The association of intraoperative factors with the development of postoperative delirium

To examine the association of intraoperative factors, including route of anesthesia, hemodynamic complications, and blood loss, with the development of postoperative delirium.

We studied 1,341 patients 50 years of age and older admitted for major elective noncardiac surgery at an academic medical center. Data on route of anesthesia, intraoperative hypotension, bradycardia and tachycardia, blood loss, number of blood transfusions, and lowest postoperative hematocrit were obtained from the medical record. Delirium was diagnosed by using daily interviews with the Confusion Assessment Method, as well as from the medical record and the hospital's nursing intensity index.

Postoperative delirium occurred in 117 (9%) patients. Route of anesthesia and intraoperative hemodynamic complications were not associated with delirium. Delirium was associated with greater intraoperative blood loss, more postoperative blood transfusions, and postoperative hematocrit <30%. After adjusting for preoperative risk factors, postoperative hematocrit <30% was associated with an increased risk of delirium (odds ratio = 1.7, 95% confidence interval 1.1-2.7).

Further study is required to determine whether transfusion to keep postoperative hematocrit above 30% can reduce the incidence of postoperative delirium.