Determinants of cerebral oximetry in patients undergoing off-pump coronary artery bypass grafting: an observational study.

BACKGROUND AND

OBJECTIVE

The present study investigated whether positioning of the heart during off-pump coronary artery bypass grafting leads to changes in regional cerebral oxygen saturation measured by near infrared spectroscopy.

METHODS

In 35 consecutive patients undergoing elective off-pump coronary artery bypass grafting, cerebral oxygen saturation was measured by near infrared spectroscopy. A 20% decrease from baseline values was considered to be cerebral hypoperfusion. Mean arterial pressure, cardiac index, arterial carbon dioxide partial pressure, central venous pressure, haemoglobin concentration, and body temperature were determined simultaneously. Each value was recorded at the following time points: at baseline; after positioning the heart for distal anastomoses of the left anterior descending artery, the circumflex, and the right coronary artery; after repositioning the heart; and after chest closure. Significant changes in each parameter from baseline were detected using repeated-measures analysis of variance. Determinants of cerebral oxygen saturation during surgery were analysed by means of generalized estimation equations.

RESULTS

Cerebral oxygen saturation remained constant during grafting of the left anterior descending artery and decreased significantly during grafting of the circumflex (P = 0.001) and the right coronary artery (P < 0.001). Cerebral hypoperfusion was found in seven (20%) patients. Changes in haemoglobin concentration (P = 0.014), arterial CO2 partial pressure (P = 0.001), cardiac output (P < 0.001), and central venous pressure (P = 0.014) determined alterations in cerebral oxygen saturation.

CONCLUSION

Positioning of the heart during off-pump coronary artery bypass grafting leads to a decrease in regional cerebral oxygen saturation. This decrease is associated with changes in cardiac output, haemoglobin concentration, arterial CO2 partial pressure, and central venous pressure.