Measuring resting energy expenditure during extracorporeal membrane oxygenation: preliminary clinical experience with a proposed theoretical model

Nutrition management of a patient following emergent pneumonectomy due to chest wall trauma

Emergent total pneumonectomy is a rare surgical intervention for patients with severe chest trauma. Patients who survive the immediate postoperative period experience prolonged, complex hospitalizations. The purpose of this case study is to review the nutrition care provided to a patient who survived total pneumonectomy and the supporting evidence. John Doe (JD) is a man aged 28 years who presented to a level I trauma center with penetrating chest trauma. He required multiple operative interventions, resulting in a partial right and total left pneumonectomy. JD's hospitalization was complicated by prolonged use of extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). His surgical course and gastric feeding intolerance hampered enteral nutrition adequacy, and parenteral nutrition support was initiated on hospital day 17. Tolerance to enteral nutrition improved after jejunal access was obtained, and the patient transitioned to total enteral nutrition support. As a result of inflammatory metabolic changes and nutrition delivery challenges for the first 2 weeks of hospitalization, JD developed malnutrition. His nutrition care was further complicated by copper and carnitine deficiencies, which have been described in patients requiring ECMO and CRRT. Patients who require emergent total pneumonectomy following traumatic chest injuries will likely require complex hospital care, including extracorporeal organ support. These patients present unique nutrition challenges; however, given the relative infrequency of the intervention, there is limited research to guide clinical practice. Additional research on nutrition interventions in this population is warranted.

Nutrition and outcomes in venovenous extracorporeal membrane oxygenation: An observational cohort study

BACKGROUND

Overfeeding and underfeeding are associated with negative outcomes during critical illness. The purpose of this retrospective study was to assess the association between nutrition intake and outcomes for patients receiving venovenous (VV) extracorporeal membrane oxygenation (ECMO).

METHODS

Adults who received VV ECMO August 2017 to June 2020 were screened. Patients with <3 ECMO nutrition support days were excluded. Age, sex, height, weight, ideal body weight (IBW), body mass index, sequential organ failure assessment score, respiratory ECMO survival prediction score, energy, and protein goals were collected. All nutrition intake was collected for the first 14 days of ECMO or until death, decannulation, or oral diet initiation. Outcomes analyzed included mortality and VV ECMO duration. The relationship between nutrition delivery and outcomes was tested with multivariate analysis. Univariate analyses were conducted on obese and nonobese subgroups.

RESULTS

A total of 2044 nutrition days in 178 patients were analyzed. The median estimated needs were 24 (interquartile range: 22.3-28.3) kcal/kg/day and 2.25 (interquartile range: 2.25-2.77) g/kg/day of protein using IBW in patients with obesity and actual weight in patients without obesity. Patients received 83% of energy and 63.3% of protein targets. Patients with obesity who received ≥2 g/kg IBW of protein had a significantly shorter ECMO duration (P = 0.037). Increased protein intake was independently associated with a reduced risk of death (odds ratio: 0.06; 95% confidence interval: 0.01-0.43).

CONCLUSION

Higher protein intake was associated with reduced mortality. Optimal energy targets for patients receiving ECMO are currently unknown and warrant further study.

The Influence of Prone Positioning on Energy and Protein Delivery in COVID-19 Patients Requiring ECMO Support

BACKGROUND

Gastrointestinal dysfunction is a common complication of medical nutrition therapy in critically ill patients. Whether prone positioning leads to a deterioration in gastrointestinal function has not been fully clarified. Thus, we aimed to analyze the influence of prone positioning on the tolerance of medical nutrition therapy.

METHODS

We conducted a retrospective analysis of 102 SARS-CoV-2 infected patients with venovenous extracorporeal membrane oxygenation support (VV ECMO). Gastric residual volume (GRV) was used to assess the tolerance of enteral nutrition.

