Bioimpedance-assessed muscle wasting and its relation to nutritional intake during the first week of ICU: a pre-planned secondary analysis of Nutriti Study

Abstract

Background: Muscle mass evaluation in ICU is crucial since its loss is related with long term complications, including physical impairment. However, quantifying muscle wasting with available bedside tools (ultrasound and bioimpedance analysis) must be more primarily understood. Bioimpedance analysis (BIA) provides estimates of muscle mass and phase angle (PA). The primary aim of this study was to evaluate muscle mass changes with bioimpedance analysis during the first 7 days after ICU admission. Secondary aims searched for correlations between muscular loss and caloric and protein debt.

Methods: Patients with an expected ICU-stay ≥ 72 h and the need for artificial nutritional support were evaluated for study inclusion. BIA evaluation of muscle mass and phase angle were performed at ICU admission and after 7 days. Considering the difference between ideal caloric and protein targets, with adequate nutritional macronutrients delivered, we calculated the caloric and protein debt. We analyzed the potential correlation between caloric and protein debt and changes in muscle mass and phase angle.

Results: 72 patients from September 1st to October 30th, 2019 and from August 1st to October 30th, 2021 were included in the final statistical analysis. Median age was 68 [59-77] years, mainly men (72%) admitted due to respiratory failure (25%), and requiring invasive mechanical ventilation for 7 [4-10] days. Median ICU stay was 8 [6-12] days. Bioimpedance data at ICU admission and after 7 days showed that MM and PA resulted significantly reduced after 7 days of critically illness, 34.3 kg vs 30.6 kg (p < 0.0001) and 4.90° vs 4.35° (p = 0.0004) respectively. Mean muscle loss was 3.84 ± 6.7 kg, accounting for 8.4% [1-14] MM reduction. Correlation between caloric debt (r = 0.14, p = 0.13) and protein debt (r = 0.18, p = 0.13) with change in MM was absent. Similarly, no correlation was found between caloric debt (r = -0.057, p = 0.631) and protein debt (r = -0.095, p = 0.424) with changes in PA.

Conclusions: bioimpedance analysis demonstrated that muscle mass and phase angle were significantly lower after 7 days in ICU. The total amount of calories and proteins does not correlate with changes in muscle mass and phase angle.

Keywords: Bioimpedance analysis; Caloric debt; Critically ill patient; ICU acquired weakness; Muscle wasting; Nutrition; Proteins.

Fig. 1

Study flowchart

Fig. 2

Correlations between MM and PA at ICU admission and their changes after 7 days of ICU stay. In the left part of the figure, it is shown the correlation between MM and PA at ICU admission (r = 0.67, p < 0.0001): In the right part, MM and PA changes after 7 days from admission demonstrated still to be correlated significantly (r = 0.68, p < 0.0001)

Fig. 3

Correlation between Kcal_DEBT and Prot_DEBT, and changes in MM after 7 days of ICU stay. No significant correlation was found between variations in MM (ΔMM) and protein debt (Prot_DEBT) or caloric debt (Kcal_DEBT) during the first 7 days after ICU admission (p = 0.13 for both correlations)

Fig. 4

Correlation between Kcal_DEBT and Prot_DEBT, and changes in PA after 7 days of ICU stay. No significant correlation was found between variations in PA (ΔPA) and protein debt (Prot_DEBT) or caloric debt (Kcal_DEBT) during the first 7 days after ICU admission (p = 0.42 and p = 0.63 respectively)