Evidence for improved cerebral function after minimally invasive bypass surgery

Background: Neurological impairment is a major cause of morbidity after car diac surgery and may be associated with occurrence of cerebral microemboli generated during cardiopulmonary bypass (CPB). This study evaluates cerebra l dysfunction following coronary artery surgery on-pump and off-pump. Metho ds: Neurological outcome was evaluated in 322 patients with a coronary arte ry bypass graft (CABG). Conventional CPB was used (on-pump) in 305 patients and in 17 patients no CPB was used (off-pump). Intraoperatively, a pulsed- wave transcranial Doppler with a 2-MHZ probe measured high-intensity transi ent signals (HITS) by ultrasonic insonnation of the middle cerebral artery indicating the presence of emboli within the vessel lumen. Transcranial nea r-infrared spectroscopy measured cerebral venous oxygen saturation for adeq uate perfusion. Postoperatively, all patients were subjected to the antisac cadic eye movement (ASEM) test, a sensitive indicator of neurocognitive def icits secondary to frontal lobe dysfunction. Results: While there was no si gnificant difference in O-2 saturation, the number of microemboli HITS gene rated was significantly higher in the on-pump group than the off-pump group . In the off-pump group, 16 (94%) of 17 patients had perfect scores on the ASEM test, while only 108 (35.4%) of 305 patients achieved a perfect score in the on-pump group (p < 0.01). Furthermore, while all patients in the off -pump group achieved at least 90%, 28% (86/305) in the on-pump group scored "zero" on the ASEM test. Conclusion: Cerebral dysfunction as evidenced by ASEM errors is common following coronary bypass on-pump, but rare with off- pump bypass surgery. Cerebral microemboli generated during CPB may account for this difference.