Effect of Combined Protein-Enriched Enteral Nutrition and Early Cycle Ergometry in Mechanically Ventilated Critically Ill Patients—A Pilot Study

Nutrition in the intensive care unit: from the acute phase to beyond

Recent randomized controlled trials (RCTs) have shown no benefit but  dose-dependent harm by early full nutritional support in critically ill patients. Lack of benefit may be explained by anabolic resistance, suppression of cellular repair processes, and aggravation of hyperglycemia and insulin needs. Also early high amino acid doses did not provide benefit, but instead associated with harm in patients with organ dysfunctions. However, most studies focused on nutritional interventions initiated during the first days after intensive care unit admission. Although the intervention window of some RCTs extended into the post-acute phase of critical illness, no large RCTs studied nutritional interventions initiated beyond the first week. Hence, clear evidence-based guidance on when and how to initiate and advance nutrition is lacking. Prolonged underfeeding will come at a price as there is no validated metabolic monitor that indicates readiness for medical nutrition therapy, and an adequate response to nutrition, which likely varies between patients. Also micronutrient status cannot be assessed reliably, as inflammation can cause redistribution, so that plasma micronutrient concentrations are not necessarily reflective of total body stores. Moreover, high doses of individual micronutrients have not proven beneficial. Accordingly, current evidence provides clear guidance on which nutritional strategies to avoid, but the ideal nutritional regimen for individual patients remains unclear. In this narrative review, we summarize the findings of recent studies, discuss possible mechanisms explaining the results, point out pitfalls in interpretation of RCTs and their effect on clinical practice, and formulate suggestions for future research.

Indirect calorimetry directed feeding and cycling in the older ICU population: a pilot randomised controlled trial

BACKGROUND

Older critically ill patients experience rapid muscle loss during stay in an intensive care unit (ICU) due to physiological stress and increased catabolism. This may lead to increased ICU length of stay, delayed weaning from ventilation and persistent functional limitations. We hypothesized that with optimal nutrition and early physical therapy acting in synergism, we can reduce muscle mass loss and improve functional outcomes.

METHODS

This was a prospective, single blinded randomized, controlled single-center pilot study to compare the lean muscle mass (measured at bilateral quadriceps femoris using ultrasound) of older ICU patients at 4 time points over 14 days between the control and intervention groups. The control group received standard weight-based empiric feeding and standard ICU physiotherapy. The intervention group received indirect calorimetry directed feeding adjusted daily and 60 min per day of cycle ergometry. 21 patients were recruited and randomized with 11 patients in the control arm and 10 patients in the intervention arm. Secondary outcome measures included ICU and hospital mortality, length of stay, functional assessments of mobility and assessment of strength.

RESULTS

Median age was 64 in the control group and 66 in the intervention group. Median calories achieved was 24.5 kcal/kg per day in the control group and 23.3 kcal/kg per day in the intervention group. Cycle ergometry was applied to patients in the intervention group for a median of 60 min a day and a patient had a median of 8.5 sessions in 14 days. Muscle mass decreased by a median of 4.7cm2 in the right quadriceps femoris in the control group and 1.8cm2 in the intervention group (p = 0.19), while the left quadriceps femoris decreased by 1.9cm2 in the control group and 0.1cm2 in the intervention group (p = 0.51).

CONCLUSION

In this pilot study, we found a trend towards decrease muscle loss in bilateral quadriceps femoris with our combined interventions. However, it did not reach statistical significance likely due to small number of patients recruited in the study. However, we conclude that the intervention is feasible and potentially beneficial and may warrant a larger scale study to achieve statistical significance.

TRIAL REGISTRATION

This study was registered on Clinicaltrials.gov on 30th May 2018 with identifier NCT03540732.

The effects of higher versus lower protein delivery in critically ill patients: an updated systematic review and meta-analysis of randomized controlled trials with trial sequential analysis

BACKGROUND

A recent large multicentre trial found no difference in clinical outcomes but identified a possibility of increased mortality rates in patients with acute kidney injury (AKI) receiving higher protein. These alarming findings highlighted the urgent need to conduct an updated systematic review and meta-analysis to inform clinical practice.

METHODS

From personal files, citation searching, and three databases searched up to 29-5-2023, we included randomized controlled trials (RCTs) of adult critically ill patients that compared higher vs lower protein delivery with similar energy delivery between groups and reported clinical and/or patient-centred outcomes. We conducted random-effect meta-analyses and subsequently trial sequential analyses (TSA) to control for type-1 and type-2 errors. The main subgroup analysis investigated studies with and without combined early physical rehabilitation intervention. A subgroup analysis of AKI vs no/not known AKI was also conducted.

