Energy expenditure and caloric balance after burn: increased feeding leads to fat rather than lean mass accretion

HOUSING TEMPERATURE ALTERS BURN-INDUCED HYPERMETABOLISM IN MICE

ABSTRACT

Mice used in biomedical research are typically housed at ambient temperatures (22°C-24°C) below thermoneutrality (26°C-31°C). This chronic cold stress triggers a hypermetabolic response that may limit the utility of mice in modeling hypermetabolism in response to burns. To evaluate the effect of housing temperature on burn-induced hypermetabolism, mice were randomly assigned to receive sham, small, or large scald burns. Mice recovered for 21 days in metabolic phenotyping cages at 24°C or 30°C. Regardless of sex or sham/burn treatment, mice housed at 24°C had greater total energy expenditure ( P < 0.001), which was largely attributable to greater basal energy expenditure when compared to mice housed at 30°C ( P < 0.001). Thermoneutral housing (30°C) altered adipose tissue mass in a sex-dependent manner. Compared to sham and small burn groups, large burns resulted in greater water vapor loss, regardless of housing temperature ( P < 0.01). Compared to sham, large burns resulted in greater basal energy expenditure and total energy expenditure in mice housed at 24°C; however, this hypermetabolic response to large burns was blunted in female mice housed at 30°C, and absent in male mice housed at 30°C. Locomotion was significantly reduced in mice with large burns compared to sham and small burn groups, irrespective of sex or housing temperature ( P < 0.05). Housing at 30°C revealed sexual dimorphism in terms of the impact of burns on body mass and composition, where males with large burns displayed marked cachexia, whereas females did not. Collectively, this study demonstrates a sex-dependent role for housing temperature in influencing energetics and body composition in a rodent model of burn trauma.

Large area fractional laser treatment of mouse skin increases energy expenditure

Fractional laser (FL) treatment is a common dermatologic procedure that generates arrays of microscopic treatment zones separated by intact tissue, promoting fast wound healing. Using a mouse model, we introduced a large area fractional laser treatment (LAFLT) method to study metabolic effects. Using two laser modalities, ablative FL (AFL) and non-ablative FL (NAFL), and exposing different percentages of mice's total body surface area (TBSA), we followed changes in metabolic parameters in real time using metabolic cages. Additionally, body composition, markers of inflammation, neurohormonal signaling, and browning of adipocytes were investigated. LAFLT, especially in high TBSA groups, had specific metabolic effects such as significantly increased average daily energy expenditure, increased fat mass loss, systemic browning of adipocytes, and inflammatory states, without compromising other organs. The ability of LAFLT to stimulate metabolism in a controlled way could develop into a promising therapeutic treatment to induce positive metabolic changes that replace or augment systemic drugs.

Burn Patient Metabolism and Nutrition

Following severe burns, patients have unique metabolic derangements that make adequate nutritional support imperative for their survival and recovery. Patients with burns have persistent and prolonged hypermetabolic states that lead to increased catabolism following injury. During rehabilitation, catabolism leads to increased muscle wasting and cachexia. Failure to adequately meet the patient's increased nutritional requirements can lead to poor wound healing, increased infections, and overall organ dysfunction. Because of these risks, adequate assessment and provision of nutritional needs are imperative to care for these patients.

Nutrition Considerations for Burn Patients: Optimizing Recovery and Healing

The hypermetabolic and hypercatabolic responses to severe burns put nutrition support at the forefront of treatments. When left untreated, severe weight loss, increased infection, and wound healing failure can occur. Enteral nutrition is the primary method of nutrition support in such patients. Meeting caloric needs and a positive nitrogen balance are short-term goals of nutrition support, with long-term goals of minimizing lean body mass loss and maximizing wound healing. High-carbohydrate and low-fat nutrition received evidence from randomized controlled trials of aiding in decreasing pneumonia rates and was found to promote positive nitrogen balance, which lipids do not do. We go through the macronutrient and micronutrient needs of the burn patient as well as techniques for meeting these needs in the modern intensive care unit, with some discussion of alterations in these techniques that are required in the austere environment.

Metabolic and Nutritional Support

Hypermetabolism is a hallmark of larger burn injuries. The hypermetabolic response is characterized by marked and sustained increases in catecholamines, glucocorticoids, and glucagon. There is an increasing body of literature for nutrition and metabolic treatment and supplementation to counter the hypermetabolic and catabolic response secondary to burn injury. Early and adequate nutrition is key in addition to adjunctive therapies, such as oxandrolone, insulin, metformin, and propranolol. The duration of administration of anabolic agents should be at minimum for the duration of hospitalization, and possibly up to 2 to 3 years postburn.

Adjusting body weight for edema in severely burned patients

Weight loss is difficult to quantify in critically ill burn patients, as the presence of edema can mask changes in dry body weight. We sought to estimate dry body weight using measured weights adjusted for reported extremity edema. We evaluated patients with at least 20% total body surface area (TBSA) burns admitted to our intensive care unit over a 3½-year period. Body weights were collected for this analysis from admission to the time of a recorded dry weight after wound healing. Extremity edema was collected at the time of each weight measurement and was categorized into three groups: (1) no edema, (2) 1 + pitting edema, (3) 2 + or 3 + pitting edema. Logistic regression yielded the following formula for estimating dry weight (in kg): 0.66 x measured body weight + 25 - (3 for 1 + pitting edema or 4 for 2 + or 3 + pitting edema of either upper extremity) - (4 for any pitting edema to either lower extremity) (p < 0.01, R2 = 0.81). These results may allow us to better estimate dry body weight changes in our edematous patients with severe burns. Nutrition goals can be adjusted earlier, when appropriate, based on these estimated dry body weight changes.

