Optimization of Nutrition Therapy with the Use of Calorimetry to Determine and Control Energy Needs in Mechanically Ventilated Critically Ill Patients: The ONCA Study, a Randomized, Prospective Pilot Study

Longitudinal analysis of caloric requirements in critically ill trauma patients: a retrospective cohort study

PURPOSE

Nutrition is of paramount importance in critically ill trauma patients. However, adequate supply is difficult to achieve, as caloric requirements are unknown. This study investigated caloric requirements over time, based on indirect calorimetry, in critically ill trauma patients.

METHODS

Retrospective cohort study at a tertiary trauma center including critically ill trauma patients who underwent indirect calorimetry 2012-2019. Caloric requirements were assessed as resting energy expenditure (REE) during the intensive care unit stay up to 28 days and analyzed in patient-clustered linear regression analysis.

RESULTS

A total of 129 patients were included. Median REE per day was 2376 kcal. The caloric intake did not meet REE at any time with a median daily deficit of 1167 kcal. In univariable analysis, ISS was not significantly associated with REE over time (RC 0.03, p = 0.600). Multivariable analysis revealed a significant REE increase (RC 0.62, p < 0.001) and subsequent decrease (RC - 0.03, p < 0.001) over time. Age < 65 years (RC 2.07, p = 0.018), male sex (RC 4.38, p < 0.001), and BMI ≥ 35 kg/m2 (RC 6.94, p < 0.001) were identified as independent predictors for higher REE over time. Severe head trauma was associated with lower REE over time (RC - 2.10, p = 0.030).

CONCLUSION

In critically ill trauma patients, caloric requirements significantly increased and subsequently decreased over time. Younger age, male sex and higher BMI were identified as independent predictors for higher caloric requirements, whereas severe head trauma was associated with lower caloric requirements over time. These results support the use of IC and will help to adjust nutritional support in critically ill trauma patients.

Effects of Energy Delivery Guided by Indirect Calorimetry in Critically Ill Patients: A Systematic Review and Meta-Analysis

BACKGROUND

The utility of using indirect calorimetry (IC) to estimate energy needs and methods for its application to this purpose remain unclear. This systematic review investigated whether using IC to estimate energy expenditure in critically ill patients is more meaningful for improving survival than other estimation methods.

METHODS

Comprehensive searches were conducted in MEDLINE using PubMed, Cochrane Central Register of Controlled Trials, and Igaku-Chuo-Zasshi up to March 2023.

RESULTS

Nine RCTs involving 1178 patients were included in the meta-analysis. The evidence obtained suggested that energy delivery by IC improved short-term mortality (risk ratio, 0.86; 95% confidence interval [CI], 0.70 to 1.06). However, the use of IC did not appear to affect the length of ICU stay (mean difference [MD], 0.86; 95% CI, -0.98 to 2.70) or the duration of mechanical ventilation (MD, 0.66; 95% CI, -0.39 to 1.72). Post hoc analyses using short-term mortality as the outcome found no significant difference by target calories in resting energy expenditure, whereas more frequent IC estimates were associated with lower short-term mortality and were more effective in mechanically ventilated patients.

CONCLUSIONS

This updated meta-analysis revealed that the use of IC may improve short-term mortality in patients with critical illness and did not increase adverse events.

Clinical practice guidelines for nutritional assessment and monitoring of adult ICU patients in China

The Chinese Society of Critical Care Medicine (CSCCM) has developed clinical practice guidelines for nutrition assessment and monitoring for patients in adult intensive care units (ICUs) in China. This guideline focuses on nutrition evaluation and metabolic monitoring to achieve optimal and personalized nutrition therapy for critically ill patients. This guideline was developed by experts in critical care medicine and evidence-based medicine methodology and was developed after a thorough review of the system and a summary of relevant trials or studies published from 2000 to July 2023. A total of 18 recommendations were formed and consensus was reached through discussions and reviews by expert groups in critical care medicine, parenteral and enteral nutrition, and surgery. The recommendations are based on currently available evidence and cover several key fields, including screening and assessment, evaluation and assessment of enteral feeding intolerance, metabolic and nutritional measurement and monitoring during nutrition therapy, and organ function evaluation related to nutrition supply. Each question was analyzed according to the Population, Intervention, Comparison, and Outcome (PICO) principle. In addition, interpretations were provided for four questions that did not reach a consensus but may have potential clinical and research value. The plan is to update this nutrition assessment and monitoring guideline using the international guideline update method within 3-5 years.

