Malabsorption and nutritional balance in the ICU: fecal weight as a biomarker: a prospective observational pilot study

How to interpret and apply the results of indirect calorimetry studies: A case-based tutorial

Evidence is growing that the individual adjustment of energy targets guided by indirect calorimetry (IC) can improve outcome. With the development of a new generation of devices that are easier to use and rapid, it appears important to share knowledge and expertise that may be used to individualize nutrition care. Despite the focus of this tutorial being on one contemporary device, the principles of IC apply across existing devices and can assist tailoring the nutrition prescription and in assessing response to nutrition therapy. The present tutorial addresses its clinical application in intubated mechanically ventilated and spontaneously breathing adult patients (canopy), i.e. it covers the range from critical illness to outpatients. The cases that are presented show how the measured energy expenditure (mEE), and the respiratory quotient (RQ), i.e. the ratio of expired CO2 to consumed O2, should be applied in different cases, to adapt and individualize nutrition prescription, as it is a good marker of over- or underfeeding at the different stages of disease. The RQ also informs about the patient's body's capacity to use different substrates: the variations of RQ indicating the metabolic changes revealing insufficient or excessive feeding. The different cases reflect the use of a new generation device as a metabolic monitor that should be combined with other clinical observations and laboratory biomarkers. The tutorial also points to some shortcomings of the method, proposing alternatives.

Glycine by enteral route does not improve major clinical outcomes in severe COVID-19: a randomized clinical pilot trial

There is a worrying scarcity of drug options for patients with severe COVID-19. Glycine possesses anti-inflammatory, cytoprotective, endothelium-protective, and platelet-antiaggregant properties, so its use in these patients seems promising. In this open label, controlled clinical trial, inpatients with severe COVID-19 requiring mechanical ventilation randomly received usual care (control group) or usual care plus 0.5 g/kg/day glycine by the enteral route (experimental group). Major outcomes included mortality, time to weaning from mechanical ventilation, total time on mechanical ventilation, and time from study recruitment to death. Secondary outcomes included laboratory tests and serum cytokines. Patients from experimental (n = 33) and control groups (n = 23) did not differ in basal characteristics. There were no differences in mortality (glycine group, 63.6% vs control group, 52.2%, p = 0.60) nor in any other major outcome. Glycine intake was associated with lower fibrinogen levels, either evaluated per week of follow-up (p < 0.05 at weeks 1, 2, and 4) or as weighted mean during the whole hospitalization (608.7 ± 17.7 mg/dl vs control 712.2 ± 25.0 mg/dl, p = 0.001), but did not modify any other laboratory test or cytokine concentration. In summary, in severe COVID-19 glycine was unable to modify major clinical outcomes, serum cytokines or most laboratory tests, but was associated with lower serum fibrinogen concentration.Registration: ClinicalTrials.gov NCT04443673, 23/06/2020.

Fat malabsorption in critical illness

Malnutrition in critical illness is common and is associated with significant increases in adverse outcomes. A hypermetabolic state and underfeeding both contribute to the incidence of malnutrition. Malabsorption caused by critical illness is also an important contributor to the development of malnutrition. The early provision of enteral nutrition is associated with improved outcomes. Strategies for nutrition therapy must be informed by the alterations in absorption of macronutrients present in these patients. The following review examines alterations in fat metabolism during critical illness, and its consequences to overall nutrition status. Critical illness, as well as the sequalae of common medical interventions, may lead to alterations in the mechanical and chemical processes by which fat is digested and absorbed. Mechanical alterations include delayed gastric emptying and changes to the normal gut transit time. Pharmacologic interventions aimed at reducing these impacts may themselves, negatively affect efficient fat absorption. Exocrine pancreatic insufficiency can also occur in critical illness and may be underappreciated as a cause of fat malabsorption. Dysfunction of the gut lymphatics has been proposed as a contributing factor to fat malabsorption, and additional work is needed to better describe and quantify those effects. Achieving optimal outcomes for nutrition therapy requires recognition of these alterations in fat digestion.

Administration of Free Amino Acids Improves Exogenous Amino Acid Availability when Compared with Intact Protein in Critically Ill Patients: A Randomized Controlled Study

BACKGROUND

Protein digestion and amino acid absorption appear compromised in critical illness. The provision of enteral feeds with free amino acids rather than intact protein may improve postprandial amino acid availability.

OBJECTIVE

Our objective was to quantify the uptake of diet-derived phenylalanine after the enteral administration of intact protein compared with an equivalent amount of free amino acids in critically ill patients.

METHODS

Sixteen patients who were mechanically ventilated in intensive care unit (ICU) at risk of malabsorption received a primed continuous infusion of L-[ring-2H5]-phenylalanine and L-[ring-3,5-2H2]-tyrosine after an overnight fast. Patients were randomly allocated to receive 20 g intrinsically L-[1-13C]-phenylalanine-labeled milk protein or an equivalent amount of amino acids labeled with free L-[1-13C]-phenylalanine via a nasogastric tube over a 2-h period. Protein digestion and amino acid absorption kinetics and whole-body protein net balance were assessed throughout a 6-h period.

RESULTS

After enteral nutrient infusion, both plasma phenylalanine and leucine concentrations increased (P-time < 0.001), with a more rapid and greater rise after free amino acid compared with intact protein administration (P-time × treatment = 0.003). Diet-derived phenylalanine released into the circulation was 25% greater after free amino acids compared with intact protein administration [68.7% (confidence interval {CI}: 62.3, 75.1%) compared with 43.8% (CI: 32.4, 55.2%), respectively; P < 0.001]. Whole-body protein net balance became positive after nutrient administration (P-time < 0.001) and tended to be more positive after free amino acid in provision (P-time × treatment = 0.07).

CONCLUSIONS

The administration of free amino acids as opposed to intact protein further increases postprandial plasma amino acid availability in critically ill patients, allowing more diet-derived phenylalanine to become available to peripheral tissues. This trial was registered at clinicaltrials.gov as NCT04791774.

Dose-response relationship between diarrhea quantity and mortality in critical care patients: A retrospective cohort study

BACKGROUND

Previous studies have shown that diarrhea, defined as a dichotomized cutoff, is associated with increased mortality of patients in intensive care units (ICUs). This study aimed to examine the dose-response relationship between the quantity of diarrhea and mortality in ICU patients with newly developed diarrhea.

METHODS

We conducted this single-center retrospective cohort study. We consecutively included all adult patients with newly developed diarrhea in the ICU between January 2017 and December 2018. Newly developed diarrhea was defined according to the World Health Organization definition. The consistency of diarrhea was evaluated by the Bristol stool chart scale, and the quantity of diarrhea was assessed on the day when patients newly developed diarrhea. The primary outcome was in-hospital mortality. The risk ratio (RR) and 95% confidence interval (CI) for the association between diarrhea quantity and mortality were estimated using multivariable modified Poisson regression models.

RESULTS

Among the 231 participants, 68.4% were men; the median age was 72 years. The median diarrhea quantity was 401g (interquartile range [IQR] 230‒645g), and in-hospital mortality was 22.9%. More diarrhea at baseline was associated with higher in-hospital mortality; the adjusted RR (95% CI) per 200-g increase was 1.10 (1.01‒1.20), p = 0.029. In sensitivity analyses with near quartile categories of diarrhea quantity (<250g, 250-399g, 400-649g, ≥650g), the adjusted RRs for each respective category were 1.00 (reference), 1.02 (0.51-2.04), 1.29 (0.69-2.43), and 1.77 (0.99-3.21), p for trend = 0.033.

CONCLUSIONS

A greater quantity of diarrhea was an independent risk factor for in-hospital mortality. The diarrhea quantity may be an indicator of disease severity in ICU patients.

Nutritional intake and gastro-intestinal symptoms in critically ill COVID-19 patients

BACKGROUND & AIMS

Critically ill COVID-19 patients seem hypermetabolic and difficult to feed enterally, due to gastro-intestinal (GI) symptoms such as high gastric residual volumes (GRV) and diarrhea. Our aim was to describe the association of nutritional intake and GI symptoms during first 14 days of ICU admission.

METHODS

Observational study including critically ill adult COVID-19 patients. Data on nutritional intake [enteral nutrition (EN) or parenteral nutrition] and GI symptoms were collected during 14 days after ICU admission. Target energy and protein feeding goals were calculated conform ESPEN guidelines. GI symptoms included GRV (ml/d), vomiting, abdominal distension, and faeces (ml/d). High GRV's were classified as ≥2 times ≥150 ml/d and diarrhea as Bristol stool chart ≥6. GI symptoms were defined as mild if at least one symptom occurred and as moderate when ≥2 symptoms occurred. Acute gastrointestinal injury (AGI) grades of III were classified as GI dysfunction and grades of IV were considered as GI failure with severe impact on distant organs. Linear mixed model analysis was performed to explore the development of nutritional intake and GI symptoms over time at day (D) 0, 4, 10, and 14.

RESULTS

One hundred and fifty patients were included [75% male; median age 64 years (IQR 54-70)]. BMI upon admission was 28 kg/m² (IQR 25-33), of which 43% obese (BMI > 30 kg/m²). Most patients received EN during admission (98% D4; 96% D10-14). Mean energy goals increased from 87% at D4 to 93% D10-14 and protein goals (g/kg) were increasingly achieved during admission (84% D4; 93% D10-14). Presence of moderate GI symptoms decreased (10% D0; 6% D4-10; 5% D14), reversely mild GI symptoms increased. Occurrence of GI dysfunction fluctuated (1% D0; 18% D4; 12% D10; 8% D14) and none of patients developed grade IV GI failure. Development of high GRV fluctuated (5% D0; 23% D4; 14% D10; 8% D14) and occurrence of diarrhea slightly increased during admission (5% D0; 22% D4; 25% D10; 27% D14). Linear mixed models showed only an association between AGI grades III and lower protein intake at day 10 (p = 0.020).

CONCLUSION

Occurrence of GI symptoms was limited and seems no major barrier for EN in our group of critically COVID-19 patients. Nutritional intake was just below requirements during the first 14 days of ICU admission. The effect on nutritional status remains to be studied.

A scoping review considering potential biomarkers or functional measures of gastrointestinal dysfunction and enteral feeding intolerance in critically ill adults

BACKGROUND & AIM

Enteral feeding intolerance (EFI) as a result of gastrointestinal (GI) dysfunction in critically ill adults can lead to suboptimal nutritional delivery, increasing the risk of hospital acquired malnutrition. There are no validated measures of EFI or consensus as to which measures could be used to define EFI. The aim of this scoping review is to explore the validity of biomarkers, physiological or functional measures of GI dysfunction and EFI in critically ill adults characterising their use in routine clinical practice to identify those with GI dysfunction to better guide nutritional support.

METHODS

Database searches were completed in Ovid MEDLINE, Embase, CINAHL and Web of Science using the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The search was performed until June 2022. Articles were included if they reported original studies that identify potential biomarkers or functional measures of EFI in critically ill adults. A nine-stage process was completed to extract and complete data synthesis.

RESULTS

139 unique articles were identified. Following review of titles and abstracts, 114 of these articles were excluded, three further articles were excluded after full text review and 22 articles met the inclusion criteria. A thematic analysis of the articles included identified three overarching themes of GI dysfunction: (1) Serum biomarkers, (2) Physiological markers, and (3) Functional markers. Within the category of serum biomarkers, a further three sub-categories were identified: (i) enterohormones, (ii) markers of enterocyte function, and iii) cytokines and neurotransmitters. Some associations were seen between EFI and heparin binding protein, intra-abdominal pressure, cholecystokinin and acetylcholine levels but no markers are currently suitable for daily clinical use.

CONCLUSIONS

Further larger studies are required to characterise the relationships between serum biomarkers, physiological and functional makers of GI dysfunction in critically ill adults. A robust definition of GI dysfunction should be included in any future research.

When is parenteral nutrition indicated?

The indications and contraindications of parenteral nutrition (PN) are discussed in view of recent clinical findings. For decades, PN has been restricted to patients unable to tolerate enteral nutrition (EN) intake owing to the perceived risk of severe side-effects. The evolution of the PN substrate composition and delivery of nutrition via all-in-one bags has dramatically improved the application prospects of PN. Recent studies show similar complication rates of nutrition therapy administered through enteral and intravenous routes. Therefore, indications of PN have, based on evidence, extended beyond complete gastrointestinal (GI) failure to include conditions such as insufficient EN generating persistent negative energy balance and insufficient protein intakes, malabsorption, or specific needs that are impossible to cover with EN feeds.

Gastrointestinal manifestations and possible mechanisms of COVID-19 in different periods

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, has become a pandemic worldwide. Although COVID-19 mainly affects the respiratory system, gastrointestinal (GI) manifestations have been frequently reported in such cases, even as initial symptoms. There have been several studies on different GI manifestations in patients with mild and severe disease or in remission. In this review article we summarized different GI manifestations of COVID-19 at various disease stages and the possible mechanisms based on published literatures, as well as the significance of GI manifestations in systemic inflammatory injury.

Understanding the physiology of human defaecation and disorders of continence and evacuation

The act of defaecation, although a ubiquitous human experience, requires the coordinated actions of the anorectum and colon, pelvic floor musculature, and the enteric, peripheral and central nervous systems. Defaecation is best appreciated through the description of four phases, which are, temporally and physiologically, reasonably discrete. However, given the complexity of this process, it is unsurprising that disorders of defaecation are both common and problematic; almost everyone will experience constipation at some time in their life and many will develop faecal incontinence. A detailed understanding of the normal physiology of defaecation and continence is critical to inform management of disorders of defaecation. During the past decade, there have been major advances in the investigative tools used to assess colonic and anorectal function. This Review details the current understanding of defaecation and continence. This includes an overview of the relevant anatomy and physiology, a description of the four phases of defaecation, and factors influencing defaecation (demographics, stool frequency/consistency, psychobehavioural factors, posture, circadian rhythm, dietary intake and medications). A summary of the known pathophysiology of defaecation disorders including constipation, faecal incontinence and irritable bowel syndrome is also included, as well as considerations for further research in this field.

Gastrointestinal Tolerance and Protein Absorption Markers with a New Peptide Enteral Formula Compared to a Standard Intact Protein Enteral Formula in Critically Ill Patients

The aim of this exploratory study was to investigate gastrointestinal tolerance and protein absorption markers with a new enteral peptide formula (PF) compared to an isocaloric enteral intact protein standard formula (SF) containing the same amount of protein in ICU patients. Patients admitted to a cardio-thoracic intensive care unit expected to receive tube feeding for ≥5 days were randomized to receive either PF (1.5 kcal/mL) or SF in a double-blind manner for ≤14 days. Twenty-six patients were randomized (13 SF and 13 PF) and 23 (12 SF and 11 PF) completed at least 5 days of product administration. There were no statistically significant differences between the feeds during the first 5 days of intervention for diarrhea (SF:3 (23%); PF:5 (39%), p = 0.388), vomiting (SF:1 (8%); PF:2 (15%), p = 0.549), constipation (SF:7 (54%), PF:3 (23%), p = 0.115), and high gastric residual volume (>500 mL: SF:1 (8%); PF: 2 (15%), p = 0.535). There were no differences in plasma amino acids or urinary markers of protein absorption and metabolism. In conclusion, no major differences were found in tolerability and protein absorption markers between the standard intact protein formula and the peptide formula.

Energy expenditure and feeding practices and tolerance during the acute and late phase of critically ill COVID-19 patients

BACKGROUND & AIMS

Different metabolic phases can be distinguished in critical illness, which influences nutritional treatment. Achieving optimal nutritional treatment during these phases in critically ill patients is challenging. COVID-19 patients seem particularly difficult to feed due to gastrointestinal problems. Our aim was to describe measured resting energy expenditure (mREE) and feeding practices and tolerance during the acute and late phases of critical illness in COVID-19 patients.

METHODS

Observational study including critically ill mechanically ventilated adult COVID-19 patients. Indirect calorimetry (Q-NRG+, Cosmed) was used to determine mREE during the acute (day 0-7) and late phase (>day 7) of critical illness. Data on nutritional intake, feeding tolerance and urinary nitrogen loss were collected simultaneously. A paired sample t-test was performed for mREE in both phases.

