DISCUSSION
In this study the prevalance of sarcopenia was found to be 59% in the patients admitted to general ICU in a one-year period and most common in patients over 70 years of age. Sarcopenia was associated with the increasing in mortality, the prolongation in the lenght of staying at hospital and ICU.
EWGSOP reported the incidence of sarcopenia as 5.8-14.9% in the normal population, 4.1% in men and 16.6% in women (2). On the other hand, they reported that the incidence in the elderly was between 1-29% (17). Moisey et al found this figure to be 71% in aged trauma patients (18). However, the number of studies investigating the incidence of sarcopenia in critically ill patients is low. Sheean et al found the incidence of sarcopenia as 62% in patients who were admitted to ICU due to respiratory failure and followed up in mechanical ventilator (19). Joyce et al reported the incidence of sarcopenia in their patients hospitalized in their intensive care unit as 68% (13). Baggerman et al were reported that the prevalence of sarcopenia is approximately 30-70 % in intensive care units (5). In the present study, we found the incidence of sarcopenia in general ICU as 59%, similar to literature.
Malnutrition is closely related to sarcopenia in aged persons and plays an important role in the development of sarcopenia. Mundi et al showed that 50% of the critically ill patients were malnourished, which is the reason for impaired immune function, long-term ventilator dependence, increased infectious complications, and increased morbidity and mortality (20). It is important to evaluate the nutritional status of first admission in patients admitted to ICU, but it is difficult to assess the history of acute weight loss. Protein deficiency disrupts the immune system by increasing metabolic stres (21). Baumgartner et al found an association between albumin levels and sarcopenia (22). Kim et al reported that higher albumin levels were associated with a protective effect against declines in SMI (23). Although there was no difference in albumin levels in our patients, we found prealbumin levels lower in patients with sarcopenia. Prealbumin is a protein produced by the liver. Serum prealbumin had historically been used as a biomarker of malnutrition and as an important indicator of overall nutrition status among aged adults not suffering from acute illness. Chen et al reported that lower prealbumin levels were associated with higher sarcopenia prevelance. Therefore higher BMI and prealbumin levels may be protective factors against sarcopenia development among aged adults (24). We consider that muscle mass or strength might decline due to degradation of protein synthesis associated with low prealbumin, which may lead to an increased risk of sarcopenia in critical illness.
BMI is a parameter used in the evaluation of nutrition, based on height and weight. But body weight includes both fat and muscle mass. Therefore, it prevents us from making the accurate assessment for sarcopenia. Weijs et al reported that the measurement of muscle mass was a more important indicator than BMI (25). In some studies, acute sarcopenia due to muscle destruction and decreased protein synthesis has been shown in critically ill patients. Muscle volume decrement was shown as 17-30% in the first 10 days of the ICU (26). The use of BMI may also cause inaccurate results in the presence of diffuse edema, especially in obese patients. Albumin or other serum proteins are affected by the acute phase response and changes in the intravascular volume so prevent the use of as a marker for the assessment of nutritional status in the critical patient (27). In CT imaging, body compartments can be better distinguished, and abdominal fat tissue, visceral adipose tissue, intramuscular, and subcutaneous adipose tissue can be identified more accurately. Therefore, abdominal CT is defined as standard method for evaluating total body and skeletal muscle (21). Sheetz et al evaluated SMI in abdominal CT preoperatively and reported sarcopenia (28). Martin et al reported that SMI was closely related to mortality and associated with poor prognosis, especially in the aged patients (29). In the present study, abdominal CT was used for SMI evaluation. Patients were divided into two groups for SMI values based on Prado’s threshold values (16). SMI was found to be lower in patients over the age of 70 compared to those older than 40.
The general ICU population is very heterogeneous. The mortality of critically ill patients is still one of the most important issues, especially for the elderly patients with comorbidities. Most patients have sepsis, and suffering from chronic comorbidities such as cardiovascular failure, trauma, malnutrition or cancer. These comorbidities are associated with a decline of skeletal muscle mass, potentially leading to sarcopenia. Various scoring systems are used to predict mortality. However, these scoring systems have shown relatively poor predictable performance. We used APACHE II and SOFA scores in ICU. However, we couldn’t find any differences between the groups.
In several studies, it has been stated that low levels of vitamin D cause a decrease in muscle tension. Vitamin D deficiency should be treated to maintain vitamin D levels of 40 ng/mL and above (29,30). Any relationship between serum vitamin D levels and muscle mass was not found in this study.
In the presence of sarcopenia; length of mechanical ventilation, length of stay in ICU and hospital are longer and consequently an cost increases (28). Moisey et al found the number of days on ventilator and the number of days of intensive care to be higher. Hospital stay was longer and mortality was higher in the sarcopenic patients (18). Weijs et al they reported that low muscle mass evaluated with CT was related to increased duration of mechanical ventilation and increased duration of hospitalization and mortality (25). Kirk et al reported that the presence of preoperative sarcopenia increases the incidence of admission to the intensive care unit and prolongs the duration of discharge (21). The patients were admitted to ICU with a severe critical disease accompanied by comorbidities, protein catabolism, muscle atrophy and weakness. Sarcopenia caused an increase in mortality, a prolongation in the lenght of hospitalization and ICU stay. In the present study, mortality was increased and lengths of intensive care and hospital stay were prolonged in the presence of sarcopenia,
Limitations of the study; it was a retrospective and single centered study. Data were obtained directly from the medical records of the patients. Patients with abdominal CT for any reason were included. Primary or secondary sarcopenia could not be differentiated because abdominal CT at any time was evaluated during the treatment in the ICU. There were cases that could not be evaluated because of missing data. Response to treatment could not be evaluated (adequate nutrition, specifically protein and micronutrients such as Vit D).