The superiority of an extracellular fluid solution over Euro-Collins' solution for pulmonary preservation

Supercooling: A Promising Technique for Prolonged Organ Preservation in Solid Organ Transplantation, and Early Perspectives in Vascularized Composite Allografts

Ex-vivo preservation of transplanted organs is undergoing spectacular advances. Machine perfusion is now used in common practice for abdominal and thoracic organ transportation and preservation, and early results are in favor of substantially improved outcomes. It is based on decreasing ischemia-reperfusion phenomena by providing physiological or sub-physiological conditions until transplantation. Alternatively, supercooling techniques involving static preservation at negative temperatures while avoiding ice formation have shown encouraging results in solid organs. Here, the rationale is to decrease the organ's metabolism and need for oxygen and nutrients, allowing for extended preservation durations. The aim of this work is to review all advances of supercooling in transplantation, browsing the literature for each organ. A specific objective was also to study the initial evidence, the prospects, and potential applications of supercooling preservation in Vascularized Composite Allotransplantation (VCA). This complex entity needs a substantial effort to improve long-term outcomes, marked by chronic rejection. Improving preservation techniques is critical to ensure the favorable evolution of VCAs, and supercooling techniques could greatly participate in these advances.

Ebselen Preserves Tissue-Engineered Cell Sheets and their Stem Cells in Hypothermic Conditions

Clinical trials have been performed using autologous tissue-engineered epithelial cell sheets for corneal regenerative medicine. To improve stem cell-based therapy for convenient clinical practice, new techniques are required for preserving reconstructed tissues and their stem/progenitor cells until they are ready for use. In the present study, we screened potential preservative agents and developed a novel medium for preserving the cell sheets and their stem/progenitor cells; the effects were evaluated with a luciferase-based viability assay. Nrf2 activators, specifically ebselen, could maintain high ATP levels during preservation. Ebselen also showed a strong influence on maintenance of the viability, morphology, and stem cell function of the cell sheets preserved under hypothermia by protecting them from reactive oxygen species-induced damage. Furthermore, ebselen drastically improved the preservation performance of human cornea tissues and their stem cells. Therefore, ebselen shows good potential as a useful preservation agent in regenerative medicine as well as in cornea transplantation.

Modelo experimental de perfusão pulmonar isolada em ratos: técnica e aplicações em estudos de preservação pulmonar

Estudos de preservação pulmonar em modelos experimentais realizados em animais de pequeno porte são de realização mais simples e barata. Esta comunicação tem o enfoque de descrever tecnicamente um modelo de perfusão pulmonar ex vivo em ratos, com o uso de um equipamento disponível comercialmente que foi o primeiro a ser instalado em um laboratório de pesquisa em cirurgia torácica no Brasil. Descrevemos detalhadamente o modelo e sua preparação, assim como suas aplicações para estudos de preservação pulmonar. Os detalhes técnicos da preparação podem ser observados também em um vídeo postado no site do Jornal Brasileiro de Pneumologia.

Preservation solution for lung transplantation

Despite the increasing success of lung transplantation as the mainstay therapeutic modality for end-stage lung disease, the 1-year survival rate after lung transplantation remains 80% and primary graft dysfunction (PGD) accounts for 30% of mortality. Ischemia-reperfusion injury has been identified as one of the main causes of PGD, and thus significant efforts have been made to optimize the methods for lung preservation in an attempt to minimize lung injury during the period of ischemia. The composition of the lung preservation solution used in the pulmonary artery flush has been considered to be the key to successful lung preservation, and many lung transplant programs have been shifting the use of the preservation solution from the intracellular fluid type to the extracellular fluid type because of preferable posttransplant lung function with the latter. This review summarizes the experimental and clinical studies on lung preservation, particularly focusing attention on the preservation solution being employed for clinical lung transplantation.

Risk factors for early primary graft dysfunction after lung transplantation: a registry study

BACKGROUND

Primary graft dysfunction (PGD) is a leading cause of early morbidity and mortality in lung transplantation. We sought to identify risk factors for PGD using the United Network for Organ Sharing/International Society for Heart and Lung Transplant (UNOS/ISHLT) Registry.

METHODS

A total of 6984 lung transplants between 1994 and 2002 were available for analysis. Potential risk factors were tested for association with PGD and multivariable logistic regression was applied to adjust for confounding.

RESULTS

The overall incidence of PGD was 10.7% (95% CI 9.9-11.4). In multivariable analyses, factors independently associated with PGD were donor age >45 yr (p < 0.001); donor head trauma (p = 0.03); recipient body mass index >25 kg/m(2) (p = 0.005); recipient female gender (p = 0.001); use of Eurocollins preservation solution (p = 0.001); single lung transplant (p = 0.005); increased ischemic time (p < 0.001); and elevated recipient pulmonary artery systolic pressure at transplant (p < 0.001). Recipient transplant diagnosis was strongly associated with PGD, with primary or secondary pulmonary hypertension (p < 0.001 for both), and idiopathic (p < 0.001) or secondary pulmonary fibrosis (p = 0.011) as significant and independent risk factors for PGD.

CONCLUSIONS

Risk factors for PGD in the UNOS/ISHLT registry are consistent with prior smaller studies. Recipient, donor, and therapy variables are independently associated with PGD, as defined in a large registry.

Comparison of canine single and sequential bilateral lung transplant model for lung preservation study

The purpose of this study was to compare canine sequential bilateral lung transplantation (SBLT) with left single lung transplant (LSLT) models. After 24 hours of lung preservation with low potassium/dextran glucose (LPDG) solution, seven SBLT procedures were performed using mongrel dogs. The comparative group including nine cases of LSLT. After completion of each transplant, the dogs were maintained on a ventilator for 3 hours. Thereafter serial hemodynamics were evaluated with recipients with chest X-ray, computed tomography, and lung perfusion scan checked at 2 hours after transplantation. Pathological evaluations were also performed. Five of seven SBLT successfully completed the whole assessment, all LSLT survived. In SBLT, pulmonary arterial pressure and pulmonary vascular resistance were significantly elevated, but recovered 3 hours after reperfusion. The ultrastructural aspects of alveolae and pulmonary artery endothelium showed a reversible mild injury 24 hours after lung preservation and reperfusion. The present study suggests that the canine SBLT model using LPDG solution provides an excellent preservation effect and is more physiological as the dog is completely dependent on the function of the transplanted lung.

Perfadex for clinical lung procurement: is it an advance?

BACKGROUND

Extensive laboratory experience suggested that low potassium dextran lung preservation solution (Perfadex; Medisan, Uppsala, Sweden) is superior to Euro-Collins (EC; Frusen, Hamburg, Germany), the clinical standard. The purpose of this study was to evaluate Perfadex in clinical lung transplantation.

METHODS

A retrospective analysis of the outcome of 69 consecutive lung allografts retrieved and used for transplantation was made. Donor lungs were flushed with EC in 37 patients and Perfadex in 32 patients. The evaluation measurements were quantitative chest roentgenogram score (grade 0 to 4), graft oxygenation, duration of mechanical ventilation, length of intensive care treatment, and survival.

