Skeletal Muscle Wasting and Renal Dysfunction After Critical Illness Trauma - Outcomes Study

Inclusion Criteria: * Major trauma cohort: Patients ≥18y admitted to ICU and anticipated to be mechanically ventilated for ≥48 hours with a primary admission diagnosis of major trauma. * Non-trauma cohort: Patients ≥18y admitted to ICU and anticipated to be mechanically ventilated for ≥48 hours without a primary admission diagnosis of major trauma. Exclusion Criteria: * Death or discharge from hospital considered highly likely by treating physician within 7 days of ICU admission. * Any of the following conditions: major traumatic brain injury (Abbreviated Injury Scale head injury score ≥ 5), spinal cord injury with paralysis, lower limb amputation, end stage renal disease or disseminated cancer, lack of independence with activities of daily living or non-ambulatory status prior to admission. (Rationale - exclusion of factors where type of injury or comorbid disease will overwhelming determine functional or renal outcomes.)