A randomized-controlled trial of arginine infusion in severe sepsis on microcirculation and metabolism

Early intravenous branched-chain amino acid-enriched nutrition supplementation in older patients undergoing gastric surgery: a randomized clinical trial

BACKGROUND

The initiation time and formula for supplemental parenteral nutrition after surgery require optimization, especially in older patients undergoing major gastrointestinal surgery. This study aimed to assess the effect of early supplementation with a branched-chain amino acid (BCAA)-enriched formula (BAF) on short-term postoperative outcomes in older patients undergoing gastric surgery.

METHODS

This single-center, prospective, double-blinded, randomized clinical trial was conducted from March 10, 2020, to September 15, 2022. Patients aged 65-80 years with gastric cancer scheduled for curative resection were assessed for eligibility and randomly allocated to a high-proportion BCAA (HBCAA) (early supplementation with the BAF) or control (routine nutrition) group. The primary outcome was the standardized length of hospital stay (LOS).

RESULTS

A total of 150 patients were randomized. Thirteen patients were excluded due to the resection of other organs, presence of metastasis, or withdrawal of consent. Finally, we included 70 and 67 patients in the HBCAA and control groups, respectively (mean age: 70.5 ± 4.2 years; 96 men [70.1%]). The standardized LOS was significantly shorter in the treatment group than in the control group (median [interquartile range]: 8.0 [7.8, 8.0] vs. 8.5 [8.0, 9.0] days; mean difference, 0.38; 95% confidence interval [CI], 0.02-0.74 days; P < .001). Patients in the HBCAA group showed better gastrointestinal function with faster defecation (4.0 [3.6, 5.0] vs. 5.0 [4.0, 5.5] days; mean difference, 0.6 days; 95% CI, 0.26-0.94 days; P < .001) and semi-liquid diet initiation (8.0 [7.5, 8.0] vs. 8.0 [8.0, 8.8] days; mean difference, 0.36 days; 95% CI, 0.03-0.7 days; P < .001) and had lesser weight loss at postoperative day 5 than those in the control group did (3.5 [2.7, 6.5] vs. 4.9 [3.3, 7.6]%; mean difference, 1.23%; 95% CI, 0.27-2.19%; P = .011).

CONCLUSIONS

In this randomized clinical trial, compared with routine nutrition, early supplementation with a BAF was associated with a shorter standardized LOS in older patients undergoing gastric surgery, suggesting that it may be a favorable strategy for patients with a poor tolerance to external nutrition who are undergoing major surgery.

TRIAL REGISTRATION

ClinicalTrials.gov; Identifier: ChiCTR2000029635.

Exploring the circulating metabolome of sepsis: metabolomic and lipidomic profiles sampled in the ambulance

BACKGROUND

Sepsis is defined as a dysfunctional host response to infection. The diverse clinical presentations of sepsis pose diagnostic challenges and there is a demand for enhanced diagnostic markers for sepsis as well as an understanding of the underlying pathological mechanisms involved in sepsis. From this perspective, metabolomics has emerged as a potentially valuable tool for aiding in the early identification of sepsis that could highlight key metabolic pathways and underlying pathological mechanisms.

OBJECTIVE

The aim of this investigation is to explore the early metabolomic and lipidomic profiles in a prospective cohort where plasma samples (n = 138) were obtained during ambulance transport among patients with infection according to clinical judgement who subsequently developed sepsis, patients who developed non-septic infection, and symptomatic controls without an infection.

METHODS

Multiplatform metabolomics and lipidomics were performed using UHPLC-MS/MS and UHPLC-QTOFMS. Uni- and multivariable analysis were used to identify metabolite profiles in sepsis vs symptomatic control and sepsis vs non-septic infection.

RESULTS

Univariable analysis disclosed that out of the 457 annotated metabolites measured across three different platforms, 23 polar, 27 semipolar metabolites and 133 molecular lipids exhibited significant differences between patients who developed sepsis and symptomatic controls following correction for multiple testing. Furthermore, 84 metabolites remained significantly different between sepsis and symptomatic controls following adjustment for age, sex, and Charlson comorbidity score. Notably, no significant differences were identified in metabolites levels when comparing patients with sepsis and non-septic infection in univariable and multivariable analyses.

