High protein intake without concerns?

Musculoskeletal crosstalk in chronic obstructive pulmonary disease and comorbidities: Emerging roles and therapeutic potentials

Chronic Obstructive Pulmonary Disease (COPD) is a multifaceted respiratory disorder characterized by progressive airflow limitation and systemic implications. It has become increasingly apparent that COPD exerts its influence far beyond the respiratory system, extending its impact to various organ systems. Among these, the musculoskeletal system emerges as a central player in both the pathogenesis and management of COPD and its associated comorbidities. Muscle dysfunction and osteoporosis are prevalent musculoskeletal disorders in COPD patients, leading to a substantial decline in exercise capacity and overall health. These manifestations are influenced by systemic inflammation, oxidative stress, and hormonal imbalances, all hallmarks of COPD. Recent research has uncovered an intricate interplay between COPD and musculoskeletal comorbidities, suggesting that muscle and bone tissues may cross-communicate through the release of signalling molecules, known as "myokines" and "osteokines". We explored this dynamic relationship, with a particular focus on the role of the immune system in mediating the cross-communication between muscle and bone in COPD. Moreover, we delved into existing and emerging therapeutic strategies for managing musculoskeletal disorders in COPD. It underscores the development of personalized treatment approaches that target both the respiratory and musculoskeletal aspects of COPD, offering the promise of improved well-being and quality of life for individuals grappling with this complex condition. This comprehensive review underscores the significance of recognizing the profound impact of COPD on the musculoskeletal system and its comorbidities. By unravelling the intricate connections between these systems and exploring innovative treatment avenues, we can aspire to enhance the overall care and outcomes for COPD patients, ultimately offering hope for improved health and well-being.

Factors Associated with Interruptions of Enteral Nutrition and the Impact on Macro- and Micronutrient Deficits in ICU Patients

BACKGROUND AND AIM

Feeding interruptions in critical care patients are often unjustified. We aimed to determine the causes, duration, and frequency of enteral nutrition interruptions (ENIs) and to assess macronutrients and antioxidant deficits according to European Society of Parenteral Enteral Nutrition (ESPEN) guidelines.

METHODS

We prospectively enrolled Intensive Care Unit (ICU) patients admitted for more than 48 h with an inability to orally eat from April to December 2019. The type of enteral nutrition, the number of calories administered, the time of feeding initiation, the reasons for delaying feeding, and the causes for ENI were recorded.

RESULTS

81 patients were enrolled, with a median duration of ENIs of 5.2 (3.4-7.4) hours/day. Gastric residual volume (GRV) monitoring-a highly controversial practice-was the most common cause of ENI (median duration 3 (2.3-3) hours/day). The mean energy intake was 1037 ± 281 kcal/day, while 60.5% of patients covered less than 65% of the total energy needs (1751 ± 295 kcal/day, according to mean Body Mass Index (BMI)). The median daily protein intake did not exceed 0.43 ± 0.3 gr/kg/day of the actual body weight (BW), whereas ESPEN recommends 1.3 gr/kg/day for adjusted BW (p < 0.001). The average administration of micronutrients and antioxidants (arginine, selenium, zinc, vitamins) was significantly less than the dietary reference intake (p < 0.01).

CONCLUSION

ENIs lead to substantial caloric, protein, and antioxidant deficits.

Protein absorption and kinetics in critical illness

PURPOSE OF REVIEW

Timing, dose, and route of protein feeding in critically ill patients treated in an ICU is controversial. This is because of conflicting outcomes observed in randomized controlled trials (RCTs). This inconsistency between RCTs may occur as the physiology of protein metabolism and protein handling in the critically ill is substantially different from the healthy with limited mechanistic data to inform design of RCTs. This review will outline the current knowledge and gaps in the understanding of protein absorption and kinetics during critical illness.

RECENT FINDINGS

Critically ill patients, both children and adults, lose muscle protein because of substantial increases in protein degradation with initially normal, and over time increasing, protein synthesis rates. Critically ill patients appear to retain the capacity to absorb dietary protein and to use it for building body protein; however, the extent and possible benefit of this needs to be elucidated. More sophisticated methods to study protein absorption and digestion have recently been described but these have yet to be used in the critically ill.

