Intensive care unit–acquired weakness: unanswered questions and targets for future research

Abstract

Intensive care unit–acquired weakness (ICU-AW) is the most common neuromuscular impairment in critically ill patients. We discuss critical aspects of ICU-AW that have not been completely defined or that are still under discussion. Critical illness polyneuropathy, myopathy, and muscle atrophy contribute in various proportions to ICU-AW. Diagnosis of ICU-AW is clinical and is based on Medical Research Council sum score and handgrip dynamometry for limb weakness and recognition of a patient’s ventilator dependency or difficult weaning from artificial ventilation for diaphragmatic weakness (DW). ICU-AW can be caused by a critical illness polyneuropathy, a critical illness myopathy, or muscle disuse atrophy, alone or in combination. Its diagnosis requires both clinical assessment of muscle strength and complete electrophysiological evaluation of peripheral nerves and muscles. The peroneal nerve test (PENT) is a quick simplified electrophysiological test with high sensitivity and good specificity that can be used instead of complete electrophysiological evaluation as a screening test in non-cooperative patients. DW, assessed by bilateral phrenic nerve magnetic stimulation or diaphragm ultrasound, can be an isolated event without concurrent limb muscle involvement. Therefore, it remains uncertain whether DW and limb weakness are different manifestations of the same syndrome or are two distinct entities. Delirium is often associated with ICU-AW but a clear correlation between these two entities requires further studies. Artificial nutrition may have an impact on ICU-AW, but no study has assessed the impact of nutrition on ICU-AW as the primary outcome. Early mobilization improves activity limitation at hospital discharge if it is started early in the ICU, but beneficial long-term effects are not established. Determinants of ICU-AW can be many and can interact with each other. Therefore, future studies assessing early mobilization should consider a holistic patient approach with consideration of all components that may lead to muscle weakness.

Role of ICU-acquired weakness on extubation outcome among patients at high risk of reintubation

“…However, MRC sumscore was measured only for the elbows and knees with an overall score ranging from 0 to 20 points, and limb weakness was considered for a score below 10 points. Unlike this study, we measured MRC sum-score according to the usual method with an overall sum-score ranging from 0 to [21,[35][36][37], while severe limb weakness was considered in patients with a MRC sum-score below 36 points [36], these scores having shown a good interobserver agreement. Moreover, cough strength was not assessed in these previous studies and could have been a confounding factor making the results uncertain.…”

“…Ineffective cough is mainly due to altered expiratory muscle function including at varying degrees of the diaphragm, accessory respiratory muscles, and abdominal muscles [18,19]. ICU-acquired weakness combining polyneuropathy, myopathy, and muscle atrophy [20][21][22] is clinically diagnosed as limb paresis but may affect all respiratory muscles with an altered inspiratory and expiratory strength, as well pharyngeal muscles, and which can lead to overall respiratory muscle weakness [23,24] and to swallowing disorders [25].…”

Approach to critical illness myopathy and polyneuropathy in the older SARS-CoV-2 patients

“…One last theory suggests CIP is related to dysfunction of voltage gated sodium channels [29]. This shared mechanism with CIM may underlie why both conditions often occur together.…”

Reliability, Validity, and Cutoff Point of the Chinese Version of the Chelsea Critical Care Physical Assessment Tool in Critically Ill Patients

“…Intensive care unit-acquired weakness (ICU-AW) is a severe and debilitating complication in critically ill patients. The prevalence of ICU-AW in patients receiving mechanical ventilation for more than 4-7 days has been reported to be 33-82% [1][2][3][4][5] . The prevalence of ICU-AW in sepsis patients is 100% [3][4][5] .…”

“…The prevalence of ICU-AW in sepsis patients is 100% [3][4][5] . Early identi cation, assessment and active prevention are crucial to reduce ICU-AW risk because the pathophysiological mechanism of ICU-AW is not clear, and e cacious pharmacotherapy is lacking [1,6] .…”