RESULTS

Nutritional data were collected for 2344 days. Undernutrition was observed in 40.8%, with a significantly higher incidence on days in prone position (48.4% versus 38.6%, p < 0.001). On days in supine position, significantly more calories were administered enterally than on days in prone position (p < 0.001). The mean GRV/24 h was 111.1 mL on days in supine position and 187.3 mL on days in prone position (p < 0.001). Prone positioning was associated with higher rates of GRV of ≥500 mL/24 h independent of age, disease severity at ECMO start, ECMO runtime and ICU length of stay (adjusted hazard ratio: 4.06; 95%CI: 3.0-5.5; p < 0.001).

CONCLUSIONS

Prone position was associated with lower tolerance of enteral nutrition, as indicated by an increased GRV. As a result, reduced enteral nutritional support was administered.

Metabolic support for patients on extra-corporeal membrane oxygenation

PURPOSE OF REVIEW

The purpose of the review is to summarize recent research on metabolic support during extracorporeal membrane oxygenation. In this review, we cover the evidence on nutritional supplementation, both the route of supplementation, timing of initiation of supplementation as well as quantities of supplementation needed. In addition, we discuss the recent trend in awake extracorporeal membrane oxygenation (ECMO) and its benefits to patients.

RECENT FINDINGS

As ECMO use continues to increase over the last few years, for both cardiovascular as well as respiratory failure, the need to optimize the metabolic states of patients has arisen. Increasing evidence has pointed towards this hitherto unexplored domain of patient care having a large impact on outcomes. Additionally, strategies such as awake ECMO for select patients has allowed them to preserve muscle mass which could aid in a faster recovery.

SUMMARY

There is a role of optimal metabolic support in the early recovery of patients on ECMO that is currently under-recognized. Future directions of research that aim to improve post ECMO outcomes must focus on this area.

Nutritional support in the cardiac intensive care unit

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

Challenges of Nutrition Support in Pediatric Patients Requiring Extracorporeal Membrane Oxygenation

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

High protein intake and nitrogen balance in patients receiving venovenous extracorporeal membrane oxygenation: A descriptive cohort study

BACKGROUND

This retrospective cohort study sought to describe the ability of high protein regimens to achieve nitrogen equilibrium in patients receiving venovenous extracorporeal membrane oxygenation (VV ECMO).

METHODS

Patients aged ≥18 years with a documented nitrogen balance study (NB) on VV ECMO between February 2018 and December 2021 were included. Studies with incomplete 24-h urine collections or changes in blood urea nitrogen ≥10 mg/dl were excluded. Data were summarized, correlation between first NB and potentially contributing variables was assessed with Kendall tau. Subanalysis described findings after stratifying for weight class (obese vs nonobese) and duration of VV ECMO at the time of NB.

RESULTS

A total of 68 NBs in 30 patients were included; 47% of the cohort had obesity. The number of NBs per patient was 2.2 ± 1.1, which were completed on a median of 31.5 (interquartile range: 16, 53.8) days receiving ECMO. Nitrogen equilibrium or positive balance was achieved in 72% of studies despite elevated nitrogen excretion. Patients received 87.9 ± 16.8% of prescribed protein on NB days for average intakes of 2.4 ± 0.4 g/kg of actual weight per day and 2.4 ± 0.5 g/kg of ideal weight per day in patients without and with obesity. Median NB in patients without obesity was -1.46 (-8.96, 2.98) g/day and -0.21 (-10.58, 4.04) g/day in patients with obesity. A difference in median NB after stratification for timing was observed (P = 0.029).

CONCLUSION

Nitrogen equilibrium can be achieved with high protein intake in adults receiving VV ECMO. NB monitoring is one tool to individualize protein prescriptions throughout the course of VV ECMO.

