Inhaled nitric oxide attenuates reperfusion injury in non-heartbeating-donor lung transplantation. Paris-Sud University Lung Transplantation Group

Therapeutic benefits of nitric oxide in lung transplantation

Lung transplantation is an evolutionary procedure from its experimental origin in the twentieth century and is now recognized as an established and routine life-saving intervention for a variety of end-stage pulmonary diseases refractory to medical management. Despite the success and continuous refinement in lung transplantation techniques, the widespread application of this important life-saving intervention is severely hampered by poor allograft quality offered from donors-after-brain-death. This has necessitated the use of lung allografts from donors-after-cardiac-death (DCD) as an additional source to expand the pool of donor lungs. Remarkably, the lung exhibits unique properties that may make it ideally suitable for DCD lung transplantation. However, primary graft dysfunction (PGD), allograft rejection and other post-transplant complications arising from unavoidable ischemia-reperfusion injury (IRI) of transplanted lungs, increase morbidity and mortality of lung transplant recipients annually. In the light of this, nitric oxide (NO), a selective pulmonary vasodilator, has been identified as a suitable agent that attenuates lung IRI and prevents PGD when administered directly to lung donors prior to donor lung procurement, or to recipients during and after transplantation, or administered indirectly by supplementing lung preservation solutions. This review presents a historical account of clinical lung transplantation and discusses the lung as an ideal organ for DCD. Next, the author highlights IRI and its clinical effects in lung transplantation. Finally, the author discusses preservation solutions suitable for lung transplantation, and the protective effects and mechanisms of NO in experimental and clinical lung transplantation.

Inhaled Pulmonary Vasodilator Therapy in Adult Lung Transplant: A Randomized Clinical Trial

Importance

Inhaled nitric oxide (iNO) is commonly administered for selectively inhaled pulmonary vasodilation and prevention of oxidative injury after lung transplant (LT). Inhaled epoprostenol (iEPO) has been introduced worldwide as a cost-saving alternative to iNO without high-grade evidence for this indication.

Objective

To investigate whether the use of iEPO will lead to similar rates of severe/grade 3 primary graft dysfunction (PGD-3) after adult LT when compared with use of iNO.

Design, Setting, and Participants

This health system-funded, randomized, blinded (to participants, clinicians, data managers, and the statistician), parallel-designed, equivalence clinical trial included 201 adult patients who underwent single or bilateral LT between May 30, 2017, and March 21, 2020. Patients were grouped into 5 strata according to key prognostic clinical features and randomized per stratum to receive either iNO or iEPO at the time of LT via 1:1 treatment allocation.

Interventions

Treatment with iNO or iEPO initiated in the operating room before lung allograft reperfusion and administered continously until cessation criteria met in the intensive care unit (ICU).

Main Outcomes and Measures

The primary outcome was PGD-3 development at 24, 48, or 72 hours after LT. The primary analysis was for equivalence using a two one-sided test (TOST) procedure (90% CI) with a margin of 19% for between-group PGD-3 risk difference. Secondary outcomes included duration of mechanical ventilation, hospital and ICU lengths of stay, incidence and severity of acute kidney injury, postoperative tracheostomy placement, and in-hospital, 30-day, and 90-day mortality rates. An intention-to-treat analysis was performed for the primary and secondary outcomes, supplemented by per-protocol analysis for the primary outcome.

Results

A total of 201 randomized patients met eligibility criteria at the time of LT (129 men [64.2%]). In the intention-to-treat population, 103 patients received iEPO and 98 received iNO. The primary outcome occurred in 46 of 103 patients (44.7%) in the iEPO group and 39 of 98 (39.8%) in the iNO group, leading to a risk difference of 4.9% (TOST 90% CI, -6.4% to 16.2%; P = .02 for equivalence). There were no significant between-group differences for secondary outcomes.

Conclusions and Relevance

Among patients undergoing LT, use of iEPO was associated with similar risks for PGD-3 development and other postoperative outcomes compared with the use of iNO.

Trial Registration

ClinicalTrials.gov identifier: NCT03081052.

