Protein metabolism and requirements in the ICU

Physical and respiratory therapy in the critically ill patient with obesity: a narrative review

Obesity has become increasingly prevalent in the intensive care unit, presenting a significant challenge for healthcare systems and professionals, including rehabilitation teams. Caring for critically ill patients with obesity involves addressing complex issues. Despite the well-established and safe practice of early mobilization during critical illness, in rehabilitation matters, the diverse clinical disturbances and scenarios within the obese patient population necessitate a comprehensive understanding. This includes recognizing the importance of metabolic support, both non-invasive and invasive ventilatory support, and their weaning processes as essential prerequisites. Physiotherapists, working collaboratively with a multidisciplinary team, play a crucial role in ensuring proper assessment and functional rehabilitation in the critical care setting. This review aims to provide critical insights into the key management and rehabilitation principles for obese patients in the intensive care unit.

High protein intake and nitrogen balance in patients receiving venovenous extracorporeal membrane oxygenation: A descriptive cohort study

BACKGROUND

This retrospective cohort study sought to describe the ability of high protein regimens to achieve nitrogen equilibrium in patients receiving venovenous extracorporeal membrane oxygenation (VV ECMO).

METHODS

Patients aged ≥18 years with a documented nitrogen balance study (NB) on VV ECMO between February 2018 and December 2021 were included. Studies with incomplete 24-h urine collections or changes in blood urea nitrogen ≥10 mg/dl were excluded. Data were summarized, correlation between first NB and potentially contributing variables was assessed with Kendall tau. Subanalysis described findings after stratifying for weight class (obese vs nonobese) and duration of VV ECMO at the time of NB.

RESULTS

A total of 68 NBs in 30 patients were included; 47% of the cohort had obesity. The number of NBs per patient was 2.2 ± 1.1, which were completed on a median of 31.5 (interquartile range: 16, 53.8) days receiving ECMO. Nitrogen equilibrium or positive balance was achieved in 72% of studies despite elevated nitrogen excretion. Patients received 87.9 ± 16.8% of prescribed protein on NB days for average intakes of 2.4 ± 0.4 g/kg of actual weight per day and 2.4 ± 0.5 g/kg of ideal weight per day in patients without and with obesity. Median NB in patients without obesity was -1.46 (-8.96, 2.98) g/day and -0.21 (-10.58, 4.04) g/day in patients with obesity. A difference in median NB after stratification for timing was observed (P = 0.029).

CONCLUSION

Nitrogen equilibrium can be achieved with high protein intake in adults receiving VV ECMO. NB monitoring is one tool to individualize protein prescriptions throughout the course of VV ECMO.

Protein and energy intake in intensive care unit survivors during the first year of recovery: A descriptive cohort study

BACKGROUND

Many intensive care unit (ICU) survivors suffer long-term health issues that affect their quality of life. Nutrition inadequacy can limit their rehabilitation potential. This study investigates nutrition intake and support during ICU admission and recovery.

METHODS

In this prospective cohort study, 81 adult ICU patients with stays ≥48 h were included. Data on dietary intake, feeding strategies, baseline and ICU characteristics, and 1-year outcomes (physical health and readmission rates) were collected. The number of patients achieving 1.2 gram per kilogram per day of protein and 25 kilocalories per kilogram per day at 3 months, 6 months, and 12 months after ICU admission was recorded. The impact of dietary supplementation during the year was assessed. Baseline characteristics, intake barriers, and rehabilitation's influence on nutrition intake at 12 months were evaluated, along with the effect of inadequate intake on outcomes.

RESULTS

After 12 months, only 10% of 60 patients achieved 1.2 g/kg/day protein intake, whereas 28% reached the advised 25 kcal/kg/day energy target. Supplementary feeding significantly increased protein intake at 3, 6, and 12 months (P = 0.003, P = 0.012, and P = 0.033, respectively) and energy intake at 3 months (P = 0.003). A positive relation was found between female sex and energy intake at 12 months after ICU admission (β = 4.145; P = 0.043) and taste issues were independently associated with higher protein intake (β = 0.363; P = 0.036). However, achieving upper-quartile protein or energy intake did not translate into improved physical health outcomes.

CONCLUSION

Continuous and improved nutrition care is urgently needed to support patients in reaching nutrition adequacy.

How much underfeeding can the critically ill adult patient tolerate?

