A Single-Center Prospective Observational Study Comparing Resting Energy Expenditure in Different Phases of Critical Illness: Indirect Calorimetry Versus Predictive Equations

Nutrition considerations for patients with persistent critical illness: A narrative review

Critically ill patients experience high rates of malnutrition and significant muscle loss during their intensive care unit (ICU) admission, impacting recovery. Nutrition is likely to play an important role in mitigating the development and progression of malnutrition and muscle loss observed in ICU, yet definitive clinical trials of nutrition interventions in ICU have failed to show benefit. As improvements in the quality of medical care mean that sicker patients are able to survive the initial insult, combined with an aging and increasingly comorbid population, it is anticipated that ICU length of stay will continue to increase. This review aims to discuss nutrition considerations unique to critically ill patients who have persistent critical illness, defined as an ICU stay of >10 days. A discussion of nutrition concepts relevant to patients with persistent critical illness will include energy and protein metabolism, prescription, and delivery; monitoring of nutrition at the bedside; and the role of the healthcare team in optimizing nutrition support.

Association between protocol change to a higher-protein formula with lower energy targets and nutrient delivery in critically ill patients with COVID-19: A retrospective cohort study

BACKGROUND

Guidelines recommend prioritizing protein provision while avoiding excessive energy delivery to critically ill patients with coronavirus disease 2019 (COVID-19), but there are no prospective studies evaluating such a targeted approach in this group. We aimed to evaluate the effect of a "higher-protein formula protocol" on protein, energy, and volume delivery when compared with standard nutrition protocol.

METHODS

This was a retrospective cohort study of adult patients with COVID-19 who received mechanical ventilation for >72 h and enteral nutrition. Before October 2021, the standard nutrition protocol for patients was 0.7 ml/kg/h ideal body weight (IBW) of a 63 g/L protein and 1250 kcal/L formula. From October 2021, we implemented a higher-protein formula protocol for patients with COVID-19. The initial prescription was 0.5 ml/kg/h IBW of a 100 g/L protein and 1260 kcal/L formula with greater emphasis on energy targets being directed by indirect calorimetry when possible. Measured outcomes included protein, energy, and volume delivered.

RESULTS

There were 114 participants (standard protocol, 48; higher-protein protocol, 66) with 1324 days of nutrition support. The median (95% CI) differences in protein, energy, and volume delivery between targeted and standard protocol periods were 0.08 g/kg/day (-0.02 to 0.18 g/kg/day), -1.71 kcal/kg/day (-3.64 to 0.21 kcal/kg/day) and -1.5 ml/kg/day (-2.9 to -0.1 ml/kg/day). Thirty-three patients (standard protocol, 7; higher-protein protocol, 26) had 44 indirect calorimetry assessments. There was no difference in measured energy expenditure over time (increased by 0.49 kcal/kg/day [-0.89 to 1.88 kcal/kg/day]).

CONCLUSION

Implementation of a higher-protein formula protocol to patients with COVID-19 modestly reduced volume administration without impacting protein and energy delivery.

Decision tree model for early use of semi-elemental formula versus standard polymeric formula in critically ill Malaysian patients: A cost-effectiveness study

BACKGROUND

Prevention of enteral feeding interruption (EFI) improves clinical outcomes of critically ill intensive care unit (ICU) patients. This leads to shorter ICU stays and thereby lowers healthcare costs. This study compared the cost of early use of semi-elemental formula (SEF) in ICU vs standard polymeric formula (SPF) under the Ministry of Health (MOH) system in Malaysia.

METHODS

A decision tree model was developed based on literature and expert inputs. An epidemiological projection model was then added to the decision tree to calculate the target population size. The budget impact of adapting the different enteral nutrition (EN) formulas was calculated by multiplying the population size with the costs of the formula and ICU length of stay (LOS). A one-way sensitivity analysis (OWSA) was conducted to examine the effect each input parameter has on the calculated output.

