Trophic or full nutritional support?:

Effects of enteral nutrition with different energy supplies on metabolic changes and organ damage in burned rats

BACKGROUND

Enteral nutrition (EN) is an important treatment for burn patients. However, severe gastrointestinal damage caused by major burns often leads to EN intolerance. Trophic EN solves this problem basically, but how to transition from trophic EN to standard EN smoothly is still a challenge in burn clinical nutrition. The aim of this study is to investigate the effects of EN with different energy supplies on metabolic changes, organ damage and prognosis in burned rats.

METHODS

Different feeding regimens were designed based on the continuous monitoring of resting energy expenditure in rats. Thirty-two Sprague-Dawley rats were randomly divided into a normal control group, burn +50% REE group, burn +75% REE group and burn +100% REE group. At the end of a nutritional treatment cycle (14th day), nuclear magnetic resonance spectroscopy, blood biochemistry analysis and quantification of subscab bacteria were performed to explore the differences in metabolic changes, degrees of organ damage and prognoses between the groups.

RESULTS

Sixteen metabolites involving seven metabolic pathways were identified from the different energy supply groups. After burn injury, resting energy consumption and body weight loss increased obviously. Meanwhile, weight loss was inversely related to energy supply. The greatest changes in the degree of organ damage, the level of plasma proteins, lipids and endotoxins, as well as the quantification of subscab bacteria were observed in the 50% REE group, followed by the 75 and 100% groups.

CONCLUSIONS

Achieving an early balance between energy supply and expenditure is conducive to mitigating metabolic disorders and improving prognosis after burn injury.

When is enteral nutrition indicated?

Enteral nutrition (EN) is a vital component of nutrition around the world. EN allows for delivery of nutrients to those who cannot maintain adequate nutrition by oral intake alone. Common questions regarding EN are when to initiate and in what scenarios it is safe. The answers to these questions are often complex and require an evidence-based approach. The Board of Directors of the American Society for Parenteral and Enteral Nutrition (ASPEN) established an Enteral Nutrition Committtee to address the important questions surrounding the indications for EN. Consensus recommendations were established based on eight extremely clinically relevant questions regarding EN indications as deemed by the Enteral Nutrition Committee. These consensus recommendations may act as a guide for clinicians and stakeholders on difficult questions pertaining to indications for EN. This paper was approved by the ASPEN Board of Directors.

SIRT3-mediated mitochondrial autophagy in refeeding syndrome-related myocardial injury in sepsis rats

Background

Myocardial injury induced by refeeding syndrome (RFS) is one of the important causes of deterioration in critically ill patients. Sirtuin-3 (SIRT3) has been shown to regulate mitochondrial autophagy in myocardial ischemia/reperfusion injury; however, the role of mitochondrial autophagy on RFS-related myocardial injury in patients in critical condition has not been reported on.

Methods

Thirty Sprague-Dawley (SD) rats were divided into 3 groups (n=10 each group): the control group; the standard calorie refeeding (SCR) group; and the low calorie refeeding (LCR) group. The rats were weighed every third or four days from day 1 to day 14. On day 14, all rats were anesthetized and received an echocardiography test. Blood and bronchoalveolar lavage fluid (BALF) were collected and tested for arterial oxygen pressure (PaO₂), phosphorus (P), and calcium (Ca), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and cardiac troponin 1 (cTnI), myeloperoxidase (MPO), tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and IL-6. The histopathological change of hearts and lungs were evaluated, and lung injury score was calculated. Mitochondrial autophagy related proteins (including Beclin1, LC3, mitofusin-2, Mfn2, PINK1, Parkin, and SIRT3) were analyzed using a Western blot. To evaluate the effect of SIRT3, 20 rats were divided into 2 groups (n=10 each group): The adeno-associated virus 9 (AAV9-Nc) group; and the AAV9-SIRT3 overexpression (AAV9-SIRT3) group. The protocols for rats were the same as the SCR group since day 22 after injection of AAV9. The protein expressions of PINK1, Parkin, and SIRT3 were compared between the AAV9-Nc group and AAV9-SIRT3 group.

Results

SCR caused significant decline in cardiac contractility and increased inflammatory cell infiltration in myocardial tissue. Meanwhile, Beclin1, LC3, PINK1, Parkin, and SIRT3 levels decreased, while Mfn2 showed no significant change. Furthermore, significant positive correlations were also found between SIRT3 and P, PINK1, and Parkin, and significant negative correlations were found between SIRT3 and CK-MB, LDH, and cTnI. Overexpression of SIRT3 activated the PINK1/Parkin mediated mitochondrial autophagy.