Inhaled pulmonary vasodilators: a narrative review

Pulmonary hypertension (PH) is a severe disease that affects people of all ages. It can occur as an idiopathic disorder at birth or as part of a variety of cardiovascular and pulmonary disorders. Inhaled pulmonary vasodilators (IPV) can reduce pulmonary vascular resistance (PVR) and improve RV function with minimal systemic effects. IPV includes inhaled nitric oxide (iNO), inhaled aerosolized prostacyclin, or analogs, including epoprostenol, iloprost, treprostinil, and other vasodilators. In addition to pulmonary vasodilating effects, IPV can also be used to improve oxygenation, reduce inflammation, and protect cell. Off-label use of IPV is common in daily clinical practice. However, evidence supporting the inhalational administration of these medications is limited, inconclusive, and controversial regarding their safety and efficacy. We conducted a search for relevant papers published up to May 2020 in four databases: PubMed, Google Scholar, EMBASE and Web of Science. This review demonstrates that the clinical using and updated evidence of IPV. iNO is widely used in neonates, pediatrics, and adults with different cardiopulmonary diseases. The limitations of iNO include high cost, flat dose-response, risk of significant rebound PH after withdrawal, and the requirement of complex technology for monitoring. The literature suggests that inhaled aerosolized epoprostenol, iloprost, treprostinil and others such as milrinone and levosimendan may be similar to iNO. More research of IPV is needed to determine acceptable inclusion criteria, long-term outcomes, and management strategies including time, dose, and duration.

Pulmonary Protection Strategies in Cardiac Surgery: Are We Making Any Progress?

Pulmonary dysfunction is a common complication of cardiac surgery. The mechanisms involved in the development of pulmonary dysfunction are multifactorial and can be related to the activation of inflammatory and oxidative stress pathways. Clinical manifestation varies from mild atelectasis to severe respiratory failure. Managing pulmonary dysfunction postcardiac surgery is a multistep process that starts before surgery and continues during both the operative and postoperative phases. Different pulmonary protection strategies have evolved over the years; however, the wide acceptance and clinical application of such techniques remain hindered by the poor level of evidence or the sample size of the studies. A better understanding of available modalities and/or combinations can result in the development of customised strategies for the different cohorts of patients with the potential to hence maximise patients and institutes benefits.

Inhaled nitric oxide therapy for extrapulmonary inflammation

Inhaled nitric oxide (iNO) has been used extensively to treat pulmonary hypertension primarily in newborns. This therapy is a safe and effective therapy to improve the matching between airway ventilation and blood oxygenation. A key conceptual component of iNO therapy is that effects are limited to the pulmonary compartment thereby avoiding unwanted systemic effects. The mechanism underlying this model is that any NO entering the blood stream is rapidly oxidized to nitrate, a relatively inert anion that is excreted. Mediating this oxidation is oxyhemoglobin that becomes oxidized to methemoglobin, accumulation of which is limited by erythrocyte methemoglobin reductase. In this article, we discuss studies that dismiss the notion that once in the blood stream iNO is inactivated and show that a surprising result of iNO therapy is the formation of stable NO-derived products that circulate and can elicit NO-dependent signaling in extra-pulmonary tissues. This pathway has the potential to open up new applications for iNO for treatment of systemic diseases associated with loss of NO signaling.

Effects of exogenous surfactant on the non-heart-beating donor lung graft in experimental lung transplantation - a stereological study

The use of non-heart-beating donor (NHBD) lungs may help to overcome the shortage of lung grafts in clinical lung transplantation, but warm ischaemia and ischaemia/reperfusion injury (I/R injury) resulting in primary graft dysfunction represent a considerable threat. Thus, better strategies for optimized preservation of lung grafts are urgently needed. Surfactant dysfunction has been shown to contribute to I/R injury, and surfactant replacement therapy is effective in enhancing lung function and structural integrity in related rat models. In the present study we hypothesize that surfactant replacement therapy reduces oedema formation in a pig model of NHBD lung transplantation. Oedema formation was quantified with (SF) and without (non-SF) surfactant replacement therapy in interstitial and alveolar compartments by means of design-based stereology in NHBD lungs 7 h after cardiac arrest, reperfusion and transplantation. A sham-operated group served as control. In both NHBD groups, nearly all animals died within the first hours after transplantation due to right heart failure. Both SF and non-SF developed an interstitial oedema of similar degree, as shown by an increase in septal wall volume and arithmetic mean thickness as well as an increase in the volume of peribron-chovascular connective tissue. Regarding intra-alveolar oedema, no statistically significant difference could be found between SF and non-SF. In conclusion, surfactant replacement therapy cannot prevent poor outcome after prolonged warm ischaemia of 7 h in this model. While the beneficial effects of surfactant replacement therapy have been observed in several experimental and clinical studies related to heart-beating donor lungs and cold ischaemia, it is unlikely that surfactant replacement therapy will overcome the shortage of organs in the context of prolonged warm ischaemia, for example, 7 h. Moreover, our data demonstrate that right heart function and dysfunctions of the pulmonary vascular bed are limiting factors that need to be addressed in NHBD.

