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J Thorac Cardiovasc Surg 2008;135:1216-1219
© 2008 The American Association for Thoracic Surgery
Invited Commentary |
I am intrigued by the operation and am impressed that such an undertaking can be completed. Would you comment on the following technical issues. How do you size the implants, and how are cardiac hemodynamics measured intraoperatively and postoperatively to prevent cardiac tamponade, ventricular arrhythmia, or decreased venous return?
Dr Shen. The issue of how to size the implant is one that we believe is based in some ways on trial and error at the time of the operation. After the pneumonectomy space has been opened and all of the scar and adhesions have been mobilized to allow repositioning of the herniated lung back to the proper side and repositioning mediastinal structures, heart, and pericardium back to a central position, we typically have used a technique where a measured amount of saline is poured into the chest to be able to estimate the volume of this often complex space. On the basis of the measured volume of saline that is then removed from the chest, we then select a number of breast implant sizers, test-sizers, before committing to an actual implant. I think it also speaks to your second question on how to monitor these patients postoperatively. Once the approximate volume has been selected, a critical technical point is that extensive monitoring of hemodynamics in terms of pulse, blood pressure, and central venous pressure with central line monitoring is important to be on the lookout for tamponade physiology. In addition, we use flexible bronchoscopy extensively throughout the procedure once the mediastinal structures have been centrally located, as well as after test placement of the implants and after the chest has been closed. A final check once the patient has been turned supine is also done. It's worth noting that 4 of the 18 patients, after partial closure of the chest, developed tamponade physiology and had to have their partially closed incision reopened and the volume adjusted. We also make use of intraoperative radiography with a chest x-ray done at the end of the procedure, also looking for atelectasis and overcorrection. So I think the issue of how to correctly size the repositioning is intimately tied to the monitoring that's done in the procedure.
Dr Murthy. I have 2 other technical questions. Can you do this extrapleurally? It seems like that might be an easier approach, not having done one of these, but just thinking about it. Might tissue expanders be a more appropriate choice to fill the space? This is reported in the pediatric literature.
Dr Shen. The tasks that need to be achieved to successfully reposition the mediastinum are that the scar and adhesions holding the herniated lung, as well as the pericardium and other mediastinal structures, need to be lysed and divided to allow one to centrally reposition the mediastinum. Another important technical point to emphasize is that the junction between the pneumonectomy stump and the main bronchus needs to be extensively dissected and liberated. That junction is oftentimes scarred to either the vertebral body or the posterior mediastinum, and if you don't achieve liberation and complete lysis of that scar tissue there, you can still reposition the mediastinal structures centrally, but if that tethering point hasn't been fully dissected, you're still going to have mechanical compression of either the main or lobar bronchi and not achieve the desired result. Whether or not that can be done easier from an extrapleural approach, I don't think so. To accomplish all those things, I think it's necessary to open the pneumonectomy space.
As far as the issue of having adjustable tissue expanders, it has been described extensively in the pediatric literature. I think that for pediatric patients, to allow for further somatic growth, it is worthwhile to consider. In adult patients, it's really not necessary. Several other groups have reported the use of adjustable breast implants in adults and have not found the need to make adjustments after surgery.
Dr Murthy. I'll skip to the last point. Finally, what might be the mechanism for the apparent amelioration of this syndrome? Your spirometry data actually argue against that you have solved a functional airway obstruction. Other reports and my own common sense would suggest that there would be an improvement in spirometry measurements, especially FEV1, if a suspected airway stenosis were to be relieved by your maneuvers. Perhaps it is the relief of some intracardiac shunt or right atrial compression that might lead to your improvement, and there is a syndrome, platypnea-orthodeoxia, that has been reported as a possible putative mechanism for this kind of problem.
