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Ann Thorac Surg 2004;77:2172-2175
© 2004 The Society of Thoracic Surgeons
a Cardiovascular Surgery Unit, Amiens, France
b Anesthesiology Department, South Hospital, Amiens, France
Accepted for publication May 20, 2003.
* Address reprint requests to Dr Remadi, Centre Hopitalier Universitaire D'Amiens, Service de Chirurgie Cardique, Groupe Hopitalier Sud, Amiens Cedex 1 80054, France.
e-mail: jpremadi{at}aol.com
Abstract
PURPOSE: We studied a cohort of 150 patients operated on with a new cardiopulmonary bypass (CPB) system. This is the mini-extracorporeal circulation (MECC) system.
DESCRIPTION: The MECC is a fully heparin coated closed-loop CPB system that includes a centrifugal pump and has a priming volume of 450 mL. Between March 2001 and September 2002, 150 consecutive patients were operated on using the mini-CPB (MECC) method. This includes 105 coronary artery bypass graft and 45 aortic valve replacement patients. The median age was 66.7 ± 10.7 years with a gender ratio of 3.27 males to 1 female.
EVALUATION: The 30-day operative mortality was 1.3%. The hemoglobin concentration was stable and perioperative transfusion was needed in only 6% of all patients. The renal and neuropsychiatric complications were less than 1%.
CONCLUSIONS: In our experience, the MECC system is a reliable new concept for CPB with good clinical results.
Following the development of the first cardiopulmonary bypass (CPB) machines at the end of the 1950s [1] there have been many improvements in pump-oxygenator circuits. One example is the development of the membrane oxygenator that replaced the bubble oxygenator [2]. Another example is the progressive reduction of priming volume. These were notable improvements that resulted in substantial clinical progress.
Throughout the 1990s, pump-oxygenator circuits and cardioplegia techniques plateaued [3]. Despite all of these prior improvements, the adverse effects of CPB (eg, inflammatory response; and renal, pulmonary, and neurologic dysfunction) remained important problems even though the outcomes have improved [4, 5]. The adverse effects of CPB led, in part, to the development of off-pump coronary artery bypass grafting (CABG) techniques.
The limitations of off-pump CABG result primarily from hemodynamic instability that occurs as a result of cardiac displacement. This problem has stimulated the development of novel devices that provide temporary support for the circulation with fewer adverse affects than conventional pump-oxygenator circuits. The mini-CPB or mini-extracorporeal circulation system (MECC; Jostra AG, Hirrlingen, Germany) is one such novel device. The purpose of the present study is to describe our results using the MECC system for cardiac operations in 150 patients. These operations included CABG and aortic valve replacement (AVR).
Description
The MECC system
The MECC circuit is a fully heparinized closed-loop CPB system (Figs. 1 and 2).
A 150 U/kg dose of intravenous heparin is required for use of this system.
The MECC circuit is constructed as follows.
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Centrifugal pump
Zones of stagnant blood and hemolysis are minimized by the design of this pump (Rotaflow; Jostra AG, Hirrlingen, Germany). The priming volume is 32 mL and the surface area is 0.019 m2. An integral flow measurement system determines output from the pump outlet. The flow capacity is greater than 9 L/min.
Arterial filter
The arterial filter includes an innovative three-phase deairing design. The surface area of the filter is 0.057 m2 and the priming volume is 180 mL. In the present series the arterial filter was not used in order to minimize the priming volume, however this arterial filter is available for clinical use.
Heparin coating
Tubing for the pump-oxygenator (Bioline; Jostra AG, Hirrlingen, Germany) is treated with a proprietary heparin coating that provides biocompatibility with protection of all blood components. The tubing length is less than 100 cm. Therefore, the pump must be placed near the patient's head. The blood-foreign surface contact area and the hemodilution resulting from use of this pump are relatively small due to the total priming volume of 450 mL. Of note, the system does not have a venous cardiotomy suction device. In-line blood gas measurements and saturation monitoring are incorporated in the device.
In 2002 a suction system was added to the MECC circuit. Using this added device two suctions can be used simultaneously at the operating table. This addition should be considered a "semiclosed" system because a vent may also implanted in the ascending aorta (for CABG surgery) or in the pulmonary artery (for AVR). The blood from this vent is reinjected into the pump inflow (Fig 2). The absence of a cardiotomy reservoir limits the artificial surface-blood contact that occurs secondary to aspiration of blood. In the present study, blood in the pericardial space was aspirated and treated with an erythrocyte-scavenging device before reinfusion. The flow capacity of the pump is directly related to the blood volume of the patient, therefore blood volume must be carefully monitored and maintained by the entire team of physicians caring for the patient throughout the procedure (eg, anesthesiologists, surgeons, nurses, and perfusionists among others).
Evaluation
Between March 2001 and September 2002 we studied 150 consecutive patients who underwent CABG or AVR. All patients were operated on with the MECC system. The only patients that were excluded were those with renal insufficiency (creatinine > 1.2 mg/dL). The mean age of the MECC patients was 66.7 ± 10.7 years and the gender ratio was 3.27 males to 1 female. The patients included 105 CABG and 45 AVR patients. The AVR patients included 11 AVR/CABG procedures. The mean preoperative left ventricular ejection fraction was 56% ± 5% (Table 1). For the initial 40 CABG patients a closed MECC system was used. Subsequently, a suction system that permitted AVR was added to the circuit. Cannulation for MECC is comparable to conventional CPB. A double venous purse string was used in order to ensure an airtight seal at the right atrial level. The MECC was positioned closer to the operative field than a conventional pump-oxygenator circuit. In these patients full dose heparin (3 mg/kg intravenously) was given to maintain the ACT above 400 seconds. With a heparin-coated circuit, a dose of 1.5 mg/kg would have been sufficient. At the end of the procedure heparin was fully reversed with protamine. Myocardial protection consisted of high potassium warm cardioplegia solution, so there was no need to cool the blood. Following introduction of the suction system, aortic venting has been used with CABG procedures. A pulmonary artery vent has been used for AVR.