A randomized clinical trial testing the anti-inflammatory effects of preemptive inhaled nitric oxide in human liver transplantation

Decreases in endothelial nitric oxide synthase derived nitric oxide (NO) production during liver transplantation promotes injury. We hypothesized that preemptive inhaled NO (iNO) would improve allograft function (primary) and reduce complications post-transplantation (secondary). Patients at two university centers (Center A and B) were randomized to receive placebo (n = 20/center) or iNO (80 ppm, n = 20/center) during the operative phase of liver transplantation. Data were analyzed at set intervals for up to 9-months post-transplantation and compared between groups. Patient characteristics and outcomes were examined with the Mann-Whitney U test, Student t-test, logistic regression, repeated measures ANOVA, and Cox proportional hazards models. Combined and site stratified analyses were performed. MELD scores were significantly higher at Center B (22.5 vs. 19.5, p<0.0001), surgical times were greater at Center B (7.7 vs. 4.5 hrs, p<0.001) and warm ischemia times were greater at Center B (95.4 vs. 69.7 min, p<0.0001). No adverse metabolic or hematologic effects from iNO occurred. iNO enhanced allograft function indexed by liver function tests (Center B, p<0.05; and p<0.03 for ALT with center data combined) and reduced complications at 9-months (Center A and B, p = 0.0062, OR = 0.15, 95% CI (0.04, 0.59)). ICU (p = 0.47) and hospital length of stay (p = 0.49) were not decreased. iNO increased concentrations of nitrate (p<0.001), nitrite (p<0.001) and nitrosylhemoglobin (p<0.001), with nitrite being postulated as a protective mechanism. Mean costs of iNO were $1,020 per transplant. iNO was safe and improved allograft function at one center and trended toward improving allograft function at the other. ClinicalTrials.gov with registry number 00582010 and the following URL:http://clinicaltrials.gov/show/NCT00582010.

Comparing beneficial effects of inhaled nitric oxide to L-arginine in necrotizing enterocolitis model in neonatal rats

OBJECTIVE

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal condition of neonatal infants. The pathophysiology of NEC remains poorly understood. We tried to evaluate the effectiveness of inhaled NO compared to L-arginine usage in necrotizing enterocolitis model in rats.

MATERIAL-METHODS

46 newborn pups from 4 time-mated Sprague-Dawley pregnant rats were divided equally into 4 groups as follows: NEC (subjected to NEC), NEC + L-arginine, NEC + inhaled NO and control.

RESULTS

SOD, GSH-Px and NOx levels were significantly higher and MDA levels were significantly lower in NEC + inhaled NO group compared to NEC + L-arginine group. There was significantly lower intestinal injury and apoptosis index scoring in NEC + inhaled NO group compared to NEC + L-arginine group.

CONCLUSION

We think that inhaled NO can be used as a novel therapeutic agent like L-arginine in NEC, like using in pulmonary hypertention in newborns but much more studies are needed.

Preconditioning by inhaled nitric oxide prevents hyperoxic and ischemia/reperfusion injury in rat lungs

Since the generation of nitric oxide (NO) is an essential step in the trigger phase of ischemic preconditioning, short-term inhalation of NO before ischemia should ameliorate ischemia/reperfusion (I/R) injury of the lung. We tested this hypothesis in high oxygen (>99%) ventilated rats in order to additionally evaluate compatibility of NO and exposure to hyperoxia. Male adult Sprague-Dawley rats inhaled NO (15 ppm, 10 min) before the left lung hilum was clamped for 1 h, and the reperfusion phase was observed for 4 h (NO group). Animals in the I/R group underwent the same treatment, but without NO inhalation. A third group without I/R served as time-matched controls. Animals in the I/R group showed severe I/R injury in terms of arterial pO2 (apO2), which was reduced to 22% of surgical controls (SCs) at time point 30 min reperfusion, and increased endothelial permeability (Evans blue procedure). The pretreatment with NO attenuated these effects. The pO2 after 4 h reperfusion was still 3.0-fold higher in the NO group compared to I/R. In contrast, the I/R- and hyperoxia-induced invasion of leukocytes, as determined by measuring myeloperoxidase (MPO) activity, was not affected by NO. These data were correlated with the activity of major cellular signaling pathways by measuring the phosphorylation at activating and inhibitory sites of extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, protein kinase B (AKT), and glycogen synthase kinase 3beta (GSK-3beta), and by determination of cGMP in plasma and lung tissue. Inhalation of NO partly prevented the loss of activation by I/R and hyperoxic ventilation of ERK, JNK, and AKT, and it reduced the I/R-induced activation of GSK-3beta. The level of cGMP in plasma and lung tissue was increased in the NO group after 4 h reperfusion. In conclusion, application of inhaled NO in the preconditioning mode prevented I/R injury in the rat lung without interfering effects of hyperoxic ventilation. The effects of NO on cellular signaling pathways resemble mechanisms of ischemic preconditioning, but further studies have to evaluate the physiological relevance of these results.

