Acellular Low-Potassium Dextran Preserves Pulmonary Function After 48 Hours of Ischemia

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1 Acellular Low-Potassium Dextran Preserves Pulmonary Function After 48 Hours of Ischemia Robert C. King, MD, Oliver A. R. Binns, MD, R. Chai Kanithanon, BA, Patrick E. Parrino, MD, T. Brett Reece, BA, James D. Maliszewskyj, RN, Kimberly S. Shockey, MS, Curtis G. Tribble, MD, and Irving L. Kron, MD Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia Health Sciences Center, Charlottesville, Virginia Background. We previously have shown that extracellular preservation solutions provide superior pulmonary protection after 18 hours of cold ischemia at 4 C in an isolated, whole-blood perfused, rabbit lung model. We also reported that the addition of 20% whole blood to a low-potassium dextran solution (BLPD) conferred no discernible advantage over low-potassium dextran (LPD) alone in this same model. Our current study was aimed at documenting the importance of blood in buffering extracellular preservation solutions during 24 to 48 hours of hypothermic ischemia. Methods. We studied three groups of lungs using an isolated, whole-blood perfused, ventilated, rabbit lung model. Lungs were flushed with Euro-Collins, LPD, or BLPD solution, and then were reperfused after 24, 36, or 48 hours of hypothermic storage at 4 C. Continuous measurements of pulmonary artery pressure, pulmonary vascular resistance, left atrial pressure, tidal volume, and dynamic airway compliance were obtained. Fresh, nonrecirculated venous blood was used to determine singlepass pulmonary venous-to-arterial O 2 gradients. Results. The 24-hour Euro-Collins group could not be completed because of immediate reperfusion failure. The 36-hour LPD group oxygenated significantly better than the 36-hour BLPD group ( versus mm Hg, respectively; p 0.015). The 48-hour LPD group also experienced significant improvements in oxygenation when compared with the 48-hour BLPD group (pulmonary venous-arterial O 2 difference of versus mm Hg, respectively; p 0.012). The 48-hour LPD group also displayed significant improvements in pulmonary artery pressure ( versus mm Hg, respectively; p 0.031) and pulmonary vascular resistance (39,737 1,291 versus 67,594 9,467 dynes s cm 5, respectively; p 0.027) when compared with the 48-hour BLPD group. There were no significant differences between the three LPD groups. Conclusions. Extracellular solutions provide improved pulmonary preservation in an isolated rabbit lung model after 48 hours of cold ischemia. The addition of blood to extracellular preservation solutions diminishes pulmonary function when combined with ischemic periods of 36 to 48 hours. (Ann Thorac Surg 1997;64: ) 1997 by The Society of Thoracic Surgeons Lung transplantation has plateaued as a therapeutic modality for end-stage lung disease during the past several years. A shortage of suitable lung donors has developed as a result of the limited number of suitable multiorgan donors and the frailty of the lung to both pretransplantation and ischemia-reperfusion injury. Inability to extend tolerable ischemic times, as well as to provide adequate preservation for marginal grafts, has limited the pulmonary donor pool with respect to solid organ donation. The development of solutions specific for pulmonary endothelial and pneumocyte functional preservation has been of growing interest during the past decade [1]. Traditionally, single-flush perfusion of pulmonary grafts with a modified Euro-Collins (EC) solution in Presented at the Thirty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Feb 3 5, Address reprint requests to Dr Kron, Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia Health Sciences Center, Box 310, Charlottesville, VA combination with a prostaglandin infusion has been the accepted standard for pulmonary preservation [2]. This technique has allowed for acceptable ischemic periods of 6 to 12 hours before lung implantation in the clinical setting. Despite this practice, lung reperfusion injury is still a significant and occasionally costly outcome for approximately 10% to 20% of all transplant recipients [3]. Alternatives to this standard approach have