CONCLUSION

Overall, we found that the metabolome, including the lipidome, was decreased in patients experiencing infection and sepsis, with no significant differences between the two conditions. This finding indicates that the observed metabolic profiles are shared between both infection and sepsis, rather than being exclusive to sepsis alone.

Nutritional and metabolic modulation of inflammation in critically ill patients: a narrative review of rationale, evidence and grey areas

BACKGROUND

Inflammation is the hallmark of critical illness and triggers the neuro-endocrine stress response and an oxidative stress. Acute inflammation is initially essential for patient's survival. However, ongoing or exaggerated inflammation, due to persistent organ dysfunction, immune dysfunction or poor inflammation resolution, is associated to subsequent hypermetabolism and hypercatabolism that severely impact short and long-term functional status, autonomy, as well as health-related costs. Modulation of inflammation is thus tempting, with the goal to improve the short- and long-term outcomes of critically ill patients.

FINDINGS

Inflammation can be modulated by nutritional strategies (including the timing of enteral nutrition initiation, the provision of some specific macronutrients or micronutrients, the use of probiotics) and metabolic treatments. The most interesting strategies seem to be n-3 polyunsaturated fatty acids, vitamin D, antioxidant micronutrients and propranolol, given their safety, their accessibility for clinical use, and their benefits in clinical studies in the specific context of critical care. However, the optimal doses, timing and route of administration are still unknown for most of them. Furthermore, their use in the recovery phase is not well studied and defined.

CONCLUSION

The rationale to use strategies of inflammation modulation is obvious, based on critical illness pathophysiology and based on the increasingly described effects of some nutritional and pharmacological strategies. Regretfully, there isn't always substantial proof from clinical research regarding the positive impacts directly brought about by inflammation modulation. Some arguments come from studies performed in severe burn patients, but such results should be transposed to non-burn patients with caution. Further studies are needed to explore how the modulation of inflammation can improve the long-term outcomes after a critical illness.

A review of perioperative immune-modulating and metabolic-modulating nutrition strategies for bowel resection surgery

Focused perioperative nutrition strategies have proven benefits on the outcomes for patients undergoing major abdominal surgery. In this brief article, we will review these strategies and the evidence to support them with a focus on gastrointestinal anastomotic healing. We will elaborate the risks and benefits of enteral feeds, immune- and metabolic-modulating formulas, prebiotics and probiotics, and prehabilitation in preparation for surgery. Additionally, we will discuss the role of fish oils (eicosapentaenoic acid and docosahexaenoic acid) in the surgical patient and new data on specialized proresolving mediators in inflammation resolution. Finally, this article will consider the harmful impact surgical trauma has on the microbiome and the potential for perioperative dietary modulation to attenuate these negative effects.

Amino acid kinetics in the critically ill

PURPOSE OF REVIEW

Stable isotope methods have been used for many years to assess whole body protein and amino acid kinetics in critically ill patients. In recent years, new isotope approaches and tracer insights have been developed. The tracer pulse approach has some advantages above the established primed-continuous tracer infusion approach because of the high amount of metabolic information obtained, easy applicability, and low tracer costs. Effects of disease severity and sex on amino acid kinetics in ICU patients will also be addressed.

RECENT FINDINGS

Current knowledge was synthesized on specific perturbations in amino acid metabolism in critically ill patients, employing novel methodologies such as the pulse tracer approach and computational modeling. Variations were evaluated in amino acid production and linked to severity of critical illness, as measured by SOFA score, and sex. Production of the branched-chain amino acids (BCAAs), glutamine, tau-methylhistidine and hydroxyproline were elevated in critical illness, likely related to increased transamination of the individual BCAAs or increased breakdown of proteins. Citrulline production was reduced, indicative of impaired gut mucosa function. Sex and disease severity independently influenced amino acid kinetics in ICU patients.