Clinical applications of body composition and functional status tools for nutrition assessment of hospitalized adults: A systematic review

BACKGROUND

No global consensus exists on diagnostic criteria for malnutrition. Muscular deficits and functional impairments are major components of available malnutrition diagnostic frameworks because these facets of nutrition status significantly impact outcomes. The purpose of this review is to explore which body composition assessment (BCA) and functional status assessment (FSA) tools are being used for nutrition assessment (NA) and monitoring the response to nutrition interventions (RNIs) in adult inpatients.

METHODS

A literature search of Embase, Medline (Ovid), Web of Science, and Cochrane Central was performed to identify studies that used BCA and/or FSA tools for NA (along with an accepted NA diagnostic framework) and/or for monitoring RNI in adult inpatients.

RESULTS

The search yielded 3667 articles; 94 were included in the review. The number of studies using BCA and/or FSA tools for NA was 47 and also 47 for monitoring RNI. Seventy-nine percent of studies used bioimpedance for BCA, and 97% that included FSA utilized handgrip strength. When compared against sets of diagnostic criteria, many of the BCA and FSA tools showed promising associations with nutrition status.

CONCLUSION

Bioimpedance methods are the most widely used bedside BCA tools, and handgrip strength is the most widely used FSA tool; however, these methods are being used with a variety of protocols, algorithms, and interpretation practices in heterogeneous populations. To create a standardized nutrition status assessment process there is a need for validation studies on bedside methods and the development of globally standardized assessment protocols in clinical inpatient settings.

Impact of an interdisciplinary nutrition support team (NST) on the clinical outcome of critically ill patients. A pre/post NST intervention study

BACKGROUND

Intensive care unit (ICU) patients are at particular risk for malnutrition with major impact for outcome and prognosis. Nutrition support teams (NST) have been proposed to improve nutrition care in ICU patients.

OBJECTIVE

To assess the effectiveness of an interdisciplinary NST on anthropometry and clinical outcome of ICU patients.

METHODS

Before NST implementation, we assessed 120 patients (before NST group; SAPS II score 44 ± 16), afterwards 60 patients (after NST group), of whom 29 received NST guidance (after NST + group; SAPS II 65 ± 19) and 31 not (after NST - group; SAPS II, 54 ± 16). The primary outcome parameter was length of stay in the hospital (hospital-LOS). Severity of disease was assessed by the APACHE II score and the nutritional risk (NUTRIC) score.

RESULTS

NST intervention resulted in a more pronounced improvement of disease severity (APACHE II, from 27 ± 8 to 18 ± 6, p < 0.001; NUTRIC, from 7 ± 2 to 4 ± 2, p < 0.001) compared to no NST intervention (APACHE II from 24 ± 7 to 21 ± 7, p < 0.05; NUTRIC from 6 ± 2 to 5 ± 2, p < 0.01). The mean hospital-LOS was not reduced, neither in the NST intervention group nor in the control group without NST intervention. NST intervention failed to improve nutritional status or mortality compared to no NST intervention.

CONCLUSION

In our study the NST intervention had a positive effect on disease severity, but failed to improve mortality, hospital-LOS or nutritional status in ICU patients, likely because of a large patient heterogeneity.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02200874).

