[Cerebral oxygen saturation (rSo2) during open heart surgery and postoperative brain dysfunction].

We studied the occurrence of brain dysfunction in regards to changes in cerebral oxygen saturation (rSo2) during open heart surgery. The subjects were 68 patients with the average age of 61 years. For the evaluation of brain function, Hasegawa Dementia Scale was used, and those patients whose scores were less than 23 points, or had decreased by more than 3 points from preoperative scores on the 7th postoperative day were categorized as the brain dysfunction group. There were 14 (21%) postoperative brain dysfunction cases. Although rSo2 values during surgery ran at 70-65% level, the brain dysfunction group showed significantly lower values throughout the entire procedures, with the lowest value being 61% during cardiopulmonary bypass. The patients in the dysfunction group were of older ages and postoperative lower cardiac index, which indicated that the occurrence of brain dysfunction is greatly influenced by low cerebral blood flow. Effect from the operative procedures and CPB alone seemed to be small. Cerebral oxygen saturation (rSo2) is believed to be a useful monitor of cerebral blood flow, and occurrence of brain dysfunction may be expected at values lower than 60%.