Conclusions

SIRT3 has an essential role in RFS-related myocardial injury during LPS induced chronic sepsis in rats, probably via regulating mitochondrial autophagy.

A multicenter randomized clinical trial of pharmacological vitamin B1 administration to critically ill patients who develop hypophosphatemia during enteral nutrition (The THIAMINE 4 HYPOPHOSPHATEMIA trial)

BACKGROUND

Hypophosphatemia may be a useful biomarker to identify thiamine deficiency in critically ill enterally-fed patients. The objective was to determine whether intravenous thiamine affects blood lactate, biochemical and clinical outcomes in this group.

METHOD

This randomized clinical trial was conducted across 5 Intensive Care Units. Ninety critically ill adult patients with a serum phosphate ≤0.65 mmol/L within 72 h of commencing enteral nutrition were randomized to intravenous thiamine (200 mg every 12 h for up to 14 doses) or usual care (control). The primary outcome was blood lactate over time and data are median [IQR] unless specified.

RESULTS

Baseline variables were well balanced (thiamine: lactate 1.2 [1.0, 1.6] mmol/L, phosphate 0.56 [0.44, 0.64] mmol/L vs. control: lactate 1.0 [0.8, 1.3], phosphate 0.54 [0.44, 0.61]). Patients randomized to the intervention received a median of 11 [7.5, 13.5] doses for a total of 2200 [1500, 2700] mg of thiamine. Blood lactate over the entire 7 days of treatment was similar between groups (mean difference = -0.1 (95 % CI -0.2 to 0.1) mmol/L; P = 0.55). The percentage change from lactate pre-randomization to T = 24 h was not statistically different (thiamine: -32 (-39, -26) vs. control: -24 (-31, -16) percent, P = 0.09). Clinical outcomes were not statistically different (days of vasopressor administration: thiamine 2 [1, 4] vs. control 2 [0, 5.5] days; P = 0.37, and deaths 9 (21 %) vs. 5 (11 %); P = 0.25).

CONCLUSIONS

In critically ill enterally-fed patients who developed hypophosphatemia, intravenous thiamine did not cause measurable differences in blood lactate or clinical outcomes.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry (ACTRN12619000121167).

Prognostic capability of the Maximum Acute Gastrointestinal Injury Score and of caloric intake in patients requiring vasopressors: A multicenter prospective cohort study

PURPOSE

Our main objective was to use the Maximum Acute Gastrointestinal Injury Score (AGI_max) to evaluate the prognostic capability of gastrointestinal dysfunction (GID), on hospital mortality in patients on mechanical ventilation (MV) requiring vasopressors. A secondary goal was to analyze the relationship between AGI_max and vasopressor dosage with increasing caloric intake.

MATERIALS AND METHODS

Prospective multicenter cohort study in ten ICUs across Argentina. Consecutive adult patients on MV, requiring vasopressors and receiving enteral nutrition (EN) were included. AGI_max was identified (I-IV) using a modified AGI score. Comparisons of clinical and outcome variables were performed in 3 predetermined EN-groups: <10 kcal/kg/d, ≥10 to <20 kcal/kg/d, or ≥ 20 kcal/kg/d.

RESULTS

A total of 494 patients met all inclusion criteria. Forty-four percent of patients had severe AGI_max and 17% received <10 kcal/kg/day, indicating more severity and higher mortality. Notable independent predictors of mortality were AGI_max, vasopressors, and caloric intake. PN was the only factor which had an inverse relationship to mortality.

CONCLUSIONS

In this population, patients with AGI_max III-IV were significantly associated with lower caloric intake and greater hospital mortality, highlighting the importance of AGI as a prognostic tool. As PN was linked with lower mortality, it could be an option to explore in further studies.

