Critical Illness Survivorship: Rehabilitation and Recovery

© 2021 Jennifer Rose Abotomey JonesSurvivors of critical illness can experience significant physical disability during their recovery, delaying return to activities of daily living, all negatively impacting their health-related quality of life. Level one evidence supports the implementation of physical rehabilitation programs to address these short term sequalae. However, recent large randomized controlled trials measuring longer term physical function and health-related quality of life do not report sustained improvement. To better understand this phenomenon, investigations into the role of patient characteristics in responsiveness to physical rehabilitation and critical illness recovery is an emerging research area and is the focus of this thesis. The first study of this thesis is a narrative review, where 12 randomized controlled trials with conflicting results for the beneficial effects of physical rehabilitation on the physical function, health-related quality of life and health care utilization outcomes of critically ill adults were identified from a comprehensive and systematic literature search. Through critical evaluation of these randomized controlled trials and additionally relevant studies, a theoretical construct was developed for the research of this thesis and to advance the field. In brief, the core components of the theoretical construct are in searching for the responder; investigation into potential modifiers of physical rehabilitation outcomes (including patient characteristics); tailoring rehabilitation interventions to address known physical impairments; and deciphering the prime time for responsiveness to these interventions based on patients biological and physiological recovery. Lastly, the conclusion that more research is needed on the optimal prescription parameters of physical rehabilitation programs to guide clinical practice with consideration to facilitators and barriers to implementation of the intervention is reached. The second study is a systematic review examining the association between indicators of social and economic position within society (socioeconomic position) and health outcomes following critical illness. Ten studies were included in this systematic review, with a strong focus on mortality despite survivorship being the identified challenge for critical care in the 21st century. The higher mortality rates and poorer health-related quality of life reported for critically ill adults with a lower socioeconomic position signal that a social gradient exists in critical care. This may indicate a clinical subgroup that would derive benefit from multimodal and interdisciplinary interventions to potentially alter their recovery trajectory. For the third and final study a systematic review and an individual participant data meta-analysis of randomized controlled trials was performed to examine the interaction between the treatment group (intervention vs control) and patient characteristics (comorbidity, age, sex and illness severity) for the performance-based physical function (at hospital discharge, three and six months) and health-related quality of life (at three, six and 12 months) outcomes of critically ill adults. From the four randomized controlled trials included, totaling a combined sample size of over 800 participants, comorbidity modified the effect of physical rehabilitation for the health-related quality of life instrument (Physical Component Summary score of the 12-item and 36-item Short Form Health Surveys). Specifically, the Physical Component Summary scores were higher (better) for multimorbid patients (defined as Functional Comorbidity Index score >=2) who were allocated to the intervention group at the three and six but not 12 month follow up time points. We hypothesize that this study has implications for future trial design, where a stratified approach (Functional Comorbidity Index =2) may reduce sample size calculations. We recommend that clinicians prioritize the provision of a structured individualized physical rehabilitation program to multimorbid patients as a subgroup that derives significant benefit from this intervention. In conclusion, the findings of this thesis navigate the path forward for rehabilitation research in critical care. This area, both in research and clinical practice, has previously been plagued by the heterogeneity of the patient population. The identification of a target group of critically ill patients (multimorbid, Functional Comorbidity Index score >= 2) provides direction clinically and for future investigations into the effects of physical rehabilitation. Ultimately leading to the progression of the field to provide patients with the right intervention at the right time in their recovery trajectory to improve their outcomes following critical illness