RESULTS

Replacing SPF with SEF would lower ICU cost by MYR 1059 (USD 216) per patient. The additional cost of increased LOS due to EFI was MYR 5460 (USD 1114) per patient. If the MOH replaces SPF with SEF for ICU patients with high EFI risk (estimated 7981 patients in 2022), an annual net cost reduction of MYR 8.4 million (USD 1.7 million) could potentially be realized in the MOH system. The cost-reduction finding of replacing SPF with SEF remained unchanged despite the input uncertainties assessed via OWSA.

CONCLUSION

Early use of SEF in ICU patients with high EFI risk could potentially lower the cost of ICU care for the MOH system in Malaysia.

Comparison of predictive equations and indirect calorimetry in critical care: Does the accuracy differ by body mass index classification?

BACKGROUND

Nutrition support professionals are tasked with estimating energy requirements for critically ill patients. Estimating energy leads to suboptimal feeding practices and adverse outcomes. Indirect calorimetry (IC) is the gold standard for determining energy expenditure. However, access is limited, so clinicians must rely on predictive equations.

METHODS

A retrospective chart review of critically ill patients who underwent IC in 2019 was conducted. The Mifflin-St Jeor equation (MSJ), Penn State University equation (PSU), and weight-based nomograms were calculated using admission weights. Demographic, anthropometric, and IC data were extracted from the medical record. Data were stratified by body mass index (BMI) classifications, and relationships between estimated energy requirements and IC were compared.

RESULTS

Participants (N = 326) were included. Median age was 59.2 years, and BMI was 30.1. The MSJ and PSU were positively correlated with IC in all BMI classes (all P < 0.001). Median measured energy expenditure was 2004 kcal/day, which was 1.1-fold greater than PSU, 1.2-fold greater than MSJ, and 1.3-fold greater than weight-based nomograms (all P < 0.001).

CONCLUSION

Despite the significant relationships between measured and estimated energy requirements, the significant fold-differences suggest that using predictive equations leads to significant underfeeding, which may result in poor clinical outcomes. Clinicians should rely on IC when available, and increased training in the interpretation of IC is warranted. In the absence of IC, the use of admission weight in weight-based nomograms could serve as a surrogate, as these calculations provided the closest estimate to IC in participants with normal weight and overweight, but not obesity.

The Effects of Zinc and Selenium Co-Supplementation on Resting Metabolic Rate, Thyroid Function, Physical Fitness, and Functional Capacity in Overweight and Obese People under a Hypocaloric Diet: A Randomized, Double-Blind, and Placebo-Controlled Trial

Evidence of the effectiveness of zinc (Zn) and selenium (Se) on resting metabolic rate (RMR) and physical function parameters in people with overweight and obesity is scarce, while the effects of zinc and selenium on thyroid function and body composition are still a topic of debate and controversy. The aim of this randomized, double-blind, and placebo-controlled trial was to examine the effects of a hypocaloric diet and Se-Zn co-supplementation on RMR, thyroid function, body composition, physical fitness, and functional capacity in overweight or obese individuals. Twenty-eight overweight-obese participants (mean BMI: 29.4 ± 4.7) were randomly allocated (1:1) to the supplementation group (n = 14, 31.1 ± 5.5 yrs, 9 females) and the placebo group (n = 14, 32.1 ± 4.8 yrs, 6 females). The participants received Zn (25 mg of zinc gluconate/day) and Se (200 mcg of L-selenomethionine/day) or placebo tablets containing starch for eight weeks. The participants of both groups followed a hypocaloric diet during the intervention. RMR, thyroid function, body composition, cardiorespiratory fitness (VO₂max), and functional capacity (sit-to-stand tests, timed up-and-go test, and handgrip strength) were assessed before and after the intervention. A significant interaction was found between supplementation and time on RMR (p = 0.045), with the intervention group's RMR increasing from 1923 ± 440 to 2364 ± 410 kcal/day. On the other hand, no interaction between supplementation and time on the thyroid function was found (p > 0.05). Regarding the effects of Zn/Se co-administration on Se levels, a significant interaction between supplementation and time on Se levels was detected (p = 0.004). Specifically, the intervention group's Se serum levels were increased from 83.04 ± 13.59 to 119.40 ± 23.93 μg/L. However, Zn serum levels did not change over time (90.61 ± 23.23 to 89.58 ± 10.61 umol/L). Even though all body composition outcomes improved in the intervention group more than placebo at the second measurement, no supplement × time interaction was detected on body composition (p > 0.05). Cardiorespiratory fitness did not change over the intervention. Yet, a main effect of time was found for some functional capacity tests, with both groups improving similarly over the eight-week intervention period (p < 0.05). In contrast, a supplement x group interaction was found in the performance of the timed up-and-go test (TUG) (p = 0.010), with the supplementation group improving more. In conclusion, an eight-week intervention with Zn/Se co-supplementation combined with a hypocaloric diet increased the RMR, TUG performance, and Se levels in overweight and obese people. However, thyroid function, Zn levels, body composition, and the remaining outcomes of exercise performance remained unchanged.

