P&S Journal: Fall 1994, Vol.14, No.3
About 10 years old, lung transplantation is a relatively new field. But Dr. Craig Smith, director of the cardiopulmonary transplant program, has introduced innovations to the procedure and has made CPMC one of the top five U.S. centers in lung transplantation.
His accomplishment is notable because the limited number of donor lungs makes lung transplantation such an infrequent procedure. "Perhaps only pancreas transplantation is rarer," says Dr. Smith. Even though each lung can be transplanted into separate recipients, too few donor lungs exist because they deteriorate rapidly and are not harvested as easily as are hearts from brain-dead patients. Of the 2,000 heart transplant donors each year, only about 30 percent to 50 percent have lungs acceptable for transplantation. In 1993, about 750 double- and single-lung transplants occurred in the United States.
Since Dr. Smith joined P&S in 1984, he and his colleagues have performed 110 lung transplants, including patients with emphysema, other types of chronic pulmonary obstructions without infected secretions, pulmonary hypertension, and pulmonary fibrosis, including cystic fibrosis.
He identifies the management of lung transplant recipients a few weeks after surgery as his group's major contribution to the field. Five years ago, the standard of postoperative care was withholding steroids and using high doses of immunosuppressants. Steroids, it was believed, inhibited healing of the bronchial and tracheal tissue, sites where the new lung is stitched in place. "There is less vasculature in this region," explains Dr. Smith, "and as a result, connections break down."
In 1986, however, a resident in Dr. Smith's laboratory, Dr. Joseph Auteri, showed that steroids had no negative impact on healing single-lung transplants in dogs. Since the results were presented at a pulmonary conference, most centers in the United States have given low-dose maintenance of steroids the first day after the operation. Steroids may be beneficial by reducing the consequences of early rejection on blood flow to the lung.
CPMC also stands out, says Dr. Smith, in the use of lung transplants to treat cystic fibrosis patients. In 1989, Dr. Smith was the fourth surgeon in the United States to do a bilateral single-lung transplant, a special type of double-lung operation, in a cystic fibrosis patient. In 15 CF patients who underwent lung transplantation, CPMC has been able to achieve 100 percent survival, statistics not seen elsewhere.
A significant challenge in the field is determining whether a double- or single-lung transplant is more appropriate for a specific disease. The current trend, says Dr. Smith, is to do fewer single-lung transplants because double-lung transplants may give better results for some conditions. Initially, for example, most centers did single-lung transplants for pulmonary hypertension, but Dr. Smith's experience and that of others suggest that double-lung transplants are better.
"It is hard to say anything meaningful about clinical results in lung transplants because the patient base is so small and the numbers are statistically insignificant," Dr. Smith says. "We're left to follow our instincts."
To reduce speculation, Dr. Smith and Dr. Osvaldo Yano, an associate research scientist in surgery, have returned to the basic research laboratory. By creating a rat model of pulmonary hypertension and treating it with transplantation, the researchers hope to characterize physiological conditions that necessitate single- or double-lung repair.