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Ann Thorac Surg 2001;71:1623-1629
© 2001 The Society of Thoracic Surgeons
a Division of General Thoracic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
b Department of General Thoracic Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
c Department of Cardiothoracic Surgery, Strong Memorial Hospital, University of Rochester Medical Center, Rochester, New York, USA
d Division of Thoracic Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
e Statistics Unlimited, Savannah, Georgia, USA
Address reprint requests to Dr Wain, Department of Thoracic Surgery, Massachusetts General Hospital, Blake 1570, 55 Fruit St, Massachusetts General Hospital, Boston MA 02114
e-mail: Jwain{at}partners.org
Presented at the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 31Feb 2, 2000.
| Abstract |
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Methods. In a multicenter trial, 172 patients undergoing thoracotomy were randomized intraoperatively in a 2:1 ratio to receive surgical sealant applied to sites at risk for air leak after standard methods of lung closure (treatment group) or to have standard lung closure only (control group). The primary outcome variable was the percentage of patients free of air leakage throughout hospitalization. Secondary outcome variables were the control of air leaks intraoperatively and the time to postoperative air leak cessation. Time to chest tube removal, time to hospital discharge, and safety outcomes were also evaluated.
Results. Air leaks were identified before randomization in 89 of 117 patients in the treatment group and in 39 of 55 patients in the control group. Application of the sealant resulted in control of air leaks in 92% of treated patients (p
0.001). A significantly higher percentage of treated patients than control patients remained free of air leaks during hospitalization (39% versus 11%, p
0.001). The mean times to last observable air leak were 30.9 hours in the treatment group and 52.3 hours in the control group (p = 0.006). In the treatment group, trends were observed for reduced time to chest tube removal and earlier discharge. No significant difference was identified in postoperative morbidity and mortality between the two groups.
Conclusions. Air leaks after lung resection occur in most patients. The application of this novel surgical sealant appears to be effective and safe in preventing postoperative air leaks.
| Introduction |
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The prevention or elimination of air leaks is an important goal, as it can facilitate early removal of chest tubes, thereby reducing postoperative pain, facilitating postoperative recovery, and perhaps allowing for earlier hospital discharge. In a study of hospital stay after thoracic operations, inadequate control of postoperative pain and persistent air leaks were identified as the most common causes of delays in discharge [4].
Various methods have been tried to close or seal lung parenchyma. Standard methods of closure, including sutures and staples, have the disadvantage of causing further trauma to the lung tissue. Sealant materials ideally need to be sufficiently strong and adherent to withstand pressures of 30 to 40 cm H2O that are normally expected in the inflated lung. Sealant materials must also be flexible and compliant to accommodate the volume changes of the lung, resulting in a uniform surface load and minimizing the potential for secondary tearing of tissue at the application site. Such a material should also bond rapidly to the lung tissue and be unaltered by underlying blood or moisture [5]. Sealants also need to be locally nonirritating, systemically nontoxic, lacking in antigenicity, and bacteriostatic.
Recently, a new synthetic tissue sealant has been developed with designed mechanical characteristics approximating these qualities [5]. The sealant is a water-soluble polyethylene glycol-based gel that can be rapidly applied and photopolymerized on the lung surface. We designed a randomized, prospective controlled study to evaluate the efficacy and safety of this new synthetic bioresorbable surgical sealant in the control of parenchymal air leaks at surgical sites after lung resection.
| Material and methods |
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The study was performed at four metropolitan tertiary-care medical centers: Massachusetts General Hospital (Boston, MA); The Hospital of the University of Pennsylvania (Philadelphia, PA); The Johns Hopkins Hospital (Baltimore, MD); and Strong Memorial Hospital (Rochester, NY). All participating surgeons were board-certified thoracic surgeons who underwent laboratory training in the use of the surgical sealant or who collaborated with laboratory-trained surgeons initially. Two pilot patients were initially entered in the study at each of the four institutions to give participating surgeons clinical experience with the sealant and familiarity with the protocol before enrolling patients to be included in the efficacy analysis. Data from pilot patients were included in the safety analysis. The primary outcome variable of the study was the proportion of patients in the treatment and control groups who were free of air leaks throughout hospitalization. Secondary outcome variables were the proportion of patients in each group free of air leaks at the end of the operation, assessed by intraoperative saline submersion, and the time from skin closure to the last observed air leak. In addition, data were collected for the time from skin closure to chest tube removal and the time to hospital discharge. Safety was assessed by the incidence and severity of adverse events and by changes in selected laboratory values throughout the study period.
