ICU-Acquired Weakness: An Unsolved Clinical Problem: A Narrative Review

Intensive care unit-acquired weakness (ICUAW) is a common and devastating complication in critically ill patients admitted to the intensive care unit (ICU). ICUAW is characterized by profound skeletal and respiratory muscle weakness and degeneration, as well as peripheral nerve dysfunction. The condition is further categorized into three primary diagnoses: critical illness myopathy (CIM), which affects skeletal muscles, critical illness polyneuropathy (CIP), which affects peripheral nerves, and critical illness polyneuromyopathy (CIPNM), which exhibits features of both CIM and CIP. Although the pathophysiology of ICUAW remains poorly understood, several risk factors have been identified, including female sex, advanced age, prolonged mechanical ventilation, extended ICU stay, prolonged immobilization, multiorgan failure, shock, infection, and other factors related to critical illness and its treatment. Currently, ICUAW is diagnosed after the onset of critical illness, and only once all other possible causes of generalized weakness have been excluded. The most commonly used assessments for suspected ICUAW are the Medical Research Council sum score (MRC-SS) and handgrip dynamometry. However, these tools require active patient participation and are, therefore, impractical for many ICU patients. Non-volitional testing methods, including electromyography (EMG) and nerve conduction studies, can be used to evaluate ICUAW, but these tests are invasive and require specialized training and resources. Due to the lack of effective diagnostic tools and an incomplete understanding of disease mechanisms, management of ICUAW is largely restricted to physical rehabilitation. ICUAW is associated with high morbidity and mortality, and survivors often experience long-term disability and reduced quality of life following hospital discharge. Future areas of research, including biomarker analysis and risk prediction modeling, may enable earlier diagnosis and intervention in critically ill patients. This review summarizes potential diagnostic tools, current management strategies, and short- and long-term prognosis and identifies emerging areas of research aimed at improving outcomes for critically ill patients with suspected ICUAW.