Validation of carbon dioxide production (VCO2) as a tool to calculate resting energy expenditure (REE) in mechanically ventilated critically ill patients: a retrospective observational study

Effects of positive end-expiratory pressure on brain oxygenation, systemic oxygen cascade and metabolism in acute brain injured patients: a pilot physiological cross-sectional study

Patients with acute brain injury (ABI) often require the application of positive end-expiratory pressure (PEEP) to optimize mechanical ventilation and systemic oxygenation. However, the effect of PEEP on cerebral function and metabolism is unclear. The primary aim of this study was to evaluate the effects of PEEP augmentation test (from 5 to 15 cmH2O) on brain oxygenation, systemic oxygen cascade and metabolism in ABI patients. Secondary aims include to determine whether changes in regional cerebral oxygenation are reflected by changes in oxygenation cascade and metabolism, and to assess the correlation between brain oxygenation and mechanical ventilation settings. Single center, pilot cross-sectional observational study in an Academic Hospital. Inclusion criteria were: adult (> 18 y/o) patients with ABI and stable intracranial pressure, available gas exchange and indirect calorimetry (IC) monitoring. Cerebral oxygenation was monitored with near-infrared spectroscopy (NIRS) and different derived parameters were collected: variation (Δ) in oxy (O2)-hemoglobin (Hb) (ΔO2Hbi), deoxy-Hb(ΔHHbi), total-Hb(ΔcHbi), and total regional oxygenation (ΔrSO2). Oxygen cascade and metabolism were monitored with arterial/venous blood gas analysis [arterial partial pressure of oxygen (PaO2), arterial saturation of oxygen (SaO2), oxygen delivery (DO2), and lactate], and IC [energy expenditure (REE), respiratory quotient (RQ), oxygen consumption (VO2), and carbon dioxide production (VCO2)]. Data were measured at PEEP 5 cmH2O and 15 cmH2O and expressed as delta (Δ) values. Ten patients with ABI [median age 70 (IQR 62-75) years, 6 (60%) were male, median Glasgow Coma Scale at ICU admission 5.5 (IQR 3-8)] were included. PEEP augmentation from 5 to 15 cmH2O did not affect cerebral oxygenation, systemic oxygen cascade parameters, and metabolism. The arterial component of cerebral oxygenation was significantly correlated with DO2 (ΔO2HBi, rho = 0.717, p = 0.037). ΔrSO2 (rho = 0.727, p = 0.032), ΔcHbi (rho = 0.797, p = 0.013), and ΔHHBi (rho = 0.816, p = 0.009) were significantly correlated with SaO2, but not ΔO2Hbi. ΔrSO2 was significantly correlated with VCO2 (rho = 0.681, p = 0.049). No correlation between brain oxygenation and ventilatory parameters was found. PEEP augmentation test did not affect cerebral and systemic oxygenation or metabolism. Changes in cerebral oxygenation significantly correlated with DO2, SaO2, and VCO2. Cerebral oxygen monitoring could be considered for individualization of mechanical ventilation setting in ABI patients without high or instable intracranial pressure.

Validity of Actigraph for Measuring Energy Expenditure in Healthy Adults: A Systematic Review and Meta-Analysis

PURPOSE

The objective of this systematic review and meta-analysis was to assess the validity of the Actigraph triaxial accelerometer device in measuring physical activity energy expenditure (PAEE) in healthy adults, with indirect calorimetry (IC) serving as the validity criterion.

METHODS

A comprehensive search was conducted using the PubMed, Web of Science, and sportdiscuss databases, in addition to manual searches for supplementary sources. Search strategies were employed that involved conducting single keyword searches using the terms "gt3x" and "Actigraph gt3x". The literature search encompassed the timeframe spanning from 1 January 2010 to 1 March 2023. The methodological quality of the studies included in the analysis was evaluated using both the Downs and Black checklist and the Consensus-Based Criteria for Selection of Measurement Instruments (COSMIN) checklist. The meta-analysis was conducted using the Review Manager 5.4 software. The standardized mean difference (SMD) was calculated and expressed as a 95% confidence interval (CI). The significance level was set at α = 0.05. A systematic assessment of the Actigraph's performance was conducted through the descriptive analysis of computed effect sizes.