Nutrition support for patients on mechanical circulatory support

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Metabolic and nutritional aspects in continuous renal replacement therapy

Nutrition is one of the foundations for supporting and treating critically ill patients. Nutritional support provides calories, protein, electrolytes, vitamins, and trace elements via the enteral or parenteral route. Acute kidney injury (AKI) is a common and devastating problem in critically ill patients and has significant metabolic and nutritional consequences. Moreover, renal replacement therapy (RRT), whatever the modality used, also profoundly impacts metabolism. RRT and of the extracorporeal circuit impede 'effect the evaluation of a patient's energy requirements by clinicians. Substrates added and removed within the extracorporeal treatment are not always taken into consideration, making treatment even more challenging. Furthermore, evidence on nutritional support during continuous renal replacement therapy (CRRT) is scarce, and there are no clinical guidelines for nutrition adaptations during CRRT in critically ill patients. Most recommendations are based on expert opinions. This review discusses the complex interaction between nutritional support and CRRT and presents some milestones for nutritional support in critically ill patients on CRRT.

Inadequate Energy Delivery Is Frequent among COVID-19 Patients Requiring ECMO Support and Associated with Increased ICU Mortality

BACKGROUND

Patients receiving extracorporeal membrane oxygenation (ECMO) support are at high risk for malnutrition. There are currently no general nutrition guidelines for coronavirus disease 2019 (COVID-19) patients during ECMO therapy.

METHODS

We conducted a retrospective analysis of COVID-19 patients requiring venovenous ECMO support at a large tertiary hospital center. Nutrition goals were calculated using 25 kcal/kg body weight (BW)/day. Associations between nutrition support and outcome were evaluated using Kaplan-Meier and multivariable Cox regression analyses.

RESULTS

Overall, 102 patients accounted for a total of 2344 nutrition support days during ECMO therapy. On 40.6% of these days, nutrition goals were met. Undernutrition was found in 40.8%. Mean daily calorie delivery was 73.7% of calculated requirements, mean daily protein delivery was 0.7 g/kg BW/d. Mean energy intake of ≥70% of calculated targets was associated with significantly lower ICU mortality independently of age, disease severity at ECMO start and body mass index (adjusted hazard ratio: 0.372, p = 0.007).

CONCLUSIONS

Patients with a mean energy delivery of ≥70% of calculated targets during ECMO therapy had a better ICU survival compared to patients with unmet energy goals. These results indicate that adequate nutritional support needs to be a major priority in the treatment of COVID-19 patients requiring ECMO support.

Indirect Calorimetry in Spontaneously Breathing, Mechanically Ventilated and Extracorporeally Oxygenated Patients: An Engineering Review

Indirect calorimetry (IC) is considered the gold standard for measuring resting energy expenditure (REE). This review presents an overview of the different techniques to assess REE with special regard to the use of IC in critically ill patients on extracorporeal membrane oxygenation (ECMO), as well as to the sensors used in commercially available indirect calorimeters. The theoretical and technical aspects of IC in spontaneously breathing subjects and critically ill patients on mechanical ventilation and/or ECMO are covered and a critical review and comparison of the different techniques and sensors is provided. This review also aims to accurately present the physical quantities and mathematical concepts regarding IC to reduce errors and promote consistency in further research. By studying IC on ECMO from an engineering point of view rather than a medical point of view, new problem definitions come into play to further advance these techniques.

Quantitative Gas Exchange in Extracorporeal Membrane Oxygenation-A New Device: Accuracy, Approach-based Difficulties, and Caloric Targeting

Measurement of oxygen uptake (VO 2 ) and carbon dioxide removal (VCO 2 ) on membrane lungs (MLs) during extracorporeal membrane oxygenation (ECMO) provides potential for improved and safer therapy. Real-time monitoring of ML function and degradation, calculating caloric needs as well as cardiac output, and weaning algorithms are among the future possibilities. Our study compared the continuous measurement of the standalone Quantum Diagnostics System (QDS) with the published Measuring Energy Expenditure in ECMO patients (MEEP) approach, which calculates sequential VO 2 and VCO 2 values via blood gas analysis and a physiologic gas content model. Thirty-nine datasets were acquired during routine venovenous ECMO intensive care treatment and analyzed. VO 2 was clinically relevant underestimated via the blood-sided measurement of the QDS compared to the MEEP approach (mean difference -42.61 ml/min, limits of agreement [LoA] -2.49/-87.74 ml), which could be explained by the missing dissolved oxygen fraction of the QDS equation. Analysis of VCO 2 showed scattered values with wide limits of agreement (mean difference 54.95 ml/min, LoA 231.26/-121.40 ml/min) partly explainable by a calculation error of the QDS. We described potential confounders of gas-sided measurements in general which need further investigation and recommendations for enhanced devices.

