Comparison of Two Techniques to Assess Muscle Mass Loss During ICU Stay: Muscle Ultrasound vs Bioelectrical Impedance Analysis

Background and aims: Muscle wasting is a prevalent issue among long-term critically ill patients and is associated with adverse clinical outcomes. Evaluating muscle mass in the ICU presents challenges due to the lack of a consistent methodology and the significant impact of fluid balance range in ICU patients. This prospective study aimed to compare the utility of bioelectrical impedance analysis (BIA) and ultrasound (US) for monitoring muscle wasting in critically ill patients over an initial seven-day period of critical illness. Methods: Conducted in a tertiary teaching hospital's mixed ICU, the study included adult patients with ICU stays exceeding seven days. Measurements were taken on Day 1 (within 24 hours of ICU admission), Day 5, and Day 7. Results: Out of 101 enrolled patients, 74 were male, with a mean age of 55.3 (SD 14.8) years. The mean APACHE II score was 18.2 (SD 7.2), and the Day 1 SOFA score was 7.9 (SD 3.2). The ICU survival rate was 65%, and the mean ICU length of stay was 19.2 (SD 19.2) days. Statistically significant muscle mass loss was detected by US measurement, demonstrating the relative change in general muscle thickness: -2.5% (SD 11.8) by Day 5 and -6.5% (SD 12.4) by Day 7 (P < 0.001). BIA demonstrated no significant change in phase angle, as the relative change by Day 5 was -3.3% (SD 19.9) and by Day 7 it was -1.9% (SD 21.9), with no significant difference (P = 0.374). Conclusions: Ultrasound was a more suitable method for assessing and monitoring muscle wasting during ICU stays, while bioelectrical impedance analysis failed to demonstrate a comparable degree of muscle loss at Days 5 and 7. This study highlights the importance of selecting an appropriate assessment method based on the specific clinical context, emphasizing the reliability of US in evaluating muscle wasting among critically ill patients.