To quantify the changes in rectus femoris muscle size and quality from RRT initiation to hospital discharge. Secondarily, we examined rates of ICU-acquired weakness in this population.
A prospective observational study was performed at two ICUs from United States, including adults with AKI who required RRT (AKI-RRT). Primary outcomes were the change in rectus femoris cross-sectional area (CSA), muscle thickness (mT), and echointensity (EI) measured by ultrasound at RRT initiation (day 1), 3 and 7 days later, and at ICU- and hospital-discharge. To determine the significance of muscle wasting, AKI-RRT was compared to a historical group (n=21) with acute respiratory failure without AKI-RRT. We also measured the occurrence of ICU-acquired weakness by using the Medical Research Council Sum Score with the cut-off 48/60, exploring differences in demographic and clinical variables using Mann–Whitney U test based on clinical diagnosis on having or not having ICU-acquired weakness.
Patients (n=23) had a median age of 56 years [IQR 47–60] being 39% female, where their median duration of RRT, ICU, and hospital length of stay was 4 [IQR 1–7], 7 [IQR 5–15], and 13 [IQR 9–33] days, respectively. Six (26%) patients died in the ICU. The median baseline rectus femoris mT was 1.35 cm [1.1–1.7] which decreased by median -10% [-20 to -3] from day 1 to 7 and -17% [-22 to -8] from day 1 to hospital discharge. The median baseline rectus femoris CSA was 3.89 cm2 [3.3–4.4] which decreased by median -19% [-22 to -12] from day 1 to 7 and -15% [-24 to -12] from day 1 to hospital discharge. The median baseline rectus femoris EI was 92 au [70–101] which increased (worse quality) by median 14% [5 to 25] from day 1 to day 7 and 13% [0.5 to 28] from day 1 to hospital discharge. Changes of rectus femoris parameters across time were significant (CSA: F= 66.2, p0.001; mT: F=27.1, p0.001; EI: F=22.5, p0.001). There were no statistical differences in demographic or clinical data between the RRT and historical groups, with both groups showing statistically significant decreases in muscle mass and quality over time. At hospital discharge 67% of patients (n=10/15) had ICU-acquired weakness, and were younger, had longer RRT duration, and longer ICU times, but no differences were observed in ultrasound parameters compared to those without ICU-acquired weakness.
Patients with severe AKI are at high risk of acute muscle wasting with our data demonstrating a significant reduction in rectus femoris muscle mass and quality.
Two thirds of patients requiring RRT met criteria for clinical diagnosis of ICU-acquired weakness. The findings demonstrate the importance of examining muscle function in patients with severe AKI. Early identification may provide physiotherapists with opportunities to deliver targeted strategies to mitigate and improve patient-centered outcomes.
Muscle wasting
acute kidney injury
