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Eur J Cardiothorac Surg 2004;26:S82-S85
© 2004 Elsevier Science NL
Working Group Report |
Department of Cardio-thoracic Surgery, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, D-93042 Regensburg, Germany
* Corresponding author. Tel.: +49-941-9449801; fax: +49-941-9449802. (Email: htc{at}klinik.uni-regensburg.de).
Abstract
Tradition and experience of cardiopulmonary bypass in the hand of cardiac surgeons led to several spin-offs of this extracorporeal technique. Acute organ support is realized for situations of failing cardiac output, circulatory arrest respectively, of pulmonary failure and of drowning. Extracorporeal circulation is a promising adjunct to aim in better surgical technique and treatment in neurosurgery, thoracic aortic surgery, complex lung resection, tumor surgery and procedures where safe organ perfusion must be ascertained. Chemotherapy and hyperthermia in limb carcinoma is highly successful if performed with the help of extracorporeal circulation. Progression in transcutaneous cannulation technique makes application of machinery easy and from operation facilities independent. Replacement of long lasting periods of chest compression for heart massage is a future perspective if circulation is maintained by transcutaneously adapted miniaturized heart–lung-machine. Long lasting traumatizing mechanical ventilation of a severely diseased lung maybe replaced by extracorporeal lung assistance to give better chances for the lung to recover. Thoughts for these new interdisciplinary duties of cardio surgical units were discussed in the committee for the Symposium for the Future of Cardiac Surgery.
Key Words: Extracorporeal circulation • Cardiopulmonary bypass • Extracorporeal lung assist • Percutaneous technique for cannulation • Acute heart failure • Acute lung failure • Perfusionist
1. Introduction
Extra corporeal circulation (ECC) is by it's original meaning a supportive tool for insufficient functions of organs in a variety of applications. This technology contributed to the major progress steps in medicine during the last five decades. Classical medical disciplines adopted all kinds of these methods with the help of engineers and industry and guided them to continuous development. One of the first major and highly effective paths of this development came from dialysis. The development was strictly linked to nephrology and dialysis centers respectively for its specificity. Therefore this technology remained rather isolated.
Despite of technical knowledge and experience in renal supportive devices was oriented in a low blood flow manner. This did influence the development of high flow systems cardiac surgeons became interested in. Cardiopulmonary bypass (CPB) was for decades the most important tool, without of it the success of cardiac surgery would not have been occurred.
This success was accompanied by
Applications for extra cardiac reasons are important spin-offs of these parameters of success in cardiac surgery. They allowed new perspectives to support or replace passagerly particular organ functions or to deliver support by means of extra corporeal high volume transported blood.
New future perspectives need absolutely to be based on facts, the awareness of them are often neglected in order to guide to a proper and fruitful goal. These facts need explanations before suggesting future directions.
2. Status and perspectives
The essential components of a cardiopulmonary bypass are pump, oxygenator and heat exchanger. The physiological capability of them gave logically rise to possibilities for replacement of failing organ systems. The cardiac surgeon as the expert of this multicomponent tool was always initiator to apply derivatives of a heart lung machine to the need for replacement of organ functions.
2.1 Support for circulation
Most common is the replacement of a failing or arrested blood circulation. Extra corporeal pump systems have been applied with a perspective for several days to weeks in situations of acute low cardiac output failure, e.g. due to myocardial infarction. These pump systems are simplified heart lung machines. For continuous technical improvement they reveal today a high level of safety. Most recent versions are named minimal extra corporeal circulation (MECC) applicable to those cases in heart surgery not readily be performed by off-pump technique. MECC-system is less expensive, supports circulation in full if cardiac output is compromised and is absolutely save in the hands of the trained and experienced person. MECC-system in different versions still always containing pump, oxygenator and heat exchanger is applicable by percutaneous technique with appropriate cannula in arterial and venous femoral vessels allowing its ambulatory use. Within few minutes it is installed and every day fulltime available [8]. The ease of application and handling may allow wide spread handling of all medical disciplines, in catheter laboratories, emergency rooms, X-ray departments, even airports and by ambulatory resuscitation teams. Chronic left and/or right ventricular failure with uncertainty of availability for organ replacement and for organ recovery can be handled by a transcutaneous MECC-system if the clinical situation demands for and until the decision for a definitive and mostly expensive implantable device has been made [5].
