Trajectories of Recovery after ACutE and cRitical illness (TRACER): a prospective observational study protocol

Patients who survive admission to intensive care unit (ICU) for critical illness are at high risk of developing muscle atrophy and weakness, commonly diagnosed as ICU-acquired weakness (ICUAW). The development of ICUAW is closely linked to long-term symptoms and impairments known as post-intensive care syndrome (PICS). Despite heightened recognition of impairments, there is limited research supporting effective interventions to improve muscle and physical outcomes after hospital discharge. Prior to developing and testing interventions for ICU survivors, it is imperative to understand the trajectory of muscle and physical function recovery following an ICU stay. The purpose of this study is to longitudinally investigate skeletal muscle health and physical function outcomes after ICU admission.

This protocol describes a single site, prospective, observational study in adult patients who have survived a critical illness (ie, sepsis or acute respiratory failure). Patients will participate in a battery of testing including primary outcomes: muscle power and physical function; and secondary outcomes: muscle strength, muscle size, endurance and physical activity (by accelerometry) at hospital discharge and 3, 6, and 12 months post-discharge. A subset of patients will participate in muscle biopsy and venipuncture. To examine if the trajectory of recovery predicts primary outcomes, we will perform multivariate linear regression models in 150 evaluable patients. To examine differences in molecular and cellular outcomes in plasma and muscle tissue, a control group of community-dwelling adults without history of an ICU stay will be enrolled as a comparator group. Enrolment started on 18 October 2022 with an estimated completion date of 1 August 2027.

This protocol was approved by the University of Kentucky Office of Research Integrity Medical Internal Review Board (# 77407), with patients providing informed written consent. We anticipate our findings to establish recovery trajectories, improving the classification of patients who experience sustained physical disability. Improved identification of recovery trajectories of muscle and physical function enables future studies to employ an individually targeted rehabilitation approach, that is, precision medicine, with the goal of improving patient outcomes. The cellular findings will support the development of novel interventions specifically designed for detecting underlying mechanisms. We intend to disseminate findings to patients, healthcare professionals, the public and other relevant groups via conference presentations and manuscripts without publication restrictions.

NCT05537298.