led several investigators to develop solutions aimed at preserving the pulmonary vasculature s endothelial response to ischemia-reperfusion through the use of extracellular or low-potassium solutions. Several studies have documented improved pulmonary tolerance to ischemia-reperfusion injury with the use of extracellular preservation solutions in multiple animal models [4 8]. These solutions have a low potassium concentration and generally use a colloid plasma substitute to decrease endothelial binding of circulating blood elements. Dextran, hydroxyethyl starch, and polygelin all have been used successfully as alternative solu by The Society of Thoracic Surgeons /97/$17.00 Published by Elsevier Science Inc PII S (97)00595-X

2 796 KING ET AL Ann Thorac Surg BLOOD-BASED VERSUS DEXTRAN PRESERVATION 1997;64: Fig 1. Average of raw data for pulmonary artery pressures collected at 15-second intervals during 30 minutes of pulmonary reperfusion for the 36- and 48-hour low-potassium dextran (LPD) and low-potassium dextran with whole blood (BLPD) groups. tions for lung preservation. The addition of blood to improve cellular buffering and maintain metabolic equilibrium also has been well documented during ischemic periods as long as 18 hours [9 11]. The purpose of this study was to investigate the limits of ischemic preservation in an isolated rabbit lung model. We compared the effectiveness of an intracellular preservation solution (EC) with an extracellular solution (low-potassium dextran [LPD]) with or without the addition of 20% autologous, whole blood (BLPD) after 24, 36, and 48 hours of hypothermic ischemia. We hypothesized that the addition of whole blood to a low-potassium dextran preservation solution would extend the tolerable ischemic period before lung reperfusion. Material and Methods Lung-Heart Block Harvesting Using the following experimental model previously described by our laboratory [12], 49 adult New Zealand white rabbits of either sex (3.0 to 3.5 kg) were assigned randomly to seven experimental groups. Each rabbit was anesthetized with intramuscular ketamine (50 mg/kg) and xylazine (5 mg/kg). Tracheal intubation was performed through a tracheostomy and followed by paralysis with intravenous metocurine (0.2 mg/kg). Mechanical ventilation was instituted (Ventilator RSP1002; Kent Scientific Corporation, Litchfield, CT) using room air with a tidal volume of 12 ml/kg and a rate of 20 breaths/min. A median sternotomy and thymectomy then were performed. The superior and inferior venae cavae were encircled loosely with ligatures and the pericardium was opened. Both the pulmonary artery (PA) and the aorta were dissected free and similarly encircled. A pursestring suture then was placed in the free wall of the right ventricle and the rabbit was heparinized intravenously (500 U/kg). After the injection of 30 g of prostaglandin E 1 (Alprostadil; Upjohn Company, Kalamazoo, MI) directly into the PA, the venae cavae were ligated, initiating the 18-hour ischemic period. The PA then was cannulated through a right ventriculotomy in the center of the pursestring suture and both the right ventricle and PA ligatures were tied around the cannula. After venting the left ventricle through a left ventriculotomy and ligating the aorta, 50 ml/kg of the preservation solution to be evaluated according to the protocol was infused into the PA from a height of 30 cm and at a temperature of 4 C. Topical cooling was achieved with cold saline slush. During PA flush, the left atrium was cannulated through the left ventriculotomy and a second pursestring suture was tied around the cannula. A second catheter was placed in the left atrium to transduce left atrial pressures directly. After the PA flush, the inflow and outflow cannulas were clamped. Care was taken to leave the pleurae intact until the completion of the flush to avoid parenchymal injury. The lungs were stored inflated by clamping the tracheal tube at end-inspiration. The lung-heart block then was excised, immersed in cold 0.9% saline solution, and stored at 4 C for 18 hours. All experimental protocols were reviewed and approved by an institutional animal use committee. 