THE IMPACT OF POSTOPERATIVE PAIN ON THE DEVELOPMENT OF POSTOPERATIVE DELIRIUM

We performed a prospective observational study to examine the role of postoperative pain and its treatment on the development of postoperati ve delirium. Pain was measured in direct patient interviews using a vi sual analog scale (VAS) and was assessed for pain at rest, pain with m ovement, and maximal pain over the previous 24 h. Postoperative deliri um was diagnosed during these interviews by using the confusion assess ment method (CAM) and/or by using data from the medical record and the hospital's nursing intensity index. The method of postoperative analg esia, type of opioid, and cumulative opioid dose were also recorded. A fter controlling for known preoperative risk factors for delirium (age , alcohol abuse, cognitive function, physical function, serum chemistr ies, and type of surgery), higher pain scores at rest was associated w ith an increased risk of delirium over the first 3 postoperative days (adjusted risk ratio 1.20, P = 0.04). Pain with movement and maximal p ain were not associated with delirium. Method of postoperative analges ia, type of opioid, and cumulative opioid dose were not associated wit h an increased risk of delirium. We conclude that more effective contr ol of postoperative pain reduces the incidence of postoperative deliri um. Implications: We performed daily interviews in a large population of patients undergoing noncardiac surgery to measure their level of pa in and development of delirium. We found an association between higher pain levels at rest and the development of delirium. Our results sugg est that better control of postoperative pain may reduce this serious complication.