Determining energy requirements in the ICU

Bioelectrical Impedance Analysis to Assess Energy Expenditure in Critically Ill Patients: A Cross-Sectional Study

BACKGROUND

Evaluating energy expenditure is important for establishing optimal goals for nutrition treatment. However, indirect calorimetry, the reference standard for measuring energy expenditure, is difficult to apply widely in clinical practice.

OBJECTIVE

To test the consistency of bioelectrical impedance analysis (BIA) relative to indirect calorimetry for evaluating energy expenditure in critically ill patients.

METHODS

A cross-sectional study of 140 critically ill adult patients was conducted. Within 24 hours of a patient being transferred to the intensive care unit, trained researchers assessed the patient's energy expenditure by use of BIA and indirect calorimetry simultaneously. Consistency of the 2 measurements was detected by intraclass correlation coefficients with a 2-way random-effects model. Factors affecting consistency were analyzed.

RESULTS

Median energy expenditure measured by indirect calorimetry was 1430.0 kcal/d (IQR, 1190.5-1650.8 kcal/d). Median energy expenditure measured by BIA was 1407.0 kcal/d (IQR, 1248.5-1563.5 kcal/d). The correlation coefficient between indirect calorimetry and BIA was 0.813 (95% CI, 0.748-0.862; P < .001). The consistency of the 2 measurements was lower in patients with comorbidities than in those without (P = .004).

CONCLUSIONS

Results of BIA were highly consistent with indirect calorimetry assessments of energy expenditure in critically ill patients. Few factors except comorbidity affect the accuracy of BIA when assessing energy expenditure. Therefore, as a low-cost, easy-to-use, and noninvasive method, BIA is a valuable clinical tool for assessing energy expenditure in critically ill patients.

Validation of Indirect Calorimetry in Children Undergoing Single-Limb Non-Invasive Ventilation: A Proof of Concept, Cross-Over Study

BACKGROUND

The accurate assessment of resting energy expenditure (REE) is essential for personalized nutrition, particularly in critically ill children. Indirect calorimetry (IC) is the gold standard for measuring REE. This methodology is based on the measurement of oxygen consumption (VO2) and carbon dioxide production (VCO2). These parameters are integrated into the Weir equation to calculate REE. Additionally, IC facilitates the determination of the respiratory quotient (RQ), offering valuable insights into a patient's carbohydrate and lipid consumption. IC validation is limited to spontaneously breathing and mechanically ventilated patients, but it is not validated in patients undergoing non-invasive ventilation (NIV). This study investigates the application of IC during NIV-CPAP (continuous positive airway pressure) and NIV-PS (pressure support).

METHODS

This study was conducted in the Pediatric Intensive Care Unit of IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, between 2019 and 2021. Children < 6 years weaning from NIV were enrolled. IC was performed during spontaneous breathing (SB), NIV-CPAP, and NIV-PS in each patient. A Bland-Altman analysis was employed to compare REE, VO2, VCO2, and RQ measured by IC.

RESULTS

Fourteen patients (median age 7 (4; 18) months, median weight 7.7 (5.5; 9.7) kg) were enrolled. The REE, VO2, VCO2, and RQ did not differ significantly between the groups. The Limits of Agreement (LoA) and bias of REE indicated good agreement between SB and NIV-CPAP (LoA +28.2, -19.4 kcal/kg/day; bias +4.4 kcal/kg/day), and between SB and NIV-PS (LoA -22.2, +23.1 kcal/kg/day; bias 0.4 kcal/kg/day).

CONCLUSIONS

These preliminary findings support the accuracy of IC in children undergoing NIV. Further validation in a larger cohort is warranted.

OXYGEN CONSUMPTION AS AN EARLY WARNING SYSTEM IN THE CRITICALLY ILL

ABSTRACT

Introduction: In this study, we assessed whether changes in oxygen consumption (VO 2 ) and other metabolic parameters could be used as an early warning system for detecting clinical deterioration in mechanically ventilated patients. Methods: This was a prospective cohort study of adult patients requiring mechanical ventilation between February 2016 and March 2019. We looked for changes in VO 2 , carbon dioxide production (VCO 2 ), respiratory quotient (RQ), and end-tidal carbon dioxide (EtCO 2 ), occurring prior to clinical deterioration. Clinical deterioration was predefined as a requirement of vasopressor, an increase in serum lactate by 20% where at least one value was above 3 mmol/L, or a decrease in hemoglobin by 20% in the 4 hours prior to clinical deterioration. Results A total of 141 patients were included. There were no detectable changes in VO 2 , VCO 2 , and EtCO 2 within the 4 hours prior to any clinical deterioration. RQ increased significantly within the 4 hours prior to an increase in lactate as compared with no increase in lactate, but there were no detectable changes prior to other clinical deteriorations. Conclusions RQ has the potential to be an early marker of tissue hypoperfusion or mitochondrial dysfunction. However, future studies are necessary to evaluate the use of RQ as a bedside monitor in critical care settings.

The Role of Indirect Calorimetry in Care of the Surgical Patient

Purpose of Review

This is a review of recent literature on the role of indirect calorimetry in surgical nutrition.