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 Institutes of Health (NIH publication 86-23, revised 1985). Assessment of Lung Function After 18 hours of storage at 4 C, the lung-heart block was suspended by a force transducer in a warm, humidified tissue chamber. Ventilation was reestablished with a 95% O 2 /5% CO 2 gas mixture at a tidal volume of 12 ml/kg and a respiratory rate of 20 breaths/min. The lungs were reperfused with homologous, fresh, whole, venous blood from a main reservoir. A second venous blood reservoir was used to determine single-pass oxygenation at 10, 20, and 30 minutes after the initiation of reperfusion. Blood was harvested from a single rabbit for each experiment. The inflow and outflow cannulas then were connected to the blood-primed perfusion circuit, with care taken to avoid the introduction of air. The perfusion circuit was designed to recirculate 150 ml of warmed blood through a 270- m blood filter (no. 2C7600; Baxter, Deerfield, IL) using a roller pump (no ; Cole Palmer Instrument Company, Chicago, IL) at a rate of 60 ml/min (Fig 1). A 270- m blood filter was chosen so as not to affect leukocyte or platelet counts. Continuous recording of PA pressure, left atrial pressure, lung weight, airway flow, and airway pressure was facilitated by the use of a dynamic data acquisition program (Workbench PC; Strawberry Tree, Inc, Sunnydale, CA) run on a personal computer (no. 470A; Compaq Prolinea, Houston, TX). This program automatically calculated and displayed pulmonary vascular resistance, tidal volume, and dynamic airway compliance. The left atrial pressure was maintained within the physiologic range (4 to 8 mm Hg) by adjusting the height of a small outflow reservoir in the circuit. Pulmonary venous blood samples were collected for blood gas analysis (Corning 178 ph/blood Gas Analyser; Ciba Corning Diagnostics Corp, Medfield, MA) at 10, 20, and 30 minutes after the start of reperfusion. At

3 Ann Thorac Surg KING ET AL 1997;64: BLOOD-BASED VERSUS DEXTRAN PRESERVATION 797 each sampling interval, inflow from the main reservoir was interrupted and the circuit was filled with venous blood from the second inflow reservoir. Thirty milliliters of venous blood was passed through the pulmonary vasculature at each interval to ensure accurate measurement of pulmonary venous oxygen content. Oxygen contact with exposed blood surfaces inside the reservoir containers was minimized by the continuous infusion of 100% nitrogen. After 30 minutes of reperfusion, specimens of lung tissue were acquired for weight analysis. Wet-to-dry ratios were calculated after passive desiccation at room temperature to a stable dry weight. Experimental Protocol All lungs were stored inflated at 4 C for 18 hours after the injection of 30 g of prostaglandin E 1 and single-flush preservation with 50 ml/kg of solution. Seven experimental groups were defined on the basis of the preservation solution they were assigned randomly to receive (Table 1). Group 1 (n 7) received EC solution and their lung-heart blocks were stored for 24 hours at 4 C. Groups 2 through 4 (n 7 in each group) received LPD solution and their lung-heart blocks were stored for 24, 36, and 48 hours, respectively. Groups 5 through 7 (n 7 in each group) received a flush solution composed of LPD solution with the addition of 20% autologous, heparinized, whole, venous blood (BLPD) and their lung-heart blocks were stored for 24, 36, and 48 hours, respectively. All lungs were reperfused at a physiologic flow rate of 60 ml/min for 30 minutes. Data were recorded every 15 seconds and analyzed at the end of the 30-minute reperfusion period. Oxygenation data were obtained and analyzed at 10-minute intervals. All values were expressed as the mean the standard error of the mean. Statistical analysis was performed by analysis of variance to compare the experimental groups. Differences were considered to be statistically significant if the p value was less than Table 1. Preservation Solution Composition Component Solution EC LPD BLPD Na (mmol/l) K (mmol/l) Cl (mmol/l) HCO 3 (mmol/l) HPO 2 4 (mmol/l) H 2 PO 4 (mmol/l) Mg 2 (mmol/l) Ca 2 (mg/dl) Lactate (mmol/l) Dextran (g/l) Dextrose (g/l) Donor blood (%) ph (4 C) EC Euro-Collins; LPD low-potassium