Perspectives in organ preservation

Maintaining organ viability after donation until transplantation is critically important for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in every day clinical practice. Although simple and effective, it is questionable whether this method is able to prevent deterioration of organ quality in the present era with increasing numbers of organs retrieved from older, more marginal, and even non-heart-beating donors. This review describes principles involved in effective preservation and focuses on some basic components and methods of abdominal organ preservation in clinical and experimental transplantation. Concepts and developments to reduce ischemia related injury are discussed, including hypothermic machine perfusion. Despite the fact that hypothermic machine perfusion might be superior to static cold storage preservation, organs are still exposed to hypothermia induced damage. Therefore, recently some groups have pointed at the beneficial effects of normothermic machine perfusion as a new perspective in organ preservation and transplantation.

Donor pretreatment using the aerosolized prostacyclin analogue iloprost optimizes post-ischemic function of non-heart beating donor lungs

BACKGROUND

Ischemia-reperfusion injury accounts for one-third of early deaths after lung transplantation. To expand the limited donor pool, lung retrieval from non-heart beating donors (NHBD) has been introduced recently. However, because of potentially deleterious effects of warm ischemia on microvascular integrity, use of NHBD lungs is limited by short tolerable time periods before preservation. After intravenous prostanoids are routinely used to ameliorate reperfusion injury, the latest evidence suggests similar efficacy of inhaled prostacyclin. Therefore, the impact of donor pretreatment with the prostacyclin analogue iloprost on postischemic NHBD lung function and preservation quality was evaluated.

METHODS

Asystolic pigs (5 per group) were ventilated for 180 minutes of warm ischemia (Group 2). In Group 3, 100 microg iloprost was aerosolized during the final 30 minutes of ventilation with a novel mobile ultrasonic nebulizer. Lungs were then retrogradely preserved with Perfadex and stored for 3 hours. After left lung transplantation and contralateral lung exclusion, hemodynamics, rO2/FiO2, and dynamic compliance were monitored for 6 hours and compared with sham-operated controls (Group 1). Pulmonary edema was determined both stereologically and by wet-to-dry weight ratio (W/D). Statistics comprised analysis of variance with repeated measures and Mann-Whitney test.

RESULTS

Flush preservation pressures, dynamic compliance, inspiratory pressures, and W/D were significantly superior in iloprost-treated lungs, and oxygenation and pulmonary hemodynamics were comparable between groups. Stereology revealed a trend toward lower intraalveolar edema formation in iloprost-treated lungs compared with untreated grafts.

CONCLUSIONS

Alveolar deposition of Iloprost and NHBD lungs before preservation ameliorates postischemic edema and significantly improves lung compliance. This easily applicable innovation approach, which uses a mobile ultrasonic nebulizer, offers an important strategy for improvement of pulmonary preservation quality and might expand the pool of donor lungs.

Selective inducible nitric oxide synthase (iNOS) inhibition attenuates remote acute lung injury in a model of ruptured abdominal aortic aneurysm

OBJECTIVE

Abdominal aortic aneurysm rupture is associated with a systemic inflammatory response syndrome and acute lung injury. Using a selective inducible nitric oxide synthase (iNOS) inhibitor, N(6)-(iminoethyl)-lysine (L-NIL), we explored the role of iNOS in the early pro-inflammatory signaling and acute lung injury in experimental abdominal aortic aneurysm rupture.

MATERIALS AND METHODS

Anesthetized rats were randomized to sham control or shock and clamp (s + c) groups, which underwent one hour of hemorrhagic shock, followed by 45 minutes of supramesenteric aortic clamping, and then two hours resuscitated reperfusion. Animals in s + c were randomized to receive intravenous L-NIL at 50 microg/kg/h or saline at the start of reperfusion. Pulmonary permeability to (125)I-labeled albumin, myeloperoxidase (MPO) activity, cytokine levels, and semi-quantitative RT-PCR for mRNA were indicators of microvascular permeability, leuco-sequestration, and pro-inflammatory signaling, respectively.

RESULTS

Lung permeability index were significantly increased in s + c compared to sham (4.43 +/- 0.96 versus 1.30 +/- 0.17, P < 0.01), and attenuated by L-NIL treatment (2.14 +/- 0.70, P < 0.05). Lung tissue MPO activity was significantly increased in s + c compared to sham (2.80 +/- 0.32 versus 1.03 +/- 0.29, P < 0.002), and attenuated by L-NIL treatment (1.50 +/- 0.20, P < 0.007). Lung tissue iNOS activity was significantly increased in s + c compared to sham animals (P < 0.05), and attenuated by L-NIL treatment (P < 0.05). Lung tissue iNOS mRNA was upregulated 8-fold in s + c compared to sham (P < 0.05). Data represents mean +/- standard error mean, comparisons with ANOVA.

