The Effect of Substrate Load and Blood Glucose Management on Cerebral Dysfunction Following Cardiopulmonary Bypass

Seventy patients undergoing elective coronary artery bypass grafting were prospectively randomized into either of two primes: 5% dextrose or Hartmann's solution. The groups were comparable. Neuropsychological assessment was performed before and eight weeks after surgery. During bypass blood glucose concentrations rose to a mean of 26 mmol/L in the 5% dextrose group and 6 mmol/L in the Hartmann's group. No deaths occurred in either group; 2 clinically evident neurological events were noted, both taking place in the hyperglycemic group. Detailed analysis of the results showed differences between the groups. When score changes between tests were assessed it was found that in 17 of the 18 versions of the tests more patients in the hyperglycemic group deteriorated than the normoglycemic controls. With a two-tailed binomial statistic this difference was significant at the 5% level. Learning ability was likewise found to worsen in the hyperglycemic group after surgery. Hyperglycemia may be a detrimental factor in the development of postcardiac surgical intellectual dysfunction. The authors would advocate the avoidance of glucose-containing bypass primes and the close monitoring of blood glucose during cardiopulmonary bypass.