RESULTS

We enrolled 21 patients with a median age of 59 years [44-66], 67% male and median BMI of 31.5 kg/m2 [25.7-37.8]. Patients were predominantly fed with EN in both phases. No significant difference in mREE was observed between phases (p = 0.529). Sixty-five percent of the patients were hypermetabolic in both phases. Median delivery of energy as percentage of mREE was higher in the late phase (94%) compared to the acute phase (70%) (p = 0.001). Urinary nitrogen losses were significant higher in the late phase (p = 0.003).

CONCLUSION

In both the acute and late phase, the majority of the patients were hypermetabolic and fed enterally. In the acute phase patients were fed hypocaloric whereas in the late phase this was almost normocaloric, conform ESPEN guidelines. No significant difference in mREE was observed between phases. Hypermetabolism in both phases in conjunction with an increasing loss of urinary nitrogen may indicate that COVID-19 patients remain in a prolonged acute, catabolic phase.

Gut dysfunction in the ICU: diagnosis and management

PURPOSE OF REVIEW

Progress has been made in our understanding of gut dysfunction in critical illness. This review will outline new findings and give perspectives based on previous knowledge and concurrent advances in nutrition.

RECENT FINDINGS

The relationship between gut dysfunction and poor outcomes in critical illness has received considerable interest. It remains uncertain whether gut dysfunction is merely a marker of illness severity or if it is directly responsible for prolonged critical illness and increased mortality. This relationship is difficult to ascertain given there is no agreed method for identification and quantification; biomarkers such as intestinal fatty acid binding protein and citrulline show promise but require further study. Recent studies have investigated strategies to deliver enteral nutrition targets with impacts on gut function, including high calorie or protein formulae, intermittent regimes and novel prokinetics.

SUMMARY

Gut dysfunction is associated with poor outcomes, but it remains uncertain whether strategies to improve gut function will influence survival and recovery.

Effect of protein composition of enteral formula on gastric content volume during continuous feeding: A randomized controlled cross-over study in healthy adults

BACKGROUND & AIMS

Enteral nutrition with polymeric intact protein formula is the preferred medical nutrition strategy in critically ill patients when oral intake is insufficient. Enteral nutrition formulas are often rich in casein protein, which has coagulating properties. Coagulation in the stomach impedes gastric emptying and might result in high gastric residual volumes which are a clinical sign of gastrointestinal intolerance and a major reason to decrease or to discontinue enteral feeding. In this study the impact of protein composition of enteral formula on gastric content volume (GCV) during and after continuous feeding was tested in healthy volunteers in whom gastrointestinal conditions of critically ill patients were mimicked.

METHODS

An enteral formula including 4 proteins (P4) with non-coagulating properties was compared to a casein-dominant formula (Cas) with coagulating properties. Esomeprazole and codeine were administered to mimic stress ulcer prophylaxis and induce gastroduodenal motor dysfunction, both being hallmarks of critically ill patients. GCV was measured with magnetic resonance imaging during and after continuous enteral feeding (100 mL/h for 4h) in a randomized single-center cross-over study. Results are provided as mean (SD). Significance level of p < 0.05 was applied.

RESULTS

Twenty subjects completed the study (14 women, 6 men, 25.8 (4.6) years old, BMI: 22.5 (1.5) kg/m²). The GCV as change from baseline at T = 240 (primary endpoint) did not differ between study products (P4: 124.3 (83.4) vs. Cas: 137.1 (102.0) mL, 95% CI: -57.4, 27.0, p = 0.457). During feeding and after cessation of feeding, the area under the GCV-curve (AUC_0-360 GCV) for P4 and Cas was 44631.1 (15546.1) and 52822.2 (19686.1) mL∗min, respectively (p = 0.061). During feeding the GCV was lower at T = 180 min (175.4 (64.8) vs. 205.2 (75.4) mL, p = 0.038) and after cessation of feeding at T = 300 min (81.3 (71.1) vs. 116.3 (84.3) mL, p = 0.004) and T = 330 min (39.9 (53.9) vs. 73.6 (81.1) mL, p = 0.031). With P4 it took less time to reach half of the GCV at T = 240 min compared to Cas (52.8 (27.6) vs. 65.4 (29.9) min, p = 0.020).

CONCLUSIONS

In this study in which healthy volunteers received esomeprazole and codeine to mimic gastrointestinal conditions of critically ill patients, observations of secondary endpoints suggest faster gastric emptying with P4 compared to Cas, and less gastric accumulation, possibly due to the non-coagulating properties of the P4 protein blend. Considering the small effect and the possible clinical relevance of reduced intragastric accumulation of enteral nutrition, the potential impact of protein coagulation should be further investigated in relevant study populations. Registered under Netherlands Trial Register identifier no. NTR6423.

Diarrhea and elevation of plasma markers of cholestasis are common and often occur concomitantly in critically ill patients

PURPOSE

We aimed to describe epidemiology of diarrhea and cholestasis in critically ill patients and explore associations between these two conditions.

MATERIAL AND METHODS

We performed a retrospective study including all consecutive patients who stayed in the ICU for at least 3 days and in whom plasma measurements of liver enzymes/cholestasis parameters were performed. Diarrhea was defined as 3 or more loose or liquid stools per day and cholestasis as increase of alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (GGT) 1.5 times above the upper limit of normality.

RESULTS

Diarrhea was observed in 26.1% and cholestasis in 27.9% of study patients, about one third of the cases in both diarrhea and cholestasis occurred beyond the first week of patient's ICU stay. Cholestasis occurred in 45.6% of patients with diarrhea vs 28.0% of patients without diarrhea (p < 0.001). In 94 patients (13.1%) both diarrhea and cholestasis occurred, cholestasis was more commonly (2/3 of cases) documented before manifestation of diarrhea.

CONCLUSIONS

Cholestasis is more common in patients with diarrhea and vice versa. Diarrhea and cholestasis both occur in approximately one quarter of ICU patients, with significant proportion manifesting beyond the first week in the ICU.

Measures of Dietary Fat and Energy Absorption in Healthy Adults

OBJECTIVES

Existing reference ranges for stool fat and energy absorption were developed using subjects in controlled environments on precise diets. This study measured energy and fat absorption in healthy, community-dwelling adults eating a moderate-to-high fat American diet via stool- and serum-based methods.

METHODS

This was a secondary analysis of healthy subjects recruited as the comparison group in a chronic pancreatitis study. Subjects recorded dietary intake and collected stool over 3-day periods. Stool was analyzed for fat content using the coefficient of fat absorption and for energy content using bomb calorimetry. The malabsorption blood test (MBT) was used to measure dietary fat absorption.

RESULTS

Nineteen subjects had mean daily stool measures of 143 g wet weight, 4.1 g of fat, and 178 kcal. The mean coefficients of fat and energy absorption were 96% and 93%, respectively. The mean MBT area under the curve cut-point was greater than 8 mg·h/dL.

CONCLUSIONS

This study confirms the historical reference range for the coefficient of fat absorption in contemporary healthy, community-dwelling adults on a moderate-to-high fat diet. The study contributes to the development of reference range values for multiple bomb calorimetry-based outcomes of stool energy losses and to the serum-based MBT as a promising method for measuring fat absorption.

Impact of a natural versus commercial enteral-feeding on the occurrence of diarrhea in critically ill cardiac surgery patients. A retrospective cohort study

BACKGROUND

Diarrhea is an important complication in critically ill patients undergoing enteral feeding. The occurrence of diarrhea may lead to systemic and local complications and negatively impacts on nursing workload and patient's wellbeing. An enteral feeding based on blenderized natural food could be beneficial in reducing the risk of diarrhea. No study has compared natural and commercial enteral feedings in critically ill cardiac surgery patients.

OBJECTIVE

The aim of this study was to compare the risk of diarrhea occurrence in two cohorts of patients fed a blenderized natural food diet or commercial enteral feeding preparations, respectively.

DESIGN

Retrospective cohort study.

SETTING

Cardiac-Surgery Intensive Care Unit of a University Hospital.

