Prolonged Double-Low Time and the Incidence of Postoperative Delirium in Surgical ICU Patients

An intraoperative double-low condition is defined as concurrent low values for bispectral index (BIS) and mean arterial pressure (MAP), and may predict perioperative outcomes. We hypothesized that prolonged double-low times might be associated with an increased incidence of postoperative delirium. We conducted a single-center retrospective observational study on patients who had been admitted to our hospital's intensive care unit (ICU) after surgery and whose BIS and MAP data had been recorded during general anesthesia. The primary outcome was the incidence of postoperative delirium. A double-low condition was defined as BIS < 45 and MAP <75 mmHg. The total double-low time was calculated in 1-min increments and used to divide the patients into quintiles. Multiple logistic regression analyses were conducted. Among the 334 patients included in the study, the incidence of postoperative delirium was 15.6% (n=52). Multiple logistic regression analysis revealed that a prolonged double-low time, defined as a total double-low time of > 42 min (i.e., third, fourth, and fifth quintiles), was significantly associated with an increased incidence of postoperative delirium (adjusted odds ratio: 2.61, 95% confidence interval: 1.27-5.37, p=0.009). Prolonged double-low time during general anesthesia was independently associated with an increased incidence of postoperative delirium in surgical ICU patients.