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Ann Thorac Surg 2001;72:S2265-S2266
© 2001 The Society of Thoracic Surgeons
a Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104-4283, USA
e-mail: hank.edmunds{at}uphs.upns.upern.edu
We have heard today a very clear, well-outlined, and complete presentation, which was given impromptu, without slides, because of a computer failure. I’ve read the manuscript. The manuscript is wonderful, and we probably learned more from the impromptu presentation than we would have learned from a slide presentation. I really congratulate Dr Menasché on this feat.
I would like to reemphasize a few points that Dr Menasché has already emphasized. From the patient’s point of view, the purpose of the bypass surgery, regardless of how it is performed, is to bypass all of the obstructed vessels that need to be bypassed, and to ensure the best chance for the grafts to remain open. It is very important not to compromise the number of bypass grafts performed and not to compromise the chances of patency of the anastomoses. I’ve never done a coronary artery graft off bypass because I was concerned about the potential of these compromises.
The second point that Dr Menasché pointed out, is that cardiopulmonary bypass does make the patients sick. However, it does not make them as sick as we formerly thought. Most of the inflammatory component and the thrombotic complications associated with cardiopulmonary bypass are actually from the wound itself. Cardiac surgery is the only operation in which one routinely and continuously takes blood from the surgical field and recycles it directly into the intravascular system. In every other kind of surgery, blood from the field is absorbed into sponges or suctioned into a discard bucket. Recirculating surgical field blood is what really distinguishes cardiac from other types of surgery. Intuitively, off-pump bypass has the advantages of reducing the inflammatory response. Doctor Menasché has detailed this well, focusing on complement and neutrophils (and I would add monocytes), although we really do not have a clear idea as to the exact role that the cardiopulmonary bypass–induced inflammatory response plays clinically. But the fact of the matter is that most of the cytokines and vasoactive materials are created in the circuit, and off-pump bypass preempts that. But, as Dr Menasché has pointed out, this is not enough of an improvement to really make a difference clinically.
Doctor Menasché has underscored the scarcity of randomized studies addressing the inflammatory response in off-pump versus on-pump surgery. I agree that, except for a Finnish study, which showed no differences between the two groups, there are hardly any such randomized studies. The Finnish study had only 15 patients in each group, and with that small number it was unquestionably underpowered. Nevertheless, it was prospective and randomized. Understandably, surgeons are reluctant to plan randomized studies for techniques that are still in evolution, particularly when they are uncertain of whether or not these techniques will work. In this respect, we may be overemphasizing the need to have prospective, randomized studies when we are introducing new technology. However, there is no question that prospective, randomized studies are the best means to evaluate this technology.
At the end of the manuscript, Dr Menasché talks about various surface coatings and inhibitors that could potentially be used to reduce the inflammatory response. I am skeptical about surface coatings; I really do not think that heparin-coated surfaces do much of anything except to raise the price of the bypass circuit. They do not reduce thrombus formation. They reduce the terminal complex of complement, but Videm and others have not been able to show that this produces a salutary clinical effect. I think that selective inhibitors, such as high-dose aprotinin, which inhibits fibrinolysis and, to a lesser extent, kallikrein, may or may not partially reduce the inflammatory response. We know from our own studies that eptibibatide or integrelin can preserve platelets by inducing platelet anesthesia, that is, rendering platelets inactive during surgery and restoring platelet function at the end of cardiopulmonary bypass. The Japanese have shown that nafamostat will also inhibit some of the inflammatory response. So I believe that this approach will achieve better control of the inflammatory response associated with cardiopulmonary bypass.
Finally, off-pump bypass seems to be developing indications of its own: namely, renal failure, severe chronic obstructive pulmonary disease, and advanced age, particularly when the patients have good distal vessels. Patients who have poor runoff are probably better off undergoing operation on-pump. The indications are still evolving, and the aim is to identify those patients in whom one can use off-pump bypass to achieve good results, full revascularization, and high patency rates, and maybe reduce the mortality rate to less than 1%. This will have to be achieved by proper patient selection, which is what all surgery is about. Selection of the patient for the right procedure, and fitting the procedure to the patient to achieve the best outcome, is the essence of cardiac surgery.
This article has been cited by other articles:
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  P.-G. Chassot, P. van der Linden, M. Zaugg, X. M. Mueller, and D. R. Spahn Off-pump coronary artery bypass surgery: physiology and anaesthetic management{dagger} Br. J. Anaesth., March 1, 2004; 92(3): 400 - 413. [Abstract] [Full Text] [PDF]
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