Recent Findings

All critical care societal guidelines recommend the use of indirect calorimetry as the standard of care to determine energy needs. Recent studies confirm discrepancy between measured and equation-predicted energy expenditure and further demonstrate improved outcomes with indirect calorimetry-guided nutrition. Patients that undergo ECMO, CRRT and those with COVID-19 would benefit from the use of indirect calorimetry.

Summary

Indirect calorimetry-guided nutrition is the standard of care in mechanically ventilated surgical patients.

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.

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.

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.

Overcoming challenges to enteral nutrition delivery in critical care

PURPOSE OF REVIEW

Existing data and all ICU nutrition guidelines emphasize enteral nutrition (EN) represents a primary therapy leading to both nutritional and non-nutritional benefits. Unfortunately, iatrogenic malnutrition and underfeeding is virtually ubiquitous in ICUs worldwide for prolonged periods post-ICU admission. Overcoming essential challenges to EN delivery requires addressing a range of real, and frequently propagated myths regarding EN delivery.

RECENT FINDINGS

Key recent data addresses perceived challenges to EN including: Adequately resuscitated patients on vasopressors can and likely should receive trophic early EN and this was recently associated with reduced mortality; Patients paralyzed with neuromuscular blocking agents can and should receive early EN as this was recently associated with reduced mortality/hospital length of stay; Proned patients can safely receive EN; All ICU nutrition delivery, including EN, should be objectively guided by indirect calorimetry (IC) measures. This is now possible with the new availability of a next-generation IC device.

SUMMARY

It is the essential implementation of this new evidence occurs to overcome real and perceived EN challenges. This data should lead to increased standardization/protocolization of ICU nutrition therapy to ensure personalized nutrition care delivering the right nutrition dose, in the right patient, at the right time to optimize clinical outcome.

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.

The Systemic Metabolic Profile Early after Allogeneic Stem Cell Transplantation: Effects of Adequate Energy Support Administered through Enteral Feeding Tube

Patients undergoing allogeneic stem cell transplantation usually require nutritional support. There is no consensus on whether enteral support through tube feeding should be preferred. A recent randomized study could not detect any difference between enteral and parenteral feeding with regard to post-transplant outcomes, whereas 2 retrospective studies described an association between enteral feeding and a favorable post-transplant outcome. We compared pre- and post-transplant plasma metabolomic profiles for 10 patients receiving mainly enteral nutritional support and 10 patients receiving mainly parenteral support. Samples were collected before conditioning and 3 weeks post-transplant; 824 metabolites were analyzed using mass spectrometry. The pretransplant metabolite profiles showed a significant overlap between the 2 groups. Post-transplant samples for both patient groups showed an increase of secondary bile acids and endocannabinoids, whereas reduced levels were seen for food preservatives, plasmalogens, and retinol metabolites. The main post-transplant differences between the groups were decreased levels of fatty acids and markers of mitochondrial activation in the control group, indicating that these patients had insufficient energy intake. A significant effect was also seen for heme/bilirubin metabolism for the parenteral support. To conclude, allotransplant recipients showed altered metabolic profiles early after transplantation; this was mainly due to the conditioning/transplantation/reconstitution, whereas the type of nutritional support had minor effects.

Evaluation of the accuracy and precision of a new generation indirect calorimeter in canopy dilution mode

BACKGROUND & AIMS

Indirect calorimetry (IC) is the only way to measure in real time energy expenditure (EE) and to optimize nutrition support in acutely and chronically ill patients. Unfortunately, most of the commercially available indirect calorimeters are rather complex to use, expensive and poorly accurate and precise. Therefore, an innovative device (Q-NRG®, COSMED, Rome, Italy) that matches clinicians' needs has been developed as part of the multicenter ICALIC study supported by the two academic societies ESPEN and ESICM. The aim of this study was to evaluate the accuracy and intra- and inter-unit precision of this new device in canopy dilution mode in vitro and in spontaneously breathing adults.

METHODS

Accuracy and precision of oxygen consumption (VO₂) and carbon dioxide production (VCO₂) measurements were evaluated in vitro and in 15 spontaneously breathing healthy adults by interchanging three Q-NRG® units in a random order. In vitro validation was performed by gas exchange simulation using high-precision gas mixture and mass flow controller. Accuracy was calculated as error of measured values against expected ones based on volume of gas infused. Respiratory coefficient (RQ) accuracy was furthermore assessed using the ethanol-burning test. To evaluate the intra- and inter-unit precisions, the coefficient of variation (CV% = SD/Mean*100) was calculated, respectively, from the mean ± SD or the mean ± SD of the three mean values of VO₂, VCO₂, RQ and EE measured by each Q-NRG® units. In vivo accuracy measurement of the Q-NRG® was assessed by simultaneous comparison with mass spectrometry (MS) gas analysis, using Bland-Altman plot, Pearson correlation and paired t-test (significance level of p = 0.05).

