Standard donor lung procurement with normothermic ex vivo lung perfusion: A prospective randomized clinical trial

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ORIGINAL CLINICAL SCIENCE

Standard donor lung procurement with normothermic ex vivo lung perfusion: A prospective randomized clinical trial Alexis Slama, MD,a,b Lukas Schillab, MD,a Maximilian Barta, MD,a Aris Benedek, MS,a Andreas Mitterbauer, MD,a Konrad Hoetzenecker, MD, PhD,a Shahrokh Taghavi, MD,a Gyoergy Lang, MD, PhD,a,c Jose Matilla, MD,a Hendrik Ankersmit, MD, MBA,a Helmut Hager, MD,d Georg Roth, MD,d Walter Klepetko, MD,a and Clemens Aigner, MD, MBAa,b From the aDepartment of Thoracic Surgery, Medical University of Vienna, Vienna, Austria; bDepartment of Thoracic Surgery and Surgical Endoscopy, Ruhrlandklinik–University Clinic Essen, Essen, Germany; cDepartment of Thoracic Surgery, Semmelweis University, National Institute of Oncology, Budapest, Hungary; and the dDepartment of Anaesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Vienna, Austria.

KEYWORDS: ex vivo lung perfusion; donor organ preservation; standard donor lungs; lung transplantation; preservation time

BACKGROUND: Ex vivo lung perfusion (EVLP) was primarily developed for evaluation of impaired donor lungs. The good clinical results raise the question for its possible impact on lungs meeting standard criteria. Before application of EVLP on such lungs enters routine clinical practice, it must be demonstrated whether EVLP would affect or improve outcome when used in standard donor lungs. We performed a prospective randomized trial to investigate the role of EVLP in standard lung transplantation (Tx). METHODS: This prospective randomized clinical trial compared patients who underwent Tx with ex vivo evaluated donor lungs with an equivalent patient population without previous EVLP. RESULTS: From October 2013 to May 2015, 193 lung Tx were performed at the Medical University of Vienna. During this period, 80 recipient/donor pairs that met the inclusion criteria were included in this trial, 41 pairs in the control group, and 39 in the EVLP group. In the EVLP group, 4 lungs (10.2%) ultimately did not qualify for Tx and were rejected for lung Tx owing to technical reasons (n ¼ 2) and quality criteria (n ¼ 2). Donor and recipient characteristics were comparable in both groups. Total cold ischemic time in the EVLP group was significantly longer for both implanted lungs (first side, 372 minutes vs 291 minutes, p o 0.001; second side, 437 minutes vs 370 minutes, p ¼ 0.001); median duration of surgery showed no differences (277 minutes vs 275 minutes). Median oxygen partial pressure/fraction of inspired oxygen ratio at 24 hours after Tx was 516 (range, 280–557) in the EVLP group and 491 (range, 352–575) in the control group (p ¼ 0.63). Incidence of primary graft dysfunction 41 was lower in the EVLP group at all time points compared with the control group (24 hours, 5.7% vs 19.5%, p ¼ 0.10), and need for post-operative prolonged extracorporeal membrane oxygenation was lower in the EVLP group (5.7% vs 12.2%, p ¼ 0.44). Short-term clinical outcomes did not differ between recipients in the 2 groups. Patients remained intubated (1.6 days vs 1.6 days, p ¼ 0.67), in the intensive care unit (6 days vs 6 days, p ¼ 0.76), and in the hospital (23 days vs 19 days, p ¼ 0.42) for a comparable period of time. The 30-day survival was 97.1% vs 100% (p ¼ 0.46).

Reprint requests: Clemens Aigner, MD, MBA, FETCS, Department of Thoracic Surgery and Surgical Endoscopy, Ruhrlandklinik–University Clinic Essen, Tueschener Weg 40, Essen 45239, Germany. Telephone: þ49 201 433 4011. Fax: þ49 201 433 4019. E-mail address: [email protected] 1053-2498/$ - see front matter r 2017 International Society for Heart and Lung Transplantation. All rights reserved. http://dx.doi.org/10.1016/j.healun.2017.02.011

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The Journal of Heart and Lung Transplantation, Vol ], No ], Month ]]]] CONCLUSIONS: This study provides evidence that EVLP can safely be used in standard donor lungs. Functional results and perioperative outcome are comparable to those achieved with standard donor lung preservation techniques. As an evaluation tool, EVLP allows clinicians to identify and to possibly exclude lungs with functional impairment. Finally, EVLP can safely extend total preservation time. J Heart Lung Transplant ]]]];]:]]]–]]] r 2017 International Society for Heart and Lung Transplantation. All rights reserved.

