Sarcopenia in critical patients – relationship between mortality, nutrition and functional activity: Single-center prospective observational cohort study

Abstract

Sarcopenia is a disease characterized by loss of both muscle mass and muscle function and is very common in patients in the intensive care unit (ICU). The aim was to investigate the relationship between sarcopenia and mortality, nutrition, weakness and functional activity in intensive care patients. This prospective cohort study included patients who underwent ultrasonographic quadriceps muscle thickness measurement 48 hours after admission to the anesthesia ICU. Patients who underwent ultrasonographic quadriceps muscle thickness measurement in the anesthesia ICU were included in the study. Correlation analysis was performed with sarcopenia parameters and clinical conditions (acute physiology and chronic health evaluation [APACHE] II and sequential organ failure assessment [SOFA]), malnutrition (nutritional risk screening 2002 [NRS2002] and nutrition risk in critically ill score [NUTRIC]), frailty (simple questionnaire to rapidly diagnose sarcopenia [SARC-F]), and life activities scales. Fifty-one patients were included in the study. A negative correlation was found between rectus femoris (RF) muscle thickness and Charlson comorbidity index, NUTRIC, NRS2022 and frailty index scores, a negative correlation with SARC-F score, a positive correlation with KATZ score and a positive correlation with Lawron–Brody score (P < .05). A negative correlation was found between vastus intermedius (VI) muscle thickness and NRS2002 and SARC-F scores, and a positive correlation was found with KATZ score (P < .05). Ultrasonographic measurement of quadriceps muscle thickness in intensive care patients is a useful evaluation method in patient follow-up in terms of nutritional defect, frailty, daily living activities, and mortality.

1. Introduction

Critically ill patients experience rapid skeletal muscle loss due to physiological stress and increased catabolism during their stay in the intensive care unit (ICU). This leads to prolonged ICU stay, respiratory muscle weakness, delayed weaning from ventilation, and many morbidities such as limitations in daily living activities.^[1] The prevalence of ICU-associated sarcopenia varies between 25% and 100%.^[2] This situation significantly affects patient follow-up and rehabilitation. Sarcopenia is a geriatric syndrome defined by the loss of both muscle mass and muscle function. In 2016, the World Health Organization accepted sarcopenia as a disease with the code ICD-10-CM (M62.84).^[3] For the diagnostic criteria of sarcopenia, patients with decreased muscle mass must also have at least one of the following: loss of muscle strength and/or deterioration in muscle performance.^[4]

Ultrasonography (USG) is a reliable and valid tool for measuring muscle thickness and for early detection and follow-up of sarcopenia. At the same time, USG does not expose the patient to radiation and is quite useful in intensive care patients at the bedside due to its mobility.^[5] In the evaluation of sarcopenia, USG of the thigh rectus femoris (RF) muscle is particularly useful due to the superficial and easily accessible location of the muscle. Minetto et al determined the cutoff value for sarcopenia as a decrease in RF muscle thickness of 20 mm in men and 16 mm in women.^[6] Sonographic muscle thickness ratio and cutoff values for sarcopenia diagnosis were recently defined by Kara et al. The cutoff values for the sonographic thigh correction ratio (STAR), obtained by dividing the anterior thigh muscle thickness (mm) by the body mass index (BMI), were found to be 1.4 and 1.0 in male and female subjects, respectively.^[7,8]

The main objective of the study was to investigate whether the assessment of sarcopenia in the ICU would help identify patients at high risk of death: to determine the prevalence of sarcopenia in ICU patients; to determine the relationship between sarcopenia and nutritional deficits and functional outcomes in ICU patients; and to define the relationship between sarcopenia and 30-day mortality.

2. Methods

2.1. Search strategy

This prospective observational cohort study consists of patients who were hospitalized in the anesthesia and re-examination ICU of Şanliurfa Education and Research Hospital between January 2023 and April 2023 and underwent ultrasonographic anterior thigh muscle thickness measurements at least 48 hours after admission. Ultrasonographic measurements were made by both observers (HA, NA) within 48 hours after ICU admission.

2.1.1. Ethics statement

Written informed consent was obtained from each patient or their legal representative before participation and information was provided about the study protocol. Ethics Committee of Harran University Hospital approved the study (Decision numbered December 12, 2022 and 2022/24/35).

