New generation indirect calorimeters for measuring energy expenditure in the critically ill: a rampant or reticent revolution?

Comparison of resting energy expenditure measured with metabolic cart and calculated with predictive formulas in critically ill patients on mechanical ventilation

INTRODUCTION

The purpose was to compare the resting energy expenditure (REE) measured with the Q-NRG™+ metabolic-cart (MREE) with REE predicted by equations (the Harris-Benedict formula and an equation developed in ward, REE-HB and REE-W, respectively). We also aimed to assess the agreement of the measurements of oxygen consumption (V̇O₂) and carbon dioxide production (V̇CO₂) at different inspired fractions of oxygen (FiO₂).

METHODS

27 mechanically ventilated ICU patients were enrolled. V̇O₂ and V̇CO₂ were measured by Q-NRG™+ during breathing 40% and 60% FiO₂. MREE was compared with REE-W and REE-HB normalized for body weight.

RESULTS

V̇O₂ was 233.0 (95.2) ml/min and 217.5 (89.8) ml/min at FiO₂ 40% and 60%, respectively (NS). V̇CO₂ was 199.0 (91.7) ml/min at FiO₂ 40%, and 197.5 (85.5) ml/min at FiO₂ 60% (NS). The REE estimated from the equations was significantly different from the MREE. The best agreement was found for the Harris-Benedict equation without correction for stress-factors. Harris-Benedict equation corrected overestimates REE.

CONCLUSIONS

This new metabolic cart Q-NRG™+ provides a concordance of values for V̇O₂ and V̇CO₂ when measured at different FiO₂, and is a reliable tool for estimating energy expenditure and assessing the nutritional needs of the patient. This study demonstrates that the estimation of REE using predictive formulas does not allow accurate calculation of metabolic demands in ventilated intensive care patient. However, predictive equations allow for a rapid assessment of REE and calculation of the amount of energy derived from different substrates.

Blood gas analysis as a surrogate for microhemodynamic monitoring in sepsis

BACKGROUND

Emergency patients with sepsis or septic shock are at high risk of death. Despite increasing attention to microhemodynamics, the clinical use of advanced microcirculatory assessment is limited due to its shortcomings. Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption, it may serve as a surrogate for microcirculation monitoring in septic treatment.

METHODS

We performed a search using PubMed, Web of Science, and Google scholar. The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.

RESULTS

Based on the pathophysiology of oxygen metabolism, the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care. Notwithstanding flaws, several parameters are linked to changes in the microcirculation. A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.

CONCLUSION

Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments. A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.

Measured Energy Expenditure Using Indirect Calorimetry in Post-Intensive Care Unit Hospitalized Survivors: A Comparison with Predictive Equations

Actual energy needs after a stay in intensive care units (ICUs) are unknown. The aims of this observational study were to measure the energy expenditure (mEE) of ICU survivors during their post-ICU hospitalization period, and to compare this to the estimations of predictive equations (eEE). Survivors of an ICU stay ≥ 7 days were enrolled in the general ward during the first 7 days after ICU discharge. EE was measured using the Q-NRG calorimeter in canopy mode. This measure was compared to the estimated EE using the Harris−Benedict (HB) equation multiplied by a 1.3 stress factor, the Penn−State (PS) equation or the 30 kcal weight-based (WB) equation. A total of 55 adults were included (67.3% male, age 60 (52−67) y, body mass index 26.1 (22.2−29.7) kg/m2). Indirect calorimetry was performed 4 (3−6) d after an ICU stay of 12 (7−16) d. The mEE was 1682 (1328−1975) kcal/d, corresponding to 22.9 (19.1−24.2) kcal/kg/day. The eEE values derived using HB and WB equations were significantly higher than mEE: 3048 (1805−3332) and 2220 (1890−2640) kcal/d, respectively (both p < 0.001). There was no significant difference between mEE and eEE using the PS equation: 1589 (1443−1809) kcal/d (p = 0.145). The PS equation tended to underestimate mEE with a bias of −61.88 kcal and a wide 95% limit of agreement (−717.8 to 594 kcal). Using the PS equation, agreement within 15% of the mEE was found in 32/55 (58.2%) of the patients. In the present cohort of patients who survived a prolonged ICU stay, mEE was around 22−23 kcal/kg/day. In this post-ICU hospitalization context, none of the tested equations were accurate in predicting the EE measured by indirect calorimetry.

