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Reliable eighteen-hour lung preservation at 4° and 10° C by pulmonary artery flush after high-dose prostaglandin E1 administration
Reliable eighteen-hour lung preservation at 4° and 10° C by pulmonary artery flush after high-dose prostaglandin E 1 administration Pulmonary preservation is improved by hypothermia, but the optimal preservation temperature is not known. The effects of two different preservation temperatures, 4° and 10° C, on lung function were studied in a canine left lung aUograft survival model aUowing selective perfusion of either lung. Mter donor treatment with high-dose prostaglandin E., (25 ILg/kg~ lungs were flushed with modified Euro-CoUins solution (50 m1/kg) and stored in Euro-CoUins solution for 18 hours at 4° C in group I (n = 8) and 10° C in group II (n = 6). Pulmonary gas exchange and hemodynamics were compared on the day of transplantation (day 0) and 3 days later (day 3). Rapid, high-flow, low-pressure flush was achieved uniformly in both groups (flush time: group I, 35.1 ± 2.4 seconds; group II, 35.3 ± 3.0 seconds; p = 0.96; flush pressure: group I, 9.8 ± 0.7 mm Hg; group II, 10.1 ± 1.1 mm Hg; p = 0.8~ Transplanted lungs provided similar exceUent oxygenation in both groups on day 0 (arterial oxygen tension, group I, 451 ± 82 mm Hg; group II, 497 ± 37 mm Hg; p = 0.61; inspired oxygen fraction = 1.0) and day 3 (arterial oxygen tension, group 1,551 ± 57 mm Hg; group II, 587 ± 19 mm Hg; p = 0.55~ with a statisticaUy significant improvement from day 0 to day 3 in both groups (group I, p = 0.034; group II, p = 0.038~ There was no difference in arterial carbon dioxide tension, base excess, cardiac output, blood pressure or pulmonary artery pressure between the two groups. We conclude that a large bolus of prostaglandin E 1 into the pulmonary artery produces a high-flow, low-pressure flush with modified Euro-CoUins solution; with this technique, equivalent, reliable 18-hour lung preservation can be achieved at 4° and 10° C flush and storage temperatures. (J THORAe CARDIOVASC SURG 1992;103:1136-42) Eckhard Mayer, MD, * John D. Puskas, MD, Paulo F. G. Cardoso, MD, Shiquing Shi, MD, Arthur S. Slutsky, MD, and G. Alexander Patterson, MD, FRCSC, Toronto, Ontario, Canada
Lng transplantation has been used successfully in the treatment of selected patients with end-stage pulmonary disease. 1-4 Broader application of this procedure is severeFrom the Division of Thoracic Surgery, Department of Surgery, University of Toronto, Toronto General Hospital, Toronto, Ontario, Canada. Supported by Medical Research Council grant 10142. Received for publication Sept. 14, 1990. Accepted for publication March 5, 1991. Address for reprints: G. A. Patterson, MD, One Barnes Hospital Plaza, Suite 3108 Queeny Tower, St. Louis, MO 63110. *Supported by the Department of Cardiothoracic and Vascular Surgery, Johannes Gutenberg-University Clinics, Mainz, FRG, and the Deutsche Forschungsgemeinschaft; present address: Department of Cardiothoracic and Vascular Surgery, Johannes Gutenberg-University Clinics, D-6500 Mainz, FRG. 12/1/30719
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ly limited by the current shortage of suitable donor lungs. Although lung preservation has been studied extensively for almost 30 years' a reliable clinical technique of lung preservation beyond 6 hours has not been achieved. Better methods oflung preservation would allow an extension of the safe ischemic time and therefore increase the quantity and quality of available lung grafts and facilitate an adequate matching of donor organs and recipients. On the basis of results in solid organ transplantation.? a lung preservation temperature of 4 0 C isconsidered (but not proved) to provide optimal graft function, presumably by slowing down cellular enzyme activity and metabolism. However, there are known detrimental effects of hypothermia on a number of cellular mechanisms, including membrane permeability.?'? glucose use.l'' calcium sequestration, 1I and cellular osmotic homeostasis.?" Wang and colleagues'? have used an ex vivo rabbit lung
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model and found that 10° C storage with simple immersion provided better lung preservation than the universally used 4 ° C. Thus the optimal preservation temperature remains to be investigated in an in vivo survival model with the use of a pulmonary flush preservation technique. Most clinical lung and heart-lung transplantation programs have preserved donor lungs by means of vasosodilator prostanoid pretreatment followed by pulmonary artery (PA) flush with cold (4° C) modified crystalloid solutions.v 13, 14 However, there is no agreement as to the vasodilator or the dose required. Furthermore, it is not known whether P A flush and subsequent preservation could be enhanced by increased pulmonary vasodilation with a higher dose of vasodilator prostanoid. The present study was designed to compare the effects on lung function of 18-hour preservation by P A flush and storage at 4° and 10° C in a canine left lung allotransplantation model after donor pretreatment with a large bolus dose of prostaglandin EI (PGE 1) .