RESULTS

Twenty-three RCTs (n = 3303) with protein delivery of 1.49 ± 0.48 vs 0.92 ± 0.30 g/kg/d were included. Higher protein delivery was not associated with overall mortality (risk ratio [RR]: 0.99, 95% confidence interval [CI] 0.88-1.11; I2 = 0%; 21 studies; low certainty) and other clinical outcomes. In 2 small studies, higher protein combined with early physical rehabilitation showed a trend towards improved self-reported quality-of-life physical function measurements at day-90 (standardized mean difference 0.40, 95% CI - 0.04 to 0.84; I2 = 30%). In the AKI subgroup, higher protein delivery significantly increased mortality (RR 1.42, 95% CI 1.11-1.82; I2 = 0%; 3 studies; confirmed by TSA with high certainty, and the number needed to harm is 7). Higher protein delivery also significantly increased serum urea (mean difference 2.31 mmol/L, 95% CI 1.64-2.97; I2 = 0%; 7 studies).

CONCLUSION

Higher, compared with lower protein delivery, does not appear to affect clinical outcomes in general critically ill patients but may increase mortality rates in patients with AKI. Further investigation of the combined early physical rehabilitation intervention in non-AKI patients is warranted.

PROSPERO ID

CRD42023441059.

Predictors of acute muscle loss in the intensive care unit: A secondary analysis of an in-bed cycling trial for critically ill patients

PURPOSE

The purpose of this study was to assist clinicians to identify critically ill patients at greatest risk of acute muscle loss and to analyse the associations between protein intake and exercise on acute muscle loss.

MATERIALS AND METHODS

Secondary analysis of a single-centre randomised clinical trial of in-bed cycling using a mixed effects model was undertaken to examine the association between key variables and rectus femoris cross-sectional area (RFCSA). Groups were combined, and key variables for the cohort were modified Nutrition Risk in the Critically Ill (mNUTRIC) scores within the first days following intensive care unit admission, longitudinal RFCSA measurements, percent of daily recommended protein intake, and group allocation (usual care, in-bed cycling). RFCSA ultrasound measurements were taken at baseline and days 3, 7, and 10 to quantify acute muscle loss. All patients received usual care nutritional intake while in the intensive care unit. Patients allocated to the cycling group commenced in-bed cycling once safety criteria were met.

RESULTS

Analysis included all 72 participants, of which 69% were male, with a mean (standard deviation) age of 56 (17) years. Patients received a mean (standard deviation) of 59% (26%) of the minimum protein dose recommended for critically ill patients. Mixed-effects model results indicated that patients with higher mNUTRIC scores experienced greater RFCSA loss (estimate = -0.41; 95% confidence interval [CI] = -0.59 to -0.23). RFCSA did not share a statistically significant association with cycling group allocation (estimate = -0.59, 95% CI = -1.53 to 0.34), the percentage of protein requirements received (estimate = -0.48; 95% CI = -1.16 to 0.19), or a combination of cycling group allocation and higher protein intake (estimate = 0.33, 95% CI = -0.76 to 1.43).

CONCLUSIONS AND RELEVANCE

We found that a higher mNUTRIC score was associated with greater muscle loss, but we did not observe a relationship between combined protein delivery and in-bed cycling and muscle loss. The low protein doses achieved may have impacted the potential for exercise or nutrition strategies to reduce acute muscle loss.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry (ACTRN 12616000948493).

Study protocol for TARGET protein: The effect of augmented administration of enteral protein to critically ill adults on clinical outcomes: A cluster randomised, cross-sectional, double cross-over, clinical trial

Background

It is unknown whether increasing dietary protein to 1.2-2.0 g/kg/day as recommended in international guidelines compared to current practice improves outcomes in intensive care unit (ICU) patients. The TARGET Protein trial will evaluate this.

Objective

To describe the study protocol for the TARGET Protein trial.

Design setting and participants

TARGET Protein is a cluster randomised, cross-sectional, double cross-over, pragmatic clinical trial undertaken in eight ICUs in Australia and New Zealand. Each ICU will be randomised to use one of two trial enteral formulae for three months before crossing over to the other formula, which is then repeated, with enrolment continuing at each ICU for 12 months. All patients aged ≥16 years in their index ICU admission commencing enteral nutrition will be eligible for inclusion. Eligible patients will receive the trial enteral formula to which their ICU is allocated. The two trial enteral formulae are isocaloric with a difference in protein dose: intervention 100g/1000 ml and comparator 63g/1000 ml. Staggered recruitment commenced in May 2022.

