidal carbon dioxide elimination (etV̇co₂).

DESIGN

Retrospective observational study.

SETTING

A tertiary high ECMO volume academic institution.

PATIENTS/SUBJECTS

Ten adult ARDS patients on venovenous ECMO.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The modified Weir equation, Fick principle, Henderson-Hasselbalch equation, ECMO flow, hemoglobin, and pre and post oxygenator blood gases were used to determine ECMO carbon dioxide production (V̇co₂), ECMO oxygen consumption, and REE. REE values were matched to patients' paralysis status based on medication flowsheets and compared using a paired t test. Linear regression was performed to determine the threshold TV normalized to ideal body weight (IBW) associated with measurable ventilator etV̇co₂, above which meaningful ventilation occurs. When lungs were not functioning, patients had significantly lower mean REE when paralyzed (23.4 ± 2.8 kcal/kg/d) than when not paralyzed (29.2 ± 5.8 kcal/kg/d) (p = 0.02). Furthermore, mean REE was not similar between patients and varied as much as 1.7 times between patients when paralyzed and as much as 1.4 times when not paralyzed. Linear regression showed that ventilator V̇co₂ was measurable and increased linearly when TV was greater than or equal to 0.7 mL/kg.

CONCLUSIONS

REE is patient-specific and varies significantly with and without patient paralysis. When TV exceeds 0.7 mL/kg IBW, ventilator V̇co₂ increases measurably and must be considered in determining total REE.

A Narrative Review of Nutrition Therapy in Patients Receiving Extracorporeal Membrane Oxygenation

The use of extracorporeal membrane oxygenation (ECMO) in patients with severe cardiorespiratory failure has seen significant growth in the last decade. Despite this, there is paucity of data surrounding the optimum nutritional management for ECMO patients. This review aimed to describe current nutrition practices in patients receiving ECMO, critically appraise available studies and identify areas for future research. A literature search was conducted in PubMed, MEDLINE, and CINAHL Plus to identify all randomized trials and observational studies published between July 2000 and July 2020 investigating nutrition practices in critically ill adults receiving ECMO. The primary outcomes were nutritional adequacy, gastrointestinal complications, and physical function. Secondary outcomes included mortality, length of stay, and duration on ECMO support. From a total of 31 studies identified, 12 met the inclusion criteria. Nine observational studies were reviewed following eligibility assessment. Early enteral nutrition was deemed safe and feasible for ECMO patients; however, meeting nutritional targets was challenging. Utilizing alternative nutrition routes is an option, although risks and benefits should be taken into consideration. Data on gastrointestinal complications and other clinical outcomes were inconsistent, and no data were identified investigating the effects of nutrition on the physical and functional recovery of ECMO patients. Nutrition therapy in ECMO patients should be provided in line with current guidelines for nutrition in critical illness until further data are available. Further prospective, randomized studies investigating optimum nutrition practices and effects on clinical and functional outcomes are urgently required.

Nutrition during extracorporeal life support: A review of pathophysiological bases and application of guidelines

BACKGROUND

Patients on extracorporeal life support (ECLS), either for respiratory or cardiac support, are at high risk of malnutrition; guidelines on nutrition in critical care have not incorporated solid evidence regarding these settings. The aim of this narrative review is to gather the available evidence in the existing literature and transpose general principles to the ECLS population.

METHODS

A literature review of observational and interventional studies on nutrition during ECLS, and evaluation of nutrition guidelines in this perspective.

RESULTS

Nutrition is paramount for improving outcomes in ECLS, as well as in critically ill patients. The caloric needs during ECLS can vary according to the severity of the clinical state, sedation, paralysis, and temperature stability. Precise evaluation of energy expenditure by indirect calorimetry is difficult because ECLS is a system dedicated to removing carbon dioxide; however, modified equations composed of carbon dioxide values taken from the membrane lung are available. Guidelines suggest starting early enteral nutrition (EN) with a hypocaloric (70%-80% of the needs) strategy, also in acute states such as septic or cardiogenic shock. Moreover, EN, despite previous concerns, is feasible in prone position, an increasingly adopted strategy during mechanical ventilation. The catabolic state is maximal in these patients, causing a protein and muscular reduction. Therefore, adequate protein delivery should be guaranteed by administering a high protein intake of up to 2 g/kg/day.