RESULTS

A total of 4738 articles were retrieved from the initial search. After eliminating duplicate articles and excluding those deemed irrelevant, a comprehensive analysis was conducted on a total of 20 studies, encompassing a combined sample size of 1247 participants. The scores on the Downs and Black checklist ranged from 10 to 14, with a mean score of 11.35. The scores on the COSMIN checklist varied from 50% to 100%, with an average score of 65.83%. The meta-analysis findings revealed a small effect size (SMD = 0.01, 95% CI = 0.50-0.52, p = 0.97), indicating no statistically significant difference (p > 0.05).

CONCLUSIONS

The meta-analysis revealed a small effect size when comparing the Actigraph and IC, suggesting that the Actigraph can be utilized for assessing total PAEE. Descriptive analyses have indicated that the Actigraph device has limited validity in accurately measuring energy expenditure during specific physical activities, such as high-intensity and low-intensity activities. Therefore, caution should be exercised when utilizing this device for such purposes. Furthermore, there was a significant correlation between the activity counts measured by the Actigraph and the PAEE, indicating that activity counts can be utilized as a predictive variable for PAEE.

Controlled enteral nutrition in critical care patients - A randomized clinical trial of a novel management system

PURPOSE

Nutritional therapy is essential to ICU care. Successful early enteral feeding is hindered by lack of protocols, gastrointestinal intolerance and feeding interruptions, leading to impaired nutritional intake. smART+ was developed as a nutrition management feeding platform controlling tube positioning, reflux, gastric pressure, and malnutrition. This study evaluated the potential of this new ICU care platform to deliver targeted nutrition and improve ICU outcomes.

METHODS

Critically ill patients ≥18 years-old, mechanically ventilated and enterally fed, were randomized to receive ESPEN-guideline-based nutrition or smART+ -guided nutrition for 2-14 days. Primary endpoint was average deviation from daily targeted nutrition determined via calculation of energy targets per calorimetry. Secondary endpoints included gastric residual volumes, length of stay (LOS) and length of ventilation (LOV).

RESULTS

smART+ achieved a mean deviation from daily targeted nutrition of 10.5% (n = 48) versus 34.3% for control (n = 50), p < 0.0001. LOS and LOV were decreased in the smART+ group versus control (mean LOS: 10.4 days versus 13.7; reduction 3.3 days, adjusted HR 1.71, 95% CI:1.13,2.60, p = 0.012; mean LOV: 9.5 days versus 12.8 days reduction of 3.3 days, adjusted HR 1.64, 95% CI:1.08-2.51, p = 0.021). Feeding goals were met (within ±10%) on 75.7% of days for smART+ versus 23.3% for control (p < 0.001). No treatment-related adverse events occurred in either group. The study was stopped due to success in a planned interim analysis of the first 100 patients.

CONCLUSION

The smART+ Platform improved adherence to feeding goals and reduced LOS and LOV versus standard of care in critically ill patients.

TRIAL REGISTRATION

NCT04098224; registered September 23, 2019.

External Validation with Accuracy Confounders of VCO2-Derived Predicted Energy Expenditure Compared to Resting Energy Expenditure Measured by Indirect Calorimetry in Mechanically Ventilated Children

