Evaluation of Hemodynamic and Regional Tissue Perfusion Effects of Minimized Extracorporeal Circulation (MECC

The introduction of extracorporeal circulation has facilitated open-heart surgery. The development of modern techniques in extracorporeal circulation (ECC) is the result of the combined efforts of physiologists, physicians, and engineers. During the second half of the 20th century, scientists refined their methods in the development of extracorporeal circulation (new oxygenators [membrane], pumps [centrifugal], and modified surfaces [coatings] were introduced) so that it could be used in humans (1). All these improvements and new developments had only one aim: to reduce the observed deleterious effects of extracorporeal circulation (2). At the end of the 1990s many practitioners and scientists devised a new kind of ECC system in which the surface area and priming amount of the tubes was reduced to reduce the deleterious and hemodilutional effects of extracorporeal circulation. These circuits are better known as minimal extracorporeal circulation. The idea was to have one system with all observed advantages. The first commercial mini-system was the CorX® System from Cardiovention®, (Santa Clara, CA). This system included an integrated centrifugal pump-polypropylene oxygenator, a complete heparin-coated surface, and a low priming volume (3). The minimized extracorporeal circulation system (MECC®, Maquet) was introduced almost at the same time (1999). MECC® has been conducted to evaluate its effectiveness for extracorporeal support during coronary bypass grafting (CABG) and valve replacement surgery. Findings include a reduction in the use of blood products and a reduction in serum markers of inflammation in comparison to conventional cardiopulmonary bypass (4–7). The literature shows a lot of injuries and side effects from extracorporeal circulation on the major organ systems, especially to the cerebrum and abdominal organs like the kidneys. Efforts to find clear correlations between organ impairment and ECC or the superiority of off pump coronary aortic bypass surgery over conventional cardiopulmonary bypass (CCPB) surgery was not significant in terms of neurological declines and renal injury (8–11). The main factors in terms of impairment to renal and cerebral function in correlation regarding the ECC systems are embolism (cerebral) followed by hypoperfusion (renal + cerebral) (12). Regarding the ECC systems per se left heart venting (13) (cerebral injury) and the duration of CPB (13–15) seems to be more relevant. But also a higher consumption of vasopressor was referred with an increased organ injury (16,17). Wiesenack et al. recently showed in a retrospective analysis of 970 patients (485 MECC vs. 485 CCPB) that, despite a reduced preoperative cardiac index, the mean arterial pressure (MAP) among MECC patients was significantly higher compared to CCPB. Patients in the MECC group received less frequent neosynephrine (318 (65%) vs. 429 (88%)) (4). In our experience over the last 3 years, the maintaining of ECC with MECC is linked to a higher mean arterial pressure and lower consumption of norepinephrine (mean μg norepinephrine per MECC and CCPB: 16.2 ± 27.1 vs. 91.4 ± 174.9 (patient database, Heart Center Coswig). In this study we want to examine this observation and whether it has any influence on regional tissue perfusion in patients who received a coronary arterial bypass surgery treated with MECC compared to those treated with CCPB. Secondary endpoints were the transfusion rate and the course of hematocrit and intracorporeal volume status perioperatively.