Near infrared spectroscopy changes during hypothermic circulatory arrest with retrograde cerebral perfusion

We report on the changes in cerebral near-infrared spectroscopy during grafting of a thoraco-abdominal aneurysm. A 58-year-old man presented with a complex dissecting aortic aneurysm. Repair of the aneurysm was performed under hypothermic circulatory arrest with retrograde cerebral perfusion. Cerebral near-infrared spectroscopy monitoring revealed a reduction in the values recorded for total haemoglobin, oxygenated haemoglobin and cytochrome aa3 along with an increase in deoxygenated haemoglobin during circulatory arrest. When retrograde cerebral perfusion was commenced the signals representing total haemoglobin, oxygenated haemoglobin and cytochrome aa3 were all restored to near baseline values. Deoxygenated haemoglobin, however, remained elevated. These changes support the hypothesis that some cerebral perfusion occurs during retrograde cerebral perfusion.