Hypobaric type oxygenators during cardiopulmonary bypass for cardiac surgery to reduce gaseous microemboli: A randomized controlled trial

Objectives: Neurological complications after cardiac surgery have been associated with gaseous microemboli generated during cardiopulmonary bypass. We undertook a trial to assess whether a novel dual-chamber oxygenator, designed to denitrogenate the blood, could reduce cerebral gaseous microemboli compared with conventional cardiopulmonary bypass. Methods: In this single-center, single-blind, parallel-group randomized controlled trial, adults undergoing elective or urgent coronary artery bypass grafting with or without aortic valve replacement (±coronary artery bypass grafting) were assigned to the novel oxygenator or conventional cardiopulmonary bypass. Continuous intraoperative transcranial Doppler monitoring quantified cerebral gaseous microemboli in both middle cerebral arteries. Secondary outcomes included serum S100 Beta Protein Biomarker concentrations, cardiopulmonary bypass circuit gaseous microemboli counts, and 30-day adverse events. Results: The trial stopped early after recruiting 25 participants (coronary artery bypass grafting = 19; aortic valve replacement = 6) because elevated gaseous microemboli counts were not lower in the novel oxygenator group. Among patients undergoing coronary artery bypass grafting, median total gaseous microemboli counts were higher with the novel cardiopulmonary bypass than conventional cardiopulmonary bypass (right middle cerebral artery 170 [42-749] vs 129 [45-184]; left middle cerebral artery 234 [173-464] vs 93 [40-428]; incidence rate ratio 1.55; 95% CI, 0.64-3.74). No participant experienced neurological injury, and 1 patient died within 30 days. Conclusions: A novel, dual-chamber oxygenator for cardiopulmonary bypass did not reduce gaseous microemboli in the middle cerebral artery of patients during cardiac surgery.