PARTICIPANTS

Two-hundred and fifteen patients admitted to the postoperative cardiac surgery intensive care unit were included, 103 fed blenderized natural enteral feeding and 112 fed commercial formulas.

METHODS

Commercial enteral formulas were delivered by continuous pump administration, while natural enteral feeding by bolus 3 times per day. Diarrhea was documented in the presence of three or more evacuations of loose or watery stool (or an amount above 250 ml) per day. The presence of diarrhea was recorded daily from the beginning to the end of the enteral feeding, up to a maximum of 8 days. The unadjusted time to the first event of diarrhea between the two enteral feeding groups was compared. Adjusted comparison was then performed by fitting a multivariable Cox Proportional-Hazards model, adjusted for potential confounders for diarrhea occurrence (i.e. administration of inotropes, vasopressors, prokinetics, antibiotics, oral nutritional supplements, antifungal agents, sedatives, opioids, probiotics, laxatives).

RESULTS

In unadjusted survival analysis the probability of diarrhea was significantly lower in the natural enteral feeding group (log rank test: p = 0.023). In the multivariable model patients in natural enteral feeding cohort showed a non-significant trend towards an almost halved risk of experiencing diarrhea (hazard ratio: 0.584; 95% confidence interval: 0.335-1.018; p = 0.058) compared to those fed commercial enteral feeding.

CONCLUSIONS

Administration of a blenderized diet based on natural food for enteral feeding can reduce the incidence of diarrhea in cardiac surgery critically ill patients. This strategy may reduce the risk of diarrhea-associated malnutrition and systemic and local complications, also having a positive impact on nursing workload and patient wellbeing.

Gastrointestinal dysfunction in the critically ill: a systematic scoping review and research agenda proposed by the Section of Metabolism, Endocrinology and Nutrition of the European Society of Intensive Care Medicine

BACKGROUND

Gastrointestinal (GI) dysfunction is frequent in the critically ill but can be overlooked as a result of the lack of standardization of the diagnostic and therapeutic approaches. We aimed to develop a research agenda for GI dysfunction for future research. We systematically reviewed the current knowledge on a broad range of subtopics from a specific viewpoint of GI dysfunction, highlighting the remaining areas of uncertainty and suggesting future studies.

METHODS

This systematic scoping review and research agenda was conducted following successive steps: (1) identify clinically important subtopics within the field of GI function which warrant further research; (2) systematically review the literature for each subtopic using PubMed, CENTRAL and Cochrane Database of Systematic Reviews; (3) summarize evidence for each subtopic; (4) identify areas of uncertainty; (5) formulate and refine study proposals that address these subtopics; and (6) prioritize study proposals via sequential voting rounds.

RESULTS

Five major themes were identified: (1) monitoring, (2) associations between GI function and outcome, (3) GI function and nutrition, (4) management of GI dysfunction and (5) pathophysiological mechanisms. Searches on 17 subtopics were performed and evidence summarized. Several areas of uncertainty were identified, six of them needing consensus process. Study proposals ranked among the first ten included: prevention and management of diarrhoea; management of upper and lower feeding intolerance, including indications for post-pyloric feeding and opioid antagonists; acute gastrointestinal injury grading as a bedside tool; the role of intra-abdominal hypertension in the development and monitoring of GI dysfunction and in the development of non-occlusive mesenteric ischaemia; and the effect of proton pump inhibitors on the microbiome in critical illness.

CONCLUSIONS

Current evidence on GI dysfunction is scarce, partially due to the lack of precise definitions. The use of core sets of monitoring and outcomes are required to improve the consistency of future studies. We propose several areas for consensus process and outline future study projects.

Quantification of diacylglycerol and triacylglycerol species in human fecal samples by flow injection Fourier transform mass spectrometry

The intestinal microbiome plays an important role in human health and disease and fecal materials reflect the microbial activity. Thus, analysis of fecal metabolites provides insight in metabolic interactions between gut microbiota and host organism. In this work, we applied flow injection analysis coupled to Fourier transform mass spectrometry (FIA-FTMS) to identify and quantify lipid species in human fecal samples. Fecal homogenates were subjected to lipid extraction and analyzed by FIA-FTMS. The analysis of different subjects revealed a vast heterogeneity of lipid species abundance. The majority of samples displayed prominent signals of triacylglycerol (TG) and diacylglycerol (DG) species that could be verified by MS2 spectra. Therefore, we focused on the quantification of TG and DG. Method validation included limit of quantification, linearity, evaluation of matrix effects, recovery, and reproducibility. The validation experiments demonstrated the suitability of the method, with exception for approximately 10% of samples, where we observed coefficients of variation higher than 15%. Impaired reproducibility was related to sample inhomogeneity and could not be improved by additional sample preparation steps. Additionally, these experiments demonstrated that compared with aqueous samples, samples containing isopropanol showed higher amounts of DG, presumably due to lysis of bacteria and increased TG lipolysis. These effects were sample-specific and substantiate the high heterogeneity of fecal materials as well as the need for further evaluation of pre-analytic conditions. In summary, FIA-FTMS offers a fast and accurate tool to quantify DG and TG species and is suitable to provide insight into the fecal lipidome and its role in health and disease.

Acute Intestinal Failure

Acute intestinal failure (AIF), "reduction of gut function below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, requiring parenteral nutrition", is common, but very often neglected part of multiorgan dysfunction syndrome (MODS) in the critically ill patients. It is now increasingly being recognized as a cause of prolonged ICU and hospital stay and poor outcome. Multidisciplinary team approach, systematic approach to management with treatment of sepsis, early mobilization and enteral feeding with prokinetics if required, control of intra-abdominal pressure and surgical intervention, when mandated, can help treat AIF and improve patient outcomes. How to cite this article: Chandankhede SR, Kulkarni AP. Acute Intestinal Failure. Indian J Crit Care Med 2020;24(Suppl 4):S168-S174.

Enteral tolerance in critically ill patients

Enteral nutrition (EN) can maintain the structure and function of the gastrointestinal mucosa better than parenteral nutrition. In critically ill patients, EN must be discontinued or interrupted, if gastrointestinal complications, particularly vomiting and bowel movement disorders, do not resolve with appropriate management. To avoid such gastrointestinal complications, EN should be started as soon as possible with a small amount of EN first and gradually increased. EN itself may also promote intestinal peristalsis. The measures to decrease the risk of reflux and aspiration include elevation the head of the bed (30° to 45°), switch to continuous administration, administration of prokinetic drugs or narcotic antagonists to promote gastrointestinal motility, and switch to jejunal access (postpyloric route). Moreover, the control of bowel movement is also important for intensive care and management. In particular, prolonged diarrhea can cause deficiency in nutrient absorption, malnutrition, and increase in mortality. In addition, diarrhea may cause a decrease the circulating blood volume, metabolic acidosis, electrolyte abnormalities, and contamination of surgical wounds and pressure ulcers. If diarrhea occurs in critically ill patients on EN management, it is important to determine whether diarrhea is EN-related or not. After ruling out the other causes of diarrhea, the measures to prevent EN-related diarrhea include switch to continuous infusion, switch to gastric feeding, adjustment of agents that improve gastrointestinal peristalsis or laxative, administration of antidiarrheal drugs, changing the type of EN formula, and semisolidification of EN formula. One of the best ways to success for EN management is to continue as long as possible without interruption and discontinuation of EN easily by appropriate measures, even if gastrointestinal complications occur.

The effect of enteral versus parenteral nutrition for critically ill patients: A systematic review and meta-analysis

STUDY OBJECTIVE

To analyze the effect of enteral nutrition compared with parenteral nutrition in critically ill patients.

DESIGN

Systematic review and meta-analysis of randomized controlled trials.

SETTING

Intensive care unit.

PATIENTS

23 trials containing 6478 patients met our inclusion criteria.

INTERVENTION

A systematical literature search was conducted to identify eligible trials in electronic databases including PubMed, Embase, Scopus, EBSCO and Cochrane Library. The primary outcome was mortality, the secondary outcomes were gastrointestinal complications, bloodstream infections, organ failures, length of stay in ICU and hospital. We performed a predefined subgroup analyses to explore the treatment effect by mean age, publication date and disease types.

