Prostaglandin E1 or prostacyclin in Euro-Collins solution fails to improve lung preservation

Does reperfusion injury still cause significant mortality after lung transplantation?

OBJECTIVES

Severe reperfusion injury after lung transplantation has mortality rates approaching 40%. The purpose of this investigation was to identify whether our improved 1-year survival after lung transplantation is related to a change in reperfusion injury.

METHODS

We reported in March 2000 that early institution of extracorporeal membrane oxygenation can improve lung transplantation survival. The records of consecutive lung transplant recipients from 1990 to March 2000 (early era, n = 136) were compared with those of recipients from March 2000 to August 2006 (current era, n = 155). Reperfusion injury was defined by an oxygenation index of greater than 7 (where oxygenation index = [Percentage inspired oxygen] x [Mean airway pressure]/[Partial pressure of oxygen]). Risk factors for reperfusion injury, treatment of reperfusion injury, and 30-day mortality were compared between eras by using chi(2), Fisher's, or Student's t tests where appropriate.

RESULTS

Although the incidence of reperfusion injury did not change between the eras, 30-day mortality after lung transplantation improved from 11.8% in the early era to 3.9% in the current era (P = .003). In patients without reperfusion injury, mortality was low in both eras. Patients with reperfusion injury had less severe reperfusion injury (P = .01) and less mortality in the current era (11.4% vs 38.2%, P = .01). Primary pulmonary hypertension was more common in the early era (10% [14/136] vs 3.2% [5/155], P = .02). Graft ischemic time increased from 223.3 +/- 78.5 to 286.32 +/- 88.3 minutes in the current era (P = .0001). The mortality of patients with reperfusion injury requiring extracorporeal membrane oxygenation improved in the current era (80.0% [8/10] vs 25.0% [3/12], P = .01).

CONCLUSION

Improved early survival after lung transplantation is due to less severe reperfusion injury, as well as improvements in survival with extracorporeal membrane oxygenation.

Preischemic iloprost application for improvement of graft preservation: which route is superior in experimental pig lung transplantation: inhaled or intravenous?

BACKGROUND

Optimal allograft protection is essential in lung transplantation to reduce postoperative organ dysfunction. Although intravenous prostanoids are routinely used to ameliorate reperfusion injury, the latest evidence suggests a similar efficacy of inhaled prostacyclin. Therefore, we compared donor lung-pretreatment using inhaled lioprost (Ventavis) with the commonly used intravenous technique.

METHODS

Five pig lungs were each preserved with Perfadex and stored for 27 hours without (group 1) or with (group-2, 100 prior aerosolized of iloprost were (group 3) or iloprost (IV). Following left lung transplantation, hemodynamics, Po(2)/F(i)o(2), compliance, and wet-to-dry ratio were monitored for 6 hours and compared to sham controls using ANOVA analysis with repeated measures.

RESULTS

The mortality was 100% in group 3. All other animals survived (P < .001). Dynamic compliance and PVR were superior in the endobronchially pretreated iloprost group as compared with untreated organs (P < .05), whereas oxygenation was comparable overall W/D-ratio revealed significantly lower lung water in group 2 (P = .027) compared with group 3.

CONCLUSION

Preischemic alveolar deposition of iloprost is superior to IV pretreatment as reflected by significantly improved allograft function. This strategy offers technique to optimize pulmonary preservation.

Does Perfadex Affect Outcomes In Clinical Lung Transplantation?

BACKGROUND

The use of a low-potassium-based preservation solution improves gas exchange in experimental models of lung transplantation. However, its efficacy in reducing the incidence of primary graft dysfunction (PGD) and improving patient outcomes in the clinical setting is controversial.

