Although a growing body of evidence indicates superiority of minimized cardiopulmonary bypass (mCPB) systems over conventional CPB systems, limited venous return can result in severe fluctuations of venous line pressure which can result in gaseous emboli. In this study, we investigated the influence of sub-atmospheric pressures and volume buffer capacity added to the venous line on the generation of gaseous emboli in the mCPB circuit. Two different mCPB systems (MEC - Maquet, n=7 and ECC.O - Sorin, n=8) and a conventional closed cardiopulmonary bypass (cCPB) system (n=12) were clinically evaluated. In the search for a way to increase volume buffer capacity of mCPB systems, we additionally evaluated the 'Better Bladder' (BB) in a mock circulation by simulating, repeatedly, decreased venous return while measuring pressure and gaseous embolic activity. Arterial gaseous emboli activity during clinical perfusion with a cCPB system was the lowest in comparison to the mCPB systems (312±465 versus 311±421 with MEC and 1,966±1,782 with ECC.O, counts per 10 minute time interval, respectively; p=0.03). The average volume per bubble in the arterial line was the highest in cases with cCPB (12.5±8.3 nL versus 8.0±4.2 nL with MEC and 4.6±4.8 nL with ECC.O; p=0.04 for both). Significant cross-correlation was obtained at various time offsets from 0 to +35 s between sub-atmospheric pressure in the venous line and gaseous emboli activity in both the venous and arterial lines. The in vitro data showed that incorporation of the BB dampens fluctuations of venous line pressure by approximately 30% and decreases gaseous emboli by up to 85%. In conclusion, fluctuations of sub-atmospheric venous line pressure during kinetic-assisted drainage are related to gaseous emboli. Volume buffer capacity added to the venous line can effectively dampen pressure fluctuations resulting from abrupt changes in venous return and, therefore, can help to increase the safety of minimized cardiopulmonary bypass by reducing gaseous microemboli formation resulting from degassing.

Peri-operative cerebral microemboli in cardiac surgery are associated with post-operative neurological complications. Cardiopulmonary bypass (CPB) and perfusionist interventions are important contributors of microemboli. In this study, we examined the influence of blood sampling by the perfusionist on the appearance of microembolic signals (MES) in an open and a closed CPB system. Fourteen patients underwent isolated coronary artery bypass grafting (CABG), using either an open or closed CPB system. Patients were monitored with transcranial Doppler (TCD) for the occurrence MES in both middle cerebral arteries (MCA) as well as in the arterial and venous lines of the CPB. In the closed system, two sampling methods were used, namely the "traditional" and the "E-line". In the latter, a shunt line was applied from the manifold to the cardiotomy reservoir). In the open system, one method of blood sampling was used. Blood sampling in an open system or in a closed system using the E-line resulted in 0.2 (+/-0.56) MES, which was significantly lower than the traditional method (72 (+/-69) MES). The use of a shunt line reduces MES during blood sampling in a closed CPB system.