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

OBJECTIVES

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

DESIGN

Retrospective observational study.

SETTING

A tertiary high ECMO volume academic institution.

PATIENTS/SUBJECTS

Ten adult ARDS patients on venovenous ECMO.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Methodological Aspects of Indirect Calorimetry in Patients with Sepsis-Possibilities and Limitations

The aim of the review was to analyse the challenges of using indirect calorimetry in patients with sepsis, including the limitations of this method. A systematic review of the literature was carried out. The analysis concerned the methodology and presentation of research results. In most studies assessing energy expenditure, energy expenditure was expressed in kcal per day (n = 9) and as the mean and standard deviation (n = 7). Most authors provided a detailed measurement protocol, including measurement duration (n = 10) and device calibration information (n = 7). Ten papers provided information on the day of hospitalisation when the measurements were obtained, nine on patient nutrition, and twelve on the criteria for inclusion and exclusion of participants from the study. Small study group sizes and study at a single centre were among the most cited limitations. Studies assessing energy expenditure in patients with sepsis by indirect calorimetry differ in the methodology and presentation of results, and their collective analysis is difficult. A meta-analysis of the results could enable multi-site and large patient evaluation. Standardisation of protocols and presentation of all collected data would enable their meta-analysis, which would help to achieve greater knowledge about metabolism in sepsis.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Gas exchange calculation may estimate changes in pulmonary blood flow during veno-arterial extracorporeal membrane oxygenation in a porcine model

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is used as rescue therapy for severe cardiopulmonary failure. We tested whether the ratio of CO₂ elimination at the lung and the V-A ECMO (V̇co_2ECMO/V̇co_2Lung) would reflect the ratio of respective blood flows and could be used to estimate changes in pulmonary blood flow (Q̇_Lung), i.e., native cardiac output. Four healthy pigs were centrally cannulated for V-A ECMO. We measured blood flows with an ultrasonic flow probe. V̇co_2ECMO and V̇co_2Lung were calculated from sidestream capnographs under constant pulmonary ventilation during V-A ECMO weaning with changing sweep gas and/or V-A ECMO blood flow. If ventilation-to-perfusion ratio (V̇/Q̇) of V-A ECMO was not 1, the V̇co_2ECMO was normalized to V̇/Q̇ = 1 (V̇co_2ECMONorm). Changes in pulmonary blood flow were calculated using the relationship between changes in CO₂ elimination and V-A ECMO blood flow (Q̇_ECMO). Q̇_ECMO correlated strongly with V̇co_2ECMONorm (r² 0.95–0.99). Q̇_Lung correlated well with V̇co_2Lung (r² 0.65–0.89, P < = 0.002). Absolute Q̇_Lung could not be calculated in a nonsteady state. Calculated pulmonary blood flow changes had a bias of 76 (−266 to 418) mL/min and correlated with measured Q̇_Lung (r² 0.974–1.000, P = 0.1 to 0.006) for cumulative ECMO flow reductions. In conclusion, V̇co₂ of the lung correlated strongly with pulmonary blood flow. Our model could predict pulmonary blood flow changes within clinically acceptable margins of error. The prediction is made possible with normalization to a V̇/Q̇ of 1 for ECMO. This approach depends on measurements readily available and may allow immediate assessment of the cardiac output response.

