Adrian Bauer

Minimal extracorporeal circulation and off-pump compared to conventional cardiopulmonary bypass in coronary surgery☆

OBJECTIVES Although minimal extracorporeal circulation (MECC) and off-pump surgery are equal or better alternatives to conventional cardiopulmonary bypass (CCPB) regarding perioperative morbidity, use of blood and blood products and completeness of revascularization, CCPB is still being used in the majority of coronary artery bypass grafting (CABG) operations. METHODS AND RESULTS We investigated 1472 CABG operations in our center. A total of 1143 CABG operations were performed using CCPB, 220 using MECC and 109 were performed as off-pump coronary artery bypass (OPCAB). All patients were recorded prospectively. Perioperative follow-up was focused on the occurrence of arrhythmia, neurocognitive disorders and the need of blood and blood products. Operative mortality rates were comparable in all three groups. The mean number of distal anastomoses was 3.2+/-0.6 in the MECC group, 3.4+/-0.7 in the CCPB group and 1.9+/-0.8 in the OPCAB group (P=0.01). Arrhythmia occurred in 25% of the MECC group and in 35.6% of the CCPB group (P=0.05). Arrhythmia occurred in 21.7% of the OPCAB group. Seven patients (3%) of the MECC group suffered neurocognitive disorders perioperatively compared to 74 (7%) patients of the CCPB group (P=0.05) and three patients of the OPCAB group (3%). The median number of blood transfusions per patient was 0.8 in the MECC group, 1.8 in the CCPB group and 0.8 in the OPCAB group (P<0.0001). CONCLUSIONS Perioperative morbidity of MECC and OPCAB is comparable to or even less in comparison to CCPB. MECC allows CABG surgery in cardiac arrest so that completeness of revascularization is being warranted and longer patency rates can be guaranteed. Furthermore, the use of blood and blood products is significantly less in MECC surgery so that MECC should be considered first choice in CABG surgery over CCPB and OPCAB.

Use of minimal invasive extracorporeal circulation in cardiac surgery: principles, definitions and potential benefits. A position paper from the Minimal invasive Extra-Corporeal Technologies international Society (MiECTiS)

Minimal invasive extracorporeal circulation (MiECC) systems have initiated important efforts within science and technology to further improve the biocompatibility of cardiopulmonary bypass components to minimize the adverse effects and improve end-organ protection. The Minimal invasive Extra-Corporeal Technologies international Society was founded to create an international forum for the exchange of ideas on clinical application and research of minimal invasive extracorporeal circulation technology. The present work is a consensus document developed to standardize the terminology and the definition of minimal invasive extracorporeal circulation technology as well as to provide recommendations for the clinical practice. The goal of this manuscript is to promote the use of MiECC systems into clinical practice as a multidisciplinary strategy involving cardiac surgeons, anaesthesiologists and perfusionists.

Minimal invasive Extra-Corporeal Circulation (MiECC): a revolutionary evolution in perfusion

