Protein metabolism in critical illness

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.

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.

Association between early nutrition support and 28-day mortality in critically ill patients: the FRANS prospective nutrition cohort study

BACKGROUND

Current guidelines suggest the introduction of early nutrition support within the first 48 h of admission to the intensive care unit (ICU) for patients who cannot eat. In that context, we aimed to describe nutrition practices in the ICU and study the association between the introduction of early nutrition support (< 48 h) in the ICU and patient mortality at day 28 (D28) using data from a multicentre prospective cohort.

METHODS

The 'French-Speaking ICU Nutritional Survey' (FRANS) study was conducted in 26 ICUs in France and Belgium over 3 months in 2015. Adult patients with a predicted ICU length of stay > 3 days were consecutively included and followed for 10 days. Their mortality was assessed at D28. We investigated the association between early nutrition (< 48 h) and mortality at D28 using univariate and multivariate propensity-score-weighted logistic regression analyses.

RESULTS

During the study period, 1206 patients were included. Early nutrition support was administered to 718 patients (59.5%), with 504 patients receiving enteral nutrition and 214 parenteral nutrition. Early nutrition was more frequently prescribed in the presence of multiple organ failure and less frequently in overweight and obese patients. Early nutrition was significantly associated with D28 mortality in the univariate analysis (crude odds ratio (OR) 1.69, 95% confidence interval (CI) 1.23-2.34) and propensity-weighted multivariate analysis (adjusted OR (aOR) 1.05, 95% CI 1.00-1.10). In subgroup analyses, this association was stronger in patients ≤ 65 years and with SOFA scores ≤ 8. Compared with no early nutrition, a significant association was found of D28 mortality with early enteral (aOR 1.06, 95% CI 1.01-1.11) but not early parenteral nutrition (aOR 1.04, 95% CI 0.98-1.11).

CONCLUSIONS

In this prospective cohort study, early nutrition support in the ICU was significantly associated with increased mortality at D28, particularly in younger patients with less severe disease. Compared to no early nutrition, only early enteral nutrition appeared to be associated with increased mortality. Such findings are in contrast with current guidelines on the provision of early nutrition support in the ICU and may challenge our current practices, particularly concerning patients at low nutrition risk. Trial registration ClinicalTrials.gov Identifier: NCT02599948. Retrospectively registered on November 5th 2015.

The role of nutrition rehabilitation in the recovery of survivors of critical illness: underrecognized and underappreciated

Many survivors of critical illness face significant physical and psychological disability following discharge from the intensive care unit (ICU). They are often malnourished, a condition associated with poor outcomes, and nutrition remains problematic particularly in the early phases of ICU recovery. Yet nutrition rehabilitation, the process of restoring or optimizing nutritional status following illness, is seldom prioritized, possibly because it is an underrecognized and underappreciated area in critical care rehabilitation and research. To date, 16 original studies have been published where one of the objectives includes measurement of indices relating to nutritional status (e.g., nutrition intake or factors impacting nutrition intake) in ICU survivors. The primary aim of this narrative review is to provide a comprehensive summary of key themes arising from these studies which form the basis of our current understanding of nutritional recovery and rehabilitation in ICU survivors. ICU survivors face a multitude of barriers in achieving optimal nutrition that are of physiological (e.g., poor appetite and early satiety), functional (e.g., dysphagia, reduced ability to feed independently), and psychological (e.g., low mood, body dysmorphia) origins. Organizational-related barriers such as inappropriate feeding times and meal interruptions frequently impact an ICU survivor’s ability to eat. Healthcare providers working on wards frequently lack knowledge of the specific needs of recovering critically ill patients which can negatively impact post-ICU nutrition care. Unsurprisingly, nutrition intake is largely inadequate following ICU discharge, with the largest deficits occurring in those who have had enteral nutrition prematurely discontinued and rely on an oral diet as their only source of nutrition. With consideration to themes arising from this review, pragmatic strategies to improve nutrition rehabilitation are explored and directions for future research in the field of post-ICU nutrition recovery and rehabilitation are discussed. Given the interplay between nutrition and physical and psychological health, it is imperative that enhancing the nutritional status of an ICU survivor is considered when developing multidisciplinary rehabilitation strategies. It must also be recognized that dietitians are experts in the field of nutrition and should be included in stakeholder meetings that aim to enhance ICU rehabilitation strategies and improve outcomes for survivors of critical illness.