Dr Shen. We believe that there are 2 important physiologic derangements that contribute to the overall syndrome. The first is obviously a mechanical compression of the main bronchus or lobar bronchus from the mediastinal shift, and so you get a functional and a dynamic compressive upper airway obstruction. The second component to the syndrome is due to the shift and herniation and overexpansion of the residual lung. In patients with symptoms of dyspnea and shortness of breath from this syndrome, I think it's a combination of these mechanisms, and each patient probably has a mix of the effects of the overexpansion and herniation of the lung, as well as the mechanical compression of the airway itself. We believe that the relief that patients get from surgical correction with mediastinal repositioning really comes from addressing both of those issues independently. They are independent and also connected. We did find in the spirometry data that the FVC decreased in every patient, reflecting correction of the hyperexpansion. The results with FEV1 have not been consistent. In Dr Grillo's original report, 7 patients had preoperative and postoperative spirometry, 4 patients had improvement in the FEV1, and 3 patients had decline. In this current series of patients, 9 decreased and 2 increased. I think the relief of dyspnea that patients get is probably a combination of the correction of the overexpansion of the herniated lung and relief of the mechanical obstruction on the airway. Depending on which component of that is more important for any given patient, that's probably ultimately what affects the end result of relief of symptoms.
Dr Murthy. That such a study could be done clearly demonstrates the expertise of you and your group.
Dr J. Deslauriers (Quebec City, Quebec, Canada). What do you think is the true incidence of this complication after pneumonectomy?
Dr Shen. I think it's extremely low. The only reported incidence I've seen is an estimate of 1 in 640 pneumonectomies in children, and obviously that's much lower in adults.
Dr Deslauriers. So it would be extremely rare.
Dr Shen. Extremely rare.
Dr Deslauriers. Perhaps 1 in 1,000 or something like that?
Dr Shen. At least, yes.
Dr Deslauriers. My second question has to do with the sometimes associated bronchomalacia. This problem was mentioned in the first article written by Dr Grillo, and it relates to the destruction of bronchial cartilages that may occur over time. Do you still just put the intrapleural prosthesis, or do you do something else with the bronchus to stabilize it?
Dr Shen. You raise an important point in the management of this syndrome. It is difficult to determine which of these patients will continue to have malacic changes in the airway after repositioning. We typically do have these patients undergo awake bronchoscopy so they can do provocative maneuvers. Sometimes you're turning them on their side. We look specifically at the time of bronchoscopy to see if we can see the cartilaginous rings and dynamic change. Even with all of those maneuvers, we have not been able to determine with any high degree of accuracy preoperatively which patients will continue to have malacia after successful repositioning. In the original series of articles there were a number of things that tried to address the malacia, including tracheal resection of that segment with reconstruction. Our current recommendation would be that patients who have persistent malacic segments after repositioning undergo prompt tracheal stenting.
Dr Deslauriers. So you just do the described operation, hoping that the bronchus will be stabilized once the mediastinum is repositioned.
Dr Shen. Yes.
Dr Deslauriers. Do you perform a bronchoscopy while you're doing these procedures to see if the trachea has been repositioned in the midline?
Dr Shen. Yes, absolutely. It's one point I tried to stress with some of the questions that Dr Murthy asked. It is an important part of the technical conduct of the operation to be conducting flexible bronchoscopy at multiple time points during the operation: once the mediastinal structures have been repositioned into the central location to assess how you've relieved the compression on the airway, when the implants are placed, when you begin closing the chest, and then, finally, again looking with a bronchoscope when the patients are turned onto their back. In several of the cases in this series we found that the patients had been overcorrected and required reopening the incision and removing some of the volume from their implants.
Dr Deslauriers. Do these prostheses have a subcutaneous port where you can aspirate fluid out if required?
Dr Shen. Yes there are implants with subcutaneous ports available.
Dr Deslauriers. So you don't really need to reopen the chest.
Dr Shen. In 4 cases the chest had already been mostly closed, and according to the intraoperative chest x-ray or bronchoscopy, we found that they had actually been overcorrected, or they were fine when they were in the lateral decubitus position. Then when they were put supine again, they were overcorrected, and you needed to be able to at least access the implants to remove some volume. It would not be practical to routinely use the implants with subcutaneous ports, because multiple implants are being placed into the pneumonectomy space.
Dr Deslauriers. There were 3 patients in your series in whom the pneumonectomy had been done for chronic lung disease, presumably for tuberculosis, or destroyed lung. Because these patients usually already have their mediastinum shifted beforehand, why do you think they developed this syndrome?
Dr Shen. Why was the mediastinum not fixed in those patients?
Dr Deslauriers. Well, usually it's fixed, yes.
Dr Shen. The 3 patients who underwent operation for infectious reasons had airway obstruction or were developing chronic pulmonary infections. They were not necessarily patients who originally underwent pneumonectomy for infectious causes, and because they developed post-pneumonectomy syndrome I don't think their mediastinum was fixed before pneumonectomy.