Intraoperatively, a patient was deemed ineligible for further participation if their procedure was completed by a video-assisted approach; if they underwent pneumonectomy, sleeve resection, or bronchoplasty; if they had inoperable disease; if inadequate hemostasis could not be achieved; or if other sealant materials were used. After completion of the lung resection, if the patient continued to meet eligibility requirements, saline submersion testing of the entire lung was performed to identify air leaks while manual ventilation was maintained with an end-inspiratory pressure of 20 to 30 cm of H2O. All sites of dissection and surgical manipulation were assessed and assigned a grade of 0 (no leak), 1 (countable air bubbles), 2 (stream of bubbles), or 3 (coalesced bubbles). Patients were then stratified into high- and low-risk strata by cumulative valuation of both preoperative and intraoperative factors for which the likelihood of postoperative air leaks is increased (Table 1). Standard techniques were used to reduce all leaks, including restapling, resuturing, or tissue grafting, followed by repeat submersion testing and regrading of leaks. The patients were than randomized within their risk stratum by opening one of two sealed envelopes (labeled either "high risk" or "low risk") in the operating room. Assignments were randomized to the treatment and control groups in a ratio of 2:1. Sealed envelopes were prepared for each risk stratum and study center in batches of six, with each batch containing four treatment group assignments and two control group assignments. Within batches, the envelopes were randomly sequenced by computer. At the time of the operation, one sealed envelope was removed from the top of the high-risk or low-risk stack, whichever was appropriate.
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Postoperatively, the pleural drainage device was managed according to the site-specific standard protocol of each institution. The device was examined postoperatively at 1, 4, 12, 24, 36, and 48 hours and then daily thereafter to identify the presence or absence of air leaks, the amount of pleural drainage, and whether additional suction was required in the drainage device. Evaluation and recording of chest tube output was handled by the nursing and physician staffs at the bedside who were blinded to the randomization status of the subject. Daily chest roentgenograms were obtained. On postoperative days 1 and 3, serial laboratory studies were performed including hematology, liver, and kidney function tests.
Over a 6-month follow-up period, patients returned for three follow-up evaluations, scheduled at approximately 1, 3, and 6 months postoperatively. Visits included a chest roentgenogram, laboratory studies, and an assessment of any potential adverse events since hospital discharge.
With a randomization ratio of 2:1 for the treatment and control groups, a sample size of 172 was calculated as sufficient to provide 90% power to assess differences in both primary and secondary efficacy outcomes. For the analysis of adverse events, a sample size of 120 for the treatment groups was estimated as the requirement to give 80% probability that a 95% upper confidence limit on the true rate would be no greater than 10%, assuming an adverse event rate of 5%. Data for the proportion of patients remaining free of air leaks at the end of the surgical procedure and those remaining leak-free though hospital discharge were analyzed by the MantelHaenszel test; the data for time to cessation of air leaks were analyzed by the generalized Wilcoxon test. The statistical analyses on the efficacy data did take into account the stratification by risk group and center. All statistical tests were two-sided and the level of significance was taken as 0.05.
| Results |
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Sealant application controlled all air leaks in 108 of 117 patients in the treatment group before skin closure. The percentage of patients with no intraoperative air leaks before skin closure was therefore significantly higher in the treatment group than in the control group: 92% versus 29% (p
0.001) (Fig 1). In the sealant group, 46 of 117 (39%) remained free of air leaks between the time of skin closure and hospital discharge, compared with only 6 of 55 (11%) in the control group (p
0.001) (Fig 1).