2.2. Inclusion criteria

1. Patients aged 18 years and over who have been admitted to the ICU

2. Patients who have been admitted to the ICU for at least 48 hours

3. Patients without existing systemic neuromuscular disease

4. Patients who are expected to stay in the ICU for more than 96 hours

5. Patients whose RF, vastus intermedius (VI), and subcutaneous thickness were measured by USG 48 hours after admission to the ICU

2.3. Exclusion criteria

1. Patients who cannot independently perform basic activities of daily living (ADL), such as walking with assistance, before admission to the ICU

2. Patients with disabilities in the USG measurement area

3. Patients with preexisting systemic neuromuscular disease

4. Patients with autoimmune disorders affecting the musculoskeletal system

5. Patients with lower extremity fractures and amputations

6. Patients whose RF and VI muscle lines cannot be well defined on USG due to soft tissue edema

2.4. Study protocol

2.4.1. Clinical evaluation

Patients’ demographic characteristics such as age, gender, BMI, underlying diseases, length of stay (number of days in hospital and intensive care), and feeding method (closed, oral enteral, parenteral) were recorded. Critical disease data regarding the reason for admission to the ICU, acute physiology and chronic health evaluation (APACHE) II score during ICU admission, and sequential organ failure assessment (SOFA) score during the ICU stay were recorded. We followed the patients for 30 days. We divided the patients into 2 groups: survivors and 30-day mortality. Nutritional status in the ICU was assessed with nutritional risk screening 2002 (NRS2002) and nutrition risk in critically ill score (NUTRIC) scales. Functional status and dependency levels were assessed by the relatives of the patients using Katz daily living activities (ADL) and Lawton Instrumental ADL scales, taking into account their pre-hospitalization status. The simple questionnaire to rapidly diagnose sarcopenia (SARC-F) was used as a sarcopenia screening test, and the FRAIL frailty test was used as a frailty screening test.

2.4.2. Ultrasound muscle measurement

Patients were positioned with their legs extended and their muscles relaxed. The point representing half of the distance from the anterior superior iliac spine to the upper border of the patella was determined. RF, VI and anterior mid-thigh muscle thickness measurements in the dominant extremity were recorded using a 5 to 12 MHz linear probe ultrasound (Vscan®Dual Probe). A large volume of gel was used to minimize the pressure on the tissue. All measurements were made on the screen of the ultrasound unit located at the bedside. Patients whose RF muscle lines could not be well defined due to soft tissue edema were excluded from the study (n = 3). RF muscle thickness was measured between the deep and superficial fascia; VI muscle thickness was measured between the femoral cortex and the superficial fascia of VI (Fig. 1). The anterior thigh muscle thickness was measured in the axial plane between the periosteum of the femur and the outer fascial layer of RF. Then, the (mm) was divided by BMI to calculate sonographic thigh adjustment ratio (STAR).^[7] ISarcoPRM algorithm was used for the diagnosis of sarcopenia.^[8] To assess measurement consistency, 2 independent physicians (HA, NA) performed muscle thickness measurements same day. Interobserver reliability was evaluated using the intraclass correlation coefficient (ICC), which demonstrated high agreement across all measured parameters (ICC > 0.85). Both physicians had prior training in musculoskeletal USG and at least 10 years of clinical experience, allowing accurate and reliable assessments.

Figure 1.

Ultrasonographic image of anterior thigh muscles. a: Rectus femoris, b: vastus intermedius, c: anterior mid-thigh muscle thickness, and d: subcutaneous fat thickness.

2.5. Statistical analysis

Statistical analyses were performed using SPSS version 25.0 (Statistical Package for Social Sciences, IBM, Armonk). Continuous variables with normal distribution were presented as mean ± standard deviation; those without normal distribution were presented as median and interquartile range (IQR: 25–75 percentiles). Categorical variables are shown as numbers and percentages. To analyze the mean difference, continuous variables were compared using independent samples t-test or Mann–Whitney U-test, respectively, according to whether they were normally distributed or not. Categorical variables were analyzed using Pearson chi-square and Fisher exact probability tests according to the expected frequency for differences between groups. Spearman correlation analysis was applied to examine the correlation between the scores or indices of clinical severity, nutrition and daily living activities scales and RF and VI muscle thickness. Binary logistic regression analysis was performed with forward: LR method to determine variables associated with mortality. In this study, a P value <.05 was considered statistically significant.