2.2 Support for ventilation
Under a running cardiopulmonary bypass the lung function is completely replaced. In analogy to the circulatory support this led to the oxygenator's application for acute pulmonary failure. In the past ECMO has sporadically applied in these situations with some experience in distinct centers, however results were not convincing enough that over the years it became a standardized procedure except for its use in children. The technique of ECMO in adult is more or less pre-occupied with a negative option. The term ECMO (extra corporeal membrane oxygenation) is obsolete, for membrane oxygenators do not have an alternative today. Technical perfection, simplification and thereby exclusion of system break down and handling failure have recently adopted extra corporeal lung assistance (ECLA) in a new fashion [7]. Own experience extends to more than 100 cases of pulmonary support. There are diverse underlying diseases causing terminal situations of gas exchange such as including sepsis, trauma, asphyxia, drowning, fat embolisation, pneumonia and other reasons of pulmonary failure with and without cardiac weakness. The amelioration of the percutaneous technique by ‘Seldinger’ for application of appropriate cannulae has mainly contributed to simplification of the complete technique, such as vascular access allows the application of a pumpless lung assistance by arterio-venous shunt under all possible circumstances such as emergency transportation, intensive care in different medical and emergency units [6]. An arterio-venous shunt up to two liters/min demands for increase of cardiac output in another wise cardiac healthy individuums well tolerated for weeks [2].
2.3 Support for temperature balance
The third essential component of the cardiopulmonary bypass is the temperature control. Resuscitation of drowned patients by controlled rewarming is the object of another derivative tool of classical CPB. This technique became as well the domain of the experiences of cardiac surgeons who have almost established standards how to cure these patients predominantly children. The pathophysiologic understanding of hypothermia and the biology of rewarming are essentials for application of this technique, a competence that is indispensable for general cardiac surgery. The application of extra corporeal system in these situations needs to be applied under surgical thoracic access.
2.4 Support for surgical and medical treatments
Technology of extra corporeal systems have discovered areas were circulation deviation of blood extracorporeally can help to perform surgery more effective and save or to apply medical treatments with success. These fields of applications are at this time low volume procedures and rather specific where however at least Perfusionists if not cardiac surgeons are requested for consultation. Cardio surgical units initiated to deliver this service function for these requesting fields by application and maintenance of such ambulatory systems. Established methods are such as pump bypass in liver transplantation for maintenance of venous return, as arterial bypass with or without oxygenation in thoracic and thoraco-abdominal aortic surgery, for performance of surgery for ascending tumor grow into the inferior vena caval systems, and for the application of extra corporeal systems in oncology [4].
For liver transplantation the caval blood is circumdeviated from the lower body area. Often hypernephroma and renal tumors may spread cranially within the vena cava to occasionally even reach and progress into the right atrium. This kind of Oncologic surgery can be performed more save and allowing complete tumor resection if extra corporeal circulation is applied to allow perfect intraoperative view and proper surgical technique.
Cerebro-vascular aneurysm or brain tumor is wanted to be operated under hypothermic circulatory arrest. Aneurysms can be clipped or resected in a bloodless area, vasculature of tumor firmly secured [1].
Thoracic aortic aneurysm is by standard operated with left atrial-femoral shunt if not with veno-arterial cardiopulmonary bypass. This method led to better results and remained therefore domain of cardiac surgeons whereas vascular surgeon upstain from this area. Of course thoraco-abdominal surgery is performed save and efficient with the help of circumdeviated blood with extra corporeal circulation.
