BACKGROUND: Intensive care unit-acquired weakness (ICU-AW) is a complication characterized by decreased muscle mass and impairments in strength and physical function and is associated with poor quality of life and worse clinical outcomes. The primary objective of this study is to analyze the prevalence of ICU-AW, and secondary objectives were to assess risk factors and analyze the associations with clinical outcomes. METHODS: This is a prospective cohort study of patients on mechanical ventilation (MV). Nutritional risk (mNUTRIC) and the presence of malnutrition (GLIM criteria) were evaluated. A nutritional assessment was performed upon admission and post-extubation. Cumulative energy and protein deficit (CPD) were calculated. ICU-AW was assessed. Post-extubation dysphagia (P-ED), hospital readmission, length of ICU stays post-extubation, and hospital stay post-ICU were reported as clinical outcomes. Comparison tests between groups, univariate and multivariate logistic, and linear regressions were performed. RESULTS: ICU-AW was diagnosed in 55 % of patients. Differences were observed between ICU-AW and normal strength group for sex, days on MV, hospital length of stay, pharmacological therapy for sedation and CPD. The interaction of vecuronium prescription with MV time (RR = 1.09, 95%CI = 1.03-1.16, p <
0.01) and female sex (RR = 4.16, 95%CI = 1.3-13.38, p = 0.01) were independent predictors for ICU-AW development. ICU-AW was associated with P-ED (RR = 11.2, 95%CI = 2.6-48.4, p <
0.01) and length of ICU stay post-extubation (β = 2.11, 95%CI = 0.5-3.7, p = 0.01). CONCLUSION: ICU-AW is a highly frequent condition in critical patients. Pharmacological therapy, duration of MV and sex were independent predictors for ICU-AW development. This condition was also associated with P-ED development and length of ICU stay post-extubation.