Comment: This pilot study encourages further research, because there are many unanswered questions. No conclusions can be made until larger groups of patients are studied and postoperative neurophysiologic testing is done in addition to MRI scans. Of interest also would be an assessment of the effect of different anesthetic techniques, drugs, cardiopulmonary bypass length, and body temperature. The patients in this study group were maintained by Alphastat management, which does not correct blood gases for temperature. One wonders whether brain swelling would be worse if pH stat management had been used, in which there is gas correction for temperature.