RESULTS

The mean chest roentgenogram score was 1.55 and 1.81 for the EC group compared with 1.18 and 2.09 for the Perfadex group at 1 and 48 hours, respectively (p = 0.1 and 0.8, respectively). Arterial alveolar oxygen tension ratio was similar at 12 and 24 hours (0.61 vs 0.67; p = 0.8; and 0.64 vs 0.53; p = 0.3, respectively). The mean ventilation time was 71.2 +/- 32.3 hours versus 81.9 +/- 43.6 hours for the EC and Perfadex groups, respectively (p = 0.4). The mean intensive therapy unit stay was 3.1 +/- 2.6 days for the EC group compared with 4.1 +/- 3.9 days for the Perfadex group (p = 0.4). Death caused by primary organ failure was 5.1% for the EC group compared with 3.1% for the Perfadex group (p = 0.8).

CONCLUSIONS

There was no difference between Perfadex and EC in clinical lung preservation. This may reflect the difference between controlled laboratory environment and the real world of brain death lung injury. Further studies are required to investigate the impact of Perfadex in the long-term outcome of lung transplantation.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Influence of high molecular dextrans on lung function in an ex vivo porcine lung model

BACKGROUND

Extracellular preservation solutions utilizing high molecular agents can reduce intracellular edema during ischemia/reperfusion in lung transplantation. A solution of 40,000 dalton molecular weight (DMW) has already been clinically established (Perfadex). However, it is unclear whether dextrans of this particular size represent the optimal additive for lung preservation solutions.

MATERIALS AND METHODS

In a new ex vivo porcine lung model, lungs were each preserved with low-potassium solutions containing 5% dextran with 90,000 DMW (Dex 90) and 160,000 DMW (Dex 160) and with Perfadex (40,000 DMW). After 24 h of cold ischemia, reperfusion was performed employing a roller pump with a pulsatile module. Lungs were perfused with deoxygenated perfusate and ventilated with room air. The oxygenation capacity (Delta pO(2)), peak inspiratory pressure (PIP), and mean pulmonary artery pressure (PAP) were monitored for 60 min. Net weight gain (NWG) and wet-to-dry ratio (W/D ratio) were determined. Free-radical generation was assessed by measuring malondialdehyde (MDA) at 10, 30, and 50 min.

RESULTS

PIP and PAP increased in all groups significantly during reperfusion. However, Dex 160-perfused lungs exhibited significantly higher values than those with Dex 90 and Perfadex. Perfadex showed the highest Delta pO(2) throughout the entire reperfusion, while Delta pO(2) was slightly reduced in Dex 160 and significantly lower in Dex 90. In Perfadex the lowest water content was observed assessed by NWG and W/D ratio. The highest MDA values were observed in Dex 90, followed by Dex 160, while the lowest values were seen in Perfadex.

CONCLUSIONS

Preservation of the lung with Perfadex exhibited superior postischemic function in contrast to preservation solutions containing dextrans with a higher molecular weight.

Influence of preservation solution on early graft failure in clinical lung transplantation

The aim of this study was to assess the influence of preservation solution type and extra- or intracellular composition on the occurrence of early graft dysfunction after clinical lung transplantation. For 170 patients who underwent a single (n = 124) or bilateral (n = 46) lung transplantation in two centers in Paris between 1988 and 1999, the preservation technique applied to the donor lung was single-flush perfusion of the pulmonary artery with one of several solutions of intracellular (Euro-Collins, n = 61; University of Wisconsin, n = 24) or extracellular composition (Cambridge, n = 64; Celsior, n = 21). The early postoperative outcome of these patients was reviewed. Reimplantation edema occurred in 48% of all patients, and the overall 1-mo survival rate was 84%. No significant difference in the incidence of edema, duration of mechanical ventilation, and 1-mo survival rate was observed between the four groups or between intra- and extracellular groups. After adjustment for graft ischemic time by means of multivariate analysis, the use of extracellular preservation fluid was associated with a lower incidence of reimplantation edema without effect on 1-mo mortality. Graft ischemic time was associated with both edema occurrence and 1-mo survival rate (p = 0.02 and p = 0.01, respectively). We conclude that extracellular-type solutions are associated with better lung preservation than intracellular-type solutions in clinical transplantation.

Cardiac transplantation following a 24-h preservation using a perfusion apparatus

BACKGROUND

We developed a new apparatus for heart preservation and have already reported successful transplantation following 12 h of preservation using this apparatus. The efficacy of coronary perfusion with an oxygenated Celsior solution was investigated through transplantation following 24 h of preservation using the apparatus.

MATERIALS AND METHODS

After being harvested, grafts were preserved with a combination of immersion in a 4 degrees C Celsior solution and perfusion with an oxygenated Celsior solution using the apparatus in the coronary perfusion (CP) group and simply immersed in a 4 degrees C Celsior solution in the simple immersion(SI) group. beta-Adenosine triphosphate (beta-ATP), phosphocreatine (Pcr), and inorganic phosphate (P(i)) levels and myocardial pH (pH(i)) were measured immediately after the heart was excised and at 12 and 24 h after preservation. Following preservation, orthotopic transplantation was performed. Cardiac function was measured 2 h after weaning from cardiopulmonary bypass (CPB).

RESULTS

beta-ATP/P(i), Pcr/P(i), and pH(i) levels were significantly higher in the CP group than in the SI group at 12 and 24 h after preservation. Four of six animals in the CP group and two of six in the SI group were successfully weaned from CPB. The recovery rates of cardiac function were better in the CP group than in the SI group.

CONCLUSION

Twenty-four hours of heart preservation may be possible with a combination of immersion in a 4 degrees C Celsior solution and perfusion with an oxygenated Celsior solution using the perfusion apparatus.

Current strategies in lung preservation

Current methods of lung preservation allow for effective, expeditious transplantation as a treatment for end-stage pulmonary disease. However, the utilization of hypothermia, hyperkalemia, and pulmonary artery distension as a single rapid flush for perfusion is less than ideal. All these interventions result in increased pulmonary vascular resistance and suboptimal preservation of lung function. The ability to preserve lungs for longer time intervals and with less risk of tissue injury would provide significant advantages. There would be a greater likelihood that rare size or blood types could find matches by enlarging the area of organ distribution. Optimal preservation would also improve the perioperative outcomes in regard to primary graft failure and subsequently reduce the later complication of chronic rejection and graft lung dysfunction. Finally, through a better understanding of the mechanisms of lung injury during preservation and by developing means to limit the injury, it would be possible to utilize organs from donors that at this time would not be considered optimal. This would increase the donor pool without compromising the recipient's outcome.

A novel cell culture model for studying ischemia-reperfusion injury in lung transplantation

Many cell culture models have been developed to study ischemia-reperfusion injury; however, none is specific to the conditions of lung preservation and transplantation. The objective of this study was to design a cell culture model that mimics clinical lung transplantation, in which preservation is aerobic and hypothermic. A549 cells, a human pulmonary epithelial cell line, were preserved in 100% O(2) at 4 degrees C for varying periods in low-potassium dextran glucose solution, simulating ischemia, followed by the introduction of warm (37 degrees C) DMEM plus 10% fetal bovine serum to simulate reperfusion. Cultures were assayed for cell attachment and viability. Sequential extension of ischemic times to 24 h showed a time-dependent loss of cells. There was a further decrease in cell number after simulated reperfusion. Cell detachment was due mainly to cell death, as determined by cell viability. The effects of chemical components such as dextran 40 and calcium in the preservation solution and various preservation gas mixtures were examined by use of this model system. With its design and validation, this model could be used to study mechanisms related to ischemia-reperfusion injury at the cellular and molecular level.

