Abstract
BackgroundMuscle quantity at intensive care unit (ICU) admission has been independently associated with mortality. In addition to quantity, muscle quality may be important for survival. Muscle quality is influenced by fatty infiltration or myosteatosis, which can be assessed on computed tomography (CT) scans by analysing skeletal muscle density (SMD) and the amount of intermuscular adipose tissue (IMAT). We investigated whether CT-derived low skeletal muscle quality at ICU admission is independently associated with 6-month mortality and other clinical outcomes.MethodsThis retrospective study included 491 mechanically ventilated critically ill adult patients with a CT scan of the abdomen made 1 day before to 4 days after ICU admission. Cox regression analysis was used to determine the association between SMD or IMAT and 6-month mortality, with adjustments for Acute Physiological, Age, and Chronic Health Evaluation (APACHE) II score, body mass index (BMI), and skeletal muscle area. Logistic and linear regression analyses were used for other clinical outcomes.ResultsMean APACHE II score was 24 ± 8 and 6-month mortality was 35.6%. Non-survivors had a lower SMD (25.1 vs. 31.4 Hounsfield Units (HU); p < 0.001), and more IMAT (17.1 vs. 13.3 cm2; p = 0.004). Higher SMD was associated with a lower 6-month mortality (hazard ratio (HR) per 10 HU, 0.640; 95% confidence interval (CI), 0.552–0.742; p < 0.001), and also after correction for APACHE II score, BMI, and skeletal muscle area (HR, 0.774; 95% CI, 0.643–0.931; p = 0.006). Higher IMAT was not significantly associated with higher 6-month mortality after adjustment for confounders. A 10 HU increase in SMD was associated with a 14% shorter hospital length of stay.ConclusionsLow skeletal muscle quality at ICU admission, as assessed by CT-derived skeletal muscle density, is independently associated with higher 6-month mortality in mechanically ventilated patients. Thus, muscle quality as well as muscle quantity are prognostic factors in the ICU.Trial registrationRetrospectively registered (initial release on 06/23/2016) at ClinicalTrials.gov: NCT02817646.
Highlights
Muscle quantity at intensive care unit (ICU) admission has been independently associated with mortality
Neither SMD nor intermuscular adipose tissue (IMAT) were significantly associated with the odds of being discharged to home, length of ventilation (LOV), or ICU length of stay (ICU-LOS). This retrospective study in mechanically ventilated patients admitted to the ICU for 4 days or longer shows that low skeletal muscle quality at ICU admission, as assessed by skeletal muscle density on computed tomography (CT) scans, is associated with higher 6-month mortality independent of muscle quantity, Acute Physiological (APACHE) II score, and body mass index (BMI)
Intermuscular adipose tissue was associated with mortality but not independently, suggesting that SMD is a stronger marker of muscle quality for 6-month mortality or that IMAT is better represented by confounders than SMD
Summary
Muscle quantity at intensive care unit (ICU) admission has been independently associated with mortality. Puthucheary et al reported a steady decrease in skeletal muscle mass of almost 20% during the first 10 days of intensive care unit (ICU) admission [2]. Loss of muscle has been associated with longer duration of mechanical ventilation and higher ICU and hospital mortality [3,4,5]. If patients survive, they exhibit long-term functional disability with a great impact on quality of life for as long as 5 to 8 years after admission [6,7,8]. In two retrospective studies as much as 60–70% of patients had low muscle quantity as assessed on computed tomography (CT) scans on ICU admission, and low muscle quantity at ICU admission was associated with a higher mortality [9, 10]
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