SUMMARY

Novel tracer and computational approaches have been developed to simultaneously measure postabsorptive kinetics of multiple amino acids that can be used in critical illness. The collective findings lay the groundwork for targeted individualized nutritional strategies in ICU settings aimed at enhancing patient outcomes taking into account disease severity and sex.

Microcirculation-guided resuscitation in sepsis: the next frontier?

Microcirculatory dysfunction plays a key role in the pathogenesis of tissue dysoxia and organ failure in sepsis. Sublingual videomicroscopy techniques enable the real-time non-invasive assessment of microvascular blood flow. Alterations in sublingual microvascular perfusion were detected during sepsis and are associated with poor outcome. More importantly, sublingual videomicroscopy allowed to explore the effects of commonly applied resuscitative treatments in septic shock, such as fluids, vasopressors and inotropes, and showed that the optimization of macro-hemodynamic parameters may not be accompanied by an improvement in microvascular perfusion. This loss of "hemodynamic coherence," i.e., the concordance between the response of the macrocirculation and the microcirculation, advocates for the integration of microvascular monitoring in the management of septic patients. Nonetheless, important barriers remain for a widespread use of sublingual videomicroscopy in the clinical practice. In this review, we discuss the actual limitations of this technique and future developments that may allow an easier and faster evaluation of the microcirculation at the bedside, and propose a role for sublingual microvascular monitoring in guiding and titrating resuscitative therapies in sepsis.

Nutrition support for critically ill patients

Nutrition support is an important aspect of the management of critically ill patients. This review highlights the emerging evidence on critical care nutrition and focuses on the pathophysiologic interplay between critical illness, the gastrointestinal tract, and nutrition support and the evidence on the best route, dose, and timing of nutrition. Although indirect calorimetry is recommended to measure energy expenditure, predictive equations are commonly used but are limited by their inaccuracy in individual patients. The current evidence supports early enteral nutrition (EN) in most patients, with a gradual increase in the daily dose over the first week. Delayed EN is warranted in patients with severe shock. According to recent trials, parenteral nutrition seems to be as effective as EN and may be started if adequate EN is not achieved by the first week of critical illness. A high protein dose has been recommended, but the best timing is unclear. Immuno-nutrition should not be routinely provided to critically ill patients. Patients receiving artificial nutrition should be monitored for metabolic derangements. Additional adequately powered studies are still needed to resolve many unanswered questions.

NO, way to go: critical amino acids to replenish nitric oxide production in treating mucositis

PURPOSE OF REVIEW

There is still an unmet need for preventive and treatment strategies for chemotherapy-induced and radiotherapy-induced mucositis and its associated systemic inflammatory response (SIR) in cancer patients. Because of citrulline depletion due to cytotoxic therapy, nitric oxide (NO) production can be reduced, limiting its effect in many physiological processes. Restoring NO production could relieve mucositis severity by supporting host damage control mechanisms. Amino acids glutamine, arginine and citrulline are involved in NO production. This review including recent literature of preclinical and clinical studies will discuss the potential benefits of glutamine, arginine and citrulline on mucositis development with focus on NO production.

RECENT FINDINGS

Mucositis severity is more defined by host response to DNA damage than by DMA damage itself. Citrulline depletion because of afunctional enterocytes could be responsible for NO depletion during cytotoxic therapy. Restoring NO production during cytotoxic therapy could have a beneficial effect on mucositis development. Citrulline seems a more promising NO donor than glutamine or arginine during cytotoxic therapy, although clinical studies in mucositis patients are currently lacking.

SUMMARY

Glutamine, arginine and citrulline show in-vitro beneficial effects on inflammatory processes involved in mucositis. Translation to the clinic is difficult as demonstrated with use of glutamine and arginine. Citrulline, being the most potent NO donor with excellent oral bio-availability, is very promising as treatment choice for mucositis and its use deserves to be investigated in clinical trials with mucositis patients.