Since the beginning of extracorporeal circulation (ECC) in cardiac surgery, a multitude of changes and improvements were aimed to reduce the adverse systemic effects caused by the artificial surfaces of the perfusion circuit. The clinical picture is similar to a systemic inflammatory response syndrome [1]. The magnitude of the inflammatory response adversely influences clinical outcomes [2]. Hence, the overall morbidity associated with cardiac surgery is substantial [3]. The off-pump coronary artery bypass (OPCAB) technique was introduced as a strategy to decrease the side effects of cardiopulmonary bypass (CPB). But the real advantages of OPCAB have been questioned in recent years [4]. In the early 2000s, a simplified perfusion system comprising all technological advancements was designed [5]. The modifications of the new system were much more revolutionary than the individual improvements to the existing conventional CPB circuits. The idea was to create a system including all established benefits in one CPB set-up. The Minimal Extra-Corporeal Circulation (MiECC) technology was born. Since then, MiECC systems have been developed to increase the technical ease of on-pump surgery while tempering its disadvantages. For many years, cardiac surgeons, anaesthesiologists and perfusionists considered MiECC systems as a miniaturization or simplification of traditional CPB only. MiECC significantly attenuated morbidity attributed to conventional ECC, as for beatingheart procedures, while permitting optimal technical surgical conditions [6]. ‘The authors believe that MiECC technology represents more than a miniaturization process: it is a major step forward and a totally new philosophy to be integrated in contemporary cardiac surgery’. The idea of MiECC systems has initiated new efforts to improve the biocompatibility of CPB systems and minimize their side effects, offering finally better postoperative end-organ function. Characteristics of MiECC include the following: (1) a blood pump with optimal biocompatibility, low thrombogenicity, minimal haemolysis and activation of leucocytes as well as proinflammtory mediators; (2) a minimal tubing length to reduce the priming volume required and thus minimize haemodilution, decreasing the need for foreign blood transfusions; (3) coated surfaces to reduce protein adsorption and platelet activation; (4) separation of shed blood and exclusion of activated blood components via cell salvage; (5) closed system to avoid blood–air contact; (6) temperature management depending on the need and magnitude of surgery should be possible; (7) use of modern concepts of myocardial protection, like blood cardioplegia, must be easy to integrate; (8) safe de-airing must be possible following open heart procedures; (9) finally, it should help modern concepts of fast-track anaesthesia [7, 8]. These characteristics will help to make MiECC an element of a minimal invasive procedure rather than simply a miniaturized CPB system. Numerous randomized clinical studies have proved that MiECC exerts significant beneficial effects on postoperative morbidity, by reducing haemodilution, mediastinal bleeding, need for blood transfusion and inflammatory response. Clinical benefits are: improved end-organ (myocardial, renal and cerebral) protection and reduction of the length of intensive care unit stay [5–8]. Moreover, it is associated with a significant survival benefit in coronary procedures compared with conventional ECC as shown in a recent meta-analysis. This analysis reported randomized trials including 24 studies with a total of 2770 patients [9] and provided a Scientific Class I, Level of evidence A for implementation of MiECC, at least for coronary revascularization. Despite these clear clinical advantages, penetration of the MiECC technology into clinical practice remains significantly low. Thus, the authors took the initiative to organize the ‘1st International Symposium on Minimal invasive Extracorporeal Circulation Technologies (1st MiECT)’ in Thessaloniki, Greece during June 13–14 to create a dedicated international forum to stimulate the exchange of ideas in clinical application and research in the field of Minimal invasive Extracorporeal Circulation Technology without geographical bias (www.miect.org). More than 400 participants from all continents registered. Beside scientific sessions, wet-labs with two simulators for ‘hands-on training’ allowed participants to practice on all commercially available MiECC systems. Twenty abstracts were selected for publication and are part of this Interactive Cardiovascular and Thoracic Surgery issue. During the congress, the ‘Minimal invasive Feedback from the 1st International Symposium on Minimal invasive Extracorporeal Circulation Technologies, Thessaloniki, Greece, 13–14 June 2014.

Reduced amount of gaseous microemboli in the arterial line of minimized extracorporeal circulation systems compared with conventional extracorporeal circulation