Effects of EP4 solution and LPD solution vs Euro-Collins solution on Na(+)/K(+)-ATPase activity in rat alveolar type II cells and human alveolar epithelial cell line A549 cells

BACKGROUND

Intact alveolar epithelial Na(+)/K(+)- adenosinetriphosphatase (ATPase) function is important in preventing alveolar fluid accumulation after lung transplantation. We examined whether the type of preservation solution used influences Na(+)/K(+)-ATPase activity in alveolar epithelial cells.

METHODS

Rat alveolar type II cells were preserved with EP4, low-potassium dextran (LPD), or Euro-Collins solution at 7 degrees C for 5 and 20 hours. To assess cell toxicity, we measured cell viability and lactate dehydrogenase release. Na(+)/K(+)-ATPase activity was measured as ouabain-sensitive ATPase hydrolysis. We also examined the effect of terbutaline (10(-3) mol/liter) and dibutyryl cyclic adenosine monophosphate (dbcAMP) (10(-3) mol/liter) on Na(+)/K(+)-ATPase activity in A549 cells preserved for 5 hours.

RESULTS

All solutions caused significant damage of rat alveolar type II cells at 20 hours. However, Na(+)/K(+)-ATPase activity was preserved at normal levels with EP4 and LPD over 20 hours. Terbutaline and dbcAMP significantly increased Na(+)/K(+)-ATPase activity in A549 cells preserved with EP4 and LPD solutions for 5 hours. However, we observed no activation in the cells preserved with Euro-Collins solution. We found no significant difference in intracellular cAMP levels after terbutaline challenge among the types of preservation solution.

CONCLUSIONS

We conclude that extracellular-type solutions such as EP4 and LPD may be preferable for maintaining not only the basal activity but also the ability to activate Na(+)/K(+)-ATPase in response to beta-adrenergic agonists, in alveolar epithelial cells.

Comparison of university of wisconsin, euro-collins, low-potassium dextran, and krebs-henseleit solutions for hypothermic lung preservation

OBJECTIVE

We sought to test the effectiveness of 4 different solutions for hypothermic rat lung preservation.

METHODS

One hundred ninety-two rats were used. The rats were divided into 4 groups, and University of Wisconsin, Euro-Collins, low-potassium dextran, or Krebs-Henseleit solution was used in each group. They were further divided into 6 subgroups of 8 rats each. The lungs were preserved at 4 degrees C for 0, 4, 6, 8, 12, or 24 hours, respectively, and lung function was studied by using a living rat perfusion model.

RESULTS

Pulmonary arterial flow decreased in each group after 4 to 6 hours of preservation; the low-potassium dextran group decreased the least and the Krebs-Henseleit group decreased the most. Pulmonary vascular resistance increased in each group after 6 hours of preservation; the Krebs-Henseleit group increased the most. Although airway pressure increased, static lung compliance and gas exchange capacity decreased after 8 hours of preservation; the Krebs-Henseleit group exhibited the worst values. Lung tissue wet/dry weight ratio increased gradually during preservation; the University of Wisconsin group exhibited the least increase. An ultrastructural study indicated the least morphologic changes in the low-potassium dextran group at 24 hours.

CONCLUSIONS

At 4 degrees C, all solutions preserved rat lungs for 4 hours with acceptable function. However, 6 hours of preservation resulted in damaged pulmonary function in some lungs, and this damage increased when preservation time was extended. The lungs preserved in low-potassium dextran solution had the best overall function, but the lungs preserved in University of Wisconsin solution had less edema.

Overview and future practice patterns in cardiac and pulmonary preservation

Heart and lung transplantation have become standard therapy for many patients with end-stage heart and lung disease. Successful transplantation requires preservation of allografts until they can be implanted and reperfused. In the decades since the transplantation of thoracic organs became a clinical reality, many advances have been made in preoperative donor management, procurement, and preservation techniques. This article summarizes the state of the art in heart and lung preservation and review some of the areas of current research that may lead to improvements in preservation techniques in the future.

Heart and lung preservation for transplantation

Since the beginning of transplantation the search for optimal means of organ preservation has been ongoing. One of the major causes of death early following heart or lung transplantation is graft failure. Factors that play a role in this problem include recipient and donor issues, but clearly procurement techniques and preservation solutions are important. This article summarizes the history, current clinical practice, and research devoted to heart and lung preservation for transplantation.

Ischemic preconditioning enhances donor lung preservation in the rabbit

OBJECTIVE

Ischemic preconditioning achieved by brief periods of ischemia followed by reperfusion before a prolonged period of ischemia, is well known to reduce myocardial damage. We investigated whether ischemic preconditioning of the lung could also attenuate ischemia-reperfusion injury following pulmonary preservation.

METHODS

Transient ischemia of the right lung was achieved in rabbits (n = 4 in each group) by occluding the main bronchus and pulmonary artery, followed by reperfusion according to a protocol that differed between study groups: group 1 (control), 45 min ventilation; group 2, 30 min ventilation, 5 min ischemia and 10 min reperfusion; group 3, three periods of 5 min ischemia and 10 min reperfusion; group 4, five periods of 3 min ischemia and 6 min reperfusion. Donor lungs were then flushed with a crystalloid solution followed by inflated storage at 37 degrees C for 2 h. The function of the right lung was assessed during reperfusion for 2 h with homologous, diluted and deoxygenated blood in an isolated, pressure-limited, and room-air ventilated model.

RESULTS

Significant differences (P < 0.0001) were observed between groups 1 and 2 vs. groups 3 and 4 in veno-arterial oxygen pressure gradient (29 +/- 6 and 24 +/- 6 mmHg vs. 124 +/- 24 and 132 +/- 14 mmHg, respectively), and in weight gain (88 +/- 13 and 98 +/- 13% vs. 44 +/- 9 and 29 +/- 3%, respectively) after 1 h of reperfusion, and in wet-to-dry weight ratio (15.5 +/- 1.5 and 14.3 +/- 0.4 vs. 10.1 +/- 1.6 and 9.0 +/- 0.8, respectively) at the end of reperfusion. No significant differences in any of these parameters were observed between group 1 vs. group 2 neither between group 3 vs. group 4.

CONCLUSIONS

These data suggest: (1) That 15 min, but not 5 min of transient ischemia prior to pulmonary preservation can significantly reduce edema in the lung graft upon reperfusion, thus improving oxygenation capacity and (2) although not significant, this beneficial effect seems to be slightly better with more repetitive periods of transient ischemia. Further research is warranted to investigate whether ischemic preconditioning in the human organ donor may become a new strategy to protect lung tissue during a planned ischemic event as in pulmonary transplantation.

Lung procurement by low-potassium dextran and the effect on preservation injury. Munich Lung Transplant Group

BACKGROUND

This clinical study was performed to evaluate the effect of low-potassium dextran (LPD) solution on organ function in human lung transplantation.

METHODS

A total of 80 patients were included in this study. Donor lungs were flushed with Euro-Collins (EC) solution in 48 cases or LPD (Perfadex) in 32 cases. Subsequently, single- (EC: n = 31; LPD: n = 15) or double-lung transplantations (EC: n = 17; LPD: n = 17) were performed. The evaluation parameters of transplant function were the reperfusion injury score (grade I to V); the alveolar/arterial oxygen ratio; the duration of respirator therapy; and the length of intensive care treatment and survival.

