Hypothermic storage alone in lung preservation for transplantation: a metabolic, light microscopic, and functional analysis after 18 hours of preservation

Acute respiratory distress syndrome induction by pulmonary ischemia-reperfusion injury in large animal models

Acute respiratory distress syndrome (ARDS) is a common critical pulmonary complication after esophagectomy and other thoracic surgeries (e.g., lung transplantation, pulmonary thromboendarterectomy). Direct pulmonary ischemia-reperfusion injury (PIRI) is known to play the main role in induction of ARDS in these cases. Large animal models are an appropriate choice for ARDS as well as PIRI study because of their physiological and anatomic similarities to the human body. With regard to large animal models, we reviewed different methods of inducing in situ direct PIRI and the commonly applied methods for diagnosing and monitoring ARDS or PIRI in an experimental research setting.

Effect of positive end-expiratory pressure after porcine unilateral left lung transplant

OBJECTIVES

To evaluate the effects of 2 different levels of positive end-expiratory pressure on pigs who had unilateral lung transplants.

MATERIALS AND METHODS

A left lung transplant was performed in 12 pigs. The animals were randomized into 2 groups based on positive end-expiratory pressure: group 1 (5 cm H(2)O) and group 2 (10 cm H(2)O). Hemodynamics, gas exchange, and respiratory mechanics were measured before and after surgery. Cytokines, oxidative stress, and histologic scores were assessed in the lung tissue of each pig.

RESULTS

Pigs in group 2 exhibited a significantly higher mean heart rate (P = .006), static compliance (P = .001), lower mean arterial pressure (P = .003), and airway resistance (P = .001) than did pigs in group 1. There were no postoperative differences between the groups in concentrations of thiobarbituric acid reactive substances, superoxide dismutase, and interleukin 8. At the end of the observation period, pigs in group 2 had higher levels of thiobarbituric acid reactive substances (P = .001) and interleukin 8 (P = .05), and pigs in group 1 had higher levels of superoxide dismutase (P = .05) than they did at baseline.

CONCLUSIONS

After unilateral lung transplant, higher positive end-expiratory pressure was associated with improved respiratory mechanics, a negative effect on hemodynamics, a stronger inflammatory response, and increased production of reactive oxygen species, but no effect on gas exchange.

Novel approaches to expanding the lung donor pool: donation after cardiac death and ex vivo conditioning

Two novel approaches have been developed to potentially increase the availability of donor lungs for lung transplantation. In the first approach, lungs from donation after cardiac death (DCD) donors are used to increase the quantity of organ donors. In the second approach, a newly developed normothermic ex vivo lung perfusion (EVLP) technique is used as a means of reassessing the adequacy of lung function from DCD and from high-risk brain death donors prior to transplantation. This EVLP technique can also act as a platform for the delivery of novel therapies to repair injured organs ex vivo.

Carbon monoxide reduces pulmonary ischemia-reperfusion injury in miniature swine

OBJECTIVES

Carbon monoxide is produced endogenously as a by-product of heme catalysis and has been shown to reduce ischemia-reperfusion injury in a variety of organs in murine models. The aims of this translational research were to establish an in situ porcine lung model of warm ischemia-reperfusion injury and to evaluate the cytoprotective effects of low-dose inhaled carbon monoxide in this model.

METHODS

Warm ischemia was induced for 90 minutes by clamping the left pulmonary artery and veins in 8 Clawn miniature swine (Japan Farm CLAWN Institute, Kagoshima, Japan). The left main bronchus was also dissected and reanastomosed just before reperfusion. Four animals were treated with inhaled carbon monoxide at a concentration of approximately 250 ppm throughout the procedure. Lung function and structure were serially accessed via lung biopsy, chest x-ray films, and blood gas analysis.

RESULTS

Carbon monoxide inhalation dramatically decreased the lung injury associated with ischemia and reperfusion. Two hours after reperfusion, the arterial oxygen tension of the carbon monoxide-treated group was 454 +/- 34 mm Hg, almost double the arterial oxygen tension of the control group (227 +/- 57 mm Hg). There were fewer pathologic changes seen on chest x-ray films and in biopsy samples from animals in the carbon monoxide-treated group. Animals in the carbon monoxide-treated group also had fewer inflammatory cell infiltrates and a markedly smaller increase in serum concentrations of the proinflammatory cytokines interleukin 1beta, interleukin 6, and high-mobility group box 1 after ischemia-reperfusion injury.