Optimal energy provision, guided by measured resting energy expenditure (REE) and determined by indirect calorimetry (IC), is fundamental in Intensive Care Units (ICU). Because IC availability is limited, methods to predict REE based on carbon dioxide production (VCO2) measurements (REEVCO2) alone have been proposed as a surrogate for REE measured by IC (REEIC). The study aimed at externally and internally validating the accuracy of the REEVCO2 as an alternative to REEIC in mechanically ventilated children. A ventilator’s integrated gas exchange module (E-COVX) was used to prospectively measure REEIC and predict REEVCO2 on 107 mechanically ventilated children during the first 24 h of admission. The accuracy of the REEVCO2 compared to REEIC was assessed through the calculation of bias and precision, paired median differences, linear regression, and ROC analysis. Accuracy within ±10% of the REEIC was deemed acceptable for the REEVCO2 equation. The calculated REEVCO2 based on respiratory quotient (RQ) 0.89 resulted in a mean bias of −72.7 kcal/day (95% limits of agreement −321.7 to 176.3 kcal/day) and a high coefficient of variation (174.7%), while 51.4% of the calculations fell outside the ±10% accuracy rate. REEVCO2 derived from RQ 0.80 or 0.85 did not improve accuracy. Only measured RQ (Beta 0.73, p < 0.001) and no-recorded neuromuscular blocking agents (Beta −0.13, p = 0.044) were independently associated with the REEVCO2−REEIC difference. Among the recorded anthropometric, metabolic, nutrition, or clinical variables, only measured RQ was a strong predictor of REEVCO2 inaccuracy (p < 0.001). Cutoffs of RQ = 0.80 predicted 89% of underestimated REEIC (sensitivity 0.99; specificity 0.89) and RQ = 0.82 predicted 56% of overestimated REEIC (sensitivity of 0.99; specificity 0.56). REEVCO2 cannot be recommended as an alternative to REEIC in mechanically ventilated children, regardless of the metabolic, anthropometric, or clinical status at the time of the evaluation.

Absent Metabolic Transition from the Early to the Late Period in Non-Survivors Post Cardiac Surgery

After major surgery, longitudinal changes in resting energy expenditure (REE) as well as imbalances in oxygen delivery (DO2) and distribution and processing (VO2) may occur due to dynamic metabolic requirements, an impaired macro- and microcirculatory flow and mitochondrial dysfunction. However, the longitudinal pattern of these parameters in critically ill patients who die during hospitalization remains unknown. Therefore, we analyzed in 566 patients who received a pulmonary artery catheter (PAC) their REE, DO2, VO2 and oxygen extraction ratio (O2ER) continuously in survivors and non-survivors over the first 7 days post cardiac surgery, calculated the percent increase in the measured compared with the calculated REE and investigated the impact of a reduced REE on 30-day, 1-year and 6-year mortality in a uni- and multivariate model. Only in survivors was there a statistically significant transition from a negative to a positive energy balance from day 0 until day 1 (Day 0: −3% (−18, 14) to day 1: 5% (−9, 21); p < 0.001). Furthermore, non-survivors had significantly decreased DO2 during the first 4 days and reduced O2ER from day 2 until day 6. Additionally, a lower REE was significantly associated with a worse survival at 30 days, 1 year and 6 years (p = 0.009, p < 0.0001 and p = 0.012, respectively). Non-survivors seemed to be unable to metabolically adapt from the early (previously called the ‘ebb’) phase to the later ‘flow’ phase. DO2 reduction was more pronounced during the first three days whereas O2ER was markedly lower during the following four days, suggesting a switch from a predominantly limited oxygen supply to prolonged mitochondrial dysfunction. The association between a reduced REE and mortality further emphasizes the importance of REE monitoring.

Nutrition Management for Critically Ill Adult Patients Requiring Non-Invasive Ventilation: A Scoping Review

Nutrition management is a core component of intensive care medicine. Despite the increased use of non-invasive ventilation (NIV) for the critically ill, a paucity of evidence on nutrition management precludes recommendations for clinical practice. A scope of the available literature is required to guide future research on this topic. Database searches of MEDLINE, Embase, Scopus, Web of Science, and Google Scholar were conducted to identify original research articles and available grey literature in English from 1 January 1990 to 17 November 2021 that included adult patients (≥16 years) receiving NIV within an Intensive Care Unit. Data were extracted on: study design, aim, population, nutrition concept, context (ICU type, NIV: use, duration, interface), and outcomes. Of 1730 articles, 16 met eligibility criteria. Articles primarily included single-centre, prospective, observational studies with only 3 randomised controlled trials. Key concepts included route of nutrition (n = 7), nutrition intake (n = 4), energy expenditure (n = 2), nutrition status (n = 1), and nutrition screening (n = 1); 1 unpublished thesis incorporated multiple concepts. Few randomised clinical trials that quantify aspects of nutrition management for critically ill patients requiring NIV have been conducted. Further studies, particularly those focusing on the impact of nutrition during NIV on clinical outcomes, are required to inform clinical practice.