Respiratory Support Adjustments and Monitoring of Mechanically Ventilated Patients Performing Early Mobilization: A Scoping Review

Supplemental Digital Content is available in the text.

Objectives:

This scoping review is aimed to summarize current knowledge on respiratory support adjustments and monitoring of metabolic and respiratory variables in mechanically ventilated adult patients performing early mobilization.

Data Sources:

Eight electronic databases were searched from inception to February 2021, using a predefined search strategy.

Study Selection:

Two blinded reviewers performed document selection by title, abstract, and full text according to the following criteria: mechanically ventilated adult patients performing any mobilization intervention, respiratory support adjustments, and/or monitoring of metabolic/respiratory real-time variables.

Data Extraction:

Four physiotherapists extracted relevant information using a prespecified template.

Data Synthesis:

From 1,208 references screened, 35 documents were selected for analysis, where 20 (57%) were published between 2016 and 2020. Respiratory support settings (ventilatory modes or respiratory variables) were reported in 21 documents (60%). Reported modes were assisted (n = 11) and assist-control (n = 9). Adjustment of variables and modes were identified in only seven documents (20%). The most frequent respiratory variable was the Fio₂, and only four studies modified the level of ventilatory support. Mechanical ventilator brand/model used was not specified in 26 documents (74%). Monitoring of respiratory, metabolic, and both variables were reported in 22 documents (63%), four documents (11%) and 10 documents (29%), respectively. These variables were reported to assess the physiologic response (n = 21) or safety (n = 13). Monitored variables were mostly respiratory rate (n = 26), pulse oximetry (n = 22), and oxygen consumption (n = 9). Remarkably, no study assessed the work of breathing or effort during mobilization.

Conclusions:

Little information on respiratory support adjustments during mobilization of mechanically ventilated patients was identified. Monitoring of metabolic and respiratory variables is also scant. More studies on the effects of adjustments of the level/mode of ventilatory support on exercise performance and respiratory muscle activity monitoring for safe and efficient implementation of early mobilization in mechanically ventilated patients are needed.

The clinical relevance and mechanism of skeletal muscle wasting

Skeletal muscle wasting occurs in both chronic and acute diseases. Increasing evidence has shown this debilitating process is associated with short- and long-term outcomes in critical, cancer and surgical patients. Both muscle quantity and quality, as reflected by the area and density of a given range of attenuation in CT scan, impact the patient prognosis. In addition, ultrasound and bioelectrical impedance analysis (BIA) are also widely used in the assessment of body composition due to their bedside viability and no radioactivity. Mechanism researches have revealed complicated pathways are involved in muscle wasting, which include altered IGF1-Akt-FoxO signaling, elevated levels of myostatin and activin A, activation of NF-κB pathway and glucocorticoid effects. Particularly, central nervous system (CNS) has been proven to participate in regulating muscle wasting in various conditions, such as infection and tumor. Several promising therapeutic agents have been under developing in the treatment of muscle atrophy, such as myostatin antagonist, ghrelin analog, non-steroidal selective androgen receptor modulators (SARMs). Notably, nutritional therapy is still the fundamental support in combating muscle wasting. However, the optimizing and tailored nutrition regimen relies on accurate metabolism measurement and large clinical trials in the future. Here, we will discuss the current understanding of muscle wasting and potential treatment in clinical practice.

A novel prediction equation of resting energy expenditure for Japanese septic patients

Estimating nutrient consumption and administering appropriate nutritional therapy is essential for improving clinical outcomes in critically ill patients. Various equations, such as the Harris-Benedict equation, have been developed to estimate the required calories. Previous equations, however, targeted Westerners, whose physical characteristics are likely different from those of Asians. Hence, it is unclear whether these equations can be used for Asian patients. This study focused specifically on sepsis patients admitted to a single Japanese ICU, and aimed to develop novel equations to estimate their total energy expenditure. A total of 95 sepsis patients were included in this study. We measured resting energy expenditure (REE) by using indirect calorimetry, and created equations to calculate basal metabolic rate (BMR) using height, weight and age as variables. REE was predicted by multiplying BMR by the novel equation with the stress factor of 1.4. The prediction error of our novel equations were smaller than those of other conventional equations. We further confirmed the accuracy of our equations and that they were unaffected by patient age and disease severity by using data obtained from another patient group. The current study suggested that these equations might allow accurate estimation of the total energy expenditure and proper management of nutritional therapy in Asian sepsis patients.