Ex vivo lung perfusion (EVLP) is a relatively new approach for procurement of donor lungs. It has been developed with the goals to evaluate the quality of grafts that have not been accessible for full functional testing before harvesting and to potentially improve the function of organs that by established criteria are not suitable for lung transplantation (Tx).1 First clinical results have been very promising and have demonstrated that both goals can be achieved, which consequently has resulted in enlargement of the donor organ pool. In fact, EVLP-treated extended criteria donor lungs performed equivalently to standard criteria donor lungs.1–3 Based on these findings, future concepts of EVLP foresee specific treatment of donor lungs, for example, with antibiotics or gene therapy. In addition, as the time on normothermic EVLP cannot be accounted for as “ischemic time,” EVLP could also play an important role for expansion of the procurement time. This enormous clinical potential for the use of EVLP in functionally impaired donor lungs raises the question for its possible role in standard quality lungs. However, before such a role can be better defined, it must be demonstrated whether EVLP results in superior outcome when used in standard donor lungs. Thus, we performed a prospective randomized trial to investigate the role of EVLP in standard lung Tx.

Methods Study design The study was designed in a prospective, randomized fashion and was performed as a single-center trial at the Medical University of Vienna. All consecutive donor lungs in the study period meeting standard donor lung acceptance criteria that were allocated to a recipient fulfilling the study inclusion criteria were randomly assigned to 2 groups (EVLP group and control group with standard preservation). All lungs were procured with the established standard cold preservation technique (cold Perfadex flush [XVIVO AB]) and were transported to our transplant center. On arrival, donor lungs in the EVLP group were subjected to 4 hours of normothermic EVLP, followed by a final assessment and subsequent implantation if no further reason for exclusion occurred at this point. Lungs in the control group (standard preservation) were transplanted immediately on arrival to our center. The study was performed in accordance with the Declaration of Helsinki and approved by the ethics committee of the Medical University of Vienna (1360/2013). Written informed consent was obtained before randomization from all subsequently included recipients. Organ allocation was performed according to the Eurotransplant allocation policy and national rules. The decision for inclusion in the study was made after the organ was allocated.

Randomization was performed online using the standard software program of the Medical University of Vienna (www.meduniwien. ac.at/randomizer). After the transplant procedure, all recipients in both study groups received routine medical care. This investigator-driven study was sponsored by XVIVO AB, Gothen burg, Sweden. The sponsor was not involved in the execution of the trial or in the data analysis.

Inclusion and exclusion criteria Donor lungs were defined as “standard” and thereby eligible for inclusion whenever they met all of the following criteria:  Donation after brain death  Arterial oxygen partial pressure (PaO2)/fraction of inspired

oxygen (FIO2) ratio on 100% FIO2 4300 mm Hg

 Donor age 418 years  Clear chest x-ray

 No major purulent secretions found during bronchoscopy  No major mechanical lung trauma  No gross gastric aspiration  No evidence of significant infection  No evidence for human immunodeficiency virus, hepatitis B

virus, hepatitis C virus, or any other relevant viral disease  No history or evidence of malignant disease

All recipients on our waiting list were considered for study inclusion except for patients presenting with any of the following pre-defined exclusion criteria:  Consent not given  Pediatric recipient o18 years old  Diagnosis of primary pulmonary arterial hypertension (Dana

Point classification group 1.1)  Patient ventilated or on mechanical support before Tx  Previous Tx of any solid organ  Need for combined heart-lung Tx, lobar lung Tx, or single-

lung Tx

Logistics, explantation procedure, and randomization The initial donor lung assessment and procurement procedure was carried out according to our routine clinical protocol.1 Donors received 1 g of methylprednisolone, 25,000 IU of heparin and 0.5 mg of prostaglandin I2 (epoprostenol [Flolan]) before aortic cross clamping. Antegrade and retrograde organ perfusion with buffered Perfadex solution was performed for preservation. Special attention was paid to preserve sufficiently sized vascular and tracheal cuffs to allow for ex vivo cannulation. The final decision for suitability for Tx was discussed with the implanting surgeon. Randomization was performed if both the donor lungs and the

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EVLP in Standard Lung Transplantation

3 fully inflated with no need for additional manual recruitment. Moreover, 500 ml of perfusate was withdrawn and replenished at 60, 120, and 180 minutes of perfusion immediately after gas analysis was performed. If at any point in time a pH o7 was detected in the gas analysis, 20 ml of bicarbonate were added to the circuit. If the glucose concentration decreased to o100 mg/dl, 10 ml of glucose 33% was added. During the 4 hours of perfusion, functional parameters were recorded every 30 minutes. Before every full hour, FIO2 was set to 100% for 15 minutes, followed by a gas analysis of the perfusion solution. The following parameters were measured and recorded:  Pulmonary artery flow (PAF) (liters/min)  Mean pulmonary artery pressure (PAP) (mm Hg)  Left atrial pressure (LAP) (mm Hg)  Pulmonary vascular resistance (PVR ¼ [PAP  LAP]  80/