Material and methods Pairs of weight-matched mongrel dogs underwent left lung allotransplantation. Donor lungs were randomly assigned in a blinded fashion to one of two study groups. The flush and storage temperature was 4° C in group I (n = 8) and 10° C in group II (n = 6). Donor operation. After pretreatment with atropine (0.5 mg intravenously) and cefazolin (I gm intravenously) and sedation with meperidine (50 mg intravenously) and acepromazine (I mg intravenously), the donor dogs were anesthetized with thiopental sodium (Pentothal, 10 mg/kg intravenously). The dogs were intubated, and mechanical ventilation (Ventimeter ventilator, Narco Scientific, Pilling Division, Fort Washington, Pa.) was instituted with a tidal volume of 25 ml/kg at a rate of 12 breaths/min and an inspired oxygen fraction of 1.0. Anesthesia was maintained with halothane 1% to 1.5%. A 2Q-gauge catheter "was inserted into the right femoral artery for continuous monitoring of the arterial blood pressure (model 7758 multichannel recorder, Hewlett-Packard Co., Palo Alto, Calif.); arterial blood gases (model 178, Corning Inc., Corning, N.Y.) and hematocrit values were measured. After median sternotomy and ligation of the azygos vein, both venae cavae and the trachea were isolated and encircled. So that the heart would not be dislocated, only the cranial third of the anterior portion of the pericardium was opened, and the ascending aorta and main PA were encircled with umbilical tapes. After systemic heparinization (500 U /kg), a 3-0 Prolene purse-string suture (Ethicon, Inc., Somerville, N.J.) was placed into the proximal anterior wall of the main PA, and the PA was cannulated with an 8 mm aortic arch cannula (Sarns, Inc., Ann Arbor, Mich.) that had a previously inserted 19-9auge catheter (CutDown Catheter, Deseret Medical, Sandy, Utah) for PA pressure monitoring. Care was taken in the handling of the cannula to avoid occlusion of the PA lumen. A needle myocardial temperature probe (Shiley, Inc., Irvine, Calif.) was placed in the right middle lobe at a depth of 10 mm to measure the temperature during flush.
Lung preservation at 4° and 10° C
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Under stable hemodynamic conditions (systolic arterial pressure ~IOO mm Hg), 251Lg/kg PGEI (Prostin VR), diluted in 5 ml of saline, was given as a bolus via the PA pressure line into the proximal P A. The systemic blood pressure was carefully monitored, and cardiac inflow was occluded by ligation of both venae cavae when the systolic arterial pressure decreased to 50 mm Hg. The time between PGE I bolus and inflowocclusion was recorded. After amputation of the left atrial appendage and a single hyperinflation (to 30 ern water pressure) of the lungs, the PA was flushed with a 50 mljkg infusion of 4 ° C (group I) or 10° C (group II) modified (4 mEq Mg++ /L and 65 ml of 50% dextrose/L) Euro-Collins solution containing 500 1Lg/LPGE!. The solution was infused by gravity drainage from a height of 40 ern, The surgeons were blinded to the temperature of the flush solution and the lung temperature at the end of the flush. Blinding was reliably maintained since the thick flush tubing used prevented the surgeons from determining the real flush temperature. PA flush pressure was continuously monitored and maintained below 12 mm Hg by adjusting the flow rate with a clamp on the flush tubing. The left atrial effluent was allowed to pool in the chest to provide further topical cooling. The flush time was recorded, the defect in the cannula insertion site of the PA was closed after removal of the cannula, and the proximal PA was ligated. The temperature probe was removed. Ventilation was discontinued, and the trachea was divided between two clamps with the lungs in a semiinflated state. After ligation, the aorta was divided distally to the left subclavian artery and the entire heart-lung block was excised by blunt and sharp dissection with the anterior wall of the esophagus as the posterior limit of dissection and with minimal handling of both lungs. The heart-lung block was then placed in a sterile bag with 1 L of 4 ° C (group I) or 10° C (group II) modified Euro-Collins solution prepared by a technician. The closed bag was put into a second sterile bag containing 1 L of 4 ° or 10° C Ringer's lactate solution. Finally, the double-bagged heart-lung block was stored for 18 hours immersed in a water-filled container in a monitored cold room at 4° C (group I) or 10° C (group 11). Recipient operation. Before anesthesia, the dogs received cyclosporine (IS rug/kg) and azathioprine (I rug/kg) orally. Then exactly the same anesthetic procedure as described for the donor was performed, followed by administration of methylprednisolone (I gm intravenously). Before intubation, a No.8 Fogarty venous occlusion catheter (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.) was positioned in the left main-stem bronchus for occlusion during implantation of the lung. Anesthesia was maintained with a 40:60 mixture of nitrous oxide/oxygen and halothane 1% to 1.5%. Ringer's lactate solution (1.2 to 1.8 L) was infused for volume replacement during the surgical procedure. After insertion of a Swan-Ganz catheter (Baxter) in the right femoral vein and insertion of an arterial line, and after 10 minutes of ventilation in the supine position, the hematocrit value and arterial blood gases were assayed and systemic and pulmonary hemodynamics were recorded. Left lung allografts were performed in a similar fashion, as we have previously described.P: 16 After a thoracotomy in the left fifth intercostal space and intrapericardial isolation of both PAs, an inflatable silicone rubber cuff was placed around the proximal right PA to allow exclusive perfusion of the left lung after transplantation. A left pneumonectomy was then performed. The left lung was trimmed from the preserved heartlung block while floating in a bag filled with cold (4 ° to 8° C) Euro-Collins solution in a basin with sterile saline and ice cubes.