RESULTS

In vitro evaluation of the Q-NRG® accuracy showed measurement errors <1% for VO₂, VCO₂ and EE and <1.5% for RQ. Evaluation of the intra- and inter-unit precision showed CV% ≤1% for VO₂ and EE and CV% ≤1.5% for VCO₂ and RQ measurements, except for one Q-NRG® unit where CV% was 2.3% for VO₂ and 3% for RQ. Very good inter-unit precision was confirmed in vivo with CV% equal to 2.4%, 3%, 2.8% and 2.3% for VO₂, VCCO₂, RQ and EE, respectively. Comparison with MS showed correlation of 0.997, 0.987, 0.913 and 0.997 for VO₂, VCO₂, RQ and EE respectively (p ≤ 0.05). Mean deviation of paired differences was 1.6 ± 1.4% for VO₂, -1.5 ± 2.5% for VCO₂, -3.1 ± 2.6% for RQ and 0.9 ± 1.4% for EE.

CONCLUSION

Both in vitro and in vivo measurements of VO₂, VCO₂, RQ and EE on three Q-NRG® units showed minimal differences compared to expected values and MS and very low intra- and inter-unit variability. These results confirm the very good accuracy and precision of the Q-NRG® indirect calorimeter in canopy dilution mode in spontaneously breathing adults.

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

BACKGROUND

Adequate nutrition therapy in critically ill patients poses a challenge because of the variable energy and substrate needs. The objective was to investigate whether nutrition therapy involving indirect calorimetry (IC), instead of equations for assessment of energy needs, could improve the nutrition status of critically ill patients.

METHODS

Forty mechanically ventilated patients were randomized into a group in which energy needs were controlled by calorimetry (IC group) and a group treated with a formula-based approach reflecting standard care (SC group). The primary outcome was change in the phase angle (PhA), a bioelectrical impedance parameter related to nutrition status and prognosis.

RESULTS

The mean IC-based energy requirement was lower than the formula-based estimate (21.1 ± 6.4 versus [vs] 25 kcal/kg/d, P < .01). The IC group reached 98% ± 8% of the energy goal, whereas the SC group reached only 79% ± 29% (P < 0.05), although mean intake was similar in both groups. The protein intake goal was better met in the IC group (91% ± 24%) than the SC group (73% ± 33%). The PhA of the IC group did not change during treatment, whereas that of the SC group tended to decrease by 0.36° ± 0.86° (P = .077). A shorter length of stay in intensive care was observed in the IC than in the SC group (13 ± 8 vs 24 ± 20 days, P < .05).

CONCLUSION

Intensified individual nutrition therapy involving IC appears to be useful for improving nutrition status in critically ill patients.

Predictive equations versus measured energy expenditure by indirect calorimetry: A retrospective validation

BACKGROUND & AIMS

Measuring resting energy expenditure (REE) via indirect calorimetry (IC) in intensive care unit (ICU) patient is the gold standard recommended by guidelines. However technical difficulties hinder its use and predictive equations are largely used instead. We sought to validate commonly used equations using a large cohort of patients.

METHODS

Patients hospitalized from 2003 to 2015 in a 16-bed ICU at a university-affiliated, tertiary care hospital who had IC measurement to assess caloric targets were included. Data was drawn from a computerized system and included REE and other variables required by equations. Measurements were restricted to 5 REE per patient to avoid bias. Equation performance was assessed by comparing means, standard deviations, correlation, concordance and agreement, which was defined as a measurement within 85-115% of measured REE. A total of 8 equations were examined.

RESULTS

A total of 3573 REE measurements in 1440 patients were included. Mean patient age was 58 years and 65% were male. A total of 562 (39%) patients had >2 REE measurements. Standard deviation of REE ranged from 430 to 570 kcal. The Faisy equation had the least mean difference (90 Kcal); Harris-Benedict had the highest correlation (52%) and agreement (50%) and Jolliet the highest concordance (62%). Agreement within 10% of caloric needs was met only in a third of patients.

CONCLUSIONS

Predictive equations have low performance when compared to REE in ICU patients. We therefore suggest that predictive equations cannot wholly replace indirect calorimetry for the accurate estimation of REE in this population.

Parenteral or enteral nutrition: do you have the choice?

PURPOSE OF REVIEW

The review focuses on the use of parenteral nutrition and enteral nutrition in critically ill patients to optimize the nutrition care throughout the ICU stay. The key message is: you have the choice!

RECENT FINDINGS

Enteral nutrition has been recommended for critically ill patients, whereas parenteral nutrition has been considered harmful and to be avoided. However, recent studies have challenged this theory. They demonstrated that enteral nutrition is frequently associated with energy and protein undernutrition, whereas parenteral nutrition becomes deleterious only if overfeeding is induced. Measuring energy expenditure by indirect calorimetry, in most cases, enables accurate determination of the energy needs to optimize the prescription of nutrition. Protein targets should also be considered for adequate feeding. Parenteral nutrition can be used as a supplement or as an alternative to enteral nutrition in case of gastrointestinal intolerance, to enable adequate energy, and protein provision.

SUMMARY

Parenteral nutrition is a powerful tool to optimize nutrition care of critically ill patients to improve clinical outcome, if prescribed according to the individual needs of the patients. After 3-4 days of attempt to feed enterally, enteral nutrition or parenteral nutrition can be used alternatively or combined, as long as the target is reached with special attention to avoid hypercaloric feeding.

Parenteral nutrition in intensive care patients: medicoeconomic aspects

PURPOSE OF REVIEW

Parenteral nutrition (PN) alone or as supplemental parenteral nutrition (SPN) has been shown to prevent negative cumulative energy balance, to improve protein delivery and, in some studies, to reduce infectious morbidity in ICU patients who fail to cover their needs with enteral nutrition (EN) alone.

