Novel approaches to metabolic assessment and structured exercise to promote recovery in ICU survivors

Abstract

Purpose of review: Survivorship or addressing impaired quality of life (QoL) in ICU survivors has been named 'the defining challenge of critical care' for this century to address this challenge; in addition to optimal nutrition, we must learn to employ targeted metabolic/muscle assessment techniques and utilize structured, progressive ICU rehabilitative strategies.

Recent findings: Objective measurement tools such as ccardiopulmonary exercise testing (CPET) and muscle-specific ultrasound show great promise to assess/treat post-ICU physical dysfunction. CPET is showing that systemic mitochondrial dysfunction may underlie development and persistence of poor post-ICU functional recovery. Finally, recent data indicate that we are poor at delivering effective, early ICU rehabilitation and that there is limited benefit of currently employed later ICU rehabilitation on ICU-acquired weakness and QoL outcomes.

Summary: The combination of nutrition with effective, early rehabilitation is highly likely to be essential to optimize muscle mass/strength and physical function in ICU survivors. Currently, technologies such as muscle-specific ultrasound and CPET testing show great promise to guide ICU muscle/functional recovery. Further, we must evolve improved ICU-rehabilitation strategies, as current methods are not consistently improving outcomes. In conclusion, we must continue to look to other areas of medicine and to athletes if we hope to ultimately improve 'ICU Survivorship'.

Figure 1:

MuscleSound® echo-intensity heatmap of the rectus femoris muscle, showing different stage of muscle wasting in a clinical population.

Figure 2:

Segmented CT analysis at the level of L3; blue is the subcutaneous adipose tissue (SAT) layer, red is muscle, green is intramuscular adipose tissue (IMAT) and yellow is visceral adipose tissue (VAT). MuscleSound® echo-intensity heatmap of the rectus femoris muscle.

Figure 3:

Central role of mitochondrial dysfunction in impaired physical and muscle recovery in critical illness.

Figure 4:

Proposed novel metabolic assessment and intervention pathways across all phases of critical illness to promote survivorship and optimal post-ICU muscle and physical recovery. (Abbreviations- CPET- Cardiopulmonary Exercise Testing, HIT- High Intensity Training targeted to patients’ abilities by CPET testing results)