CONCLUSIONS

The perioperative administration of low-dose inhaled carbon monoxide decreases warm ischemia-reperfusion injury in lungs in miniature swine. This protective effect is mediated in part by the downregulation of proinflammatory mediators.

Recipient treatment with L-arginine attenuates donor lung injury associated with hemorrhagic shock

BACKGROUND

Organ donors are frequently trauma victims, but the impact of donor hemorrhagic shock and resuscitation (HSR) on pulmonary graft function has not been assessed. L-arginine treatment during reperfusion increases the production of endothelial nitric oxide and thus ameliorates ischemia-reperfusion injury. Objective of the present porcine study was to investigate the effect of donor hemorrhage on pulmonary graft function and potential beneficial effects of L-arginine administration.

METHODS

In the control-group (n=6), lungs were harvested from donors without hypotensive periods. In the HSR-group (n=6) and HSR-Arg-group (n=6), donors were subjected to hemorrhagic shock (40% blood shed) and resuscitation before harvest. Left lungs were transplanted after hypothermic preservation of 18 hr, and graft function was observed for 6 hr after reperfusion. Recipients in the HSR-Arg-group received a bolus of L-arginine (50 mg/kg BW) intravenously 5 min before reperfusion followed by a continuous intravenous administration of L-arginine 200 mg/kg BW for 2 hr. Tissue specimens and bronchoalveolar lavage fluid were obtained at the end of the observation period.

RESULTS

Donor lung function did not differ between study groups. Compared with the control group, pulmonary graft gas exchange was significantly impaired in the HSR-group. Graft function in the HSR-Arg-group did not differ from control organs. Neutrophil fraction, protein content, and malondialdehyde levels in the bronchoalveolar lavage fluid in the HSR-group were higher compared with control and HSR-Arg-Group.

CONCLUSION

Although fulfilling ideal donor criteria, pulmonary graft function of lungs harvested from donors subjected to HSR is impaired, but improves significantly when l-arginine is administered during reperfusion.

The efficacy of partial liquid ventilation in lung protection during hypotension and cardiac arrest: preliminary study of lung transplantation using non-heart-beating donors

BACKGROUND

Because of the shortage of suitable brain-dead donors, the use of non-heart-beating donor lungs has been investigated experimentally. However, no effective lung protection method has been developed. In this study, we preliminarily investigated the protective effect of partial liquid ventilation (PLV) on a non-heart-beating rabbit lung.

METHODS

We used 20 male rabbits (mean weight, 3.7 kg) and divided them into 3 groups: the conventional ventilation (control) group, the PLV without cooling group, and the PLV with cooling group. After initially measuring donor cardiopulmonary function, we maintained hypotension at <50 mm Hg for 1 hour followed by 2-hour cardiac arrest. During this time, we used either conventional ventilation or PLV with or without cooling (4 degrees C) for ventilation, and we evaluated the changes in arterial blood gas analysis, pulmonary resistance and elastance, tissue interleukin-8 (IL-8) concentration, and histologic damage.

RESULTS

We found no significant difference in arterial oxygen concentration or in carbon dioxide tension among the 3 groups in the hypotensive phase. Pulmonary elastance increased after perfusion of preservation solution in the control group. However, we found no change in elastance in the PLV groups, which was less than that in the control group. Histologic evaluation after perfusion of preservation solution revealed that alveolar structure was damaged significantly less and cell infiltration was milder in the PLV groups than in the control group. Although IL-8 concentrations in the controls increased after cardiac arrest, IL-8 in the PLV groups remained at baseline concentrations during the study period.

CONCLUSION

In this experimental model of hypotension and cardiac arrest, PLV suppresses lung injury when compared with gas-controlled ventilation.

Lung preservation

Better understanding of the mechanisms of ischemia-reperfusion injury, improvement in the technique of lung preservation, and the recent introduction of a new preservation solution specifically developed for the lungs have helped to reduce the incidence of primary graft dysfunction after lung transplantation. Currently, the limitation in extending the ischemic time is more often related to the increasing use of non-ideal lung donors rather than to poor lung preservation. In this review, we have focused our attention on the experimental and clinical work performed to optimize the methods of lung preservation from the time of retrieval to the period of reperfusion after graft implantation.

