Hypothermic preservation of the heart and lungs with Collins solution: effect on cardiorespiratory function following heart-lung allotransplantation in dogs

University of Wisconsin versus modified Euro-Collins solution for lung preservation

In a canine model, the quality of lung preservation was assessed using pulmonary artery flush after prostacyclin administration with either modified Euro-Collins solution or University of Wisconsin solution. Twelve combined heterotopic heart and orthotopic left lung allotransplantations were performed after 6 hours of cold ischemia. Myocardial preservation was achieved using St. Thomas Hospital solution. Donor organs were anastomosed parallel to the recipient's heart and right lung, and the superior vena cava inflow was directed into the transplanted heart-left lung block after ligation of the recipient's superior vena cava proximal to the caval anastomosis. Postoperatively, cardiorespiratory function was evaluated separately for donor and recipient organs at an inspired oxygen fraction of 0.4 for a maximum of 12 hours. Significantly improved oxygenation and lower pulmonary vascular resistance index of the donor lung was observed in the University of Wisconsin + prostacyclin group, whereas pulmonary artery pressures showed no significant differences in between both groups. It is concluded that superior results in lung preservation can be achieved with pulmonary artery flush perfusion using University of Wisconsin solution and prostacyclin when compared with Euro-Collins solution and prostacyclin.

Pulmonary mechanics after cardio-pulmonary transplantation, an experimental study

An experimental model was developed in pigs (weight: 25 +/- 2 kg), to evaluate pulmonary mechanics during the first 2 h of reperfusion following heart-lung transplantation. We studied two groups with three transplantations each: group A (45 min of preservation) and group B (6 h of preservation). After rinsing out the heart-lung mass by the injection of a cold intracellular solution (K+ = 115 mEq/l) into the aorta and the pulmonary artery, the organs were removed and conserved in a cold environment (0.5 degrees C). The orthotopic heart-lung transplantation was carried out using extra-corporeal circulation. Pulmonary mechanics were evaluated before and after transplantation by measuring the pulmonary compliance (C), and the aero-dynamic resistance (R) with an interrupted air flow technique. [table: see text] The duration of ischaemia appeared to be a pernicious factor in cardiopulmonary function. In all cases, the protection protocol of the heart-lung block had allowed a cutting-off of the cardiorespiratory assistance. However, there were major pulmonary mechanical perturbations, associated with a reduction in the pulmonary compliance and a very important increase in the aerodynamic resistance.

Antagonisation of platelet activating factor--a new therapeutic concept for improvement of organ quality in lung preservation

The release of platelet activating factor (PAF) is thought to be one of the most important pathophysiological pathways in the development of ischemic lung injury. We investigated the use of a PAF antagonist (PAF-a) in a canine model in reducing PAF-mediated pulmonary dysfunction following lung preservation and transplantation. Twelve combined heterotopic heart and orthotopic left lung allotransplantations were performed after 6 h of cold ischemia. Following administration of prostacyclin (PGI2), Euro-Collins solution (EC) was used for pulmonary artery flush in all donors, while in six animals the PAF-a, WEB 2170 BS, was administered to the donor (0.15 mg/kg for 30 min), to the storage solution (0.3 mg/kg) and to the recipient during reperfusion for a total of 6 h (0.3 mg/kg per h) EC/PAF-a). In all donors myocardial preservation was achieved using St. Thomas Hospital solution. Postoperatively, cardiorespiratory function was evaluated separately for donor and recipient organs at an FiO2 of 0.4 for a maximum of 12 h. The quality of lung preservation was assessed by means of postoperative oxygenation (pO2), pulmonary artery pressure (PAP) and pulmonary vascular resistance index (PVRI). In the EC/PAF-a group, pO2 of the donor lung was significantly elevated (P < 0.01) and PVRI was significantly lower (P < 0.05) when compared to the EC group, while PAP showed no significant differences between both groups and throughout the entire postoperative course. We concluded that a significant improvement in the current clinical standard for lung preservation could be obtained by the application of WEB 2170 BS in combination with EC flush as demonstrated by improved oxygenation and lower PVRI of the transplantated organs.

