Effects of Postoperative Blood Pressure Management on Delirium Among Patients in the Intensive Care Unit After Cardiac Surgery: An Observational Cohort Study

Objectives: This study aimed to determine whether blood pressure control in the early postoperative period was associated with postoperative delirium in the cardiovascular intensive care unit (ICU).

Design: Observational cohort study.

Setting: Single large academic institution with a high volume of cardiac surgery.

Participants: Cardiac surgery patients admitted to the cardiovascular ICU after surgery.

Interventions: Observational study.

Measurements and main results: A total of 517 cardiac surgery patients had mean arterial pressure (MAP) data recorded minute-by-minute for 12 postoperative hours. The time spent in each of the 7 prespecified blood pressure bands was calculated, and the development of delirium was recorded in the ICU. A multivariate Cox regression model was developed using the least absolute shrinkage and selection operator approach to identify associations between time spent in each MAP range band and delirium. Compared with the reference band of 60-to-69 mmHg, longer durations spent in 3 bands were independently associated with a lower risk of delirium: 50-to-59 mmHg band (adjusted hazard ratio [HR] 0.907 [per 10 minutes]; 95% CI 0.861-0.955); 70-to-79 mmHg band (adjusted HR 0.923 [per 10 minutes]; 95% CI 0.902-0.944); 90-to-99 mmHg band (adjusted HR 0.898 [per 10 minutes]; 95% CI 0.853-0.945).

Conclusions: The MAP range bands above and below the authors' reference band of 60-to- 69 mmHg were associated with decreased risk of ICU delirium development; however, this was difficult to reconcile with a plausible biologic mechanism. Therefore, the authors did not find a correlation between early postoperative MAP control and increased risk of the development of ICU delirium after cardiac surgery.