The effect of indirect calorimetry guided isocaloric nutrition on mortality in critically ill patients-a systematic review and meta-analysis

Indirect calorimetry (IC)-guided nutrition might positively affect the clinical outcome of critically ill patients. In this systematic review and meta-analysis, our objective was to assess the benefit of isocaloric nutrition guided by IC, compared to hypocaloric nutrition, for critically ill patients admitted to the intensive care unit (ICU). We performed a systematic review of all randomized controlled trials published through January 2021, assessing the benefit of isocaloric nutrition guided by IC. The primary outcome was 28-day all-cause mortality. Secondary outcomes were ICU and 90-day all-cause mortality, rate of nosocomial infections, and adverse events. Four trials evaluating 1052 patients were included. Patients treated with isocaloric nutrition had a lower 28-day mortality rate (risk ratio (RR) 0.79, 95% confidence interval (CI) 0.63-0.99, P = 0.04). No between-group difference was found in ICU and 90-day mortality (RR 0.92, 95% CI 0.68-1.23, P = 0.56 and RR 0.88, 95% CI 0.72-1.07; P = 0.2, respectively) and in the rate of nosocomial infections (RR 1.15, 95% CI 0.77-1.72, P = 0.51). A pooled analysis of studies that evaluated the benefit of isocaloric nutrition guided by IC, for critically ill patients in the ICU, has shown reduced 28-day mortality. However, there was no difference in 90-day mortality and nosocomial infection rate.

Feasibility of achieving different protein targets using a hypocaloric high-protein enteral formula in critically ill patients

Background and aims

Combining energy and protein targets during the acute phase of critical illness is challenging. Energy should be provided progressively to reach targets while avoiding overfeeding and ensuring sufficient protein provision. This prospective observational study evaluated the feasibility of achieving protein targets guided by 24-h urinary nitrogen excretion while avoiding overfeeding when administering a high protein-to-energy ratio enteral nutrition (EN) formula.

Methods

Critically ill adult mechanically ventilated patients with an APACHE II score > 15, SOFA > 4 and without gastrointestinal dysfunction received EN with hypocaloric content for 7 days. Protein need was determined by 24-h urinary nitrogen excretion, up to 1.2 g/kg (Group A, N = 10) or up to 1.5 g/kg (Group B, N = 22). Variables assessed included nitrogen intake, excretion, balance; resting energy expenditure (REE); phase angle (PhA); gastrointestinal tolerance of EN.

Results

Demographic characteristics of groups were similar. Protein target was achieved using urinary nitrogen excretion measurements. Nitrogen balance worsened in Group A but improved in Group B. Daily protein and calorie intake and balance were significantly increased in Group B compared to Group A. REE was correlated to PhA measurements. Gastric tolerance of EN was good.

Conclusions

Achieving the protein target using urinary nitrogen loss up to 1.5 g/kg/day was feasible in this hypercatabolic population. Reaching a higher protein and calorie target did not induce higher nitrogen excretion and was associated with improved nitrogen balance and a better energy intake without overfeeding. PhA appears to be related to REE and may reflect metabolism level, suggestive of a new phenotype for nutritional status.

Trial registration 0795-18-RMC.

Effect of an intensified individual nutrition therapy on serum metabolites in critically ill patients - A targeted metabolomics analysis of the ONCA study

PURPOSE

The effect of medical nutrition on serum metabolomics has been poorly explored. The aim of the study was to investigate the relation between energy supply and metabolic profiles in critically ill patients.

MATERIALS AND METHODS

Twenty mechanically ventilated patients on enteral nutrition (EN) or enteral/parenteral nutrition (EN/PN) were randomized into two groups. One group received an individual energy supply based on indirect calorimetry (IC group, n = 9), the other group received a standard energy supply based on a formula, the standard care group (SC group, n = 11). Targeted metabolomics was performed in early-, late- and post-acute metabolic phase.

RESULTS

Individual versus standard care energy supply resulted in a metabolite class separation between the IC and the SC group (P < 0.001). In the SC group concentrations of four glucogenic amino acids and three biogenic amines increased between the early- and late-acute metabolic phase (P < 0.05). The metabolomics pattern differed between the routes of nutrition administration (P < 0.01).