SUMMARY

Adequate understanding of protein absorption and kinetics during critical illness will help the design of better interventional studies in the future. Because of the complexity of measuring protein absorption and kinetics in the critically ill, very few investigations are executed. Recent data using isotope-labelled amino acids suggests that critically ill patients are able to absorb enteral protein and to synthesize new body protein. However, the magnitude of absorption and anabolism that occurs, and possible benefits for the patients need to be elucidated.

Full Versus Trophic Feeds in Critically Ill Adults with High and Low Nutritional Risk Scores: A Randomized Controlled Trial

Although energy intake might be associated with clinical outcomes in critically ill patients, it remains unclear whether full or trophic feeding is suitable for critically ill patients with high or low nutrition risk. We conducted a prospective study to determine which feeding energy intakes were associated with clinical outcomes in critically ill patients with high or low nutrition risk. This was an investigator-initiated, single center, single blind, randomized controlled trial. Critically ill patients were allocated to either high or low nutrition risk based on their Nutrition Risk in the Critically Ill score, and then randomized to receive either the full or the trophic feeding. The feeding procedure was administered for six days. No significant differences were observed in hospital, 14-day and 28-day mortalities, the length of ventilator dependency, or ICU and hospital stay among the four groups. There were no associations between energy and protein intakes and hospital, 14-day and 28-day mortalities in any of the four groups. However, protein intake was positively associated with the length of hospital stay and ventilator dependency in patients with low nutrition risk receiving trophic feeding. Full or trophic feeding in critically ill patients showed no associations with clinical outcomes, regardless of nutrition risk.

Optimizing Nitrogen Balance Is Associated with Better Outcomes in Neurocritically Ill Patients

Marked protein catabolism is common in critically ill patients. We hypothesized that optimal protein supplementation using nitrogen balance might be associated with better outcomes in the neurointensive care unit (NICU) patients. A total of 175 patients admitted to the NICU between July 2017 and December 2018 were included. Nitrogen balance was measured after NICU admission and measurements were repeated in 77 patients. The outcomes were compared according to initial nitrogen balance results and improvement of nitrogen balance on follow-up measurements. A total of 140 (80.0%) patients had a negative nitrogen balance on initial assessments. The negative balance group had more events of in-hospital mortality and poor functional outcome at three months. In follow-up measurement patients, 39 (50.6%) showed an improvement in nitrogen balance. The improvement group had fewer events of in-hospital mortality (p = 0.047) and poor functional outcomes (p = 0.046). Moreover, improvement of nitrogen balance was associated with a lower risk of poor functional outcomes (Odds ratio, 0.247; 95% confidence interval, 0.066–0.925, p = 0.038). This study demonstrated that a significant proportion of patients in the NICU were under protein hypercatabolism. Moreover, an improvement in protein balance was related to improved outcomes in neurocritically ill patients. Further studies are needed to confirm the relationship between protein balance and outcomes.

Uptake of dietary amino acids into arterial blood during continuous enteral feeding in critically ill patients and healthy subjects

BACKGROUND

Amino acid availability is a regulatory factor of protein anabolism and is partly dependent on enteral amino acid uptake. During continuous enteral feeding, enteral amino acid uptake may vary considerably, but this has not been documented systematically.

METHODS

In this pragmatic study, we investigated patients in the intensive care unit (n = 10) and healthy adults (n = 10). The time course of essential amino acid concentrations in arterial plasma and the uptake of dietary phenylalanine were recorded during 12 hours of continuous enteral feeding, using a ¹³C-labeled phenylalanine tracer.

RESULTS

Plasma essential amino acid concentrations and ¹³C-phenylalanine enrichment reached a tentative steady state after no more than 4.5 h from start of tracer infusion. There was a large intra- and inter-individual variability in both cohorts. No periodicity could be detected in the temporal variation.

CONCLUSION

During continuous enteral feeding, uptake of amino acids shows large intra- and inter-individual variation. A tentative steady state of ¹³C-phenylalanine uptake is eventually reached.

