Impact of ICU-acquired weakness on post-ICU physical functioning: a follow-up study

Abstract

Introduction: ICU-acquired weakness is thought to mediate physical impairments in survivors of critical illness, but few studies have investigated this thoroughly. The purpose was to investigate differences in post-ICU mortality and physical functioning between patients with and without ICU-acquired weakness at 6 months after ICU discharge.

Method: ICU patients, mechanically ventilated ≥ 2 days, were included in a single-center prospective observational cohort study. ICU-acquired weakness was diagnosed when the average Medical Research Council score was <4 in awake and attentive patients. Post-ICU mortality was recorded until 6 months after ICU discharge; in surviving patients, physical functioning was assessed using the Short-Form Health Survey physical functioning domain. The independent effect of ICU-acquired weakness on post-ICU mortality was analyzed using a multivariable Cox proportional hazards model. The independent effect of ICU-acquired weakness on the physical functioning domain score was analyzed using a multivariable linear regression model.

Results: Of the 156 patients included, 80 had ICU-acquired weakness. Twenty-three patients died in the ICU (20 with ICU-acquired weakness); during 6 months follow-up after ICU discharge another 25 patients died (17 with ICU-acquired weakness). Physical functioning domain scores were available for 96 survivors (39 patients with ICU-acquired weakness). ICU-acquired weakness was independently associated with an increase in post-ICU mortality (hazard ratio 3.6, 95% confidence interval, 1.3 to 9.8; P = 0.01) and with a decrease in physical functioning (β: -16.7 points; 95% confidence interval, -30.2 to -3.1; P = 0.02).

Conclusion: ICU-acquired weakness is independently associated with higher post-ICU mortality and with clinically relevant lower physical functioning in survivors at 6 months after ICU discharge.

Figure 1

Flowchart of the study population. ICU-AW, ICU-acquired weakness; OHCA, out-of-hospital cardiac arrest; MRC, muscle strength as assessed with Medical Research Council scale; mRankin, modified Rankin score; NMD, neuromuscular disorder.

Figure 2

Post-ICU survival curves for patients with and without ICU-acquired weakness. Survival curves for patients with (black line) and without (grey line) intensive care unit-acquired weakness (ICU-AW) starting at final ICU discharge until end of follow-up; that is, 6 months after final ICU discharge. Dotted lines represent the 95% confidence interval; censored patients presented with +.