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| Comment |
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Various other techniques have been used to minimize air leaks after lung operation. Fibrin glue has disadvantages that include its human and, in some preparations, bovine origins; its relatively low tissue adhesion; and its questionable efficacy [6, 7]. The application of bovine pericardial strips along staple lines has been used with inconsistent results. Prolonged air leaks have occurred in up to 40% of patients treated by these methods [8, 9]. Attempts at using laser technology and argon beam coagulation have also been disappointing [10, 11]. The photopolymerizable lung sealant used in this study has a number of potential advantages, including its ability to polymerize without excess heating or local toxicity and its excellent tissue adherence due to formation of a highly compliant cross-linked polymer network [12, 13]. The application of this synthetic, bioresorbable surgical sealant in our study reduced the incidence of intraoperative air leaks to 8%. Postoperatively, those patients who received the sealant were significantly more likely to remain air leak free throughout their hospitalization than those in the control group.
Although some patients receiving sealant did develop air leaks after skin closure, more than three times as many patients in the sealant application group remained air leak free throughout their hospitalization, as compared with the control group. Even among patients who received sealant therapy but demonstrated postoperative air leaks, the duration of the air leak was significantly reduced as compared with the control group. This benefit of sealant application was seen in both the high- and low-risk subgroups, implying that selection of patients for sealant application based on the risk for air leak alone may not be justified. Additional study may be needed to identify any specific subgroups that may have a particular favorable outcome with sealant application.
There were no specific complications or morbidity that appeared to result from use of the sealant. No treated patient developed a bronchopleural fistula and the incidence of pneumothorax was similar in treated and control groups. Although not achieving statistical significance, 2% of treated patients did demonstrate residual spaces on follow-up chest roentgenograms without evidence of empyema or fistula. The sealant does serve as an adhesion barrier and a possible explanation for the residual space finding may be that the sealant modifies the expected postoperative reconformation of the lung and thoracic cavity. Use of the sealant did not lead to increased chest tube drainage or to pleural effusions. After application, the material degrades to its major water-soluble constituent parts, which are readily eliminated by the body, primarily through the kidneys. No evidence of hepatic or renal toxicity was identified in our patients receiving the sealant over the 6-month follow-up period.
Interestingly, despite the potential advantage conferred by earlier cessation of air leaks, we did not identify a statistically significant difference in chest tube duration or in length of hospitalization between the treated and control groups. In part, this finding may be because in this nonblinded study we did not attempt to modify the standard clinical pathways for patients at each institution. Nonetheless, because favorable trends with respect to chest tube duration and hospitalization were associated with use of the sealant, an additional factor may be that the statistical power of the study was insufficient to identify a difference between the treated and control groups. Alternatively, standard algorithms of chest tube management may not be appropriate in patients who have received the sealant. Avoidance or only limited use of intrapleural suction after sealant application may decrease the incidence of postoperative air leaks in these patients and further truncate the need for the pleural drainage device, facilitating patient recovery and earlier hospital discharge.
| Acknowledgments |
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| Footnotes |
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| Discussion |
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You did not show a decrease in the length of stay, and I wonder if that is because you had four different institutions and multiple surgeons? Can you comment on what your criteria was for when to remove the chest tubes? Is there a set amount of drainage that one surgeon would use to remove a tube versus another?
I continue to be surprised at this meeting, based on papers I saw today and yesterday, that the length of stay for a routine lobectomy is still 7 or 8 days. It seems to us that in our last 750 patients it is 4 or 5 days. I wonder why there is such a long length of stay for routine lobectomies? Does it have to do with the volume of chest tube drainage as opposed to air leaks?
The other thing I wonder about is your chest tube management. You mention in the presentation and not in the paper that patients were left on suction for 24 hours, but what happened after that? As you know, we have shown that sealing is superior to suction in stopping air leaks. And because of these trials, we favor water seal. Can you tell us if you found similar findings? Did suction increase the degree and longevity of the air leak? And why did you not use a leak meter, as we have used. In a trial like this, where you are looking critically at air leaks, why did you not use a Pleur-Evac system that has a built-in air leak meter?