We would like to refer to the recently published article by Aboud et al. [1] regarding negative venous line pressures and increased arterial air bubble count during minimized extracorporeal circulation (MECC). We think that there are several flaws in this paper. Recent studies have mainly focussed on gaseous microemboli (GME). Approaches are manifold, using arterial line filters, or additionally, venous bubble traps (VBTs) [2]. Roosenhoff et al. [3] showed a significant reduction of GMEs after the VBT. Kutschka et al. [4] showed a nearly complete reduction of GME post-arterial line filter. Perthel et al. [5] proved the relationship between reduced GME in the arterial line of MECC and a decreased emboli rate, demonstrated by transcranial ultrasound. In clinical terms, Anastasiadis et al. [6] proved that patients operated on MECC showed a clearly better postoperative neurocognitive course. After implementation of VBTs, our study group in Coswig focused on venous suction and took several measures: a small triple-stage venous cannula and use of a double purse-string suture to firmly fix the cannula. Furthermore, since 2007, in Coswig, we have been using a controlled negative-pressure approach. This, translated into clinical practice, means a continuous measuring of venous suction pressure with integrated regulation of arterial flow. There is also an ongoing study in Coswig focusing on GME regarding MECC vs conventional extracorporeal circulation. Moreover, the authors focused on one type of the MECC system. In fact, there are several different oxygenators that handle microbubbles in a different way. In the present study, the authors chose the worst possible combination, components which should most probably not be used for MECC perfusion. Most modern oxygenators have integrated bubble traps (Affinity Fusion) or an integrated arterial filter (Capiox FX). The best available MECC circuit may integrate these components, because they demonstrate practically no GME activity even at higher negative pressures. In general, every modern MECC circuit is negative pressure limited in terms of the operator being able to determine the maximal negative pressure— which is certainly never as high as −150 mmHg. Finally, MECC perfusions are always performed with a minimal positive right atrial pressure. However, the smaller the pump, the more negative will be the pressure. In the present study, the authors used the smallest available pump. In any case, in the era of the modern MECC systems and the routine use of real-time control of negative pressure to the venous line and VBT to all systems, we think that this paper is out-of-date. Moreover, the advice for further refinements of the systems to avoid adverse effects from increased arterial air bubbles is a rather misleading conclusion and may not refer to the systems, which are used in contemporary clinical practice. In summary, we would like to point out that despite the notable effort that the authors have made, the long-time interval between implementing their study and publishing their results suggests that advances in MECC technology and technique did not find enough consideration in the study design, and hence, we have to consider the entire work as not state-of-the-art.

2017 EACTS/EACTA Guidelines on patient blood management for adult cardiac surgery

Authors/Task Force Members: Christa Boer (EACTA Chairperson)(Netherlands), Michael I. Meesters (Netherlands), Milan Milojevic (Netherlands), Umberto Benedetto (UK), Daniel Bolliger (Switzerland), Christian von Heymann (Germany), Anders Jeppsson (Sweden), Andreas Koster (Germany), Ruben L. Osnabrugge (Netherlands), Marco Ranucci (Italy), Hanne Berg Ravn (Denmark), Alexander B.A. Vonk (Netherlands), Alexander Wahba (Norway), Domenico Pagano (EACTS Chairperson)(UK),. Document Reviewers: Moritz W.V. Wyler von Ballmoos (USA), Mate Petricevic (Croatia), Arie Pieter Kappetein (Netherlands), Miguel Sousa-Uva (Portugal), Georg Trummer (Germany), Peter M. Rosseel (Netherlands), Michael Sander (Germany), Pascal Colson (France), Adrian Bauer (Germany).

Minimal invasive extracorporeal circulation should become the standard practice in coronary revascularization surgery

