Neuropsychologic dysfunction after CABG: standard cardiopulmonary bypass versus off-pump CABG

Objectives

With the introduction of lesser invasive strategies in cardiac surgery that do not require cardiopulmonary bypass (CPB), it is expected that the incidence of postoperative neuropsychologic disorders will decrease. The difference in effect on postoperative neuropsychologic dysfunction in patients undergoing coronary artery bypass grafting (CABG) using CPB or off-pump surgery is investigated.

Method

10 patients undergoing standard CABG with CPB (CABG-group; nine male/one female) and 17 patients receiving off-pump CABG without CPB (OPCAB-group; 13 males/four females) were evaluated preoperatively, 7 days postoperatively and 1 month postoperatively. The CDR computerised test battery was administered and included single and choice reaction time, number vigilance, memory scanning, and word and picture recognition. Overall cognitive ability within and between the two groups was analyzed using one sample t-tests and analysis of variance.

Results

Mean age was similar [CABG 61.2 years, standard deviation (SD) 9.1; OPCAB 58.0 years, SD 8.9; P = not significant). Preoperative left ventricular function was similar (ratio impaired/good: CABG 3/10 and OPCAB 3/17; P = not significant). In the CABG group, two patients had prior cardiac surgery. The average number of distal anastomosis was 3.4 (SD 0.7) for CABG and 1.4 (SD 0.5) for OPCAB (P < 0.001). Preoperatively there were no significant differences between the two groups on any of the tasks. At both 7 and 30 days postoperatively a significant difference in overall cognitive function between the CABG and OPCAB group was observed. In the CABG group a pattern of cognitive function decline was seen at 7 days postoperatively, but this resolved at 30 days. In the OPCAB group improvement in cognitive function was seen at both 7 and 30 days postoperatively.

Conclusion

CABG with the use of CPB is associated with transient cognitive functional decline that is not apparent using OPCAB. The increasing use of operative techniques that do not require CPB is likely to reduce neuropsychologic dysfunction. Improvement in cognitive ability after OPCAB remains puzzling, and exploration of unknown factors that may cause this is warranted.