CONCLUSIONS

Studies on nutrition tailored to ECLS patients are warranted. Early hypocaloric EN with high protein intake, tailored on indirect calorimetry, may be the most appropriate option.

Which is the best route to achieve nutritional goals in pediatric ECMO patients?

OBJECTIVES

Estimating caloric intake and choosing route of administration are fundamental in the nutritional support of patients being supported by extracorporeal membrane oxygenation (ECMO). The aim of this study was to review the nutritional intervention carried out in a pediatric cohort in a third-level hospital.

METHODS

This was a prospective descriptive study. Age, sex, underlying pathology, Pediatric Risk of Mortality score, ECMO indication, type of care, duration of ECMO support, and prognosis were collected. Type of nutritional support, route of administration, kcal/kg achieved, estimated energy requirements, and percentage of caloric objective (%CO) reached on days 3 and 5 after cannulation were recorded.

RESULTS

Twenty-four venoarterial ECMO runs in 23 patients over a period of 2 y were recorded. Of the 23 patients, 15 were <1 y of age. The underlying pathology in 56.5% was cardiac disease. Three groups were identified: parenteral nutrition (group 0, n = 7), enteral nutrition (group 1, n = 8), and mixed nutrition (group 2, n = 7). The median of the %CO was 33.34 (0-84) on day 3 and 87.75% (78.4-100) on day 5 of ECMO, respectively for group 0; 75.5 (42.25-98.5) and 85% (24.4-107.7) in group 1 and 68.7 (44.4-82.2) and 91.2% (35.5-92) in group 2 (P > 0.05). Children <12 mo of age and cardiac patients represented 85.71% and 71.43% of total patients in group 0. Among the eight episodes of exclusive enteral nutrition, no complications were identified.

CONCLUSION

Enteral nutrition appears to be safe in the setting of hemodynamic stability and absence of contraindications and is equivalent to other nutritional interventions in terms of compliance with estimated energy requirements.

Nutrition in Pediatric Extracorporeal Membrane Oxygenation: A Narrative Review

Extracorporeal membrane oxygenation (ECMO) support is increasingly utilized in quaternary pediatric intensive care units. Metabolic derangements and altered nutritional requirements are common in critically ill children supported on ECMO. However, there remains no consensus on the optimal approach to the prescription of nutrition in these patients. This narrative review aims to summarize the current medical literature on various aspects of nutrition support in pediatric patients on ECMO. These include: (1) nutritional adequacy, (2) pros and cons of feeding on ECMO, (3) enteral vs. parenteral nutrition, and (4) proposed recommendations and future directions for research in this area.

Indirect calorimetry in critical illness: a new standard of care?

PURPOSE OF REVIEW

Review recent literature on the role of indirect calorimetry in critical care nutrition management.

RECENT FINDINGS

Critical illness demands objective, targeted nutritional therapy to prevent adverse effects of underfeeding/over feeding. Thus, all recent societal guidelines recommend indirect calorimetry use to determine energy needs. Very recently, indirect calorimetry technology has finally evolved to allow for accurate, simple, and routine utilization in a wider range of ICU patients. Recent data continues to confirm poor correlation between measured and equation-predicted energy expenditure emphasizing need for indirect calorimetry to be standard of care. This may be particularly true in COVID-19, where significant progressive hypermetabolism and variability in energy expenditure has been shown. Metabolic physiology can change frequently during ICU stay in response to changes in clinical condition or care. Thus, repeated longitudinal indirect calorimetry measures are needed throughout ICU stay to optimize care, with initial data showing improved clinical outcomes when indirect calorimetry targets are utilized.

SUMMARY

Personalized ICU care demands objective data to guide therapy. This includes use of indirect calorimetry to determine energy expenditure and guide ICU nutrition therapy. Long-awaited new innovations in indirect calorimetry technology should finally lead to indirect calorimetry to becoming a fundamental component of modern ICU standard of care and clinical research moving forward.