The role of nutrition rehabilitation in the recovery of survivors of critical illness: underrecognized and underappreciated

Many survivors of critical illness face significant physical and psychological disability following discharge from the intensive care unit (ICU). They are often malnourished, a condition associated with poor outcomes, and nutrition remains problematic particularly in the early phases of ICU recovery. Yet nutrition rehabilitation, the process of restoring or optimizing nutritional status following illness, is seldom prioritized, possibly because it is an underrecognized and underappreciated area in critical care rehabilitation and research. To date, 16 original studies have been published where one of the objectives includes measurement of indices relating to nutritional status (e.g., nutrition intake or factors impacting nutrition intake) in ICU survivors. The primary aim of this narrative review is to provide a comprehensive summary of key themes arising from these studies which form the basis of our current understanding of nutritional recovery and rehabilitation in ICU survivors. ICU survivors face a multitude of barriers in achieving optimal nutrition that are of physiological (e.g., poor appetite and early satiety), functional (e.g., dysphagia, reduced ability to feed independently), and psychological (e.g., low mood, body dysmorphia) origins. Organizational-related barriers such as inappropriate feeding times and meal interruptions frequently impact an ICU survivor’s ability to eat. Healthcare providers working on wards frequently lack knowledge of the specific needs of recovering critically ill patients which can negatively impact post-ICU nutrition care. Unsurprisingly, nutrition intake is largely inadequate following ICU discharge, with the largest deficits occurring in those who have had enteral nutrition prematurely discontinued and rely on an oral diet as their only source of nutrition. With consideration to themes arising from this review, pragmatic strategies to improve nutrition rehabilitation are explored and directions for future research in the field of post-ICU nutrition recovery and rehabilitation are discussed. Given the interplay between nutrition and physical and psychological health, it is imperative that enhancing the nutritional status of an ICU survivor is considered when developing multidisciplinary rehabilitation strategies. It must also be recognized that dietitians are experts in the field of nutrition and should be included in stakeholder meetings that aim to enhance ICU rehabilitation strategies and improve outcomes for survivors of critical illness.

Effects of Different Ratios of Carbohydrate-Fat in Enteral Nutrition on Metabolic Pattern and Organ Damage in Burned Rats

(1) Background: Nutritional support is one of the most important cornerstones in the management of patients with severe burns, but the carbohydrate-to-fat ratios in burn nutrition therapy remain highly controversial. In this study, we aimed to discuss the effects of different ratios of carbohydrate–fat through enteral nutrition on the metabolic changes and organ damage in burned rats. (2) Methods: Twenty-four burned rats were randomly divided into 5%, 10%, 20% and 30% fat nutritional groups. REE and body weight were measured individually for each rat daily. Then, 75% of REE was given in the first week after burns, and the full dose was given in the second week. Glucose tolerance of the rats was measured on days 1, 3, 7, 10 and 14. Blood biochemistry analysis and organ damage analysis were performed after 7 and 14 days of nutritional therapy, and nuclear magnetic resonance (NMR) and insulin content analysis were performed after 14 days. (3) Results: NMR spectra showed significant differences of glucose, lipid and amino acid metabolic pathways. The energy expenditure increased, and body weight decreased significantly after burn injury, with larger change in the 20%, 5% and 30% fat groups, and minimal change in the 10% fat group. The obvious changes in the level of plasma protein, glucose, lipids and insulin, as well as the organ damage, were in the 30%, 20% and 5% fat groups. In relative terms, the 10% fat group showed the least variation and was closest to normal group. (4) Conclusion: Lower fat intake is beneficial to maintaining metabolic stability and lessening organ damage after burns, but percentage of fat supply should not be less than 10% in burned rats.

Assessing calorie and protein recommendations for survivors of critical illness weaning from prolonged mechanical ventilation - can we find a proper balance?

Background & aims:

Survivors of critical illness requiring prolonged mechanical ventilation (PMV) are predisposed to malnutrition, muscle wasting, and weakness. There is a lack of data regarding nutrition adequacy among these patients, and although nitrogen balance has been studied as a marker of adequate protein intake in healthy individuals and acutely critically ill patients, it has not been well studied in critically ill patients with PMV. The purpose of this study was to determine if patients requiring PMV admitted to a long-term acute care hospital (LTACH) achieved registered dietitian (RD) recommended goals for energy and protein intake and if the recommendations were adequate to avoid negative nitrogen balance.

Methods:

Using a retrospective, cohort study design, patients requiring PMV who had orders for 24-h urine collections for urea nitrogen (24hrUUN) were included. Energy and protein intake was calculated from chart documentation of dietary intake for the 24-h period during which patients underwent a 24hrUUN. Nitrogen intake was estimated from protein intake. Dietary intake was compared to RD-recommendations to determine the percentage of RD-recommendations achieved. Nitrogen balance was calculated as nitrogen intake minus nitrogen loss, with negative balance categorized as less than −1.

Results:

Subjects (n = 16) were 38% male and 75% African American (mean age 61.5 ± 3.2 years; mean BMI 27.5 ± 2.5 kg/m²). Duration of LTACH hospitalization was 26.5 (6–221) days. Mean energy and protein intake was 21.7 ± 2.9 kcal/kg/d and 1.1 ± 0.1 g/kg/d, respectively, which corresponded to 86% of both RD energy and protein recommendations. Ten patients achieved a positive nitrogen balance (mean 0.9 ± 1.1 g). In addition, there was a positive linear relationship between protein intake and nitrogen balance (r = 0.59, p = 0.016).

Conclusion:

Survivors of critical illness requiring PMV achieved a high percentage of RD-recommended protein and calories, and prevented a negative nitrogen balance in a majority of patients. Increasing protein intake can prevent a negative nitrogen balance. Future studies should evaluate whether these patients are able to maintain a steady state of nitrogen intake and excretion over time and how this affects time to and/or success of weaning.

Role of anabolic testosterone agents and structured exercise to promote recovery in ICU survivors

PURPOSE OF REVIEW

ICU survivors frequently suffer significant, prolonged physical disability. 'ICU Survivorship', or addressing quality-of-life impairments post-ICU care, is a defining challenge, and existing standards of care fail to successfully address these disabilities. We suggest addressing persistent catabolism by treatment with testosterone analogues combined with structured exercise is a promising novel intervention to improve 'ICU Survivorship'.

