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Objective To test the hypothesis that duration of delirium in the intensive care unit (ICU) is an independent predictor of long-term cognitive impairment after critical illness requiring mechanical ventilation. Design Prospective cohort study. Setting Medical ICU in a large community hospital in the United States. Patients Mechanically ventilated medical ICU patients who were assessed daily for delirium while in the ICU and underwent comprehensive cognitive assessments 3 and 12 months after discharge. Measurements and Main Results Of 126 eligible patients, 99 survived ≥3 months post-critical illness; long-term cognitive outcomes were obtained for 77 (78%) patients. Median age was 61 years, 51% were admitted with sepsis/ARDS, and median duration of delirium was 2 days. At 3-and 12-month follow-up, 79% and 71% of survivors had cognitive impairment, respectively (with 62% and 36% being severely impaired). After adjusting for age, education, preexisting cognitive function, severity of illness, severe sepsis, and exposure to sedative medications in the ICU, increasing duration of delirium was an independent predictor of worse cognitive performance—determined by averaging age- and education-adjusted T-scores from nine tests measuring seven domains of cognition—at 3-month (p = 0.02) and 12-month follow-up (p = 0.03). Duration of mechanical ventilation, alternatively, was not associated with long-term cognitive impairment (p = 0.20 and 0.58). Conclusions In this study of mechanically ventilated medical ICU patients, duration of delirium was independently associated with long-term cognitive outcomes, representing a potentially modifiable predictor of this common public health problem.

Background Delirium or acute brain dysfunction is extremely prevalent in medical intensive care unit (ICU) patients, but limited data exist regarding its prevalence and risk factors among surgical (SICU) and trauma ICU (TICU) patients. The purpose of this study was to determine the prevalence and risk factors for delirium in surgical and trauma ICU patients. Methods SICU and TICU patients requiring mechanical ventilation (MV) >24 hours were prospectively evaluated for delirium using the Richmond Agitation Sedation Scale (RASS) and the Confusion Assessment Method for the ICU (CAM-ICU). Those with baseline dementia, intracranial injury, or ischemic/hemorrhagic strokes that would confound the evaluation of delirium were excluded. Markov models were used to determine predictors for daily transition to delirium. Results One-hundred patients (46 SICU and 54 TICU) were enrolled. Prevalence of delirium was 73% in the SICU and 67% in the TICU. Multivariable analyses identified midazolam [OR 2.75 (CI 1.43–5.26, p = 0.002)] exposure as the strongest independent risk factor for transitioning to delirium. Opiate exposure showed an inconsistent message such that fentanyl was a risk factor for delirium in the SICU (p = 0.007) but not in the TICU (p = 0.936), while morphine exposure was associated with a lower risk of delirium (SICU, p = 0.069; TICU p = 0.024). Conclusions Approximately 7 out of 10 SICU and TICU patients experience delirium. In keeping with other recent data on benzodiazepines, exposure to midazolam is an independent and potentially modifiable risk factor for the transitioning to delirium.