Evidence for Improved Cerebral Function After Minimally lnvasive Bypass Surgery

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Abstract
Neurological impairment is a major cause of morbidity after cardiac surgery and may be associated with occurrence of cerebral microemboli generated during cardiopulmonary bypass (CPB). This study evaluates cerebral dysfunction following coronary artery surgery on-pump and off-pump. Neurological outcome was evaluated in 322 patients with a coronary artery 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 transient signals (HITS) by ultrasonic insonnation of the middle cerebral artery indicating the presence of emboli within the vessel lumen. Transcranial near-infrared spectroscopy measured cerebral venous oxygen saturation for adequate perfusion. Postoperatively, all patients were subjected to the antisaccadic eye movement (ASEM) test, a sensitive indicator of neurocognitive deficits secondary to frontal lobe dysfunction. While there was no significant difference in O2 saturation, the number of microemboli HITS generated 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. 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.