ICU-acquired weakness: Critical illness myopathy and polyneuropathy

Abstract

Critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) are significant complications in intensive care unit (ICU) patients, first identified in the late 20th century. These conditions often present as flaccid paralysis and respiratory muscle weakness, making it challenging for patients to wean off ventilatory support. The incidence of ICU-acquired weakness, which includes CIM and CIP, ranges from 25 % to 84 % among long-term ventilated patients, with higher rates observed in those with sepsis or systemic inflammatory response syndrome. CIM is characterized by muscle wasting and can be confirmed using electromyography and muscle biopsy. The pathogenesis of CIM involves the loss of thick myosin filaments, while the proposed etiology of CIP centers around increased permeability of nerve axons, leading to axonal degeneration. Risk factors for developing these conditions include prolonged ICU length of stay, sepsis, multi-system organ dysfunction, hyperglycemia, as well as exposure to steroids and neuromuscular blocking agents. Emerging diagnostic tools including muscle ultrasound, magnetic resonance imaging (MRI), and biomarkers such as interleukin-6 (IL-6) and growth differentiation factor-15 (GDF-15) show promise in early detection and differentiation of CIM and CIP. Preventative and therapeutic treatment focuses on early mobilization, minimizing sedation, optimizing nutritional support, and use of intensive insulin therapy to prevent prolonged hyperglycemia. Despite these advancements, CIM and CIP continue to pose significant challenges, emphasizing the need for ongoing research to improve patient outcomes and develop effective treatments.

Keywords: Critical illness myopathy; Critical illness polyneuropathy; ICU-acquired weakness.