METHODS

In this study we measured: oxygenation index (OI); International Society of Heart and Lung Transplantation (ISHLT) PGD grades; extubation times; intensive care unit (ICU) and hospital length of stay; 30-day, 90-day and 1-year survival rates; and bronchiolitis obliterans syndrome (BOS)-free survival. We compared 115 consecutive (2001 to 2004) lung recipients who received allografts preserved with Perfadex, a low-potassium dextran (LPD) solution, and compared the results with the previous 116 consecutive (1999 to 2001) lung recipients who received allografts preserved with modified Euro-Collins (MEC) solution. Recipients were classified as having severe PGD (ISHLT Grade III) if the lowest arterial oxygenation (P) to fraction of inspired oxygen (F) (P/F ratio) within 48 hours post-transplantation was <200.

RESULTS

Baseline characteristics of the 2 cohorts were similar except for recipient age (LPD 53.5 vs MEC 49.9 years; p = 0.03). There were no differences in donor age, gender, category of transplant, indication for transplant, use of cardiopulmonary bypass or pre-operative pulmonary artery pressures. When gas-exchange parameters were measured upon arrival to the ICU (T0), at 24 hours post-transplant (T24) and at 48 hours post-transplant (T48), the only significant finding was that the incidence of ISHLT Grade III PGD at T24 was lower in the LPD group compared with the MEC group (8% vs 20%, p = 0.03). The incidence of severe PGD at other timepoints was not statistically different (LPD vs MEC: T0, 17% vs 26%; T0 to T48, 25% vs 31%). Both groups had similar extubation rates at 48 hours post-transplant (LPD 64% vs MEC 67%). The 30-day survival (LPD 93% vs MEC 95%), 90-day survival (LPD 89% vs MEC 89%), 1-year patient survival (LPD 80% vs MEC 77%) and 1-year BOS-free survival (LPD 70% vs MEC 74%) were not statistically different.

CONCLUSIONS

Lung preservation with LPD as compared with MEC does not improve early gas exchange or impact 90-day and 1-year mortality. Continued investigation into lung preservation solution composition is necessary to reduce the incidence of PGD.

Impact of retrograde graft preservation in perfadex-based experimental lung transplantation

OBJECTIVE

Optimal preservation of postischemic organ function is a continuing challenge in clinical lung transplantation. Retrograde instillation of preservation solutions has theoretical advantages to achieve a homogeneous distribution in the lung due to perfusion of both the pulmonary and the bronchial circulation. Thus far, no systematic screening studies followed by in vivo large animal reevaluation including stereological analysis of intrapulmonary edema exist concerning the influence of retrograde preservation on postischemic lung function after preservation with low potassium dextran (LPD) solution (Perfadex).

MATERIALS AND METHODS

For initial screening in an extracorporeal rat model eight lungs, each, were preserved for 4 h using antegrade or retrograde preservation with LPD solution (Perfadex; PER(ant)/PER(ret)). Respiratory and hemodynamic results after reperfusion were compared to low-potassium Euro-Collins (LPEC). For systematic reevaluation, five pig lungs, each, were preserved correspondingly for 27 h, and results were compared to sham-operated control lungs. In both models, edema formation was quantified stereologically. Statistics comprised different ANOVA models.

RESULTS

In both models, use of PER(ret) resulted in significantly higher oxygenation capacity, lower inspiratory pressures, and lower amounts of intraalveolar edema as compared to PER(ant). Results of PER(ret) were not different from sham controls in the in vivo model; furthermore, a continuous retrograde elimination of blood clots from pulmonary microcirculation was noticed.

CONCLUSIONS

Retrograde application of LPD solution (Perfadex) results in significant functional and histological improvement as compared to antegrade perfusion. This innovative technique can be applied very easily in clinical practice and might be an ideal adjunct to further optimize the results after lung transplantation with LPD-based graft protection.

Experimental lung preservation with Perfadex: effect of the NO-donor nitroglycerin on postischemic outcome

OBJECTIVE

Optimal preservation of postischemic graft function is essential in lung transplantation. Antegrade flush perfusion with modified Euro-Collins solution represents the standard technique worldwide. However, growing evidence suggests the superiority of extracellular-type Perfadex solution (Vitrolife AB, Gothenburg, Germany) over Euro-Collins solution. During ischemia and reperfusion, endogenous pulmonary nitric oxide synthesis is decreased, and therefore therapeutic stimulation of the nitric oxide pathway might be beneficial in ameliorating ischemia-reperfusion damage. However, research mainly focuses on nitric oxide supplementation of intracellular solutions, and no studies exist in which the effect of nitroglycerin on Perfadex preservation quality is evaluated.