RESULTS

Incidence and severity of reperfusion injury score were more severe in the EC group (31 of 48: grade I: n = 13; II: n = 8; III: n = 5; IV: n = 2; V: n = 3; LPD group: 17 of 32 patients; grade I: n = 12; II: n = 1; III: n = 3; IV: n = 0 grade V: n = 0), leading to death in three patients. In the LPD group, despite of the use of cardiopulmonary bypass, alveolar/arterial oxygen ratio values were significantly (P = 0.009) better during the early postoperative phase. Thirty-day mortality was 12% in the EC group and 6% in the LPD group. The one-year survival rate was 79% after the use of LPD (vs. EC: 62%).

CONCLUSIONS

Graft preservation using LPD leads to better immediate and intermediate graft function after pulmonary transplantation and also results in better long-term survival.

Beneficial effects of leukocyte-depleted blood and low-potassium dextran solutions on microvascular permeability in preserved porcine lung

Modified Euro-Collins (EC) solution, a crystalloid intracellular-type solution, has been commonly used for pulmonary preservation. Several experimental studies have shown the advantages of using extracellular colloid-based solutions. The aim of this study was to compare the quality of preservation of two extracellular colloid solutions, leukocyte-depleted blood (BL) and low-potassium dextran (LPD) solutions, with that of EC solution. Lungs of 22 domestic pigs were flushed and preserved with EC (n = 8), BL (n = 7), or LPD (n = 7) solution. After harvesting, one of the lungs was reperfused immediately in an ex vivo circuit (control lungs), whereas the contralateral lung was reperfused after 8 h of cold (4 degrees C) storage (preserved lungs). Besides the lung function parameters (gas exchange, pulmonary hemodynamics and mechanics), the permeability of the endothelial-epithelial barrier was assessed by determining the transferrin leak index (TLI) using a double radioisotopic method, by measuring the alveolar/arterial protein concentration ratio, and by analyzing histopathologic changes. The functional quality (oxygenation, airway resistance, dynamic compliance [CL, dyn]) of both BL and LPD lungs was slightly but significantly superior to that of EC lungs. However, pulmonary vascular resistance was lower in BL-preserved than in EC- or LPD-preserved lungs. The TLI was increased in EC control and preserved lungs, whereas it was low in BL and LPD control lungs and did not increase after preservation. The alveolar/arterial protein concentration ratio was not different between control groups, but was increased fourfold in EC-preserved compared with BL- or LPD-preserved lungs. Finally, EC-preserved lungs presented a weight gain about twice that of BL- and LPD-preserved lungs. Morphologic analysis confirmed these results, because in the EC-preserved lungs, rupture of alveolar septa and severe alveolar edema and hemorrhage were observed, whereas BL- and LPD-preserved lungs showed a relatively well-preserved structure. The results demonstrate that both BL and LPD flush solutions preserve the endothelial-epithelial barrier better than does EC solution. Although the quality of preservation is similar, pulmonary vascular resistance is higher in LPD-preserved than in BL-preserved lungs.

Effects of preservation of rat lungs in a hypothermic medium on alveolar morphology

The increasing use of organs such as liver, lung, heart, pancreas, kidney and small intestine for transplantation purposes necessitates the development of optimum preservation techniques. The aim of our study was to investigate time-related morphological changes in alveoli during preservation of rat lungs in hypothermic Euro-Collins solution. Lungs were perfused via the pulmonary arteries with Euro-Collins solution at a temp of 19 degrees C. Totally perfused lungs were placed in Euro-Collins solution and stored for 6, 12 and 24 h at 4 degrees C. Biopsies were taken and prepared for examination at the light and electron microscopical level. Light microscopic examination revealed good preservation of the alveoli after storage for 6 h and moderate damage of alveolar architecture after 12 h of preservation. Severe degeneration of alveoli was found after 24 h of storage. The main ultrastructural changes were observed in lungs stored for 12 h and 24 h. After 6 h of storage, tissue damage was not found. Pneumocytes type II lost their apical microvilli and lamellar bodies were electron-lucent, indicating lamellar degeneration after 12 and 24 h of storage. Pneumocytes type I were also damaged. Their cytoplasm contained many vacuoles. Endothelial lining of the capillaries was contracted. Endothelial cells also showed many vacuoles. Edema around the capillaries was observed. We conclude on the basis of our morphological study, that Euro-Collins solution at low temperature is a good preservative for a short period of time only, but serious tissue damage occurs after periods of preservation longer than 12 h.

Reliable 18-hour lung preservation with University of Wisconsin solution. An ex vivo rat model with a pulsatile perfusion system

OBJECTIVES

A common experimental model is necessary to assess therapeutic intervention in lung preservation. This study was designed to establish lung preservation in an ex vivo rat model that would enable post-storage lung function to be stably evaluated during the 2 hours following reperfusion.

SUBJECTS AND METHODS

Lungs isolated from Sprague-Dawley rats (n = 36) were flushed and stored in University of Wisconsin solution at 4 degrees C for the following periods: Group 1: no storage (n = 12); Group 2: 4 hours (n = 8); Group 3: 18 hours (n = 8); and Group 4: 24 hours (n = 8). After storage in University of Wisconsin solution, all lungs were reperfused with homologous venous blood exsanguinated from donor rats using a pulsatile perfusion system. Pulmonary variables, including lung airway resistance, dynamic lung compliance, total pulmonary vascular resistance, and blood gas analysis, were assessed during reperfusion.

RESULTS

All lungs stored for 24 hours failed within 1 hour of reperfusion. Lungs stored for up to 18 hours survived 2-hour reperfusion. pO2 in groups 1 to 3 (87.1 +/- 3.5, 89.7 +/- 2.4, and 80.6 +/- 6.4, pO2 mmHg at 30 minutes) was similar during reperfusion, but that in group 4 (49.5 +/- 4.6 mmHg, at 30 minutes) deteriorated within 30 minutes after reperfusion onset. Lung airway resistance, dynamic lung compliance, and shunt fraction also deteriorated in group 4, whereas these variables were similar in groups 1, 2, and 3 during reperfusion.

CONCLUSIONS

These results indicate that this experimental model provided a reliable evaluation of preserved lung function after 18-hour cold storage. Any therapeutic intervention for extending storage periods or ameliorating post-storage lung function is easily tested using this system.

A comparison of the new preservation solution Celsior to Euro-Collins and University of Wisconsin solutions in lung reperfusion injury

BACKGROUND

The lung is particularly susceptible to reperfusion injury, both experimentally and clinically after transplantation. The extracellular-type preservation solution Celsior, which has been predominantly studied in cardiac preservation, has components designed to prevent cell swelling, free radical injury, energy depletion, and calcium overload. Using an isolated blood-perfused rat lung model, we investigated whether Celsior would decrease preservation injury and improve lung function after cold ischemic storage and reperfusion compared to Euro-Collins (EC) and University of Wisconsin (UW) solutions.