RECENT FINDINGS

The optimization of energy provision to an individualized energy target using either early PN or SPN within 3-4 days after admission has recently been reported to be a cost-saving strategy mediated by a reduction of infectious complications in selected intensive care patients.

SUMMARY

EN alone is often insufficient, or occasionally contraindicated, in critically ill patients and results in growing energy and protein deficit. The cost benefit of using early PN in patients with short-term relative contraindications to EN has been reported. In selected patients SPN has been associated with a decreased risk of infection, a reduced duration of mechanical ventilation, a shorter stay in the ICU. Altogether four studies have investigated the costs associated with these interventions since 2012: two of them from Australia and Switzerland have shown that optimization of energy provision using SPN results in cost reduction, conflicting with other studies. The latter encouraging findings require further validation.

Alterations in energy substrate metabolism in mice with different degrees of sepsis

BACKGROUND

Nutritional management is crucial during the acute phase of severe illnesses. However, the appropriate nutritional requirements for patients with sepsis are poorly understood. We investigated alterations in carbohydrate, fat, and protein metabolism in mice with different degrees of sepsis.

MATERIALS AND METHODS

C57BL/6 mice were divided into three groups: control mice group, administered with saline, and low- and high-dose lipopolysaccharide (LPS) groups, intraperitoneally administered with 1 and 5 mg of LPS/kg, respectively. Rectal temperature, food intake, body weight, and spontaneous motor activity were measured. Indirect calorimetry was performed using a respiratory gas analysis for 120 h, after which carbohydrate oxidation and fatty acid oxidation were calculated. Urinary nitrogen excretion was measured to evaluate protein metabolism. The substrate utilization ratio was recalculated. Plasma and liver carbohydrate and lipid levels were evaluated at 24, 72, and 120 h after LPS administration.

RESULTS

Biological reactions decreased significantly in the low- and high-LPS groups. Fatty acid oxidation and protein oxidation increased significantly 24 h after LPS administration, whereas carbohydrate oxidation decreased significantly. Energy substrate metabolism changed from glucose to predominantly lipid metabolism depending on the degree of sepsis, and protein metabolism was low. Plasma lipid levels decreased, whereas liver lipid levels increased at 24 h, suggesting that lipids were transported to the liver as the energy source.

CONCLUSIONS

Our findings revealed that energy substrate metabolism changed depending on the degree of sepsis. Therefore, in nutritional management, such metabolic alterations must be considered, and further studies on the optimum nutritional intervention during severe sepsis are necessary.

Practice Guidelines for Nutrition in Critically Ill Patients: A Relook for Indian Scenario

Background and Aim:

Intensive-care practices and settings may differ for India in comparison to other countries. While international guidelines are available to direct the use of enteral nutrition (EN), there are no recommendations specific to Indian settings. Advisory board meetings were arranged to develop the practice guidelines specific to Indian context, for the use of EN in critically ill patients and to overcome challenges in this field.

Methods:

Various existing guidelines, meta-analyses, randomized controlled trials, controlled trials, and review articles were reviewed for their contextual relevance and strength. A systematic grading of practice guidelines by advisory board was done based on strength of the supporting evidence. Wherever Indian studies were not available, references were taken from the international guidelines.

Results:

Based on the literature review, the recommendations for developing the practice guidelines were made as per the grading criteria agreed upon by the advisory board. The recommendations were to address challenges regarding EN versus parenteral nutrition; nutrition screening and assessment; nutrition in hemodynamically unstable; route of nutrition; tube feeding and challenges; tolerance; optimum calorie-protein requirements; selection of appropriate enteral feeding formula; micronutrients and immune-nutrients; standard nutrition in hepatic, renal, and respiratory diseases and documentation of nutrition practices.

Conclusion:

This paper summarizes the optimum nutrition practices for critically ill patients. The possible solutions to overcome the challenges in this field are presented as practice guidelines at the end of each section. These guidelines are expected to provide guidance in critical care settings regarding appropriate critical-care nutrition practices and to set up Intensive Care Unit nutrition protocols.

Estimating Resting Energy Expenditure by Different Methods as Compared With Indirect Calorimetry for Patients With Pulmonary Hypertension

BACKGROUND

For patients with pulmonary hypertension, nutrition status is an independent predictor of morbidity and mortality, and energy expenditure can be strongly influenced by lung disease. Indirect calorimetry (IC) is the gold standard for measuring resting energy expenditure (REE), this study aimed to compare the results of REE estimated by different methods with those obtained by IC for patients with pulmonary hypertension.

METHODS

In this cross-sectional study (n = 34), REE was estimated by bioelectrical impedance analysis and the predictive equations of Harris-Benedict, Food and Agriculture Organization / World Health Organization, Institute of Medicine, Cunningham, Katch-McArdle, and Mifflin-St Jeor.

