Cognitive decline after cardiac surgery: proposal for easy measurement with a new test

Neuropsychological dysfunction is a recognized complication after cardiac surgery. Attention, concentration, short term memory, and speed of mental processing are commonly involved. We evaluated prospectively the incidence of cognitive impairment in our population using a single test: Paced Auditory Serial Addition Test.

We analysed 132 patients (mean age 67 years) undergoing elective cardiac surgery (63.6% valvular, 25% coronary artery bypass grafting and rest mixed procedures) between January and June 2003. We did not include patients with previous history of cognitive impairment, major psychiatric disorders or stroke. Paced Auditory Serial Addition Test was performed before and after surgery (mean, 7 days) and in outpatient follow-up (mean, 4 months).

None of the patients suffered a major neurological complication. Mean preoperative Paced Auditory Serial Addition Test score was 27.04+/-11.05, 25.81+/-11.83 in immediate postoperative and 27.93+/-13.11 in follow-up. A significant postoperative neuropsychological dysfunction (test scale decline more than 1 S.D.) was shown in 45.5% of the patients. In 48.8%, decline persisted in follow-up. Valvular surgery and low preoperative Paced Auditory Serial Addition Test score were significant risk factors for immediate postoperative neuropsychological dysfunction. Valvular surgery and female sex were significant in multivariable analysis. Considering follow-up, older age is the only significant risk factor for cognitive impairment.

Using a single, quantifiable and easy and quickly applied test such as the Paced Auditory Serial Addition Test, we found an incidence of cognitive decline after cardiac surgery similar to that previously described. Valvular surgery and older age are the main risk factors for neuropsychological dysfunction in our population.