TRIAL REGISTRATION

Registered at Australian New Zealand Clinical Trials Registry, trial ID ACTRN12616000593437.

Protein Requirements in Critical Illness: Do We Really Know Why to Give So Much?

The protein and energy requirements of critically ill patients treated in intensive care units (ICUs) have been actively discussed recently. Currently published clinical recommendations and reviews suggest significant increases of protein provision to 2-2.5 g/kg/d in some populations of ICU patients. However, a detailed analysis of the main sources of these recommendations reveals a number of serious contradictions, as well as an absence of obvious evidence supporting the allotment of high doses of protein. We went through these recommendations and reviewed cited articles and other studies, and we have separated our arguments against excessive protein provision into sections.

The Effect of IV Amino Acid Supplementation on Mortality in ICU Patients May Be Dependent on Kidney Function: Post Hoc Subgroup Analyses of a Multicenter Randomized Trial

OBJECTIVES

We investigated whether preexisting kidney function determines if ICU patients may benefit from increased (2.0 g/kg/d) protein intake.

DESIGN

Post hoc, hypothesis-generating, subgroup analysis of a multicenter, phase 2, randomized clinical trial. All analyses were conducted by intention to treat and maintained group allocation. Ninety-day mortality was the primary outcome.

SETTING

ICUs of 16 hospitals throughout Australia and New Zealand.

PATIENTS

Adult critically ill patients expected to remain in the study ICU for longer than 2 days.

INTERVENTIONS

Random allocation to receive a daily supplement of up to 100 g of IV amino acids to achieve a total protein intake of 2.0 g/kg/d or standard nutrition care.

MEASUREMENTS AND MAIN RESULTS

A total of 474 patients were randomized: 235 to standard care and 239 to IV amino acid supplementation. There was a statistically significant interaction between baseline kidney function and supplementation with study amino acids (p value for interaction = 0.026). Within the subgroup of patients with normal kidney function at randomization, patients who were allocated to receive the study amino acid supplement were less likely to die before study day 90 (covariate-adjusted risk difference, -7.9%; 95% CI, -15.1 to -0.7; p = 0.034). Furthermore, amino acid supplementation significantly increased estimated glomerular filtration rate in these patients (repeated-measures treatment × time interaction p = 0.009). Within the subgroup of patients with baseline kidney dysfunction and/or risk of progression of acute kidney injury, a significant effect of the study intervention on mortality was not found (covariate-adjusted risk difference, -0.6%; 95% CI, -16.2 to 15.2; p = 0.95).

CONCLUSIONS

In this post hoc, hypothesis-generating, subgroup analysis, we observed reduced mortality and improved estimated glomerular filtration rate in ICU patients with normal kidney function who were randomly allocated to receive increased protein intake (up to 2.0 g/kg/d). We strongly recommend confirmation of these results in trials with low risk of bias before this treatment is recommended for routine care.

Safety and efficacy of volume-based feeding in critically ill, mechanically ventilated adults using the 'Protein & Energy Requirements Fed for Every Critically ill patient every Time' (PERFECT) protocol: a before-and-after study

BACKGROUND

Underfeeding in critical illness is common and associated with poor outcomes. According to large prospective hospital studies, volume-based feeding (VBF) safely and effectively improves energy and protein delivery to critically ill patients compared to traditional rate-based feeding (RBF) and might improve patient outcomes. A before-and-after study was designed to evaluate the safety, efficacy and clinical outcomes associated with VBF compared to RBF in a single intensive care unit (ICU).

METHODS

The sample included consecutively admitted critically ill adults, mechanically ventilated for at least 72 h and fed enterally for a minimum of 48 h. The first cohort (n = 46) was fed using RBF, the second (n = 46) using VBF, and observed for 7 days, or until extubation or death. Statistical comparison of percentage feed volume, energy and protein delivered, plus indices of feed intolerance, were the primary outcomes of interest. Secondary observations included ventilation period, mortality, and length of ICU stay (LOICUS).