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Adverse device-related events
On three occasions air that entered the pump inflow resulted in bubbles that were noted in the oxygenator. This air never passed through to the oxygenator outflow and, therefore, never caused any harmful effects. In each case air entered the pump due to surgical problems. These included right atrial purse string failure and entrainment of air from small holes in the right atrium that were created during reoperative surgery. As a result we no longer perform reoperative procedures using the MECC system. There were four reoperations in this series.
Comment
Since the early 1990s, the risk factors for patients having cardiac operations have progressively increased. As a consequence, improvements in the surgical, anesthetic, and CPB techniques have become ever more important to achieving satisfactory postoperative outcomes [6]. The deleterious effects of CPB are well documented [4, 5, 7], but at the same time CPB offers perhaps the best technical conditions for surgery. Off-pump CABG has been proposed as an alternative to CPB for CABG. The preliminary reports describing off-pump CABG exhibited a similar mortality and morbidity rate to CABG using CPB [8]. However, off-pump CABG has somewhat less favorable technical conditions for surgery. As a result, questions persist regarding long-term graft patency in patients who have off-pump CABG. MECC represents the combination of two techniques that may decrease the deleterious effects of CPB. The inflammatory response associated with CPB is likely reduced [9] due to decreased hemodilution and limited air-blood contact [9, 10]. The decrease of S1B1100 production during MECC, compared with conventional CPB, may decrease the incidence of neurologic complications associated with MECC [9]. One major advantage of MECC is its capacity to function as a closed system.
This study has demonstrated that postoperative morbidity and mortality were very low in this group of patients. A prospective clinical trial that compares conventional CPB with MECC is necessary to define the impact of MECC. Using the MECC as a semiclosed system with aortic or pulmonary artery suction permitted the extension of the MECC system to AVR. However, the vent catheter is placed in the pulmonary artery rather than the left ventricle. This position limits the aspiration of air.
Our principal finding from using MECC was a more stable hemoglobin level, which may explain the lower intraoperative transfusion requirements in our patients. For surgeons, anesthesiologists, and especially perfusionists, there is a learning curve for this technique. The anesthesiologist must keep a close watch on the vascular tone of the patient in order to obtain optimal performance of the pump. The absence of a venous reservoir, the use of a centrifugal pump with negative venous pressure, and the absence of security lent by conventional CPB may make perfusionists reticent to use this technique.
In our series we encountered three incidents of air entering the venous cannula and passing into the oxygenator. Future improvements in the MECC system will eliminate this problem. Improved hemodynamic stability will also help anesthetic management. However, because the patient is the venous reservoir for the system, tight control of vascular tone will remain important.
In conclusion, the use of a semiclosed MECC system provides a comfort level similar to standard CPB for CABG and AVR. The MECC is also a good circulatory support device for performing CABG on a beating heart in difficult patients.
Disclosures and freedom of investigation
The Jostra MECC system was purchased by The South Hospital of Amiens (Amiens, France). The authors have performed a free and independent evaluation of this new technology. Dr Remadi and coauthors have no financial relationship with Jostra.
Acknowledgments
The authors thank William L. Holman, MD, for his assistance with language editing.
Footnotes
The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
References
This article has been cited by other articles:
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  L. K. Ti, B.-L. Goh, P.-S. Wong, P. Ong, S.-G. Goh, and C.-N. Lee Comparison of Mini-Cardiopulmonary Bypass System With Air-Purge Device to Conventional Bypass System Ann. Thorac. Surg., March 1, 2008; 85(3): 994 - 1000. [Abstract] [Full Text] [PDF]
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J.-P. Remadi Invited Commentary Ann. Thorac. Surg., March 1, 2008; 85(3): 1000 - 1001. [Full Text] [PDF]
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R. A.J.M. Huybregts, A. M. Morariu, G. Rakhorst, S. R. Spiegelenberg, H. W.A. Romijn, R. de Vroege, and W. van Oeveren Attenuated Renal and Intestinal Injury After Use of a Mini-Cardiopulmonary Bypass System Ann. Thorac. Surg., May 1, 2007; 83(5): 1760 - 1766. [Abstract] [Full Text] [PDF]
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C. Beghi, F. Nicolini, A. Agostinelli, B. Borrello, A. M. Budillon, F. Bacciottini, M. Friggeri, A. Costa, L. Belli, L. Battistelli, et al. Mini-Cardiopulmonary Bypass System: Results of a Prospective Randomized Study Ann. Thorac. Surg., April 1, 2006; 81(4): 1396 - 1400. [Abstract] [Full Text] [PDF]
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U. Abdel-Rahman, F. Ozaslan, P. S. Risteski, S. Martens, A. Moritz, A. Al Daraghmeh, H. Keller, and G. Wimmer-Greinecker Initial Experience With a Minimized Extracorporeal Bypass System: Is There a Clinical Benefit? Ann. Thorac. Surg., July 1, 2005; 80(1): 238 - 243. [Abstract] [Full Text] [PDF]
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W J van Boven, W B Gerritsen, F G Waanders, F J Haas, and L P Aarts Mini extracorporeal circuit for coronary artery bypass grafting: initial clinical and biochemical results: A comparison with conventional and off-pump coronary artery bypass grafts concerning global oxidative stress and alveolar function Perfusion, July 1, 2004; 19(4): 239 - 246. [Abstract] [PDF]
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