METHODS

Lewis rat lungs were isolated, flushed with the respective cold preservation solution, and then stored at 4 degrees C for 6 or 12 hr. After ischemic storage, the lung block was suspended from a force transducer, ventilated with 100% O2, and reperfused for 90 min with fresh blood via a cannula in the pulmonary artery. Lung compliance, alveolar-arterial oxygen difference, and outflow oxygen tension were all measured. The capillary filtration coefficient (Kf), a sensitive measure of changes in microvascular permeability, was determined.

RESULTS

For 6 hr of cold storage, lungs stored in Celsior had lower Kf values than those stored in EC, indicating decreased microvascular permeability. No other significant differences were noted between Celsior and EC or UW. For 12 hr of cold storage, Celsior provided increased oxygenation, decreased alveolar-arterial O2 differences, increased compliance, and decreased Kf values as compared to both EC and UW.

CONCLUSIONS

Celsior provides better lung preservation than EC or UW as demonstrated by increased oxygenation, decreased capillary permeability, and improved lung compliance, particularly at 12-hr storage times. These results are highly relevant, inasmuch as EC and UW are the most common clinically used lung preservation solutions. Further studies of Celsior in experimental and clinical lung transplantation, as well as in other solid organs, are indicated.

Evaluation of 18-hour lung preservation with oxygenated blood for optimal oxygen delivery

BACKGROUND

Previous studies have shown that availability of oxygen during lung preservation to maintain aerobic metabolism may be essential for the optimal viability of preserved lung tissue. The purpose of this study was to evaluate lung preservation with oxygenated blood for optimal oxygen delivery to the lung graft in a rabbit model.

METHODS

Eighteen excised rabbit lungs were flushed and stored for 18 hours at 10 degrees C with one of the following: Euro-Collins solution (EC; n=6), oxygenated homologous blood (OB; n=6), or low-potassium dextran solution (LPD; n=6). Poststorage lung functions were evaluated with isolated, blood-perfused lung model for 10 minutes.

RESULTS

The mean oxygen tensions after reperfusion for the EC, OB, and LPD groups (47.0+/-2.8, 76.9+/-13.1, 96.2+/-10.9 mm Hg at 10 minutes, respectively) were significantly different throughout the perfusion period (EC < OB < LPD, p < 0.05; EC < LPD, p < 0.01). Pulmonary artery pressure during the reperfusion period in the EC group (35.8+/-4.4 mm Hg at 10 minutes) was higher than that in the OB and LPD groups (29.8+/-4.3 and 22.4+/-2.2 mm Hg, respectively) (EC > OB, EC > LPD, p < 0.05). However, the E-selectin level in the reperfused blood in the OB group (5.04+/-0.24 ng/mL) was significantly elevated compared with that in other groups (EC, 3.56+/-0.54; LPD, 2.92+/-0.35 ng/mL, p < 0.05), which indicated enhanced neutrophil recruitment in the OB group. Comparisons of thrombomodulin and endothelin among the three groups did not reach statistical significance.

CONCLUSIONS

We conclude that OB may enhance lung preservation as compared with EC solution, probably through its enriched oxygen delivery during storage and extracellular composition. However, the availability of oxygenated blood does not exceed that of LPD solution because of augmented neutrophil recruitment, which may activate neutrophil-endothelial interactions.

The relationship of ischemia-reperfusion injury of transplanted lung and the up-regulation of major histocompatibility complex II on host peripheral lymphocytes

OBJECTIVES

This study was designed to examine the relationship between ex vivo preservation time of the transplanted lung and the extent of injury and to relate this to the severity of rejection with and without allogenicity.

METHODS

Single lung transplantation was performed on two groups of domestic swine. Group A (n = 7) and group B (n = 6) had ex vivo preservation times of 4 and 15 hours, respectively, at 4 degrees C hypothermia. Group C (n = 6) underwent 2 hours of warm ischemia via dissection and isolation of the left lung with ligation of its bronchial artery and crossclamping of the left pulmonary artery, vein, and bronchus without explantation. Assessment measures included lung function, antioxidant enzyme activities in the plasma and lung tissue, levels of inflammatory mediators in the recipient plasma, and quantification of major histocompatibility complex II HLA-DR-beta on host peripheral lymphocytes.

RESULTS

All groups demonstrated increases in interleukin-10, lung weight, and HLA-DR-1beta expression and decreases in lung-tissue antioxidant enzyme activities, gas exchange, and lung compliance. There was a strong positive correlation between ex vivo preservation time and the expression of HLA-DR-beta and a negative correlation between ischemic time and lung-tissue superoxide dismutase.

CONCLUSIONS

These results suggest that the intensity of the host immunogenic response is related to the severity of ischemia-reperfusion injury and is independent of tissue incompatibility and/or the type of ischemic insult. We conclude that the extension of ex vivo preservation time may predispose the transplanted lung to more severe rejection.

Reduced lipid peroxidation and ischemia-reperfusion injury after lung transplantation using low-potassium dextran solution for lung preservation

Ischemia-reperfusion injury is one of the significant problems in clinical lung transplantation. We investigated the effect of lung preservation with Euro-Collins solution (EC group) or low-potassium dextran solution (LPD group) on lipid peroxidation and ischemia-reperfusion injury in a pig model of lung allotransplantation. The donor lungs were preserved at 4 degrees C for 18 h. Left-sided single lung transplantation was performed, followed by 6 h of reperfusion. Lipid peroxidation was measured as thiobarbituric acid-reactive materials (TBARM) in bronchoalveolar lavage (BAL) fluid and effluent solutions from pulmonary artery (Effluent). After 18 h of ischemia, the LPD group showed lower TBARM in BAL and Effluent than the EC group (p < 0.05). After ischemia plus reperfusion, lung wetto-dry weight ratios and TBARM levels in BAL in the LPD group were lower than those of the EC group (p < 0.05). Lung wet-to-dry weight ratios correlated with TBARM levels in BAL (p < 0.05, r = 0.50). We conclude lipid peroxidation in BAL and Effluent may reflect the degree of ischemia-reperfusion injury, and lung preservation with LPD can reduce lipid peroxidation and lung injury as compared with EC.

Extended preservation of ischemic pulmonary graft by postmortem alveolar expansion

BACKGROUND

If lungs could be retrieved for transplantation from non-heart-beating cadavers, the shortage of donors might be significantly alleviated.

METHODS

Peak airway pressure, mean pulmonary artery pressure, pulmonary vascular resistance, and wet to dry weight ratio were measured during delayed hypothermic crystalloid flush in rabbit lungs (n = 6) at successive intervals after death comparing cadavers with lungs left deflated (group 1), inflated with room air (group 2) or 100% oxygen (group 4), or ventilated with room air (group 3), or 100% nitrogen (group 5), or 100% oxygen (group 6).

RESULTS

There was a gradual increase in mean pulmonary artery pressure and pulmonary vascular resistance with longer postmortem intervals in all study groups (p = not significant, group 1 versus group 2 versus group 3). There was also a gradual increase in peak airway pressure and wet-to-dry weight ratio over time in all groups, which reflected edema formation during flush (airway pressure, from 14.5 +/- 1.0 cm H2O to 53.7 +/- 12.2 cm H2O, and wet-to-dry weight ratio, from 3.6 +/- 0.1 to 11.5 +/- 1.2, in group 1 at 0 and 6 hours postmortem, respectively; p < 0.05). Compared with group 1, however, the increase in groups 2 and 3 was much slower (airway pressure, 20.9 +/- 0.5 cm H2O and 18.8 +/- 1.2 cm H2O, and wet-to-dry weight ratio, 5.2 +/- 0.3 and 4.6 +/- 0.4 at 6 hours postmortem, respectively; p < 0.05 versus group 1 and p = not significant, group 2 versus group 3). Airway pressure and wet-to-dry weight ratio did not differ between groups 2 and 4 or between groups 3, 5, and 6.