CONCLUSIONS

These data suggest that in our model of ruptured abdominal aortic aneurysm iNOS plays a crucial role in reperfusion lung injury. Selective inhibition of iNOS during early reperfusion prevents neutrophil mediated acute lung injury.

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 Retrieval from Non-Heart-Beating Donors: First Experience with an Innovative Preservation Strategy in a Pig Lung Transplantation Model

OBJECTIVE

Lung transplantation is limited by the scarcity of donor organs. Lung retrieval from non-heart-beating donors (NHBD) might extend the donor pool and has been reported recently. However, no studies in NHBD exist using the novel approach of retrograde preservation with Perfadex solution.

METHODS

Heparinized asystolic pigs (n = 5, 30-35 kg) were ventilated for 90 min. The lungs were retrogradely preserved with Perfadex solution and stored inflated at 4 degrees C for 3 h. Left lung transplantation in the recipient was followed by exclusion of the right lung. Results were compared to sham-operated animals. Oxygenation, hemodynamics and dynamic compliance were monitored for 4 h. Infiltration of polymorphonuclear cells (PMNs) and stereological quantification of alveolar edema was performed. Statistical analysis comprised Kruskal-Wallis and Mann-Whitney tests and ANOVA analysis with repeated measures.

RESULTS

No mortality was observed. During preservation, continuous elimination of blood clots via the pulmonary artery venting site was observed. Oxygenation and compliance were similar between groups, but sham controls showed significantly lower pulmonary vascular resistance. Stereological quantification revealed higher volume fractions of intra-alveolar edema in NHBD grafts, while PMN infiltration was comparable to sham controls.

CONCLUSIONS

Use of NHBD lungs results in excellent outcome after 90 min of warm ischemia followed by retrograde preservation with Perfadex solution. This novel approach can optimize lung preservation by eliminating clots from the pulmonary circulation and might clinically be considered in brain-dead organ donors who become hemodynamically unstable prior to organ harvest. Further trials with longer warm and cold ischemic periods are necessary to further elucidate this promising approach to donor pool expansion.

Non-heart-beating donors in thoracic transplantation

Access to lung transplantation is severely limited by a scarcity of suitable donors, resulting in increasing numbers of deaths on the heart and lung transplant waiting lists, and strict selection criteria for recipients. Unlike some other solid organs, the lung may be ideally suited to retrieval for transplant following substantial intervals after circulatory arrest. This may be because lung parenchymal cells do not rely on perfusion for cellular respiration. This review outlines the relevant published experimental data that addresses the concept that lungs might be suitable for transplant even if retrieved from non-heart-beating donors (NHBDs), and the small published clinical experience with NHBDs as lung donors. Aspects of reperfusion injury in this setting are reviewed. The prospect of heart transplant from NHBDs is addressed. The impact of the routine use of NHBDs on lung transplantation is discussed.

Nitric oxide during perfusion improves posttransplantation function of non- heart-beating donor lungs

BACKGROUND

We attempted to determine in a pig model whether 20 ppm of nitric oxide (NO) during perfusion ameliorates warm ischemic lung injury in the non-heart-beating donor (NHBD), thereby improving function with longer warm ischemia.

METHODS

Lungs were retrieved from three groups (n=6): 1 hr (NHBD(1)) and 2 hr with and without NO (NHBD(2)NO, NHBD(2)) after hypoxic death. For assessment and preservation, left lungs were ventilated with 100% oxygen (NHBD(2)NO with added NO) and perfused for 20 min with neutrophil-depleted, deoxygenated blood in Perfadex solution. Pulmonary vascular and airway pressures and blood flow were measured with pulmonary venous blood gases. Perfusion temperature was reduced to 18 degrees C prior to storage at 4 degrees C before transplantation.

RESULTS

NO during perfusion significantly improved posttransplantation pulmonary venous oxygenation (NHBD(1) [mean +/- SD] 51+/-14 kPa, NHBD(2) 54+/-16 kPa, and NHBD(2)NO 61+/-6 kPa; P=0.01) and airway pressures (NHBD(1) 30.8+/-3.5, NHBD(2) 32.5+/-5.6, NHDB(2)NO 29.4+/-5.3; P=0.0001). NO significantly improved pulmonary vascular resistance (excluding the initial cold-induced vasoconstricted reperfusion period): NHBD(1) 19+/-9 Wood units, NHBD(2) 28+/-25 Wood units, NHDB(2)NO 16+/-10 Wood units, P=0.029. Neutrophil uptake was significantly lowered by NO: NHBD(1) 0.6+/-1.4*10(9) minute-1, NHBD(2) 1.2+/-1.0*10(9) minute-1, NHBD(2)NO 0.4+/-0.9*10(9) minute-1 (P=0.029).