Dr O. Adebo (Ibadan, Nigeria). I'm curious about the explanation that you gave for the pathology. Most of the pneumonectomies we do are for tuberculous destroyed lung, and at the end of the pneumonectomy, the patient's x-ray looks similar to that of patients with postpneumonectomy syndrome, and they have no symptoms. At the end of the pneumonectomy, the shift is as much, if not more, than what you showed from your x-rays, and I'm curious why those patients don't seem to develop any respiratory problem or symptoms despite the remarkable shift of the heart to the operated side, the pneumonectomized side, and we don't make any effort, of course, to reposition it because the lungs are invariably there already and the patient is well adjusted to it. So I'm wondering why the explanation you gave would be the one to undermine this syndrome.
Dr Shen. That's an interesting observation. I don't really have a good explanation for why you don't observe this syndrome in those patients who essentially have a destroyed lung. Have you ever seen this syndrome in patients who have undergone pneumonectomy?
One of the continuing unanswered questions with this syndrome is what are the predisposing factors, why is this such a rare syndrome, and are there factors that you could use to predict who is more likely to develop this syndrome. We don't really have any further insight into that. It seems to be that this is more prevalent in women and is more prevalent or more likely in patients who have undergone right pneumonectomy. If we were to look at the total, the 29 patients who were treated at Massachusetts General from 1979 to 2004, 22 of the 29 were women and 20 of the 29 patients had a right pneumonectomy. But as to the real question, why do some people get it and what are the predisposing factors, I think we still don't know.
Dr W. Klepetko (Vienna, Austria). I would like to come back to the importance of the hemodynamic component in the syndrome that was stressed before. We recently identified a series of 5 or 6 patients in our patient cohort who developed severe postpneumonectomy syndrome based on hemodynamic grounds either on the reopening of the foramen ovale or on the compression of the right atrium because of an unusually high elevation of the right diaphragm. These were all cases of right pneumonectomy. The leading symptom in those patients was always severe hypoxemia, which sometimes developed rapidly, and after the correction, either the closure of the intracardiac shunt or the repositioning of the diaphragm, the hypoxemia was overcome and blood gases were pretty much normalized.
What have you done to rule out such a hemodynamic component? Could you give us some data on your blood gases, which you did not show us. Were they impaired before the operation, and how did they behave after the operation?
Dr Shen. I don't have any data concerning preoperative and postoperative blood gases to be able to share with you. In many of the cases in this series that were evaluated, part of the preoperative evaluation and determination that the patient had postpneumonectomy syndrome included echocardiography, and sometimes patients also have transesophageal echo studies in the operating room. We are looking specifically for alternative explanations for their symptoms.
Dr Klepetko. Have you seen in your large experience any patients with such a syndrome based on hemodynamic grounds only?
Dr Shen. No. There have been a couple of patients who continued to have similar symptoms after postpneumonectomy surgical repair with repositioning and were found to have some cardiac issues that were uncovered.
Dr T. Daniel (Charlottesville, Va). Congratulations, Dr Shen, on an interesting presentation of this rare condition. I don't know whether operating on 3 additional patients makes me an expert, but perhaps so. To suggest an answer to our colleague from Nigeria as to causation, we looked at some of our patients and the patients in Dr Grillo's first report, and there seems to be a narrow interval between the sternum and the anterior portion of the vertebral body that may show up in that difference in the sex incidence. Most women might have less of a barrel chest, and this may be a predisposing factor. Certainly for all the pneumonectomies done in the world, why such a small handful get it, we don't know, but that may be a predisposing cause.
To Dr Deslauriers' question as to why we don't use the adjustable port to modify these patients, 1 of 3 patients had a problem in the postoperative unit that required returning to the operating room and taking some fluid out. We used a breast prosthesis with an implantable port subcutaneously on the first patient and thought we got a good result, but 6 months after operation, she apparently had a stress fracture of the polyethylene catheter connecting the prosthesis to the extrathoracic position and had a, quote, "flat tire" and redeveloped the syndrome, and we reoperated on her with a successful result. So that's a factor you wouldn't think of.
Related Article
J. Thorac. Cardiovasc. Surg. 2008 135: 1210-1219.
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