Energy requirements of long-term ventilated COVID-19 patients with resolved SARS-CoV-2 infection

Background & aims

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can rapidly progress into acute respiratory distress syndrome accompanied by multi-organ failure requiring invasive mechanical ventilation and critical care treatment. Nutritional therapy is a fundamental pillar in the management of hospitalized patients. It is broadly acknowledged that overfeeding and underfeeding of intensive care unit (ICU) patients are associated with increased morbidity and mortality. This study aimed to assess the energy demands of long-term ventilated COVID-19 patients using indirect calorimetry and to evaluate the applicability of established predictive equations to estimate their energy expenditure.

Methods

We performed a retrospective, single-center study in 26 mechanically ventilated COVID-19 patients with resolved SARS-CoV-2 infection in three independent intensive care units. Resting energy expenditure (REE) was evaluated by repetitive indirect calorimetry (IC) measurements. Simultaneously the performance of 12 predictive equations was examined. Patient's clinical data were retrieved from electronic medical charts. Bland-Altman plots were used to assess agreement between measured and calculated REE.

Results

Mean mREE was 1687 kcal/day and 20.0 kcal relative to actual body weight (ABW) per day (kcal/kg/day). Longitudinal mean mREE did not change significantly over time, although mREE values had a high dispersion (SD of mREE ±487). Obese individuals were found to have significantly increased mREE, but lower energy expenditure relative to their body mass. Calculated REE showed poor agreement with mREE ranging from 33 to 54%.

Conclusion

Resolution of SARS-CoV-2 infection confirmed by negative PCR leads to stabilization of energy demands at an average 20 kcal/kg in ventilated critically ill patients. Due to high variations in mREE and low agreement with calculated energy expenditure IC remains the gold standard for the guidance of nutritional therapy.

Point-Counterpoint: Indirect Calorimetry Is Essential for Optimal Nutrition Therapy in the Intensive Care Unit

Iatrogenic malnutrition and underfeeding are ubiquitous in intensive care units (ICUs) worldwide for prolonged periods after ICU admission. A major driver leading to the lack of emphasis on timely ICU nutrition delivery is lack of objective data to guide nutrition care. If we are to ultimately overcome current fundamental challenges to effective ICU nutrition delivery, we must all adopt routine objective, longitudinal measurement of energy targets via indirect calorimetry (IC). Key evidence supporting the routine use of IC in the ICU includes (1) universal societal ICU nutrition guidelines recommending IC to determine energy requirements; (2) data showing predictive equations or body weight calculations that are consistently inaccurate and correlate poorly with measured energy expenditure, ultimately leading to routine overfeeding and underfeeding, which are both associated with poor ICU outcomes; (3) recent development and worldwide availability of a new validated, accurate, easy-to-use IC device; and (4) recent data in ICU patients with coronavirus disease 2019 (COVID-19) showing progressive hypermetabolism throughout ICU stay, emphasizing the inaccuracy of predictive equations and marked day-to-day variability in nutrition needs. Thus, given the availability of a new validated IC device, these findings emphasize that routine longitudinal IC measures should be considered the new standard of care for ICU and post-ICU nutrition delivery. As we would not deliver vasopressors without accurate blood pressure measurements, the ICU community is only likely to embrace an increased focus on the importance of early nutrition delivery when we can consistently provide objective IC measures to ensure personalized nutrition care delivers the right nutrition dose, in the right patient, at the right time to optimize clinical outcomes.