RESULTS

Mean patient age was 47.0 ± 14.5 years, and 76.5% were women. REE obtained with IC was strongly correlated with all other estimation methods but showed higher mean values: IC 1750.8 ± 434.3 kcal vs bioelectrical impedance analysis, 1549.0 ± 417.8 kcal; Harris-Benedict, 1493.1 ± 337.0 kcal; FAO/WHO, 1536.1 ± 345.0 kcal; Institute of Medicine, 1457.1 ± 293.2 kcal; Cunningham, 1597.3 ± 292.3 kcal; Katch-McArdle, 1447.7 ± 287.0 kcal; and Mifflin-St Jeor, 1388.7 ± 303.9 kcal. The analysis of agreement showed a clinically significant bias of approximately -255 kcal in all estimation methods when compared with IC.

CONCLUSION

Although there was a strong correlation between REE estimation methods and IC, there was no agreement between them. All estimation methods underestimated energy needs by about 255 kcal for patients with pulmonary hypertension, and the Cunningham equation had the smallest difference in relation to IC.

Which indicators for measuring the daily physical activity? An overview on the challenges and technology limits for Telehealth applications

BACKGROUND

Obesity is one of the biggest drivers of preventable chronic diseases and healthcare costs in Worldwide. Different prevention activities are suggested. By monitoring daily energy expenditure (EE) could be possible make personalized diets and programming physical activity. In this, physical inactivity is one of the most important public health problems. Some studies refer the effort of the international community in promoting physical activities. Physical activity can be promoted only by increasing citizens' empowerment on taking care of their health, and it passes from the improving of individual information. Technology can offer solutions and metrics for monitoring and measuring daily activity by interacting with individuals, sharing information and feedbacks.

OBJECTIVE

In this study we review indicators of total energy expenditure and weaknesses of available devices in assessing these parameters.

METHODS

Literature review and technology testing EuNetHta core model.

RESULTS

For the clinical aspects, it is fundamental to take into account all the factor that can influence the personal energy expenditure as: heart rate, blood pressure and thermoregulation (influenced by the body temperature).

DISCUSSION

In this study we focused the attention on the importance of tools to encourage the physical activity. We made an analysis of the factor that can influence the right analysis of energy expenditure and at the same time the energy regime. A punctual monitoring of the exercise regime could be helpful in Telemedicine application as Telemonitorig. More study are needed to value the impact of physical activity tracker in Telemonitorig protocols.

CONCLUSION

On the assessment of the energy expenditure, critical issues are related to the physiological data acquisition. Sensors connected with mobile devices could be important tools for disease prevention and interventions affecting health behaviors. New devices applications are potential useful for telemedicine assistance, but security of data and the related communication protocol limits should be taking into account.

Can calculation of energy expenditure based on CO2 measurements replace indirect calorimetry?

BACKGROUND

Methods to calculate energy expenditure (EE) based on CO₂ measurements (EEVCO₂) have been proposed as a surrogate to indirect calorimetry. This study aimed at evaluating whether EEVCO₂ could be considered as an alternative to EE measured by indirect calorimetry.

METHODS

Indirect calorimetry measurements conducted for clinical purposes on 278 mechanically ventilated ICU patients were retrospectively analyzed. EEVCO₂ was calculated by a converted Weir's equation using CO₂ consumption (VCO₂) measured by indirect calorimetry and assumed respiratory quotients (RQ): 0.85 (EEVCO₂_0.85) and food quotient (FQ; EEVCO₂_FQ). Mean calculated EEVCO₂ and measured EE were compared by paired t test. Accuracy of EEVCO₂ was evaluated according to the clinically relevant standard of 5% accuracy rate to the measured EE, and the more general standard of 10% accuracy rate. The effects of the timing of measurement (before or after the 7th ICU day) and energy provision rates (<90 or ≥90% of EE) on 5% accuracy rates were also analyzed (chi-square tests).

RESULTS

Mean biases for EEVCO₂_0.85 and EEVCO₂_FQ were -21 and -48 kcal/d (p = 0.04 and 0.00, respectively), and 10% accuracy rates were 77.7 and 77.3%, respectively. However, 5% accuracy rates were 46.0 and 46.4%, respectively. Accuracy rates were not affected by the timing of the measurement, or the energy provision rates at the time of measurements.

CONCLUSIONS

Calculated EE based on CO₂ measurement was not sufficiently accurate to consider the results as an alternative to measured EE by indirect calorimetry. Therefore, EE measured by indirect calorimetry remains as the gold standard to guide nutrition therapy.

Indirect calorimetry in nutritional therapy. A position paper by the ICALIC study group

BACKGROUND & AIMS

This review aims to clarify the use of indirect calorimetry (IC) in nutritional therapy for critically ill and other patient populations. It features a comprehensive overview of the technical concepts, the practical application and current developments of IC.

METHODS

Pubmed-referenced publications were analyzed to generate an overview about the basic knowledge of IC, to describe advantages and disadvantages of the current technology, to clarify technical issues and provide pragmatic solutions for clinical practice and metabolic research. The International Multicentric Study Group for Indirect Calorimetry (ICALIC) has generated this position paper.

RESULTS

IC can be performed in in- and out-patients, including those in the intensive care unit, to measure energy expenditure (EE). Optimal nutritional therapy, defined as energy prescription based on measured EE by IC has been associated with better clinical outcome. Equations based on simple anthropometric measurements to predict EE are inaccurate when applied to individual patients. An ongoing international academic initiative to develop a new indirect calorimeter aims at providing innovative and affordable technical solutions for many of the current limitations of IC.

