Block allotransplantation of both lungs with pulmonary trunk and left atrium in dogs

History of lung transplantation

Lung transplantation nowadays is a well-accepted and routine treatment for well selected patients with terminal respiratory disease. However, it took several decades of experimental studies and clinical attempts to reach this success. In this paper, we describe the early experimental activity from the mid-forties until the early sixties. The first clinical attempt in humans was reported by Hardy and Webb in 1963 followed by others with short survival only except for one case by Derom et al. who lived for 10 months. Long-term successes were not reported until after the discovery of cyclosporine as a new immunosuppressive agent. Successful heart-lung transplantation (HLTx) for pulmonary vascular disease was performed by the Stanford group starting in 1981 while the Toronto group described good outcome after single-lung transplantation (SLTx) for pulmonary fibrosis in 1983 and after double-lung transplantation for emphysema in 1986. Further evolution in surgical techniques and in transplant type for the various forms of end-stage lung diseases are reviewed. The evolution in lung transplantation still continues nowadays with the use of pulmonary allografts coming from living-related donors, from donors after circulatory death, or after prior assessment and reconditioning during ex vivo lung perfusion (EVLP) in an attempt to overcome the critical shortage of suitable organs. Early outcome has significantly improved over the last three decades. Better treatment and prevention of chronic lung allograft dysfunction will hopefully result in further improvement of long-term survival after lung transplantation.

Supporting future surgical innovation. Lung transplantation as a case study

OBJECTIVE

Using lung transplantation as a case study, this article addressed the problem of supporting innovative clinical surgery in an era of increasing pressures for cost containment.

SUMMARY BACKGROUND DATA

After sporadic attempts at lung transplantation during the 1960s and 1970s, its clinical development began in earnest during the early 1980s. As a result of a wide range of incremental advances, the results have improved significantly. The Health Care Financing Administration, however, has not yet issued a national policy covering lung transplants and has left the coverage decision to the discretion of its regional contractors.

METHODS

The authors surveyed the major commercial insurers, the Blue Cross Blue Shield Association, and a sample of Medicare intermediaries to evaluate the coverage of lung transplantation. They also interviewed the National Heart, Lung, and Blood Institute and industrial firms about their support for clinical research.

RESULTS

Government and industry funding were limited, and the development and assessment of lung transplants have been financed predominantly by academic institutions through cross-subsidization from patient care and teaching funds. The major private payers and Blue Cross Blue Shield decided to cover this procedure in the early 1990s. Coverage decisions by Medicare intermediaries, however, revealed considerable variability. Moreover, the absence of a specific diagnosis-related group for lung transplants had considerable consequences for institutions in all-payer states, in which payments appeared to be considerably lower than the mean costs of a transplant procedure (about $110,000).

CONCLUSIONS

This analysis indicated that there was a growing disparity between the increasing demand for outcomes data about new procedures and the limited resources available for supporting the development and assessment of new operations. It this disparity is not addressed, the rate of surgical innovation may be jeopardized, and timely outcomes data may not be acquired. It was concluded that provisional coverage within a predetermined research protocol may be a promising mechanism to remedy this situation, providing timely assessment of new procedures before widespread application.

The evolution of techniques and indications for lung transplantation

The techniques and indications for lung transplantation have evolved significantly in the past 6 years. We initially restricted single-lung transplantation to patients with pulmonary fibrosis and developed the double-lung transplantation procedure for patients with emphysema or cystic fibrosis. However, with the double-lung procedure, a 25% mortality rate resulted from ischemic complications at the tracheal anastomosis. The technique was altered to incorporate bilateral bronchial anastomosis, with a resulting reduction in airway complications. The double-lung transplantation procedure continued to have significant drawbacks, including intraoperative and postoperative hemorrhage, and cardiac complications due to prolonged cardiopulmonary bypass, ischemic cardiac arrest, and extensive manipulation of the heart. These problems recently have been addressed with a much simplified procedure incorporating a bilateral transverse thoracosternotomy, replacement of the right lung without cardiopulmonary bypass, and replacement of the left lung with or without a short period of partial bypass. This procedure has been successfully used for emphysema and for cystic fibrosis. The technique of single-lung transplantation also has been simplified and indications have been expanded to include selected patients with emphysema and with primary pulmonary hypertension. With single-lung transplantation, each of the lungs from a donor has been successfully used for a separate recipient on several occasions, improving the supply of available donor organs.

Canine double-lung allotransplantation: operative technique and results for 12-h preservation studies

A canine double-lung allotransplantation model was developed to study the effects of 12-h static pulmonary preservation. This model has not been used extensively for such experiments but allows a detailed evaluation of the quality of preservation. An operative technique is described in which cautery dissection and preliminary devascularization of the recipient right lung allows the period of cardiopulmonary bypass to be limited and reduces postoperative bleeding. Six double-lung blocks were successfully orthotopically transplanted and recipient animals were studied for 12 h postoperatively. All animals survived the study period and had a mean PO2 (FIO2 0.4) of 141 mm Hg, 12 h following reimplantation suggesting adequate pulmonary preservation. There was no evidence of pulmonary edema at any time following implantation, although airway pressures and pulmonary vascular resistance were elevated. The role of this model in lung preservation studies is discussed.

Lung transplantation

The supply of donor organs remains extremely limited, and improved methods of maintaining the lungs of potential donors to allow for transplantation must be developed. Currently the upper limit of donor lung ischemic even with our "best" preservation techniques is approximately 4 to 6 hours. Improved methods for preservation will increase the supply of suitable lungs and will considerably simplify the logistics of transplantation just as has occurred with liver transplantation. Efficient use of donor organs remains of paramount importance. We recently performed two single-lung transplants utilizing lungs from one donor. Likewise, there is no reason why a lung could not be sent to another center for transplantation if the harvesting group uses only one lung. Sufficient progress has been achieved to date to warrant continued application of lung transplantation for end-stage pulmonary disease. With increasing experience, one can anticipate refinement of techniques and broader application of these procedures. Single lung transplantation, initially restricted to patients with end-stage pulmonary fibrosis, has now been successfully applied to patients with emphysema, pulmonary hypertension, and other conditions. Although transplantation currently can offer real benefit only to a limited number of persons, it serves to create hope for many others. An additional benefit may prove to be the interest and attention that transplantation focuses on patients with end-stage lung disease and on the pathophysiology of chronic respiratory failure. Knowledge gained may ultimately result in the prevention of many of the disorders for which lung transplantation currently offers the only hope.

Experimental en bloc double-lung transplantation

A technique of en bloc double-lung transplantation through a median sternotomy has been developed. Hypothermic circulatory arrest was used after surface cooling in 7 puppies (mean weight, 3.1 kg; range, 1.5 to 4.1 kg). A double lung block, consisting of the two lungs, distal trachea, the main pulmonary artery, and a large cuff of left atrium, was removed from weight-matched donors. After the arrest of the circulation by inflow occlusion, bilateral pneumonectomies were performed in the recipient. The donor double-lung block was then implanted with anastomoses at the distal trachea, the posterior left atrium, and the main pulmonary artery. All animals were successfully rewarmed and had excellent hemodynamic function and gas exchange for periods of up to 24 hours. If primate experiments with long-term survival confirm these initial results, this procedure may have a role in the treatment of patients with end-stage respiratory disease but acceptable cardiac function.