Energy expenditure and caloric targets during continuous renal replacement therapy under regional citrate anticoagulation. A viewpoint

BACKGROUND

Indirect calorimetry (IC) is the gold standard for measuring energy expenditure in critically ill patients However, continuous renal replacement therapy (CRRT) is a formal contraindication for IC use.

AIMS

To discuss specific issues that hamper or preclude an IC-based assessment of energy expenditure and correct caloric prescription in CRRT-treated patients.

METHODS

Narrative review of current literature.

RESULTS

Several relevant pitfalls for validation of IC during CRRT were identified. First, IC measures CO2 production (VCO2) and O2 consumption to calculate resting energy expenditure (REE) with the Weir equation. VCO2 measurements are influenced by CRRT because CO2 is exchanged during the blood purification process. CO2 exchange also depends on type of pre- and/or postdilution fluid(s). CO2 dissolves in different forms with dynamic but unpredictable impact on VCO2. Second, the effect of immunologic activation and heat loss on REE caused by extracorporeal circulation during CRRT is poorly documented. Third, caloric prescription should be adapted to CRRT-induced in- and efflux of different nutrients. Finally, citrate, which is the preferred anticoagulant for CRRT, is a caloric source that may influence IC measurements and REE.

CONCLUSION

Better understanding of CRRT-related processes is needed to assess REE and provide individualized nutritional therapy in this condition.

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.

Clinical Nutrition in Critical Care Medicine - Guideline of the German Society for Nutritional Medicine (DGEM)

PURPOSE

Enteral and parenteral nutrition of adult critically ill patients varies in terms of the route of nutrient delivery, the amount and composition of macro- and micronutrients, and the choice of specific, immune-modulating substrates. Variations of clinical nutrition may affect clinical outcomes. The present guideline provides clinicians with updated consensus-based recommendations for clinical nutrition in adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function.

METHODS

The former guidelines of the German Society for Nutritional Medicine (DGEM) were updated according to the current instructions of the Association of the Scientific Medical Societies in Germany (AWMF) valid for a S2k-guideline. According to the S2k-guideline classification, no systematic review of the available evidence was required to make recommendations, which, therefore, do not state evidence- or recommendation grades. Nevertheless, we considered and commented the evidence from randomized-controlled trials, meta-analyses and observational studies with adequate sample size and high methodological quality (until May 2018) as well as from currently valid guidelines of other societies. The liability of each recommendation was described linguistically. Each recommendation was finally validated and consented through a Delphi process.

RESULTS

In the introduction the guideline describes a) the pathophysiological consequences of critical illness possibly affecting metabolism and nutrition of critically ill patients, b) potential definitions for different disease phases during the course of illness, and c) methodological shortcomings of clinical trials on nutrition. Then, we make 69 consented recommendations for essential, practice-relevant elements of clinical nutrition in critically ill patients. Among others, recommendations include the assessment of nutrition status, the indication for clinical nutrition, the timing and route of nutrient delivery, and the amount and composition of substrates (macro- and micronutrients); furthermore, we discuss distinctive aspects of nutrition therapy in obese critically ill patients and those treated with extracorporeal support devices.

CONCLUSION

The current guideline provides clinicians with up-to-date recommendations for enteral and parenteral nutrition of adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. The period of validity of the guideline is approximately fixed at five years (2018-2023).

Nutritional support in patients with extracorporeal life support and ventricular assist devices

PURPOSE OF REVIEW

Extracorporeal life support (ECLS) including venovenous and venoarterial extracorporeal membrane oxygenation (ECMO) and ventricular assist devices (VAD) provide mechanical pulmonary and circulatory support, respectively, in patients with acute pulmonary or cardiovascular failure. This review discusses recently published data regarding specific topics of nutritional support in patients with ECLS and VAD.

