Intensive care unit-acquired weakness

Abstract

Intensive care unit acquired weakness (ICU-AW) is a clinical diagnosis characterised by generalised weakness of the limbs and respiratory muscles subsequent to prolonged intensive care. The weakness develops in the intensive care unit and is without another obvious cause. ICU-AW is because of critical illness polyneuropathy or critical illness myopathy or a combination of these two, termed critical illness poly-neuromyopathy. Previously used terms such as steroid denervation myopathy, sepsis-induced myopathy and ventilator-induced diaphragmatic dysfunction have all been abandoned in preference of ICU-AW.

The risk factors for developing ICU-AW are numerous, including patient demographics, premorbid status, drug use in ICU and severity of the disease. The pathophysiology is initiated by an inflammatory response leading to microvascular, muscle and nerve dysfunction or a combination of these factors. The clinical gold standard is the Medical Research Council sum score (MRC-SS) of less than 48 points out of a maximum 60 points. Other modalities used for confirming diagnosis include electromyography, nerve conduction studies and imaging such as ultrasound and magnetic resonance imaging. Nerve and muscle biopsies are rarely performed to confirm the cause of ICU-AW. An integral part in the management of ICU-AW includes limiting or avoiding risk factors, aggressively treating the underlying illness, glycaemic control and early physical rehabilitation. ICU-AW contributes significantly to the development of chronic critical illness and post-intensive care syndrome which affects quality of life of ICU survivors.