Main outcomes measures

The primary outcome is days free of the index hospital and alive at day 90. Secondary outcomes include days free of the index hospital at day 90 in survivors, alive at day 90, duration of invasive ventilation, ICU and hospital length of stay, incidence of tracheostomy insertion, renal replacement therapy, and discharge destination.

Conclusion

TARGET Protein aims to determine whether augmented enteral protein delivery reduces days free of the index hospital and alive at day 90.

Trial registration

Australian New Zealand Clinical Trials Registry (ACTRN12621001484831).

Physical therapy and nutrition therapy: synergistic, antagonistic, or independent interventions?

PURPOSE OF REVIEW

Physical therapy and nutrition therapy have predominantly been studied separately in the critically ill, however in clinical practice are often delivered in combination. It is important to understand how these interventions interact. This review will summarize the current science - where they are potentially synergistic, antagonistic, or independent interventions.

RECENT FINDINGS

Only six studies were identified within the ICU setting that combined physical therapy and nutrition therapy. The majority of these were randomized controlled trials with modest sample sizes. There was an indication of benefit in the preservation of femoral muscle mass and short-term physical quality of life - particularly with high-protein delivery and resistance exercise, in patients who were predominantly mechanically ventilated patients, with an ICU length of stay of approximately 4-7 days (varied across studies). Although these benefits did not extend to other outcomes such as reduced length of ventilation, ICU or hospital admission. No recent trials were identified that combined physical therapy and nutrition therapy in post-ICU settings and is an area that warrants investigation.

SUMMARY

The combination of physical therapy and nutrition therapy might be synergistic when evaluated within the ICU setting. However, more careful work is required to understand the physiological challenges in the delivery of these interventions. Combining these interventions in post-ICU settings is currently under-investigated, but may be important to understand any potential benefits to patient longitudinal recovery.

Protein supplementation in critical illness: why, when and how?

PURPOSE OF REVIEW

In critically ill patients, optimal protein provision remains a challenge given the wide range in recommended protein delivery in international guidelines and the lack of robust, high quality evidence. As patients are confronted with poor functional outcomes after admission, often attributed to muscle wasting and persisting for multiple years, there is a pressing need for optimal nutritional strategies in the ICU, particularly including protein. This review will discuss the recent literature with regard to purpose, timing and mode of protein delivery.

RECENT FINDINGS

Recent studies on the effect of dose and timing of protein on clinical and functional outcomes are largely observational in nature and the protein delivery considered as "high" still often only nears the lower end of current recommendations. The majority of trials observed no effect of protein supplementation on mortality, muscle strength or function, though some report attenuation of muscle volume loss, especially when combined with muscle activation. There is no strong evidence that ICU patients should receive supplementation with any specific amino acids.

SUMMARY

Though adequate protein provision is likely important, it is difficult to come to a uniform conclusion regarding dosing and timing due to conflicting results in mostly observational studies as well as different cut-off values for high, moderate and low protein intake. This topic is currently subject to large clinical trials.

Toward nutrition improving outcome of critically ill patients: How to interpret recent feeding RCTs?

Although numerous observational studies associated underfeeding with poor outcome, recent randomized controlled trials (RCTs) have shown that early full nutritional support does not benefit critically ill patients and may induce dose-dependent harm. Some researchers have suggested that the absence of benefit in RCTs may be attributed to overrepresentation of patients deemed at low nutritional risk, or to a too low amino acid versus non-protein energy dose in the nutritional formula. However, these hypotheses have not been confirmed by strong evidence. RCTs have not revealed any subgroup benefiting from early full nutritional support, nor benefit from increased amino acid doses or from indirect calorimetry-based energy dosing targeted at 100% of energy expenditure. Mechanistic studies attributed the absence of benefit of early feeding to anabolic resistance and futile catabolism of extra provided amino acids, and to feeding-induced suppression of recovery-enhancing pathways such as autophagy and ketogenesis, which opened perspectives for fasting-mimicking diets and ketone supplementation. Yet, the presence or absence of an anabolic response to feeding cannot be predicted or monitored and likely differs over time and among patients. In the absence of such monitor, the value of indirect calorimetry seems obscure, especially in the acute phase of illness. Until now, large feeding RCTs have focused on interventions that were initiated in the first week of critical illness. There are no large RCTs that investigated the impact of different feeding strategies initiated after the acute phase and continued after discharge from the intensive care unit in patients recovering from critical illness.