Transient electroencephalographic suppression with initiation of cardiopulmonary bypass in pigs: blood versus nonblood priming

Electroencephalographic (EEG) changes have been reported with cardiopulmona ry bypass (CPB). We tested whether the type of priming solution (blood vers us nonblood) affected the EEG. Twenty-six anesthetized pigs (29.5 +/- 1.6 k g) were cannulated for CPB primed with 1 liter plasmalyte and 500 mi 6% het astarch (nonblood prime). EEG signals were recorded during the initiation o f normothermic CPB. Three minutes later, animals were weaned from CPB and a llowed to stabilize. CPB was reinstituted using the animals' hemodiluted bl ood as prime. We found that with nonblood prime, abrupt and marked EEG supp ression lasting 12.6 +/- 0.7 s was found in all animals, followed by gradua l resumption of baseline EEG activity. In contrast, CPB with blood prime ca used no detectable EEG changes. We conclude that severe reductions in EEG a ctivity occur after initiating CPB with nonblood prime; these reductions ar e not seen when using blood prime. The cause of EEG suppression is unknown, but may represent transient impairment of oxygen delivery to the brain cau sed by nonblood perfusion.