Key Point

Delirium is common in nonventilated patients—occurring in about half—and often results in longer ICU and hospital stays, with the potential for additional poor outcomes.

NASHVILLE—Delirium and its effects have been extensively studied in patients in long-term care facilities and hospital wards. Studies of ICU patients found that between 60% and 80% of mechanically ventilated ICU patients experience delirium, and two studies found a relationship between delirium and severity of illness. Delirium was associated with unfavorable outcomes, including higher mortality. Furthermore, in mechanically ventilated ICU patients, every day spent in delirium was associated with impaired long-term cognitive function and a 10% higher risk of death.

The Society of Critical Care Medicine (SCCM) has recommended routine monitoring for delirium for all ICU patients. But in 2001 and 2002, only 5% of 912 intensivists surveyed reported that they monitor patients for ICU delirium. Many patients are treated in ICUs who do not need mechanical ventilation. Thus, to determine the association between delirium, length of stay in the ICU, length of stay in the hospital, and in-hospital mortality, researchers at Vanderbilt University Medical Center in Nashville undertook a two-year observational cohort study of nonventilated ICU patients. They found that delirium occurred almost half of the time and resulted in longer ICU and hospital stays. This study did not detect a relationship between delirium and mortality, but in this group of patients who are generally less ill than those treated with ventilators, a larger study might be necessary to detect such a difference.¹

Two hundred sixty patients were enrolled in the study. At least once per 12-hour shift, nurses assessed patients’ sedation levels and delirium states via the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Compliance with these bedside observations was 90% in more than 2,000 observations. At time of enrollment, demographic information, APACHE scores, and admission diagnoses were recorded. The Charlson Comorbidity Index, which takes into account the number and severity of preexisting conditions, was calculated.

Patients who scored positive for delirium on the CAM-ICU at any time were classified as having “ever-delirium,” and those with a negative score were classified as “never-delirium.”

THE CONSEQUENCES OF DELIRIUM

Of the 260 patients, 125 (48%) experienced delirium. No significant differences were noted between the ever-delirium and never-delirium groups with regard to age, ethnicity, Charlson comorbidity score, or admission diagnosis. The ever-delirium patients were older and had higher APACHE scores than did the never-delirium group.

The ever-delirium group had longer ICU stays by one day and were in the hospital for two days longer than the never-delirium group. At any given time during their stay in the ICU, the ever-delirium group had a 29% greater risk of remaining in the ICU—even after adjustment for covariates. In addition, the patients in the ever-delirium group had a 41% greater risk of remaining in the hospital.

Nineteen percent of patients in the ever-delirium group died, compared to 6% of the never-delirium group. Cox proportional hazards regression showed that after age, gender, ethnicity, coma status, APACHE score, and Charlson comorbidity score were controlled for, delirium was not significantly associated with time to in-hospital mortality.

According to the authors, this is the first study to document the incidence of delirium in a strictly nonventilated patient group. Their finding that delirium increases the length of both ICU and hospital stay is particularly relevant given the increasing resource use and economic burden of hospital care. “These data lend support to the SCCM clinical practice guideline recommendation for routine monitoring of delirium for all adult ICU patients using validated tools such as the CAM-ICU, which has been validated in ventilated and nonventilated critically ill patients.”

The authors also pointed out that while their patients had a lower severity of illness than patients in similar ICU studies, data have overwhelmingly shown delirium to be associated with prolonged hospital stay, dependency of care, subsequent institutionalization, and increased mortality. They stressed that their study complements and does not refute any previous findings.

Symptoms of delirium must be sought objectively, noted the authors. Anything else will result in undetected brain dysfunction. They concluded that “the alternative to daily monitoring for delirium is to persist with the status quo in which an estimated 60% to 80% of delirium is missed in the absence of standardized monitoring.”

—Gale Jurasek

Reference
1. Thomason JWW, Shintani A, Peterson JF, et al. Intensive care unit delirium is an independent predictor of longer hospital stay: a prospective analysis of 261 non-ventilated patients. Critical Care. 2005;9:R375-R381.

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