Study details delirium incidence, duration and severity in critically ill patients with COVID-19

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In a cohort of critically ill patients with coronavirus disease 2019 (COVID-19), delirium without coma occurred in 29.1% of patients, according to a study published in Critical Care Explorations. In addition, the study found that delirium persisted for approximately 5 days and occurred at high severity.

Sikandar H Khan, Indiana University School of Medicine, Indianapolis, Indiana, and colleagues retrospectively extracted data of 268 patients admitted to the ICUs of Methodist Hospital and Eskenazi Health for COVID-19 from March 1 to June 7, 2020. The mean age of the cohort was 58.4 years and 40.3% were females. The median Charlson Comorbidity Index score was 1, with hypertension (60.1%), obesity (57.5%), tobacco use (25.7%) and chronic lung disease (20.9%) being the most frequent comorbid conditions. The median Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 18, and 80.2% of patients in the cohort underwent invasive mechanical ventilation.

The primary outcomes were the rate of delirium and delirium/coma duration during the first 14 days of admission to the ICU. Coma was assessed using the Richmond Agitation-Sedation Scale (RASS) and delirium was identified through the Confusion Assessment Method for the ICU (CAM-ICU).The secondary outcome of delirium severity was assessed using the CAM-ICU-7, which requires all components of the CAM-ICU to be assessed for each patient rather than a dichotomous CAM-ICU positive or negative result.

Study data showed that delirium without coma occurred in 29.1% (78/268), delirium prior to coma in 27.9% (75/268), and delirium after coma in 23.1% (62/268) of the cohort. In patients with delirium, 61.9% (133/215) were positive on the first CAM-ICU assessment. Further, patients with delirium had higher median APACHE II severity of illness scores (20 vs 11; P < 0.001) and were more likely to be mechanically ventilated (93.5% vs 26.4%; P < 0.001) than patients without delirium. Meanwhile, PaO₂:FiO₂ ratios (81.8 vs 103.1; P = 0.001) and Glasgow Coma Scale scores (9.0 vs 15.0; P < 0.001) were lower in patients with delirium during the first 24 hours of ICU admission compared with those without delirium.

Among patients who developed delirium, the median delirium duration was 5 (interquartile range [IQR], 2–8) days. Hypoactive delirium, reported in 87.4% of patients, was the most common subtype. By day 14, the median delirium/coma-free days was 5 (IQR, 4–11), and the median CAM-ICU-7 score was 6.5 (IQR, 5–7) indicating severe delirium. Patients had a median RASS of –2 (IQR, –3 to 0) at the time of ICU admission, indicating light sedation.

Further, patients with delirium had greater mechanical ventilation days (median, 9.1 vs 0; P < 0.001) and ICU days (median, 14.4 vs 4.0; P < 0.001) compared with patients without delirium. Meanwhile, greater frequency of orders was also noted among patients with delirium for benzodiazepines (86.5% vs 45.3%; P < 0.001), opioids (94.4% vs 50.9%; P < 0.001), propofol (83.3% vs 24.5%; P < 0.001), and dexmedetomidine (34.9% vs 5.7%; P < 0.001) compared with patients without delirium. In the logistic regression model consisting of age, receipt of mechanical ventilation, APACHE II scores, Glasgow Coma Scale, RASS , and sedative medications, only mechanical ventilation was significantly associated with greater odds of developing delirium (odds ratio, 5.0; 95% confidence interval, 1.1–22.2; P = 0.033).

“To the best of our knowledge, our study is the first to describe delirium rates, duration, and severity in critically ill patients with COVID-19 using standardized delirium assessment tools,” the authors wrote. “Due to the increased risk of mortality and morbidity following delirium, including the development of long-term cognitive impairment and post intensive care syndrome, this study has important implications for clinical practice, the recovery of patients with COVID-19 admitted to intensive care, public health decision making, and even future research priorities.”

“Given these findings, continued attention to prevent and manage delirium, and a deeper understanding of the virus’ neurotoxic effects are critical,” the authors added.