RESULTS

Groups were comparable in baseline clinical and demographic characteristics and nutrition practices. Volume delivered to the VBF group increased significantly by 11.2% (p ≤ 0.001), energy by 13.4% (p ≤ 0.001) and protein by 8.4% (p = 0.02), compared to the RBF group. In the VBF group, patients meeting > 90% of energy requirements increased significantly from 47.8 to 84.8% (p ≤ 0.001); those meeting > 90% of protein requirements changed from 56.5 to 73.9% (p = 0.134). VBF did not increase symptoms of feed intolerance. Adjusted binomial logistic regression found each additional 1% of prescribed feed delivered decreased the odds of vomiting by 0.942 (5.8%), 95% CI [0.900-0.985], p = 0.010. No differences in mortality or LOICUS were identified. Kaplan-Meier found a significantly increased extubation rate in patients receiving > 90% of protein requirements compared to those meeting < 80%, (p = 0.006). Adjusted Cox regression found the daily probability of being extubated tripled in patients receiving > 90% of their protein needs compared to the group receiving < 80%, hazard ratio 3.473, p = 0.021, 95% CI [1.205-10.014].

CONCLUSION

VBF safely and effectively increased the delivery of energy and protein to critically ill patients. Increased protein delivery may improve extubation rate which has positive patient-centred and financial implications, warranting larger confirmatory trials. This investigation adds weight to the ICU literature supporting VBF, and the growing evidence which advocates for enhanced protein delivery to improve patient outcomes.

Early Administration of Protein in Critically Ill Patients: A Retrospective Cohort Study

It is currently uncertain whether early administration of protein improves patient outcomes. We examined mortality rates of critically ill patients receiving early compared to late protein administration. This was a retrospective cohort study of mixed ICU patients receiving enteral or parenteral nutritional support. Patients receiving >0.7 g/kg/d protein within the first 3 days were considered the early protein group and those receiving less were considered the late protein group. The latter were subdivided into late-low group (LL) who received a low protein intake (<0.7 g/kg/d) throughout their stay and the late-high group (LH) who received higher doses (>0.7 g/kg/d) of protein following their first 3 days of admission. The outcome measure was all-cause mortality 60 days after admission. Of the 2253 patients included in the study, 371 (36%) in the early group, and 517 (43%) in the late-high group had died (p < 0.001 for difference). In multivariable Cox regression analysis, while controlling for confounders, early protein administration was associated with increased survival (HR 0.83, 95% CI 0.71⁻0.97, p = 0.017). Administration of protein early in the course of critical illness appears to be associated with improved survival in a mixed ICU population, even after adjusting for confounding variables.

Acute Inflammation and Metabolism

Inflammation is an adaptive process to the noxious stimuli that the human body is constantly exposed to. From the local inflammatory response to a full-blown systemic inflammation, a wide complex sequence of events occurs. Persistent immunosuppression and catabolism may ensue, until multiple organ failure finally sets in. And since clinically useful and specific biomarkers are lacking, diagnosis may come late. A thorough understanding of these events (how they begin, how they evolve, and how to modulate them) is imperative, but as yet poorly studied. This review aims to consolidate current knowledge of these events so that the management of these patients is not only evidence-based, but also built on an understanding of the inner workings of the human body in health and in disease.

High protein intake during the early phase of critical illness: yes or no?

The rationale for the provision of nitrogen from proteins given via the enteral route or from intravenous amino acids is to boost the synthesis of muscle proteins, and thereby to limit the severity of intensive care unit-acquired weakness by the prevention of muscle loss. However, the optimal timing for supplemental nitrogen provision is a matter of debate and controversy. Indeed, consistent data from retrospective studies support an association between high early protein intakes and better outcomes, while recent post-hoc findings from prospective studies raise safety concerns. This pro–con paper details the arguments of both sides and highlights the need for large-scale prospective studies assessing the safety and efficacy of different levels of protein intake in combination with physical activity and summarizes the currently recruiting clinical trials.