3. Results

The demographic and some clinical characteristics of the patients are shown in Table 1. A total of 51 patients, 26 (51%) female and 25 (49%) female, were included in the study. The mean age of the patients was 65.3 ± 16.3 years. The most common comorbidities were hypertension (HT) 58% and diabetes mellitus 25.5%. The most common admission diagnosis was respiratory system diseases 49% and cerebrovascular accident (CVA) 27.5%. The average hospital stay was 25 days, and the average intensive care stay was 14 days.

Table 1.

Demographic characteristics, comorbid diseases and hospitalization diagnoses of the patients (n = 51).

Age (mean ± standard deviation)	65.3 ± 16.3
Gender (n/%)
Female	26 (51.0)
Male	25 (49.0)
VKİ (mean ± standard deviation)	25.9 ± 7.0
Smoking (n/%)	28 (53.8)
Comorbidities (n/%)
HT	30 (58.8)
DM	13 (25.5)
CAD	13 (25.5)
CHF	7 (13.7)
AF	5 (9.8)
COPD	27 (52.9)
CRF	3 (5.9)
CVA	17 (33.3)
Dementia	7 (13.7)
Malignancy	2 (3.9)
Other	3 (5.9)
Number of comorbidities (n/%)
None	5 (9.8)
1	17 (33.3)
2	11 (21.6)
3	12 (23.5)
4	6 (11.8)
Admission diagnosis (n/%)
Respiratory system diseases	25 (49.0)
Neurological diseases	14 (27.5)
Sepsis	4 (7.8)
Gastrointestinal diseases	2 (3.9)
Cardiovascular diseases	2 (3.9)
Trauma and orthopedic diseases	3 (5.9)
Other	1 (2.0)

AF = atrial fibrillation, CAD = coronary artery disease, CHF = congestive heart failure, COPD = chronic obstructive pulmonary disease, CRF = chronic renal failure, CVA = cerebrovascular accident, DM = diabetes mellitus, HT = hypertension.

The patients were followed up for 30 days. They were divided into 2 groups as patients who survived and 30-day mortality, and their clinical features and laboratory parameters are shown in Table 2. The 30-day mortality rate was 15.68% (8 patients). The 2 groups were found to be similar in terms of age (P = .542), gender and BMI (P = .509). No significant difference was found between the groups in terms of respiratory support, steroid status, sepsis, vasoactive agent use, daily protein and calorie intake (P > .05). When nutritional status was divided into 2 groups as those fed orally and those fed by other routes/oral intake closed, it was found to be similar between the groups (P = .210). The proportion of female patients was found to be 58.1% (25/51) in the survived group and 12.5% (1/8) in 30-day mortality group, and the proportion of male patients was found to be significantly higher in the 30-day mortality group (Pearson chi-square: P = .018). Glucose and procalcitonin values were found to be higher in the death group (P = .035), and other laboratory parameters were found to be similar between the groups (P > .05). SOFA, APACHE II, Charlson comorbidity index and NUTRIC, NRS2002 scores were found to be higher in 30-day mortality group (P < .05). Frailty index, SARC-F, Katz daily living activities (ADL) and Lawton instrumental ADL scale were found to be similar between the groups (P > .05). According to RF, VI muscle thickness, anterior thigh muscle thickness and STAR calculation, sarcopenia frequency was found to be similar for the groups (P > .05). Sarcopenia cutoff values were taken into account (RF muscle thickness below 16 mm and below 20 mm for men and cutoff values for STAR were 1.0 and 1.4). Sarcopenia was detected in 90.9% of patients in the survival group and in 94.4% in the 30-day mortality group. The mean RF muscle thickness was 11.9 ± 4.3, VI muscle thickness was 8.2 ± 3.8, and anterior thigh muscle thickness was 19.2 ± 11.7 mm.

Table 2.

Comparison of clinical characteristics and laboratory parameters of survived and 30-d mortality group (n = 51).

