The effects of postoperative pain and its management on postoperative cognitive dysfunction

To determine risks for postoperative cognitive dysfunction (POCD), the authors conducted a prospective cohort study of 225 patients >= 65 years of age undergoing noncardiac surgery. Cognitive testing using the Word List, Verbal Fluency, and Digit Symbol tests was conducted for each patient preoperatively and 1 and 2 days postoperatively in patients without postoperative delirium. POCD was defined as meeting statistical criteria for decline from the patient's preoperative performance levels on at least two of the three cognitive tests. Multivariate logistic regression analysis determined the association between pain and postoperative analgesia with POCD after controlling for demographics, comorbidities, preoperative level of cognitive and daily functioning, preoperative medications, duration and type of anesthesia, and adverse events. Patients were on average 72 years old and 13% of patients experienced POCD on day 1, 7% on day 2, and 15% had POCD on either day 1 or day 2 after the surgery. Multivariate regression analyses revealed that only postoperative analgesia was associated with the development of POCD. Compared with those receiving postoperative analgesia through a patient-controlled analgesia device that administered opioids intravenously, those who received postoperative analgesia orally were at significantly lower risk for the development of POCD (odds ratio: 0.22; 95 % confidence interval: 0.06- 0.80; Wald chi-square = 5.36, df=1, p = 0.02). Older patients undergoing noncardiac surgery who are not delirious can experience significant declines in cognitive functioning postoperatively. Those at least risk of experiencing POCD were those who received postoperative analgesia orally.