How do guideline recommended energy targets compare with measured energy expenditure in critically ill adults with obesity: A systematic literature review

BACKGROUND

Critically ill patients with obesity have unique and complex nutritional needs, with clinical practice guidelines conflicting regarding recommended energy targets. The aim of this systematic review was to 1) describe measured resting energy expenditure (mREE) reported in the literature and; 2) compare mREE to predicted energy targets using the European (ESPEN) and American (ASPEN) guideline recommendations when indirect calorimetry is not available in critically ill patients with obesity.

METHODS

The protocol was registered apriori and literature was searched until 17th March, 2022. Original studies were included if they reported mREE using indirect calorimetry in critically ill patients with obesity (BMI≥30 kg/m²). Group-level mREE data was reported as per the primary publication using mean ± standard deviation or median [interquartile range]. Where individual patient data was available, Bland-Altman analysis was used to assess mean bias (95% limits of agreement) between guideline recommendations and mREE targets (i.e. ASPEN for BMI 30-50, 11-14 kcal/kg actual weight compared to 70% mREE and ESPEN 20-25 kcal/kg adjusted weight compared to 100% mREE). Accuracy was assessed by the percentage (%) of estimates within ±10% of mREE targets.

RESULTS

After searching 8019 articles, 24 studies were included. mREE ranged from 1607 ± 385 to 2919 [2318-3362]kcal and 12-32kcal/actual body weight. For the ASPEN recommendations of 11-14 kcal/kg, a mean bias of -18% (-50% to +13%) and 4% (-36% to +44%) was observed, respectively (n = 104). For the ESPEN recommendations 20-25 kcal/kg, a bias of -22% (-51% to +7%) and -4% (-43% to +34%), was observed, respectively (n = 114). The guideline recommendations were able to accurately predict mREE targets on 30%-39% occasions (11-14 kcal/kg actual) and 15%-45% occasions (20-25 kcal/kg adjusted), for ASPEN and ESPEN recommendations, respectively.

CONCLUSIONS

Measured energy expenditure in critically ill patients with obesity is variable. Energy targets generated using predictive equations recommended in both the ASPEN and ESPEN clinical guidelines have poor agreement with mREE and are frequently not able to accurately predict within ±10% of mREE, most commonly underestimating energy needs.

Resting Energy Expenditure in the Critically Ill and Healthy Elderly-A Retrospective Matched Cohort Study

The use of indirect calorimetry to measure resting energy expenditure (mREE) is widely recommended as opposed to calculating REE (cREE) by predictive equations (PE). The aim of this study was to compare mREE with cREE in critically ill, mechanically ventilated patients aged ≥ 75 years and a healthy control group matched by age, gender and body mass index. The primary outcome was the PE accuracy rate of mREE/cREE, derived using Bland Altman plots. Secondary analyses included linear regression analyses for determinants of intraindividual mREE/cREE differences in the critically ill and interindividual mREE differences in the matched healthy cohort. In this retrospective study, 90 critically ill patients (median age 80 years) and 58 matched healthy persons were included. Median mREE was significantly higher in the critically ill (1457 kcal/d) versus the healthy cohort (1351 kcal/d), with low PE accuracy rates (21% to 49%). Independent predictors of mREE/cREE differences in the critically ill were body temperature, heart rate, FiO₂, hematocrit, serum sodium and urea. Body temperature, respiratory rate, and FiO₂ were independent predictors of interindividual mREE differences (critically ill versus healthy control). In conclusion, the commonly used PE in the elderly critically ill are inaccurate. Respiratory, metabolic and energy homeostasis variables may explain intraindividual mREE/cREE as well as interindividual mREE differences.

