Delirium in the ICU and subsequent long-term disability among survivors of mechanical ventilation

Abstract

Objective: Survivors of critical illness are frequently left with long-lasting disability. The association between delirium and disability in critically ill patients has not been described. We hypothesized that the duration of delirium in the ICU would be associated with subsequent disability and worse physical health status following a critical illness.

Design: Prospective cohort study nested within a randomized controlled trial of a paired sedation and ventilator weaning strategy.

Setting: A single-center tertiary-care hospital.

Patients: One hundred twenty-six survivors of a critical illness.

Measurements and main results: Confusion Assessment Method for the ICU, Katz activities of daily living, Functional Activities Questionnaire (measuring instrumental activities of daily living), Medical Outcomes Study 36-item Short Form General Health Survey Physical Components Score, and Awareness Questionnaire were used. Associations between delirium duration and outcomes were determined via proportional odds logistic regression with generalized estimating equations (for Katz activities of daily living and Functional Activities Questionnaire scores) or via generalized least squares regression (for Medical Outcomes Study 36-item Short Form General Health Survey Physical Components Score and Awareness Questionnaire scores). Excluding patients who died prior to follow-up but including those who withdrew or were lost to follow-up, we assessed 80 of 99 patients (81%) at 3 months and 63 of 87 patients (72%) at 12 months. After adjusting for covariates, delirium duration was associated with worse activities of daily living scores (p = 0.002) over the course of the 12-month study period but was not associated with worse instrumental activities of daily living scores (p = 0.15) or worse Medical Outcomes Study 36-item Short Form General Health Survey Physical Components Score (p = 0.58). Duration of delirium was also associated with lower Awareness Questionnaire Motor/Sensory Factors scores (p 0.02).

Conclusion: In the setting of critical illness, longer delirium duration is independently associated with increased odds of disability in activities of daily living and worse motor-sensory function in the following year. These data point to a need for further study into the determinants of functional outcomes in ICU survivors.

Figure 1

Enrollment and follow-up diagram. ^a Katz ADL: Activities of daily living, ^b FAQ: Functional Activities Questionnaire (measuring instrumental activities of daily living), ^c SF-36 Medical Outcomes Study 36-item Short Form General Health Survey Physical Components Score, ^d AQ: Awareness Questionnaire.

Figure 2

Panel A. Association between duration of delirium in the ICU and probability of a higher Katz ADL score (indicating disability) over the course of the year following hospitalization for critical illness, after adjusting for age, baseline ADL function, severity of illness at admission, sepsis at admission, and duration of coma. As the number of days of ICU delirium increases, so does the probability of developing worse ADL function (p=0.002). Dashed lines indicate 95% confidence intervals. Panel B. Association between duration of delirium in the ICU and score on the Motor/Sensory Factor of the Awareness Questionnaire over the course of the year following hospitalization for critical illness, after adjusting for age, severity of illness at admission, sepsis at admission, and duration of coma. As the number of days of ICU delirium increased, the Awareness Questionnaire Motor/Sensory Factors score decreased (p=0.02), indicating greater perceived impairment in limb movement, eyesight, coordination and hearing compared with pre-illness state. Possible scores on this measure range from 4–20, with lower scores indicating worse perceived functioning compared to pre-illness functioning. Dashed lines represent 95% confidence intervals.