CONCLUSIONS

This technique satisfactorily assesses and preserves the non-heart-beating lung. NO during preservation reverses the slight deterioration seen when increasing warm ischemia from 1 to 2 hr, significantly improving transplant oxygenation, vascular resistance, and airway pressures. This may be a result of the observed significant reduction in neutrophil sequestration.

A randomized trial of inhaled nitric oxide to prevent ischemia-reperfusion injury after lung transplantation

Inhalation of nitric oxide (NO) has been advocated as a method to prevent ischemia-reperfusion injury after lung transplantation. We enrolled 84 patients into a concealed, randomized, placebo-controlled trial to evaluate the effect of inhaled NO (20 ppm NO or nitrogen) initiated 10 minutes after reperfusion on outcomes after lung transplantation. The groups (n = 42) were balanced with respect to age, sex, lung disease, procedure, and total ischemic times. PaO2/FIO2 ratios were similar on admission to the intensive care unit (ICU) (NO 361 +/- 134; control patients 357 +/- 132), and over the duration of the study. There were no differences in hemodynamics between the two groups. Severe reperfusion injury (PaO2/FIO2 < 150) was present at the time of admission to the ICU in 14.6% NO patients versus 9.5% of control patients (p = 0.48). The groups had similar median times to first successful trial of unassisted breathing (25 vs. 27 hours; p = 0.76), successful extubation (32 vs. 34 hours; p = 0.65), ICU discharge (3.0 days for both groups), and hospital discharge (27 vs. 29 days; p = 0.563). Five NO versus six control patients died during their hospital stay. Adjusting for age, sex, lung disease etiology, presence of pulmonary hypertension, and total ischemic time did not alter these results. In conclusion, we did not detect a significant effect of inhaled NO administered 10 minutes after reperfusion on physiologic variables or outcomes in lung transplant patients.

Protective effects of inhaled nitric oxide and gabexate mesilate in lung reperfusion injury after transplantation from non-heart-beat donors

BACKGROUND

The use of lung grafts from non-heart-beat donors (NHBDs) is one way of solving the critical donor organ shortage. Inhaled nitric oxide (NO) and gabexate mesilate (FOY), a protease inhibitor, can attenuate some types of neutrophil-mediated tissue injury. Using an isolated lung ventilation and perfusion model, we studied the effects of these agents on reperfusion injury following lung transplantation from NHBDs.

METHODS

Five groups of minipigs were studied. In group 1(n = 6), the lungs were flushed and harvested after cardiac arrest, and were reperfused for 2 hours after 2 hours of cold ischemia. In group 2 (n = 6), the lungs were harvested after 2 hours of in situ warm ischemia, followed by 2 hours of cold ischemia and 2 hours of reperfusion. In groups 3 (n = 7), 4 (n = 7), and 5 (n = 6), the procedure was the same as in group 2, except in group 3, NO was inhaled before and after ischemia, in group 4, FOY was given intravenously, and in group 5, a combination of inhaled NO and intravenous FOY were administered.

RESULTS

Compared with group 1, group 2 had higher mean pulmonary arterial pressure, vascular resistance, and lower arterial blood oxygen tension. Furthermore, these negative effects of warm ischemia were also reflected in the contents of bronchoalveolar lavage fluid, tissue myeloperoxidase (MPO) activity, histology, and permeability change. Either FOY or NO administration (groups 3 or 4) ameliorated the associated injury. A combination of FOY and NO use (group5) decreased the parameters of lung reperfusion injury measurement to a larger degree than either agent individually.

CONCLUSIONS

The inhaled NO and FOY can protect NHBD lung grafts at an early reperfusion period. Their use in combination has an additive protective effect that might be applied to the protection of NHBD grafts from preservation and reperfusion injury.

Survival and graft function in a large animal lung transplant model after 30 h preservation and substitution of the nitric oxide pathway

OBJECTIVE

Substitution of the nitric oxide- (NO-) pathway improves early graft function following lung transplantation. We previously demonstrated that 8-Br-cGMP (second messenger of NO) to the flush solution and tetrahydrobiopterin (BH4, coenzyme of NO synthase) given as additive during reperfusion improve post-transplant graft function. In the present study, the combined treatment with 8-Br-cGMP and BH4 was evaluated.

METHODS

Unilateral left lung transplantation was performed in weight matched outbred pigs (24-31 kg). In group I, grafts were preserved for 30 h (n=5). 8-Br-cGMP (1mg/kg) was added to the flush solution (Perfadex, 1.5l, 1 degrees C) and BH4 (10mg/kg/h) was given to the recipient for 5h after reperfusion. In group II, lungs were transplanted after a preservation time of 30 h (n=3) and prostaglandin E(1) (250 g) was given into the pulmonary artery (PA) prior to flush. In all recipients 1h after reperfusion the contralateral right PA and bronchus were ligated to assess graft function only. Survival time after reperfusion, extravascular lung water index (EVLWI), hemodynamic variables, and gas exchange (PaO(2)) were assessed during a 12h observation period.