CONCLUSION

Indirect calorimetry is a tool of paramount importance, necessary to optimize the nutrition therapy of patients with various pathologies and conditions. Recent technical developments allow broader use of IC for in- and out-patients.

Supplemental Parenteral Nutrition Is the Key to Prevent Energy Deficits in Critically Ill Patients

This review emphasizes the role of a timely supplemental parenteral nutrition (PN) for critically ill patients. It contradicts the recommendations of current guidelines to avoid the use of PN, as it is associated with risk. Critical illness results in severe metabolic stress. During the early phase, inflammatory cytokines and mediators induce catabolism to meet the increased body energy demands by endogenous sources. This response is not suppressed by exogenous energy administration, and the early use of PN to reach the energy target leads to overfeeding. On the other hand, early and progressive enteral nutrition (EN) is less likely to cause overfeeding because of variable gastrointestinal tolerance, a factor frequently associated with significant energy deficit. Recent studies demonstrate that adequate feeding is beneficial during and after the intensive care unit (ICU) stay. Supplemental PN allows for timely adequate feeding, if sufficient precautions are taken to avoid overfeeding. Indirect calorimetry can precisely define the adequate energy prescription. Our pragmatic approach is to start early EN to progressively test the gut tolerance and add supplemental PN on day 3 or 4 after ICU admission, only if EN does not meet the measured energy target. We believe that supplemental PN plays a pivotal role in the achievement of adequate feeding in critically ill patients with intolerance to EN and does not cause harm if overfeeding is avoided by careful prescription, ideally based on energy expenditure measured by indirect calorimetry.

Measuring energy expenditure in the intensive care unit: a comparison of indirect calorimetry by E-sCOVX and Quark RMR with Deltatrac II in mechanically ventilated critically ill patients

Background

Indirect calorimetry allows the determination of energy expenditure in critically ill patients by measuring oxygen consumption (VO₂) and carbon dioxide production (VCO₂). Recent studies have demonstrated variable performance of “breath-by-breath” instruments compared to mixing chamber technology. The aim of this study was to validate two modern devices (E-sCOVX and Quark RMR) against a reference method (Deltatrac II).

Method

Measurements of VO₂/VCO₂ with the test and reference devices were performed simultaneously over a 20-min period in mechanically ventilated adult intensive care unit patients. Accuracy and precision of instruments were analyzed using Bland-Altman plots.

Results

Forty-eight measurements in 22 patients were included for analysis. Both E-sCOVX and Quark RMR overestimated VO₂ and VCO₂ compared to Deltatrac II, corresponding to a 10 % higher mean resting energy expenditure. Limits of agreement of resting energy expenditure within ±2 standard deviations were ±461 kcal/24 h (±21 % expressed as percentage error) for ΔE-sCOVX–Deltatrac II and ±465 kcal/24 h (±22 %) for ΔQuark RMR–Deltatrac II.

Conclusion

Both test devices overestimate VO₂ and VCO₂ compared to Deltatrac II. The observed limits of agreement are comparable to those commonly accepted in evaluations of circulatory monitoring, and significantly less than results from predictive equations. We hypothesize that the discrepancy between methods is due to patient/ventilator-related factors that affect the synchronization of gas and spirometry waveforms.

Trial registration

Australian New Zealand Clinical Trials Registry, Trial ID ACTRN12615000205538. Date registered 3 March 2015.

Nutritional needs for the critically ill in relation to inflammation

PURPOSE OF REVIEW

This review focuses on nutritional needs in critically ill patients. The inflammation corresponding to acute stress is highlighted. Simultaneously, we try to avoid limiting the perspective to only the acute phase.

RECENT FINDINGS

During the last year, a number of important studies on nutritional needs in the critically ill have been published, including large randomized controlled trials. In particular studies addressing the needs for energy and proteins in the critically ill have imparted new knowledge in this field. However, there are few studies concerning the rehabilitation phase after critical illness.

SUMMARY

Although the recent findings and publications contribute to a more nuanced understanding of nutrition during critical illness, the implications for clinical practice are not in discord with the current recommendations of guidelines.

Parenteral nutrition in the ICU setting: need for a shift in utilization

PURPOSE OF REVIEW

The difficulties to feed the patients adequately with enteral nutrition alone have drawn the attention of the clinicians toward the use of parenteral nutrition, although recommendations by the recent guidelines are conflicting. This review focuses on the intrinsic role of parenteral nutrition, its new indication, and modalities of use for the critically ill patients.

RECENT FINDINGS

A recent trial demonstrated that selecting either parenteral nutrition or enteral nutrition for early nutrition has no impact on clinical outcomes. However, it must be acknowledged that the risk of relative overfeeding is greater when using parenteral nutrition and the risk of underfeeding is greater when using enteral nutrition because of gastrointestinal intolerance. Both overfeeding and underfeeding in the critically ill patients are associated with deleterious outcomes. Thus, early and adequate feeding according to the specific energy needs can be recommended as the optimal feeding strategy.