We read with great interest the large-scale network meta-analysis by Kowalewski et al. comparing clinical outcomes of patients undergoing coronary artery bypass grafting (CABG) operated on using minimal invasive extracorporeal circulation (MiECC) or off-pump (OPCAB) with those undergoing surgery on conventional cardiopulmonary bypass (CPB) [1]. The authors actually integrated into single study two recently published meta-analysis comparing MiECC and OPCAB with conventional CPB, respectively [2, 3] into a single study. According to the results of this study, MiECC and OPCAB are both strongly associated with improved perioperative outcomes following CABG when compared with CABG performed on conventional CPB. The authors conclude that MiECC may represent an attractive compromise between OPCAB and conventional CPB. After carefully reading the whole manuscript, it becomes evident that the role of MiECC is clearly undervalued. Detailed statistical analysis using the surface under the cumulative ranking probabilities indicated that MiECC represented the safer and more effective intervention regarding all-cause mortality and protection from myocardial infarction, cerebral stroke, postoperative atrial fibrillation and renal dysfunction when compared with OPCAB. Even though no significant statistical differences were demonstrated between MiECC and OPCAB, the superiority of MiECC is obvious by the hierarchy of treatments in the probability analysis, which ranked MiECC as the first treatment followed by OPCAB and conventional CPB. Thus, MiECC does not represent a compromise between OPCAB and conventional CPB, but an attractive dominant technique in CABG surgery. These results are consistent with the largest published meta-analysis by Anastasiadis et al. comparing MiECC versus conventional CPB including a total of 2770 patients. A significant decrease in mortality was observed when MiECC was used, which was also associated with reduced risk of postoperative myocardial infarction and neurological events [4]. Similarly, another recent meta-analysis by Benedetto et al. compared MiECC versus OPCAB and resulted in comparable outcomes between these two surgical techniques [5]. As stated in the text, superiority of MiECC observed in the current network meta-analysis, when compared with OPCAB, could be attributed to the fact that MiECC offers the potential for complete revascularization, whereas OPCAB poses a challenge for unexperienced surgeons; especially when distal marginal branches on the lateral and/or posterior wall of the heart need revascularization. This is reflected by a significantly lower number of distal anastomoses performed in OPCAB when compared with conventional CPB. Therefore, taking into consideration the literature published up to date, including the results of the current article, we advocate that MiECC should be integrated in the clinical practice guidelines as a state-of-the-art technique and become a standard practice for perfusion in coronary revascularization surgery.

A retrospective comparative study of minimally invasive extracorporeal circulation versus conventional extracorporeal circulation in emergency coronary artery bypass surgery patients: a single surgeon analysis

OBJECTIVES At the moment, the main application of minimally invasive extracorporeal circulation (MiECC) is reserved for elective cardiac operations such as coronary artery bypass grafting (CABG) and/or aortic valve replacement. The purpose of this study was to compare the outcome of emergency CABG operations using either MiECC or conventional extracorporeal circulation (CECC) in patients requiring emergency CABG with regard to the perioperative course and the occurrence of major adverse cardiac and cerebral events (MACCE). METHODS We analysed the emergency CABG operations performed by a single surgeon, between January 2007 and July 2013, in order to exclude the differences in surgical technique. During this period, 187 emergency CABG patients (113 MiECC vs 74 CECC) were investigated retrospectively with respect to the following parameters: in-hospital mortality, MACCE, postoperative hospital stay and perioperative transfusion rate. RESULTS The mean logistic European System for Cardiac Operative Risk Evaluation was higher in the CECC group (MiECC 12.1 ± 16 vs CECC 15.0 ± 20.8, P = 0.15) and the number of bypass grafts per patient was similar in both groups (MiECC 2.94 vs CECC 2.93). There was no significant difference in the postoperative hospital stay or in major postoperative complications. The in-hospital mortality was higher in the CECC group 6.8% versus MiECC 4.4% (P = 0.48). The perioperative transfusion rate was lower with MiECC compared with CECC (MiECC 2.6 ± 3.2 vs CECC 3.8 ± 4.2, P = 0.025 units of blood per patient). CONCLUSIONS In our opinion, the use of MiECC in urgent CABG procedures is safe, feasible and shows no disadvantages compared with the use of CECC. Emergency operations using the MiECC system showed a significantly lower blood transfusion rate and better results concerning the unadjusted in-hospital mortality.

Shed-blood-separation and cell-saver: an integral Part of MiECC? Shed-blood-separation and its influence on the perioperative inflammatory response during coronary revascularization with minimal invasive extracorporeal circulation systems – a randomized controlled trial