METHODS

Eight rat lungs each were preserved with Perfadex solution with or without nitroglycerin (0.1 mg/mL) and compared with low-potassium Euro-Collins solution. Postischemic lungs were reventilated and reperfused, and oxygenation capacity, pulmonary vascular resistance, and peak inspiratory pressures were monitored continuously. Stereological analysis was used for evaluation of pulmonary edema and assessment of the vasculature. Statistics were performed by using different analysis of variance models.

RESULTS

The oxygenation capacity of the Perfadex-preserved groups was higher compared with that of the low-potassium Euro-Collins solution group (P <.03). By using nitroglycerin, flush-perfusion time was reduced, and Perfadex solution with nitroglycerin-protected lungs showed superior oxygenation capacity compared with that seen in Perfadex solution-protected organs (P <.01). Furthermore, pulmonary vascular resistance and peak inspiratory pressures were improved in the nitroglycerin group (P <.01). Stereology revealed comparable intrapulmonary edema between groups and a trend toward less vasoconstricted vasculature in Perfadex with nitroglycerin-protected lungs.

CONCLUSIONS

Perfadex solution provides superior lung preservation in terms of postischemic oxygenation capacity than Euro-Collins solution. Supplementation of the nitric oxide pathway by nitroglycerin further enhances functional outcome of Perfadex-preserved organs and might be an easily applicable tool in clinical lung transplantation.

Inhaled NO and prostacyclin during porcine single lung transplantation

BACKGROUND

Increased pulmonary vascular resistance (PVR) and decreased arterial oxygenation frequently complicate lung transplantation. Inhaled nitric oxide (NO) and aerosolized prostacyclin (PGI2) both dilate the pulmonary vasculature and improve oxygenation in adult respiratory distress syndrome. We investigated whether similar effects would occur during early reperfusion of a lung graft.

METHODS

Eighteen pigs underwent left lung transplantation. We measured blood flow distribution, mean pulmonary artery pressure, PVR, and gas exchange in each lung separately. Animals were randomized into three groups to receive NO (10 ppm/30 minutes, 40 ppm/30 minutes), nebulized PGI2 (25 microg/mL/30 minutes, 50 microg/mL/30 minutes), or no drugs (control).

RESULTS

In the transplanted lung, PVR was significantly higher than in the native lung. Pulmonary vascular resistance of the transplanted lung was lower in the NO and PGI2 groups in comparison with the control group. During the first hour of inhalation, NO decreased PVR more than PGI2. Neither drug improved oxygenation in the graft.

CONCLUSIONS

Nitric oxide and PGI2 decreased PVR of the transplanted lung slightly, but the effect did not produce a normal pressure in pulmonary vasculature.

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.

Donor lung pretreatment with prostaglandin E(1) does not improve lung graft preservation

Prostaglandin E(1) (PGE(1)) is widely used to improve early graft function after lung transplantation, but some studies have questioned its benefits. Therefore we evaluated the effect of donor pretreatment with PGE(1) in our porcine model of single lung transplantation. Donors received PGE(1) or placebo intravenously before flushing the pulmonary artery with modified Euro-Collins solution. After cold storage, the excised left lung was transplanted. Ischemic time was 4 h. We used our right side heart bypass model to measure standardized pulmonary vascular resistance and to study blood flow distribution between recipient's native and transplanted lung. Systemic and pulmonary hemodynamics and gas exchange were also measured. After transplantation, pulmonary vascular resistance was significantly higher in the transplanted lung, which received only one fourth of the total pulmonary blood flow. PGE(1) pretreatment did not improve pulmonary hemodynamic parameters, or gas exchange.