RECENT FINDINGS

One explanation for lack of success in addressing post-ICU physical disability is most ICU patients exhibit severe testosterone deficiencies early in ICU that drives persistent catabolism despite rehabilitation efforts. Oxandrolone is an FDA-approved testosterone analogue for treating muscle weakness in ICU patients. A growing number of trials with this agent combined with structured exercise show clinical benefit, including improved physical function and safety in burns and other catabolic states. However, no trials of oxandrolone/testosterone and exercise in nonburn ICU populations have been conducted.

SUMMARY

Critical illness leads to a catabolic state, including severe testosterone deficiency that persists throughout hospital stay, and results in persistent muscle weakness and physical dysfunction. The combination of an anabolic agent with adequate nutrition and structured exercise is likely essential to optimize muscle mass/strength and physical function in ICU survivors. Further research in ICU populations is needed.

Status of adult inpatient burn rehabilitation in Europe: Are we neglecting metabolic outcomes?

BACKGROUND

Hypermetabolism, muscle wasting and insulin resistance are challenging yet important rehabilitation targets in the management of burns. In the absence of concrete practice guidelines, however, it remains unclear how these metabolic targets are currently managed. This study aimed to describe the current practice of inpatient rehabilitation across Europe.

METHODS

An electronic survey was distributed by the European Burn Association to burn centres throughout Europe, comprising generic and profession-specific questions directed at therapists, medical doctors and dieticians. Questions concerned exercise prescription, metabolic management and treatment priorities, motivation and knowledge of burn-induced metabolic sequelae. Odds ratios were computed to analyse associations between data derived from the responses of treatment priorities and knowledge of burn-induced metabolic sequelae.

RESULTS

Fifty-nine clinicians with 12.3 ± 9 years of professional experience in burns, representing 18 out of 91 burn centres (response rate, 19.8%) across eight European countries responded. Resistance and aerobic exercises were only provided by 42% and 38% of therapists to intubated patients, 87% and 65% once out-of-bed mobility was possible and 97% and 83% once patients were able to leave their hospital room, respectively. The assessment of resting energy expenditure by indirect calorimetry, muscle wasting and insulin resistance was carried out by only 40.7%, 15.3% and 7.4% respondents, respectively, with large variability in employed frequency and methods. Not all clinicians changed their care in cases of hypermetabolism (59.3%), muscle wasting (70.4%) or insulin resistance (44.4%), and large variations in management strategies were reported. Significant interdisciplinary variation was present in treatment goal importance ratings, motivation and knowledge of burn-induced metabolic sequelae. The prevention of metabolic sequelae was regarded as the least important treatment goal, while the restoration of functional status was rated as the most important. Knowledge of burn-induced metabolic sequelae was linked to higher importance ratings of metabolic sequelae as a therapy goal (odds ratio, 4.63; 95% CI, 1.50-14.25; p < 0.01).

CONCLUSION

This survey reveals considerable non-uniformity around multiple aspects of inpatient rehabilitation across European burn care, including, most notably, a potential neglect of metabolic outcomes. The results contribute to the necessary groundwork to formulate practice guidelines for inpatient burn rehabilitation.

White adipose tissue browning in critical illness: A review of the evidence, mechanisms and future perspectives

Observational studies suggest better clinical outcomes following critical illness in patients with overweight and obesity (obesity paradox). An understanding of the morphologic, physiologic and metabolic changes in adipose tissue in critical illness may provide an explanation. Recent studies have demonstrated the transformation of white to brown-like adipocytes due to the "browning process," which has been of interest as a potential novel therapy in obesity during the last decade. The characteristics of the browning of white adipose tissue (WAT) include the appearance of smaller, multilocular adipocytes, increased UCP1 mRNA expression, mitochondrial density and respiratory capacity. These changes have been identified in some critical illnesses, which specifically refers to burns, sepsis and cancer cachexia in this study. The pathophysiological nature of WAT browning, underlying mechanisms, main regulators and potential benefits and harms of this process are interesting new areas that warrants further investigations. In this review, we discuss emerging scientific discipline of adipose tissue physiology in metabolic stress, available data, gaps of knowledge and future perspectives. Future investigations in this field may provide insights into the underlying mechanisms and clinical aspects of browning that may further our understanding of the proposed obesity paradox following critical illness, which may in turn open up opportunities for novel therapies to save lives and improve recovery.

Protein Requirements during Hypocaloric Nutrition for the Older Patient With Critical Illness and Obesity: An Approach to Clinical Practice

Current guidelines recommend a hypocaloric, high protein nutrition regimen for patients with obesity and critical illness. The impact of advancing age presents with unique challenges in which a greater protein intake is required to overcome the anabolic resistance associated with aging in the face of presumed decreased renal function. The primary objective of this review is to provide an overview of the impact of obesity and advancing age on protein requirements for patients with critical illness and review the scientific evidence supporting the rationale for hypocaloric, high protein nutrition for this subpopulation, as well as provide some practical suggestions for their clinical management.

Cardiac Structure and Function in Well-Healed Burn Survivors

Long-term burn survivors have reduced aerobic capacity, placing them at increased risk for cardiovascular disease, morbidity, and mortality. However, the exact mechanism contributing to a reduced aerobic capacity remains incompletely understood, but may be related to adverse cardiovascular remodeling. Therefore, it was hypothesized that well-healed burn survivors would exhibit adverse left ventricular (LV) remodeling and impaired LV function. To test this hypothesis, 22 well-healed moderately burned individuals (age: 41 ± 14 years; BMI: 27.7 ± 5.4 kg/m2; male/female: 12/10; extent of burn: 37 ± 12 %BSA), 11 well-healed severely burned individuals (age: 43 ± 12 years; BMI: 29.5 ± 5.8 kg/m2; male/female: 8/3; extent of burn: 73 ± 11 %BSA), and 12 healthy, age-matched controls (age: 34 ± 9 years; BMI: 28.6 ± 5.2 kg/m2; male/female: 5/7) were enrolled in the study. All subjects were sedentary, performing less than 30 minutes of aerobic exercise per day, 3 days per week. LV morphology and function were assessed via cardiac magnetic resonance imaging. In contrast to the hypothesis, neither the presence nor severity of burn injury adversely affected LV morphology or function, when compared with equally sedentary nonburned controls. However, of note, LV mass of all three groups was in the lowest 5th percentile compared with normative values. Finally, group differences in LV morphology were largely explained by differences in aerobic capacity. Taken together, these data suggest a prior burn injury itself does not result in pathological remodeling of the LV and support a role for aerobic exercise training to improve cardiac function.

