Creatinine excretion as a determinant of accelerated skeletal muscle loss with critical illness

Abstract

Objective: The 24-h urinary creatinine excretion rate has been used as an approximation of the skeletal muscle (SM) mass in non-in-tensive care unit (ICU) settings. The study goal or aim was to determine reductions in SM mass in patients with recurrent critical illness who are admitted to a medical ICU. Methods: Retrospective ICU patient records between 2013 and 2015 were reviewed. Inclusion of ICU patients with repeat 24-h urinary creatinine excretion levels at two different ICU admissions done routinely as part of care. The study design is a case series with patients as their own control. Results: Three patients were found to have data on two separate ICU admissions. The reduction in creatinine excretion among ICU patients was correlated with estimated SM mass. All patients had >50% reduction in creatinine excretion and ≥47% reduction in estimated SM mass over 4 months. All patients were bed-bound after the first ICU admission and met the definition of sarcopenia by the second ICU admission; all patients died during the second ICU admission. The final SM mass in all patients was <4 kg m-2. Conclusion: Patients with chronic critical illness admitted to the medical ICU, who become bed bound, can experience up to 50% reduction in SM mass as gleaned from creatinine excretion within 4 months. Low SM mass may predispose patients to increased mortality. Measurement of 24-h urinary creatinine excretion may be a useful ICU biomarker to determine SM mass for diagnostic and prognostic purposes.