RECENT FINDINGS

ECLS may aggravate loss of endogenous and exogenous micronutrients and macronutrients. Observational studies have shown that enteral nutrition is feasible and most commonly used in patients with ECLS. Indirect calorimetry may be feasible for measuring energy expenditure during ECLS. Specific tools are available to assess malnutrition or nutrition risk in patients with VAD but require further validation in the perioperative setting. If parenteral nutrition is indicated, the use of intravenous lipid emulsions may be associated with membrane oxygenator dysfunction of the ECLS device or increased infectious risk in patients with VAD.

SUMMARY

Despite the exponential use of ECLS and VAD over the last decade, the role of nutrition on clinical outcome in this patient population remains an important but yet underinvestigated field.

Energy expenditure of patients on ECMO: A prospective pilot study

BACKGROUND

An optimal nutritional approach sustained by convenient monitoring of metabolic status and reliable assessment of energy expenditure (EE) may improve the outcome of critically ill patients on extracorporeal membrane oxygenation (ECMO). We previously demonstrated the feasibility of indirect calorimetry (IC)-the standard of care technique to determine caloric targets-in patients undergoing ECMO. This study aims to compare measured with calculated EE during ECMO treatment. We additionally provide median EE values for use in settings where IC is not available.

METHODS

IC was performed in seven stable ECMO patients. Gas exchange was analyzed at the ventilator, and ECMO side and values were introduced in a modified Weir formula to calculate resting EE. Results were compared with EE calculated with the Harris-Benedict equation and with the 25 kcal/kg/day ESPEN recommendation.

RESULTS

Total median oxygen consumption rate was 196 (Q1-Q3 158-331) mL/min, and total median carbon dioxide production was 150 (Q1-Q3 104-203) mL/min. Clinically relevant differences between calculated and measured EE were observed in all patients. The median EE was 1334 (Q1-Q3 1134-2119) kcal/24 hours or 18 (Q1-Q3 15-27) kcal/kg/day.

CONCLUSION

Compared with measured EE, calculation of EE both over- and underestimated caloric needs during ECMO treatment. Despite a median EE of 21 kcal/kg/day, large variability in metabolic rate was found and demands further investigation.

Indirect calorimetry as point of care testing

Determining energy requirement is a fundamental of nutrition support. Indirect calorimetry (IC) has been long recognized as the gold standard for assessing basal or resting energy expenditure (REE). The measurement of REE is recommended particularly in the situation where adjustment of energy provision is critical. The result of the IC measurement can lead to changes in treatment and since the change can be carried out immediately at the bedside, this may be considered as point-of-care testing. Beyond the nutritional aspects, studies of energy expenditure with IC have brought out more understanding of the metabolic changes during the natural course of diseases or conditions as well as those related to the intervention. The literature in various disease states has shown that changes in energy expenditure may reveal hidden metabolic information that might be translated into clinical information and have the potential of being both prognostic indicators and/or treatment targets.

Nitrogen Balance During Venovenous Extracorporeal Membrane Oxygenation Support: Preliminary Results of a Prospective, Observational Study

BACKGROUND

Current literature is insufficient to support specific guidelines for estimating nutrition needs during extracorporeal membrane oxygenation (ECMO). The purpose of this single-center observational study was to investigate protein catabolism during venovenous (VV) ECMO support and assess whether current nutrition recommendations were adequate.

METHODS

All patients admitted to the Lung Rescue Unit between November 2016 and June 2017 were screened for eligibility. Patients with a documented nitrogen balance (NB) study were included in the data set. NB results were excluded for a change in blood urea nitrogen ≥10 mg/dL during the urine collection or unquantified nitrogen losses. Demographics, ECMO-specific data, NB, nutrition prescription, and infusion were recorded in a prospective, observational manner.

RESULTS

After exclusions, 25 NB results in 16 patients were included for analysis. Nonobese (body mass index [BMI] ˂ 30 kg/m² ) and obese (BMI ≥ 30 kg/m² ) patients received 85% and 84% of their prescribed protein, respectively. Nonobese patients had a mean NB of -1.7 ± 5.7, whereas obese patients had a mean NB of -11.5 ± 9.6. Obese patients displayed significantly higher urine urea nitrogen (26.7 ± 7.7 vs 13.5 ± 4.3; P = .00004).