8-Br-cGMP is superior to prostaglandin E1 for lung preservation

BACKGROUND

Substitution of the nitric oxide (NO) pathway reduces ischemia/reperfusion injury after lung transplantation. 8-Br-cGMP is a membrane-permeable analogue of cGMP, the second messenger of NO. In this study, we evaluated the effect of administration of 8-Br-cGMP in the flush solution on early graft function.

METHODS

Unilateral left lung transplantation was performed in 10 weight-matched pairs of outbred pigs (24 to 31 kg). Donor lungs were flushed with 1.5 L cold (1 degree C) low potassium dextrane (LPD) solution and preserved for 20 hours. In group I (n = 5), 8-Br-cGMP (1 mg/kg) was added to the flush solution. In group II (n = 5), 8 microg/kg prostaglandin E1 (PGE1) was injected into the pulmonary artery (PA) before flush. One hour after reperfusion, the recipients' contralateral right PA and bronchus were ligated to assess graft function only. cGMP levels in the PA and pulmonary vein were measured. Extravascular lung water index (EVLWI), pulmonary vascular resistance, mean PA pressure, and gas exchange (PaO2) were assessed during a 5-hour observation period. Lipid peroxidation (thiobarbituric acid-reactive substance) and neutrophil migration to the allograft (myeloperoxidase activity) were measured at the end of the assessment.

RESULTS

In group I, a significant reduction of EVLWI (group I, 6.7 +/- 1.0 mL/kg vs group II, 10.1 +/- 0.6 ml/kg after 2 hours of reperfusion; p = 0.022), TBARS (group I, 65.6 +/- 10.0 pmol/g vs group II, 120.8 +/- 7.2 pmol/g, p = 0.0039), and MPO activity (group I, 0.8 +/- 0.1 change in optical density, (deltaOD)/mg/min vs group II, 1.7 +/- 0.3 deltaOD/mg/min, p = 0.036) was noted in comparison with group II. PaO2 levels tended to be higher in cGMP-treated animals, but the changes were not significant. Hemodynamic parameters did not differ between groups.

CONCLUSIONS

In this large animal model of lung allograft ischemia/reperfusion injury, 8-Br-cGMP as additive to the flush solution improves posttransplant lung edema, lipid peroxidation, and neutrophil migration to the allograft. This effect is not attributable to improved flush by vasodilation, as we compared 8-Br-cGMP with PGE1 given before flush in control animals.

Calcium channel blocker enhances lung preservation

BACKGROUND

The standard program for lung transplantation employs PGE1 pretreatment for donor lungs, but its efficacy remains controversial. Calcium channel blocker has been reported more effective for reducing potassium-induced vasoconstriction. We investigate the efficacy of calcium channel blocker in the initial lung flush using rat lung transplant model.

METHODS

The excised rat lungs (n = 30) were flushed with either University of Wisconsin solution (UWS) with a prior injection of 50 microg/kg PGE1 into the pulmonary artery (UWS + PGE1; n = 7), UWS only (UWS; n = 7), or UWS containing 10(-6) M nifedipine (UWS + Nif; n = 8). After storage (4 degrees C) for 24 hours, all lungs were reperfused for 2 hours using an isolated, pulsatile blood perfused lung model. Control lungs (n = 8) were reperfused immediately after harvest. Blood gas analysis and shunt fraction, lung airway resistance, dynamic lung compliance, and pulmonary vascular resistance were assessed.

RESULTS

The pO2 at 30 minutes after reperfusion in the control, UWS, UWS + PGE1, and UWS + Nif group were 88.0 +/- 3.2, 49.6 +/- 2.2, 52.0 +/- 2.4, 85.1 +/- 2.1 (mmHg), respectively. Until 30 minutes after reperfusion, the pO2 in UWS and UWS + PGE1 group were significantly lower than those in UWS + Nif group (p < .001). Shunt fraction, lung airway resistance, and dynamic lung compliance also demonstrated the superiority of UWS + Nif group.