Does the use of indirect calorimetry change outcome in the ICU? Yes it does

PURPOSE OF REVIEW

To review the recent findings on metabolic monitoring and possible beneficial effects of an adequate nutrition therapy, based on indirect calorimetry as the golden standard to predict energy expenditure.

RECENT FINDINGS

in the last decades, major steps are taken in the field of metabolism and nutrition, evolving from nutrition as a baseline support to a therapeutic intervention. The aspect of energy expenditure is of cardinal importance, and technical possibilities have impressively improved: from the first 'calorimetre' in 1789 to the new generation, clinical applicable indirect calorimeters and the high accuracy and easy use model reaching high technology readiness level [Oshima et al. (2017). Clin Nutr 36:651]. Several recent studies provide information on the technique of metabolic monitoring itself and the positive effects of implementation of the tool in a high-end nutritional care plan [Oshima et al. (2017). Clin Nutr 36:651]. The combination of correct energy provision and protein prescription has shown benefits, and mortality of ICU patients is related to the amount of energy provided [Zusman et al. (2016). Crit Care 20:367]. The use of a monitor per se will not change outcome. Optimal dosing of artificial nutrition can be achieved by the use of a parameter acquired by a measurement instead of by inaccurate equations. In the era of precision medicine, this approach has shown positive effects on outcome. Moreover, above all, the concept of metabolic monitoring of the critically ill is just an issue of common sense.

SUMMARY

Metabolic monitoring by indirect calorimetry is achieving a level in which it can be implemented in critical care practice. Evidence is available to prove that by guiding your nutritional therapy by measured values, it will change outcome of critically ill patients.

Muscle mass and physical recovery in ICU: innovations for targeting of nutrition and exercise

PURPOSE OF REVIEW

We have significantly improved hospital mortality from sepsis and critical illness in last 10 years; however, over this same period we have tripled the number of 'ICU survivors' going to rehabilitation. Furthermore, as up to half the deaths in the first year following ICU admission occur post-ICU discharge, it is unclear how many of these patients ever returned home or a meaningful quality of life. For those who do survive, recent data reveals many 'ICU survivors' will suffer significant functional impairment or post-ICU syndrome (PICS). Thus, new innovative metabolic and exercise interventions to address PICS are urgently needed. These should focus on optimal nutrition and lean body mass (LBM) assessment, targeted nutrition delivery, anabolic/anticatabolic strategies, and utilization of personalized exercise intervention techniques, such as utilized by elite athletes to optimize preparation and recovery from critical care.

RECENT FINDINGS

New data for novel LBM analysis technique such as computerized tomography scan and ultrasound analysis of LBM are available showing objective measures of LBM now becoming more practical for predicting metabolic reserve and effectiveness of nutrition/exercise interventions. 13C-Breath testing is a novel technique under study to predict infection earlier and predict over-feeding and under-feeding to target nutrition delivery. New technologies utilized routinely by athletes such as muscle glycogen ultrasound also show promise. Finally, the role of personalized cardiopulmonary exercise testing to target preoperative exercise optimization and post-ICU recovery are becoming reality.

SUMMARY

New innovative techniques are demonstrating promise to target recovery from PICS utilizing a combination of objective LBM and metabolic assessment, targeted nutrition interventions, personalized exercise interventions for prehabilitation and post-ICU recovery. These interventions should provide hope that we will soon begin to create more 'survivors' and fewer victim's post-ICU care.

Nutrition Therapy in Sepsis

Sepsis is characterized by early massive catabolism, lean body mass (LBM) loss, and escalating hypermetabolism persisting for months to years. Early enteral nutrition should attempt to correct micronutrient/vitamin deficiencies, deliver adequate protein and moderated nonprotein calories, as well-nourished patients can generate reasonable endogenous energy. After resuscitation, increasing protein/calories are needed to attenuate LBM loss and promote recovery. Malnutrition screening is essential, and parenteral nutrition can be safely added when enteral nutrition is failing based on preillness malnutrition. Following discharge from intensive care unit, significantly increased protein/calorie delivery is required for months to years to facilitate functional and LBM recovery.