MAIN RESULTS

The result showed no significant effect on overall mortality rate (OR 0.98, 95%CI 0.81 to 1.18, P = 0.83, I² = 19%) and organ failure rate (OR 0.87, 95%CI 0.75 to 1.01, P = 0.06, I² = 16%). The use of EN had more beneficial effects with fewer bloodstream infections when compared to PN (OR 0.59, 95%CI 0.43 to 0.82, P = 0.001, I² = 27%) and this was more noteworthy in the subgroup analysis for critical surgical patients (OR 0.36, 95%CI 0.22 to 0.59, P < 0.0001, I² = 0%). EN was associated with reduction in hospital LOS (MD -0.90, 95%CI -1.63 to -0.17, P = 0.21, I² = 0%) but had an increase incidence of gastrointestinal complications (OR 2.00, 95%CI 1.76 to 2.27, P < 0.00001, I² = 0%).

CONCLUSION

For critically ill patients, the two routes of nutrition support had no different effect on mortality rate. The use of EN could decrease the incidence of bloodstream infections and reduce hospital LOS but was associated with increased risk of gastrointestinal complications.

Incidence of diarrhea and associated risk factors in patients with traumatic brain injury and enteral nutrition

To determine the occurrence of diarrhea and associated factors in critically ill patients with traumatic brain injury (TBI) in use of nutritional therapy. Prospective cohort study conducted in an Intensive Care Unit (ICU) of a General Hospital reference in trauma. We evaluated TBI patients who stayed less than 72 h in the ICU, who were using EN for at least 48 h. Definition of diarrhea it was considered three or more episodes of liquid stools or semi-liquid at 24 h. For analysis were evaluated demographic, epidemiological, clinical and nutritional data. Twenty-three patients were evaluated, being 86.9% male, median 33 years old (IQR = 25-52 years) and 16-day ICU stay (IQR = 10-26 days). Diarrhea occurred in 69.6% of the patients and they had a longer time in the ICU (p = 0.007). All patients who used combination prokinetic therapy (metoclopramide and erythromycin) and used antibiotics for more than 8 days had diarrhea (p = 0.057 and p = 0.007, respectively). The incidence of diarrhea was high in TBI patients with enteral nutrition and was associated with the use of antibiotics for more than one week.

Natural Bioactive Food Components for Improving Enteral Tube Feeding Tolerance in Adult Patient Populations

Tube feeding (TF) is the most common form of nutrition support. In recent years, TF administration has increased among patient populations within and outside hospital settings, in part due to greater insurance coverage, reduced use of parenteral nutrition, and improved formularies suitable for sole source nutrition. With increasing life expectancy and improved access to TFs, the number of adults dependent on enteral nutrition is expected to grow. However, enteral TF intolerance (ETFI) is the most common complication of TFs, typically presenting with at least 1 adverse gastrointestinal event, including nausea, diarrhea, and constipation. ETFI often leads to reductions in TF volume with associated energy and protein deficits. Potentially ensuing malnutrition is a major public health concern due its effects on increased risk of morbidity and mortality, infections, prolonged hospital length of stay, and higher healthcare costs. As such, there is a need for intervention strategies to prevent and reduce ETFI. Incorporating whole foods with bioactive properties is a promising strategy. Emerging research has elucidated bioactive properties of whole foods with specific benefits for the prevention and management of adverse gastrointestinal events commonly associated with TFs. However, lack of evidence-based recommendations and technological challenges have limited the use of such foods in commercial TF formulas. This review addresses research gaps by discussing 5 whole foods (rhubarb, banana, curcumin, peppermint oil, and ginger) with bioactive attributes identified through literature searches and clinical experience as having substantial scientific rationale to consider their application for ETFI in adult populations.

Early or Late Feeding after ICU Admission?

The feeding of critically ill patients has recently become a controversial issue, as several studies have provided unexpected and contradictory results. Earlier beliefs regarding energy requirements in critical illness-especially during the initial phase-have been challenged. In the current review, we summarize existing evidence about fasting and the impact of early vs. late feeding on the sick organism's responses. The most important points are the non-nutritional advantages of using the intestine, and recognition that early endogenous energy production as an important player in the response must be integrated in the nutrient prescription. There is as of yet no bedside tool to monitor dynamics in metabolism and the magnitude of the endogenous energy production. Hence, an early "full-feeding strategy" exposes patients to involuntary overfeeding, due to the absence of an objective measure enabling the adjustment of the nutritional therapy. Suggestions for future research and clinical practice are proposed.

Protein calorie malnutrition, nutritional intervention and personalized cancer care

Cancer patients often experience weight loss caused by protein calorie malnutrition (PCM) during the course of the disease or treatment. PCM is expressed as severe if the patient has two or more of the following characteristics: obvious significant muscle wasting, loss of subcutaneous fat; nutritional intake of <50% of recommended intake for 2 weeks or more; bedridden or otherwise significantly reduced functional capacity; weight loss of >2% in 1 week, 5% in 1 month, or 7.5% in 3 months. Cancer anorexia-cachexia syndrome (CACS) is a multifactorial condition of advanced PCM associated with underlying illness (in this case cancer) and is characterized by loss of muscle with or without loss of fat mass. Cachexia is defined as weight loss of more than 5% of body weight in 12 months or less in the presence of chronic disease. Hence with a chronic illness on board even a small amount of weight loss can open the door to cachexia. These nutritional challenges can lead to severe morbidity and mortality in cancer patients. In the clinic, the application of personalized medicine and the ability to withstand the toxic effects of anti-cancer therapies can be optimized when the patient is in nutritional homeostasis and is free of anorexia and cachexia. Routine assessment of nutritional status and appropriate intervention are essential components of the effort to alleviate effects of malnutrition on quality of life and survival of patients.

Effect of the route of nutrition and L-alanyl-L-glutamine supplementation in amino acids' concentration in trauma patients

PURPOSE

Our purpose was to assess the amino acids' (AAs) profile in trauma patients and to assess the effect of the route of nutrition and the exogenous ALA-GLN dipeptide supplementation on plasma AAs' concentration.

METHODS

This is a secondary analysis of a previous randomized controlled trial. On day 1 and day 6 after trauma, plasma concentration of 25 AAs was measured using reverse phase high-performance liquid chromatography. Results were analyzed in relation to the route of nutrition and supplementation of ALA-GLN dipeptide. Differences between plasma AAs' concentrations at day 1 and day 6 were evaluated using the Student's t test or Mann-Whitney-Wilcoxon test. One-way ANOVA and the Kruskal-Wallis test were used to compare groups. A two-sided p value less than 0.05 was considered statistically significant.

RESULTS

Ninety-eight patients were analyzed. Mean plasma concentrations at day 1 were close to the lower normal level for most AAs. At day 6 we found an increase in the eight essential AAs' concentrations and in 9 out of 17 measured non-essential AAs. At day 6 we found no differences in plasma concentrations for the sum of all AAs (p = .72), glutamine (p = .31) and arginine (p = .23) distributed by the route of nutrition. Administration of ALA-GLN dipeptide increased the plasma concentration of alanine (p = .004), glutamine (p < .001) and citrulline (p = .006).

CONCLUSIONS

We found an early depletion of plasma AAs' concentration which partially recovered at day 6, which was unaffected by the route of nutrition. ALA-GLN dipeptide supplementation produced a small increase in plasma levels of glutamine and citrulline.

Effects of two different glutamine-containing enteral supplements on stool frequency and density in elderly patients recovering from acute critical illness

AIM

Glutamine has various beneficial functions in the gastrointestinal tract. The present study was designed to investigate the effect of two different glutamine supplements on bowel movement at the start of enteral feeding in elderly inpatients.

METHODS

This was a double-blind, prospective, randomized comparison study. A total of 25 patients aged >75 years recovering from a critical illness in a non-intensive care unit and scheduled for tube feeding were recruited. Of them, 22 consenting patients were randomly assigned to two groups: glutamine-fiber-oligosaccharide treatment group (n = 11) and glutamine F treatment group (n = 11). They were given glutamine three times daily at a dosage of 9 g/day. Enteral nutrition was given at the same dosage to both groups for the duration of the study. The end-points were stool frequency, Bristol Scale Form Score, bowel function index (Bristol Scale Form Score × stool frequency), the percentage of patients with stool frequency over three per day and those with a BSFS of 6 or 7 in each group.