CONCLUSIONS

These data suggest that (1) pulmonary edema will develop in atelectatic lungs if hypothermic flush is delayed for 2 hours after death, (2) postmortem inflation is as good as ventilation in prolonging warm ischemic tolerance, (3) inflation with oxygen or ventilation with nitrogen or oxygen is no different from that with room air, and (4) therefore, prevention of alveolar collapse appears to be the critical factor in protecting the lung from warm ischemic damage independent of continued oxygen delivery.

Both blood and crystalloid-based extracellular solutions are superior to intracellular solutions for lung preservation

OBJECTIVE

Lung transplantation remains limited by donor organ ischemic time, inadequate graft preservation, and reperfusion injury. We evaluated lung preservation with use of an extracellular solution, with or without the addition of blood, as compared with preservation with the intracellular Euro-Collins solution.

METHODS

With use of an isolated, whole blood perfused/ventilated rabbit lung model, we studied three groups of animals. Lungs were flushed with Euro-Collins, low-potassium dextran, or 20% blood-low-potassium dextran solution. Lungs were harvested en bloc, stored inflated at 4 degrees C for 18 hours, and then reperfused at 60 ml/min with whole blood. Continuous measurements of pulmonary artery pressure, pulmonary vascular resistance, and dynamic airway compliance were obtained. Fresh, nonrecirculated venous blood was used to determine the single-pass pulmonary venous-arterial oxygen gradient.

RESULTS

Lungs preserved with Euro-Collins solution demonstrated elevated pulmonary artery pressure and pulmonary vascular resistance when compared with those preserved with low-potassium dextran and 20% blood-low-potassium dextran solutions (pulmonary artery pressure: 40.8 +/- 2.2 mm Hg vs 28.9 +/- 2.4 mm Hg and 28.3 +/- 1.5 mm Hg, respectively, p < 0.001; pulmonary vascular resistance: 46.0 +/- 3.1 x 10(3) dynes x sec x cm(-5) vs 29.0 +/- 4.2 x 10(3) dynes x sec x cm(-5) and 28.8 +/- 2.3 x 10(3) dynes x sec x cm(-5), respectively, p < 0.001). Euro-Collins solution-preserved lungs demonstrated a significant drop in compliance when compared with those preserved with low-potassium dextran and 20% blood-low-potassium dextran (-21.9% +/- 4.7% vs 1.8% +/- 3.3% and 1.4% +/- 6.2%, respectively; p = 0.002). Oxygenation was improved with low-potassium dextran and 20% blood-low-potassium dextran solutions as compared with that with Euro-Collins solution (296.3 +/- 54.6 mm Hg and 290.2 +/- 66.4 mm Hg, respectively, vs 37.2 +/- 4.6 mm Hg; p = 0.001).

CONCLUSIONS

Extracellular solutions provided superior preservation of pulmonary function in this rabbit lung model of ischemia-reperfusion. However, the addition of blood does not confer any demonstrable advantage over low-potassium dextran solution alone with use of an 18-hour period of cold ischemia.

Amelioration of pulmonary allograft injury by administering a second rinse solution

OBJECTIVE

The use of rinse solutions before reperfusing liver allografts has been shown to reduce cell death in rats. Carolina rinse solution (an extracellular solution that contains antioxidants, vasodilators, and other substrates that help prevent ischemia-reperfusion injury) has also been shown to improve liver function clinically in liver transplant recipients. This pilot study evaluates the value of a second pulmonary artery flush before reperfusion of a lung graft.

METHODS

Six groups of Sprague-Dawley rats (n = 6 each) were subjected to the following: Group 1 lungs were preserved with modified Euro-Collins solution followed by 24 hours of cold ischemia. Group 2 lungs were treated the same as group 1 but reperfused with blood. Group 3 lungs were preserved in Carolina rinse solution followed by 24 hours of cold ischemia. Group 4 lungs were treated the same as group 3 lungs and then reperfused with blood. Lungs in groups 5 and 6 were preserved with Euro-Collins solution, stored cold for 24 hours, and then rinsed with Euro-Collins or Carolina rinse solution, respectively, before reperfusion with blood. Lungs were subsequently stained with trypan blue solution for 5 minutes. Lung blocks were fixed and embedded in water-soluble methacrylate. Trypan blue--stained nuclei in nonviable endothelial cells and alveolar pneumocytes were counted in 10 different fields.

RESULTS

Groups 1 and 3, preserved with Euro-Collins and Carolina rinse solutions for 24 hours but not reperfused with blood, had significantly more viable endothelial cells (groups 1 and 3 vs group 2, p < 0.0001; group 3 vs group 4, p < 0.02) and pneumocytes (group 1 vs groups 2 and 4, group 3 versus group 2, p < 0.0001; group 3 vs group 4; p < 0.035) than groups 2 and 4, which were subsequently reperfused with blood. Groups 5 and 6, which received a second rinse, also had significantly more viable endothelial cells (p < 0.0005) and pneumocytes (p < 0.0001) than control groups, which were not rinsed before reperfusion.

CONCLUSIONS

We conclude that damage to pulmonary allografts resulting from prolonged ischemia is accentuated by reperfusion with blood. We also conclude that preservation with a single flush of Euro-Collins or Carolina rinse solution does not offer adequate protection, whereas a second rinse before reperfusion significantly decreases the number of damaged cells within the allograft.

Euro-Collins solution exacerbates lung injury in the setting of high-flow reperfusion

Single-lung transplantation has been abandoned for the treatment of pulmonary hypertension by many centers because of overperfusion of the graft following implantation. Euro-Collins solution is currently used for lung preservation despite the vasoconstrictive effect of this intracellular-type solution. We hypothesized that high-flow reperfusion, alone or in combination with Euro-Collins-induced vasoconstriction, may cause lung dysfunction. Twenty-eight New Zealand White rabbit lungs were harvested and studied in an isolated, blood-perfused model of lung function after 4 hours of cold ischemia. Control lungs were preserved with 50 ml/kg cold saline solution flush and reperfused at either normal flow (60 ml/min) or high flow (120 ml/min). Experimental lungs were preserved with 50 ml/kg cold Euro-Collins solution and reperfused at normal or high flow rates. The arteriovenous oxygen gradient at the end of the 30-minute reperfusion period was significantly lower in the high-flow versus the low-flow experimental group (31.1 +/- 4.2 vs 130.6 +/- 41.6 mm Hg, p < 0.05). The pulmonary vascular resistance was increased in the high-flow groups and the experimental groups, with a statistically significant difference between low-flow experimental and control groups (64374.4 +/- 5722.6 vs 37041.5 +/- 2110.9 dynes x sec x cm(-5), p < 0.001). The percentage decrease in dynamic airway compliance in the high-flow experimental group was markedly different from that in the high-flow control group (-51% +/- 13.3% vs -10.15% +/- 3.4%, p < 0.05). Similarly, the wet/dry ratio of the lungs in the high-flow experimental group (13.92 +/- 2.32) was significantly greater than that in the low-flow experimental group (6.27 +/- 0.19, p < 0.01) and than that in the high-flow control group (5.88 +/- 0.23, p < 0.001). These data demonstrate that high-flow reperfusion and preservation with Euro-Collins solution are deleterious to lung function, both individually and in combination, in an ex vivo rabbit lung model. Lung preservation with Euro-Collins solution may not be optimal when high-flow reperfusion is anticipated, as in the setting of unilateral lung transplantation for pulmonary hypertension.

