Clinically relevant cognitive impairment after cardiac surgery: a 6-month follow-up study

BACKGROUND AND PURPOSE: The majority of studies on neuropsychological complications after cardiac surgery used the raw variation of selective tests scores to define the occurrence of cognitive decline. We prospectively estimated the frequency of cognitive impairment after cardiac surgery, with a particular emphasis on persistent and clinically relevant cognitive decline. Possible baseline and operative predictors were also evaluated. METHODS: An extensive neuropsychological battery was administered to 110 patients (mean age 64.1+/-9.4 years; 70.9% males) undergoing cardiac surgery before and 6 months after the operation. After evaluating the variations in the cognitive performances, two independent neuropsychologists ranked the patients as unchanged-improved, mildly-moderately deteriorated, or severely deteriorated, using a global and functionally oriented judgement. The degree of the impairment was determined in relation to its impact on everyday life activities. RESULTS: Ten patients (9.1%) were ranked as severely deteriorated, 22 (20%) as mildly-moderately deteriorated, and 78 (70.9%) as unchanged-improved. Cognitively impaired patients were older (p=0.031), more often females (p=0.005), with a low education level (p=0.013). At multivariate analysis, female gender (odds ratio (OR) 6.14, 95% confidence interval (95% CI) 2.16-17.50), baseline use of beta-blockers (OR 4.55, 95% CI 1.30-15.92), and PaO2 at arrival in intensive care unit (OR for 1 mm Hg increment 1.012, 95% CI 1.004-1.020) were significant predictors of cognitive impairment of any degree. Positive predictors of severe cognitive impairment were history of hypertension (OR 5.33, 95% CI 1.03-27.64) and PaO2 at arrival intensive care unit (OR for 1 mm Hg increment 1.020, 95% CI 1.006-1.035), while education was protective (OR per year of increment 0.53, 95% CI 0.31-0.90). CONCLUSIONS: A considerable proportion of cardiac surgery patients may undergo clinically relevant cognitive impairment. The knowledge of variables influencing cognitive outcome is essential for the adoption of preventive measures.