PAF) (dyne ∙ sec ∙ cm5)

 Mean, peak, and plateau airway pressure (mAWP, peak AWP,

platAWP) (cm H2O)  Dynamic compliance (ml/cm H2O)  Perfusate gas analysis—inflow (pulmonary artery) and outflow

(pulmonary vein) PO2, PCO2, and pH

Figure 1

Algorithm for randomization and group assignment.

assigned recipient met all inclusion criteria. An online randomization tool (www.meduniwien.ac.at/randomizer) was used (2 groups; 1:1, no balancing, no stratification), and the results were communicated to the surgeon performing the procurement. Donor lungs randomly assigned to the ex vivo group were packaged en bloc. Lungs assigned to the control group were separated on the back-table and placed in separate storage boxes before transport (Figure 1).

Ex vivo lung perfusion technique Lungs in the treatment arm were perfused broadly in line with the clinical protocol described by the Toronto group2,3 and used by our own group in previous work.4 The perfusion system consisted of a 3/8-inch heparin-coated perfusion circuit (Carmeda; Medtronic) driven by a conventional extracorporeal membrane oxygenation (ECMO) device (Bio-Console 560; Medtronic). Lung ventilation and measurement of functional ventilation parameters was achieved with standard operating room equipment (Primus or Infinity [both Dräger]; Hemomed [Siemens]). The circuit was primed with 2 liters of STEEN Solution (XVIVO AB) heated to 201C. In addition, heparin 10,000 IU, cefuroxime 3 g, and methylprednisolone 500 mg were added to the perfusate. After cannulation of the left atrium and the main pulmonary artery, a retrograde perfusion (150 ml/min) was applied to de-air the lung vasculature. Antegrade perfusion was then initiated and gradually increased over 50 minutes to reach a maximum of 40% of the estimated donor cardiac output. During the first 20 minutes, the temperature was increased to 371C and ventilation of the donor lung was started (FIO2: 21%). De-oxygenation of the perfusate was achieved with the membrane gas exchanger (gas mixture: N2 86%, O2 6%, CO2 8%) with a fixed gas flow of 4 liters/min. Ventilation was started with a tidal volume of 7 ml/kg, inspiratory-expiratory ratio 1:2, frequency of 8/min, and FIO2 of 21%. Recruitment of atelectasis was achieved by maintaining the positive end expiratory pressure to a level at which the lungs stayed

The development of these functional parameters was monitored, and in cases of a deterioration of the delta PO2 of 420% compared with baseline values, the lungs were considered unsuitable for Tx. Furthermore, a macroscopic inspection by the implanting surgeon was performed after 4 hours of EVLP before final acceptance of the organ. All lungs showing stable or improving functional parameters with a delta PO2 4350 mm Hg and a satisfactory macroscopic evaluation at the final evaluation (time [T] ¼ 4 hours) were subsequently transplanted. These lungs were cooled down to 151C on the circuit and then flushed again with 1.5 liters of cold (41C) Perfadex solution before being separated and stored on ice until implantation. Modifications to the initially described Toronto method, such as the lack of manual recruitment and the substitution of glucose, bicarbonate, and STEEN solution, were based on our previous experience with marginal donor lungs.

Transplant procedure All Tx were performed as bilateral sequential lung Tx using routine technique with intraoperative central venoarterial ECMO support. According to the standard protocol of our department, central venoarterial ECMO was used in all procedures and discontinued at the end of the implantation. After decannulation, arterial and venous ECMO lines were connected on the table, and the ECMO was kept running for 1 hour. If signs of insufficient graft function were observed during this period, a peripheral cannulation in the groin was performed, and the same ECMO circuit was used for prophylactic prolonged ECMO support. Criteria of insufficient intraoperative graft function were defined as PO2/FIO2 ratio o100 in combination with a mean PAP 466% of mean systemic blood pressure.

Post–lung Tx assessment The number of patients needing prolonged ECMO according to the aforementioned standard criteria was recorded in both groups. These patients were excluded from the calculation of PO2/FIO2 ratios. In all other patients, blood gas analyses and primary graft dysfunction (PGD) scores according to the International Society for Heart and Lung Transplantation (ISHLT) classification5,6 were assessed at the pre-defined time points (T0, T12, T24, T48, and T72 hours after arrival in the intensive care unit [ICU]). For every

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of EVLP, reperfusion of each lung). Total preservation time within the EVLP group was defined as cold ischemic time (CIT) before EVLP (CIT1) þ duration of EVLP þ time until reperfusion within the recipient (CIT2).

time point, arterial blood for blood gas analysis was drawn with a standard setting of 100% FIO2 and positive end expiratory pressure 5 mm Hg or as high as clinically required. Blood gas measurements were performed only in intubated patients.