Critical illness leads to significant metabolic alterations that should be considered when providing nutritional support. Findings from key randomized controlled trials (RCTs) indicate that underfeeding (<70% of energy expenditure [EE]) during the acute phase of critical illness (first 7 days of intensive care unit [ICU] admission) may not be harmful and could instead promote autophagy and prevent overfeeding in light of endogenous energy production. However, the optimal energy target during this period is unclear and full starvation is unlikely to be beneficial. There are limited data regarding the effects of prolonged underfeeding on clinical outcomes in critically ill patients, but recent studies show that oral food intake is suboptimal both in the ICU and following discharge to the acute care setting. It is hypothesized that provision of full nutrition (70-100% of EE) may be important in the recovery phase of critical illness (>7 days of ICU admission) for promoting recovery and rehabilitation; however, studies on nutritional intervention delivered from ICU admission through hospital discharge are needed. The aim of this review is to provide a narrative synthesis of the existing literature on metabolic alterations experienced during critical illness and the impact of underfeeding on clinical outcomes in the critically ill adult patient.

Augmented Renal Clearance, Muscle Catabolism and Urinary Nitrogen Loss: Implications for Nutritional Support in Critically Ill Trauma Patients

The main objective of this pilot study was to determine the association between augmented renal clearance (ARC), urinary nitrogen loss and muscle wasting in critically ill trauma patients. We conducted a retrospective analysis of a local database in 162 critically ill trauma patients without chronic renal dysfunction. Nutritional-related parameters and 24 h urinary biochemical analyses were prospectively collected and averaged over the first ten days after admission. Augmented renal clearance was defined by a mean creatinine clearance (CL_CR) > 130 mL/min/1.73 m². The main outcome was the cumulated nitrogen balance at day 10. The secondary outcome was the variation of muscle psoas cross-sectional area (ΔCSA) calculated in the subgroup of patients who underwent at least two abdominal CT scans during the ICU length of stay. Overall, there was a significant correlation between mean CL_CR and mean urinary nitrogen loss (normalized coefficient: 0.47 ± 0.07, p < 0.0001). ARC was associated with a significantly higher urinary nitrogen loss (17 ± 5 vs. 14 ± 4 g/day, p < 0.0001) and a lower nitrogen balance (−6 ± 5 vs. −4 ± 5 g/day, p = 0.0002), without difference regarding the mean protein intake (0.7 ± 0.2 vs. 0.7 ± 0.3 g/kg/day, p = 0.260). In the subgroup of patients who underwent a second abdominal CT scan (N = 47), both ΔCSA and %ΔCSA were higher in ARC patients (−33 [−41; −25] vs. −15 [−29; −5] mm²/day, p = 0.010 and −3 [−3; −2] vs. −1 [−3; −1] %/day, p = 0.008). Critically ill trauma patients with ARC are thus characterized by a lower nitrogen balance and increased muscle loss over the 10 first days after ICU admission. The interest of an increased protein intake (>1.5 g/kg/day) in such patients remains a matter of controversy and must be confirmed by further randomized trials.

Nitrogen balance in mechanically ventilated obese patients

ABSTRACT Objective This study aimed to evaluate if the protein intake recommendations for obese critically ill requiring mechanical ventilation are sufficient to promote a positive or neutral nitrogen balance. Methods Cross-sectional study that included 25 obese, ≥18 years old, undergoing mechanical ventilation and who were target to receive high-protein enteral nutrition therapy (2.0-2.5g/kg ideal body weight). Clinical, nutritional and biochemical variables were analyzed. Nitrogen balance was performed when patient was receiving full enteral nutrition therapy and was classified: positive when intake was greater than excretion; negative when excretion was greater than intake; neutral when both were equal. Results The characteristics of patients evaluated were 64.1±9.4 years old, clinical treatment 88%, body mass index 36.5±5.1kg/m2, nitrogen balance 0.3g/day (-5.3 to 4.8g/day), protein intake 2.1g/day (2.0-2.3g/kg) ideal body weight. Of individuals analyzed, 52% showed positive or neutral nitrogen balance with median of 4.23g/day 2.41 to 6.40g/day) in comparison to negative group with median of -5.27g/day (-10.38 to -3.86g/day). Adults had higher ratio of negative nitrogen balance (57.1%) than elderly (44.4%), with protein intake of 2.0 versus 2.1g/day, respectively. No correlation was found between nitrogen balance and variables assessed. Conclusion High-protein enteral nutrition therapy contributed to positive or neutral nitrogen balance for approximately half of obese ventilated individuals. With similar protein intake, elderly showed a higher proportion of positive or neutral nitrogen balance. Nitrogen balance can be influenced by various factors, so further studies are required to identify different protein needs in obese critically.