dextran; BLPD lowpotassium dextran with 20% autologous whole blood. Fig 2. Pulmonary venous-to-arterial oxygen gradients as determined by single-pass venous blood oxygenation at 10, 20, and 30 minutes of reperfusion. (LPD low-potassium dextran; BLPD low-potassium dextran with whole blood.) Results Pulmonary function was assessed during reperfusion using the following parameters: pulmonary artery pressure (PAP), pulmonary vascular resistance, dynamic lung compliance, and oxygenation capacity (V-A O 2 ). In our model, we defined oxygenation capacity as the ability of the lungs to oxygenate venous blood during a single pass from the pulmonary artery to the left atrium. It is reported as a venous-to-arterial gradient to normalize for gradual decreases that occur in the venous blood oxygen tension during the course of the experiment. At the end of the 30-minute reperfusion period, tissue samples were obtained for determining wet-to-dry weight ratios after 2 weeks of passive desiccation. Lungs preserved with EC (n 7) were unable to be reperfused successfully after 24 hours of storage at 4 C. The following parameters were used to determine graft failure on reperfusion: a PAP of 100 mm Hg or greater, a V-A O 2 gradient of 10 mm Hg or less, and direct visualization of edema fluid accumulation in the endotracheal tube. All but one of our seven EC-preserved specimens met these criteria. A seventh EC-preserved specimen was able to tolerate the 30-minute reperfusion period, but displayed a final PAP of mm Hg, a V-A O 2 of 13.4 mm Hg, and obvious edema fluid accumulation in the endotracheal tube. No statistical analysis could be performed on these limited data. The results for our EC-preserved lungs after 18 hours of hypothermic ischemia have been published previously [10]. Hemodynamics The actual data for PAP as recorded and averaged for the 30-minute reperfusion periods are presented in Figure 1. The only statistically significant difference in measured pulmonary hemodynamics occurred with the BLPDpreserved lungs after 30 minutes of reperfusion performed after 48 hours of hypothermic ischemia. These lungs had significantly higher PAP ( mm Hg) when compared with lungs preserved with LPD for 48 hours ( mm Hg; p 0.031) (Fig 2). Likewise, lungs preserved with BLPD for 48 hours displayed a significant elevation in pulmonary vascular resistance

4 798 KING ET AL Ann Thorac Surg BLOOD-BASED VERSUS DEXTRAN PRESERVATION 1997;64: Table 2. Results After 30 Minutes of Pulmonary Reperfusion Group PAP (mm Hg) PVR (dynes s cm 5 ) CPL (ml/mm Hg) V-A O 2 (mm Hg) Wet-to-Dry Weight Ratio LPD 24 hours ,254 2, BLPD 24 hours ,960 4, LPD 36 hours ,382 1, BLPD 36 hours ,221 4, a LPD 48 hours ,737 1, BLPD 48 hours b 67,594 9,467 c d a p versus 36-hour LPD; b p versus 48-hour LPD; c p versus 48-hour LPD; d p versus 48-hour LPD. PAP pulmonary artery pressure; PVR pulmonary vascular resistance; CPL dynamic airway compliance; V-A O 2 pulmonary venous-to-arterial oxygen gradient; LPD low-potassium dextran; BLPD low-potassium dextran with whole blood. (67,594 9,467 dynes s cm 5 ) when compared with lungs stored with LPD for 48 hours (39,737 1,291 dynes s cm 5 ; p 0.027). There were no other statistically significant differences between the BLPD-preserved and LPD-preserved lungs with regard to pulmonary hemodynamics (Table 2). Pulmonary Venous-to-Arterial O 2 Gradient There were statistically significant decreases in the single-pass V-A O 2 gradient after 30 minutes of reperfusion in both the 36- and 48-hour BLPD groups when compared with their respective LPD-preserved counterparts (Fig 3). The V-A O 2 gradient was mm Hg for the 36-hour BLPD group compared with mm Hg for the 36-hour LPD group (p 0.015). The V-A O 2 gradient for the 48-hour BLPD group was mm Hg compared with mm Hg for the 48-hour LPD group (p 0.012). These groups also experienced similar significant differences at the 20-minute V-A O 2 determination (Fig 4). There were no statistical differences between BLPD and LPD preservation after 24 hours of hypothermic storage with regard to single-pass oxygenation. Compliance There were no statistically significant differences in dynamic airway compliance between any of the