Statistical analysis

Study end-points

All statistics were calculated with IBM SPSS Statistics for Windows, Version 22 (IBM Corp.). Confidence intervals were stated at 95%; p-values o 0.05 were considered statistically significant. Numerical data were compared with non-parametric Mann-Whitney U test. Categorical data were analyzed by means of chi-square test or Fisher’s exact test (if observed values were o5). Data were not corrected for type I error. Unless stated otherwise, results are expressed as EVLP vs control (standard preservation). Sample size calculation was performed assuming a possible dropout rate of 5%. A sample size of 38 in each group would have 80% power to detect a difference in means for the PaO2/FIO2 ratio of 32.6. This calculation assumes a common SD of 50 using a 2-group t-test with a 5% 2-sided significance level. With a dropout

The primary study end-points were PaO2/FIO2 ratio (FIO2 ¼ 1.0) and PGD 41 (including need for prolonged ECMO) at T24 hours after lung Tx. Secondary end-points were as follows:  PaO2/FIO2 ratio measured at T12, T48, and T72 hours post-Tx  PGD scores at T12, T24, T48, and T72 hours post-Tx  Duration of intubation  Length of ICU stay  Hospitalization time  30-day mortality

For comparison of durations between the groups, all relevant time points were recorded (aortic clamp, beginning of EVLP, end Table 1

Donor, Recipient, and Intraoperative Characteristics

Donor variables Gender Age, years Height, cm Weight, kg BMI Causes of death, n (%) Traumatic brain injury Non-traumatic cerebral bleedinga Otherb Intubation time, days Last PaO2 at FIO2 ¼ 1.0 Last PaCO2 at FIO2 ¼ 1.0 Recipient variables Gender Age, years Height, cm Weight, kg BMI Diagnosis, n (%) Emphysemac Fibrosis Cystic fibrosis Other Waiting time, days LAS Intraoperative variables Size reduction, n (%) Surgery duration, minutes Packed red blood cells FFP

EVLP group (n ¼ 35)

Control group (n ¼ 41)

p-values

Median

Range

Median

Range

1 vs 2

18 F/17 M 45 170 72 24.5

18–71 156–195 50–95 19–31

12 F/27 M 44 175 75 24.8

19–76 150–193 45–110 17–33

0.049 0.67 0.76 0.34 0.35 0.08

9 (25.7%) 22 (62.9%) 4 (11.4%) 2.9 514 39.9

1.3–22 290–626 28.6–54.5

17 (41.5%) 14 (34.2%) 10 (24.4%) 2.7 463 39.7

1–32.5 232–765 31–57.8

0.74 0.1 0.97

18 F/17 M 52.9 169 60 21

21–68.3 153–189 39–91 14.7–29

20 F/21 M 54.2 172 63 21.6

19.7–66.7 155–193 41–99 14.8–29

0.82 0.62 0.26 0.43 0.68 0.53

14 (40.0%) 9 (25.7%) 7 (20.0%) 5 (14.3%) 77 34.1

1–699 20.5–82.9

21 (51.2%) 7 (17.1%) 10 (24.4%) 3 (7.3%) 91 34.4

1–685 27.9–59.6

0.48 0.63

21 (60%) 277 4 10

172–541 0–28 3–38

21 (51%) 275 3 10

184–390 0–10 0–18

0.75 0.69 0.53 0.26

BMI, body mass index; EVLP, ex vivo lung perfusion; F, female; FIO2, fraction of inspired oxygen; FFP, fresh frozen plasma; LAS, lung allocation score; M, male; PaO2, arterial oxygen partial pressure; PaCO2, arterial carbon dioxide partial pressure. a Non-traumatic cerebral bleeding includes intracerebral bleeding and subarachnoid bleeding. b Other causes of death include cerebrovascular stroke and hypoxia. c Emphysema as a recipient diagnosis includes chronic obstructive pulmonary disease and alpha1-antitrypsin deficiency.

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rate of 5%, 40 patients per group would have to be randomly assigned, that is, 80 patients in total. These figures were assumptions based on our previous experience with EVLP.

at this stage; nevertheless, they were accepted as standard donors in the study, as this is our standard clinical practice.

