Covert Critical Illness Encephalopathy: Impairments That Escape Detection by Guideline Recommended, Protocolized Assessments.

OBJECTIVES

To determine whether cognitive impairments of important severity escape detection by guideline-recommended delirium and encephalopathy screening instruments in critically ill patients.

DESIGN

Cross-sectional study with random patient sampling.

SETTING

ICUs of a large referral hospital with protocols implementing the Society of Critical Care Medicine's ICU Liberation Bundle.

PATIENTS

Patients with a heterogeneous mix of primary organ system conditions leading to critical illness and with no abnormal findings scored in Confusion Assessment Method for the ICU (CAM-ICU) screening, Richmond Agitation-Sedation Scale (RASS) 0, and Glasgow Coma Scale (GCS) 15, indicating they were alert, fully oriented, and following commands with no delirium or findings to indicate subsyndromal delirium.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated 50 patients, age 54 ± 16 years. Trained critical care nurses assessed patients at regular intervals using the CAM-ICU, RASS, and GCS per a protocol. We performed a battery of psychometric cognitive tests using the NIH Toolbox. Executive functions linked to attention and inhibitory control, and processing speed were 1.5 sd below population norm (both p < 0.01). Working memory and cognitive flexibility were also significantly, but less severely, impaired ( p < 0.01 and p = 0.026). Nearly two-thirds (64%) of the patients scored at least 1.5 sd worse than demographically adjusted means in two or more cognitive domains, a commonly used diagnostic criterion for cognitive impairment.

CONCLUSIONS

Substantial cognitive impairment is present among critically ill patients with no abnormalities detected by standard delirium and encephalopathy assessments.