Abstract & Commentary

Patients Placed in Contact Isolation Are at Increased Risk for Delirium

By David J. Pierson, MD, Editor, Professor Emeritus, Pulmonary and Critical Care Medicine, University of Washington, Seattle.

This article originally appeared in the February 2012 issue of Critical Care Alert. At that time it was peer reviewed by William Thompson, MD Associate Professor of Medicine, University of Washington, Seattle. Dr. Pierson reports no financial relationships relevant to this field of study.

Synopsis: This retrospective study of all non-psychiatric patients admitted to an academic medical center found that although those placed in contact isolation from the time of admission had no increased risk for delirium, patients moved into isolation after admission were twice as likely to develop delirium during the hospital stay.

Source: Day HR, et al. Association between contact precautions and delirium at a tertiary care center. Infect Control Hosp Epidemiol 2012;33: 34-39.

To examine the association between being placed in contact isolation and delirium, Day and colleagues at the University of Maryland Medical Center reviewed administrative data on all patients admitted during a 2-year period ending in 2009. They excluded patients with underlying schizophrenia or bipolar disorder, those admitted to the psychiatry service, and alcohol-related admissions, as well as patients under age 18. Patients placed into contact isolation during hospitalization were stratified into those assigned this status on admission (because of pre-existing risk or documented infection) and those subsequently moved into isolation (because of positive surveillance or clinical cultures, acquired risk, or other factors). Because delirium is underdiagnosed and incompletely identified by its direct ICD-9 code, the authors also used as proxy measures the otherwise-unexplained use of haloperidol or other antipsychotic drugs and the use of physical restraints during the admission. They performed selected chart reviews to assure that the variables under study were recorded in the administrative database with acceptable accuracy.

Of 70,275 admissions during the study period, 60,151 (in 45,266 unique patients; 9869 ICU admissions) were evaluated after a priori exclusions. Contact precautions were used in 9684 admissions (15%), 58% of them from the time of admission and 42% commencing at some point following admission. The authors' criteria for delirium were met in 7721 admissions (13.5%). Overall, patients placed in contact isolation at any time during hospitalization were twice as likely to have delirium compared to non-isolated patients (16.1% vs 7.6%, respectively; odds ratio [OR], 2.4; 95% confidence interval [CI], 2.2-2.5%). There was no relationship between contact precautions and delirium among patients who were placed in isolation immediately on admission. However, being moved into isolation sometime after admission because of identification of a multiple-drug-resistant bacterium was associated with increased risk for delirium (OR, 1.75; 95% CI, 1.60-1.92; P < 0.01). Although ICU patients had significantly more delirium than non-ICU patients, being placed in contact isolation had no independent effect.

Commentary

Delirium, which occurs in about 15% of all hospitalized patients and is considerably more common in the ICU, is associated with numerous bad outcomes, including increased mortality, morbidity, and length of stay. Under current recommendations by the Centers for Disease Control and Prevention, contact precautions — including the use of gloves and gowns and isolation in a private room — are now used in a substantial number of hospitalized patients. Several studies have documented that physicians, nurses, and other clinicians interact with patients in isolation less often than non-isolated patients, and that those in isolation have more symptoms of depression and anxiety. Because decreased environmental stimuli predispose to delirium, it is hardly surprising that patients placed in isolation are more likely to develop this important disorder.

This study does not show that isolation causes delirium. Patients placed in isolation had increased mortality and lengths of stay, were more likely to be admitted to the ICU, and had more positive cultures suggesting clinical infections with resistant organisms than patients who were never placed in contact precautions. Thus, delirium was likely influenced by some or all of these and other factors that could not be controlled for in a retrospective study. The fact that patients placed in isolation from the time of admission — because of a past history of colonization with resistant organisms or the presence of specific risk factors — did not have a higher risk for delirium suggests that those who required the institution of contact precautions subsequent to admission were sicker and perhaps more predisposed to delirium in the first place. These points are acknowledged by the authors.

I think the important contribution of this study is the spotlight it shines on contact isolation as a marker for the development of delirium. Regardless of the contribution of isolation per se to this development, knowing that isolated patients are at increased risk can help — at the level of the individual clinician as well as for hospital policy — with respect to efforts at early detection, appropriate treatment, and prevention of this important complication of acute illness.