Results

Recipient data and EVLP characteristics

From October 2013 to May 2015, 193 lung Tx were performed at the Medical University of Vienna. During this study period, 80 recipient/donor pairs that met the inclusion criteria were included in this trial; 41 pairs were randomly assigned to the control group, and 39 pairs were randomly assigned to the EVLP group. Within the EVLP group, 4 lungs (10.2%) were found not to qualify for Tx and had to be rejected for lung Tx owing to technical reasons (n ¼ 2) and quality criteria (n ¼ 2). There were 76 Tx performed within this trial (EVLP, n ¼ 35; control, n ¼ 41).

The 2 groups had comparable demographic data, indications for Tx, waiting time, and lung allocation score (Table 1). In the EVLP group, median CIT1 was 220 minutes (range, 119–379 minutes). EVLP perfusion was performed for a median duration of 266 minutes (range, 245–329 minutes). In some lungs, prolongation of perfusion beyond the final measurement and decision point at 4 hours was performed for logistical reasons. At the time of EVLP initiation, 2 pairs of lungs had to be excluded from the study because of technical reasons that did not allow EVLP in a standardized way. One lung, which came from a donor with severe adhesions, had multiple injuries at the level of lobar and segmental arteries, which resulted in a massive perfusate leak within the first minutes of EVLP. The lung was subsequently excluded from the study and could not be used for Tx. Another pair of lungs had an anomalous return of the right upper lobe vein into the superior vena cava, which remained undetected during harvesting. Because the stump of the anomalous vein was too short to allow for reconstruction, EVLP became technically impossible, and the lung was excluded from the study.

Donor demographics There were no statistically significant differences in donor demographics between the groups (Table 1), particularly not in oxygenation before procurement (mean PaO2 514 mm Hg vs 463 mm Hg, mean arterial carbon dioxide partial pressure 39.9 mm Hg vs 39.7 mm Hg at FIO2 ¼ 1.0, positive end expiratory pressure ¼ 5 mm Hg). In all donors, the last PaO2/FIO2 ratio obtained at the table after performing recruitment maneuvers was used. In some donors, the ratio dropped below 300 secondary to hemodynamic impairments

Figure 2

Functional parameters of perfused lungs in the EVLP group. Boxplots and outliers are plotted according to the Tukey method.

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Figure 3

Detailed functional parameters of the declined lungs.

Two lungs did not reach the functional standard acceptance criteria defined in our protocol (i.e., delta PO2 4350 mm Hg) at the final assessment at 240 minutes. Although parameter deviation was marginal (Figure 2), additional signs of increasing fluid accumulation within the lungs resulted in the clinical decision not to use them for implantation. The remaining 35 lungs showed constant functional parameters over time. Gas exchange values (delta PO2 and mixed venous partial pressure of oxygen), PAP, PVR, peak AWP, and dynamic compliance remained stable throughout the entire perfusion period. Together with a satisfactory macroscopic appearance of the lungs, acceptance criteria were met at 240 minutes (Figures 2 and 3).

Intraoperative characteristics Most transplant procedures were started on the recipient’s right side (n ¼ 33 vs n ¼ 40; 94.3% vs 97.7%). In 42 cases, an intraoperative middle lobe and/or lingula resection was performed to reduce the implanted lung volume (60% vs 51%). Regarding the intraoperative transfusion of blood products, no significant differences were found between the 2 groups (red blood cells, 4 vs 3; fresh frozen plasma, 10 vs 10). All transplant procedures were performed on central venoarterial ECMO support. Within the EVLP group, the total CIT (duration from aortic clamp to reperfusion within the recipient minus the duration of EVLP) was significantly longer for both implanted lungs (first side, 372 minutes vs 291 minutes, p o 0.001; second side 437 minutes vs 370 minutes; p ¼ 0.001), whereas the median surgery duration showed no differences (277 minutes vs 275 minutes) (Table 2).

Clinical outcomes Need for prolonged ECMO In 7 patients, intraoperative ECMO was prolonged directly into the post-operative period by transfer of the central

cannulation into the groin. In the EVLP group, 2 patients (5.7%) needed prolongation of ECMO support for exclusively hemodynamic reasons after complicated operative courses and significant intraoperative blood transfusion, mainly caused by severe adhesions after previous surgery and pleurodesis (Table 3). The function of the transplanted lungs in both patients was remarkably undisturbed, based on normal ventilation parameters and absence of signs of parenchymal damage on post-operative x-ray. Control of the bleeding and stabilization of the situation became impossible in 1 patient, and the patient died within 24 hours. The other patient required ECMO for 7 days. All other patients in the EVLP group showed functional parameters at the end of implantation that were well above our criteria for prophylactic prolongation of ECMO. In the control group, 5 patients (12.2%) presented with functional parameters (PaO2/FIO2 ratio o100 and mean PAP 466% of systemic pressure) that met our criteria for prophylactic prolongation of ECMO into the post-operative period. ECMO was switched to the femoral position and prolonged for 1–3 days (mean 2 days). The presence of relevant graft dysfunction was also confirmed by parenchymal infiltrates on chest x-ray on arrival of the patients in the ICU. Besides these prolonged ECMO cases, no further need for ECMO implantation occurred at any time during the post-operative course.