SUMMARY

Parenteral nutrition can be used to substitute or supplement enteral nutrition, if adequately prescribed. Testing for enteral nutrition tolerance during 2-3 days after ICU admission provides the perfect timing to start parenteral nutrition, if needed. In case of absolute contraindication for enteral nutrition, consider starting parenteral nutrition carefully to avoid overfeeding.

Energy expenditure in mechanically ventilated patients: The weight of body weight!

BACKGROUND & AIMS

Optimal nutritional care for intensive care unit (ICU) patients requires precise determination of energy expenditure (EE) to avoid deleterious under- or overfeeding. The reference method, indirect calorimetry (IC), is rarely accessible and inconstantly feasible. Various equations for predicting EE based on body weight (BW) are available. This study aims at determining the best prediction strategy unless IC is available.

METHODS

Mechanically ventilated patients staying ≥72 h in the ICU were included, except those with contraindications for IC measurements. IC and BW measurements were routinely performed. EE was predicted by the ESPEN formula and other predictive equations using BW (i.e. anamnestic (AN), measured (MES), adjusted for cumulated water balance (ADJ), calculated for a body mass index (BMI) of 22.5). Comparisons were made using Pearson correlation and Bland & Altman plots.

RESULTS

85 patients (57 ± 19 y, 61 men, SAPS II 43 ± 16) were included. Correlations between IC and predicted EE using the ESPEN formula with different BW (BW_AN, BW_MES, BW_ADJ, and BW_BMI22.5) were 0.44, 0.40, 0.36, and 0.47, respectively. Bland & Altman plots showed wide and inconsistent variations. Predictive equations including body temperature and minute ventilation showed the best correlations, but when using various BWs, differences in predicted EE were observed.

CONCLUSION

No EE predictive equation, regardless of the BW used, gives statistically identical results to IC. If IC cannot be performed, predictive equations including minute ventilation and body temperature should be preferred. BW has a significant impact on estimated EE and the use of measured BW_MES or BW _{BMI 22.5} is associated with the best EE prediction. Clinical trial registration number on ClinicalTrial.gov: NCT02552446. Ethical committee number: CE-14-070.

Protein-energy nutrition in the ICU is the power couple: A hypothesis forming analysis

BACKGROUND & AIMS

We hypothesize that an optimal and simultaneous provision of energy and protein is favorable to clinical outcome of the critically ill patients.

METHODS

We conducted a review of the literature, obtained via electronic databases and focused on the metabolic alterations during critical illness, the estimation of energy and protein requirements, as well as the impact of their administration.

RESULTS

Critically ill patients undergo severe metabolic stress during which time a great amount of energy and protein is utilized in a variety of reactions essential for survival. Energy provision for critically ill patients has drawn attention given its association with morbidity, survival and long-term recovery, but protein provision is not sufficiently taken into account as a critical component of nutrition support that influences clinical outcome. Measurement of energy expenditure is done by indirect calorimetry, but protein status cannot be measured with a bedside technology at present.

CONCLUSIONS

Recent studies suggest the importance of optimal and combined provision of energy and protein to optimize clinical outcome. Clinical randomized controlled studies measuring energy and protein targets should confirm this hypothesis and therefore establish energy and protein as a power couple.

Monitoring nutrition and glucose in acute brain injury

The metabolic response to injury is well described; however, very little is understood about optimal markers to measure this response. This summary will address the current evidence about monitoring nutritional status including blood glucose after acute brain injury (ABI). An electronic literature search was conducted for English language articles describing the testing, utility, and optimal methods to measure nutritional status and blood glucose levels in the neurocritical care population. A total of 45 articles were included in this review. Providing adequate and timely nutritional support can help improve outcome after ABI. However, the optimal content and total nutrition requirements remain unclear. In addition, how best to monitor the nutritional status in ABI is still being elucidated, and at present, there is no validated optimal method to monitor the global response to nutritional support on a day-to-day basis in ABI patients. Nitrogen balance may be monitored to assess the adequacy of caloric intake as it relates to protein energy metabolism, but indirect calorimetry, anthropometric measurement, or serum biomarker requires further validation. The adverse effects of hyperglycemia in ABI are well described, and data indicate that blood glucose should be carefully controlled in critically ill patients. However, the optimal frequency or duration for blood glucose monitoring after ABI remains poorly defined. There are significant knowledge gaps about monitoring nutritional status and response to nutritional interventions in ABI; these need to be addressed and hence few recommendations can be made. The optimal frequency and duration of blood glucose monitoring need further study.

When and how should sepsis patients be fed?

PURPOSE OF REVIEW

To provide an overview on the recent literature regarding metabolism during sepsis and outcome-related effects of nutrition therapy in septic patients. The question when and how these patients should be fed with respect to macronutrient intake is elaborated.

RECENT FINDINGS

Although the incidence of severe sepsis has steadily increased over the past years, still no strong evidence is available with respect to the role of energy and protein provision in these patients. On the basis of recent large randomized trials in mixed patient populations, the updated sepsis guidelines recommend early but limited nutrition via the enteral route rather than targeted feeding. Lately, the results of a large trial challenged the importance of the route of feeding on the clinical outcome of critically ill patients. Four post-hoc analyses of prospective randomized trials including a large number of severely septic patients yielded conflicting results. One reported significant mortality reduction with near-target calorie and protein intake by exclusive enteral nutrition, whereas the second showed an advantage of enteral compared to combined nutrition, albeit resulting in a lower calorie and protein provision. The other two analyses found no association at all of either lower or higher daily caloric or protein intake, respectively, with clinical outcomes.