CONTINUOUS INFUSION OF NITROGLYCERIN IMPROVES PULMONARY GRAFT FUNCTION OF NON???HEART-BEATING DONOR LUNGS

BACKGROUND

The warm ischemic period of lungs harvested from a non-heart-beating donor (NHBD) results in an increased ischemia-reperfusion injury after transplantation. The intravenous application of nitroglycerin (NTG), a nitric oxide (NO) donor, proved to be beneficial during reperfusion of lung grafts from heart-beating donors. The objective of the present study was to investigate the effect of nitroglycerin on ischemia-reperfusion injury after transplantation of long-term preserved NHBD-lungs.

METHODS

Sixteen pigs (body weight, 20-30 kg) underwent left lung transplantation. In the control group (n=5), lungs were flushed (Perfadex, 60 mL/kg) and harvested immediately after cardiac arrest. In the NHBD group (n=5) and the NHBD-NTG group (n=6), lungs were flushed 90 min (warm ischemia) after cardiac arrest. After a total ischemia time of 19 hr, lungs were reperfused and graft function was observed for 5 hr. Recipient animals in the NHBD-NTG group received 2 microg/kg/min of NTG administered intravenously during the observation period starting 5 min before reperfusion. Tissue specimens and bronchoalveolar lavage fluid (BALF) were obtained at the end of the observation period.

RESULTS

Compared with the control group, pulmonary gas exchange was significantly impaired in the NHBD group, whereas graft function in the NHBD-NTG group did not change. Leukocyte fraction and protein concentration in the BALF and histologic alteration of the NHBD-NTG group were not different from controls.

CONCLUSIONS

Continuous infusion of NTG in the early reperfusion period improves pulmonary graft function of NHBD lungs after long-term preservation. The administration of an NO donor during reperfusion may favor the use of NHBD lungs to alleviate the critical organ shortage in lung transplantation.

Lung transplantation. Lung preservation

Over the past decade, improvements in the technique of lung preservation have led to significant reduction in the incidence of ischemia-reperfusion-induced lung injury after lung transplantation. The challenge remains to improve the number of donor lungs available for transplantation. While the number of patients on the waiting list is constantly increasing, only 10% to 30% of donor lungs are currently being used for transplantation. Hence, the development of new strategies to assess, repair, and improve the quality of the lungs could have a tremendous impact on the number of transplants performed. In addition, an improved understanding of the mechanisms involved in lung preservation might help elucidate the potential link between acute lung injury and chronic graft dysfunction. In the future, genetic analysis using novel technologies such as microarray analysis will help researchers determine which genes control the injury seen in the transplantation process. Hopefully, this information will provide new insights into the mechanisms of injury and reveal potential new strategies and targets for therapies to improve lung preservation.

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.

Tissue damage of non-heart-beating donor lungs after long-term preservation: evaluation of histologic alteration, bronchoalveolar lavage, and energy metabolism

Several studies have shown that warm ischemia before short-term preservation of pulmonary grafts from non-heart-beating donors (NHBD) induced morphological changes, but still provided a good pulmonary graft function. The aim of this study was to investigate morphological and metabolic changes of NHBD lungs after long-term preservation. Left lung allotransplantation was performed on 12 native-bred pigs. In the NHBD group, lungs were subjected to 90 min of warm ischemia before harvesting, whereas lungs in the HBD group were harvested immediately after cardiac arrest. After a total ischemic period of 19 h, lungs were reperfused and pulmonary gas exchange was assessed. Bronchoalveolar lavage (BAL) and tissue specimen for wet-to-dry weight (W/D) ratio, histologic examination, and measurement of high-energy phosphates were taken 5 h after reperfusion. All parameters were compared with a sham-operated control group. Five hours after reperfusion, mean paO2 and paCO2 were 288 +/- 52 and 48 +/- 0.8 mmHg, respectively, during isolated ventilation of the pulmonary graft with 100% oxygen in the NHBD group. W/D ratio and high-energy phosphates of the pulmonary graft did not differ between our study groups. Histologic examination showed significant morphological changes in the HBD and NHBD group, but alterations were more pronounced in the NHBD group. The percentage of neutrophils, total protein content, and potassium concentration were significantly elevated in the BAL fluid of the NHBD group. Despite the observed aggravation of cellular injury after long-term preservation, NHBD lungs still performed a good pulmonary graft function.