Geometric framework reveals that a moderate protein, high carbohydrate intake is optimal for severe burn injury in mice

Nutritional therapy is a cornerstone of burns management. The optimal macronutrient intake for wound healing after burn injury has not been identified, although high-energy, high-protein diets are favoured. The present study aimed to identify the optimal macronutrient intake for burn wound healing. The geometric framework (GF) was used to analyse wound healing after a 10 % total body surface area contact burn in mice ad libitum fed one of the eleven high-energy diets, varying in macronutrient composition with protein (P5-60 %), carbohydrate (C20-75 %) and fat (F20-75 %). In the GF study, the optimal ratio for wound healing was identified as a moderate-protein, high-carbohydrate diet with a protein:carbohydrate:fat (P:C:F) ratio of 1:4:2. High carbohydrate intake was associated with lower mortality, improved body weight and a beneficial pattern of body fat reserves. Protein intake was essential to prevent weight loss and mortality, but a protein intake target of about 7 kJ/d (about 15 % of energy intake) was identified, above which no further benefit was gained. High protein intake was associated with delayed wound healing and increased liver and spleen weight. As the GF study demonstrated that an initial very high protein intake prevented mortality, a very high-protein, moderate-carbohydrate diet (P40:C42:F18) was specifically designed. The dynamic diet study was also designed to combine and validate the benefits of an initial very high protein intake for mortality, and subsequent moderate protein, high carbohydrate intake for optimal wound healing. The dynamic feeding experiment showed switching from an initial very high-protein diet to the optimal moderate-protein, high-carbohydrate diet accelerated wound healing whilst preventing mortality and liver enlargement.

Randomized Controlled Trial of Comparative Hypocaloric vs Full-Energy Enteral Feeding During the First Week of Hospitalization in Neurosurgical Patients at the Intensive Care Unit

BACKGROUND

Nutrition support plays a pivotal role in improving the clinical outcomes of the patients admitted to the intensive care unit (ICU). However, there are controversies regarding the optimal amount of energy for the reduction of morbidity and mortality in neurosurgical patients at the ICU.

METHODS

This randomized clinical trial was conducted on 560 patients who were admitted to trauma, stroke, and neurosurgery ICUs, and 68 patients were enrolled based on the inclusion criteria. In total, data of 58 patients were analyzed. In the full-energy group, enteral feeding started at 75% of their daily energy expenditure and gradually increased to 90%-100%. In the hypocaloric group, enteral feeding started with 30% of the daily energy expenditure and reached 75% within 7 days of the intervention.

RESULTS

No significant differences were observed in the baseline characteristics of the patients in the hypocaloric and full-energy groups. The incidence of severe gastrointestinal intolerance was relatively high in the full-energy group (P < .001). Duration of mechanical ventilation and length of hospital stay were lower in the hypocaloric group compared with the full-energy group (P = .014 and P = .046, respectively). However, no significant differences were denoted in the length of ICU admission (P = .163), 28-day mortality (P = .640), and pneumonia (P = .162) between the study groups.

CONCLUSIONS

In the neurocritical care unit, hypocaloric enteral feeding was associated with lower gastrointestinal intolerance, as well as reduced duration of ventilator dependence and length of hospital stay.

The Long-Term Impact of Severe Burn Trauma on Musculoskeletal Health

Severe burn injury causes a profound stress response that leads to muscle and bone cachexia. Evidence suggests that these deficits persist for several months or even years after injury and are associated with growth delay, increased incidence of fractures, and increased hospital admissions for musculoskeletal disorders. Thus, there is an overwhelming need to determine the optimal acute and rehabilitative strategies to mitigate these deficits and improve quality of life for burn survivors. To date, there is limited research on the long-term impact of cachexia on functional performance and overall health, as well as on the lasting impact of pharmacological, nutritional, and exercise interventions. The aim of this review is to emphasize the long-term consequences of musculoskeletal cachexia and determine the best evidence-based strategies to attenuate it. We also underline important knowledge gaps that need to be addressed in order to improve care of burn survivors.

Burns: modified metabolism and the nuances of nutrition therapy

OBJECTIVE

To review the effects of burn injury on nutritional requirements and how this can best be supported in a healthcare setting.

METHOD

A literature search for articles discussing nutrition and/or metabolism following burn injury was carried out. PubMed, Embase and Web of Science databases were searched using the key search terms 'nutrition' OR 'metabolism' AND 'burn injury' OR 'burns'. There was no limitation on the year of publication.

RESULTS

A total of nine articles met the inclusion criteria, the contents of which are discussed in this manuscript.

CONCLUSION

Thermal injury elicits the greatest metabolic response, among all traumatic events, in critically ill patients. In order to ensure burn patients can meet the demands of their increased metabolic rate and energy expenditure, adequate nutritional support is essential. Burn injury results in a unique pathophysiology, involving alterations in endocrine, inflammatory, metabolic and immune pathways and nutritional support needed during the inpatient stay varies depending on burn severity and idiosyncratic patient physiologic parameters.

