Cardiopulmonary bypass (CPB) is essential for cardiac surgery but poses risks, including gaseous micro emboli (GME). While the incidence of stroke—a common clinical consequence of embolism—ranges from 1-5% in cardiac surgery, prevalence of GME during CPB remain poorly understood.

To quantitatively compare GME incidence in the arterial line between cavoatrial and bicaval cannulation during open-heart surgery. Secondary exploratory objectives include evaluating the impact of venous reservoir volume on GME, and the correlation between GME in the venous and arterial lines.

This single center randomized controlled trial was conducted at Sahlgrenska University Hospital, Sweden. Patients ≥18 years undergoing planned aortic valve repair/replacement with cavoatrial cannulation, or mitral valve repair/replacement with bicaval cannulation, with or without coronary artery revascularization, were screened for eligibility. Patients were further randomized to either venous reservoir volume of ≥300 mL (control) or 200–300mL (intervention). GME detection was performed using GAMPT BCC300 with probes positioned at multiple locations within the CPB circuit.

39 patients were included. No significant differences in GME quantity in the arterial line were observed between the cannulation methods (count p=.444; volume p=967). Similarly, no significant differences were found based on venous reservoir volume (count p=.074; volume p=.166). Furthermore, no significant correlation was observed between GME in venous line entering the arterial line (count p-value=492; volume p-value=.750). The CPB circuit effectively removed 99.14% of GME, with no adverse events reported.

No significant differences were found in arterial GME count or volume between cavoatrial and bicaval cannulation during CPB. These findings underscore the importance of the bypass circuit’s air-handling capacity, as well as the role of modern oxygenators and arterial line filters in effectively minimizing the passage of GME.