A methodological and clinical approach to measured energy expenditure in the critically ill pediatric patient

The metabolic response to injury and stress is characterized initially by a decreased energy expenditure (Ebb phase) followed by an increased metabolic expenditure (Flow phase). Indirect calorimetry is a methodology utilized to measure energy expenditure and substrate utilization by measuring gas exchange in exhaled air and urinary nitrogen. The use of indirect calorimetry in critically ill patients requires precise equipment to obtain accurate measurements. The most recent guidelines suggested that measured energy expenditure by indirect calorimetry be used to determine energy requirements. This article reviews the methodological and clinical use of indirect calorimetry in critically ill pediatric patients.

Do we need different predictive equations for the acute and late phases of critical illness? A prospective observational study with repeated indirect calorimetry measurements

BACKGROUND

Predictive equations (PEs) for estimating resting energy expenditure (REE) that have been developed from acute phase data may not be applicable in the late phase and vice versa. This study aimed to assess whether separate PEs are needed for acute and late phases of critical illness and to develop and validate PE(s) based on the results of this assessment.

METHODS

Using indirect calorimetry, REE was measured at acute (≤5 days; n = 294) and late (≥6 days; n = 180) phases of intensive care unit admission. PEs were developed by multiple linear regression. A multi-fold cross-validation approach was used to validate the PEs. The best PEs were selected based on the highest coefficient of determination (R²), the lowest root mean square error (RMSE) and the lowest standard error of estimate (SEE). Two PEs developed from paired 168-patient data were compared with measured REE using mean absolute percentage difference.

RESULTS

Mean absolute percentage difference between predicted and measured REE was <20%, which is not clinically significant. Thus, a single PE was developed and validated from data of the larger sample size measured in the acute phase. The best PE for REE (kcal/day) was 891.6(Height) + 9.0(Weight) + 39.7(Minute Ventilation)-5.6(Age) - 354, with R² = 0.442, RMSE = 348.3, SEE = 325.6 and mean absolute percentage difference with measured REE was: 15.1 ± 14.2% [acute], 15.0 ± 13.1% [late].

CONCLUSIONS

Separate PEs for acute and late phases may not be necessary. Thus, we have developed and validated a PE from acute phase data and demonstrated that it can provide optimal estimates of REE for patients in both acute and late phases.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03319329.

Methods for Estimating Energy Expenditure in Critically Ill Adults

Energy expenditure (EE) is the sum of metabolic activity within the body at a given time and comprises basal EE, diet-induced thermogenesis, and physical activity. In the intensive care unit, EE is most often assessed to determine a patient's caloric requirements. Energy expenditure also may be useful to understand disease states and the metabolic impact of interventions. Several methods for estimating EE are relevant for clinical use, including indirect calorimetry, predictive equations, exhaled carbon dioxide volume, and the Fick method. Indirect calorimetry is the preferred method for evaluating EE and is considered the gold standard for estimating EE in hospitalized patients. However, use of indirect calorimetry is not always practical or possible. Therefore, other methods of estimating EE must be considered. In this review, methods of evaluating EE in critically ill adults are examined and the benefits and limitations of each method are discussed, with practical considerations for use.

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.

The centenary of the Harris-Benedict equations: How to assess energy requirements best? Recommendations from the ESPEN expert group

BACKGROUND & AIMS

The year 2019 marked the centenary of the publication of the Harris and Benedict equations for estimation of energy expenditure. In October 2019 a Scientific Symposium was organized by the European Society for Clinical Nutrition and Metabolism (ESPEN) in Vienna, Austria, to celebrate this historical landmark, looking at what is currently known about the estimation and measurement of energy expenditure.

METHODS

Current evidence was discussed during the symposium, including the scientific basis and clinical knowledge, and is summarized here to assist with the estimation and measurement of energy requirements that later translate into energy prescription.

RESULTS

In most clinical settings, the majority of predictive equations have low to moderate performance, with the best generally reaching an accuracy of no more than 70%, and often lead to large errors in estimating the true needs of patients. Generally speaking, the addition of body composition measurements did not add to the accuracy of predictive equations. Indirect calorimetry is the most reliable method to measure energy expenditure and guide energy prescription, but carries inherent limitations, greatly restricting its use in real life clinical practice.