CONCLUSIONS

The amount of energy supply by EN or PN, besides other factors, seems to modulate serum metabolites. Nutrition therapy based on individualized energy supply is associated with a reduction of metabolites reflecting catabolism. Therefore, metabolomics could be a new tool to determine metabolic phases in critically ill patients.

Energy expenditure and delivery: does the Micawber principle apply during critical illness?

PURPOSE OF REVIEW

To determine from existing literature if achieving energy balance in critically ill patients improves outcome. Only randomized clinical trials were considered. Furthermore, the intent had to be that energy intake of the treatment group would reach 100% of requirement, and that the requirement was measured and not estimated.

RECENT FINDINGS

Six studies meeting the above criteria were identified. Truly positive energy balance was rarely achieved in these studies and protein intake was a confounder because it often varied with the energy intake. The two studies in which energy balance came closest to 100% did suggest clinical benefit, but in both of these studies protein intake was also higher in the high-energy intake group.

SUMMARY

The question posed cannot be fully answered based on the available literature. There are some signals that the pursuit of energy balance in critically ill patients might be favorable, but significant uncertainty remains.

Energy delivery guided by indirect calorimetry in critically ill patients: a systematic review and meta-analysis

BACKGROUND

The use of indirect calorimetry (IC) is increasing due to its precision in resting energy expenditure (REE) measurement in critically ill patients. Thus, we aimed to evaluate the clinical outcomes of an IC-guided nutrition therapy compared to predictive equations strategy in such a patient population.

METHODS

We searched PubMed, EMBASE, and Cochrane library databases up to October 25, 2020. Randomized controlled trials (RCTs) were included if they focused on energy delivery guided by either IC or predictive equations in critically ill adults. We used the Cochrane risk-of-bias tool to assess the quality of the included studies. Short-term mortality was the primary outcome. The meta-analysis was performed with the fixed-effect model or random-effect model according to the heterogeneity.

RESULTS

Eight RCTs with 991 adults met the inclusion criteria. The overall quality of the included studies was moderate. Significantly higher mean energy delivered per day was observed in the IC group, as well as percent delivered energy over REE targets, than the control group. IC-guided energy delivery significantly reduced short-term mortality compared with the control group (risk ratio = 0.77; 95% CI 0.60 to 0.98; I² = 3%, P = 0.03). IC-guided strategy did not significantly prolong the duration of mechanical ventilation (mean difference [MD] = 0.61 days; 95% CI - 1.08 to 2.29; P = 0.48), length of stay in ICU (MD = 0.32 days; 95% CI - 2.51 to 3.16; P = 0.82) and hospital (MD = 0.30 days; 95% CI - 3.23 to 3.83; P = 0.87). Additionally, adverse events were similar between the two groups.

CONCLUSIONS

This meta-analysis indicates that IC-guided energy delivery significantly reduces short-term mortality in critically ill patients. This finding encourages the use of IC-guided energy delivery during critical nutrition support. But more high-quality studies are still needed to confirm these findings.

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.

Nutrition management of obese critically ill adults: A survey of critical care dietitians in Australia and New Zealand

BACKGROUND

Guideline recommendations for nutrition therapy in critically ill obese adults are inconsistent. This study aimed to describe how dietitians working in an intensive care unit (ICU) in Australia and New Zealand (ANZ) approach managing the nutritional needs of an obese, critically ill adult.

METHODS

Invitations to participate were via personal email communication. The survey was also disseminated through a research email list and a dietitian-based newsletter. The multiple-choice case-based survey consisted of 12 questions relating to nutrition prescription and were based on international nutrition guideline recommendations including (i) weight used in energy and protein predictive equations; (ii) energy and protein prescription at ICU admission and day 7, (iii) commencement of enteral nutrition, and; (iv) use of supplemental protein. Data are reported as n (%).

