Tomographic assessment of regional cerebral blood flow in cerebral complications after extracorporeal circulation for cardiac surgery

We investigated the cerebral complications following extracorporeal circulation for cardiac surgery using neuroimaging techniques. Twelve consecutive patients were studied; each patient had neurological examination, neuropsychological assessment, transmission computerized tomography, and regional cerebral blood flow (rCBF) study with single photon emission computed tomography, both pre- and postoperatively. After surgery, neither neurological symptoms nor morphostructural lesions were observed. However, 6 patients presented with cognitive function impairments and 9 patients showed brain areas of hypoperfusion. Cognitive and perfusional postoperative findings were consistent in 6 patients. Judged as a group, we observed after surgery neither the occurrence of a unique general pattern of rCBF decrease nor a significant rCBF reduction in the brain areas corresponding to the arterial watershed territories. In conclusion these results indicate that: (a) the neuropsychological assessment and the rCBF study yield a more sensitive evaluation of the cerebral complications of cardiac surgery; (b) both the patterns of cognitive deficits and the changes in rCBF distribution support the microembolic rather than the hemodynamic pathogenesis of brain damage following extracorporeal circulation for cardiac surgery.