CONCLUSIONS

While the limitations of predictive equations are clear, their use is still the mainstay in clinical practice. It is imperative to recognize specific patient populations for whom a specific equation should be preferred. When available, the use of indirect calorimetry is advised in a variety of clinical settings, aiming to avoid under-as well as overfeeding.

Using technology to assess nutritional status and optimize nutrition therapy in critically ill patients

PURPOSE OF REVIEW

Malnutrition is prevalent in critically ill patients and is linked to worse outcomes such as prolonged mechanical ventilation, length of intensive care unit (ICU) stay, and increased mortality. Therefore, nutritional therapy is important. However, it is often difficult to accurately identify those at high malnutrition risk and to optimize nutritional support. Different technological modalities have therefore been developed to identify patients at high nutritional risk and to guide nutritional support in an attempt to optimize outcomes.

RECENT FINDINGS

Computed tomography (CT), ultrasound (US), and bioelectrical impedance analysis are tools that allow assessment of lean body mass and detection of sarcopenia, which is a significant marker of poor nutrition. The use of indirect calorimetry allows the determination of resting energy expenditure to serve as a guide to providing optimal nutrition intake in ICU patients.

SUMMARY

By using CT, US, or bioelectrical impedance analysis, detection of sarcopenia can be undertaken in patients admitted to the ICU. This allows for an accurate picture of underlying nutritional status to help clinicians focus on nutritional support for these patients. Subsequently, indirect calorimetry can be used to guide optimal nutrition therapy and caloric intake in critically ill patients. However, whether these methods result in improved outcomes in critically ill patients remains to be validated.

Reliability of ActiGraph GT3X+ placement location in the estimation of energy expenditure during moderate and high-intensity physical activities in young and older adults

WHO defines physical activity (PA) as any bodily movement produced by skeletal muscles that requires energy expenditure (EE). The purpose of this study was to compare the EE estimations by ActiGraph GT3X+ with a gold standard measurement, the portable gas analyser in a set of 3 different PAs. This cross-sectional study involved 56 participants, age range (years, [min, max]: young people [20, 33], older adults [65, 83]). Participants completed a single session of three experimental PAs including biking, treadmill walking, and treadmill running. Each participant wore five GT3X+ triaxial accelerometers and a portable gas analyser used as the gold standard measurement. The GT3X+ were placed on the wrists, the waist (centred at the pelvis), and the ankles. ActiGraph GT3X+ and MetaMax3B records were investigated through intraclass correlation coefficient. Magnitude of measurement error was estimated using Effect Size. The GT3X+ wrist and GT3X+ waist underestimated EE regardless of the PA type. The GT3X+ ankles strongly overestimated EE during biking (mean bias = 489 ± 392%) and walking (mean bias = 106 ± 58%), while it underestimated EE during running (mean bias = -47 ± 27%). The ActiGraph GT3X+ does not provide accurate EE estimates across a range of placement locations during moderate and high-intensity PA.

First international meeting of early career investigators: Current opportunities, challenges and horizon in critical care nutrition research

BACKGROUND

Appropriate nutritional support is a key component of care for critically ill patients. While malnutrition increases complications, impacting long term outcomes and healthcare-related costs, uncertainties persist regarding optimal provision of nutritional support in this setting.

METHODS

An international group of healthcare providers (HCPs) from critical care specialties and nutrition researchers convened to identify knowledge gaps and learnings from studies in critical care nutrition. Clinical research needs were identified in order to better inform future nutrition practices.

RESULTS

Challenges in critical care nutrition arise, in part, from inconsistent outcomes in several large-scale studies regarding the optimal amount of calories and protein to prescribe, the optimal time to initiate nutritional support and the role of parental nutrition to support critically ill patients. Furthermore, there is uncertainty on how best to identify patients at nutritional risk, and the appropriate outcome measures for ICU nutrition studies. Given HCPs have a suboptimal evidence base to inform the nutritional management of critically ill patients, further well-designed clinical trials capturing clinically relevant endpoints are needed to address these knowledge gaps.

