Cerebral blood flow and cognitive dysfunction after coronary surgery.

Abstract

Postoperative cognitive dysfunction after cardiac surgery has been attributed both to embolic events and periods with reduced cerebral perfusion. We investigated whether cognitive dysfunction after coronary surgery is associated with changes in regional cerebral blood flow (CBF) using single photon emission computed tomography. Before surgery and at discharge, 15 coronary surgery patients were studied. Global and regional CBF were measured using a brain-dedicated single photon emission computed tomography scanner, and neuropsychological testing with seven subtests was performed. Postoperative cognitive dysfunction was defined as a Z score above 2. Normative single photon emission computed tomography data were available from 26 healthy age-matched controls. Preoperative global CBF was significantly lower in patients compared with controls (53.7 versus 46.1 mL/100 g/min, p = 0.006). After surgery, global CBF significantly decreased in the patient group (46.1 versus 38.6 mL/100 g/min, p = 0.0001). No significant differences were detected in regional CBF. Cognitive dysfunction was identified in 4 of the 15 patients (26.7%, 95% CI 7.8% to 55.1%). No correlation was found between the neuropsychological Z score and global or regional CBF. The significant decrease in CBF after coronary surgery was uniformly distributed and was not correlated to postoperative cognitive dysfunction.