This study revealed that critically ill patients in the ICU who develop ICU-acquired weakness (ICU-AW) are more dependent on vasopressor drugs and mechanical ventilation therapy, indicating a more severe condition and poorer prognosis. This is supported by the trends in data of variables such as RF-CSA, TA-MT, SMI, MUAC, TBW, Protein, and PA levels in body composition measurements. Therefore, timely recognition and diagnosis of ICU-AW are of utmost importance.
In recent years, standardized sepsis treatment has yielded positive outcomes, resulting in a significant reduction in mortality [19]. However, survivors may encounter a decline in functional status and muscular weakness due to the impact of sepsis, which can adversely affect their subsequent quality of life [20]. This situation can be particularly exacerbated in patients with tumors who already experience chronic muscle wasting. In an early study, the changes in quadriceps muscles and the protein/DNA ratio over time were evaluated, and the results revealed that during the first week, muscle mass decreased in nearly all cases due to reduced protein synthesis and increased protein breakdown [16]. This study confirmed that patients with ICU-acquired weakness (ICU-AW) displayed significantly reduced skeletal muscle rectus femoris cross-sectional area (RF-CSA) and tibialis anterior muscle thickness (TA-MT) compared to those without ICU-AW, and △RF-CSA exhibited higher accuracy in diagnosing ICU-AW in comparison to △TA-MT. Even △MUAC, determined from the upper arm circumference, demonstrated higher diagnostic value for ICU-AW compared to △TA-MT.
Some studies have demonstrated that the skeletal muscle index (SMI) is a predictive indicator of ICU-acquired weakness (ICU-AW) in sepsis patients [21]. Currently, the calculation of the whole-body skeletal muscle index entails dividing the sum of skeletal muscle areas measured at the L3 vertebral CT level by the square of height [22]. However, this method is expensive and exposes patients to a certain amount of radiation. Given the limited conditions for examination, this method may not be optimal for most critically ill patients with tumors, particularly during the sepsis period. Therefore, utilizing bioelectrical impedance analysis to calculate SMI and determine whole-body skeletal muscle mass offers advantages such as accuracy, ease of operation, and radiation-free measurements [17]. Studies have revealed that patients in the ICU-AW group exhibited significantly lower SMI upon admission to the ICU compared to the non-ICU-AW group, and measuring SMI at this point can predict the occurrence of ICU-AW in sepsis patients [21, 23, 24]. In this study, SMI measured by bioelectrical impedance analysis indicated that ICU-AW patients experienced a more substantial decrease in SMI, and △SMI demonstrated good diagnostic accuracy for ICU-AW. Protein, another important parameter measured by bioelectrical impedance analysis, was observed to have reduced content in all sepsis patients admitted to the ICU due to reduced protein synthesis and increased breakdown during sepsis. However, ICU-AW patients exhibited a more notable decrease in protein content compared to non-ICU-AW patients, and △Protein demonstrated higher diagnostic accuracy for ICU-AW. Total body water (TBW) is another important parameter derived from bioelectrical impedance analysis. The initial fluid resuscitation in the early stages of sepsis treatment often leads to a high blood volume status among patients [25], resulting in an elevation of the baseline TBW value. However, as a consequence of self-consumption and sepsis fluid management, TBW exhibits a downward trend. ICU-AW patients experienced a more significant decrease in TBW compared to patients without ICU-AW, and △TBW demonstrated good diagnostic accuracy for ICU-AW when compared to other parameters.
The commonly utilized sepsis scoring systems, APACHE II and SOFA scores, have been identified as significant risk factors for ICU-acquired weakness (ICU-AW)[26, 27]. However, recent studies have indicated that APACHE II and SOFA scores alone lack sufficient diagnostic capability for ICU-AW [28, 29]. In this study, the initial APACHE II and SOFA scores demonstrated diagnostic performance comparable to △RF-CSA, △SMI, △Protein, and △TBW, but further validation is necessary by expanding the sample size. When the APACHE II and SOFA scores were combined to establish a diagnostic model, the diagnostic rate of ICU-AW reached 56.6%. Considering the promptness and convenience of obtaining APACHE II and SOFA scores, in contrast to predicting the occurrence of ICU-AW through changes in muscle and body composition after 72 hours of treatment, the combined diagnostic model of APACHE II and SOFA scores exhibited favorable early diagnostic efficacy. Among other multifactorial diagnostic models, the △RF-CSA combined with △SMI model, which was established on muscle indicators, displayed the highest area under the receiver operating characteristic (ROC) curve of 0.849 and therefore the highest diagnostic value, further reinforcing the correlation between severe muscle wasting and the diagnosis of ICU-AW in patients with sepsis.
In addition, a noteworthy finding in the treatment of sepsis in tumor patients was the sole parameter that exhibited an upward trajectory - the phase angle (PA). The phase angle (PA) serves as a reliable indicator of cellular health, as changes in cell membrane integrity signify cellular malnutrition or death[18]. Higher values of the phase angle indicate stronger cell integrity and improved cell function. In the early stages of sepsis, cell membrane integrity is compromised due to severe infection and a systemic inflammatory response. However, with the administration of sepsis treatment, cell membrane stability improves, leading to enhanced cellular water and energy metabolism and consequently causing an upward trend in phase angle values. Additionally, this upward trend in phase angle is more prominent in patients with ICU-acquired weakness (ICU-AW) since they initially display lower phase angle values compared to non-ICU-AW patients (averaging at 3.23° compared to 3.71°). Following active sepsis treatment, the increase in phase angle is even more substantial in ICU-AW patients (mean difference of 0.653 compared to 0.571).
However, this study also has several limitations. First, our ultrasound examinations only measured muscle thickness or area. However, other studies suggest that muscle echogenicity and feathering angle may also provide valuable diagnostic information. Additionally, measurements from bioelectrical impedance analysis may potentially be influenced by various factors including changes in body position and cooperation level, even if the electrodes are properly placed according to limb markings. Unfortunately, due to limitations in conducting muscle biopsy and electromyography, the analysis of pathology and electromyography on the muscles of patients with ICU-AW was not carried out. Moreover, the MRC score assessment was conducted on the 5th day after ICU admission. It is important to note that a longer stay in the ICU might increase the incidence of subsequent ICU-AW, warranting further investigation on this matter.