Muscle Loss Is Prevalent and Severe in the ICU: An Analysis of Clinically Acquired CT Images

Background Muscle loss is a common and debilitating complication of critical illness. Understanding the prevalence, severity, and risk factors associated with muscle loss is challenging. Muscle cross‐sectional area obtained from computed tomography (CT) scans can be used to assess changes in muscle over the course of critical illness. The objective of this study was to investigate changes in muscle in the ICU using clinically acquired CT imaging, describe the severity and prevalence of muscle loss in the ICU, and explore the risk factors for muscle loss in the ICU. Methods For this multi‐hospital cohort study, we acquired baseline and follow‐up CT abdominal scans for 171 ICU trauma and sepsis patients from four hospitals in Calgary, Canada. We measured mean psoas muscle cross‐sectional area at the level of the third lumbar vertebra using a U‐Net algorithm and manual correction. Patient demographic and illness‐related information were acquired using electronic medical records. Linear mixed models and regressions were used to assess risk factors. Results CT‐derived psoas muscle index (PMI, defined as psoas cross‐sectional area/height 2 ), was calculated for 151 patients. The median [IQR] age was 55 [42, 67] years and 40% of patients were female. 71% of patients had sepsis and 29% had traumatic injuries. Patients experienced a median [IQR] 9 [1.5, 18.3]% reduction in psoas muscle index (PMI) over a median [IQR] 13 [9, 21] days in the ICU. This represents a median PMI loss rate of 0.9% [0.2, 1.6] % per day. The prevalence of substantial PMI loss (≥ 10%) was 45%. Patients with greater PMI at baseline or greater time in the ICU experienced more profound PMI loss ( p < 0.001). Trauma patients experienced a greater rate of PMI loss than sepsis patients ( p < 0.05). Female sepsis patients had the lowest PMI at follow‐up (p < 0.001). 89% of patients survived the ICU. Greater rate of PMI loss was associated with increased ICU mortality ( p < 0.05). Conclusions Muscle loss in trauma and sepsis patients in the ICU is common, especially among patients with longer ICU stays or greater baseline muscle. Greater rate of muscle loss occurs in trauma patients and is associated with mortality.