Progressive exercise training improves maximal aerobic capacity in individuals with well-healed burn injuries

Long-term rehabilitative strategies are important for individuals with well-healed burn injuries. Such information is particularly critical because patients are routinely surviving severe burn injuries given medical advances in the acute care setting. The purpose of this study was to test the hypothesis that a 6-mo community-based exercise training program will increase maximal aerobic capacity (V̇o_2max) in subjects with prior burn injuries, with the extent of that increase influenced by the severity of the burn injury (i.e., percent body surface area burned). Maximal aerobic capacity (indirect calorimetry) and skeletal muscle oxidative enzyme activity (biopsy of the vastus lateralis muscle) were measured pre- and postexercise training in noninjured control subjects (n = 11) and in individuals with well-healed burn injuries (n = 13, moderate body surface area burned; n = 20, high body surface area burned). Exercise training increased V̇o_2max in all groups (control: 15 ± 5%; moderate body surface area: 11 ± 3%; high body surface area: 11 ± 2%; P < 0.05), though the magnitude of this improvement did not differ between groups (P = 0.7). Exercise training also increased the activity of the skeletal muscle oxidative enzymes citrate synthase (P < 0.05) and cytochrome c oxidase (P < 0.05), an effect that did not differ between groups (P = 0.2). These data suggest that 6 mo of progressive exercise training improves V̇o_2max in individuals with burn injuries and that the magnitude of body surface area burned does not lessen this adaptive response.

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.

Weight changes and patterns of weight measurements in hospitalized burn patients: a contemporary analysis

Background

Severe burn is associated with significant changes in body weight due to resuscitation volumes, fluid shifts, a hypermetabolic state, prolonged bed rest, and caloric intake. Our goal was to quantify and describe trends in weight change in patients with burns of all severities under modern treatment conditions and to identify the time points at which these changes occur.

Methods

An institutional review board-approved chart review was conducted of acute burn patients treated at an American Burn Association-verified regional burn center from February 2016 to November 2016. Patients were then divided into three groups based on percent of total burn surface area (%TBSA) burn: 1–19%, 20–39%, and ≥ 40%. Weight was expressed as percent change of weight from baseline. Regression analysis was conducted on percent weight changes for each TBSA group.

Results

We identified 197 burn patients with a length of stay (LOS) of ≥ 7 days. Of the study cohort, 149 had TBSA burn of 1–19%, 27 had TBSA burn of 20–39%, and 21 had TBSA burn of ≥ 40%. All groups had a majority of White male, non-Hispanic patients with mean ages between 40 and 42 years. Burn patients with > 20% TBSA burn had a median increase in weight above baseline of approximately 5 to 8% likely due to resuscitation fluids within the first week of hospitalization. Weight loss below baseline often did not exceed 10% and was more pronounced as LOS increased, mostly in patients with > 20% TBSA burn. Whereas patients with 1–19% TBSA burn on average returned to baseline weight at last measurement, patients with 20–39% TBSA and ≥ 40% TBSA burn continued a decline in weight at 4 weeks (r² = 0.57 and 0.55, respectively) on the same trajectory.

Conclusions

Burn patients with > 20% TBSA burn had an increase in weight above baseline of up to 8%, likely due to resuscitation fluids within the first week of hospitalization. Weight loss below baseline often did not exceed 10% and was more pronounced as LOS increased, mostly in patients with > 20% TBSA burn. Therefore, our patients on average, lost body weight to a lesser extent than the maximum mean loss of 22% of pre-burn weight reported prior to modern treatment conditions.

Metabolic support challenges with obesity during critical illness

Adiposity-based chronic disease, critical illness, and nutrition therapy increase the risk for overfeeding and worsened nutritional and clinical outcomes. Hypocaloric, high-protein nutrition therapy provides critically ill obese patients the opportunity to achieve net protein anabolism with a reduced risk for overfeeding-related complications. The intent of this review is to discuss the impact of obesity on clinical outcomes, describe the consequences of obesity that increase complications associated with nutrition therapy, provide the framework to develop a hypocaloric, high-protein regimen, review the scientific evidence to support this mode of therapy, and discuss its limitations. Practical suggestions for patient monitoring are also provided.

Prescribed hypocaloric nutrition support for critically-ill adults

BACKGROUND

There are controversies about the amount of calories and the type of nutritional support that should be given to critically-ill people. Several authors advocate the potential benefits of hypocaloric nutrition support, but the evidence is inconclusive.

OBJECTIVES

To assess the effects of prescribed hypocaloric nutrition support in comparison with standard nutrition support for critically-ill adults SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, Cochrane Library), MEDLINE, Embase and LILACS (from inception to 20 June 2017) with a specific strategy for each database. We also assessed three websites, conference proceedings and reference lists, and contacted leaders in the field and the pharmaceutical industry for undetected/unpublished studies. There was no restriction by date, language or publication status.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing hypocaloric nutrition support to normo- or hypercaloric nutrition support or no nutrition support (e.g. fasting) in adults hospitalized in intensive care units (ICUs).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We meta-analysed data for comparisons in which clinical heterogeneity was low. We conducted prespecified subgroup and sensitivity analyses, and post hoc analyses, including meta-regression. Our primary outcomes were: mortality (death occurred during the ICU and hospital stay, or 28- to 30-day all-cause mortality); length of stay (days stayed in the ICU and in the hospital); and Infectious complications. Secondary outcomes included: length of mechanical ventilation. We assessed the quality of evidence with GRADE.