PO2/FIO2 ratio and incidence of PGD Median PO2/FIO2 ratio (measured in patients without ECMO) at T24 hours (primary end-point) was 516 (range, 280–557) in the EVLP group and 491 (range, 352–575) in the control group (p ¼ 0.63). The difference between the 2 groups at all other time points did also not reach statistical significance (Table 4). Calculation of post-operative PGD rates in both groups revealed that the only patients with PGD 41 by criteria in the EVLP group were the 2 patients

Slama et al. Table 2

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Comparison of Durations Between Both Groups

Aortic cross clamp to EVLP (CIT1) Duration of EVLP End of EVLP to first reperfusion End of EVLP to second reperfusion (CIT2) Aortic clamp to first reperfusion Aortic clamp to second reperfusion Total CIT of the first side Total CIT of the second side Duration of surgerya

EVLP group (n ¼ 35)

Control group (n ¼ 41)

p-values

Median

Range

Median

Range

1 vs 2

220 266 133 212 642 716 372 437 277

119–379 245–329 80–238 119–325 517–766 566–894 235–499 305–629 172–541

291 370 291 370 275

212–456 270–568 212–456 270–568 184–390

o0.001 o0.001 o0.001 0.001 0.69

CIT, cold ischemic time; EVLP, ex vivo lung perfusion. All data are given in minutes. a Duration of surgery is from skin incision to skin suture within the recipient.

on prolonged ECMO. No other patients in the EVLP group developed a PGD 41 during the ICU stay. In the control group, 8 patients (19.5%), the 5 patients with prolonged ECMO and 3 additional patients, presented with PGD 41 at T12 hours. However, this number quickly resolved to 7 (17.1%) at T24 hours, 4 (9.8%) at T48 hours, and 1 (2.4%) at T72 hours. The incidence of PGD 41 was lower in the EVLP group at all time points (4%–14%) compared with the control group, but this difference did not reach statistical significance.

Clinical course Short-term clinical outcomes did not differ between recipients in the 2 groups. Patients remained intubated (1.6 days vs 1.6 days), in the ICU (6 days vs 6 days), and in the hospital (23 days vs 19 days) for a comparable period. The only death within the first 30 post-operative days occurred in the EVLP group in the patient mentioned before, who died 24 hours after the operation related to hemorrhage secondary to complex operative problems but preserved lung function. There were no deaths in the control group within 30 days. Within 90 days, 2 more patients in the EVLP group died of infections in our hospital on postoperative day 61 and postoperative day 80 (the patient who needed 7 days ECMO support). Table 3

Discussion EVLP has been developed with the aim to re-evaluate and improve function of donor lungs that do not meet standard functional acceptance criteria. EVLP likely acts through many different mechanisms, including opening of atelectatic areas, reduction of intrapulmonary shunt, decrease of extravascular lung water, and reduction of circulating cytokines.4,7 The proof of this concept has been provided in a number of experimental investigations,2,8 which resulted in the clinical application of the method by the Toronto Lung Transplant Program3 and several other groups.4,9–14 In these reports, EVLP was demonstrated to be a safe and reliable method to improve the function of marginal donor lungs. Moreover, it became evident that EVLP is a perfect tool to evaluate the quality of uncontrolled donor lungs after circulatory death.15–17 These findings resulted in increasingly widespread use of EVLP, which has helped to increase the donor organ pool. This positive experience in marginal and uncontrolled donor lungs3,4,9,14,18,19 raises the question about a potential role of EVLP in standard lung Tx. There are a number of potentially positive aspects of EVLP in standard lung procurement. Extension of the storage time would be 1 important aspect, as the lung is supplied with nutrients and oxygen during EVLP, and storage times well beyond the current practice of 4 hours could become realistic.

