Eur J Cardiothorac Surg 1999;16:S51-S56
© 1999 Elsevier Science NL
The preoperative selection of patients for emphysema surgery
Thomas R Todd
1
The Toronto Hospital, Division of Thoracic Surgery, Eaton North 10-226, 200 Elizabeth Street, Toronto, Ontario, Canada M5G 2C4
 |
Abstract
|
|---|
Lung volume reduction surgery for emphysema is evolving rapidly since its re-introduction in 1993. Lung transplantation remains a viable option for others with emphysema. The major difficulty facing surgeons lies in appropriate selection of patients for either procedure. The following paper represents an attempt by review of the literature and personal experience to describe some of the important features involved in patient selection. The current literature on patient selection for lung volume reduction surgery and transplantation for emphysema was reviewed, and the results within the University of Toronto Lung Volume Reduction Program were analyzed. The review suggests that the most reliable predictors of success are heterogeneous distribution of emphysematous change as reflected by the CAT scan and the quantitative ventilation perfusion scan with new emphasis being placed on the ventilation portion of the latter. Poor prognostic indicators are hypercarbia and pulmonary hypertension. It was felt that an algorithm could be established for determination of whether lung volume reduction or transplantation should be offered to patients for emphysema surgery. The algorithm is described.
Key Words: Preoperative • Emphysema surgery • Selection
|
1. Introduction
|
|---|
This decade has witnessed a resurgence in the surgical interest in emphysema. Nonetheless, surgeons have been involved in the therapy of this disorder for over decades. Although several procedures have not stood the test of time, and others seem today to be outrageous in their design, there are three that have emerged as either standard or as emerging into acceptance. These are:- 1. bullectomy or tube drainage of Bullae,
- 2. lung volume reduction (LVR),
- 3. transplantation.
As with all surgical procedures selection of the appropriate patient for a given operation is key to success. The field of emphysema surgery is changing rapidly and it is important to recognize that what follows are the opinions of the author at this point in time given in the context that there are the three surgical options noted above. The challenge to surgeons to develop a more rigorous assessment of these patients to enable accurate predictions of outcome and to permit the surgeon to determine the appropriate procedure is real. There is little doubt that assessment of patients and their selection to a given surgical therapy will change greatly over the next few years. Hopefully it will be the surgeons themselves that will lead this evaluation of assessment. It is also assumed that surgeons recognize that none of the options above are to be regarded as other than palliation. Although we may discover through rigorous assessment of our results that survival is altered there is as yet no evidence that survival is affected by any surgical procedure.
|
2. Assessment
|
|---|
There are several things to consider in the assessment of patients with emphysema. Many relate to a determination of medical fitness for surgery but there are several that are specific to the procedure itself and the selection of the particular operation.
2.1 General assessment
A review of any sizable experience with such patients reveals that they frequently have accompanying pathology. An example of this frequency is illustrated in Table 1
which describes the important pathology that was noted in the first 135 patients seen in the Toronto program. As these patients have with few exceptions been smokers vascular disease is common. It is important therefore to ensure that coronary artery disease is absent. This may be difficult by history alone as dyspnea usually sufficiently restricts activity that angina may not occur, only to rear it's head during the stress of the post-operative period. As a result any suggestion of atypical chest pain, arrhythmia, or prior history of cardiac disease should suggest that an assessment of potential cardiac ischemia be undertaken. A persantine thallium scan will suffice. Frequently however there is concern that pulmonary hypertension may be present and this may not be adequately resolved by a two-dimensional echocardiogram. Under these circumstances a right heart catheterization will almost certainly be performed and if so a coronary angiogram should also be undertaken.
