Metabolic response during neuromuscular electrical stimulation in critically ill patients with deep sedation: a prospective observational study

BACKGROUND: Neuromuscular electrical stimulation (NMES) is a potential strategy to counteract skeletal muscle atrophy in critically ill patients unable to engage in early mobilization. However, it is difficult to confirm whether the exercise load applied by NMES is sufficient to elicit a physiological effect in patients under sedation or with impaired consciousness, as the appropriate stimulus intensity and exercise load of NMES are generally assessed using subjective responses. This study aimed to evaluate changes in energy expenditure during NMES in sedated, mechanically ventilated patients using indirect calorimetry. METHODS: This single-center observational study included 22 mechanically ventilated patients under deep sedation in the intensive care unit (ICU). Energy expenditure was measured using indirect calorimetry during NMES sessions. The primary outcome was the difference in energy expenditure before and during NMES. Multivariable linear regression analysis was performed to calculate the adjusted mean difference in energy expenditure. A clinically meaningful increase in energy expenditure attributable to NMES was predefined as 150 kcal/day, which was assumed based on an increase in energy expenditure when sitting on the edge of the bed. RESULTS: In total, 26 NMES sessions involving 22 participants were included in the analysis. The mean energy expenditure was 1,137 ± 170 kcal/day pre-NMES and 1,350 ± 228 kcal/day during NMES. The adjusted increase in energy expenditure during NMES was 213.8 kcal/day (95% confidence interval, 137.1-290.3). This increase reached statistical significance when tested against the predefined threshold of 150 kcal/day (P = 0.02). CONCLUSIONS: The exercise load provided by NMES could be objectively assessed by measuring increases in energy expenditure. Although a statistically significant increase in energy expenditure was observed during NMES compared to pre-NMES levels, the magnitude of this increase was minimal. Further research is needed to determine whether NMES protocols that enhance energy expenditure are associated with muscle mass preservation, strength maintenance, and the prevention of ICU-acquired weakness.