RESULTS

All recipients in group I survived the 12h assessment, whereas none of the group II animals survived more than 4h after reperfusion with a rapid increase of EVLWI up to 24.8+/-6.7 ml/kg. In contrast, in group I EVLWI reached up to 8.9+/-1.5 ml/kg and returned to nearly normal levels at 12h (6.1+/-0.8 ml/kg). In two animals of group I the gas exchange deteriorated slightly. The other three animals showed normal arterial oxygenation over the entire observation time.

CONCLUSION

Our data indicate that the combined substitution of the NO pathway during preservation and reperfusion reduces ischemia/reperfusion injury substantially and that this treatment even allows lung transplantation after 30 h preservation in this model.

Protective role of the L-arginine-nitric oxide synthase pathway on preservation injury after rat liver transplantation

BACKGROUND

A major problem complicating liver transplantation is the preservation injury that results from cold storage and subsequent ischemia/reperfusion injury after organ revascularization. The L-arginine-nitric oxide (NO) pathway has been recognized to play critical roles during infection, inflammation, organ injury, and transplant rejection. Recent data indicates that NO synthesis has beneficial effects in several models of liver injury. The purpose of this study is to examine the role of the L-arginine-NO pathway on preservation injury in an experimental model of rat liver transplantation.

METHODS

Orthotopic liver transplantation was performed in syngeneic (LEW to LEW) rats. Liver preservation injury was determined by measuring serum liver function tests 6 to 48 hours after transplantation. In some experiments, rats received L-arginine supplementation 0 to 24 hours after transplantation. In other experiments, NO synthase inhibitors (L-NAME or L-NIL) were injected at the time of isograft revascularization.

RESULTS

L-Arginine supplementation decreased hepatic transaminase levels at all time points examined (6-48 hours). L-Arginine produced a significant improvement in liver preservation injury by 12 hours after reperfusion. The NO synthase inhibitor L-NAME caused a significant increase in liver injury 24 hours after injection. The inducible NO synthase (iNOS)-specific inhibitor L-NIL had no significant effect on liver injury.

CONCLUSIONS

The results show that L-arginine supplementation and NO synthesis improve hepatic injury and have a protective role in the transplanted liver graft. The protective effect may be mediated by low-level cNOS-derived NO.

The effects of inhaled nitric oxide, gabexate mesilate, and retrograde flush in the lung graft from non-heart beating minipig donors

BACKGROUND

The use of lung grafts from non-heart-beating donors (NHBD) is one way of solving the donor organ shortage problem. In this experiment, we studied the effect of retrograde flush (RF) from the left atrium before harvest, inhaled nitric oxide (NO), and gabexate mesilate (FOY), a protease inhibitor, in the lung grafts from NHBD.

METHODS

Forty-eight Lee-Sung, small-ear, miniature pigs (15-20 kg) were divided into 24 pairs (donor and recipient) and four groups. The donor lungs were flushed and harvested 90 min after cardiac arrest. No i.v. heparin was administered until the time before flush and harvest. Left single lung transplantation was undertaken, and the recipients were observed for 18 hr. The grafts warm and cold ischemia times were 90 (controlled) and 183+/-23.4 min. Group 1 (untreated control, UC, n=6) had core perfusion through a Swan-Ganz catheter followed by a single, antegrade flush with modified Euro-Collin's solution containing heparin, urokinase, and PGE1. Group 2 (RF group, n=6) had the same as group 1, except that one additive retrograde flush through the left atrium was administered. Group 3 (NO group, n=6) had the same as group 1, except that 20 parts per million (ppm) inhaled NO was administered for the cadaver donors before the graft harvest, and for the recipients after the grafts reperfusion. Group 4 (FOY group, n=6) had the same as group 1, except that the recipients received FOY i.v. infusion from the beginning of the recipient's operation and continuously throughout the experiments.

RESULTS

Compared with the group 1 (control), group 2 (RF) had significantly (P<0.05) lower mean pulmonary artery pressure, pulmonary vascular resistance (PVR), lung wet/dry ratio, histological lung injury score, and higher PaO2/FiO2 and pulmonary dynamic compliance. Group 3 (NO) had significantly lower mean pulmonary arterial pressure, PVR, lung injury score, degree of tissue neutrophils infiltration (histological and myeloperoxidase assay), bronchoalveolar lavage fluid protein content and neutrophils (PMNs) percentage, and higher PaO2/FiO2 and pulmonary dynamic compliance. Group 4 (FOY) had significantly lower PMNs infiltration, lung injury score, wet/dry ratio, bronchoalveolar lavage fluid protein and PMNs percentage, and higher PaO2/FiO2. Group 2 (RF) revealed better gas exchange (PaO2/FiO2) than the control (group 1) at earlier reperfusion periods (1st and 5th hr). On the contrary, group 4 (FOY) had higher PaO2/FiO2 than group 1 only at later period (18th hr). Pathologically, retrograde flush (group 2, RF) inhibited the intravascular thrombi formation more effectively than the NO or FOY treatment. However, the NO or FOY treatment inhibited the neutrophil infiltration more effectively than did the retrograde flush.

