Predictive factors for the duration of subsyndromal delirium in the intensive care unit

To evaluate the duration of subsyndromal delirium (SSD) in intensive care unit (ICU) patients and the factors associated with SSD duration.

This retrospective study included adult patients admitted to the ICU of Affiliated Hospital of Nantong University between December 2019 and June 2020. All patients with Richmond Agitation Sedation Scale scores of ≥-2 were evaluated every 8 h using the confusion assessment method of the intensive care unit (CAM-ICU) until the patients with SSD were negative, progressed to delirium, fell into a coma, died, or were discharged from the ICU. Multivariable Cox regression analyses were performed to determine the factors associated with SSD duration.

Of the 388 patients, 53.6% had SSD, and 20.7% progressed from SSD to delirium. The duration of SSD ranged from 8 to 248 h, and the median duration was 48 h (interquartile range, 24-72). Age (hazard ratio [HR] = 0.985, 95% confidence interval [CI], 0.971-0.999, p = 0.035), surgery or not (HR = 0.514; 95% CI, 0.310-0.850; p = 0.010), duration of ventilation (HR = 1.003; 95% CI, 1.000-1.006; p = 0.044), duration of hypoxia (HR = 0.212; 95% CI, 0.103-0.438; p < 0.001), and adapted cognitive exam scores (HR = 1.057; 95% CI, 1.030-1.085; p < 0.001) were independently associated with the duration of SSD.

The duration of SSD was associated with age, surgery, duration of ventilation, duration of hypoxia, and cognitive function. SSD has a high incidence among ICU patients, and many patients progress to delirium.

The study team met with public members of the evaluation teams throughout the project in a series of workshops. Workshops informed study design, data collection tools and data interpretation.

ICU staff should pay attention to SSD patients with older age, history of surgery, longer duration of ventilation, prolonged duration of hypoxia, and lower ACE scores.