Energy expenditure and indirect calorimetry in critical illness and convalescence: current evidence and practical considerations

The use of indirect calorimetry is strongly recommended to guide nutrition therapy in critically ill patients, preventing the detrimental effects of under- and overfeeding. However, the course of energy expenditure is complex, and clinical studies on indirect calorimetry during critical illness and convalescence are scarce. Energy expenditure is influenced by many individual and iatrogenic factors and different metabolic phases of critical illness and convalescence. In the first days, energy production from endogenous sources appears to be increased due to a catabolic state and is likely near-sufficient to meet energy requirements. Full nutrition support in this phase may lead to overfeeding as exogenous nutrition cannot abolish this endogenous energy production, and mitochondria are unable to process the excess substrate. However, energy expenditure is reported to increase hereafter and is still shown to be elevated 3 weeks after ICU admission, when endogenous energy production is reduced, and exogenous nutrition support is indispensable. Indirect calorimetry is the gold standard for bedside calculation of energy expenditure. However, the superiority of IC-guided nutritional therapy has not yet been unequivocally proven in clinical trials and many practical aspects and pitfalls should be taken into account when measuring energy expenditure in critically ill patients. Furthermore, the contribution of endogenously produced energy cannot be measured. Nevertheless, routine use of indirect calorimetry to aid personalized nutrition has strong potential to improve nutritional status and consequently, the long-term outcome of critically ill patients.

Enteral Nutrition Safety With Advanced Treatments: Extracorporeal Membrane Oxygenation, Prone Positioning, and Infusion of Neuromuscular Blockers

This review aims at assessing the safety and efficacy of enteral nutrition in critically ill patients receiving extracorporeal membrane oxygenation, prone positioning, and infusion of neuromuscular blockers. Existing data from randomized controlled trials demonstrate the survival benefit of early enteral nutrition in critically ill patients. Observational data have demonstrated that enteral nutrition in patients receiving extracorporeal membrane oxygenation, prone positioning, and infusion of neuromuscular blockers is generally safe. However, these patients are at increased risk for gastrointestinal complications from enteral nutrition because of critical illness-induced gastrointestinal dysfunction; associated shock; the concomitant use of vasopressor agents, sedatives, and narcotics; possibly mesenteric circulatory compromise; and regurgitation associated with prone positioning. Therefore, early enteral nutrition is generally recommended in these patients in the absence of severe gastrointestinal dysfunction or shock. To reduce the complications, early nutrition should be advanced gradually (trophic feeding or permissive underfeeding), the bed should be tilted to a maximum of 30°, and concentrated nutritional formulae and the use of prokinetics may be considered to treat enteral feeding intolerance. Physicians should be vigilant about monitoring for early signs of acute mesenteric ischemia, which should lead to holding enteral feeding. Parenteral nutrition may be utilized in patients who cannot receive enteral nutrition or are unable to reach their nutrition goals by the end of the first week.

Safety, Tolerability, and Outcomes of Enteral Nutrition in Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is a supportive care system for patients with respiratory or cardiac failure. Patients requiring ECMO are at risk for significant inflammation, prolonged hospitalization, and acquired malnutrition and sarcopenia. Societal guidelines recommend early enteral nutrition in critically ill patients; however, in this population, optimal timing and dose of nutrition remains unknown and fear of reduced splanchnic perfusion, delayed gastric emptying, and bowel ischemia poses a barrier to appropriate energy and protein intake. This narrative review intends to provide an overview of ECMO, highlight the rationale for nutrition support in this population, and review the safety, tolerability, and outcomes associated with enteral nutrition during ECMO.

Strategies for optimal calorie administration in critically ill patients

Nutritional therapy is one of the important treatments in critically ill patients. How to estimate calorie consumption and how to determine an optimal calorie dose are clinical questions of great importance. Although indirect calorimetry is the gold standard for assessing energy expenditure, many intensivists are unable to use this technique. Therefore, the use of formulas, such as the Harris-Benedict equation, or the simple predictive value of 25 kcal/kg/day is reasonable. Several studies and guidelines have shown that the strategies for nutritional therapy depend on the nutritional risk of patients. If patients have low nutritional risks, these estimated values should not be adopted in the acute phase. Until the patient’s condition improves, less than 18 kcal/kg/day might be an optimal calorie target. Contrastingly, cumulative negative energy balance can also be harmful to critically ill patients. Thus, it is important to accurately determine the energy requirement and to make the required changes in the administered calorie dose to go from a strategy of “defense” to that of “offense” in a timely manner. In this article, the concepts of optimal calorie administration in critically ill patients were reviewed.