Evaluation of a new solution containing trehalose for twenty-hour canine lung preservation

We examined the efficacy of two new preservation solutions containing trehalose--an extracellular type (ET-K) of solution and an intracellular type (IT-K) of solution--in relation to that of Euro-Collins (EC) solution in 20-h canine lung preservation. Canine lungs were flushed with one of the three solutions (n = 5 for each solution) after pretreatment with PGE1 (20 micrograms/kg) and were stored for 20 h at 4 degrees C. The left lungs were transplanted and evaluated to 6 h post transplant. In the ET-K group, the arterial oxygen tension after reperfusion was significantly higher than in the IT-K and EC groups. The pulmonary vascular resistance, wet/dry weight ratio, and histological evaluation of each transplanted lung in the ET-K group were also better than in the IT-K and EC groups. This indicates that ET-K solution is useful for 20-h preservation of canine lung grafts.

Low-potassium solution for lung preservation in the setting of high-flow reperfusion

BACKGROUND

We previously demonstrated that standard preservation using Euro-Collins solution impairs lung function in the setting of high-flow reperfusion because of potassium-induced vasoconstriction. Preservation strategies for single-lung transplantation are an important factor in patients with pulmonary hypertension. This study investigates the hypothesis that low-potassium preservation solution will improve function of lungs subjected to high-flow reperfusion.

METHODS

Twenty-one New Zealand white rabbit lungs were harvested and studied on an isolated, blood-perfused model of lung function after 4 hours of cold ischemia at 4 degrees C. Control lungs were preserved with 50 mL/kg of cold saline solution flush (group I). Experimental lungs were preserved with low-potassium solution (group II) or Euro-Collins solution (group III) at similar temperatures and volumes.

RESULTS

The pulmonary arteriovenous oxygen gradient at the end of the 30-minute high-flow reperfusion period was significantly higher in group II compared with group III (121.3 +/- 19.2 mm Hg versus 31.1 +/- 4.2 mm Hg; p < 0.001). The pulmonary vascular resistance was significantly lower in group II than in group III (46.3 +/- 1.8 x 10(3) dynes x s x cm(-5) versus 79.8 +/- 8.4 x 10(3) dynes x s x cm(-5); p < 0.01. The percent decrease in dynamic airway compliance in group III was significantly greater than in group I and II (-51.0% +/- 13.3% versus -10.2% +/- 3.4% and -11.2% +/- 2.8%, respectively; p < 0.001). Similarly, the wet to dry ratio of the lungs in group III was significantly greater than in groups I and II (13.9 +/- 2.3 versus 5.9 +/- 0.2 and 6.0 +/- 0.4, respectively; p < 0.001).

CONCLUSIONS

These data demonstrate that a low-potassium preservation solution yields improved lung function after high-flow reperfusion in an ex vivo rabbit lung model. Lung preservation should be aimed at the clinical setting.

Trehalose-containing solutions enhance preservation of cultured endothelial cells

BACKGROUND AND METHODS

We have developed two types of preservation solutions containing trehalose. ET-Kyoto solution (ET-K) is an extracellular type and IT-Kyoto solution (IT-K) is an intracellular type. In the present study we examined with in vitro assays the ability of ET-K, IT-K, Euro-Collins (EC), and University of Wisconsin (UW) solutions to preserve a murine endothelial cell line. The viability of cells stored in the solutions at 4 degrees C was determined by trypan blue exclusion and MTT assay.

RESULTS

Trypan blue exclusion showed the viability after 48 hours of cold storage to be 49.5 +/- 4.7% (mean +/- standard error) in ET-K, 59.5 +/- 0.7% in IT-K, 29.2 +/- 2.5% in EC, and 55.3 +/- 7.6% in UW (ET-K or UW versus EC, p < 0.05; IT-K versus EC, p < 0.01). MTT assay absorbance values for cells after 48 hours of cold storage were 0.366 +/- 0.0066 (mean +/- standard error) in ET-K, 0.358 +/- 0.0044 in IT-K, 0.336 +/- 0.011 in EC, and 0.362 +/- 0.0019 in UW (ET-K or UW versus EC, p < 0.05). After 120 hours, absorbance values for cells were 0.303 +/- 0.0038 in ET-K, 0.269 +/- 0.0034 in IT-K, 0.186 +/- 0.011 in EC, and 0.265 +/- 0.0066 in UW (ET-K versus UW, p < 0.05; ET-K versus IT-K, p < 0.01; ET-K, IT-K or UW versus EC, p < 0.01).

CONCLUSIONS

As far as the ability to preserve a murine endothelial cell line at a low temperature was concerned, the ET-K solution was superior to the UW solution, the IT-K solution and UW solution were equal, and the ET-K and IT-K solutions were superior to the EC solution.

Influence of pulmonary arterial pressure during flushing on lung preservation

The effect of changing pulmonary artery pressure during flushing (flushing pressure) on lung preservation was examined in an ex vivo rabbit lung perfusion model. Both lungs were flushed in situ with 200 ml of a preservation solution (extracellular fluid [ECF] type) at 8 degrees C, at a constant flushing pressure maintained by regulating the flushing flow rate from 20 to 120 ml/min. In the controls, the flushing pressure was maintained at 15 mmHg and the lungs were assessed without storage. In the other 5 groups (n = 7 in each group), the lungs were flushed at pressures of 5, 10, 15, 20, and 25 mmHg, respectively. The heart-lung block was then harvested, and immersed in the same solution at 8 degrees C for 24 hr. After 24 hr of storage, the block was reperfused with pooled venous blood for 10 min, and then with oxygenated blood for another 60 min in a closed circuit. Assessment of lung function included blood gas analysis of effluent blood, pulmonary artery pressure, airway pressure, wet:dry weight ratio, and histologic study. At flushing pressures of 5, 20, and 25 mmHg, uniform and clear flushing out of the pulmonary vascular beds was not obtained, resulting in postperfusion pulmonary hypofunction and a high incidence of pulmonary edema. However, at flushing pressures of 10-15 mmHg, we succeeded in completely flushing out the pulmonary vascular beds, and managed to preserve good pulmonary function. In conclusion, we determined the optimal flushing pressure for rabbit lung preservation to be 10-15 mmHg.

Perfadex is superior to Euro-Collins solution regarding 24-hour preservation of vascular function

BACKGROUND

The aim of this study was to compare Perfadex with Euro-Collins solution regarding 24-hour preservation of endothelium-dependent relaxation and vascular smooth muscle function.

METHODS

The infrarenal aorta of 72 isogenic rats was studied in organ baths as fresh controls, after 24 hours of cold (4 degrees C) storage, and after 24-hour storage followed by transplantation and examination after 7 or 30 days. The thromboxane A2 analogue U-46619 was used to test contractility. Acetylcholine chloride was used to elicit endothelium-dependent relaxation and papaverine hydrochloride, to elicit endothelium-independent relaxation.