CONCLUSION

The retrograde flush, inhaled NO and FOY infusion are beneficial to the protection of the NHBD lung grafts at an early reperfusion period, through different mechanisms. The use of these treatments in combination might help us to find a better way to protect the NHBD grafts against the preservation and reperfusion injury.

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.

The nitric oxide synthase cofactor tetrahydrobiopterin reduces allograft ischemia-reperfusion injury after lung transplantation

OBJECTIVE

Exogenous nitric oxide reduces ischemia-reperfusion injury after solid organ transplantation. Tetrahydrobiopterin, an essential cofactor for nitric oxide synthases, may restore impaired endothelium-dependent nitric oxide synthesis. We evaluated whether tetrahydrobiopterin administration to the recipient attenuates lung reperfusion injury after transplantation in swine.

METHODS

Unilateral left lung transplantation was performed in 15 weight-matched pigs (24-31 kg). Donor lungs were flushed with 1.5 L cold (1 degrees C) low-potassium-dextran solution and preserved for 20 hours. Group I animals served as controls. Group II and III animals were treated with a bolus of tetrahydrobiopterin (20 mg/kg). In addition, in group III a continuous infusion of tetrahydrobiopterin (10 mg/kg per hour over 5 hours) was given. One hour after reperfusion, the recipient right lung was occluded. Cyclic guanosine monophosphate levels were measured in the pulmonary venous and central venous blood. Extravascular lung water index, hemodynamic variables, lipid peroxidation, and neutrophil migration to the allograft were assessed.

RESULTS

In group III a significant reduction of extravascular lung water was noted in comparison with the controls (P =.0047). Lipid peroxidation in lung allograft tissue was significantly reduced in group II (P =.0021) and group III ( P =. 0077) in comparison with group I. Pulmonary venous levels of cyclic guanosine monophosphate increased up to 23 +/- 1 pmol/mL at 5 hours in group II and up to 40 +/- 1 pmol/mL in group III (group I, 4.1 +/- 0.5 pmol/mL [I vs III]; P <.001), whereas central venous levels of cyclic guanosine monophosphate were unchanged in all groups.

CONCLUSION

Tetrahydrobiopterin administration during lung allograft reperfusion may reduce posttransplantation lung edema and oxygen-derived free radical injury in the graft. This effect is mediated by local enhancement of the nitric oxide/cyclic guanosine monophosphate pathway.

Inhaled NO preadministration modulates local and remote ischemia-reperfusion organ injury in a rat model

Inhaled nitric oxide (iNO) has been shown to have a protective effect in lung ischemia-reperfusion (I/R)-induced injuries. We studied the role of iNO (10 parts/million for 4 h) administered before I/R. In an isolated perfused lung preparation, iNO decreased the extravascular albumin accumulation from 2,059 +/- 522 to 615 +/- 105 microl and prevented the increase in lung wet-to-dry weight ratio. To study the mechanisms of this prevention, we evaluated the role of nitric oxide (NO) transport and lung exposure with matched experiments by using either lungs or blood of animals exposed to iNO and blood or lungs of naive animals. iNO-exposed blood with naive lungs did not limit the extravascular albumin accumulation (2,561 +/- 397 microl), but iNO-exposed lungs showed a leak not significantly different from the group in which both lungs and blood were iNO exposed (855 +/- 224 vs. 615 +/- 105 microl). An improvement in heart I/R left ventricular developed pressure in the animals exposed to iNO showed that blood-transported NO was, however, sufficient to trigger remote organ endothelium and reduce the consequences of a delayed injury. In conclusion, preventive iNO reduces the consequences of lung I/R injuries by a mechanism based on tissue or endothelium triggering.

Perioperative management of patients undergoing lung transplantation

This review focuses on recent developments in the perioperative management of patients undergoing lung transplantation. Relevant current literature and the experience of the Munich Lung Transplant Group were taken into consideration. Recent advances include the use of inhalational nitric oxide for the treatment of early graft dysfunction and the use of aerosolized cyclosporine for the treatment of recurrent and steroid-resistant acute rejection. Opportunistic infections remain a major source of morbidity and mortality in lung transplant recipients.