RESULTS

There were no significant differences between the two groups in terms of patient characteristics before the study. All the end-points in the glutamine F group were significantly lower than those in the glutamine-fiber-oligosaccharide group.

CONCLUSIONS

Compared with glutamine-fiber-oligosaccharide, glutamine F administration resulted in stool hardening and reduced stool frequency in elderly inpatients recovering from acute critical illness in non-intensive care units. The effects might be caused by the different additive components of glutamine supplements. Geriatr Gerontol Int 2017; 17: 2514-2519.

Intravenous citrulline generation test to assess intestinal function in intensive care unit patients

Background

Assessment of a quantifiable small intestinal function test is cumbersome. Fasting citrulline concentrations have been proposed as a measure of enterocyte function and elaborated into a citrulline generation test (CGT), which is applicable only when glutamine is administered orally. CGT is an oral test, limiting its use, for example, in critically ill patients.

Objective

Assessment of normative values and feasibility of an intravenously performed CGT in intensive care unit (ICU) patients with presumed gastrointestinal motility disturbances, especially when performed intravenously.

Design

CGT reference values were determined in 16 stable ICU patients using two different CGT methods, namely following either enteral or intravenous glutamine administration and both with simultaneous arterial and venous plasma citrulline sampling at six time-points. Plasma amino acid analysis was performed using reverse-phase high-performance liquid chromatography.

Results

The median total generation of citrulline in 90 min (CGT iAUCT90) was markedly higher with arterial citrulline sampling compared with venous citrulline sampling, being 724±585 and 556±418 µmol/L/min for enteral glutamine, respectively (p=0.02) and 977±283 and 769±231 µmol/L/min for intravenous glutamine, respectively (p=0.0004). The median slope (time-dependent increase) for plasma arterial and venous citrulline during the CGT was 0.20±0.16 and 0.18±0.12 µmol/L/min for enteral glutamine, respectively (p=0.004) and 0.22±0.16 and 0.19±0.05 µmol/L/min for intravenous glutamine, respectively (p=0.02).

Conclusion

Intravenous glutamine administration combined with arterial plasma citrulline sampling yielded the least variation in CGT characteristics in stable ICU patients. A 2-point measurement test had comparable test characteristics as a 6-point measurement CGT and seems promising.

Microwaving human faecal sludge as a viable sanitation technology option for treatment and value recovery - A critical review

The prolonged challenges and terrible consequences of poor sanitation, especially in developing economies, call for the exploration of new sustainable sanitation technologies. Such technologies must be: capable of effectively treating human faecal wastes without any health or environmental impacts; scalable to address rapid increases in population and urbanization; capable of meeting environmental regulations and standards for faecal management; and competitive with existing strategies. Further and importantly, despite its noxiousness and pathogenic load, the chemical composition of human faecal sludge indicates that it could be considered a potentially valuable, nutrient-rich renewable resource, rather than a problematic waste product. New approaches to faecal sludge management must consequently seek to incorporate a 'valuable resource recovery' approach, compatible with stringent treatment requirements. This review intends to advance the understanding of human faecal sludge as a sustainable organic-rich resource that is typically high in moisture (up to 97 per cent), making it a suitable candidate for dielectric heating, i.e. microwave irradiation, to promote faecal treatment, while also recovering value-added products such as ammonia liquor concentrate (suitable for fertilizers) and chars (suitable for fuel) - which can provide an economic base to sustain the technology. Additionally, microwaving human faecal sludge represents a thermally effective approach that can destroy pathogens, eradicate the foul odour associated human faecal sludge, while also preventing hazardous product formations and/or emissions, aside from other benefits such as improved dewaterability and heavy metals recovery. Key technological parameters crucial for scaling the technology as a complementary solution to the challenges of onsite sanitation are also discussed.

Gastrointestinal failure in the ICU

PURPOSE OF REVIEW

The current review summarizes different aspects of assessment of gastrointestinal function and provides a practical approach to management of adult patients with gastrointestinal dysfunction in the ICU.

RECENT FINDINGS

Different ways to define gastrointestinal failure have been used in the past. Recently, the term 'acute gastrointestinal injury (AGI)' has been proposed to specifically describe gastrointestinal dysfunction as a part of multiple organ dysfunction syndrome. Possible pathophysiological mechanisms and different aspects in assessment of gastrointestinal function in adult ICU patients are presented. Currently, there is no single marker that could reliably describe gastrointestinal dysfunction. Therefore, monitoring and management is still based on complex assessment of different gastrointestinal symptoms and feeding intolerance, even though this approach includes a large amount of subjectivity. The possible role of biomarkers (citrulline, enterohormones, etc.) and additional parameters like intra-abdominal pressure remains to be clarified.

SUMMARY

Defining gastrointestinal failure remains challenging but broad consensus needs to be reached and disseminated soon to allow conduct of interventional studies. A systematic approach to management of gastrointestinal problems is recommended.

Diarrhea in Critically Ill Patients: The Role of Enteral Feeding

This tutorial presents a systematic approach to the management of diarrhea in the critical care setting. Diarrhea is a common and prevalent problem in critically ill patients. Despite the high prevalence, its management is far from simple. Professionals are confronted with a myriad of definitions based on frequency, consistency, and volume. The causes are complex and multifactorial, yet enteral tube feeding formula is believed to be the perpetrator. Potential causes for diarrhea are discussed, and 3 case reports provide context to examine the treatment from a nutrition perspective. Each scenario is comprehensively addressed discussing potential causes and providing specific clinical strategies contributing to improved bowel function in this patient group. The approach used for diarrhea management is based on a complete understanding of enteral tube formula, their composition, and their impact in the presence of gut dysfunction. Choosing the right feeding formula may positively influence bowel function and contribute to improved nutrition.

Effect of Critical Illness on Triglyceride Absorption

BACKGROUND

Adequate nutrition support for critically ill patients optimizes outcome, and enteral feeding is the preferred route of nutrition. Small intestinal glucose absorption is frequently impaired in critical illness. Despite lipid being a major constituent of liquid nutrient administered, there is little information about lipid absorption during critical illness.

OBJECTIVES

To determine small intestinal lipid, as well as glucose, absorption in critical illness compared with health.

MATERIALS AND METHODS

Twenty-nine mechanically ventilated critically ill patients and 16 healthy volunteers were studied. Liquid nutrient (60 mL, 1 kcal/mL), containing 200 µL (13)C-triolein and 3 g 3-O-methyl-glucose (3-OMG), was infused directly into the duodenum at a rate of 2 kcal/min. Exhaled (13)CO2 and serum 3-OMG concentrations were measured at timed intervals over 360 minutes. Lipid absorption was measured as the cumulative percentage dose (cPDR) of (13)CO2 recovered at 360 minutes. Glucose absorption was measured as the area under the 3-OMG concentration curve. Data are median (range) and analyzed using the Mann-Whitney U and Pearson correlation tests.

RESULTS

Lipid absorption was markedly less in the critically ill (cPDR(13)CO2: patients, 22.6% [0%-100%] vs healthy participants, 40.7% [5.3%-84.7%]; P = .018). While glucose absorption was less at 60 minutes in the critically ill (3-OMG60: 13.2 [3.5-29.5] vs 21.1 [9.3-31.9] mmol/L·min; P = .003), this was not apparent at 360 minutes (3-OMG360: 92.7 [54.5-147.9] vs 107.9 [64.0-168.7] mmol/L·min; P = .126). There was no relationship between lipid and glucose absorption.

CONCLUSION

Small intestinal absorption of lipid is diminished during critical illness.