MAIN RESULTS

We identified 15 trials, with a total of 3129 ICU participants from university-associated hospitals in the USA, Colombia, Saudi Arabia, Canada, Greece, Germany and Iran. There are two ongoing studies. Participants suffered from medical and surgical conditions, with a variety of inclusion criteria. Four studies used parenteral nutrition and nine studies used only enteral nutrition; it was unclear whether the remaining two used parenteral nutrition. Most of them could not achieve the proposed caloric targets, resulting in small differences in the administered calories between intervention and control groups. Most studies were funded by the US government or non-governmental associations, but three studies received funding from industry. Five studies did not specify their funding sources.The included studies suffered from important clinical and statistical heterogeneity. This heterogeneity did not allow us to report pooled estimates of the primary and secondary outcomes, so we have described them narratively.When comparing hypocaloric nutrition support with a control nutrition support, for hospital mortality (9 studies, 1775 participants), the risk ratios ranged from 0.23 to 5.54; for ICU mortality (4 studies, 1291 participants) the risk ratios ranged from 0.81 to 5.54, and for mortality at 30 days (7 studies, 2611 participants) the risk ratios ranged from 0.79 to 3.00. Most of these estimates included the null value. The quality of the evidence was very low due to unclear or high risk of bias, inconsistency and imprecision.Participants who received hypocaloric nutrition support compared to control nutrition support had a range of mean hospital lengths of stay of 15.70 days lower to 10.70 days higher (10 studies, 1677 participants), a range of mean ICU lengths of stay 11.00 days lower to 5.40 days higher (11 studies, 2942 participants) and a range of mean lengths of mechanical ventilation of 13.20 days lower to 8.36 days higher (12 studies, 3000 participants). The quality of the evidence for this outcome was very low due to unclear or high risk of bias in most studies, inconsistency and imprecision.The risk ratios for infectious complications (10 studies, 2804 participants) of each individual study ranged from 0.54 to 2.54. The quality of the evidence for this outcome was very low due to unclear or high risk of bias, inconsistency and imprecisionWe were not able to explain the causes of the observed heterogeneity using subgroup and sensitivity analyses or meta-regression.

AUTHORS' CONCLUSIONS

The included studies had substantial clinical heterogeneity. We found very low-quality evidence about the effects of prescribed hypocaloric nutrition support on mortality in hospital, in the ICU and at 30 days, as well as in length of hospital and ICU stay, infectious complications and the length of mechanical ventilation. For these outcomes there is uncertainty about the effects of prescribed hypocaloric nutrition, since the range of estimates includes both appreciable benefits and harms.Given these limitations, results must be interpreted with caution in the clinical field, considering the unclear balance of the risks and harms of this intervention. Future research addressing the clinical heterogeneity of participants and interventions, study limitations and sample size could clarify the effects of this intervention.

Malnutrition in Gastrointestinal Disorders: Detection and Nutritional Assessment

All patients with significant gastrointestinal disease should be clinically assessed for protein calorie malnutrition by using the Subjective Global Assessment. Blood tests for anemia, electrolytes, calcium, phosphorus, magnesium, ferritin, vitamin B₁₂, and folate should be considered for assessment of major micronutrients. Where malabsorption or inflammatory bowel disease is diagnosed, bone mineral density using dual beam x-ray absorptiometry, 25-OH vitamin D levels, and measurement of other vitamins and trace elements should be considered. In addition, in at-risk patients, vitamin and trace element clinical deficiency syndromes should be considered during patient assessment.

Body Composition following Necrotising Enterocolitis in Preterm Infants

BACKGROUND

The optimal nutritional regimen for preterm infants, including those that develop necrotising enterocolitis (NEC), is unknown.

OBJECTIVE

The objective here was to evaluate body composition at term in infants following NEC, in comparison with healthy infants. The primary outcome measure was non-adipose tissue mass (non-ATM).

METHODS

We compared body composition assessed by magnetic resonance imaging at term in infants born <31 weeks of gestational age that participated in NEON, a trial comparing incremental versus immediate delivery of parenteral amino acids on non-ATM, and SMOF versus intralipid on intrahepatocellular lipid content. There were no differences in the primary outcomes. We compared infants that received surgery for NEC (NEC-surgical), infants with medically managed NEC (NEC-medical), and infants without NEC (reference).

RESULTS

A total of 133 infants were included (8 NEC-surgical; 15 NEC-medical; 110 reference). In comparison with the reference group, infants in the NEC-surgical and NEC-medical groups were significantly lighter [adjusted mean difference (95% CI) NEC-surgical: -630 g (-1,010, -210), p = 0.003; NEC-medical: -440 g (-760, -110), p = 0.009] and the total adipose tissue volume (ATV) was significantly lower [NEC-surgical: -360 cm3 (-516, -204), p < 0.001; NEC-medical: -127 cm3 (-251, -4); p = 0.043]. There were no significant differences in non-ATM [adjusted mean difference (95% CI) NEC-surgical: -46 g (-281, 189), p = 0.70; NEC-medical: -122 g (-308, 63), p = 0.20].

CONCLUSION

The lower weight at term in preterm infants following surgically and medically managed NEC, in comparison to preterm infants that did not develop the disease, was secondary to a reduction in ATV. This suggests that the nutritional regimen received was adequate to preserve non-ATM but not to support the normal third-trimester deposition of adipose tissue in preterm infants.

Ultrasound assessment of rectus femoris and anterior tibialis muscles in young trauma patients

Purpose

Quantitative and qualitative changes of skeletal muscle are typical and early findings in trauma patients, being possibly associated with functional impairment. Early assessment of muscle changes—as evaluated by muscle ultrasonography—could yield important information about patient’s outcome.

Methods

In this prospective observational study, we used ultrasonography to evaluate the morphological changes of rectus femoris (RF) and anterior tibialis (AT) muscles in a group of young, previously healthy trauma patients on enteral feeding.

Results

We studied 38 severely injured patients (median Injury Severity Score = 34; median age = 40 y.o.) over the course of the ICU stay up to 3 weeks after trauma. We found a progressive loss of muscle mass from day 0 to day 20, that was more relevant for the RF (45%) than for the AT (22%); this was accompanied by an increase in echogenicity (up to 2.5 by the Heckmatt Scale, where normal echogenicity = 1), which is an indicator of myofibers depletion.

Conclusions

Ultrasound evaluation of skeletal muscles is inexpensive, noninvasive, simple and easily repeatable. By this method, we were able to quantify the morphological changes of skeletal muscle in trauma patients. Further studies may rely on this technicque to evaluate the impact of different therapeutic strategies on muscle wasting.