groups. There was a slight decrease in measured dynamic airway compliance for the 48-hour BLPD group; however, these differences were not significant when compared with any other group. Wet-to-Dry Weight Ratio There also were no statistically significant differences in the formation of pulmonary edema as measured by wet-to-dry weight ratios. Likewise, there was an increase in the wet-to-dry weight ratio for the 48-hour BLPD group, but again this difference was not significant when compared with any other group. There were no statistically significant differences between the three LPD groups after 24, 36, or 48 hours of ischemic storage at 4 C in any of the measured parameters (see Table 2). Results for our LPD-preserved lungs after 18 hours of hypothermic storage also have been published previously [10]. Comment The use of intracellular solutions for pulmonary preservation has gained widespread clinical acceptance [2]. These solutions originally were developed to optimize solid organ preservation. The high potassium concentrations in both EC and University of Wisconsin solution were aimed at decreasing the metabolic demands neces- Fig 3. Comparison of pulmonary artery pressures at 30 minutes after 24, 36, and 48 hours of hypothermic ischemia for both the lowpotassium dextran (LPD) and low-potassium dextran with whole blood (BLPD) groups. Fig 4. Comparison of pulmonary venous-to-arterial oxygen gradients at 30 minutes after 24, 36, and 48 hours of hypothermic ischemia for both the low-potassium dextran (LPD) and low-potassium dextran with whole blood (BLPD) groups.

5 Ann Thorac Surg KING ET AL 1997;64: BLOOD-BASED VERSUS DEXTRAN PRESERVATION 799 sary to maintain cellular electrolyte gradients, thereby preserving adenosine triphosphate stores during preservation [13]. However, studies have documented that the high potassium concentrations in pulmonary flush solutions actually may be detrimental to organ function after periods of ischemia [14]. High-potassium preservation contributes to elevated hydrostatic pressures at the pulmonary capillary bed secondary to induced vasoconstriction. Potassium also has been shown to be detrimental to the preservation of the endothelial cell and pneumocyte [15, 16]. Clinically, these problems have been overcome through the administration of a prostaglandin infusion both before and during the flush of the donor allograft. The efficacy of this practice has been demonstrated in a canine transplantation model that displayed improved pulmonary function when compared with lungs preserved with an LPD solution after 18 hours of ischemia [17]. We have been unable to duplicate this success in our laboratory using an isolated, whole-blood perfused, rabbit lung model. In fact, we have shown that lungs preserved with EC solution and prostaglandin injection displayed significant elevations in PAP and a decreased ability to oxygenate after 18 hours of hypothermic ischemia when compared with lungs preserved with a lowpotassium solution [11]. We also have shown that pulmonary function in the face of high-flow reperfusion is preserved with low-potassium solutions [18, 19]. Our most recent studies have shown no significant difference in pulmonary hemodynamics or oxygenation when lungs are flushed with either EC solution and prostaglandin or LPD followed by immediate reperfusion. The exact cellular mechanism responsible for this phenomenon in the rabbit remains to be elucidated. However, evidence exists that high-potassium solutions may contribute to decreased activity of Ca -adenosine triphosphatase in the pulmonary endothelium [20]. This phenomenon could lead to altered intracellular calcium distribution and possible changes in the level of activity of nitric oxide synthase. Whether these differences are due solely to species-specific differences has not been investigated fully. Further studies are warranted in large animal models and possibly prospective, randomized, clinical trials. The addition of dextran or other impermeant colloid substitutes has been shown to be of benefit during prolonged hypothermic pulmonary storage in multiple animal models [4 8]. Equivalent results have been achieved with either dextran or hydroxyethyl starch after 30 hours of hypothermic ischemia in a canine model [21]. Both these solutions have been documented to provide superior pulmonary preservation when compared with EC-preserved lungs. These findings have been reported after prolonged periods of hypothermic ischemia in canine and rodent models [11, 12, 21]. The relevant mechanisms in this setting include decreased endothelial cellular edema resulting from increased intravascular oncotic pressure and nonspecific inhibition of both leukocyte and platelet endothelial adhesion. Additional studies have documented the importance of a low potassium concentration in the dextran flushing solution when compared with dextran solutions with high potassium concentrations [7, 21]. The addition of red blood cells to colloid preservation solutions is thought to minimize ischemia-reperfusion injury to the lung by providing a physiologic buffering system [22, 23]. The addition of erythrocytes also supplements colloid oncotic pressure in an attempt to decrease pulmonary edema formation. The addition of whole blood to a preservation solution may confound this picture by introducing additional leukocytes and platelets during the ischemic phase. Alternatively, whole blood may improve ischemic preservation by providing additional metabolic substrates for the vascular endothelium [24]. The addition of washed bovine red blood cells to a Krebs-Henseleit buffer conferred improved pulmonary preservation after harvest of a rodent lung-heart block and immediate reperfusion [9]. The addition of blood to a low-potassium solution, followed by 6 hours of ischemic preservation in a rat model, showed improvements in pulmonary vascular resistance and decreased edema formation [11]. Our experience has shown that the addition of 20% whole blood to a low-potassium preservation solution conferred no additional statistically significant advantage in pulmonary function when compared with LPD alone [12]. Our current study did not show a significant difference in pulmonary function after 24 hours of ischemic preservation with either LPD or BLPD solutions. After 36 hours of preservation, the lung s ability to oxygenate began to deteriorate significantly. This was followed by hemodynamic decompensation and a trend toward increased edema formation at 48 hours with BLPD preservation. These findings could be explained by activation of both platelets and leukocytes present in the added whole blood. In addition, the integrity of erythrocyte function and structure probably is altered tremendously after 48 hours of hypothermic storage without the addition of cellular preservative solutions. Further investigations into the cellular pathology responsible for this derangement currently are under way. We compared these results with those of our previous studies of LPD preservation and 18 hours of hypothermic ischemia. There were no significant differences in pulmonary function between similarly preserved lungs after 48 hours of hypothermic ischemia. There was a slight decrease in single-pass oxygenation after 48 hours of hypothermic ischemia; however, this was not statistically significant when compared with the 24-hour LPD group. In summary, this study demonstrates adequate preservation of pulmonary function in an isolated, wholeblood perfused, rabbit lung model after 48 hours of hypothermic preservation with an LPD solution. The addition of whole blood to an LPD solution actually decreased the lung s ability to oxygenate after 36 hours of ischemia. Subsequent deterioration of pulmonary hemodynamics occurred after 48 hours of ischemic preservation with BLPD.