Isolated limb perfusion is the method of choice in treatment of soft tissue sarcomas of the extremities [3]. The extra corporeal circulatory system allows proceedings with chemotherapy in dimensions not possible by systemic application. Comparative is the treatment of tumors by hyperthermia, which easily can be applied by an extra corporeal heat exchange system for a particular extremity concerned.
3. Options for progress
Cardio surgical units need to offer their competence in extra corporeal circulation with the paradigm of a multidisciplinary re-approach to treat more efficiently diseases concerned. Cardiac surgical units should become a service center for emergency rooms, catheter laboratories, oncology departments and emergency transportation institutions.
The actual standard of classical resuscitation for cardio circulatory arrest includes besides uncontrolled airway breathing chest massage aiming into force full rhythmic compression of the heart chambers. This crude method may become disruptive for more efficient and less traumatizing performance by maintenance of minimal circulation with the help percutaneous applied pump oxygenation.
Rigorous mechanical ventilation may be compromised by its consequences of volu- and barotrauma of the lungs, which are per se damaged by its previous underlying disease. Extra corporeal oxygenation with modern techniques may lead to a change of our attitude how to treat patients with acute pulmonary failure.
In both situations of acute failing ventricle and acute failing lungs our understanding of the reversible potential of both organ systems is marginal. Reversibility of any disease, the course of it may enter a status of acute failure, is the key for success of a passagerly applied extra corporeal system. Progress in our understanding in pathophysiology of such organ diseases could help to end in clear indications for application of extracorporeal system.
When new methods are introduced in medicine standards for their application are preferred to be established soon. For reasons of low volume workload actually considered for extra corporeal circulations procedures and for lack of parameters for clear indication talking about standards is actually to be postponed.
Evidence for effectiveness of treatment in these exemplified extra corporeal systems mostly is still away. The need for registries following homogeneous data collection is a particular request of the unequivocal suggestion of the committee. It may serve to be consulted for future perspectives and for data recruitment on the basis of accepted scientific proceedings. The Bakulev-Institution in Moscow under the guidance of Prof. Leo Bockeria has announced to establish such a registry for patients treated with extra corporeal circulation for oncologic reasons.
4. Drivers for change
The possibilities of extra corporeal circulation with its vast potential are by far not fully exhausted. Many areas need to be discovered. The potential deserves advertisement. By tradition cardiopulmonary bypass often is unjustified blamed for post cardio surgical morbidity. Our profession should avoid to emphasize by unqualified means the damaging potential of cardiopulmonary bypass.
Quality of extra corporeal circulation needs promotion. This has been established for cardiopulmonary bypass for most institutions by quality circles. Europe wide legislation for industrial products and cooperation were supportive means. Certification and self-control of perfusionists has been promoted by a unique exemplary self-organization, the European Board of Cardiovascular Perfusion (EBCP).
Cardiac surgical units need to realize a foreign discipline service if extra corporeal situation will be maintained in the hand of the competence. Misuse of a tool, which is well established, needs to be avoided. New areas for extra corporeal circulation deliver new experience, which stimulates competence. Traditional experience and competence need to be held in the hand of cardio-thoracic surgery. Success of extra corporeal circulatory system needs to be assessed in an ongoing process. Quality control could be established by multiinstitutional data collection, which allows more reliable and conclusive informations. In particular our understanding of organ failure and its reversibility is weak and deserves strenuous public support. There are at this time no clear criteria for essentials and time dependent criteria for application of extra corporeal organ support systems.
The committee, the members are listed below, did investigate into these key issues and fully support their essentials and meaning for cardio-thoracic surgery.