CONCLUSIONS

The identified aspects for future research could be addressed in studies designed and conducted in collaboration with an international team of interdisciplinary nutrition experts. The aim of this collaboration is to address the unmet need for robust clinical data needed to develop high-quality evidence-based nutritional intervention recommendations to better inform the future management of critically ill patients.

Advances in Medical Nutrition Therapy: Parenteral Nutrition

Parenteral nutrition has evolved tremendously, with parenteral formulas now safer and more accessible than ever. "All-in-one" admixtures are now available, which simplify parenteral nutrition usage and decrease line infection rates alongside other methods of infectious control. Recently published data on the benefits of parenteral nutrition versus enteral nutrition together with the widespread use of indirect calorimetry solve many safety issues that have emerged over the years. All these advances, alongside a better understanding of glycemic control and lipid and protein formulation improvements, make parenteral nutrition a safe alternative to enteral nutrition.

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.

The effect of cisatracurium infusion on the energy expenditure of critically ill patients: an observational cohort study

Background

Both overfeeding and underfeeding of intensive care unit (ICU) patients are associated with worse outcomes. A reliable estimation of the energy expenditure (EE) of ICU patients may help to avoid these phenomena. Several factors that influence EE have been studied previously. However, the effect of neuromuscular blocking agents on EE, which conceptually would lower EE, has not been extensively investigated.

Methods

We studied a cohort of adult critically ill patients requiring invasive mechanical ventilation and treatment with continuous infusion of cisatracurium for at least 12 h. The study aimed to quantify the effect of cisatracurium infusion on EE (primary endpoint). EE was estimated based on ventilator-derived VCO₂ (EE in kcal/day = VCO₂ × 8.19). A subgroup analysis of septic and non-septic patients was performed. Furthermore, the effects of body temperature and sepsis on EE were evaluated. A secondary endpoint was hypercaloric feeding (> 110% of EE) after cisatracurium infusion.

Results

In total, 122 patients were included. Mean EE before cisatracurium infusion was 1974 kcal/day and 1888 kcal/day after cisatracurium infusion. Multivariable analysis showed a significantly lower EE after cisatracurium infusion (MD − 132.0 kcal (95% CI − 212.0 to − 52.0; p = 0.001) in all patients. This difference was statistically significant in both sepsis and non-sepsis patients (p = 0.036 and p = 0.011). Non-sepsis patients had lower EE than sepsis patients (MD − 120.6 kcal; 95% CI − 200.5 to − 40.8, p = 0.003). Body temperature and EE were positively correlated (Spearman’s rho = 0.486, p < 0.001). Hypercaloric feeding was observed in 7 patients.

Conclusions

Our data suggest that continuous infusion of cisatracurium in mechanically ventilated ICU patients is associated with a significant reduction in EE, although the magnitude of the effect is small. Sepsis and higher body temperature are associated with increased EE. Cisatracurium infusion is associated with overfeeding in only a minority of patients and therefore, in most patients, no reductions in caloric prescription are necessary.

Medical Nutrition Therapy in Critically Ill Patients Treated on Intensive and Intermediate Care Units: A Literature Review

Medical nutrition therapy in critically ill patients remains challenging, not only because of the pronounced stress response with a higher risk for complications, but also due to their heterogeneity evolving from different phases of illness. The present review aims to address current knowledge and guidelines in order to summarize how they can be best implemented into daily clinical practice. Further studies are urgently needed to answer such important questions as best timing, route, dose, and composition of medical nutrition therapy for critically ill patients and to determine how to assess and to adapt to patients’ individual needs.

Indirect Calorimetry in Clinical Practice

Indirect calorimetry (IC) is considered as the gold standard to determine energy expenditure, by measuring pulmonary gas exchanges. It is a non-invasive technique that allows clinicians to personalize the prescription of nutrition support to the metabolic needs and promote a better clinical outcome. Recent technical developments allow accurate and easy IC measurements in spontaneously breathing patients as well as in those on mechanical ventilation. The implementation of IC in clinical routine should be promoted in order to optimize the cost–benefit balance of nutrition therapy. This review aims at summarizing the latest innovations of IC as well as the clinical indications, benefits, and limitations.

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.