The other major association is bronchogenic carcinoma. The accidental discovery of undetermined pulmonary nodules during the performance of a CAT scan has been noted by every program. As these nodules were not visualized on routine radiology there are for the most part early and highly curable stage one bronchogenic carcinomas (Fig. 1). When these nodules are identified there are several options open to the surgeon. Firstly one can perform an aspiration fine needle biopsy for diagnosis. Although the risk of pneumothorax in these patients is significant the latter are easily handled and the information sufficiently important to warrant the procedure. This is especially true if the lesion in question is not within the target area for resection as part of a lung volume reduction strategy. The second option is to resect the lesion as part of the LVR undertaking. This is favoured if indeed the lesion is peripheral and is within the appropriately targeted area for LVR. Given the fact that the lesion will be a T1, stage one carcinoma, a curative resection can be anticipated. Thirdly one can suggest expectant therapy and simply observe the activity of the lesion over 3–6 months. There is never a rush to operate upon patients with emphysema and thus this approach is perfectly acceptable unless the nodule is in such an area and of such a size that a further increase in size would no longer permit a wedge resection as part of lung volume reduction.
View larger version (93K):
[in this window]
[in a new window]
|
Fig. 1. CAT scan on a patient demonstrating a small lesion in the posterior segment left upper lobe. This proved to be an adenocarcinoma and patient underwent LVR with resection of the lesion.
|
|
|
3. Specific areas of investigation
|
|---|
The following questions should assist the surgeon in the selection of the appropriate procedure.- 1. Is there compression of Lung on CAT scanning?
- 2. Is there an increase in trapped gas volume?
- 3. Is there lung capable of suitable function should the mechanics of breathing be improved?
- 4. What is the PaCO2?
- 5. What is the mean pulmonary artery pressure?
Compression of lung is best appreciated on the CAT scan. The expansion of bullae sufficient to result in compression of adjacent lung suggests that the patient will benefit from a bullectomy or the insertion of a tube directly into the bulla. These are both old procedures and should not be confused with LVR. Indeed most patients who possess bullae large enough to fill 50% of the ipsilateral chest volume are probably candidates for bullectomy (Fig. 2), and the surgeon can anticipate a good result. Goldstraw et al. have described their experience with tube drainage of large bullae employing a modification of the original Monaldi procedure [1]. Talc is insufflated into the bulla once successful collapse has been obtained. Morbidity, mortality, and improvements in spirometry as reflected in post-operative FEV1 comparable to results obtained with LVR have been noted by the authors. The CAT scan will also provide information as to the presence of bronchiectasis as long as a high resolution scan is performed. The finding of bronchiectasis should suggest that LVR or bullectomy not be considered further.
Body box pulmonary function tests are important in the assessment of these patients. Simple spirometry is not adequate as it is only through phlthesmography that one be certain that hyperinflation is indeed secondary to increased trapped gas and not simply due to reactive airways disease. It is important to recognize that emphysema and chronic obstructive lung disease comprise a very heterogeneous population of patients all of whom are dyspneic and have reduced air flow on spirometry. Those with emphysema will have trapped gas volumes greater than 2.0 l and also will have diffusing capacities for carbon monoxide that are less than 50% of predicted. The absence of such abnormalities on body box studies should suggest to the surgeon that other forms of COPD are operative. In particular the patient may have asthmatic bronchitis. The latter will be further suggested by a history of familial asthma, asthma as a child, or episodic dyspnea. This constellation of findings on history with a low trapped gas volume and a DCO greater than 45% should alert the surgeon to the fact that the patient is unlikely to be suitable for LVR or even bullectomy.