RESULTS

With both solutions, all grafts were patent after 7 and 30 days. Vessels preserved in Euro-Collins solution for 24 hours lost 95% (p < 0.001) of their contractility compared with fresh controls; 7 days after transplantation, they had regained 40% of initial contractility, and after 30 days, there was no significant decrease in contractility. Vessels preserved in Perfadex manifested no significant decrease in contractility at any time. Endothelium-dependent relaxation could not be evaluated in vessels stored for 24 hours in Euro-Collins solution because they had lost almost all contractility; 7 days after transplantation, endothelium-dependent relaxation was reduced by 65% (p < 0.001), but at 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation. Vessels preserved in Perfadex for 24 hours lost 17% (p < 0.05) of endothelium-dependent relaxation, but 7 and 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation.

CONCLUSIONS

Perfadex, but not Euro-Collins solution, has the capacity to preserve vascular function after 24 hours of storage followed by in vivo reperfusion.

Impact of initial flush potassium concentration on the adequacy of lung preservation

The effects of initial lung flushing with intracellular and extracellular fluid type solutions were studied in lungs stored with the University of Wisconsin solution. Excised Sprague-Dawley rat lungs (n = 39) were flushed first with one of the following solutions: (1) the University of Wisconsin solution (K+ = 140 mmol/L), (2) modified (low potassium) University of Wisconsin solution (K+ = 20 mmol/L), (3) phosphate buffered saline solution (K+ = 3.9 mmol/L), (4) modified low-potassium phosphate-buffered saline solution (K+ = 20 mmol/L), (5) modified high-potassium phosphate-buffered saline solution (K+ = 40 mmol/L), and (6) Euro-Collins solution (K+ = 115 mmol/L) followed by secondary flush with storage solution and cold (4 degrees C) storage in University of Wisconsin solution for 24 hours. The lungs were then reperfused in the isolated, pulsatile, blood-perfused working lung system for 2 hours or until lung failure. Blood gas analysis and shunt fraction, aerodynamic parameters (airway resistance, lung compliance, elastic work, and flow resistive work), and total pulmonary vascular resistance were measured throughout the perfusion period. The mean oxygen tensions (in millimeters of mercury) at 30 minutes after the onset of reperfusion for University of Wisconsin solution, modified University of Wisconsin solution, phosphate-buffered saline solution, modified phosphate-buffered saline solutions (20 and 40 mmol/L), and Euro-Collins solution were 56.1 +/- 4.2, 72.7 +/- 9.1, 87.7 +/- 6.9 (p < 0.01 versus University of Wisconsin solution; p < 0.01 versus Euro-Collins solution), 86.0 +/- 9.6 (p < 0.01 versus University of Wisconsin solution; p < 0.01 versus Euro-Collins solution), 87.9 +/- 7.7 (p < 0.01 versus University of Wisconsin solution; p < 0.01 versus Euro-Collins solution), and 53.5 +/- 6.0, respectively. All aerodynamic parameters in the lungs flushed with extracellular fluid type solutions were superior to those flushed with intracellular fluid type solutions. We conclude that the efficacy of initial flushing was essential for successful lung preservation and that extracellular fluid type solutions were superior to intracellular fluid type solutions, at least for flushing the lung before storage with University of Wisconsin solution. Potassium concentration in flushing solution should be 20 mmol/L or less to obtain appropriate flushing and subsequent adequate distribution of the storage solution.

Successful canine bilateral single-lung transplantation after 21-hour lung preservation

A canine bilateral single-lung transplantation model was used to evaluate 21-hour lung preservation with low-potassium dextran glucose solution. Donor lungs were flushed with low-potassium dextran glucose solution (50 mL/kg), inflated with 100% oxygen (35 mL/kg), and preserved at 8 degrees C. Bilateral single-lung transplantation was performed without using cardiopulmonary bypass. The ischemic times to the right and left lungs were designed to be 3 and 6 hours, respectively, in group 1 (n = 5) and 18 and 21 hours in group 2 (n = 6). After bilateral single-lung transplantation, animals were maintained on a ventilator for 12 hours and lung function, including arterial blood gas and pulmonary hemodynamics, was measured. All 5 dogs in group 1 and 5 of 6 dogs in group 2 completed bilateral single-lung transplantation successfully and survived for 12 hours with excellent lung function. Arterial oxygen tension and mean pulmonary artery pressure were stable during the 12-hour assessment period in both groups and did not differ significantly from donor values. Twelve hours after reperfusion, mean arterial oxygen tension (inspired oxygen fraction = 1.0) was 590 +/- 18 mm Hg in group 1 and 604 +/- 8 mm Hg in group 2. After the 12-hour assessment period, the animals were extubated and immunosuppressed. Two dogs in group 2 survived for 7 and 8 days, respectively, with a mean arterial oxygen tension of 74 mm Hg on room air at 5 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of pH of preservation solution on lung viability

Recently, various solutions for organ preservation have been introduced. Despite much debate regarding the composition of preservation solutions, the ideal pH of a preservation solution has not been determined. We investigated the effects of the pH of a lung preservation solution on viability using an isolated, ventilated lung perfusion model. Initially, we performed flush perfusion with solutions of five different pH groups (6.60, 7.00, 7.40, 7.80 and 8.20, measured at 10 degrees C). Lungs perfused with pH 6.60 solution had a significantly higher pulmonary vascular resistance than those perfused with pH 7.40, 7.80 and 8.20 solutions. Blood was washed out completely and uniformly with solutions of pH 7.40 and 7.80. After preservation the arterial oxygen tension was significantly greater in pH 7.40 and 7.80 groups than in pH 6.60, 7.00, or 8.20 groups. Moreover, pulmonary artery pressure, airway pressure, and wet/dry weight ratios in the pH 7.40 and 7.80 groups were lower than in the others. We conclude that for both pulmonary flush and storage preservation, solutions of pH 7.40 to pH 7.80 are optimal for lung preservation.

Lung preservation with Euro-Collins, University of Wisconsin, Wallwork, and low-potassium-dextran solution. Université++ Paris-Sud Lung Transplant Group

Using isolated rat lungs, we compared prevention of ischemia-reperfusion injury provided by flushing the lungs with modified Euro-Collins solution (EC), University of Wisconsin solution (UW), low-potassium-dextran solution (LPD), or Wallwork solution (WA). After 4 hours' and 6 hours' cold ischemia, reperfusion injury was assessed on the basis of changes in filtration coefficients (Kfc) and pressure-flow curves, characterized by the slope of the curves (incremental resistance) and the extrapolation of this slope to zero flow (pulmonary pressure intercept [Ppi]). After 4 hours, Kfc and Ppi were higher with EC than with UW, LPD, and WA, and the incremental resistance was higher with EC and UW. After 6 hours, Kfc and incremental resistance Ppi were higher with LPD than with WA. Because ischemia-reperfusion injury is associated with decreased endothelial synthesis of prostacyclin and nitric oxide, we tested whether the addition of prostacyclin or the nitric oxide precursor L-arginine to WA would improve preservation. The Kfc and Ppi were lower with both treatments. In conclusion, ischemia-reperfusion injury was best prevented by using WA. The favorable effect of prostacyclin or L-arginine emphasizes the role played by endothelial dysfunction in ischemia-reperfusion injury.