Lung and heart-lung transplantation

Unilateral lung transplantation has become a successful method for the treatment of end-stage pulmonary disease, whereas double-lung transplantation has provided benefit to patients with nonfibrotic lung disease such as emphysema and cystic fibrosis. In the past 5 years, 16 single-lung and 13 double-lung transplantations have been performed by the Toronto Lung Transplant Group in patients with end-stage lung disease. Seven perioperative and two late deaths have been recorded so far. Since the introduction of heart-lung transplantation at Stanford in 1981 and at Pittsburgh in 1982 for the treatment of Eisenmenger's syndrome and terminal pulmonary vascular disease, more than 350 combined heart-lung transplantations have been carried out throughout the world. Presently, the 2-year actuarial survival is about 62%. The long-term results have not yet reached the same level of success as those of cardiac transplantation alone. Although several factors have played a role in this difference, a prominent cause has been the lack of a reliable and simple method for pulmonary protection against prolonged ischemia. Most of the techniques proposed against ischemia can be classified as normothermic or static hypothermic cardiopulmonary preservation. The use of the normothermic method has not always been successful. For this reason, interest has now been directed toward the potential for hypothermic preservation of the heart-lung bloc and the use of free-radical scavenger therapy in the reduction of reperfusion injury.

Response to allopurinol pretreatment in a swine model of heart-lung transplantation

The role of allopurinol in the prevention of ischemia-reperfusion injury was assessed in a model of heart-lung transplantation. Fourteen swine were divided into two groups (seven donors and seven recipients). All heart and lung blocks were placed in hypothermic storage after perfusion with cold iso-osmolar cardioplegic solution and modified Collins solution, respectively (t = 8-10 degrees C for heart and t = 16-18 degrees C for lungs). The total ischemic time including the orthotopic transplantation was 6 h. Animals (donors and recipients) were pretreated with allopurinol given orally at a dosage of 50 mg/kg for 4 days. Animals were assessed by monitoring heart and lung function, including extravascular lung water at three time intervals, which included pretransplantation (donor), and 30 min and 2 h posttransplantation (recipient). Erythrocyte peroxidation susceptibility was assessed for 3 days, and surgery was performed on day 4. The malondialdehyde levels determined from erythrocyte exposure to in vitro peroxidative challenge classified three paired donor and recipient animals as responders and four paired donor and recipient animals as nonresponders to the allopurinol pretreatment. A persistent deterioration of lung function was observed over time in nonresponders (p less than .05) (increase of lung water, decrease of partial pressure of oxygen, increase in alveolar-arterial gradient, and decrease in arterial-alveolar tension ratio). Responders showed no significant alterations in lung function. This study in swine, a species devoid of myocardial xanthine oxidase activity, indicates that allopurinol may have a mechanism of action other than xanthine oxidase inhibition in the prevention of ischemia-reperfusion injury. The parallelism between protection of lung function and of red blood cells suggests the involvement of a generalized increase in tissue antioxidant capacity.

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.

Core-cooling, heart-perfusion, lung-immersion technique provides successful cardiopulmonary preservation for heart-lung transplantation

Mongrel dogs underwent heterotopic heart-orthotopic left lung transplantation. In Group I (N = 6), donor organs procured following core cooling to 15 degrees C on cardiopulmonary bypass (CPB) with cardioplegic arrest were immediately transplanted. In Group II (N = 6), following cardioplegic arrest without CPB core-cooling, the pulmonary artery was flushed with modified Collins' solution. Heart-lung blocks were immersed in extracellular solution for 6 hours and then transplanted. In Groups III and IV (N = 6 each), following CPB core-cooling to 15 degrees C and cardioplegic arrest, the organ blocks were immersed in extracellular solution (Group III) and the heart was perfused with oxygenated extracellular solution (Group IV). Evaluation of lung function using differences in arterial oxygen tension between the left and right atria demonstrated no differences between groups. However, extravascular lung water and pulmonary vascular resistance were significantly elevated in Group II. Cardiac function assessed by the ratio of end-systolic pressure to end-systolic dimension was significantly better in Group IV than in Groups II and III. Thus, adequate 6-hour hypothermic cardiopulmonary preservation with core cooling plus heart perfusion can be achieved for heart-lung transplantation.

Heterotopic heart-unilateral left lung transplantation in dogs

A technique is presented for transplantation of the heart and left lung in the canine model. Preservation of the recipient's heart and right lung allowed heterotopic en bloc transplantation of the donor organs, thus preserving the normal respiratory pattern and obviating the need for cardiopulmonary bypass. Four experiments were performed to develop the surgical technique. The mean survival of the remaining 10 dogs studied was 23 +/- 28 days (range 3 to 91 days). The transplanted heart and lung could be investigated as in orthotopic heart-lung transplantation; bronchoscopy with bronchoalveolar lavage and endobrachial biopsy as well as endomyocardial biopsy were performed by standard approaches. This model is suitable for physiological and immunological long-term observations of cardiopulmonary transplantation in dogs.