RESULTS

Sixty-three dietitians participated in the survey. Most commonly, adjusted body weight calculated as 'weight at BMI 25 kg/m² + 25% excess weight' was used in equations to guide energy (44 respondents, 70%) and protein (39 respondents, 62%) prescription. At day 1, energy and protein prescription was most commonly based on the European Society of Parenteral and Enteral Nutrition (ESPEN) guideline recommendation of 20-25 kcal/kg (39 respondents, 62%) and 1.3 g protein/kg adjusted body weight (36 respondents, 57%). Thirteen (21%) respondents had an indirect calorimetry device in their ICU to measure energy expenditure. On day 7, the ESPEN recommendations were again the most common method used for prescribing energy (30 respondents, 48%) and protein (23 respondents. 48%) needs. Thirty-eight dietitians (60%) reported they would use early supplemental protein to meet protein requirements.

CONCLUSIONS

ICU dietitians in ANZ who responded to the survey most commonly report using the ESPEN ICU guideline recommendations (20-25 kcal/kg and 1.3 g protein/kg adjusted body weight) to guide nutrition prescription in an obese critically ill adult. Prospective studies are required to confirm these findings.

Quantifying Response to Nutrition Therapy During Critical Illness: Implications for Clinical Practice and Research? A Narrative Review

Critical illness causes substantial muscle loss that adversely impacts recovery and health-related quality of life. Treatments are therefore needed that reduce mortality and/or improve the quality of survivorship. The purpose of this Review is to describe both patient-centered and surrogate outcomes that quantify responses to nutrition therapy in critically ill patients. The use of these outcomes in randomized clinical trials will be described and the strengths and limitations of these outcomes detailed. Outcomes used to quantify the response of nutrition therapy must have a plausible mechanistic relationship to nutrition therapy and either be an accepted measure for the quality of survivorship or highly likely to lead to improvements in survivorship. This Review identified that previous trials have utilized diverse outcomes. The variety of outcomes observed is probably due to a lack of consensus as to the most appropriate surrogate outcomes to quantify response to nutrition therapy during research or clinical practice. Recent studies have used, with some success, measures of muscle mass to evaluate and monitor nutrition interventions administered to critically ill patients.

Is Energy Delivery Guided by Indirect Calorimetry Associated With Improved Clinical Outcomes in Critically Ill Patients? A Systematic Review and Meta-analysis

Background:

Indirect calorimetry (IC) is recommended to guide energy delivery over predictive equations in critical illness due to its precision. However, the impact of using IC to measure energy expenditure on clinical outcomes is uncertain.

Objective:

To evaluate whether using IC to measure energy expenditure to inform energy delivery reduced hospital mortality and improved other important outcomes compared to using predictive equations in critically ill adults.

Methods:

A systematic literature review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guideline. Medline, Embase, CINAHL, and the Cochrane Library were searched for studies using IC to guide energy delivery compared to a predictive equation in adult critically ill patients with the primary outcome (hospital mortality) or any of the secondary outcomes reported (including but not limited to hospital and intensive care unit (ICU) length of stay (LOS) and duration mechanical ventilation (MV). Risk of bias within studies was assessed using the Cochrane “Risk of Bias” 1 tool. Random-effect meta-analyses were used when heterogeneity between studies existed (I² > 50%). Data are reported as median (interquartile range [IQR]), binomial outcomes as odds ratio (OR), 95% confidence interval (CI), and continuous outcomes as mean difference (MD).

Results:

Of 4060 articles, 4 randomized controlled trials were identified with 396 patients included in analysis. Three studies were considered low risk of bias and 1 as high risk. Two studies reported hospital mortality (n = 130 and 40 participants, respectively). When combined, no association between IC-guided energy delivery and hospital mortality was found (OR = 0.81, 95% CI = [0.25, 2.67], P = 0.73, I² = 52). No differences were reported with ICU mortality and hospital LOS between groups, but ICU LOS and duration of MV varied across all studies. According to the meta-analysis, no differences were observed in ICU LOS (MD = 1.39, 95% CI = [–5.01, 7.79], P = 0.67, I² = 81%), although the duration of MV was increased when energy delivery was guided by IC (MD = 2.01, 95% CI = [0.45, 3.57], P = 0.01, I² = 26%). In all 4 studies, prescribed energy targets were more closely met when energy delivery was informed by IC compared to a predictive equation. Three studies reported the percentage delivered versus the prescribed energy target, with the median (IQR) delta between the IC and predictive equation arms 19% (10%-32%).