Development and validation of a novel sepsis biomarker based on amino acid profiling

BACKGROUND & AIMS

Sepsis is a potentially fatal condition influenced by pathogens and host factors. Current sepsis biomarkers such as white blood cell count and C-reactive protein and procalcitonin levels show unsatisfactory performance in terms of diagnostic sensitivity and specificity in clinical practice. Thus, we developed and validated a new sepsis biomarker based on amino acid profiling.

METHODS

We used two independent groups. The training and validation groups included 161 and 22 healthy controls, 123 and 50 patients with systemic inflammatory response syndrome, and 115 and 45 patients with sepsis, respectively. Using mass spectrometry, we measured and analyzed serum amino acid levels to select candidate amino acids that could differentiate sepsis from other conditions. Then, several possible multivariate indexes were developed by generating formulae with different combinations of candidate amino acids. The formula showing the best performance was selected and validated further.

RESULTS

Kynurenine, tryptophan, phenylalanine, arginine, aspartic acid, glutamic acid, and glutamine were selected as candidate amino acids. Ten possible formulae were generated, and the formula with the highest diagnostic performance, which included kynurenine, tryptophan, phenylalanine, and arginine, was selected. In the validation group, the area under the receiving operating characteristic curve of the selected multivariate index (0.931) was similar to that of procalcitonin (0.945). Moreover, the generated multivariate index showed potential as a prognostic marker.

CONCLUSIONS

Serum amino acid composition in patients with sepsis differs significantly from that in healthy individuals and patients with inflammation only. The newly developed multivariate index is expected to be implementable as a sepsis biomarker in clinical practice in the near future.

Metabolism of Proteins and Amino Acids in Critical Illness: From Physiological Alterations to Relevant Clinical Practice

The clinical impact of nutrition therapy in critically ill patients has been known for years, and relevant guidelines regarding nutrition therapy have emphasized the importance of proteins. During critical illness, such as sepsis or the state following major surgery, major trauma, or major burn injury, patients suffer from a high degree of stress/inflammation, and during this time, metabolism deviates from homeostasis. The increased degradation of endogenous proteins in response to stress hormones is among the most important events in the acute phase of critical illness. Currently published evidence suggests that adequate protein supplementation might improve the clinical outcomes of critically ill patients. The role of sufficient protein supplementation may even surpass that of caloric supplementation. In this review, we focus on relevant physiological alterations in critical illness, the effects of critical illness on protein metabolism, nutrition therapy in clinical practice, and the function of specific amino acids.

Cardiovascular Responses During Sepsis

Sepsis is the life-threatening organ dysfunction arising from a dysregulated host response to infection. Although the specific mechanisms leading to organ dysfunction are still debated, impaired tissue oxygenation appears to play a major role, and concomitant hemodynamic alterations are invariably present. The hemodynamic phenotype of affected individuals is highly variable for reasons that have been partially elucidated. Indeed, each patient's circulatory condition is shaped by the complex interplay between the medical history, the volemic status, the interval from disease onset, the pathogen, the site of infection, and the attempted resuscitation. Moreover, the same hemodynamic pattern can be generated by different combinations of various pathophysiological processes, so the presence of a given hemodynamic pattern cannot be directly related to a unique cluster of alterations. Research based on endotoxin administration to healthy volunteers and animal models compensate, to an extent, for the scarcity of clinical studies on the evolution of sepsis hemodynamics. Their results, however, cannot be directly extrapolated to the clinical setting, due to fundamental differences between the septic patient, the healthy volunteer, and the experimental model. Numerous microcirculatory derangements might exist in the septic host, even in the presence of a preserved macrocirculation. This dissociation between the macro- and the microcirculation might account for the limited success of therapeutic interventions targeting typical hemodynamic parameters, such as arterial and cardiac filling pressures, and cardiac output. Finally, physiological studies point to an early contribution of cardiac dysfunction to the septic phenotype, however, our defective diagnostic tools preclude its clinical recognition. © 2021 American Physiological Society. Compr Physiol 11:1605-1652, 2021.