	Survived (n = 43)	30-d mortality (n = 8)	P
Median (IQR) or mean ± SD
Length of hospital stay (d)	25.0 (44.0)	16.3 ± 9.1	.031*
Length of stay in intensive care (d)	14.0 (45.0)	16.3 ± 9.1	.516*
Respiratory support (n/%)
Spontaneous	16 (37.2)	2 (25.0)
NIMV	11 (25.6)	1 (12.5)	.402†
IMV	16 (37.2)	5 (62.5)
Steroid use (n/%)
Yes	40 (93.0)	7 (87.5)	.594†
No	3 (7.0)	1 (12.5)
Sepsis during hospitalization (n/%)
Yes	36 (86.7)	–	.219†
No	7 (16.3)	8 (100.0)
Vasoactive agent during hospitalization (n/%)
Yes	22 (51.2)	7 (87.5)	.057†
No	21 (48.8)	1 (12.5)
Renal replacement therapy (n/%)
Yes	3 (7.0)	2 (25.0)	.115†
No	40 (93.0)	6 (75.0)
Nutritional status (n/%)
Oral	15 (34.9)	1 (12.5)
Enteral	21 (48.8)	4 (50.0)	.210†,‡
Parenteral	4 (9.3)	3 (37.5)
Closed	3 (7.0)	–
Daily protein (g/kg)	0.8 (0.7)	0.89 ± 0.42	.656*
Daily calories (kg)	19.1 ± 8.9	19.0 ± 6.5	.876*
Physiotherapy program (n/%)
Yes	3 (7.0)	–	.534†
No	40 (97.0)	8 (100.0)
RF muscle thickness (mm)	11.9 ± 5.3	11.3 ± 3.9	.672§
VI muscle thickness (mm)	9.2 ± 4.8	7.6 (6.7)	.813*
Anterior thigh muscle thickness (mm)	18.0 ± 10.1	19.2 ± 11.7	.698§
Anterior thigh muscle thickness and subcutaneous fat thickness (mm)	30.4 ± 11.3	26.8 ± 10.0	.257§
Sarcopenia (RF muscle thickness) (n/%)	30 (90.9)	17 (94.4)	.654*
Glucose	103.0 (53.0)	137.5 (50.5)	.024*
Albumin	29.7 ± 5.9	27.9 ± 6.7	.379*
Creatinine	0.9 (0.6)	1.1 ± 0.8	.265*
Urea	46.0 (43.0)	71.5 ± 57.2	.602*
CRP	61.0 (117.0)	128.4 ± 91.1	.146*
Procalcitonin	0.19 (0.36)	1.2 (5.2)	.035*

CRP = C-reactive protein, IMV = invasive mechanical ventilation, IQR = interquartile range, NIMV = noninvasive mechanical ventilation, RF = rectus femoris, VI = vastus intermedius.

^*Mann–Whitney U test.

^†Pearson Chi-square test.

^‡P value obtained when nutritional status is grouped as those fed orally and those fed by other routes/oral intake is not available.

^§Independent samples t test.

The patients were divided into 2 groups as geriatric and non-geriatric (age limit 65) and their clinical features are presented in Table 3. The 30-day mortality rates, hospitalization and ICU stay were similar between the 2 groups (P > .05). RF muscle thickness was found to be less in the geriatric age group than in the non-geriatric group (P < .01), and total muscle thickness (RF + VI) was found to be similar (P > .05). APACHE II and CCI scores were found to be significantly higher in the geriatric age group (P < .01, P < .001).

Table 3.

Nutritional and clinical severity scoring results of survived and 30-d mortality group (n = 51).

	Survived (n = 43)	30-d mortality (n = 8)	P
SOFA	5.0 (2.0)	9.0 ± 4.1	<.01*
APACHE II	25.7 ± 7.8	31.8 ± 4.8	.025*
Charlson comorbidity index	5.0 (2.0)	6.5 (2.0)	<.001*
NUTRİC	5.0 (1.0)	5.9 ± 1.1	.012*
NRS2002	3.0 (1.0)	3.0 (0.0)	.029*
Frailty index	2.0 (3.0)	1.5 (3.0)	.694*
SARC-F	4.0 (5.0)	3.5 (6.0)	.929*
Katz daily living scale	6.0 (3.0)	6.0 (3.0)	.809*
Lawron–Brody scale	4.0 (4.0)	3.9 ± 2.4	.909*

NRS2002 = nutritional risk screening 2002, NUTRİC = nutrition risk in critically ill, SARC-F = sarcopenia screening form, SOFA = sequential organ failure assessment.

^*Mann—Whitney U test.