Objective: The postoperative systemic inflammatory response after cardiopulmonary bypass (CPB) is still an undesirable side-effect after cardiac surgery. It is most likely caused by blood contact with foreign surfaces and by the surgical trauma itself. However, the recirculation of activated shed mediastinal blood is another main cause of blood cell activation and cytokine release. Minimal invasive extracorporeal circulation (MiECC) comprises a completely closed circuit, coated surfaces and the separation of suction blood. We hypothesized that MiECC, with separated cell saved blood, would induce less of a systemic inflammatory response than MiECC with no cell-saver. The aim of this study was, therefore, to investigate the impact of cell washing shed blood from the operating field versus direct return to the ECC on the biomarkers for systemic inflammation. Material and methods: In the study, patients with MiECC and cell-saver were compared with the control group, patients with MiECC and direct re-transfusion of the drawn blood shed from the surgical field. Results: High amounts of TNF-α (+ 120% compared to serum blood) were found in the shed blood itself, but a significant reduction was demonstrated with the use of a cell-saver (TNF-α ng/l post-ECC 10 min: 9.5±3.5 vs. 19.7±14.5, p<0.0001). The values for procalcitonin were not significantly increased in the control group (6h: 1.07±3.4 vs. 2.15±9.55, p=0.19) and lower for C-reactive protein (CRP) (24h: 147.1±64.0 vs.134.4±52.4 p=0.28). Conclusion: The use of a cell-saver and the processing of shed blood as an integral part of MiECC significantly reduces the systemic cytokine load. We, therefore, recommend the integration of cell-saving devices in MiECC to reduce the perioperative inflammatory response.

Recommendations for extracorporeal cardiopulmonary resuscitation (eCPR): consensus statement of DGIIN, DGK, DGTHG, DGfK, DGNI, DGAI, DIVI and GRC

Extracorporeal cardiopulmonary resuscitation (eCPR) may be considered as a rescue attempt for highly selected patients with refractory cardiac arrest and potentially reversible aetiology. Currently, there are no randomised, controlled studies on eCPR. Thus, prospective validated predictors of benefit and outcome are lacking. Currently, selection criteria and procedure techniques differ across hospitals and standardised algorithms are lacking. Based on expert opinion, the present consensus statement provides a first standardised treatment algorithm for eCPR.

Is 300 Seconds ACT Safe and Efficient during MiECC Procedures

Introduction The recommended minimum activated clotting time (ACT) level for cardiopulmonary bypass (CPB) of 480 seconds originated from investigations with bubble oxygenators and uncoated extracorporeal circulation (ECC) systems. Modern minimal invasive ECC (MiECC) systems are completely closed circuits containing a membrane oxygenator and a tip‐to‐tip surface coating. We hypothesized that surface coating and the “closed‐loop” design allow the MiECC to safely run with lower ACT levels and that an ACT level of 300 seconds can be safely applied without thromboembolic complications. The aim of this study was to investigate the potential risks during application of reduced heparin levels in patients undergoing coronary surgery. Methods In this study, 68 patients undergoing coronary artery bypass grafting with MiECC were randomized to either the study group with an ACT target of 300 seconds or the control group with an ACT of 450 seconds. All other factors of MiECC remained unchanged. Results The study group received significantly less heparin and protamine (heparin [international units] median [min‐max], Red_AC: 32,800 [23,000‐51,500] vs. Full_AC: 50,000 [35,000‐65,000] p < 0.001; protamine [international units], Red_AC: 18,000 [10,000‐35,000] vs. Full_AC: 30,000 [20,000‐45,000] p < 0.001). The ACT in the study group was significantly lower at the start of MiECC (mean ± standard deviation: study group 400 ± 112 vs. control group 633 ± 177; p < 0.0001). Before termination of CPB the ACT levels were: study group 344 ± 60 versus control group 506 ± 80. In both groups, the values of the endogenous thrombin potential (ETP) decreased simultaneously. None of the study participants experienced thromboembolic complications. Conclusion Since no evidence of increased thrombin formation (ETP) was found from a laboratory standpoint, we concluded that the use of MiECC with a reduced anticoagulation strategy seems possible. This alternative anticoagulation strategy leads to significant reduction in dosages of both heparin and protamine. We can confidently move forward with investigating this anticoagulation concept. However, to establish clinical safety of ACT below 300 seconds, we need larger clinical studies.