Evaluating Muscle Mass by Using Markers of Kidney Function: Development of the Sarcopenia Index.
OBJECTIVE
Sarcopenia is associated with a poor prognosis in the ICU. The purpose of this study was to describe a simple sarcopenia index using routinely available renal biomarkers and evaluate its association with muscle mass and patient outcomes.


METHODS
A retrospective cohort study.


METHODS
A tertiary-care medical center.


METHODS
High-risk adult ICU patients from October 2008 to December 2010.


METHODS
The gold standard for muscle mass was quantified with the paraspinal muscle surface area at the L4 vertebrae in the subset of individuals with an abdominal CT scan. Using Pearson's correlation coefficient, serum creatinine-to-serum cystatin C ratio was found to be the best performer in the estimation of muscle mass. The relationship between sarcopenia index and hospital and 90-day mortality, and the length of mechanical ventilation was evaluated.


RESULTS
Out of 226 enrolled patients, 123 (54%) were female, and 198 (87%) were white. Median (interquartile range) age, body mass index, and body surface area were 68 (57-77) years, 28 (24-34) kg/m, and 1.9 (1.7-2.2) m, respectively. The mean (± SD) Acute Physiology and Chronic Health Evaluation III was 70 (± 22). ICU, hospital, and 90-day mortality rates were 5%, 12%, and 20%, respectively. The correlation (r) between sarcopenia index and muscle mass was 0.62 and coefficient of determination (r) was 0.27 (p < 0.0001). After adjustment for Acute Physiology and Chronic Health Evaluation III, body surface area, and age, sarcopenia index was independently predictive of both hospital (p = 0.001) and 90-day mortality (p < 0.0001). Among the 131 patients on mechanical ventilator, the duration of mechanical ventilation was significantly lower on those with higher sarcopenia index (-1 d for each 10 unit of sarcopenia index [95% CI, -1.4 to -0.2; p = 0.006]).


CONCLUSIONS
The sarcopenia index is a fair measure for muscle mass estimation among ICU patients and can modestly predict hospital and 90-day mortality among patients who do not have acute kidney injury at the time of measurement.
1Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic, Rochester, MN. 2Division of Pulmonary and Critical Care Medicine, Department of Medicine, Mayo Clinic, Rochester, MN. 3Department of Pharmacy, Mayo Clinic, Rochester, MN. 4Charles University in Prague, Faculty of Medicine in Hradec Kralove, Czech Republic, Europe. 5Department of Anesthesiology, Mayo Clinic, Rochester, MN. 6Department of Radiology, Mayo Clinic, Rochester, MN. 7Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
Kianoush B
KB
Kashani
Erin N
EN
Frazee
Lucie
L
Kukrálová
Kumar
K
Sarvottam
Vitaly
V
Herasevich
Phillip M
PM
Young
Rahul
R
Kashyap
John C
JC
Lieske
D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging; D012121:Respiration, Artificial / Q000706:statistics & numerical data; D012189:Retrospective Studies; D055948:Sarcopenia / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed
D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine