T plantation has offered new therapeutical options for

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1 University of Wisconsin Versus Modified Euro Collins Solution for Lung Preservation Stephan W. Hirt, MD, Thorsten Wahlers, MD, Michael J. Jurmann, MD, Lutz Dammenhayn, MD, Josef Kemnitz, MD, PhD, Roland Rohde, PhD, and Axel Haverich, MD Division of Thoracic and Cardiovascular Surgery and Department of Pathology, Hannover Medical School, Hannover, Federal Republic of Germany n a canine model, the quality of lung preservation was assessed using pulmonary artery flush after prostacyclin administration with either modified EuroCollins solution or University of Wisconsin solution. Twelve combined heterotopic heart and orthotopic left lung allotransplantations were performed after 6 hours of cold ischemia. Myocardial preservation was achieved using St. Thomas Hospital solution. Donor organs were anastomosed parallel to the recipient s heart and right lung, and the superior vena cava inflow was directed into the transplanted heartleft lung block after ligation of the recipient s superior vena cava proximal to the caval anastomosis. Postoperatively, cardiorespiratory function was evaluated separately for donor and recipient organs at an inspired oxygen fraction of.4 for a maximum of 12 hours. Significantly improved oxygenation and lower pulmonary vascular resistance index of the donor lung was observed in the University of Wisconsin prostacyclin group, whereas pulmonary artery pressures showed no significant differences in between both groups. t is concluded that superior results in lung preservation can be achieved with pulmonary artery flush perfusion using University of Wisconsin solution and prostacyclin when compared with EuroCollins solution and prostacyclin. (Ann Thoruc Surg 1992;53:749) he clinical introduction of lung and heartlung trans T plantation has offered new therapeutical options for the increasing number of patients with endstage pulmonary and cardiopulmonary diseases [ld]. Particularly owing to the scarcity of donor organs and the problems encountered with donor transfer to the recipient s hospital, several methods for distant organ procurement have been developed in the past [2,681. Currently, pulmonary artery flush perfusion with EuroCollins solution (ECS) in combination with prostacyclin (PG,) is most frequently used for lung preservation [%12]. Acceptable results can be achieved clinically with ischemic times up to 4 hours [13]. Because the University of Wisconsin solution (UWS) has already been established successfully in kidney and liver transplantation [14, 151, we evaluated the applicability and quality of UWS for lung preservation after pretreatment with PG, in comparison with our current clinical standard as represented by ECS PG, [9, 161. Material and Methods Twelve mongrel dogs (mean weight, 18.7 f 5.3 kg) served as organ donors. After intramuscular administration of methylparaben (.5 mlkg) (Bayer AG, Leverkusen, Germany) and levomethadon (.3 ml/kg) (Hoechst AG, Frankfurt, Germany) and intravenous injection of sodium Resented at the Twentyseventh Annual Meeting of The Society of Thoracic Surgeons, San Francisco, CA, Feb 182, Address reprint requests to Dr Hirt, Division of Thoracic and Cardiovascular Surgery, Hannover Medical School, KonstantyGutschowStrage 8, D3 Hannover, Federal Republic of Germany. pentobarbital (.5 mug) (Rhone Merieux GmbH, Laupheim, Germany), orotracheal intubation was performed. The dogs were paralyzed with pancuronium bromide (4 mg initial dose) (Organon AG, OberschleiiJheim, Germany) and ventilated with 4% oxygen and 6% nitrous oxide using a tidal volume of 15 mlkg, a respiratory rate of 12 breathdmin, and a positive endexpiratory pressure of 5 cm H,O. General anesthesia was maintained by repeated intravenous application of fentanyl (.1 mg/h) (Janssen GmbH, Neuss, Germany) in combination with etomidate (4 mg/hour) (Janssen GmbH), and pancuronium bromide (2 mgh) was used for relaxation. An arterial line was placed in the left carotid artery and a thermodilution catheter was inserted in the pulmonary artery through the left internal jugular vein in all animals. The operative technique for donor and recipient operations was described previously by Wahlers and associates [9]. The donor animals were divided into two groups according to the method of pulmonary preservation: in group 1 (n = 6) pulmonary artery flush perfusion was performed with modified ECS (6 ml/kg), whereas in group 2 (n = 6) U WS (6 ml/kg) was used. The solution compositions were as follows: EuroCollins solution K,HPO, KH2p4 KCl NaHCO, MgSO4 Glucose 2.5 g/l 7.4 g/l 1.12 gn.84 g/l 1. gll 6.5 g/l 1992 by The Society of Thoracic Surgeons 34975/92/$3.5

2 Ann Thorac Surg 1992:53:749 HRTETAL 75 LUNG PRESERVATON USNG UW SOLUTON University of Wisconsin solution Hydroxyethyl starch 5. f3/l Lactobionic acid gl K,HP4 3.4 g/l WSO g/l Raffinose g/l Adenosine 1.34 g/l Allopurinol.14 g/l Glutathione.92 g/l nsulin 4 U/L Dexamethasone 16 mgl Penicillin G 2, UiL EuroCollins solution perfusion was performed by gravity. Owing to the higher viscosity of UWS a roller pump was used for perfusion in group 2. Prostacyclin (Wellcome, Grogburgwedel, Germany) was given intravenously over a 1minute period (2 ng. kg'. min') immediately before aortic crossclamping. Care was taken to achieve perfusion pressures according to the previously obtained individual pulmonary artery pressures. For cardioplegia St. Thomas Hospital solution (2 ml/kg, 4 C) was used in all donors. The organ block was immersed in cold ECS or UWS without further dissection and stored at 4 C for about 5 hours. The anesthetized recipient animals (mean weight, 27.6 f 4.9 kg) were prepared during the organ storage period as described above. Briefly, a left pneumonectomy was performed. Before the implantation, the right lung was removed from the heartlung block and the donor heart with the adjacent left lung was transplanted as described earlier [9, 161. Anastomoses were performed endtoside between the donor's and recipient's superior venae cavae, and the donor's descending aorta was sutured endtoside to the proximal part of the recipient's descending aorta. Ligation of the recipient's superior vena cava proximal to the anastomosis after 3 minutes of reperfusion provided a separation of the donor and recipient pulmonary circulation (Fig 1). The donor trachea was intubated with an endotracheal tube inserted through the second intercostal space and ventilated separately (oxygen 4%/nitrous oxide 6%; tidal volume, 1 mlikg; respiratory rate, 12/min; positive endexpiratory pressure, 5 cm H,O). The chest was closed temporarily. A pulmonary artery thermodilution catheter was placed through the left internal jugular vein and the donor's heart into the transplanted lung. An additional thermodilution catheter was inserted through the right femoral vein and the recipient's heart into the right pulmonary artery. This allowed measurement of cardiac output and pulmonary artery pressure in both circulations. Additional venous lines were placed in both left atria. Heart rate, arterial pressure, central venous pressure, pulmonary artery pressure (PAP), left atrial pressure (LAP), cardiac output, and left atrial blood gas analyses were obtained every hour until the postoperative course was terminated or the animal died. Calculation of cardiac index (C) and pulmonary vascular resistance index (PVR) were performed according to standard formulas. Data were expressed as mean values f standard devi Fig l. Heterotopic heart and orthotopic left lung transplantation. (AP = arterial pressure; BGA = left atrial blood gas analysis; CO = cardiac output; D = donor; LAP = left atrial pressure; PAP = pulmonay artey pressure; R = recipient; RAP = right atrial pressure.) ation. To exclude influences of baseline data on postoperative results, correlation analysis was performed using an analysis of covariance. Values of P less than.5 were considered significant. All animals received humane care in compliance with the "Principles of Laboratory Animal Care" formulated by the National Society for Medical Research and the "Guide for the Care and Use of Laboratory Animals" published by the National nstitutes of Health (NH publication No. 8523, revised 1985). Results Donor hemodynamic data showed no significant differences for PAP, C and PVR. n group 2, LAP was significantly lower (group 1, 9. f 3.4 mm Hg; group 2, mm Hg; p <.5) and the arterial oxygen tension (PO,) was slightly elevated (group 1, 19.3 f 1.2 mm Hg; group 2,222.6 f 22.8 mm Hg; p <.1) (Table 1). During harvesting, perfusion pressures did not exceed the native mean PAPS (group 1: perfusion pressure, 13.5 f 3.5 mm Hg; PAP, 15.7 f 4.8 mm Hg; group 2: perfusion pressure, 1. f 5.8 mm Hg; PAP, 14.3 f 2.4 mm Hg); there were no significant variations in perfusion pressure and donor PAP values between group 1 and group 2. The temperature of the perfusion solution (group 1, 4.2" 2.3"C; group 2, 4." 2.6"C), the perfusion time (group 1, 233 f 46 seconds; group 2, 211 f 34 seconds), the organ temperature after perfusion (group 1, 9.3" k 2.7"C; group 2, 11." f 3.9"C), and the total ischemia time of the donor organs (group 1, f 3.4 minutes; group 2, f

3 min' 76 HRTETAL LUNG PRESERVATON USNG UW SOLUTON Ann Thorac Surg 1992;53:7&9 '1 p<o.ol pe.5 pc.5 n.6. ECS 4 t Table 1. Donor Hemodynamic and Oxygenation Data" Variable ECS PG, UWS PG, PAP (mm Hg) 15.7 & f 2.4b LAP (mm Hg) 9. f f 2.' 3.89 f 1.7 PVR (dyn * s * cm5 * m2) f 1b PO, (mm Hg) 19 f f 23d C (L min' m') 3.25 f 1.43b a Data are shown as mean f standard deviation. P = not significant. P <.5. P <.1. C = cardiac index; ECS = EuroCollins solution; LAP = left atrial pressure; PAP = pulmonary artery pressure; PG, = prostacyclin; PO, = arterial oxygen tension; PWU = pulmonary vascular resistance index; UWS = University of Wisconsin solution. T T x j Fig 3. Postoperative donor cardiac index (C) (mean f standard deviation). (ECS = EuroCollins solution; n.s. = not significant; PG, = prostacyclin; UWS = University of Wisconsin solution.) 27.3 minutes) also showed no significant differences. The central venous pressure was adjusted in both venous systems at approximately 6 to 8 mm Hg during the entire postoperative course in both groups. n both groups no recipient animal died during the first 8 postoperative hours. Two dogs of each group died between 8 and 12 hours postoperatively. Causes of premature deaths of the animals were progressive cardiac failure with low output and dysrhythmias in all cases. mproved oxygenation of the donor lung after transplantation was observed in the UWS PG, group compared with the ECS PG, group throughout the entire postoperative period (Fig 2). During the first 5 postoperative hours PO, values were elevated in group 2 compared with group 1, but the differences were not significant. All PO, values obtained between 6 and 12 hours postoperatively showed a significant improvement in the U WS PG, group. n group 1 mean values of left atrial PO, decreased significantly during the postoperative course from 19 f 56 mm Hg at 2 hours to 123 f 34 mm Hg at 12 hours (p <.5) whereas the PO, values in group 2 were stable after transplantation (2 hours, 235 f 16 mm Hg; 12 hours, 215 f 47 mm Hg; not significant). Cardiac index was elevated in group 2 compared with group 1, and this difference was significant during the first 8 hours postoperatively (C at 2 hours: group 1, 1.6 f.29 L. min'. mp2; group 2, 2.34 f.8 L. min' m,; p <.1; at 5 hours: group 1,1.4 f.43 L min' mp2; group 2, 2.28 f 1.16 L. min'. m'..p <.5; and at 8 hours: group 1, 1.15 f.62 L. min' m'; group 2, 1.83 f.21 L 9 min'. m'. P <.5). Although C was stable in both groups during this time, in the later postoperative course C decreased in group 2 (p <.5). Despite this decrease, the C values in group 2 were still elevated compared with those in group 1, but the differences were not significant (C at 12 hours: group 1,1.5 &.23 L. min'. mp2; group 2,1.22 &.18 L * m', not significant) (Fig 3). Mean PAP ranged postoperatively between 14.2 * 7.3 mm Hg at 2 hours and mm Hg at 12 hours in group 1 and between 8.6 f 2.5 mm Hg at 2 hours and 11.5 f 4.7 mm Hg at 12 hours in group 2 (Fig 4). n both groups a slight, but not significant increase in PAP was found throughout the postoperative period. Comparing the corresponding postoperative PAP values of both groups, no significant differences were found at any time. Mean values of LAP of the donor hearts after transplantation ranged between 6.8 f 4. mm Hg at 2 hours and 8.3 f 3.9 mm Hg at 12 hours in group 1 compared with mm Hg at 2 hours and 6.8 f 3.9 mm Hg at 12 hours in E 24 E " 16 a n.8. n.8. p<o.o1 p<o.os 32 T 8. a ECS PQ12.. uws PO12 ECS PO12 _.. uws PQlp Fig 2. Postoperative donor left atrial oxygen tension (PO,) values (mean f standard deviation). (ECS = EuroCollins solution; n.s. = not significant; PG, = prostacyclin; UWS = University of Wisconsin solution.) Fig 4. Postoperative donor mean pulmonary artery pressure (PAP) (mean f standard deviation). ECS = EuroCollins solution; n.s. = not significant; PG, = prostacyclin; UWS = University of Wisconsin solution.)

4 Ann Thorac Surg 1992;53749 HRTETAL 7 LUNG PRESERVATON USNG UW SOLUTON 15 n.8. n.s. pc.5 n.8. ECS Fig 5. Postoperative donor left atrial pressure (LAP) (mean 2 standard deviation). (ECS = EuroCollins solution; n.s. = not significant; PG, = prostacyclin; UWS = University of Wisconsin solution.) group 2 (Fig 5). n both groups a slight but not significant increase of LAP was measured. Analysis of corresponding LAP values of both groups during the postoperative course revealed a statistically significant difference only at 8 hours postoperatively (LAP at 8 hours: group 1, 8.8 & 2.3 mm Hg; group 2, 5.3? 1.2 mm Hg; p <.5). Calculated PVR was elevated postoperatively in both groups and ranged between 75 & 313 dyn. s. cm. m2 at 2 hours and 947 & 732 dyn. s. cmp5. m2 at 12 hours in group 1 and between 196 & 132 dyn. s. cm5. m2 at 2 hours and 394? 4 dyn s m2 at 12 hours in group 2 (Fig 6). n both groups a significant increase in PVR was noted during the postoperative course (p <.5). Pulmonary vascular resistance index values of group 1 were elevated at all times postoperatively compared with the corresponding values of group 2. These differences reached statistical significance at 2,5, and 8 hours postoperatively. Between the two groups no significant differences were found in recipient data during the postoperative course comparing corresponding values of C, PAP, LAP, and PVR; there was a significant decrease in PO, values in both groups (p <.5). Comment First attempts at clinical lung transplantation failed early owing to problems caused by inadequate methods for N 2 E 8 E 9 12 f C r ECS PQ12.. uws t PG12 Fig 6. Postoperative donor pulmona y vascular resistance index (PVR) values (mean 2 standard deviation). (ECS = EuroCollins solution; n.s. = not significant; PG, = prostacyclin; UWS = University of Wisconsin solution.) lung preservation, aside from infectious complications and rejections [17]. As a consequence, different methods and techniques for lung procurement were investigated to improve preservation quality in clinical transplantation. nitially the lungs were harvested onsite and transplanted immediately without any attempts at preservation [17]. The limited donor availability for onsite organ procurement encouraged further development of different techniques for perfusion and preservation allowing distant organ procurement and longer ischemic times. Donor core cooling by extracorporeal circulation [8, 181 and singleflush perfusion of the pulmonary artery using either modified EuroCollins solution (2, 913] or cold blood [7] have been established. Satisfactory clinical results were achieved for mean ischemic times up to 4 hours. These methods were further improved by systemic application of prostaglandins to the donor immediately before harvesting. The resulting pulmonary vasodilation caused a better distribution of the crystalloid flush with improved early postoperative graft function [19, 21. Excellent experimental and clinical results with UWS in kidney and liver transplantation [14,15] encouraged us to compare this solution in combination with PG, with our current clinical standard (ECS PG,) for pulmonary preservation in a canine transplant model after 6 hours of cold ischemia. n our experimental setup, heterotopic heart and orthotopic singlelung transplantation was performed, as the use of extracorporeal circulation throughout the implantation can be omitted [9, 161. Another advantage of the model is based on the separation of donor and recipient circulation, because organ deterioration will not directly lead to the recipient s death, and reperfusion can be studied more extensively. For estimation of lung preservation quality, a 12hour postoperative followup period was chosen, as shorter observation times will underestimate the damage caused by reperfusion injury. Previous studies using UWS for pulmonary preservation are therefore limited, because only single measurements after 1 hour were obtained [21, 221. n both groups, a perfusion volume of 6 mlkg and perfusion pressures according to the native PAP were used, because investigations by Haverich and associates [ 11 demonstrated advantages with regard to homogeneous fluid distribution and uniform cooling. For quantification of lung preservation quality, left atrial PO,, PAP, and PVR were considered, whereas cardiac function was assessed using C and LAP. Analysis of lung water content was not performed, because others have already demonstrated its lesser sensitivity when compared with functional parameters [21]. The use of UWS PG, for pulmonary preservation resulted in excellent postoperative oxygenation of the transplanted lung as demonstrated by improved left atrial PO, throughout the entire postoperative course compared with the ECS PG, group. These differences were significant after 5 hours postoperatively owing to stable PO, values in the U WS PG, group, whereas in the ECS PG, group left atrial PO, decreased significantly. This

5 78 HRTETAL LUNG PRESERVATON USNG UW SOLUTON Ann Thorac Surg 1992;53:7&9 also demonstrated the necessity of an observation period of more than 6 hours for assessment of transplant lung function. Owing to the separation of both circulations with selective drainage of the superior vena caval return in the transplanted organs, cardiac output measured postoperatively in the donor circulation represents approximately one third of the total cardiac output. For this reason C and PVR can be compared only within the postoperative period. Using identical myocardial protection in both groups, the initially observed higher C in the UWS PG, group probably reflects better preservation of the pulmonary vascular bed resulting in a significantly lower PVR during the first 8 postoperative hours, because PAP and LAP values remained low and no significant changes were observed. n the later course C and PVR remained stable in the ECS PG, group without significant variations, whereas a decrease in C and increase in PVR in the UWS PG, group might reflect some degree of impairment despite maintenance of excellent oxygenation capacity. The basis for the improved results obtained with UWS is probably related to the structural components of the solution. n contrast to other crystalloid solutions UWS improves lung preservation in three critical aspects. Effective prevention of cell swelling and interstitial edema might be gained by the addition of three different impermeants. Especially for lactobionic acid it has been demonstrated that cell swelling is dramatically reduced during longterm perfusion with UWS [23]. Furthermore, membrane stabilization is achieved by dexamethasone in addition to the electrolyte composition [24]. Finally, antioxidants (glutathione and allopurinol) are included, which will reduce the generation of oxygen free radicals [&. The only disadvantage to be discussed with respect to lung preservation is the high potassium concentration. This can cause vasoconstriction by smooth muscle cells in the pulmonary artery bed. Therefore, UWS was applied after administration of PG,. Owing to the high viscosity of this solution, a roller pump was used for application. n conclusion, UWS in combination with PG, for lung preservation provides significantly improved postoperative oxygenation and lower PVR in lung transplantation compared with the current clinical standard as represented by ECS PG,. This was demonstrated in a canine heterotopic heart and orthotopic left lung transplant model after 6 hours of cold ischemia. The superior results obtained with UWS PG, in this experimental setting suggest the introduction of UWS into clinical lung transplantation and encourage further experimental studies on prolongation of the ischemic time. The statistical analysis was performed by R. Rohde, PhD, with the help of the Department of Biostatistics of the Hannover Medical School. Prostacyclin was supplied by H. Loebnau, Wellcome, Grogburgwedel, Germany, and the University of Wisconsin solution was kindly sumlied by R. Carter, Du Pont, UK. References 1. Cooper JD. Lung transplantationa new era. Ann Thorac Surg 1987;44: Jamieson SW, Stinson EB, Oyer PE, et al. Heartlung transplantation for irreversible pulmonary hypertension. Ann Thorac Surg 1984; Patterson GA, Cooper JD, Dark JH, Jones MT, Toronto Lung Transplant Group. Experimental and clinical double lung transplantation. J Thorac Cardiovasc Surg 1988;95: Scott J, Higgenbottam T, Hutter J, et al. Heartlung transplantation for cystic fibrosis. Lancet 1988;2: McGregor CGA, Dark JH, Hilton CJ, Freeman R, Conacher D, Coms PA. Early results of single lung transplantation in patients with endstage pulmonary fibrosis. J Thorac Cardiovasc Surg 1989; Ladowski JS, Kapelanski DP, Theodori MF, Stevenson WC, Hardesty RL, Gfith BP. Use of autoperfusion for distant procurement of heartlung allografts. Heart Transplant 1985; 3: Hakim M, Higgenbottam T, Bethune D, et al. Selection and procurement of combined heart and lung grafts for transplantation. J Thorac Cardiovasc Surg 1988;95:47&9. 8. Yacoub MH, Khaghani A, Banner N, Tajkarimi S, Fitzgerald M. Distant organ procurement for heart and lung transplantation. Transplant Proc 1989;21:254%5. 9. Wahlers T, Haverich A, Fieguth HG, Schafers HJ, Takayama T, Borst HG. Flush perfusion using EuroCollins solution vs cooling by means of extracorporeal circulation in heartlung preservation. J Heart Transplant 1986;5: Haverich A, Aziz S, Scott WC, Jamieson SW, Shumway NE. mproved lung preservation using EuroCollins solution for flush perfusion. Thorac Cardiovasc Surg 1986;34: Stuart RS, Monte S, Baumgartner WA, et al. Successful 4 hour hypothermic lung storage with EuroCollins solution: a simplified model assessing preservation. Heart Transplant 1984;3:34& Feeley TW, Mihm FG, Downing TP, et al. Hypothermic preservation of the heart and lungs with Collins solution: effect on cardiorespiratory function following heartlung allotransplantation in dogs. Ann Thorac Surg 1986;41: Haverich A, Wahlers T, Schafers HJ, et al. Distant organ procurement in clinical lung and heartlung transplantation. Eur J Cardiothorac Surg 199;4: Jamieson NV, Sundberg R, Lindel S. Preservation of the canine liver for 2448 hours using simple cold storage with University of Wisconsin solution. Transplantation 1988;46: Hoffmann B, Sollinger H, Kalyoglu M, Belzer FO. Use of UW solution for kidney transplantation. Transplantation 1988;46: Schafers J, Dammenhayn L, Wahlers T, Fieguth HG, Haverich A. Heterotopic heartunilateral left lung transplantation in dogs. Ann Thorac Surg 1987;44: Cooley DA, Bloodwell RD, Hallman GL, Nora JJ, Harrison GM, Leachman RD. Organ transplantation for advanced cardiopulmonary disease. Ann Thorac Surg 1969;8: Kontos GJ, Adachi H, Borkon AM, et al. A no flush, corecooling technique for successful cardiopulmonary preservation in heart lung transplantation. J Thorac Cardiovasc Surg 1987; Jurmann MJ, Dammenhayn L, Schafers HJ, Wahlers T, Fieguth HG, Haverich A. Prostacyclin as an additive to single crystalloid flush. mproved pulmonary preservation in heartlung transplantation. Transplant Proc 1987; Lehtola A, Harjula A, Heikkila L, et al. Singlelung allotrans

6 Ann Thorac Surg 1992;537&9 HRTETAL 79 LUNG PRESERVATON USNG UW SOLUTON plantation in pigs following donor pretreatment with intravenous prostaglandin E1. Scand J Thorac Cardiovasc Surg 1989;23: Naka Y, Shirakura R, Matsuda H, et al. Canine heartlung transplantation after 24 hours of hypothennic preservation. Eur J Cardiothorac Surg 199;449% Semik M, Moller F, Lange V, Bernhard A. A comparison of EuroCollins and UW1 solution for lung preservation using the parabiotic rat perfusion model. Presented to the European Society of Organ Transplantation, Barcelona, Spain, Nov 14, Southard JH, Belzer FO. Which components are important in the UWsolution? Presented to American Society of Transplant Surgeons, Chicago, L, May 31June 2, Belzer VO, Southard JH. Principles of solid organ preservation by cold storage. Transplantation 1988;45:6736. DSCUSSON DR J. KENT TRNKLE (San Antonio, TX): We have been very interested in this in the laboratory, comparing UWS with the standard flush and slush technique with EuroCollins solution. Our data are quite preliminary and incomplete because the two people doing this study had to take an unexpected sabbatical to Saudi Arabia. The critical factor in the UWS, however, may be the free radical scavenger, glutathione, and we are getting good results with glutathione alone added to the flush solution. wonder if you have looked at the individual components. This is a much easier and cheaper way to do it, to add a scavenger, rather than the whole solution. DR JOEL D. COOPER (St. Louis, MO): Dr Trinkle, how long are you preserving lungs for with that method? DR TRNKLE: Six hours. DR COOPER Okay, am going to comment on that after you answer him. The question is, do you need the whole concoction in the U WS or are there selective components of it that might suffice? DR HRT We have not evaluated special components because our endpoint is the clinical application of the solution. We therefore thought that the basic investigations had to be performed with the original fluid composition as commercially available. DR JOSEPH LoCCERO 111 (Chicago, L): Your work is extremely interesting to us because we are doing similar evaluations in an isolated, perfused, working lung model. We found that we can achieve superb protection of the parenchyma with excellent oxygenation after 17 hours of preservation with UWS. However, there is significant aerodynamic compromise, specifically, a decrease in compliance and a significant increase in resistance of the airway and work of breathing. Although this is an isolated lung preparation, we believe that there is a problem in protecting not only the large bronchus but also the small bronchus. wonder if you have any experience in the intact animal and, if not, do you plan to evaluate the aerodynamic changes? DR COOPER Have you done survival models? Do you have any airway problems or signs of increased airway resistance? DR HRT No, we did not observe any elevation of the inspiratory airway pressures in our experimental settings comparing UWS versus EuroCollins solution for lung preservation. DR COOPER Let me abuse the prerogative of the moderator to make a couple of comments. You really were testing both cardiac and pulmonary preservation, and as you indicated, there was a difference in the cardiac index of the two groups. That has always been the problem, believe, in looking at lung preservation by studying a model that simultaneously is dependent upon the preservation of the heart, because clearly interaction between the two is very important. DR HRT Combined transplantation of heterotopic heart and adjacent left lung allows a separation of the donor and recipient pulmonary circulation. n our opinion the advantage of this model is that a deterioration in the function of the transplanted lung will not directly lead to the death of the animal, as known from singlelung transplantation with ligation of the contralateral pulmonary artery. As a consequence, the effects of reperfusion damage probably can be studied more distinctively. DR COOPER think that there are a lot of very good studies, including this one, that demonstrate that one method may be better than another, but they are always limited to 6 hours. think 6 hours is not the problem. think there are many methods that have been clearly demonstrated to show excellent preservation of the lung in 6 hours. We too have tried UWS, and we did not find it as good as others, even the lowpotassium, homemade version. t seems to me that we have reached the stage where, if you want to demonstrate that you have a method of lung preservation that is better, 12 and 24 hours is the minimum standard, because there is a whole variety of methods that give superb function after 6 hours. How long have you gone? DR HRT This investigation represents our first large animal study on U WS for lung preservation with 6 hours of ischemia. For comparison with our currently used clinical standard as represented by EuroCollins flush and ischemic times of 4 to 6 hours in the clinical situation, we did not prolong the ischemic period beyond this time in the first step. We have recently started a singlelung transplant model with U WS for extended ischemia up to 24 hours, but so far the series are too small for statements.