CONCLUSIONS

These preliminary findings suggest that current guidelines for estimating protein needs in critically ill patients may be adequate for nonobese patients receiving VV ECMO. However, current protein recommendations for critically ill obese patients may not be adequate during VV ECMO support, possibly related to significantly higher rates of catabolism. Future studies with a larger cohort of patients are needed to confirm these results.

Venovenous Extracorporeal Membrane Oxygenation in an Adult Patient With Prader-Willi Syndrome: A Nutrition Case Report

Prader-Willi Syndrome (PWS) is a genetic condition that results in a constellation of symptoms and typically results in hyperphagia and obesity in adulthood. Critically ill adults with PWS present a unique challenge to the nutrition professional, particularly when they require support modalities such as extracorporeal membrane oxygenation (ECMO). The purpose of this case study is to review the nutrition care of a critically ill adult patient with PWS who required venovenous ECMO. The patient was successfully managed with a hypocaloric, high-protein approach, which did not result in the diagnosis of malnutrition during his hospitalization. The patient was ultimately transitioned off extracorporeal life support and discharged to a rehabilitation facility.

Adequacy of nutrition support during extracorporeal membrane oxygenation

BACKGROUND

The use of veno-venous extracorporeal membrane oxygenation (vv-ECMO) is increasing in adults with severe respiratory failure. Observational data suggest that there are significant challenges to providing adequate nutrition support for patients on vv-ECMO. We aimed to describe firstly the nutrition support practices in a large single-centre providing vv-ECMO to adults and secondly any association with clinical outcome.

METHODS

We conducted a retrospective review of patients receiving vv-ECMO on the Intensive Care Unit (ICU) of a large London teaching hospital. Adult patients admitted to the ICU with severe respiratory failure between December 2010 and December 2015 were included. Daily energy and protein delivery were compared with estimated targets and reasons for feeding interruptions were collected from electronic medical records. Adequate feeding was defined as 80-110% of estimated targets.

RESULTS

We analysed 203 eligible patients. Median duration of ICU stay was 21.0 (IQR, 15.0-33.0) days and vv-ECMO 10.0 (IQR, 7.0-16.0) days. Although median energy (89.8% (IQR, 80.5-96.0%)) and protein (84.7% (IQR, 74.0-96.7%)) delivery was adequate, underfeeding of either energy or protein occurred on nearly one third (28.3%) of nutrition support days. A higher admission severity of illness score was associated with inadequate protein delivery (p = 0.040). Patients with more severe organ dysfunction on the first day of vv-ECMO received inadequate energy (p = 0.026). The most common reasons for interrupted feeding were medical procedures (39.1%) followed by poor gastric motility (22.8%).

CONCLUSION

Adequate energy and protein delivery during vv-ECMO is possible but underfeeding is still common, especially in those who are more severely ill or who have more severe organ dysfunction. Patients with inadequate energy or protein delivery did not differ in ICU and 6-month survival. Prospective studies investigating optimal feeding in this patient cohort are required.

A brief clinical case of monitoring of oxygenator performance and patient-machine interdependency during prolonged veno-venous extracorporeal membrane oxygenation

