Associations Between Muscle-Related Cytokines and Selected Patient Outcomes in the ICU

Abstract

Introduction: Systemic cytokines produced by contracting skeletal muscles may affect the onset and severity of intensive care unit (ICU)-acquired weakness after critical illness. Aims: The purpose of this research was to determine the serum levels of interleukin (IL)-8, IL-15, and tumor necrosis factor-α (TNF-α) among patients receiving mechanical ventilation for >48 hr and examine the relationships of these myokines to outcomes of patient delirium, muscle strength, activities of daily living (ADLs), duration of mechanical ventilation, and length of ICU stay. Methods: In this exploratory, repeated-measures interventional study, the 36 participants received 20 min of once-daily in-bed or out-of-bed activity using an established early progressive mobility protocol after physiologic stability had been demonstrated for >4 hr in the ICU. Blood samples were drawn on 3 consecutive days, beginning on the day of study enrollment, for serum cytokine quantification. Results: IL-8, IL-15, and TNF-α were highly variable and consistently elevated in participants compared to normal healthy adults. About 1/3 of participants were positive for significant muscle weakness at discharge from ICU. Repeated values of mean postactivity IL-8 serum values were significantly associated only with ADL following ICU discharge. There were no significant associations with repeated values of mean postactivity IL-15 or TNF-α serum values and outcomes. Conclusion: Results provide preliminary data for exploring the potential effects of elevated serum values IL-8 and IL-15 in muscle health and TNF-α for muscle damage, including effect sizes to calculate the sample sizes needed for future studies.