There are as yet no definitive predictors of response or degree of response following LVR. Cooper et al. [2] and Weder et al. [3] have both indicated that a heterogeneous distribution of emphysema with apical predominance is predictive of good results. Nonetheless, there are other reports that would suggest that a homogeneous distribution can likewise undergo LVR with increases in exercise tolerance [4,5]. The final decision in this regard will await the results of further reports and hopefully randomized clinical trials. However at present a heterogeneous distribution of emphysema appears the best predictor of success. There are two studies designed to assist the surgeon in this determination, the CAT scan and the quantitative ventilation perfusion scan (V/Q scan). The CT scan provides a subjective interpretation of heterogeneity (Fig. 3a,b) and even when there is uniformity in the interpretation it can never be relied upon to provide an index of lung function. In other words the scan may appear heterogeneous but the area that appears to be the most preserved may itself be so damaged that an improvement in the mechanics of breathing cannot translate into improved exercise tolerance. The perfusion portion of the V/Q scan also provides a sense of heterogeneity as seen in Fig. 4
where perfusion is least in the apex. When this correlates with a CT scan that also demonstrates maximal disease in the apex the surgeon may be assured that heterogeneity exists. He still will remain uncertain if the rest of the lung is capable of sustaining improved exercise tolerance, presuming that the operation has effected an increased mechanical performance of the chest wall and diaphragm. The ventilation portion of the V/Q scan may suggest whether the other portions of the lung are indeed functional or not. In Fig. 5
one should note that as for perfusion the lung has been divided into three vertical zones. For each zone a ventilation curve has been generated. The expiratory or wash-out portion of the curve should be steep if the lung has normal compliance. Note in Fig. 5 that the slope of the wash-out portion of the curve is not nearly as steep in the upper lung zones particularly on the right side. The curve is steep in the dependent lung zones where perfusion is satisfactory, suggesting to the author that the dependent areas may function properly following apical lung volume reduction. In contrast Fig. 6
displays the wash-out curves for another patient who on CAT scanning and perfusion scanning had a heterogeneous distribution of emphysema. The slope of the curve in five of the six zones is not steep. Whether this aberration should raise concern that the function of the lung following reduction surgery is insufficient to permit the mechanical improvement to translate into functional ability is conjectural. However, we are currently utilizing this assessment in the Toronto program and hope to have sufficient data to establish the point in the not too distant future.
View larger version (100K):
[in this window]
[in a new window]
|
Fig. 3. (a) CAT scan through upper lung zones demonstrating significant destruction of lung substance. (b) Cat scan of same patient as in (a) but through the lower lung zone. Note that degree of emphysema is less.
|
|
View larger version (137K):
[in this window]
[in a new window]
|
Fig. 4. Quantitative perfusion lung scan from same patient as seen in Fig. 3. Note the major decrease in perfusion to the lung apices.
|
|
View larger version (26K):
[in this window]
[in a new window]
|
Fig. 5. Ventilation scan that illustrates the difference in slope of wash-out curves from the various lung zones.
|
|
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 6. Ventilation scan from a patient with emphysema. Note that the slope of the wash-out curves is poor in all areas but the left lower lobe.
|
|
Hypercarbia and pulmonary hypertension are both considered to be adverse predictors of outcome. Although there are several reports citing the association between hypercarbia and morbidity [6,7] there are no data to tell us what levels of PaCO2 should preclude the procedure. A PaCO2 greater than 55 mmHg is at present considered a contraindication to LVR but further information will be required to determine if this merely reflects the degree of lung damage or of itself is an absolute contraindication. The same comments hold true for pulmonary hypertension. All patients should undergo cardiac assessment with a two-dimensional echocardiogram. If there is concern that pulmonary artery hypertension exists either through a direct measurement of pulmonary artery systolic pressure or by more subtle evidence such as a decrease in pulmonary artery acceleration time, a right heart catheterization should be performed for confirmation. At present we will not undertake LVR if the mean pulmonary artery pressure is greater than 35 mmHg.
|
4. Conclusions
|
|---|
In an effort to provide guidance to the surgeon the following algorithm is offered. At the outset the CAT scan is one of the first if not the initial test after the chest X-ray. The latter will demonstrate either compression or no compression of lung surrounding the maximally damaged areas. If compression is seen then the patient should be a candidate for bullectomy. In the absence of other complicating features a good result can be anticipated under these circumstances. If however there is no compression but merely emphysema then the surgeon should proceed with a two-dimensional echocardiogram, a quantitative V/Q scan, and body box pulmonary function studies.
