Cerebral oxygen saturation assessed by near-infrared spectroscopy during coronary artery bypass grafting and early postoperative cognitive function.

BACKGROUND

Cerebral oxygen saturation (ScO2) can be assessed by near-infrared spectroscopy. We investigated the correlation between early postoperative cognitive performance and intraoperative ScO2 in a prospective observational setting.

METHODS

Forty-seven patients undergoing elective coronary artery bypass grafting with cardiopulmonary bypass underwent preoperative and postoperative neuropsychological evaluation. Patients were classified according to the presence or absence of postoperative cognitive dysfunction. Cognitive dysfunction was defined as an individual test score decrease of more than one standard deviation in two or more of the five tests. During operation ScO2 was continuously measured using an INVOS 4100 device. Cerebral oxygen saturation values were analyzed with reference to two cutoff points, which should reflect low cerebral oxygenation: an ScO2 less than 40% and a drop of more than 25% from individual baseline values. The duration and extent of ScO2 values below these two cutoff points was compared between the patients with and without cognitive dysfunction.

RESULTS

Sixteen patients (34%) showed postoperative cognitive dysfunction. Cerebral oxygen saturation values less than 40% occurred in 17 patients for a mean (+/- standard error of the mean) of 17.2 +/- 6.5 minutes, whereas a decrease of more than 25% from baseline values occurred in 37 patients for 52.7 +/- 7.8 minutes. The duration and extent below the two cutoff ScO2 values was similar in patients with and without cognitive dysfunction.

CONCLUSIONS

Intraoperative regional ScO2 as assessed by near-infrared spectroscopy with the INVOS 4100 device is not predictive for postoperative cognitive performance in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.