My next concern is trapping the lung. It seems to me from looking at this product at the booth that it appears to be an excellent product, and it does not trap the lung at all. It appears that the lung is able to freely expand. Although you are applying the sealant with the lung in a semideflated state, the lung appears to expand well. You did, however, mention that you had a couple of space problems, in the treated group, although the difference between groups was not statistically significant. Can you comment on how well the lung expands after you apply the polymer?
My next question is about long-term follow-up. I know this sealant has been used in Europe for a few years. Can you tell me if over the last few years there have been any long-term problems among patients who have had this sealant? For example, I have learned that it should not be placed on the bronchus because it can prevent healing there.
The most important question is cost. As you know, and like too many other issues in our Society today, it all comes down to money. We are all sitting here in the audience and saying: "This looks great, but do we want to use it?" If the sealant leads to decreased hospital stays (you did not show that here, but I think it makes sense to say that we will probably be able to show that) is this product going to save us money? Well, the answer may depend on what this product will cost. So John, how much is the product going to cost? And if it costs less than $400 or $500, do you think that we will be able to show that it is a cost-effective product?
And finally, how do you respond to the naysayer who is sitting out there right now saying, "Why should I use this product? I send my patients home on postoperative day 3, 4, or 5 with a Heimlich valve. I do not care if they have an air leak or not, they are still going home on the fourth or fifth day, and they do not have prolonged hospital stays." How would you respond to him about the cost and morbidity of the Heimlich valve?
I would like to thank the Society for the opportunity to discuss this paper.
DR WAIN: I think those were all very pertinent points.
The study was designed as an efficacy and safety study, with the end points I mentioned, and it was not really powered to demonstrate an improvement in length of stay. We were hoping, secretly, of course, that that would pan out of the data. However, the favorable trend I think suggests that in fact a larger study would allow us to demonstrate a favorable impact on length of stay.
I do think as a multiinstitutional study with multiple surgeons and multiple sites, that chest tube management varied between the sites. In fact, midway through the study we reconvened and tried to come to some decision about standard chest tube management. For the most part, every patient was on suction for at least 24 hours, and then some sites put patients on water seal even if they had air leaks. At other sites, I think for most sites, patients were kept on suction until the air leaks disappeared. However, when we analyzed the results site by site, they were essentially equivalent. There was no difference in length of stay or chest tube duration. As I pointed out in that final slide, or the slide before the conclusions, the length of chest tube duration did not relate to volume of chest tube output. However, I think that one thing we have all learned from this study is that if you do have a sealant that works this well in the operating room, perhaps we can modify our standard algorithms of chest tube management as you have suggested in prior presentations.
We did not use the leak meter because it was not invented yet, and it was not available to us at that point in time. But it certainly is a good way to quantify leaks over time.
The lung does expand well. We found that as the surgeon gains more experience using this product, as patients were accumulated in the study, less polymer was applied. The less polymer used, the more flexible it is. When you first use the sealant, you tend to put it on a little bit too thick and that does not trap the lung, but it somewhat limits expansion. Later in the study the volume of sealant used by each surgeon decreased significantly and issues in terms of lung expansion were not significant at all.
I am not aware of any long-term follow-up problems in the European experience, but I have not inquired directly about that. I think it will be a cost-effective product. The cost in the United States has not been set, from my understanding, because the FDA has not given final approval for the polymer. But the more we can emphasize that if it comes in at the right cost and it saves a day, I think the better for us and for patients.
And lastly, in terms of the Heimlich valve, I think the phrase that "the Heimlich valve takes care of you seeing the patient but it does not necessarily take care of the patient," is a real one. Patients are oftentimes hindered by going home with a Heimlich valve. That does not mean they are not out of the hospital, of course, but it is not necessarily a satisfactory alternative, at least from our opinion in our own surgical practice. The hope would be that using a sealant such as this, would eliminate the need for sending patients home with Heimlich values and drainage bags attached to them and all that sort of messy stuff.
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-hydroxy acid)diacrylate macromers. Macromolecules 1993;26:581-587.
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