CONCLUSIONS

The early graft function after storage was significantly enhanced in lungs flushed with UWS containing nifedipine. Calcium channel blocker is more effective than PGE1 in reducing the potassium-induced vasoconstriction. Optimal composition of the flush may require both calcium channel blocker for pulmonary vasodilation and PGE1 for pulmonary protection by non-vasodilatory mechanisms.

Hypothermic preservation of isolated rat lungs in modified bicarbonate buffer, EuroCollins solution or St Thomas' Hospital cardioplegic solution

OBJECTIVES

Inadequate preservation solutions limit lung storage times and, consequently, transplant programs. To address this problem we established an isolated, ventilated and perfused rat lung preparation. Here we report the effects of hypothermic storage in EuroCollins solution, St Thomas' Hospital cardioplegic solution and a modified bicarbonate buffer solution.

METHODS

Lungs from male Wistar rats (230-330 g) were perfused via the pulmonary artery with modified bicarbonate buffer (37 degrees C, 15 ml/min, constant flow) and ventilated by positive pressure (tidal volume:1.6-1.8 ml, 80 breaths/min). Vascular resistance (pulmonary artery pressure:perfusate flow ratio) and airways compliance (tidal volume:tracheal pressure ratio) were measured. After a control perfusion period (20 min), lungs were flushed with, then immersed in, bicarbonate buffer (4 degrees C) for varying periods (0-24 h). After storage, lung function was assessed during 20 min reperfusion. Having established a suitable period for study, storage in EuroCollins, St Thomas' Hospital cardioplegic solution or bicarbonate buffer were compared.

RESULTS

Pulmonary compliance (ml/cmH2O) was significantly (P < 0.05) reduced in lungs stored for 6 h in modified bicarbonate buffer (0.026 +/- 0.008), EuroCollins solution (0.013 +/- 0.002) or St Thomas' Hospital solution (0.025 +/- 0.005) compared to unstored lungs (0.068 +/- 0.007). Vascular resistance, (1.32 +/- 0.13 cmH2O/ml per min) in unstored lungs, was similar in lungs stored in St Thomas' Hospital solution but increased significantly in lungs stored in modified bicarbonate buffer (3.22 +/- 0.78 cmH2O/ml per min) or EuroCollins solution (4.66 +/- 0.57 cmH2O/ml per min).

CONCLUSIONS

Hypothermic storage of rat lungs for 6 h in modified bicarbonate buffer or St Thomas' Hospital solution causes less increase in vascular resistance on reperfusion than EuroCollins solution.

Relative importance of prostaglandin/cyclic adenosine monophosphate and nitric oxide/cyclic guanosine monophosphate pathways in lung preservation

BACKGROUND

Modulation of vascular tone and platelet and neutrophil function through the prostaglandin/cyclic adenosine monophosphate or nitric oxide/cyclic guanosine monophosphate pathway can benefit lung graft function. The relative importance of these pathways is unclear.

METHODS

Rat lung grafts (5 per group) were studied in an ex vivo reperfusion model. Group I grafts were pretreated with prostacyclin (20 ng.kg-1.min-1), flushed with cold Euro-Collins solution containing prostacyclin (200 micrograms/L), and reperfused immediately for 1 hour. Group II grafts were similarly procured but were stored at 4 degrees C for 6 hours before reperfusion. In group III, no prostacyclin therapy was used; instead, the nitric oxide donor glyceryl trinitrate (0.1 mg/mL) was added to the flush/storage solution, and the grafts were stored for 6 hours.

RESULTS

Group II grafts performed poorly compared with those in group I, with substantial deterioration of oxygenation and blood flow and elevation of pulmonary artery pressure, peak airway pressure, and wet to dry weight ratio. In contrast, graft function in group III was similar to that in controls.

CONCLUSIONS

Lung graft integrity after storage in Euro-Collins solution was better preserved by glyceryl trinitrate than by prostacyclin in this model.