Post-Operative Outcome After Lung Transplantation

Post-operative intubation, days Time in ICU, days Hospitalization time, days Post-operative ECMO, n (%) ECMO duration, days, median (range) 30-day survival, n (%) Successful hospital discharge, n (%)

EVLP group (n ¼ 35)

Control group (n ¼ 41)

Median

Range

Median

Range

p-values (Fisher)

1.6 6 23 2 (5.7%) 4 (1–7) 34 (97.1%) 32 (91.4%)

0.3–17.7 3–41 8–74

1.6 6 19 5 (12.2%) 2 (1–3) 41 (100%) 41 (100%)

0.2–4.8 3–30 8–111

0.67 0.76 0.42 0.44

ECMO, extracorporeal membrane oxygenation; EVLP, ex vivo lung perfusion; ICU, intensive care unit.

0.46 0.93

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Oxygen Partial Pressure/Fraction of Inspired Oxygen Ratios and Primary Graft Dysfunction Grades EVLP group (n ¼ 35)

T12 PaO2, mm Hg T12 PGD 41, n (%) T24 PaO2, mm Hg T24 PGD 41, n (%) T48 PaO2, mm Hg T48 PGD 41, n (%) T72 PaO2, mm Hg T72PGD 41, n (%)

Control group (n ¼ 41)

Median

Range

Median

Range

p-values (Fisher)

488 2 (5.7%) 516 2 (5.7%) 477 1 (2.9%) 403 1 (2.9%)

341–578

469 8 (19.5%) 491 7 (17.1%) 490 4 (9.8%) 451 1 (2.4%)

114–576

0.17 0.10 0.63 0.17 0.92 0.37 0.96 1.00

280–557 362–530 341–558

352–575 247–547 295–590

EVLP, ex vivo lung perfusion; PaO2, arterial oxygen partial pressure; PGD, primary graft dysfunction; T12, T24, T48, and T72, 12 hours, 24 hours, 48 hours, and 72 hours post-operatively. PaO2 measured after 10 minutes of fraction of inspired oxygen ¼ 1.0.

Reduction of the rate of significant PGD (PGD 41), which currently is reported to be in the range of up to 25%,20 would be another positive aspect. This could be achieved not only through further improving the donor lung quality but also by detecting impairments previously unrecognized during standard procurement and excluding these lungs from implantation. Finally, active pharmacologic or advanced biologic treatment of donor lungs during EVLP could become a valuable aspect of EVLP use as well. As a first step to pave the way for more widespread use and investigation of EVLP in standard donor lungs, we intended to demonstrate the effects of its use in a prospective series of lung Tx. To our knowledge, this is the first prospective randomized trial that evaluates normothermic acellular EVLP in standard donor lungs before Tx. A crucial step in designing such a study is the choice of appropriate outcome parameters. The only internationally accepted classification for donor lung impairment at the present time is the PGD score, a gross classification into 4 groups based on PaO2/FIO2 ratio and the presence of radiographic infiltrates consistent with pulmonary edema. However, the accuracy of PGD classification is limited by investigator-dependent interpretation of the chest x-ray5 and significant interobserver variability.21 In addition, the automatic classification of any patient on extracorporeal support as PGD 3, regardless of the underlying reason, does not sufficiently describe the presence of PGD in all situations, especially in current clinical practice where ECMO can be applied as a prophylactic strategy22–24 or for underlying cardiac problems. All this makes a uniform and comprehensive description of the functional status of a transplanted lung difficult. To overcome these problems in the best possible way, we decided to choose 2 primary end-points for our study: PaO2/FIO2 ratio and the incidence of PGD 41 at T24 hours. The limitation that PaO2/FIO2 ratio cannot be used on ECMO also influenced the comparison of PO2/FIO2 ratios at 24 hours, which might otherwise have been in favor of the EVLP group. With regard to the other primary end-point, PGD Z1 rate at T24 hours, the difference between the 2 groups was more pronounced (EVLP 5.9% vs standard 17.1%), although not significant. Although 8 patients in the

control group developed PGD 41 at T12 hours and 7 at T24 hours, the only 2 patients in the EVLP group falling into the PGD 41 category were the 2 patients who had an extremely complex intraoperative course and needed extracorporeal support for generalized hemodynamic instability. Neither patient showed signs of radiographic infiltrates consistent with pulmonary edema. In a review of 4400 patients, Prekker et al25 described a 35% PGD 41 rate at 24 hours and a 25% rate at 72 hours. This was combined with a 30-day mortality rate of 14% and 18% for PGD 2 and PGD 3 at 24 hours, respectively, and a 11% and 16% rate for PGD 2 and PGD 3 at 72 hours. Similar high rates of PGD 41 up to 25% have been reported by other authors.20 Given this history, it is remarkable how low the incidence of PGD has become in both groups. One explanation of the low PGD rates in our study lies in the selection of our patients. In contrast to retrospective studies, which looked at routine clinical patients, patients entering this prospective investigation represented a well-selected cohort, in which extremes, such as patients with idiopathic pulmonary arterial hypertension or other severe risk factors, were excluded for reasons of comparability. However, besides the influence of the selected patient cohort, it remains remarkable that the PGD 41 rates at T72 hours in both groups were o3%. For patients in the control group, this finding can be explained by the fast recovery that patients on prophylactically prolonged ECMO showed, which also resulted in zero 30day mortality in this group. To interpret these results correctly, one needs to take our institutional treatment standard into consideration. As explained in the Methods section, routine intraoperative circulatory support during lung Tx in our department is intraoperative central venoarterial ECMO. Volume substitution is liberally performed with packed red blood cells and fresh frozen plasma to maintain a high colloid osmotic pressure and hemoglobin levels. At the end of the implantation of the lungs, patients are decannulated, and the ECMO circuit is kept running on the table during chest closure. If there clear evidence at this point of insufficient or deteriorating lung function, venoarterial ECMO is transferred into the groin, and patients are transferred to the ICU