Correlation analysis was performed between RF and VI muscle thickness and clinical scoring scales (Table 4). There was a negative correlation between RF muscle thickness and Charlson comorbidity index, NUTRİC, NRS2022 and frailty index scores, a negative correlation with SARC-F score, a positive correlation with KATZ score and a positive correlation with Lawron–Brody score (P < .05). There was a negative correlation between VI muscle thickness and NRS2002 and SARC-F scores, and a positive correlation with KATZ score (P < .05).

Table 4.

Comparison of clinical data of geriatric and non-geriatric patients (n = 51).

	Geriatric group (n = 30)	Non-geriatric group (n = 21)	P
Median (IQR) or mean ± standard deviation
30-d mortality (n/%)	6 (20.0)	2 (9.5)	.311*
Length of hospital stay (d)	18.0 (42.5)	30.0 (35.5)	.168†
Length of stay in intensive care (d)	12.5 (38.3)	21.0 (42.5)	.133†
Respiratory support (n/%)
Spontaneous	14 (46.7)	4 (19.0)	.052*
NIMV	4 (13.3)	8 (38.1)
IMV	12 (40.0)	9 (42.9)
Steroid use (n/%)
Yes	28 (93.3)	19 (90.5)	.709*
No	2 (6.7)	2 (9.5)
Sepsis during hospitalization (n/%)
Yes	25 (83.3)	19 (90.5)	.466*
No	5 (16.7)	2 (9.5)
Vasoactive agent during hospitalization (n/%)
Yes	19 (63.3)	10 (47.6)	.389‡
No	11 (36.7)	11 (52.4)
Renal replacement therapy (n/%)
Yes	1 (3.3)	4 (19.0)	.063*
No	29 (96.7)	17 (91.0)
Nutritional status (n/%)
Oral	8 (26.7)	8 (38.1)
Enteral	15 (50.0)	10 (47.6)	.786*
Parenteral	5 (16.7)	2 (9.5)
Closed	2 (6.7)	1 (4.8)
Daily protein (g/kg)	0.97 ± 0.6	0.8 (1.0)	.969†
Daily calories (kg)	19.3 ± 8.6	18.8 ± 8.6
Physiotherapy program (n/%)
Yes	-	2 (9.5)	.085*
No	30 (100.0)	19 (90.5)
RF muscle thickness (mm)	10.2 ± 4.2	13.8 ± 4.9	<.01§
VI muscle thickness (mm)	8.5 (5.3)	9.3 ± 3.5	.977†
Anterior thigh muscle thickness (mm)	20.1 ± 8.3	22.7 ± 7.5	.271§
Anterior thigh muscle thickness and subcutaneous fat thickness (mm)	28.1 ± 11.1	30.7 ± 10.7	.403§
Sarcopenia (RF muscle thickness) (n/%)	29 (96.7)	18 (85.7)	.152*
Sarcopenia (STAR) (n/%)	27 (90.0)	19 (90.5)	.955*
SOFA	4.0 (3.0)	6.0 (4.0)	.785†
APACHE II	29.1 ± 7.8	23.2 ± 6.1	<.01§
Charlson comorbidity index	5.5 (1.0)	3.8 ± 1.5	<.001†
Glucose	131.0 (59.3)	121.0 (55.0)	.559†
Albumin	28.6 ± 6.4	30.6 ± 5.2	.236§
Creatinine	0.6 (0.7)	0.6 (0.6)	.759†
Urea	47.5 (59.8)	46.0 (48.0)	.625†
CRP	81.5 (131.8)	62.0 (107.1)	.193†
Procalcitonin	0.24 (0.93)	0.19 (2.49)	.985†
Procalcitonin	0.24 (0.93)	0.19 (2.49)	.985†

CRP = C-reactive protein, IQR = interquartile range, SOFA = sequential organ failure assessment.

^*Pearson Chi-square test.

^†Mann–Whitney U test.

^‡Fisher exact test.

^§Independent samples t test.

