[Risk factors and diagnostic methods of intensive care unit-acquired weakness]

To explore the risk factors of intensive care unit-acquired weakness (ICU-AW) and the characteristics of Medical Research Council (MRC) score and electromyogram.

A case control study was conducted. Patients with mechanical ventilation ≥ 7 days and MRC score admitted to department of respiratory and critical care medicine of China-Japan Friendship Hospital from September 2018 to January 2020 were enrolled, and they were divided into ICU-AW group (MRC score < 48) and non-ICU-AW group (MRC score ≥ 48) according to MRC score. The general situation, past medical history, related risk factors, MRC score, respiratory support mode, laboratory examination results, electromyogram examination results, ICU-AW related treatment, outcome and length of ICU stay were collected, and the differences between the two groups were compared. The risk factors of ICU-AW were analyzed by binary multivariate Logistic regression, and the characteristics of MRC score and electromyogram were analyzed.

A total of 60 patients were enrolled in the analysis, including 17 patients in ICU-AW group and 43 patients in non-ICU-AW group. Univariate analysis showed that there were significant differences in acute physiology and chronic health evaluation II (APACHE II) score, sequential organ failure assessment (SOFA) score, brain natriuretic peptide (BNP), blood urea nitrogen (BUN) on the first day of ICU admission and the ratio of invasive mechanical ventilation between ICU-AW group and non-ICU-AW group [APACHE II score: 21 (18, 25) vs. 18 (15, 22), SOFA score: 7 (5, 12) vs. 5 (3, 8), BNP (ng/L): 364.3 (210.1, 551.2) vs. 160.1 (66.8, 357.8), BUN (mmol/L): 9.9 (6.2, 17.0) vs. 6.0 (4.8, 9.8), invasive mechanical ventilation ratio: 88.2% vs. 46.5%, all P < 0.05]. Binary multivariate Logistic regression analysis showed no independent risk factor for ICU-AW. The average MRC score of 17 ICU-AW patients was 33±11. The limb weakness was symmetrical, and the proximal limb weakness was the main manifestation. Electromyography examination showed that the results of nerve conduction examination in ICU-AW patients mainly revealed that the amplitude of compound muscle action potential (CMAP) and sensory nerve action potentials (SNAP) were decreased, and the conduction velocity was slowed down; needle electromyography showed increased area of motor unit potential (MUP), prolonged time limit and a large number of spontaneous potentials. Prognosis evaluation showed that compared with non-ICU-AW group, patients in ICU-AW group underwent more tracheotomy (70.6% vs. 11.6%), longer length of ICU stay (days: 57±52 vs. 16±8), and more rehabilitation treatment (58.8% vs. 14.0%), and the differences were statistically significant (all P < 0.01).

The occurrence of ICU-AW may be related to high APACHE II score and SOFA score, high levels of BNP and BUN on the first day of ICU admission and the proportion of invasive mechanical ventilation, but the above factors are not independent risk factors for ICU-AW. The MRC score of ICU-AW patients was characterized by symmetrical limb weakness, mainly proximal limb weakness; in electromyography examination, the nerve conduction examination results mainly showed that CMAP and SNAP amplitude were decreased, and conduction velocity was slowed down; needle electromyography examination showed increased MUP area, prolonged duration and a large number of spontaneous potentials.