The P50 Research Center in Perioperative Sciences: How the investment by the National Institute of General Medical Sciences in team science has reduced postburn mortality

Since the inception of the P50 Research Center in Injury and Peri-operative Sciences (RCIPS) funding mechanism, the National Institute of General Medical Sciences has supported a team approach to science. Many advances in critical care, particularly burns, have been driven by RCIPS teams. In fact, burns that were fatal in the early 1970s, prior to the inception of the P50 RCIPS program, are now routinely survived as a result of the P50-funded research. The advances in clinical care that led to the reduction in postburn death were made by optimizing resuscitation, incorporating early excision and grafting, bolstering acute care including support for inhalation injury, modulating the hypermetabolic response, augmenting the immune response, incorporating aerobic exercise, and developing antiscarring strategies. The work of the Burn RCIPS programs advanced our understanding of the pathophysiologic response to burn injury. As a result, the effects of a large burn on all organ systems have been studied, leading to the discovery of persistent dysfunction, elucidation of the underlying molecular mechanisms, and identification of potential therapeutic targets. Survival and subsequent patient satisfaction with quality of life have increased. In this review article, we describe the contributions of the Galveston P50 RCIPS that have changed postburn care and have considerably reduced postburn mortality.

Metabolic and Endocrine Considerations After Burn Injury

Severe burn injury is followed by a profound hypermetabolic response that persists up to 2 years after injury. It is mediated by up to 50-fold elevations in plasma catecholamines, cortisol, and glucagon that lead to whole-body catabolism, elevated resting energy expenditures, and multiorgan dysfunction. Modulation of the response by early excision and grafting of burn wounds, thermoregulation, control of infection, early and continuous enteral nutrition, and pharmacologic treatments aimed at mitigating physiologic derangements have markedly decreased morbidity.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas.

Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Considerations When Using Predictive Equations to Estimate Energy Needs Among Older, Hospitalized Patients: A Narrative Review

The aim of this narrative review was to summarize the accuracy of predictive equations used to estimate energy expenditure in older, hospitalized adults. More than 50% of patients admitted to intensive care units are older adults. Currently accepted prediction equations used to determine energy intake in the older, hospitalized patient were not specifically developed for the aging population. Rates of multimorbidity, polypharmacy and malnutrition, conditions that influence energy expenditure, are higher in older adults compared to younger adults. For these reasons, current equations may not accurately assess energy needs in this population. As the evidence demonstrating the importance of nutritional supplementation in older, hospitalized adults grows, more accurate energy assessment methods that account for age-related conditions are needed to predict nutritional requirements.

Protein and Calorie Requirements Associated With the Presence of Obesity

Obesity compounds the metabolic response to critical illness and increases the risk for overfeeding complications due to its comorbidities. Hypocaloric, high-protein nutrition therapy affords the hospitalized patient with obesity the opportunity to achieve net protein anabolism with a reduced risk of overfeeding complications. The intent of this review is to provide the theoretical framework for development of a hypocaloric high-protein regimen, scientific evidence to support this mode of therapy, and unique considerations for its use in specialized subpopulations. Macronutrient goals and practical suggestions for patient monitoring are given.

Permissive Underfeeding of the Critically Ill Patient

The rise in the popularity of nutrition support in the 1970s was associated with the concept of "hyperalimentation." This concept was based on the early findings that increased metabolic rates were observed in various disease states such as trauma, sepsis, and burns. The aim was to feed 40% to 100% above the basal metabolic rate to avoid weight loss associated with critical illness. Since that time, several observations have indicated that permissive underfeeding may be beneficial because: (a) the metabolic rate is not markedly increased in most patients with critical illness except burns; (b) weight gain during nutrition support in critical illness is not caused by a gain in nitrogen but fat; (c) energy intake as glucose in excess of needs causes increased carbon dioxide production and a fatty liver; (d) hyperglycemia increases the risk of infective complications; and (e) a controlled trial of preoperative nutrition in which patients received 1000 kcal above the metabolic rate increased infectious complications.

Monitoring Energy Metabolism with Indirect Calorimetry: Instruments, Interpretation, and Clinical Application

Indirect calorimetry is the best measure to guide calorie administration during nutrition support. This article presents an update of the types of currently available indirect calorimeters and reviews the recent advances that guide the clinical application of indirect calorimetry. The emphasis of this report is placed on issues that the practicing clinician can use to evaluate, interpret, and apply measurements of energy expenditure.

Nutrition Support Strategies for Severely Burned Patients

Significant weight loss is a common complication of a major burn injury. Before the modern era of early enteral nutrition support, such a complication contributed significantly to impaired wound healing, raised risk of infectious morbidity, and ultimately increased mortality. Nutrition management of the burn patient is designed to promote wound healing while minimizing loss of lean body mass. The burn patient characteristically demonstrates an increase in energy expenditure after the initial injury and period of resuscitation. Studies have demonstrated that early institution of enteral feeding can attenuate the stress response, abate hypermetabolism, and improve patient outcome.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas. Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Nutritional support for critically ill children

BACKGROUND

Nutritional support in the critically ill child has not been well investigated and is a controversial topic within paediatric intensive care. There are no clear guidelines as to the best form or timing of nutrition in critically ill infants and children. This is an update of a review that was originally published in 2009. .

OBJECTIVES

The objective of this review was to assess the impact of enteral and parenteral nutrition given in the first week of illness on clinically important outcomes in critically ill children. There were two primary hypotheses:1. the mortality rate of critically ill children fed enterally or parenterally is different to that of children who are given no nutrition;2. the mortality rate of critically ill children fed enterally is different to that of children fed parenterally.We planned to conduct subgroup analyses, pending available data, to examine whether the treatment effect was altered by:a. age (infants less than one year versus children greater than or equal to one year old);b. type of patient (medical, where purpose of admission to intensive care unit (ICU) is for medical illness (without surgical intervention immediately prior to admission), versus surgical, where purpose of admission to ICU is for postoperative care or care after trauma).We also proposed the following secondary hypotheses (a priori), pending other clinical trials becoming available, to examine nutrition more distinctly:3. the mortality rate is different in children who are given enteral nutrition alone versus enteral and parenteral combined;4. the mortality rate is different in children who are given both enteral feeds and parenteral nutrition versus no nutrition.

