In patients with a critical illness resulting from acute respiratory failure, shock, or both, sedative-associated, hypoxic, and septic delirium were predictive of long-term cognitive impairment up to 1 year after hospital discharge, according to a study published in The Lancet Respiratory Medicine.

The investigators sought to describe the prevalence and duration of clinical phenotypes of delirium and to understand the relationships between these phenotypes and the severity of subsequent long-term cognitive impairment. The participants comprised patients ≥18 years of age who were in a medical or surgical intensive care unit (ICU) with respiratory failure, shock, or both, and who were part of 2 parallel studies: the Bringing to Light the Risk Factors and Incidence of Neuropsychological Dysfunction in ICU Survivors (BRAIN-ICU; Identifier ID: NCT00392795) study and the Delirium and Dementia in Veterans Surviving ICU Care (MIND-ICU; Identifier ID: NCT00400062) study.

All patients were evaluated at least once daily for delirium using the Confusion Assessment Method-ICU to identify nonmutually exclusive phenotypes of delirium based on the presence of sepsis, hypoxia, sedative exposure, or metabolic (hepatic or renal) dysfunction. At 3 and 12 months postdischarge, cognition was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

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A total of 1049 participants were enrolled between March 14, 2007, and May 27, 2010; 8 participants could not be included in the final analysis. Of the remaining 1040 participants, 708 survived to the 3-month follow-up and 628 survived to the 12-month follow-up. Delirium, which affected 71% (740 of 1040) of the participants at some point during the study, occurred on 31% (4187 of 13,434) of the participant-days. Of the 4187 participant-delirium days, a single delirium phenotype was present during only 32% (1355 of 4187) of all delirium days, whereas ≥2 phenotypes were present during 68% (2832 of 4187) of all delirium days.

The most common type of delirium reported was sedative-associated delirium (detected during 63% [2634 of 4187] of the delirium days), with a longer duration of sedative-associated delirium predicting a worse RBANS global cognition score 12 months later (difference in score comparing 3 days vs 1 day, –4.03; 95% CI, –7.80 to –0.26). Likewise, longer durations of hypoxic delirium (–3.76; 95% CI, –7.16 to –0.37), septic delirium (–3.67; 95% CI, –7.13 to –0.22), and unclassified delirium (–4.70; 95% CI, –7.16 to –2.25) were all also predictive of worse cognitive function at 12 months, whereas duration of metabolic delirium was not (1.14; 95% CI, –0.12 to 3.01).

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The investigators concluded that clinicians should consider sedative-associated, hypoxic, and septic delirium, which often coexist, as distinct signs of acute brain injury and attempt to identify all potential risk factors that may have an effect on long-term cognitive impairment in these individuals. Specific phenotypes of delirium during critical illness may have important clinical implications with respect to long-term outcomes and should thus be a focus of future research and clinical efforts on improving patient safety.


Girard TD, Thompson JL, Pandharipande PP, et al. Clinical phenotypes of delirium during critical illness and severity of subsequent long-term cognitive impairment: a prospective cohort study. Lancet Respir Med. 2018;6(3):213-222.