Nutrition therapy and critical illness: practical guidance for the ICU, post-ICU, and long-term convalescence phases

Advances in ICU medicine have resulted in a decrease in mortality due to critical illness, although an increasing number of patients discharged from ICU, have a decreased quality of life (QoL) with prolonged functional disabilities. Compromised quality of life in critically ill patients is related to a spectrum of physical, social, emotional, and neurocognitive function impairment. These complex tasks, necessary for independent living, are an important component of post-ICU functional outcomes. Frequently, nutrition targets are not achieved in any phase of recovery.

After hospital discharge, an increasing number of patients enter post-acute care facilities at substantial additional costs to recover from critical illness and ICU-acquired weakness.
Post-intensive care syndrome (PICS) was agreed upon by Needham et al (2012) as the recommended term to describe new or worsening problems in physical, cognitive, or mental health status arising after a critical illness and persisting beyond acute care hospitalization.

Improving care for intensive care survivors and their families requires collaboration between practitioners and researchers in both the inpatient and outpatient settings. Strategies and further research is required to address post-ICU QoL to improve outcomes for ICU survivors. According to the researchers of this review, van Zanten et al., optimal nutrition throughout hospitalization and recovery is one strategy that can be implemented to improve functional and QoL outcomes at a relatively low cost.

Objectives

The objective of this literature review was to collate and review the recent guidelines on nutrition therapy and the role of macronutrient timing to provide an overview of practical guidance for each stage of ICU hospitalization and recovery phases.

Results from the randomised controlled trials (RCTs) PERMIT and TARGET found no difference in endpoints after underfeeding versus normocaloric feeding or energy-dense feeding versus normocaloric feeding. These results contradict the observational study findings. This may be due to the RCTs energy targets based on equations rather than indirect calorimetry with similar protein intake in both arms of the trial.  The TARGET and EAT-ICU trials indicated that early caloric intake leads to increased hyperglycemic episodes and insulin therapy. To prevent prolonged caloric deficits, a limited deficit of 20-30% in the first ICU week appears to be optimal.

Several studies have shown that caloric restriction to 500 kcal/day or less than 50% of target for 2–3 days is essential to prevent attributable mortality from refeeding syndrome (RFS) which is characterised by electrolyte shifts in response to the reintroduction of nutrition after a period of starvation. ICU patients experience refeeding hypophosphatemia  (drop below 0.65mmol/l) within 72 hours after the start of nutrition.
 

The importance of proteins during ICU Stays
 

Several observational studies have shown that higher protein intake is associated with morbidity and mortality reduction as compared to lower intake of protein. Patients with Multiple Organ Dysfunction syndrome (MODS) have shown a loss of muscle mass of up to 1kg/day within the first 10 days of ICU stay.

In sepsis patients, the outcome may be different as suggested in the PROCASEPT retrospective study. In this study medium protein intake at days 4-7 was associated with lower 6-month mortality.

In patients treated with early high protein intake within the first 3 days of ICU stay, mortality increases, as shown in both the EPANIC and PROTINVENT studies. Although the highest 6-month mortality was in patients receiving an average protein intake less than 0.8g/kg/day.

It may be a challenge to achieve the protein targets without overfeeding, therefore the ESPEN guidelines recommend increasing both caloric and protein targets in steps of 25% starting with enteral nutrition, after progression the protein target should be at least 1.3 g/kg/day to reach the target on day 4 of ICU stay.

Most tube feeds (and parenteral nutrition products) have a low-protein-to-energy ratio. Van Zanten (2018) studied a very-high-protein-to-energy ratio intact protein enteral feed compared to an isocaloric standard high-protein feed in an international RCT. The results indicated an average intake of 1.5g/kg/day on day 5 (mean protein intake 0.75g/kg/day as indicated by higher amino acid concentration) whereas the standard high-protein feed was unable to achieve intake above 1.0-1.2g/kg/day. It appears that neither pre-digested nor hydrolyzed enteral feeds are better tolerated than intact protein feeds. It is not recommended to initiate supplemental parenteral nutrition (SPN) before days 3–7, as the risk of overfeeding may increase infectious morbidity. Additional protein supplements are unnecessary in most patients when the protein ratio of total calories is higher than 30-32%.
 

Nutrition Therapy during the post-ICU stay
 

To improve QoL, optimal calorie/protein intake is necessary to restore functional muscle mass and to prevent further loss. There is a marked increase in metabolic needs during the recovery phase as demonstrated by Indirect calorimetry studies, with Total Energy Expenditure (TEE) increasing as much as ~ 1.7-fold above resting EE (REE). Anabolic thresholds for protein synthesis (anabolic resistance) are assumed to be higher in many post-ICU patients who are older and frail. Therefore, a protein intake of 1.5–2.5 g/kg/day should be considered.
The monitoring of caloric and protein intake in post-ICU patients indicates low ratios of intake versus need in ward-based nutritional care. 

Nutrition Therapy after hospital discharge and convalescence
 

Following starvation, significant calories are needed to recover from the marked muscle loss that occurs -typically 3000–4500 kcal/day and proteins up to 1.5–2.5 g/kg/day. Following an ICU stay, patients who have a significant decrease in muscle mass and strength, require targeted nutrition that increases calorie and protein intake. It is recommended that all ICU survivors use high-protein oral nutrition supplement (HP-ONS) as part of the post-hospital discharge care, for at least 3 months. 
 

ONS has been demonstrated to:

• reduce mortality, 

• reduce hospital complications, 

• reduce hospital readmissions, 

• shorten length of stay, and 

• reduce hospital costs

Persistent catabolism and hypermetabolism may challenge ICU survivors for a long period of time. Anabolic and anticatabolic agents, such as propranolol, oxandrolone, which are targeted at restoring lean muscle mass may allow for improved post-ICU survival and recovery of QoL.

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Conclusion
 

Optimal nutrition and metabolic therapies should be provided throughout all phases of critical illness as essential options to improve long-term ICU outcomes.

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Reproduced under a Open Access Guidelines 

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