Effect of intensive care unit environment on in-hospital delirium after cardiac surgery

The etiology of postcardiac surgery delirium is complex. Our primary objective was to determine the effect of the postoperative environment on the prevalence of delirium by examining the in-hospital delirium rates in 2 postoperative intensive care units with differing physical infrastructure. We further sought to identify other risk factors associated with in-hospital delirium.

The rates of postoperative delirium were retrospectively examined in consecutive cardiac surgery patients during 2 separate 6-month periods. Environment 1 was characterized by a lack of physical barriers between bed spaces and was windowless, and environment 2 consisted of private rooms with physical barriers for each patient and with wall-to-wall exterior windows. Univariate and multivariate analyses to determine the risk factors associated with in-hospital delirium, including the effect of environment, were undertaken.

Of the 1010 patients studied, 148 (14.7%) experienced in-hospital delirium after cardiac surgery. The prevalence of delirium was not significantly different between environments 1 and 2 (16.1% vs 13.5%; P = .25). However, in patients younger than 65 years, the proportion of intensive care unit days on which delirium occurred was greater in environment 1 than in environment 2 (5.4% vs 1.7%; P = .006). Postoperative stroke or transient ischemic attack, mechanical ventilation longer than 24 hours, age 65 years or older, concomitant coronary artery bypass grafting and valve surgery, prehospital admission benzodiazepine use, a requirement for any postoperative blood product transfusion, and postoperative renal insufficiency were identified as risk factors.

The intensive care unit environment did not have a significant effect on the overall prevalence of delirium. However, that does not preclude the possibility that the intensive care unit environment might interact with other factors, such as age, in a complex manner. Attempts to reduce delirium by adjusting the intensive care unit environment alone will likely not be sufficient, and instead will require a more comprehensive multimodal approach.