Current View on the Issue of Protein Intake in Critically Ill Patients

Focus on Effective Nutrition

Critically ill patients require special nutritional care, which includes increased protein intake. According to clinical study results, adequate protein administration translates into lower mortality and improved quality of life for patients. Many critically ill patients have various restrictions regarding fluid intake, and adequately concentrated protein solutions have become a key element of enteral and parenteral nutrition.

A current topic in intensive care, however, remains the proper calculation of nutritional needs and the optimal amount of protein during different disease stages. The authors of the cited review article focused on current findings available from publications searched via Medline, Embase, and EBM Reviews databases and clinical guidelines.

Meeting Nutritional Needs Based on Current Status

Patients' nutritional needs change over time. Protein loss from the body occurs very quickly during the acute phase of a severe condition, and losses remain high even more than 5 days after admission to the intensive care unit (ICU) and subsequently during recovery. In contrast, the body's total energy requirement is low during the acute phase of the disease, as the body can generate up to 75% of its energy intake. The proportion of the non-protein component in total energy intake increases during illness and recovery, and nutritional care for patients in the ICU and after discharge should reflect all these insights.

Proper Timing Is Key

Results from retrospective observational studies show the benefits of appropriately timed administration of optimal amounts of protein to critically ill patients. The highest 6-month survival rate was observed in patients who had continuously increased protein intake during ICU hospitalization, from 0.8 g/kg/day for the first 2 days to > 1.2 g/kg/day after 5 days of hospitalization. Conversely, the worst long-term outcomes were observed in patients with generally low protein intake. Protein deficiency was associated with higher mortality both during the ICU stay and after transfer to another hospital ward.

In a Dutch cohort study of patients who were alive 90 days after ICU discharge, higher protein intake was found during the first 10 days of ICU stay. Each additional 1 g of protein/kg/day corresponded to an 18% reduction in 90-day mortality.

Assessment of Nutritional Status – Protein Levels

In the past, a simplified nitrogen balance equation was used to calculate protein needs. However, 24-hour urine collection is problematic in many situations and does not account for fluid losses through sweating, wounds, or drains. Other methods are based on measuring plasma protein concentrations and serum albumin and prealbumin levels. However, serum albumin responds slowly to changes in protein intake, limiting its value as a protein marker in enteral or parenteral nutrition. Some studies report that serum albumin and prealbumin levels do not correlate with protein amounts administered and total energy intake.

New Assessment Possibilities

The NAChO study is investigating methods that allow the monitoring of nutritional parameters over time, using blood and urine nutrient analysis, muscle tissue changes, electrophysiology, body composition analysis, brain MRI, and clinical patient status. The results of this study could help establish the most appropriate tools for screening and monitoring nutritional status.

Methods for assessing nutritional status based on lean mass analysis are still in their infancy, but preliminary data suggest that this approach could play an important role in evaluating the condition of ICU patients in the future.

Protein Intake Recommendations for ICU Patients

Several clinical guidelines agree in their recommendations regarding proteins and emphasize the importance of increased protein intake for ICU patients. Especially for patients with malnutrition, they stress the need to focus on protein intake rather than just caloric intake. According to the guidelines, initial protein intake for ICU patients should reach 1.5–2.5 g/kg/day.

In the past, increased protein intake in critically ill patients was problematic due to a lack of highly concentrated protein solutions and the associated burden of large volumes of fluids administered. However, highly concentrated solutions are now available for enteral and parenteral nutrition and are well-suited for elderly patients, those with burns, severe injuries, and ICU hospitalizations in general.

Conclusion

Products with various nutritional parameters enable tailored nutritional care for the patient, considering current protein needs and other components, minimizing risks associated with artificial nutrition administration.

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Sources:
1. De Waele E., Jakubowski J. R., Stocker R., Wischmeyer P. E. Review of evolution and current status of protein requirements and provision in acute illness and critical care. Clin Nutr 2021; 40 (5): 2958–2973, doi: 10.1016/j.clnu.2020.12.032.
2. Koekkoek W. A. C. K., van Setten C. H. C., Olthof L. E. et al. Timing of PROTein INtake and clinical outcomes of adult critically ill patients on prolonged mechanical VENTilation: the PROTINVENT retrospective study. Clin Nutr 2019; 38 (2): 883–890, doi: 10.1016/j.clnu.2018.02.012.
3. Weijs P. J. M., Mogensen K. M., Rawn J. D., Christopher K. B. Protein intake, nutritional status and outcomes in ICU survivors: a single center cohort study. J Clin Med 2019; 8 (1): 43, doi: 10.3390/jcm8010043.
4. Schefold J. C., Messmer A. S., Wenger S. et al. Nutrient pattern analysis in critically ill patients using Omics technology (NAChO) – study protocol for a prospective observational study. Medicine (Baltimore) 2019; 98 (1): e13937, doi: 10.1097/MD.0000000000013937.