In the binary logistic regression analysis performed for predictive variables for 30-day mortality, age, gender, BMI, smoking, number of comorbidities, respiratory support, steroid and vasoactive agent use, presence of sepsis, duration of hospital stay, duration of ICU stay, RF and VI muscle thickness, albumin, glucose, creatinine, C-reactive protein (CRP), PCT, SOFA, APACHE II, Charlson comorbidity index, NUTRİC; NRS2002 and SARC-F scores were included in the model. The risk of 30-day mortality increased as the duration of ICU stay (OR: 1.025, P = .039) and APACHE II score (OR: 0.882, P = .010) increased. However, as the Charlson comorbidity index (OR: 4.068, P = .039) and frailty index (OR: 0.127, P = .032) increase, the risk of 30-day mortality increases, and no other predictive variable was found for 30-day mortality (P > .05).

A high level of agreement was found between the 2 observers for all ultrasonographic muscle thickness measurements. The ICC for the RF muscle was 0.89 (95% CI: 0.83–0.94), for the VI muscle was 0.87 (95% CI: 0.80–0.92), and for the total anterior thigh muscle thickness was 0.91 (95% CI: 0.86–0.95), indicating excellent interobserver reliability.

4. Discussion

Our study is important in terms of the bedside evaluation of quadriceps muscle thickness with USG in intensive care patients and its correlation with mortality, nutrition, frailty, and life scores. Quadriceps thickness, which is especially important in the lower extremity of intensive care patients, can guide us in terms of the general condition and prognosis of patients. Our study shows that more focus should be placed on sarcopenia screening in intensive care patients and that early and effective preventive programs such as nutrition and exercise treatments should be recommended in terms of prognosis, nutrition, frailty, and quality of life of patients.

In a systematic review and meta-analysis examining the relationship between sarcopenia and mortality in critically ill patients, 3249 patients underwent quadriceps muscle CT scans^[9]; the prevalence of sarcopenia was found to be 41% in critically ill patients. The meta-analysis report stated that critically ill patients with sarcopenia had a higher risk of mortality compared to critically ill patients without sarcopenia. There are also studies indicating that the prevalence of sarcopenia in ICUs is approximately 30 to 70%.^[10] Sarcopenia prevalence has been shown to be as high as 60% among hospitalized patients requiring mechanical ventilation.^[11] We think that these differences may be due to sarcopenia assessment methods and different cutoff values. In our study, when ultrasonographic sarcopenia cutoff values were taken into account (RF thickness and STAR), sarcopenia was detected in 94.4% of the patients in the ICU.

Studies suggest that the presence of sarcopenia in intensive care patients can guide us in terms of mortality and prognosis.^[12] So far, some scoring systems have been used to evaluate critically ill patients,^[13] and it has been shown that their mortality prediction performance is weak.^[9] Therefore, more studies are needed to investigate more sensitive parameters to better predict poor clinical outcomes. In our study, patients with thick anterior thigh muscles were found to have fewer nutritional defects and lower risk of frailty. At the same time, patients with thick anterior thigh muscles had increased independence in daily living activities and quality of life. These results also show us that evaluating sarcopenia in terms of nutrition, frailty and independence in daily living activities in intensive care patients and using it in the follow-up of patients may be guiding.

There is no gold standard assessment method for the diagnosis of sarcopenia in intensive care patients. It is difficult to assess muscle strength and physical performance in these patients.^[14] Anthropometric measurements do not measure sarcopenia accurately in critically ill patients due to subcutaneous edema, physical performance tests do not measure sarcopenia accurately due to problems with cooperation and consciousness, and bioimpedance tests do not measure sarcopenia accurately in critically ill patients due to electrolyte abnormalities.^[15] Therefore, in our study, we evaluated sarcopenia by measuring anterior thigh muscle thickness with USG. We believe that muscle imaging with US, which is a method that can be used especially at the bedside, is mobile, user-dependent, and does not contain radiation for the patient, is especially important in intensive care patients. A reliability and validity study of quadriceps muscle thickness with ultrasound has been conducted in intensive care patients; evaluation of quadriceps muscle thickness with USG shows good interobserver reliability.^[16,17]

In our study, sarcopenia was found to be directly related to mortality and prognosis scales in ICU patients, but it was not found to be a direct predictor of 30-day mortality. Although there are studies similar to our results,^[10,18,19] one study found that the only independent predictive factor for 60-day mortality was quadriceps muscle thickness on the 7th day after ICU admission.^[20] Studies with larger numbers of patients and patients with similar diagnostic groups are needed on this subject. Evaluating sarcopenia in similar diagnostic groups to eliminate admission diagnoses that will affect mortality may be guiding in subsequent studies.