6 800 KING ET AL Ann Thorac Surg BLOOD-BASED VERSUS DEXTRAN PRESERVATION 1997;64: This work was supported by the National Institutes of Health under R01 grant HL and National Research Service Award fellowship F32HL The technical advice and support of Anthony J. Herring is acknowledged. References 1. Novick RJ, Gehman KE, Ali IS, Lee J. Lung preservation: the importance of endothelial and alveolar type II cell integrity. Ann Thorac Surg 1996;62: Sundaresan RS, Cooper JD. Lung transplantation. In: Sabiston DC, ed. Textbook of surgery: the biologic basis of modern surgical practice, 15th ed. Philadelphia: WB Saunders, 1997: Date H, Triantafillou AN, Trulock EP, Pohl MS, Cooper JD, Patterson GA. Inhaled nitric oxide reduces human allograft dysfunction. J Thorac Cardiovasc Surg 1996;111: Hiromi W, Tatsuo F, Takayuki N, et al. ET-Kyoto solution for 48-hour canine lung preservation. Ann Thorac Surg 1996;61: Sundaresan S, Lima O, Date H, et al. Lung preservation with low-potassium dextran flush in a primate bilateral transplant model. Ann Thorac Surg 1993;56: Moriyasu K, McKeown PP, Novitzky D, Snow TR. Preservation of competent rabbit lung function after 30 hours of storage with a low-potassium dextran solution. J Heart Lung Transplant 1995;14: Keshavjee SH, Yamazaki F, Yokomise H, et al. The role of dextran 40 and potassium in extended hypothermic lung preservation for transplantation. J Thorac Cardiovasc Surg 1992;103: Steen S, Kimbald PO, Sjöberg T, Lindberg L, Ingemansson R, Massa G. Safe lung preservation for twenty-four hours with Perfadex. Ann Thorac Surg 1994;57: Fukuse T, Albes JM, Takahashi Y, Brandes H, Hausen B, Schäfers HJ. Influence of red blood cells on lung function in an ex vivo rat heart-lung model. J Surg Res 1995;59: Xiong L, Mazmanian M, Chapelier AR, et al. Lung preservation with Euro-Collins, University of Wisconsin, Wallwork, and low-potassium-dextran solutions. Ann Thorac Surg 1994;58: Binns OA, DeLima NF, Buchanan SF, et al. Both blood and crystalloid-based extracellular solutions are superior to intracellular solutions for lung preservation. J Thorac Cardiovasc Surg 1996;112: Buchanan SA, Mauney MC, DeLima NF, et al. Enhanced isolated lung function after ischemia using anti-icam antibody. J Thorac Cardiovasc Surg 1996;111: Collins GM. Flush preservation. In: Pegg DE, Jacobsen IA, Halasz NA, eds. Organ preservation: basic and applied aspects. Lancaster, England: MTP Press, 1982: Sasaki S, McCully JD, Alessandrini F, LoCicero J. Impact of initial flush potassium concentration on the adequacy of lung preservation. J Thorac Cardiovasc Surg 1995;109: Chan BBK, Kron IL, Flanagan TL, Kern JA, Hobson CE, Tribble CG. Impairment of vascular endothelial function by high-potassium storage solutions. Ann Thorac Surg 1993;55: Hachida M, Hoon DSB, Morton DL. A comparison of solutions for lung preservation using pulmonary alveolar type II cell viability. Ann Thorac Surg 1988;45: Puskas JD, Cardoso PFG, Mayer E, Shi S, Slutsky AS, Patterson GA. Equivalent eighteen-hour lung preservation with low-potassium dextran or Euro-Collins solution after prostaglandin E 1 infusion. J Thorac Cardiovasc Surg 1992; 104: DeLima NF, Binns OAR, Buchanan SA, et al. Low-potassium solution for lung preservation in the setting of high-flow reperfusion. Ann Thorac Surg 1996;61: DeLima NF, Binns OAR, Buchanan SA, et al. Euro-Collins solution exacerbates lung injury in the setting of high-flow reperfusion. J Thorac Cardiovasc Surg 1996;112: Labow RS, Meek E, Waghray G. Use of the University of Wisconsin solution for the preservation of cell organelle activities in rat heart and lungs. J Heart Lung Transplant 1995;14: Wada H, Liu H, Inui K, Hirata T, Fukuse T, Hitomi S. Newly developed preservation solution for the lung: 30-hour preservation with new ET-Kyoto solution. Transplant Proc 1996; 28: Toth KM, Clifford DP, Berger EM, White CW, Repine JE. Intact human erythrocytes prevent peroxide-mediated damage to isolated perfused rat lungs and cultured bovine pulmonary artery endothelial cells. J Clin Invest 1984;74: Van Asbeck BS, Hoidal J, Vercellotti GM, Schwartz BA, Moldow CF, Jacob HS. Protection against lethal hyperoxia by tracheal insufflation of erythrocytes: role of red cell glutathione. Science 1985;227: Modry DL, Walpoth BW, Cohen RG, et al. Heart-lung preservation in the dog followed by lung transplantation. J Heart Transplant 1983;2: DISCUSSION DR JAMES K. KIRKLIN (Birmingham, AL): Did you examine University of Wisconsin solution in any of your pilot studies? DR KING: No, we have not done that. We believe that the high potassium concentration of intracellular preservation solutions is the single most injurious component to the pulmonary vasculature. We did not use University of Wisconsin solution because it has a high potassium concentration as well.