Retrograde cerebral perfusion versus selective cerebral perfusion as evaluated by cerebral oxygen saturation during aortic arch reconstruction

Background. Time limits for neuroprotection by retrograde cerebral perfusion (RCP) and selective cerebral perfusion (SCP) in aortic arch aneurysm repair or dissection are undergoing definition. Methods. Using near-infrared optical spectroscopy, changes in regional cerebrovascular oxygen saturation (rSO(2)) were compared between the two perfusion methods. Results. Immediately before cardiopulmonary bypass, baseline rSO(2) was 63.9% +/- 6.9% for the RCP and 66.1% +/- 5.3% for the SCP group (no significant difference). As patients were core-cooled to 20 degrees C, rSO(2) increased to 73.1% +/- 8.8% and 74.1% +/- 7.9% in the RCP and SCP groups, respectively. With circulatory arrest, rSO(2) suddenly decreased. After starting cerebral perfusion, rSO(2) returned to prearrest values in the SCP group but continued decreasing steadily in the RCP group, to levels below baseline after about 25 minutes. At the end of perfusion, rSO(2) was 57.4% +/- 12.2% for the RCP group and 71.7% +/- 6.9% for the SCP group, and the ratio of rSO(2) to baseline value was 0.89 for RCP and 1.08 for SCP despite a shorter brain perfusion time for RCP (38.8 +/- 18.0 versus 103.3 +/- 43.3 minutes). Three of 5 patients whose ratios of rSO(2) to baseline at the end of brain protection were 0.7 or less had neurologic deficits. Conclusions. Although SCP showed no clinically important time limitation, rSO(2) continued to decrease with time during RCP. An rSO(2) ratio less than 0.7 could represent a critical lower limit.