Very high intact-protein formula successfully provides protein intake according to nutritional recommendations in overweight critically ill patients: a double-blind randomized trial

BACKGROUND

Optimal energy and protein provision through enteral nutrition is essential for critically ill patients. However, in clinical practice, the intake achieved is often far below the recommended targets. Because no polymeric formula with sufficient protein content is available, adequate protein intake can be achieved only by supplemental amino acids or semi-elemental formula administration. In the present study, we investigated whether protein intake can be increased with a new, very high intact-protein formula (VHPF) for enteral feeding.

METHODS

In this randomized, controlled, double-blind, multicenter trial, 44 overweight (body mass index ≥ 25 kg/m2) intensive care unit patients received either a VHPF (8 g/100 kcal) or a commercially available standard high protein formula (SHPF) (5 g/100 kcal). Protein and energy intake, gastrointestinal tolerance (gastric residual volume, vomiting, diarrhea, and constipation), adverse events, and serious adverse events were recorded. Total serum amino acid levels were measured at baseline and day 5.

RESULTS

The primary outcome, protein intake at day 5, was 1.49 g/kg body weight (95% CI 1.21-1.78) and 0.76 g/kg body weight (95% CI 0.49-1.03, P < 0.001) for VHPF and SHPF, respectively. Daily protein intake was statistically significantly higher in the VHPF group compared with the SHPF group from day 2 to day 10. Protein intake in the VHPF group as a percentage of target (1.5 g/kg ideal body weight) was 74.7% (IQR 53.2-87.6%) and 111.6% (IQR 51.7-130.7%) during days 1-3 and days 4-10, respectively. Serum amino acid concentrations were higher at day 5 in the VHPF group than in the SHPF group (P = 0.031). No differences were found in energy intake, measures of gastrointestinal tolerance, and safety.

CONCLUSIONS

Enteral feeding with VHPF (8 g/100 kcal) resulted in higher protein intake and plasma amino acid concentrations than an isocaloric SHPF (5 g/100 kcal), without an increase in energy intake. This VHPF facilitates feeding according to nutritional guidelines and is suitable as a first-line nutritional treatment for critically ill overweight patients.

TRIAL REGISTRATION

Netherlands Trial Register, NTR5643 . Registered on 2 February 2016.

A supplemental intravenous amino acid infusion sustains a positive protein balance for 24 hours in critically ill patients

BACKGROUND

Providing supplemental amino acids to ICU patients during a 3-h period results in improved whole-body net protein balance, without an increase in amino acid oxidation. The primary objective was to investigate if a 24-h intravenous amino acid infusion in critically ill patients has a sustained effect on whole-body protein balance as was seen after 3 h. Secondary objectives were monitoring of amino acid oxidation rate, urea and free amino acid plasma concentrations.

METHODS

An infusion of [1-¹³C]-phenylalanine was added to ongoing enteral nutrition to quantify the enteral uptake of amino acids. Primed intravenous infusions of [ring-²H₅]-phenylalanine and [3,3-²H₂]-tyrosine were used to assess whole-body protein synthesis and breakdown, to calculate net protein balance and to assess amino acid oxidation at baseline and at 3 and 24 hours. An intravenous amino acid infusion was added to nutrition at a rate of 1 g/kg/day and continued for 24 h.

RESULTS

Eight patients were studied. The amino acid infusion resulted in improved net protein balance over time, from -1.6 ± 7.9 μmol phe/kg/h at 0 h to 6.0 ± 8.8 at 3 h and 7.5 ± 5.1 at 24 h (p = 0.0016). The sum of free amino acids in plasma increased from 3.1 ± 0.6 mmol/L at 0 h to 3.2 ± 0.3 at 3 h and 3.6 ± 0.5 at 24 h (p = 0.038). Amino acid oxidation and plasma urea were not altered significantly.

CONCLUSION

We demonstrated that the improvement in whole-body net protein balance from a supplemental intravenous amino acid infusion seen after 3 h was sustained after 24 h in critically ill patients.

TRIAL REGISTRATION

This trial was prospectively registered at Australian New Zealand Clinical Trials Registry. ACTRN, 12615001314516 . Registered on 1 December 2015.