Following the analysis of these tests the selection of the operation could be established as outlined below.
LVR if:
- 1. a heterogeneous distribution is seen on both CAT scan and V/Q scan,
- 2. PaCO2 is less than 55 mmHg,
- 3. there is trapped gas greater than 2.0 l,
- 4. mean pulmonary artery pressure is less than 35 mmHg.
Transplantation if:
- 1. a PaCO2 greater than 55 mmHg,
- 2. mean pulmonary artery pressure greater than 35 mmHg,
- 3. trapped gas less than 2.0 l,
- 4. asthmatic bronchitis or bronchiectasis.
This clearly does not cover all possible clinical scenarios. There remain difficult areas where there are no clear guidelines on whether to operate or not let alone permit the determination of the appropriate procedure. This is particularly the case where the distribution of emphysema is homogeneous. Further investigation as to what will permit prediction of success in homogeneous disease are required. In addition the levels of hypercarbia and pulmonary artery pressure noted above that preclude LVR are purely arbitrary. We require more data to enable us to accurately predict results in patients with levels of PaCO2 between 55 and 65 and mean pulmonary artery pressures between 36 and 45 mmHg. If transplantation for emphysema were not so successful the answers to some of these questions would be quickly forthcoming. At present it presents a viable alternative to LVR and/or bullectomy.
The assessment of patients for emphysema surgery is at best imprecise. It will undoubtedly undergo major change over the next few years. It would appear that surgeons can produce improvement in the mechanics of breathing through LVR surgery. As noted above this will only be beneficial if the remaining lung retains sufficient function to enable the patient to make use of his/her mechanical advantage. The challenge to us all is to refine our assessment of these patients so that some more reliable and predictable measure of regional lung function permits us to accurately determine which if any operation is suitable.
|
Footnotes
|
|---|
Presented to the 2nd MITSIG International Symposium: Controversies in Cardiothoracic Surgery, Hong Kong, November 20–21, 1998.
1 Tel.: +1-416-340-4798; fax: +1-416-340-3478. 
|
References
|
|---|
- Shah SS, Goldstraw P. Surgical treatment of bullous emphysema: experience with the Brompton technique. Ann Thorac Surg 1994;58:1452-1456.[Abstract]
- Wang SC, Fisher KC, Slone RM, Gierada DS, Yusen RD, Lefrak SS, Pilgram TK, Cooper JD. Perfusion scintigraphy in the evaluation of lung volume reduction surgery: correlation with clinical outcome. Radiology 1997;205:243-248.[Abstract/Free Full Text]
- Slone RM, Pilgram TK, Gierada DS, Sagel SS, Glazer HS, Yusen RD, Cooper JD. Lung volume reduction surgery: comparison of pre-operative radiologic features and clinical outcome. Radiology 1997;204:613-615.[Free Full Text]
- Weder W, Thurnheer R, Stammberger U, Burge M, Russi EW, Bloch KE. Radiologic emphysema morphology is associated with outcome after surgical lung volume reduction. Ann Thorac Surg 1997;64:313-319.[Abstract/Free Full Text]
- Wisser W, Tschernko E, Wanke T, Senbaclavaci O, Kontros M, Wolner E, Klepetko W. Functional improvements in ventilatory mechanics after lung volume reduction surgery for homogeneous emphysema. Eur J Cardiothorac Surg 1997;12:525-530.[Abstract]
- Miller JI, Lee R, Mansour MD. Lung volume reduction surgery: lessons learned. Ann Thorac Surg 1996;61:1464-1469.[Abstract/Free Full Text]
- Szekely LA, Oelberg DA, Wright C, Johnson DC, Wain J, Trotman-Dickenson B, Shepard J, Kanarek DJ, Systrom D, Ginns LC. Preoperative predictors of operative morbdity and mortality in COPD patients undergoing bilateral lung volume reduction surgery. Chest 1997;111:550-558.[Abstract/Free Full Text]
Top
Abstract
1. Introduction