SEARCH METHODS

In this updated review we searched: the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 2); Ovid MEDLINE (1966 to February 2016); Ovid EMBASE (1988 to February 2016); OVID Evidence-Based Medicine Reviews; ISI Web of Science - Science Citation Index Expanded (1965 to February 2016); WebSPIRS Biological Abstracts (1969 to February 2016); and WebSPIRS CAB Abstracts (1972 to February 2016). We also searched trial registries, reviewed reference lists of all potentially relevant studies, handsearched relevant conference proceedings, and contacted experts in the area and manufacturers of enteral and parenteral nutrition products. We did not limit the search by language or publication status.

SELECTION CRITERIA

We included studies if they were randomized controlled trials; involved paediatric patients, aged one day to 18 years of age, who were cared for in a paediatric intensive care unit setting (PICU) and had received nutrition within the first seven days of admission; and reported data for at least one of the pre-specified outcomes (30-day or PICU mortality; length of stay in PICU or hospital; number of ventilator days; and morbid complications, such as nosocomial infections). We excluded studies if they only reported nutritional outcomes, quality of life assessments, or economic implications. Furthermore, we did not address other areas of paediatric nutrition, such as immunonutrition and different routes of delivering enteral nutrition, in this review.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the searches, applied the inclusion criteria, and performed 'Risk of bias' assessments. We resolved discrepancies through discussion and consensus. One author extracted data and a second checked data for accuracy and completeness. We graded the evidence based on the following domains: study limitations, consistency of effect, imprecision, indirectness, and publication bias.

MAIN RESULTS

We identified only one trial as relevant. Seventy-seven children in intensive care with burns involving more than 25% of the total body surface area were randomized to either enteral nutrition within 24 hours or after at least 48 hours. No statistically significant differences were observed for mortality, sepsis, ventilator days, length of stay, unexpected adverse events, resting energy expenditure, nitrogen balance, or albumin levels. We assessed the trial as having unclear risk of bias. We consider the quality of the evidence to be very low due to there being only one small trial. In the most recent search update we identified a protocol for a relevant randomized controlled trial examining the impact of withholding early parenteral nutrition completing enteral nutrition in pediatric critically ill patients; no results have been published.

AUTHORS' CONCLUSIONS

There was only one randomized trial relevant to the review question. Research is urgently needed to identify best practices regarding the timing and forms of nutrition for critically ill infants and children.

Nutrition: A Primary Therapy in Pediatric Acute Respiratory Distress Syndrome

Appropriate nutrition is an essential component of intensive care management of children with acute respiratory distress syndrome (ARDS) and is linked to patient outcomes. One out of every two children in the pediatric intensive care unit (PICU) will develop malnutrition or have worsening of baseline malnutrition and present with specific micronutrient deficiencies. Early and adequate enteral nutrition (EN) is associated with improved 60-day survival after pediatric critical illness, and, yet, despite early EN guidelines, critically ill children receive on average only 55% of goal calories by PICU day 10. Inadequate delivery of EN is due to perceived feeding intolerance, reluctance to enterally feed children with hemodynamic instability, and fluid restriction. Underlying each of these factors is large practice variation between providers and across institutions for initiation, advancement, and maintenance of EN. Strategies to improve early initiation and advancement and to maintain delivery of EN are needed to improve morbidity and mortality from pediatric ARDS. Both, over and underfeeding, prolong duration of mechanical ventilation in children and worsen other organ function such that precise calorie goals are needed. The gut is thought to act as a "motor" of organ dysfunction, and emerging data regarding the role of intestinal barrier functions and the intestinal microbiome on organ dysfunction and outcomes of critical illness present exciting opportunities to improve patient outcomes. Nutrition should be considered a primary rather than supportive therapy for pediatric ARDS. Precise nutritional therapies, which are titrated and targeted to preservation of intestinal barrier function, prevention of intestinal dysbiosis, preservation of lean body mass, and blunting of the systemic inflammatory response, offer great potential for improving outcomes of pediatric ARDS. In this review, we examine the current evidence regarding dose, route, and timing of nutrition, current recommendations for provision of nutrition to children with ARDS, and the current literature for immune-modulating diets for pediatric ARDS. We will examine emerging data regarding the role of the intestinal microbiome in modulating the response to critical illness.

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Chaque année, le congrès de la SFB est l'occasion d'une mise au point sur un thème (« table ronde ».) Celui choisi en 2015 était la nutrition. Huit orateurs se sont succédés, faisant le point sur les données actuelles de la science, les pratiques dans les centres, et les recommandations actuelles, datant de 2013. Cet article se propose de diffuser les interventions.

Adaptive neuro-fuzzy inference systems with k-fold cross-validation for energy expenditure predictions based on heart rate

This paper presents a new model based on adaptive neuro-fuzzy inference systems (ANFIS) to predict oxygen consumption (V˙O2) from easily measured variables. The ANFIS prediction model consists of three ANFIS modules for estimating the Flex-HR parameters. Each module was developed based on clustering a training set of data samples relevant to that module and then the ANFIS prediction model was tested against a validation data set. Fifty-eight participants performed the Meyer and Flenghi step-test, during which heart rate (HR) and V˙O2 were measured. Results indicated no significant difference between observed and estimated Flex-HR parameters and between measured and estimated V˙O2 in the overall HR range, and separately in different HR ranges. The ANFIS prediction model (MAE = 3 ml kg(-1) min(-1)) demonstrated better performance than Rennie et al.'s (MAE = 7 ml kg(-1) min(-1)) and Keytel et al.'s (MAE = 6 ml kg(-1) min(-1)) models, and comparable performance with the standard Flex-HR method (MAE = 2.3 ml kg(-1) min(-1)) throughout the HR range. The ANFIS model thus provides practitioners with a practical, cost- and time-efficient method for V˙O2 estimation without the need for individual calibration.