Diabetes mellitus increases adverse neurocognitive outcome after coronary artery bypass grafting surgery

Background: Cognitive dysfunction is a well known problem in the postoperative period in cardiac surgery. We hypothesised that the incidence of postoperative cognitive dysfunction in patients with diabetes mellitus is higher than in the nondiabetic patient. Methods: Thirty-four patients (11 females, 23 males) with a mean age of 62.44 ± 7.52 undergoing on-pump CABG surgery were studied in a prospective manner. Fourteen patients had treated diabetes mellitus (Group I) and 20 were nondiabetic (Group II). All patients were operated upon by the same surgeon under standardised intra- and perioperative conditions. Patients with preoperative dementia (MMSE < 24) or advanced cerebrovascular disease were excluded. An extensive set of tests examining emotional and cognitive state, stress-coping and quality of life were performed preoperatively. Emotional and cognitive variables were assessed daily from day two to five postoperatively. Results: All tests showed comparable results between the groups preoperatively. The perfusion lasted considerably longer in Group I (102.5 ± 16.61 vs. 83.9 ± 14.1 min) as did the cross clamping (64.21 ± 18.31 vs. 51.75 ± 10.88 min). Postoperative cognitive outcome was significantly worse in Group 1 with regard to the Stroop Test (29.46 ± 8.6 vs. 24.01 ± 6.23, p = 0.02), the Abbreviated Mental Test (8.04 ± 0.71 vs. 8.68 ± 0.78, p = 0.02) and the Trial Making Test (35.72 ± 11.38 vs. 29.3 ± 7.77 p = 0.04). These differences persisted even after adjustment for perfusion- and cross-clamping time. Conclusion: The cognitive outcome in the early postoperative period is worse in diabetic patients compared to nondiabetics. Speed-related cognitive functions are mainly affected. Probably, this reflects a different physiology of cerebral perfusion during extracorporeal circulation. Optimising perfusion strategies to improve the outcome of diabetic patients should be the next topic of study.