The intention of minimal extracorporeal circulation (MECC) is to reduce priming volume and minimize contact of blood with polymers and air in a closed system. In contrast to conventional extracorporeal circulation (ECC), a venous reservoir is missing. Thus, air trapping is limited and avoidance of bubble embolism is a major concern. This study investigates microbubbles (MBB) number and size in the venous and arterial lines of ECC and MECC compared to the number of microembolic signals (MES) in the right and left middle cerebral artery (MCA). Twenty patients undergoing coronary surgery were operated either with conventional ECC (cardiotomy reservoir, Rotaflow pump, Quadrox oxygenator, Quart filter) or MECC (Quart filter, Rotaflow pump, Quadrox oxygenator). Number and size of MBB were monitored in the venous and arterial lines with an ultrasound Doppler system. MES in right and left MCAs were measured by transcranial Doppler (TCD) monitoring. Patients undergoing MECC had additional sealing of the venous cannula by a ligature at the site of its insertion into the right atrium. There were no significant differences between groups with respect to age, X-clamping, bypass time and number of distal anastomoses. The number of MES and MBB in the arterial line was comparable between the groups. On the venous side, MECC-perfusion shows a significantly lower number of MBB. This could be explained with the additional sealing of the venous cannula. Furthermore, our data indicate that the MBB-volume reaching the pump will also appear in the arterial outflow and into the patient's MCA. For this reason, the avoidance of air contamination is a major concern for surgeons, anaesthesiologists and perfusionists.

We conclude that bileaflet mechanical valve prostheses produce HITS even in their optimum orientation. HITS following bileaflet valve replacement have an unstable nature and might be composed of nitrogen and platelets. Tilting disc valves in their optimum orientation provide almost physiological conditions with HITS measured in the same range as bioprosthesis.

Neurological complications remain an important cause of morbidity and mortality of patients following cardiopulmonary bypass (CPB). Microemboli, as well as cerebral hypoperfusion, are the main postulated mechanisms. This study demonstrates that the insertion of a dynamic bubble trap (DBT) into the curcuit reduces microbubbles in the arterial line and microembolic signals (MES) in the middle cerebral arteries (MCAs). We investigated 12 patients during coronary artery bypass grafting (CABG). The DBT was inserted between the arterial filter and the arterial cannula. For detection of microemboli before and after the DBT, a special ultrasound Doppler device was used. MES were detected by transcranial Doppler monitoring in both MCAs of the patients. Microbubbles and MES were counted during bypass. These data were compared to 12 patients who were operated in a previous period without the use of a DBT. There were no significant differences in both groups with respect to gender, age, crossclamp and bypass time and number of anastomoses. In the group without a DBT in the circuit, a mean of 6311 microbubbles per operation could be observed distal to the arterial filter, corresponding to 282 MES. After inclusion of a DBT, we could register, in the second group, 8496 microemboli proximal and 2915 distal of the DBT, corresponding to 89 MES per operation. The reduction rate of microbubbles in the tubing was 65.7%, corresponding to a reduction in MES of about 86.2%. We conclude that the insertion of a DBT in the arterial line of CPB circuit protects the cerebrovascular system from microembolic events, as demonstrated by lower MES counts.

Microemboli during extracorporeal circulation (ECC) might be a reason for postoperative neuropsychological dysfunction. This case report shows that reduction of microbubbles in the arterial line, as well as high intensity transient signals (HITS) in the middle cerebral artery (MCA), could be accomplished by use of a dynamic bubble trap (DBT) during routine coronary artery bypass graft (CABG) surgery in a 63-year-old male. The DBT was placed after the arterial filter, an ultrasound Doppler device was used for detection of microemboli before and after the DBT. HITS were measured by a transcranial ultrasound Doppler in both MCAs. For first 32 min of ECC, the DBTwas excluded; 54 916 microbubbles and 507 HITS were counted. In the next 30 min, blood flow was directed through the DBT. This led to a significant reduction of microbubbles from 55 888 to 18 237; accordingly, only 120 HITS were registered. A DBT, integrated in ECC for routine CABG, effectively reduces air bubbles, thus protecting the cerebrovascular system from microembolization, as demonstrated by lower HITS counts.

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