Monitoring veno-venous extracorporeal membrane oxygenation (vvECMO) during 76 days of continuous support in a 42-years old patient with end-stage pulmonary disease, listed for double-lung transplantation. Applying a new monitor (Landing®, Eurosets, Medolla, Italy) and describing how measured and calculated parameters can be used to understand the variable interdependency between artificial membrane lung (ML) and patient native lung (NL). During vvECMO, in order to understand how the respiratory function is shared between ML and NL, ideally we should obtain data about oxygen transfer and CO2 removal, both by ML and NL. Measurements for NL can be made on the mechanical ventilator. Measurements for ML are typically made from gas analysis on blood samples drawn from the ECMO system before and after the oxygenator, and therefore are non-continuous. Differently, the Landing monitor provides a continuous measurement of the oxygen transfer from the ML, combined with hemoglobin level, saturation of drained blood and saturation of reinfused blood. Moreover, the Landing monitor provides hemodynamics data about circulation through the ECMO system, with blood flow, pre-oxygenator pressure and post-oxygenator pressure. Of note, measurements include the drain negative pressure, whose monitoring may be particularly useful to prevent hemolysis. Real-time monitoring of vvECMO provides data helpful to understand the complex picture of a patient with severely damaged lungs on one side and an artificial lung on the other side. Data from vvECMO monitoring may help to adapt the settings of both mechanical ventilator and vvECMO. Data about oxygen transfer by the oxygenator are important to evaluate the performance of the device and may help to avoid unnecessary replacements, thus reducing risks and costs.

Do PICU patients meet technical criteria for performing indirect calorimetry?

BACKGROUND & AIMS

Indirect calorimetry (IC) is considered gold standard for assessing energy needs of critically ill children as predictive equations and clinical status indicators are often unreliable. Accurate assessment of energy requirements in this vulnerable population is essential given the high risk of over or underfeeding and the consequences thereof. The proportion of patients and patient days in pediatric intensive care (PICU) for which energy expenditure (EE) can be measured using IC is currently unknown. In the current study, we aimed to quantify the daily proportion of consecutive PICU patients who met technical criteria to perform indirect calorimetry and describe the technical contraindications when criteria were not met.

METHODS

Prospective, observational, single-centre study conducted in a cardiac and general PICU. All consecutive patients admitted for at least 96 h were included in the study. Variables collected for each patient included age at admission, admission diagnosis, and if technical criteria for indirect calorimetry were met. Technical criteria variables were collected within the same 2 h each morning and include: provision of supplemental oxygen, ventilator settings, endotracheal tube (ETT) leak, diagnosis of chest tube air leak, provision of external gas support (i.e. nitric oxide), and provision of extracorporeal membrane oxygenation (ECMO).

RESULTS

288 patients were included for a total of 3590 patient days between June 2014 and February 2015. The main reasons for admission were: surgery (cardiac and non-cardiac), respiratory distress, trauma, oncology and medicine/other. The median (interquartile range) patient age was 0.7 (0.3-4.6) years. The median length of PICU stay was 7 (5-14) days. Only 34% (95% CI, 32.4-35.5%) of patient days met technical criteria for IC. For patients less than 6 months of age, technical criteria were met on significantly fewer patient days (29%, p < 0.01). Moreover, 27% of patients did not meet technical criteria for IC on any day during their PICU stay. Most frequent reasons for why IC could not be performed included supplemental oxygen, ECMO, and ETT leak.

CONCLUSIONS

In the current study, technical criteria to perform IC in the PICU were not met for 27% of patients and were not met on 66% of patient days. Moreover, criteria were met on only 29% of days for infants 6 months and younger where children 24 months of age and older still only met criteria on 40% of patient days. This data represents a major gap in the feasibility of current recommendations for assessing energy requirements of this population. Future studies are needed to improve methods of predicting and measuring energy requirements in critically ill children who do not meet current criteria for indirect calorimetry.

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.

Clinical Guide for the Use of Metabolic Carts: Indirect Calorimetry--No Longer the Orphan of Energy Estimation

Critically ill patients often require nutrition support, but accurately determining energy needs in these patients is difficult. Energy expenditure is affected by patient characteristics such as weight, height, age, and sex but is also influenced by factors such as body temperature, nutrition support, sepsis, sedation, and therapies. Using predictive equations to estimate energy needs is known to be inaccurate. Therefore, indirect calorimetry measurement is considered the gold standard to evaluate energy needs in clinical practice. This review defines the indications, limitations, and pitfalls of this technique and gives practice suggestions in various clinical situations.