Inadequate protein intake is an important cause of muscle loss in ICU patients. In a study evaluating critically ill patients, 0.8 g/kg/day and 1.2 g/kg/day amino acid intake provided by parenteral nutrition were compared. The higher amino acid intake was associated with a significant increase in forearm muscle thickness assessed by ultrasound.^[21] A 12.5% loss in RF muscle cross-sectional area was reported in ICU patients 7 days after admission; this loss was attributed to increased protein turnover and an imbalance between muscle protein synthesis and protein degradation.^[22] Similarly, in our study, there was a significant relationship between anterior thigh muscle thickness and nutritional deficiency. As anterior thigh muscle thickness increased, patients’ nutritional parameters were more favorable. However, in another study evaluating the effect of calorie and protein deficiency on muscle loss in ICU patients, no correlation was found between calorie and protein deficiency and the decrease in quadriceps muscle mass during the first week in the ICU.^[23] Therefore, a future study on the relationship between sarcopenia and daily protein and calorie intake would be appropriate.

In our study, it was found that RF and VI muscle thickness was thinner, malnutrition was more common, frailty increased and 30-day mortality increased in the geriatric age group. Similarly, in a study in which ultrasound measurements of quadriceps and VI muscle thickness were performed in geriatric patients in intensive care, it was determined that frailty increased, malnutrition was more common and mortality increased in geriatric patients with decreased muscle thickness.^[24] In a meta-analysis examining ultrasonographic lower extremity muscles in geriatric patients, 37 studies were examined and RF and VI muscles were mostly used in sarcopenia studies.^[16]

Exercise is the most proven effective treatment for sarcopenia. There is controversy over which type of exercise is most effective. One systematic review recommended resistance-based strengthening exercises as a first-line treatment for managing sarcopenia.^[4] On the other hand, another review reported that aerobic exercise was the most effective exercise for improving muscle strength and physical performance. Vitamin D deficiency has been commonly associated with sarcopenia, low grip strength, and atrophy of skeletal muscle mass. A large-scale (n = 380) study found that vitamin D taken in conjunction with oral leucine supplementation improved muscle mass and lower extremity function in individuals with sarcopenia, even in the absence of physical activity.^[25]

5. Limitations of the study

This study consists of critically ill patients with different admission diagnoses in a single center and an anesthesia ICU. In order to obtain a healthy predictive factor for mortality, a larger number of patients with similar diagnosis groups should be included in a multicenter study. Other factors that will affect mortality should be eliminated. A more comprehensive analysis should be performed considering potential confounding variables such as medications, ICU management, and comorbidities. In subsequent studies, studies should be conducted to examine the changes in muscle thickness after admission and its correlation with clinical parameters. Changes in physical therapy and nutritional recommendations to prevent sarcopenia and 90-day mortality rates should be recorded.

6. Conclusion

The evaluation of sarcopenia in intensive care patients is very important in terms of prognosis and mortality. Evaluating muscle functions in intensive care is difficult due to the immobility of the patients and difficulty in cooperation. Ultrasonographic quadriceps muscle thickness measurement should be used more frequently in clinical practice, especially because it is user-dependent, easily performed at the bedside, and a reproducible, noninvasive radiation-free method. Sarcopenia, although detected in the majority of patients, was not an independent predictor of 30-day mortality. However, muscle thickness was found to have significant associations with nutrition, frailty, and quality of life. In particular, the significant relationship between quadriceps muscle thickness and comorbidity indices and nutritional defects in our study guides us to conduct future studies in a larger population. Since exercise is the only proven treatment for sarcopenia, physical therapy and rehabilitation programs are extremely important in immobile patients.

Author contributions

Conceptualization: Hatice Ağir, Nazire Ateş.

Data curation: Hatice Ağir, Nazire Ateş.

Formal analysis: Hatice Ağir.

Funding acquisition: Hatice Ağir.

Investigation: Hatice Ağir.

Methodology: Hatice Ağir.

Project administration: Hatice Ağir.

Resources: Hatice Ağir.

Software: Hatice Ağir.

Supervision: Hatice Ağir, Nazire Ateş.

Validation: Hatice Ağir.

Visualization: Hatice Ağir, Nazire Ateş.

Writing – original draft: Hatice Ağir.

Writing – review & editing: Hatice Ağir.