SUMMARY

In the absence of strong clinical evidence, pathophysiological findings are discussed and nutritional strategies for septic patients derived. Future studies should explore the individual response to specific exogenous supply of macronutrients and micronutrients in the acute and persistent phase of severe systemic inflammation.

Energy requirements and the use of predictive equations versus indirect calorimetry in critically ill patients

Nutrition support has been shown to have a positive impact on critically ill patients who meet their defined goals of nutrition therapy. However, inappropriate energy assessment can contribute to under- or overfeeding resulting in deleterious effects. Thus, assessment of energy expenditure in critically ill patients is crucial to prevent negative impacts from inappropriate feeding. Currently, the optimal energy requirement and appropriate energy assessment in these patients is controversial. Indirect calorimetry or predictive equations have been suggested to evaluate energy expenditure in critically ill patients. Indirect calorimetry is a gold standard for evaluating energy expenditure, but it is not always available and has some limitations. Many predictive equations, therefore, have been developed to predict energy expenditure in critically ill patients. However, these equations cannot be used generally in these patients since they were developed in a unique patient population. Many studies compared measured energy expenditure with predictive energy expenditure, but the data regarding accuracy is not robust. Therefore, clinicians should consider using these equations carefully based on the current supporting data. Indirect calorimetry is recommended for use in evaluating energy expenditure in critically ill patients if it is available.

Validity of predictive equations for resting energy expenditure according to the body mass index in a population of 1726 patients followed in a Nutrition Unit

BACKGROUND & AIMS

The resting energy expenditure (REE) predictive formulas are often used in clinical practice to adapt the nutritional intake of patients or to compare to REE measured by indirect calorimetry. We aimed to evaluate which predictive equations was the best alternative to REE measurements according to the BMI.

METHODS

28 REE prediction equations were studied in a population of 1726 patients without acute or chronic high-grade inflammatory diseases followed in a Nutrition Unit for malnutrition, eating disorders or obesity. REE was measured by indirect calorimetry for 30 min after a fasting period of 12 h. Some formulas requiring fat mass and free-fat mass, body composition was measured by bioelectrical impedance analysis. The percentage of accurate prediction (±10%/REE measured) and Pearson r correlations were calculated.

RESULTS

Original Harris & Benedict equation provided 73.0% of accurate predictions in normal BMI group but only 39.3% and 62.4% in patients with BMI < 16 kg m(-2) and BMI ≥ 40 kg m(-2), respectively. In particularly, this equation overestimated the REE in 51.74% of patients with BMI < 16 kg m(-2). Huang equation involving body composition provided the highest percent of accurate prediction, 42.7% and 66.0% in patients with BMI < 16 and >40 kg m(-2), respectively.

CONCLUSION

Usual predictive equations of REE are not suitable for predicting REE in patients with extreme BMI, in particularly in patients with BMI <16 kg m(-2). Indirect Calorimetry may still be recommended for an accurate assessment of REE in this population until the development of an adapted predictive equation.

Body cell mass evaluation in critically ill patients: killing two birds with one stone

Body cell mass (BCM) is the metabolically active cell mass involved in O₂ consumption, CO₂ production and energy expenditure. BCM measurement has been suggested as a tool for the evaluation of nutritional status. Since BCM is closely related to energy expenditure, it could also represent a good reference value for the calculation of nutrient needs. In a recent issue of Critical Care, Ismael and colleagues used bioelectrical impedance analysis parameters and anthropometric variables to evaluate BCM in patients with acute kidney injury, before and after a hemodialysis session. The results of this study suggest that BCM is relatively insensitive to major body fluid shifts, a well known factor interfering with nutritional evaluation/monitoring and energy need calculations in the ICU. Thus, BCM seems to be a more 'stable' nutritional variable, as it is apparently less influenced by non-nutritional factors. The results of this paper emphasize the need to identify biologically sound parameters for nutritional status evaluation and energy need calculation in critically ill patients; in this regard, BCM could fulfill these expectations.

When more is better

Nutrition support of critically ill patients with sepsis is one of the most debated issues among intensivists. The latest international sepsis guidelines recommend the prescription of a low volume of feeds through gastric or intestinal enteral nutrition (EN) for 7 days after admission to the ICU. The data to support such recommendations are scarce, and large trials are needed to clarify this issue. As reported in the previous issue of Critical Care, Elke and colleagues have revisited a database containing 13,630 ICU patients, of whom 2,270 met four inclusion criteria: sepsis or pneumonia, ICU stay of at least 3 days, mechanical ventilation within 48 hours after ICU admission, and exclusive EN. The goal of the authors was to assess the impact of various levels of energy and protein administration on mortality at 60 days after ICU admission and on the duration of mechanical ventilation. They found that standard levels of energy and protein recommended by international guidelines for patients in the ICU do also apply to patients with sepsis in the ICU. This is an important finding, which contradicts the current recommendations and beliefs for this subgroup of patients in the ICU and gives a strong rationale for launching a large prospective randomized trial.