The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology

The safe disposal of human excreta is of paramount importance for the health and welfare of populations living in low income countries as well as the prevention of pollution to the surrounding environment. On-site sanitation (OSS) systems are the most numerous means of treating excreta in low income countries, these facilities aim at treating human waste at source and can provide a hygienic and affordable method of waste disposal. However, current OSS systems need improvement and require further research and development. Development of OSS facilities that treat excreta at, or close to, its source require knowledge of the waste stream entering the system. Data regarding the generation rate and the chemical and physical composition of fresh feces and urine was collected from the medical literature as well as the treatability sector. The data were summarized and statistical analysis was used to quantify the major factors that were a significant cause of variability. The impact of this data on biological processes, thermal processes, physical separators, and chemical processes was then assessed. Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day. Fecal output in healthy individuals was 1.20 defecations per 24 hr period and the main factor affecting fecal mass was the fiber intake of the population. Fecal wet mass values were increased by a factor of 2 in low income countries (high fiber intakes) in comparison to values found in high income countries (low fiber intakes). Feces had a median pH of 6.64 and were composed of 74.6% water. Bacterial biomass is the major component (25-54% of dry solids) of the organic fraction of the feces. Undigested carbohydrate, fiber, protein, and fat comprise the remainder and the amounts depend on diet and diarrhea prevalence in the population. The inorganic component of the feces is primarily undigested dietary elements that also depend on dietary supply. Median urine generation rates were 1.42 L/cap/day with a dry solids content of 59 g/cap/day. Variation in the volume and composition of urine is caused by differences in physical exertion, environmental conditions, as well as water, salt, and high protein intakes. Urine has a pH 6.2 and contains the largest fractions of nitrogen, phosphorus, and potassium released from the body. The urinary excretion of nitrogen was significant (10.98 g/cap/day) with urea the most predominant constituent making up over 50% of total organic solids. The dietary intake of food and fluid is the major cause of variation in both the fecal and urine composition and these variables should always be considered if the generation rate, physical, and chemical composition of feces and urine is to be accurately predicted.

Nutritional support in critical illness and recovery

An adequate nutritional status is crucial for optimum function of cells and organs, and for wound healing. Options for artificial nutrition have greatly expanded in the past few decades, but have concomitantly shown limitations and potential side-effects. Few rigorous randomised controlled trials (RCTs) have investigated enteral or parenteral nutritional support, and evidence-based clinical guidance is largely restricted to the first week of critical illness. In the early stages of critical illness, whether artificial feeding is better than no feeding intervention has been given little attention in existing RCTs. Expected beneficial effects of various forms of early feeding interventions on rates of morbidity or mortality have generally not been supported by results of recent high-quality RCTs. Thus, whether nutritional interventions early in an intensive care unit (ICU) stay improve outcomes remains unclear. Trials assessing feeding interventions that continue after the first week of critical illness and into the post-ICU and post-hospital settings are clearly needed. Although acute morbidity and mortality will remain important safety parameters in such trials, primary outcomes should perhaps, in view of the adjunctive nature of nutritional intervention in critical illness, be focused on physical function and assessed months or even years after patients are discharged from the ICU. This Series paper is based on results of high-quality RCTs and provides new perspectives on nutritional support during critical illness and recovery.

Enteral Nutrition for Adults in the Hospital Setting

In patients unable to tolerate oral intake, multiple options of nutrient delivery are available to the clinician. Administration of enteral nutrition (EN) has long been considered the standard of care for nutrition support among patients unable to meet energy and protein requirements orally. Healthcare practitioners must make careful decisions related to ordering, administering, and monitoring EN therapy. In the hospital setting, the registered dietitian is a key resource in enteral formula selection and method of administration, monitoring for and troubleshooting EN-related complications, and transitioning to oral feeding. The hospital setting also presents many unique challenges in providing optimal nutrition to the enterally fed patient.

Effect of enteral diet enriched with eicosapentaenoic acid, gamma-linolenic acid, and antioxidants in patients with sepsis-induced acute respiratory distress syndrome

Background

In this study, the effects of an enteral diet enriched with eicosapentaenoic acid (EPA), γ-linolenic acid (GLA), and antioxidants were compared with a standard enteral diet in critically ill patients with sepsis-induced acute respiratory distress syndrome (ARDS).

Methods

This study was a single-center, prospective, randomized, single-blind, controlled trial in our Advanced Critical Care Center. Patients were randomized to receive a continuous EPA, GLA, and antioxidant-enriched diet (study group), or an isocaloric standard diet (control group).

Results

Twenty-three of 46 patients were in the study group, and the other 23 were in the control group. Duration of mechanical ventilation, incidence of new nosocomial infections, changes over time in Sequential Organ Failure Assessment (SOFA) scores, and 60-day mortality were not significantly different between the two groups. The ratio of partial pressure of oxygen to fraction of inspired oxygen on day 7 was significantly higher in the study group (233.0 [185.5–282.8] vs. 274.0 [225.5–310.8], p = 0.021). Duration of ICU stay was significantly shorter in the study group than in the control group (24.0 [20.0–30.0] vs. 15.0 [11.0–24.0], p = 0.008).

Conclusions

An enteral diet enriched with EPA, GLA, and antioxidants did not improve duration of mechanical ventilation, SOFA score, incidence of new nosocomial infections, or mortality but did favorably influence duration of ICU stay in critically ill patients with sepsis-induced ARDS.

Electronic supplementary material

The online version of this article (doi:10.1186/s40560-015-0087-2) contains supplementary material, which is available to authorized users.

Gastrointestinal dysfunction relating to the provision of nutrition in the critically ill

PURPOSE OF REVIEW

During critical illness, enteral nutrition remains central to clinical care and an understanding of gut dysfunction is therefore important. Contemporary data have contributed to our knowledge in this area and this review will concentrate on recently published studies.

RECENT FINDINGS

It is difficult to precisely measure gastric emptying and nutrient absorption as part of routine clinical care. However, techniques for the measurement of these parameters for research purposes have been refined, studied and validated. These methodologies allow the evaluation of novel treatments that modulate gastric emptying. Quantification and an understanding of the mechanisms of nutrient malabsorption may facilitate the development of therapeutic agents to improve absorption and/or formulae, which are more readily absorbed, thereby improving nutritional and clinical outcomes.

SUMMARY

Improved understanding of gut pathophysiology in critical illness provides opportunities for the development and testing of novel and targeted treatment strategies, with the objective to improve clinical outcomes in this group.

Rapid normalization of vitamin D levels: a meta-analysis

BACKGROUND

Vitamin D deficiency may represent a modifiable risk factor to improve outcome in severe illness. The efficacy of high-dose regimens in rapid normalization of vitamin D levels is uncertain.

METHODS

We conducted a systematic review of pediatric clinical trials administering high-dose vitamin D to evaluate 25-hydroxyvitamin D (25[OH]D) response and characteristics associated with final 25(OH)D levels by using Medline, Embase, and the Cochrane Central Register of Controlled Trials, including reference lists of systematic reviews and eligible publications. Uncontrolled and controlled trials reporting 25(OH)D levels after high-dose (≥1000 IU) ergocalciferol or cholecalciferol were selected. Two reviewers independently extracted and verified predefined data fields.

RESULTS

We identified 88 eligible full-text articles. Two of 6 studies that administered daily doses approximating the Institute of Medicine's Tolerable Upper Intake Level (1000-4000 IU) to vitamin D-deficient populations achieved group 25(OH)D levels >75 nmol/L within 1 month. Nine of 10 studies evaluating loading therapy (>50 000 IU) achieved group 25(OH)D levels >75 nmol/L. In meta-regression, baseline 25(OH)D, regimen type, dose, age, and time factors were associated with final 25(OH)D levels. Adverse event analysis identified increased hypercalcemia risk with doses >400 000 IU, but no increased hypercalcemia or hypercalciuria with loading doses <400 000 IU (or 10 000 IU/kg). Few studies in adolescents evaluated loading dose regimens >300 000 IU.

CONCLUSIONS

Rapid normalization of vitamin D levels is best achieved by using loading therapy that considers disease status, baseline 25(OH)D, and age (or weight). Loading doses >300 000 IU should be avoided until trials are conducted to better evaluate risk and benefit.