Metabolic and Nutritional Characteristics of Long-Stay Critically Ill Patients

Background: insufficient feeding is frequent in the intensive care unit (ICU), which results in poor outcomes. Little is known about the nutrition pattern of patients requiring prolonged ICU stays. The aims of our study are to describe the demographic, metabolic, and nutritional specificities of chronically critically ill (CCI) patients defined by an ICU stay >2 weeks, and to identify an early risk factor. Methods: analysis of consecutive patients prospectively admitted to the CCI program, with the following variables: demographic characteristics, Nutrition Risk Screening (NRS-2002) score, total daily energy from nutritional and non-nutritional sources, protein and glucose intakes, all arterial blood glucose values, length of ICU and hospital stay, and outcome (ICU and 90-day survival). Two phases were considered for the analysis: the first 10 days, and the next 20 days of the ICU stay. Statistics: parametric and non-parametric tests. Results: 150 patients, aged 60 ± 15 years were prospectively included. Median (Q1, Q3) length of ICU stay was 31 (26, 46) days. The mortality was 18% at ICU discharge and 35.3% at 90 days. Non-survivors were older (p = 0.024), tended to have a higher SAPSII score (p = 0.072), with a significantly higher NRS score (p = 0.033). Enteral nutrition predominated, while combined feeding was minimally used. All patients received energy and protein below the ICU’s protocol recommendation. The proportion of days with fasting was 10.8%, being significantly higher in non-survivors (2 versus 3 days; p = 0.038). Higher protein delivery was associated with an increase in prealbumin over time (r² = 0.19, p = 0.027). Conclusions: High NRS scores may identify patients at highest risk of poor outcome when exposed to underfeeding. Further studies are required to evaluate a nutrition strategy for patients with high NRS, addressing combined parenteral nutrition and protein delivery.

The association between nutritional adequacy and 28-day mortality in the critically ill is not modified by their baseline nutritional status and disease severity

Background

During the initial phase of critical illness, the association between the dose of nutrition support and mortality risk may vary among patients in the intensive care unit (ICU) because the prevalence of malnutrition varies widely (28 to 78%), and not all ICU patients are severely ill. Therefore, we hypothesized that a prognostic model that integrates nutritional status and disease severity could accurately predict mortality risk and classify critically ill patients into low- and high-risk groups. Additionally, in critically ill patients placed on exclusive nutritional support (ENS), we hypothesized that their risk categories could modify the association between dose of nutrition support and mortality risk.

Methods

A prognostic model that predicts 28-day mortality was built from a prospective cohort study of 440 patients. The association between dose of nutrition support and mortality risk was evaluated in a subgroup of 252 mechanically ventilated patients via logistic regressions, stratified by low- and high-risk groups, and days of exclusive nutritional support (ENS) [short-term (≤ 6 days) vs. longer-term (≥ 7 days)]. Only the first 6 days of ENS was evaluated for a fair comparison.

Results

The prognostic model demonstrated good discrimination [AUC 0.78 (95% CI 0.73–0.82), and a bias-corrected calibration curve suggested fair accuracy. In high-risk patients with short-term ENS (≤ 6 days), each 10% increase in goal energy and protein intake was associated with an increased adjusted odds (95% CI) of 28-day mortality [1.60 (1.19–2.15) and 1.47 (1.12–1.86), respectively]. In contrast, each 10% increase in goal protein intake during the first 6 days of ENS in high-risk patients with longer-term ENS (≥ 7 days) was associated with a lower adjusted odds of 28-day mortality [0.75 (0.57–0.99)]. Despite the opposing associations, the mean predicted mortality risks and prevalence of malnutrition between short- and longer-term ENS patients were similar.

Conclusions

Combining baseline nutritional status and disease severity in a prognostic model could accurately predict 28-day mortality. However, the association between the dose of nutrition support during the first 6 days of ENS and 28-day mortality was independent of baseline disease severity and nutritional status.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2500-z) contains supplementary material, which is available to authorized users.

Changing paradigms in metabolic support and nutrition therapy during critical illness

PURPOSE OF REVIEW

To summarize the most recent advances in acute metabolic care and critical care nutrition.

RECENT FINDINGS

Recent research has demonstrated unknown consequences of high protein and amino acid administration in the early phase of ICU stay associated with dysregulated glucagon release leading to hepatic amino acid breakdown and suggested adverse effects on autophagy and long-term outcome. Progress has been made to measure body composition in the ICU. Refeeding hypophosphatemia and refeeding syndrome are common during critical illness, phosphate monitoring is essential after the start of nutrition therapy, and caloric restriction is recommendable in these patients.In recent studies, enteral nutrition is no longer superior to parenteral nutrition and signals of harm using the enteral route in shock have been suggested. However, during extracorporeal life support, enteral nutrition seems well tolerated. Intermittent or bolus enteral feeding seems an exciting concept concerning its potential anabolic effects. Studies on vitamin C, thiamine, and corticosteroid combinations suggest potential to improve outcome.

SUMMARY

These new findings will probably change the practice of metabolic and nutrition therapy in critical illness and challenge paradigms advocated for long.