Surgery News - October 2007 - (Page 6)

6 TRANSPLANT SURGERY NEWS • O C T O B E R 2 0 0 7 Grant Advances Artificial Lung Research Aganglionosis BY DOUG BRUNK Else vier Global Medical Ne ws uman clinical trials of an implantable artifical lung that can serve as a bridge to lung transplantation may be just 3-4 years away. In August, the National Institutes of Health awarded a $5 million, 5-year grant to a team of researchers, led by Dr. Robert Bartlett, to refine the device for use in patients. The device, known as the Biolung, has thus far been tested in sheep. “When lay people hear about this, they think about a permanent device like an artificial heart,” said Dr. Bartlett, professor emeritus of surgery at the University of Michigan, Ann Arbor, and a pioneer in the development of artificial organs. “But clearly that won’t be practical, at least in the foreseeable future. It will be just a bridge to transplantation. It will come along in the usual fashion of artificial organs: relatively slowly.” In the 1980s, Dr. Bartlett, an ACS Fellow, led the researchers who developed the extracorporeal circulation membrane oxygenation (ECMO) machine, which is used worldwide to circulate and oxygenate the blood of patients with acute lung failure. ECMO can be used safely for weeks while a patient is bedridden in the intensive care unit, but the typical wait for a lung transplant is 2-3 months. The Biolung device is designed to help lung transplant candidates stay alive and mobile while awaiting a donor lung. The Biolung prototype Dr. Bartlett is studying uses tiny hollow fibers and the heart’s own pumping power to oxygenate blood. The device is made of plastic, weighs about 2 pounds, and is about the size of a soda pop can. It is connected to the pulmonary artery and is strapped in with a vest outside the chest wall. The device weighs 7-8 pounds when it’s full of blood. “The device will be outside [the chest H wall] because we expect to have to change it from time to time. This makes it easy to change, rather than having to do a new operation every time we change it,” Dr. Bartlett said. The Biolung prototypes are being made by MC3 Inc., a bioengineering firm in Ann Arbor that Dr. Bartlett cofound- The Biolung connects to the pulmonary artery and is outside the chest wall. ed 15 years ago with two bioengineers. Investigators at the University of Maryland, Baltimore; the University of Kentucky, Lexington; and the University of Pittsburgh in the United States, and in Osaka, Japan, are working on Biolung prototypes. At the University of Kentucky, Dr. Joseph Zwischenberger and his associates are studying a version of the Biolung that is intended to tolerate right heart failure. The modification contains a pump about the size of a 35-mm film cartridge. “In humans [with lung failure], as much as half the time the heart’s also in some degree of failure, because the lungs and the heart are connected in series and are dependent on each other,” said Dr. Zwis- chenberger, chair of the department of surgery at the University of Kentucky and an ACS Fellow. “When the lungs fail, often the heart will fail. So before going to clinical trials, I felt it was very important to have a version of this device that could support right heart failure. The pump is designed to accomplish the pumping requirements of the right ventricle, until the lung recovers or is replaced by a transplant.” Dr. Zwischenberger likened the development of the artifical lung to the development of the artificial heart. It took 2 decades for an artificial heart to be implanted in a human. “Learning from that experience, I feel very strongly that the [Food and Drug Administration] is going to allow us to first use [an artificial lung] device that is paracorporeal—partly to improve safety, partly to allow ready access to this developing technology, and partly to allow immediate large-animal testing to continue device improvement,” he said. To date, the Biolung has been used successfully in sheep for 30 days. Dr. Zwischenberger believes that if researchers can ensure consistent performance for a month or two in large prospective studies of sheep, they can then do a pilot study in humans. Dr. Bartlett predicted that the Biolung will help expand the pool of transplantable lungs. For example, he said, organ donors with severe brain damage usually have some degree of lung failure, and are not considered lung donors. But the Biolung could make a slightly damaged donor lung acceptable for transplant. About 1,000 lung transplantations are performed in the United States each year. “The results are quite good,” Dr. Bartlett said. “The limiting factor is donors. It’s estimated that there are about 20,000 patients each year who are potential lung transplant recipients.” ■ Arrested by Transplant BY MITCHEL L. ZOLER Else vier Global Medical Ne ws O R L A N D O — Nine children diagnosed with aganglionosis, a rare form of Hirschsprung’s disease that is almost always fatal, have been cured by intestinal transplantation. Since 1994, French surgeons have performed small intestine transplantation in 12 children who had a rare, congenital absence of ganglion cells throughout virtually the entire gastrointestinal tract. Of the 12 patients, 9 have survived. Eight of these have normal fecal continence, and all patients with functioning grafts have improved quality of life, Dr. Frederique Sauvat said at the annual meeting of the American Pediatric Surgical Association. “This is landmark work,” commented Dr. Daniel H. Teitelbaum, professor of surgery at the University of Michigan, Ann Arbor, and an ACS Fellow. “This is almost uniformly a fatal disease, and this provides a potential cure for some patients.” The patients had total intestinal aganglionosis, a rare form of Hirschsprung’s disease. All required total parenteral nutrition (TPN) before transplantation. In four patients, the disorder was confined to their intestine and hence they underwent only a small intestine transplantation, which received its blood supply by anastomosis to the inferior vena cava. The other eight also developed cirrhosis secondary to TPN, and they received a combined intestine and liver transplantation that also included the right colon, said Dr. Sauvat, a surgeon at the Necker Sick Children’s Hospital in Paris. The average age at the time of transplantation was 4.5 years, ranging from 0.9 to 12 years. Average body weight was 21 kg (range, 12 kg to 43 kg). Donors ranged in age from 0.7 to 35 years old, and the median waiting time for the transplanted organs was 19 months. The average weight ratio between donor and recipient was 3.2. Following transplant, patients were immunosuppressed with steroids, tacrolimus, and azathioprine in the early phase of this series. More recently, azathioprine was replaced by the interleukin-2 receptor antagonist basiliximab (Simulect). Patients were weaned off of TPN after a median of 57 days. A successful pull-through procedure was done on all eight children who received a transplanted colon. The three children who did not survive all received a combined intestine and liver transplant. These children died from uncontrolled sepsis that was caused by fungal infection in the first 3 months after transplantation. Early diagnosis is critical because it can help prevent development of TPN-related cirrhosis and thereby preclude the need for liver transplantation, which is associated with worse survival, Dr. Sauvat said. ■ MICHIGAN CRITICAL CARE CONSULTANTS, INC. http://www.nashvillesurg.com

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Surgery News - October 2007

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