Proteins and amino acids are fundamental to optimal nutrition support in critically ill patients

Proteins and amino acids are widely considered to be subcomponents in nutritional support. However, proteins and amino acids are fundamental to recovery and survival, not only for their ability to preserve active tissue (protein) mass but also for a variety of other functions. Understanding the optimal amount of protein intake during nutritional support is therefore fundamental to appropriate clinical care. Although the body adapts in some ways to starvation, metabolic stress in patients causes increased protein turnover and loss of lean body mass. In this review, we present the growing scientific evidence showing the importance of protein and amino acid provision in nutritional support and their impact on preservation of muscle mass and patient outcomes. Studies identifying optimal dosing for proteins and amino acids are not currently available. We discuss the challenges physicians face in administering the optimal amount of protein and amino acids. We present protein-related nutrition concepts, including adaptation to starvation and stress, anabolic resistance, and potential adverse effects of amino acid provision. We describe the methods for assessment of protein status, and outcomes related to protein nutritional support for critically ill patients. The identification of a protein target for individual critically ill patients is crucial for outcomes, particularly for specific subpopulations, such as obese and older patients. Additional research is urgently needed to address these issues.

The effects of critical illness on intestinal glucose sensing, transporters, and absorption

OBJECTIVES

Providing effective enteral nutrition is important during critical illness. In health, glucose is absorbed from the small intestine via sodium-dependent glucose transporter-1 and glucose transporter-2, which may both be regulated by intestinal sweet taste receptors. We evaluated the effect of critical illness on glucose absorption and expression of intestinal sodium-dependent glucose transporter-1, glucose transporter-2, and sweet taste receptors in humans and mice.

DESIGN

Prospective observational study in humans and mice.

SETTING

ICU and university-affiliated research laboratory.

SUBJECTS

Human subjects were 12 critically ill patients and 12 healthy controls. In the laboratory 16-week-old mice were studied.

INTERVENTIONS

Human subjects underwent endoscopy. Glucose (30 g) and 3-O-methylglucose (3 g), used to estimate glucose absorption, were infused intraduodenally over 30 minutes. Duodenal mucosa was biopsied before and after infusion. Mice were randomized to cecal ligation and puncture to model critical illness (n = 16) or sham laparotomy (control) (n = 8). At day 5, mice received glucose (100 mg) and 3-O-methylglucose (10 mg) infused intraduodenally prior to mucosal tissue collection.

MEASUREMENTS AND MAIN RESULTS

Quantitative polymerase chain reaction was performed to measure absolute (human) and relative levels of sodium-dependent glucose transporter-1, glucose transporter-2, and taste receptor type 1 member 2 (T1R2) transcripts. Blood samples were assayed for 3-O-methylglucose to estimate glucose absorption. Glucose absorption was three-fold lower in critically ill humans than in controls (p = 0.002) and reduced by a similar proportion in cecal ligation and puncture mice (p = 0.004). In critically ill patients, duodenal levels of sodium-dependent glucose transporter-1, glucose transporter-2, and T1R2 transcript were reduced 49% (p < 0.001), 50% (p = 0.009), and 85% (p = 0.007), whereas in the jejunum of cecal ligation and puncture mice sodium-dependent glucose transporter-1, glucose transporter-2, and T1R2 transcripts were reduced by 55% (p < 0.001), 50% (p = 0.002), and 69% (p = 0.004).

CONCLUSIONS

Critical illness is characterized by markedly diminished glucose absorption, associated with reduced intestinal expression of glucose transporters (sodium-dependent glucose transporter-1 and glucose transporter-2) and sweet taste receptor transcripts. These changes are paralleled in cecal ligation and puncture mice.

Bomb calorimetry, the gold standard for assessment of intestinal absorption capacity: normative values in healthy ambulant adults

BACKGROUND

Intestinal absorption capacity is considered to be the best method for assessing overall digestive intestinal function. Earlier reference values for intestinal function in healthy Dutch adults were based on a study that was conducted in an inpatient metabolic unit setting in a relatively small series. The present study aimed to readdress and describe the intestinal absorption capacity of healthy adults, who were consuming their usual (Western European) food and beverage diet, in a standard ambulatory setting.

METHODS

Twenty-three healthy subjects (aged 22-60 years) were included in the analyses. Nutritional intake (energy and macronutrients) was determined with a 4-day nutritional diary. Subsequently, mean faecal losses of energy (by bomb calorimetry), fat, protein and carbohydrate were determined following a 3-day faecal collection. Finally, intestinal absorption capacity was calculated from the differences between intake and losses.

RESULTS

Mean (SD) daily faeces production was 141 (49) g (29% dry weight), containing 891 (276) kJ [10.7 (1.3) kJ g(-1) wet faeces; 22.6 (2.5) kJ g(-1) dry faeces], 5.2 (2.2) g fat, 10.0 (3.8) g protein and 29.7 (11.7) g carbohydrates. Mean (SD) intestinal absorption capacity of healthy subjects was 89.4% (3.8%) for energy, 92.5% (3.7%) for fat, 86.9% (6.4%) for protein and 87.3% (6.6%) for carbohydrates.

CONCLUSIONS

The present study provides normative values for both stool nutrient composition and intestinal energy and macronutrient absorption in healthy adults on a regular Dutch diet in an ambulatory setting. Intestinal energy absorption was found to be approximately 90%.

Gastrointestinal dysmotility: evidence and clinical management

PURPOSE OF REVIEW

Gastrointestinal dysmotility and dysfunction underlie our difficulties in providing adequate nutrition by the enteral route to our critically ill patients.

RECENT FINDINGS

Recent studies have quantified gastric emptying and nutrient absorption. Slow gastric emptying is common and probably mediated by cholecystokinin and reduced active ghrelin concentrations. The cause of impaired nutrient absorption is not yet fully understood but may be related to small intestinal blood flow and/or mucosal factors. The absorption of the different macronutrients may be affected in different ways both by critical illness and by therapies. A better understanding of this may optimize the design of nutrient formulations in the future. New treatment modalities for gastrointestinal dysfunction are being investigated and include small intestinal feeding, nonpharmacological options such as acupuncture, and drugs including novel motilin receptor agonists, and opioid antagonists.

SUMMARY

We are gradually developing a better understanding of how the gut works during critical illness, which has implications for optimizing the delivery of nutrition and thereby improving nutritional and clinical outcomes.

Reconciling divergent results of the latest parenteral nutrition studies in the ICU

PURPOSE OF REVIEW

Recent studies on the optimal modalities to feed patients during the ICU stay show divergent results. The level and the timing of energy provision is a critical issue, associated with the clinical outcome. These results questioned the clinical relevance of the recent guidelines issued by American, Canadian and European academic societies.

RECENT FINDINGS

Four recent prospective randomized studies enrolled critically ill patients who received various nutritional regimens and tested the effect of nutritional support on outcome. The Tight Calorie balance Control Study (TICACOS) targeted on calorie administration according to measured energy expenditure and found increased ICU morbidity but improved hospital mortality. The large EpaNIC study compared 'early' with 'late' (parenteral nutrition) nutrition, mostly in patients after cardiac surgery, and found an increased morbidity associated with early parenteral nutrition. The supplemental parenteral nutrition (SPN) study randomized the patients after 3 days and targeted the calories administered by parenteral nutrition as a complement to unsuccessful enteral nutrition using indirect calorimetry. The SPN resulted in less nosocomial infections and shorter duration of mechanical ventilation. Finally, a recent Australian study enrolled patients unable to be early fed enterally to receive, or not, parenteral nutrition targeted at 1500 kcal. No complications were noted in the parenteral nutrition group. Lessons from all these studies are summarized and should help in designing better studies and guidelines.

SUMMARY

The critical analysis of recent prospective studies comparing various levels of calorie administration, enteral versus parenteral nutrition and enteral versus SPN confirms the recommendations to avoid underfeeding and overfeeding. Parenteral nutrition, required if enteral feeding is failing, and if adjusted up to a measured optimal level, may improve outcome. More studies on the optimal level of energy and protein administration to optimize the clinical outcome are required to fine tune current guidelines.

Enteral nutrition: better navigation, yet unknown destination?

The nutrition dose truly absorbed by a patient is crucial information in the management or the investigation of nutrition during critical illness. In the present issue of Critical Care, assessment of nutritional losses in stools was studied. These losses together with enteral nutrition lost in gastric fluids and enteral nutrition prescribed but never infused make up the difference between the dose supposedly given to a patient and the amount effectively taken up. Additionally, the optimal dosing and timing of nutrition during critical illness are still debated. When enteral nutrition is insufficient, the options are limited.