Intensive Care Unit Acquired Weakness as a Modifiable Organ Dysfunction? A Narrative Review of Evolving Diagnostic and Therapeutic Concepts

Intensive Care Unit Acquired Weakness (ICUAW) is a highly prevalent neuromuscular complication affecting around 40% of critically ill patients, rising to over 80% in high-risk cohorts. It is independently associated with prolonged mechanical ventilation, increased intensive care unit (ICU) and hospital length of stay, elevated mortality (in-hospital, 1-year, and 5-year), higher healthcare costs, and long-term functional impairment. ICUAW is clinically defined by symmetric flaccid tetraparesis, frequently involving respiratory muscles, and exhibits significant pathobiological heterogeneity. Further subclassification is based on neurotopographic patterns: Critical Illness Polyneuropathy (CIP), Myopathy (CIM), and Polyneuromyopathy (CIPNM). Diagnosis typically relies on the Medical Research Council (MRC) Sum Score, with a threshold of <48 indicating clinically relevant weakness. While adjunct modalities such as electromyography/nerve conduction studies support assessment, their utility may be limited by patient cooperation and availability. Preventive strategies center on modifiable metabolic factors. Caloric and protein deficits exacerbate catabolism, while overfeeding-linked to anabolic resistance and stress hyperglycemia-also impairs recovery. To date, pharmacologic interventions remain inconclusive. However, early mobilization and neuromuscular electrical stimulation are promising non-pharmacologic strategies. The multifactorial and heterogeneous pathophysiology of ICUAW highlights the need for a biologically refined definition that can guide future targeted therapeutic interventions. Comprehensive multimodal strategies, together with structured long-term follow-up in Post-Intensive Care Syndrome (PICS) clinics, are essential for improving outcomes in this prevalent complication of critical care.