Comprehensive metabolic amino acid flux analysis in critically ill patients

Amino acid (AA) metabolism is severely disturbed in critically ill ICU patients. To be able to make a more scientifically based decision on the type of protein or AA nutrition to deliver in ICU patients, comprehensive AA phenotyping with measurements of plasma concentrations and whole body production (WBP) is needed. Therefore, we studied ICU patients and matched control subjects using a novel pulse isotope method to obtain in-depth metabolic analysis. In 51 critically ill ICU patients (SOFA~6.6) and 49 healthy controls, we measured REE and body composition/phase-angle using BIA. In the postabsorptive state, we collected arterial (ized) blood for CRP and AA. Then, we administered an 8 mL solution containing 18 stable AA tracers as a pulse and calculated WBP. Enrichments: LC-MS/MS and statistics: t-test, ANCOVA. Compared to healthy, critically ill ICU patients had lower phase-angle (p < 0.00001), and higher CRP (p < 0.0001). Most AA concentrations were lower in ICU patients (p < 0.0001), except tau-methylhistidine and phenylalanine. WBP of most AA were significantly (p < 0.0001) higher with increases in glutamate (160%), glutamine (46%), and essential AA. Remarkably, net protein breakdown was lower. There were only weak relationships between AA concentrations and WBP. Critically ill ICU patients (SOFA 8-16) had lower values for phase angle (p = 0.0005) and small reductions of most plasma AA concentrations, but higher tau-methylhistidine (p = 0.0223) and hydroxyproline (p = 0.0028). Remarkably, the WBP of glutamate and glutamine were lower (p < 0.05), as was their clearance, but WBP of tau-methylhistidine (p = 0.0215) and hydroxyproline (p = 0.0028) were higher. Our study in critically ill ICU patients shows that comprehensive metabolic phenotyping was able to reveal severe disturbances in specific AA pathways, in a disease severity dependent way. This information may guide improving nutritional compositions to improve the health of the critically ill patient. CLINICAL TRIAL REGISTRY: Data are from the baseline measurements of study NCT02770092 (URL: https://clinicaltrials.gov/ct2/show/NCT02770092) and NCT03628365 (URL: https://clinicaltrials.gov/ct2/show/NCT03628365).

Intravenous Arginine Administration Benefits CD4+ T-Cell Homeostasis and Attenuates Liver Inflammation in Mice with Polymicrobial Sepsis

This study investigated the effects of a single dose of arginine (Arg) administration at the beginning of sepsis on CD4+ T-cell regulation and liver inflammation in C57BL/6J mice. Mice were divided into normal control (NC), sham (SH), sepsis saline (SS), and sepsis Arg (SA) groups. An inducible nitric oxide (NO) synthase (iNOS) inhibitor was administered to additional sepsis groups to evaluate the role of NO during sepsis. Sepsis was induced using cecal ligation and puncture (CLP). The SS and SA groups received saline or Arg (300 mg/kg body weight) via tail vein 1 h after CLP. Mice were euthanized at 12 and 24 h post-CLP. Blood, para-aortic lymph nodes, and liver tissues were collected for further measurement. The findings showed that sepsis resulted in decreases in blood and para-aortic lymph node CD4+ T-cell percentages, whereas percentages of interleukin (IL)-4- and IL-17-expressing CD4+ T cells were upregulated. Compared to the SS group, Arg administration resulted in maintained circulating and para-aortic lymph node CD4+ T cells, an increased Th1/Th2 ratio, and a reduced Th17/Treg ratio post-CLP. In addition, levels of plasma liver injury markers and expression of inflammatory genes in liver decreased. These results suggest that a single dose of Arg administered after CLP increased Arg availability, sustained CD4+ T-cell populations, elicited more-balanced Th1/Th2/Th17/Treg polarization in the circulation and the para-aortic lymph nodes, and attenuated liver inflammation in sepsis. The favorable effects of Arg were abrogated when an iNOS inhibitor was administered, which indicated that NO may be participated in regulating the homeostasis of Th/Treg cells and subsequent liver inflammation during sepsis.