Intensive care unit-acquired weakness of mechanically ventilated patients: prevalence and risk factors

Abstract

To observe the incidence of intensive care unit-acquired weakness (ICU-AW) of mechanically ventilated patients, and to identify the relevant risk factors. A prospective cohort study was conducted. The patients admitted to intensive care unit (ICU) of Fuxing Hospital, Capital Medical University, aged 18 years old or older, with the duration of mechanical ventilation ≥ 24 hours and expected to stay in ICU for ≥ 7 days from May 2015 to January 2016 were enrolled. From the 7th day after ICU admission, the patients were evaluated for consciousness every day. If the patient was awake and could cooperate with muscle strength measurement, the day was recorded as T1, and the patient's muscle strength was measured using the Medical Research Council scale (MRC) and recorded, then all patients were divided into two groups according to MRC score, ICU-AW group (MRC score < 48) and non-ICU-AW group (MRC score ≥ 48). The death, transfer or the 28th day of ICU admission were regarded as the end of observation. The data from the first day of ICU admission to T1 (before T1), including metabolic factors (the lowest value of blood sodium, blood potassium, blood calcium, albumin, and the highest value of blood glucose), mechanical ventilation factors (mode and duration of mechanical ventilation), organ dysfunction factors [occurrence and duration of sepsis, multiple organ dysfunction syndrome (MODS)], and drug factors (whether the patients used aminoglycoside, sedative, muscle relaxant or glucocorticoids, etc., the time of these drugs usage and the cumulative dose) of the patients were observed, recorded and analyzed, as well as the data from T1 to the end of the observation period, including the duration of mechanical ventilation, incidence of ventilator associated pneumonia (VAP), 28-day mortality, the length of ICU stay, and the cost of ICU and hospitalization. The relevant factors with statistical significance in univariate analysis were enrolled in multivariate analysis, and Logistic regression equation was established to screen the independent risk factors that might lead to ICU-AW. 486 patients with mechanical ventilation were enrolled in this study, and 37 patients were enrolled according to the inclusion and exclusion criteria, including 15 patients with ICU-AW (with ICU-AW incidence of 40.5%) and 22 patients without ICU-AW. In the univariate analysis, ICU-AW group patients showed statistical differences in following factors as compared with the non-ICU-AW group: age, and the duration of invasive ventilation and the total duration of mechanical ventilation, braking time, sepsis, MODS and duration of them, the usage days and dosage of sedative and glucocorticoid before T1. The total duration of mechanical ventilation from T1 to the end of the observation period, total duration of mechanical ventilation during the observation period, and length of ICU stay of the ICU-AW group were significantly longer than those of the non-ICU-AW group [hours: 190 (110, 274) vs. 4 (0, 57), hours: 337 (237, 477) vs. 78 (43, 170), days: 20±7 vs. 14±7, all P < 0.05], the incidence of VAP, 28-day mortality and total hospitalization expenses were significantly higher than those of the non-ICU-AW group [26.7% (4/15) vs. 0% (0/22), 53.3% (8/15) vs. 9.1% (2/22), 10 thousands Yuan: 18.7±7.7 vs. 12.1±10.8, all P < 0.05]. Multivariate Logistic regression analysis showed that the total duration of mechanical ventilation between the patient awake and ICU admission [odds ratio (OR) = 1.03, 95% confidence interval (95%CI) was 1.01-1.05, P = 0.011] and the duration of MODS (OR = 1.79, 95%CI was 1.17-2.72, P = 0.007) were the independent risk factors for ICU-AW in mechanically ventilated patients. ICU-AW is quite common in patients with mechanical ventilation and has a higher incidence. The risk factors associated with ICU-AW were the total duration of mechanical ventilation and duration of MODS.