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, 20 (1), 386

Skeletal Muscle Quality as Assessed by CT-derived Skeletal Muscle Density Is Associated With 6-month Mortality in Mechanically Ventilated Critically Ill Patients

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Skeletal Muscle Quality as Assessed by CT-derived Skeletal Muscle Density Is Associated With 6-month Mortality in Mechanically Ventilated Critically Ill Patients

Wilhelmus G P M Looijaard et al. Crit Care.

Abstract

Background: Muscle 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.

Methods: This 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.

Results: Mean 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.

Conclusions: Low 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 registration: Retrospectively registered (initial release on 06/23/2016) at ClinicalTrials.gov: NCT02817646 .

Keywords: CT; Computed tomography; Intensive care unit; Intermuscular adipose tissue; Mortality; Muscle; Muscle quality; Myosteatosis; Outcome; Skeletal muscle density.

Figures

Fig. 1
Fig. 1
Example of CT scan analysis. This image shows CT scans at the level of lumbar vertebra 3 of two patients both un-analysed (upper row) and analysed (lower row). The analysed images show muscle tissue (red) and intermuscular adipose tissue (IMAT, green). The patient on the left has more muscle (165 vs. 120 cm2), less IMAT (10 vs. 19.5 cm2), and higher mean skeletal muscle density (42 vs. 18 Hounsfield Units) than the patient on the right
Fig. 2
Fig. 2
Consort diagram showing the inclusion process. CT computed tomography, ICU intensive care unit
Fig. 3
Fig. 3
Kaplan-Meier plots. These graphs illustrate mortality for groups below and above median skeletal muscle density (SMD) (29.2 Hounsfield Units) and median intermuscular adipose tissue (IMAT) (13.6 cm2). ICU intensive care unit

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