Conclusion:

Limited data exist to assess the impact of using IC to inform energy delivery in comparison to predictive equations on hospital mortality. The association of IC use with other important outcomes, including duration of MV, needs to be further explored before definitive conclusions can be made.

Nutrition therapy in critical illness: a review of the literature for clinicians

Nutrition therapy during critical illness has been a focus of recent research, with a rapid increase in publications accompanied by two updated international clinical guidelines. However, the translation of evidence into practice is challenging due to the continually evolving, often conflicting trial findings and guideline recommendations. This narrative review aims to provide a comprehensive synthesis and interpretation of the adult critical care nutrition literature, with a particular focus on continuing practice gaps and areas with new data, to assist clinicians in making practical, yet evidence-based decisions regarding nutrition management during the different stages of critical illness.

Factors associated with discrepancy between prescribed and administered enteral nutrition in general ICU

BACKGROUND

Discrepancy between prescribed and administered enteral nutrition (EN) is a common problem during intensive care. The aim of this study was to find out the success rate and factors associated with inadequacy of enteral nutrition in a mixed general intensive care unit (ICU).

METHODS

This was a retrospective single-center study of 892 patients with ICU length of stay (LOS) ≥4 days. The factors associated with adequacy of enteral nutrition on day 4 were analyzed. These included disease-specific factors, patient-related factors, severity of illness, and procedural factors.

RESULTS

Of the 892 patients, 349 (39.1%) had an EN success rate of ≥70%, which was associated with a lower amount of prescribed enteral energy (500 kcal [500-800] vs. 800 kcal [500-1200], p < 0.001) and bolus administration of enteral nutrition (41 of 349 vs. 27 of 543, p < 0.001). Other factors impairing successful EN were severe inflammation, surgery, and GI-related admission diagnosis.

CONCLUSIONS

On the fourth day during ICU stay discrepancy between prescribed and administered enteral nutrition was associated to severe inflammation, GI-related diagnosis, and prescribing policy.

Standardized nutritional supply versus individual nutritional assessment: Impact on weight changes, complications and functional outcome from neurological early rehabilitation

BACKGROUND & AIMS

Approximately 55% of neurological and neurosurgical early rehabilitation (NNER) patients are in need of enteral nutrition, but long-term nutritional assessment of these critically ill patients is suboptimal. Therefore, this study analyzed the effect of an individual nutritional assessment on weight changes during rehabilitation and impact on complications and functional outcome.

METHODS

170 NNER patients on enteral nutrition were enrolled in the study. According to the initial ward, patients were assigned to receive standardized enteral nutrition (n = 107, control group) or an individual nutritional assessment (n = 63, intervention group). Weight changes, complications, assessment of the functional outcome (Early Rehabilitation Index, Barthel Index, Early Rehabilitation Barthel Index) and the length of stay were recorded and compared between groups using non-parametric tests for non-paired samples (Mann-Whitney U test for metric data or the χ² test for categorical data) or paired samples (Wilcoxon test). In addition, daily energy requirement was calculated and compared with daily intake. Correlation analysis by Spearman was performed to investigate linear relationship between weight changes and the difference of administered and calculated calories in both study groups.

RESULTS

A weight loss was observed in the control group, whereas the weight of the intervention group remained stable over time. The difference between calculated and administered calories correlated with weight changes in the control group. Regarding complications during rehabilitation, control patients showed more frequently impaired diuresis. In addition, control patients were suffering longer from diarrhea than patients of the intervention group. Both groups improved in functional status to a comparable degree. Relationships between these improvements and weight changes or administered calories could not be found.

CONCLUSIONS

Individual nutritional assessment had not an additional affect for the improvement of functional outcome or the prevention of complications. However, weight turned out to be more stable and signs of nutritional incompatibilities are less frequent among patients being treated with an individualized nutritional assessment.

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.