Appendix
Conference discussion
Mr F. Merkle (Berlin, Germany): Thank you for giving me the opportunity to comment. My name is Frank Merkle, perfusionist. I am the only perfusionist in this room. I would like to stress the points that Professor Birnbaum made. There are two issues here:
One is that research on cardiopulmonary bypass is almost non-existent at the moment in the cardiac field, because the machine is running, has been running for the past 50 years, and apart from that in Europe, maybe 20, 30 individuals are doing research on cardiopulmonary bypass. This is a standard procedure, but there are many problems still unsolved, as Professor Buckberg was saying yesterday. There was a study in the UK where the priming procedures were examined. The ingredients in the pump prime varied between every single institution, and there is no evidence in using this component or the other component.
Another issue is that most perfusionists lack education. They are not able to do studies by themselves because they don't have a scientific education in Germany, and in most other countries. Perfusionists are practice-oriented, former nurses, that have special training but no scientific training. This is also a problem because surgeons do not care much anymore for cardiopulmonary bypass as it has already been invented. And so I think to re-engineer or to restructure cardiopulmonary bypass would be a very beneficial area of work for surgeons, and perfusionists the same.
Dr F. Beyersdorf (Freiburg, Germany): I think you have outlined very nicely that part of our future is exactly in this field, and I agree with that. I think that the perfusion way can be much more advanced than it is today. You mentioned the life support systems, and if an airport can put a $50,000 defibrillator in the corner, they might be able to put another device, which is much cheaper, also in the corner.
In addition to that, we have the knowledge and the opportunity to perfuse more or less every organ in the body, and I am sure that this will be one of our future activities, that we expand the knowledge which we have on the heart and apply it to other organs, because much of the basic science we have found in the cardiac muscle also applies to the skeletal muscle as well as to the brain and also to the kidneys and to the liver.
As you know, there are strong research groups for liver transplantation who are not only thinking but who are doing modified reperfusion during the implantation phase, and this, of course, is not a question if all these techniques cannot be in the armamentarium of the cardiac surgeon. So I think we should really pay our attention to this part of our job.
Dr K. Engstrom (Umea, Sweden): I think it was a very interesting discussion. In Sweden we have a very good collaboration between perfusionists and surgeons, and they are part of our procedure, of course, and we share the same meeting, the Scandinavian Cardiothoracic Society has a joint meeting with the Scandinavian perfusionists, which is very fruitful, and the perfusionists I think have great power in all the data they can collect.
And actually two years ago in Sweden we had the first perfusionist Lena Lindholm who defended her PhD, and we had another PhD Staffan Svenmarker, who Torkel (Torkel Aberg)and myself guided through last year, and two more coming the next year. So I think it is important to keep up the good collaboration with the perfusionists.
Dr Birnbaum : I would like to stress again that there is much difference in the individual centers. I am sure this audience here has an open view as the average but all rest of cardiac surgery centers they are not aware about a potential, which they have in their hands. The professional of perfusionists is—and I would like to stress this again—on a high level of education: they have established standards in wonderful ways, unbelievable. Standards for education of cardio thoracic surgeons are away in comparison to these of perfusionists. They are already on the next step: Frank Merkle mentioned it; they want to do their own studies. In this field they need cooperative partners, they need help. Or, since they often request frustraneously for help because several do not care for them, they want to do it on their own. What our partners requests is, give us training how to do science so we do it. Right, did I say it right?
Mr Merkle : Yes.
Footnotes
Presented at the EACTS Symposium for the Future of Cardiac Surgery, Frankfurt, Germany, July 1–2, 2004.
References
This article has been cited by other articles:
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  J. B. Riley, P. D. Scott, and G. J. Schears Update on Safety Equipment for Extracorporeal Life Support (ECLS) Circuits Seminars in Cardiothoracic and Vascular Anesthesia, September 1, 2009; 13(3): 138 - 145. [Abstract] [PDF]
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 F. Merkle Perfusion Education and Training in Europe: European Board of Cardiovascular Perfusion Perfusion, January 1, 2006; 21(1): 3 - 12. [Abstract] [PDF]
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