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 (rSO2) were compared between the two perfusion methods.Results.
Immediately before cardiopulmonary bypass, baseline rSO2 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°C, rSO2 increased to 73.1% ± 8.8% and 74.1% ± 7.9% in the RCP and SCP groups, respectively. With circulatory arrest, rSO2 suddenly decreased. After starting cerebral perfusion, rSO2 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, rSO2 was 57.4% ± 12.2% for the RCP group and 71.7% ± 6.9% for the SCP group, and the ratio of rSO2 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 rSO2 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, rSO2 continued to decrease with time during RCP. An rSO2 ratio less than 0.7 could represent a critical lower limit.