No convincing association between post-operative delirium and post-operative cognitive dysfunction: a secondary analysis.

BACKGROUND: Post-operative delirium and post-operative cognitive dysfunction (POCD) are both common but it has not been clarified how closely they are associated. We aimed to assess the possible relationship in a secondary analysis of data from the 'Surgery Depth of anaesthesia and Cognitive outcome'- study. METHODS: We included patients aged ≥ 60 years undergoing non-cardiac surgery planned for longer than 60 min. Delirium was assessed according to the Diagnostic and Statistical Manual of Mental Disorders IV criteria in the post-anaesthesia care unit (PACU) as well as within the first week after surgery. Cognitive function was assessed with a neuropsychological test battery. Multivariable analysis of POCD was performed with consideration of predisposing and precipitating factors. RESULTS: Of 1277 randomized patients, 850 (66.6%) had complete data. Delirium was found in 270 patients (32.9% of 850). We detected POCD in 162 (20.9% of 776) at 1 week and in 52 (9.4% of 553) at 3 months. In multivariable analysis (n = 808), delirium had no overall effect on POCD (P = 0.30). Patients with no delirium in PACU but with postoperative delirium within 7 days had an increased risk of POCD at 3 months (OR = 2.56 (95%-confidence interval: 1.07-6.16), P = 0.035). No significant association was found for the other subgroups. CONCLUSIONS: There is no clear evidence that postoperative delirium is independently associated with POCD up to 3 months.

Incidence and risk factors for cognitive dysfunction in patients with severe systemic disease.

OBJECTIVE: To determine the relevance of surgery and other causative factors to the incidence of postoperative cognitive dysfunction (POCD) in patients with severe systemic disease. METHODS: This observational study included 107 noncardiac surgical patients and 26 nonsurgical control subjects, all of whom had an American Society of Anesthesiologists physical classification status of 3. Cognitive assessment was performed preoperatively and 7 days postoperatively, or with a 7-day interval for the control group. POCD was calculated as a combined Z-score. Mini Mental State Examination (MMSE) was used to exclude patients with pre-existing cognitive deficit (MMSE score ≤ 23). Surgical and other factors including duration of surgery/anaesthesia and length of stay in the intensive care unit (ICU) were recorded. RESULTS: After 7 days, POCD was found in 40/107 (37.4%) surgical patients compared with 4/26 (15.4%) nonsurgical controls. Preoperative MMSE score, duration of surgery/anaesthesia, and length of stay in the ICU and hospital were associated with POCD. Logistic regression analysis revealed that preoperative MMSE score was an independent predictor of POCD. CONCLUSION: Lower baseline MMSE score was the only independent predictor for POCD in patients with severe systemic disease.