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Ann Thorac Surg 1996;61:948
© 1996 The Society of Thoracic Surgeons
DR MARK J. KRASNA (Baltimore, MD): I compliment Dr Hill and associates on this work and their previous work from 2 or 3 years ago. I think you have shown eloquently that in an animal model, specifically in a pig model, there is probably a bad effect caused by using CO2 insufflation.
We have shown here clinically a series of 32 patients with right-sided measurements and systemic arterial pressure measurements with no side effect of CO2 insufflation. Since that time we have used CO2 insufflation routinely in more than 450 thoracoscopies with no untoward effects. I think, therefore, that although these data clearly show it is a not a good idea in a pig model, it may be applicable in certain indications to increase exposure in a clinical setting.
DR THOMAS M. DANIEL (Charlottesville, VA): Doctor Hill sent me his manuscript so I had the advantage of looking at that. You may ask, What has your study added to what is pretty much an accepted fact, which is that most people doing thoracoscopy do it with open ports? This is not an issue. I think what you have done is quantitated the effect of positive pressure. At the low pressure of 5 mm Hg you showed a 50% reduction in cardiac index and at 10 mm Hg you had an 80% reduction. I think that is useful clinical information to quantitate an observation.
I would challenge you to do the same kind of elegant work to try to answer some of the questions now coming up. I know your program is going to be setting up a lung shaving study. A good question to study is whether shaving one lung achieves a bilateral effect. It is related to the same question addressed in your report. What are the pressure changes within the whole thorax if you do one side? With just a little change in your technique you might be able to show you do not need to do a sternotomy and bilateral lung shaving, if with unilateral shaving you can create a change in the pressures of the contralateral side. I hope your group will study questions like that.
DR BRADLEY M. RODGERS (Charlottesville, VA): Doctor Hill, that was a very provocative study. I have two questions. I think most of your data we would have suspected intuitively, but I am a little surprised by the elevation of the pulmonary capillary wedge pressures. Could you speculate on what you think is going on there?
You do not tell us exactly how you handled the ventilator in these animals; what sort of pressures were you using? And what difference do you think position would make? I gather from your illustrations that the pigs are kept supine when you do the procedure. Have you tried lateral decubitus position? Do you think that would change the hemodynamics in any way?
DR HILL: Doctor Rogers, different positions may make a difference, although I doubt it. We saw such a dramatic effect on the right side that we may have indeed been influencing the left side as a reflection of the wedge pressures, left ventricular stroke work index, and cardiac index.
Doctor Krasna, I am well aware of your excellent work and presentation to this society 2 years ago. Unfortunately, we do not put Swan-Ganz catheters in all our patients who undergo thoracoscopy, so to fine-tune the data is difficult in the human population. Your report was as good as could be done in the human population. Several investigators have reported elevated central venous pressures using insufflation, but as far as the actual measurements of cardiac index, left ventricular stroke work index, pulmonary capillary wedge pressure, and mean pulmonary artery pressure, it is difficult when you do not have pulmonary catheters, which a lot of times we do not. The multiple open-trocar technique may well be a way of decreasing these effects by simply having one trocar open periodically to release the pressure and help prevent cardiovascular compromise, as Dr Daniel suggested.
Related Article
Ann. Thorac. Surg. 1996 61: 945-948.
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