Risk factors for intensive-care-unit-acquired weakness

Abstract

Wang et al reported 1063 cases from the initial 14 d of intensive care unit (ICU) stay, and analyzed relevant data such as age, comorbidities, recent dosages, vapor pressure dosages, duration of mechanical ventilation, length of ICU stay, and rehabilitation therapy, which are closely related to ICU-acquired weakness (ICU-AW). It is suggested that the length of ICU stay and the duration of mechanical ventilation are the main factors. ICU-AW is the most common neuromuscular injury in the ICU, which affects clinical progression and outcomes of patients. This manuscript helps to improve the early recognition of ICU-AW, thereby reducing mortality and improving prognosis.

Key Words: Risk factors, Intensive care unit, Acquired weakness, Prognosis, Neuromuscular injury

Core Tip: The manuscript is helpful to improve the diagnosis and treatment of intensive-care-unit-acquired weakness (ICU-AW). ICU-AW is the most common neuromuscular injury that affects the clinical progression and outcomes of ICU patients. Multiple mechanisms are involved in the occurrence and development of ICU-AW; however, the relationship between these mechanisms still needs to be elucidated in order to reduce mortality and improve prognosis.

TO THE EDITOR

Wang et al[1] reported 1063 cases from the initial 14 d of intensive care unit (ICU) stay, and analyzed relevant data such as age, comorbidities, recent dosages, vapor pressure dosages, duration of mechanical ventilation, length of ICU stay, and rehabilitation therapy. They suggested that the duration of mechanical ventilation is important. ICU-AW is a common neuromuscular injury in the ICU, which affects clinical progression and outcomes of patients. This manuscript helps to improve the early recognize of ICU-AW, thereby reducing mortality and improving prognosis.

Weakness is a prominent and common problem in the ICU. Weakness caused by primary neuromuscular diseases (such as acute infectious multiple radiculitis, myasthenia gravis, amyotrophic lateral sclerosis, or multiple sclerosis) accounts for < 0.5% of all ICU patients, while AW is more common. The clinical syndrome that occurs during severe illness and cannot be explained by reasons other than severe illness, characterized by symmetrical weakness of the limbs and limbs, is called ICU-AW[2]. It is estimated that > 1 million patients worldwide experience ICU-AW each year. The prognosis of ICU-AW is poor, and in severe cases, respiratory muscle paralysis may occur, which can lead to prolonged mechanical ventilation and hospital stay. However, it was ignored in the manuscript that ICU-AW and prolonged mechanical ventilation and hospital stay can interact each other. The etiology of ICU-AW is complex and diverse, and identifying risk factors is important for early diagnosis. As far as the risk factors are concerned in the manuscript, it was not comprehensive, and some more important factors were not considered, such as sepsis, nutritional status, long-term immobilization, microcirculation disorders, and bioenergy failure.

Sepsis, mechanical ventilation, nutritional status, and long-term immobilization are important causes of ICU-AW[3-5]. Sepsis can lead to severe loss of skeletal muscle proteins, muscle atrophy and weakness, as well as dysfunction of the diaphragm and skeletal muscles, and is important for the occurrence of ICU-AW. The incidence of multiple organ dysfunction can reach up to 100%. Imbalance of protein synthesis and degradation, energy consumption, metabolic disorders, and other factors during malnutrition can lead to cell death and muscle atrophy, and promoting the occurrence of ICU-AW. Even with sufficient nutritional support, the prognosis will be affected by the nutritional mode. Braking can quickly lead to muscle atrophy and decreased muscle strength. Although braking itself is not sufficient to explain muscle weakness in critically ill patients, it is a contributing factor. Even healthy individuals begin to experience muscle degeneration after 4 h of braking, with an average daily loss of total muscle strength of 1.0%–1.3%.

During critical illness, changes in muscle structure, microcirculation disorders, bioenergy failure, and changes in membrane ion channel function can lead to muscle dysfunction, causing ICU-AW[2,5,6]. A large amount of myosin is lost, the myosin/actin ratio decreases, and muscle filaments are severely damaged during critical illness, leading to a decrease in muscle strength. These structural changes in muscle are one of the causes of muscle dysfunction. The activation of endothelial cells, microvascular leakage, and changes in microvascular environment can affect perfusion and oxygen transfer. Hypoperfusion and hypoxia can lead to hyperkalemia and accumulation of acidic substances, causing neuronal damage and axonal degeneration, causing ICU-AW. Mitochondrial dysfunction is the most important source of oxygen free radical production, and this oxidative stress acts through positive feedback, exacerbating mitochondrial dysfunction. The reduction of ATP production leads to energy failure, making muscles prone to fatigue. The ion channels related to the occurrence of ICU-AW mainly include voltage-dependent sodium channels and calcium channels. Abnormalities in both channels can lead to a decrease in muscle membrane excitability and excitation contraction coupling disorders, promoting the occurrence of ICU-AW.

CONCLUSION

The manuscript is helpful for improving the diagnosis and treatment of ICU-AW patients. ICU-AW is the most common neuromuscular injury that affects clinical progression and outcomes of ICU patients. Multiple mechanisms are involved in the occurrence and development of ICU-AW; however, the relationship between these mechanisms still needs to be elucidated in order to reduce mortality and improve prognosis.