Ultrastructure of canine type II pneumocytes during hypothermic ischemia of the lung: a study by means of conventional and energy filtering transmission electron microscopy and stereology

Alterations in pulmonary surfactant have been reported to be associated with ischemia/reperfusion injury in experimental and clinical lung transplantation. It is unknown whether these alterations are due to damage to surfactant synthesizing type II pneumocytes during hypothermic ischemic storage. The aim of the present study was to examine the effects of hypothermic ischemic storage of the lung on canine type II pneumocytes by means of conventional (CTEM) and energy filtering TEM (EFTEM) and stereology. The lungs of 18 dogs were fixed for TEM immediately after cardiac arrest (6 double lungs) and after storage in Tutofusin at 4 degrees C for 20 min, 4 hr, 8 hr, and 12 hr (6 single lungs, respectively). Using a systematic uniform random sampling scheme, type II pneumocytes were analyzed qualitatively and stereologically. The relative phosphorus content of cell organelles, especially the surfactant containing lamellar bodies, was investigated by EFTEM. By CTEM, no major qualitative alterations could be observed in type II pneumocytes of the experimental groups. Stereologically, no significant changes in the volume densities or the volume-to-surface ratios of type II pneumocytes and their lamellar bodies were found. By EFTEM, the highest intracellular phosphorus signals were recorded over lamellar bodies in all experimental groups. No changes in the phosphorus signals were observed during ischemia. These results indicate that the ultrastructure of canine type II pneumocytes and their lamellar bodies is not affected by hypothermic ischemia of the lung up to 12 hr. Structural preservation of intracellular surfactant is possible during prolonged ischemic lung storage.

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.

Influence of long-term preservation with endobronchially administered perfluorodecalin on pulmonary graft function

BACKGROUND

Experimental studies demonstrated a suppression of oxygen-derived free radicals, reduced adhesion of activated neutrophils on the endothelium and an increase of de novo synthesis of surfactant during liquid ventilation with perflurocarbon. The purpose of this study was to assess the pulmonary graft function after preservation with endobronchially administered perfluorocarbon as an alternative to flush perfusion.

METHODS

Native bred pigs underwent orthotopic left lung transplantation. Donor lungs were flushed in situ with either a low-potassium dextran solution (LPD, n=6) or a perfluorochemical was administered endobronchially (PFC, n=6) and were then stored after removal for 18 hr at 4 degrees C. Pulmonary graft function was assessed after reperfusion for 5 hr by measuring pulmonary gas exchange and hemodynamics during isolated ventilation and perfusion. Tissue specimens were taken for analysis of morphology and wet/dry ratio. All values were compared to a sham-operated group (n=6).

RESULTS

Pulmonary gas exchange of the graft revealed reduced paO2 values and elevated paCO2 values in the PFC group throughout the observation period as compared with the LPD group and sham group. Endothelial alterations and fibrin exudate in the PFC group were significantly more pronounced. Lungs in the LPD group showed functional and morphological recovery close to sham group.

CONCLUSIONS

Long-term preservation with endobronchially administered perfuorocarbon is possible. Impaired pulmonary graft function and pronounced morphological alterations indicate an aggravation of the ischemic reperfusion injury after lung transplantation compared to LPD preserved lungs.

Pulmonary graft function after long-term preservation of non-heart-beating donor lungs

BACKGROUND

Critical organ shortage in lung transplantation could be attenuated by the use of non-heart-beating donor (NHBD) lungs. In addition, prolonged ischemic tolerance of the organs would contribute to the alleviation of organ shortage. The aim of this study was to investigate pulmonary graft function of NHBD lungs after long-term hypothermic storage.

METHODS

Twelve native-bred pigs (bodyweight 20 to 30 kg) underwent left lung allotransplantation. In the heart-beating donor (HBD) group, lungs were harvested immediately after cardiac arrest. In the NHBD group, lungs were subjected to a warm ischemic period of 90 minutes before harvesting. After a total ischemic time of 19 hours, pulmonary grafts in both groups were reperfused and pulmonary graft function was assessed. All values were compared with a sham-operated control group.

RESULTS

Pulmonary graft function in the HBD group was excellent. In the NHBD group, pulmonary gas exchange was impaired, but still provided good graft function compared with the excellent graft function in the HBD group. Pulmonary vascular resistance was even lower in the NHBD group. In the NHBD group, calculated intrapulmonary shunt fraction (Qs/Qt) was significantly increased compared with the sham-group. Histologic alteration and wet-to-dry ratio did not differ significantly between the HBD and NHBD group.

CONCLUSIONS

We conclude that NHBD lungs (90 minutes of warm ischemic time) have the potential to alleviate organ shortage in lung transplantation even after an extended total ischemic time.

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.