Nutrition therapy in the older critically ill patients: A scoping review

Introduction: There is a lack of guidelines or formal systematic synthesis of evidence for nutrition therapy in older critically ill patients. This study is a scoping review to explore the state of evidence in this population. Method: MEDLINE and Embase were searched from inception until 9 February 2022 for studies that enrolled critically ill patients aged ≥60 years and investigated any area of nutrition therapy. No language or study design restrictions were applied. Results: Thirty-two studies (5 randomised controlled trials) with 6 topics were identified: (1) nutrition screening and assessments, (2) muscle mass assessment, (3) route or timing of nutrition therapy, (4) determination of energy and protein requirements, (5) energy and protein intake, and (6) pharmaconutrition. Topics (1), (3) and (6) had similar findings among general adult intensive care unit (ICU) patients. Skeletal muscle mass at ICU admission was significantly lower in older versus young patients. Among older ICU patients, low muscularity at ICU admission increased the risk of adverse outcomes. Predicted energy requirements using weight-based equations significantly deviated from indirect calorimetry measurements in older vs younger patients. Older ICU patients required higher protein intake (>1.5g/kg/day) than younger patients to achieve nitrogen balance. However, at similar protein intake, older patients had a higher risk of azotaemia. Conclusion: Based on limited evidence, assessment of muscle mass, indirect calorimetry and careful monitoring of urea level may be important to guide nutrition therapy in older ICU patients. Other nutrition recommendations for general ICU patients may be used for older patients with sound clinical discretion. Keywords: Critical care nutrition, geriatric patients, intensive care medicine, older adults, scoping review

Association between caloric adequacy and short-term clinical outcomes in critically ill patients using a weight-based equation: Secondary analysis of a cluster-randomized controlled trial

Background

There is controversy over the optimal energy delivery in intensive care units (ICUs). In this study, we aimed to evaluate the association between different caloric adequacy assessed by a weight-based equation and short-term clinical outcomes in a cohort of critically ill patients.

Methods

This is a secondary analysis of a cluster-randomized controlled trial (N = 2,772). The energy requirement was estimated as 25 kcal/kg of body weight. The study subjects were divided into three groups according to their caloric adequacy as calculated by the mean energy delivered from days 3 to 7 of enrollment divided by the estimated energy requirements: (1) received &lt; 70% of energy requirement (hypocaloric), (2) received 70–100% of energy requirement (normocaloric), and (3) received &gt; 100% of energy requirement (hypercaloric). Cox proportional hazards models were used to analyze the association between caloric adequacy and 28-day mortality and time to discharge alive from the ICU.

Results

A total of 1,694 patients were included. Compared with normocaloric feeding, hypocaloric feeding significantly increased the risk of 28-day mortality (hazard ratio [HR] = 1.590, 95% confidence interval [CI]: 1.162–2.176, p = 0.004), while hypercaloric feeding did not. After controlling for potential confounders, the association remained valid (adjusted HR = 1.596, 95% CI: 1.150–2.215, p = 0.005). The caloric adequacy was not associated with time to discharge alive from the ICU in the unadjusted and the adjusted models.

Conclusion

Energy delivery below 70% of the estimated energy requirement during days 3–7 of critical illness is associated with 28-day mortality.

Clinical trial registration

[https://www.isrctn.com/ISRCTN12233792], identifier [ISRCTN12233792].

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

ClinicalTrials.gov NCT03319329.

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.