Slama et al.

EVLP in Standard Lung Transplantation

on running ECMO. The goal of this strategy is to prevent further deterioration of graft function, to interrupt the process of developing reperfusion injury and in this way also to avoid emergency ECMO implantation in the postoperative period. Optimal protective reperfusion is provided in this way to lungs with functional impairment at an early time point, which relieves the transplanted lungs from full cardiac output, enables protective low tidal volume ventilation, and avoids excessive use of catecholamines. As a consequence, fast recovery of an impaired allograft is made possible at the same time. The effectiveness of this concept is demonstrated by the short duration of postoperative ECMO support in 5 cases, which was only median 2 days, in combination with the 100% 30-day survival rate in this group. No patient in the EVLP group had ECMO prolongation for reasons of isolated lung dysfunction. Besides functional parameters, the exclusion of 4 lungs from the EVLP group for further Tx has to be discussed as well. Two lungs were excluded from the study for technical reasons, which made EVLP impossible. Two further lungs did not reach the pre-defined delta of PO2 4350 mm Hg during EVLP, which is currently considered to be the cutoff level for satisfying lung quality. This, in combination with signs of increasing fluid retention in the lungs, gave the indication to exclude the lungs from Tx. Histologic examination showed no pronounced structural or vascular pathologies. We are not able to judge how these lungs would have performed if they were directly transplanted; however, the possibility of relevant dysfunction is considerably high. Based on these results, one can speculate that EVLP might be able to identify a certain number of otherwise unrecognized donor allograft problems. However, to clearly answer this question, larger patient numbers are required. The main limitation of this study is its small patient sample size. Results from this single-center study have to be reproduced in other centers to demonstrate general applicability. For the first time to our knowledge, this study demonstrates in a clinical setting that EVLP applied in donor lungs that meet the standard acceptance criteria is at least equivalent to standard lung procurement. Although statistical significance for superiority of EVLP was not achieved in this study, results in the EVLP group were uniformly better, with 30-day mortality the only exception, as 1 death occurred in the EVLP group in a technically complex patient. This study suggests that EVLP can be safely applied to standard donor lungs, a finding that is important for future therapies that will aim to further improve donor lung quality. We are limited by the sample size, and it is conceivable that this difference might have become statistically significant in a better powered study. One additional finding of this study was the fact that prolonged storage time with EVLP did not negatively impact function. Until now, an empirically defined evaluation period of 4 hours for lungs on EVLP has been considered to be the standard.4 This 4-hour period was also used in the present study protocol. However, in several cases, the lungs were kept on the system for up to 5.5 hours for logistic reasons, with no negative impact on function. This experience, combined with experience in experimental settings in which perfusions were

9 performed safely up to 12 hours,2 indicates that even prolonged perfusion periods could safely be achieved. Such a prolonged perfusion period could form the basis for active interventions and treatment strategies during EVLP.26,27 In conclusion, this study provides evidence that EVLP can be safely applied for procurement of standard donor lungs. Functional results are comparable to results achieved with standard donor lung preservation techniques, and the clear tendency toward improved results with EVLP suggests that a statistically significant functional benefit of EVLP might be proven in a better powered study. Furthermore, EVLP acts as an evaluation tool, which allows clinicians to identify and to exclude lungs with functional impairment. Finally, EVLP can safely extend the total ischemic time. These findings provide a solid basis for future studies, which could add additional active interventional strategies to standard EVLP with the aim to further improve donor lung function. Thus, the focus of future developments should be prolonged perfusion and protocol modifications.

Disclosure statement This investigator-driven study was sponsored by XVIVO AB, Gothenburg, Sweden. The sponsor was not involved in the execution of the trial or in the data analysis. The authors have no additional disclosures to report.

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