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The Journal of Thoracic and Cardiovascular Surgery
Mayeretal.
The PA stump was left as long as possible, and the donor bronchus was trimmed back to a singlecartilaginous ring above the first bifurcation; a sample of the trimmed donor bronchus was fixedin a 95% methanol/5% acetic acid solution for hjstologic assessment.During implantation, the left lung wascoveredwith cold,wet gauze. The left atrial anastomosiswas performedfirst, with use of a 5-0 Prolene everting,running, horizontal mattress suture. The PA anastomosis was performed with two running 6-0 Prolene sutures and was left untied. The bronchial anastomosis was performed with three running 4-0 Vicryl sutures (Ethicon, Inc., Somerville, N.J.) in a triangular fashion. After the transplanted lung was reinflated by hyperinflation to a pressure of 30 cm of water, the atrial clamp was removed. When back-bleedingoccurred at the PA anastomosis, the PA clamp was releasedand the PA suture was tied after the restorationof antegrade blood flow. A second inflatable silicone rubber cuff was positioned around the left proximal PA, and the injection ports connected to each cuff were implanted subcutaneously. The chest was closed in a standard fashion after intercostal neural blockade with 0.5% bupivacaine hydrochloride (10m!) and insertion of a No. 20 chest tube. Each dog was treated dai-, ly with cyclosporine (15 mg/kg orally), azathioprine (1 rug/kg orally), prednisone (l mg/kg orally), and cefazolin (l gm intravenously). Oxymorphone hydrochloride (l mg intramuscularly) was given daily, if necessary. Assessment and postoperative treatment. Routine assessments with the dog in a supine positionwere performed preoperatively and postoperatively on the day of the transplant (day 0) and 3 days later (day 3). After routine bronchoscopic examination and 10 minutes of ventilationwith 99%inspiredoxygenfraction and 1%halothane (preoperative ventilator settings, no positive end-expiratory pressure), arterial blood gases, hematocrit values,and systemic and pulmonary hemodynamics (arterial pressure, central venouspressure, PA pressure, pulmonary capillary wedgepressure [PCWPj, and cardiac output) were recorded. The same assessmentwas repeated after a 1O-minute occlusion of the left PA and again after occludingthe right PA and selectively perfusing the transplanted lung. PCWP was not measured when only one lung was perfused. During perfusionof only the transplanted lung, inflationof the balloonat the tip of the Swan-Ganz catheter in the main PA or a major branch of the PA sharply increases right ventricular afterload and significantly reduces pulmonary venousreturn to the left side of the heart, thereby causing a decrease in cardiac output and severe arterial hypotension. Measurements of PCWP and calculationsof pulmonaryvascularresistanceunder these conditions are unreliable.l" No inotropic drugs or bicarbonate infusions were givenduring the operation or assessment of the dogs. At the end of the assessment, anesthesiawasdiscontinued,each recipientreceived 20 mg furosemide (Lasix) intravenously and 1.5 mg oxymorphone hydrochloride intramuscularly, and the chest tube was removed. On the third postoperative day, the dogs were anesthetized and the same blood gas and hemodynamic assessments were repeated. After systemic heparinization, the dogs were killed and all the anastomoseswere carefully examined.The bronchial anastomosis was excised and fixed in a 95% methanol/5% acetic acid solution for histopathologicassessment. After being embedded in paraffin, longitudinal sections of the specimens were cut 4 ~m thick, stained with hematoxylin and eosin, and
examinedwitha lightmicroscope, withthe investigatorunaware of the study group, to assessthe viabilityof the proximaldonor bronchus. The same procedure was followed for the preserved donor bronchus specimens. Statistical analysis of the data was performed by paired and unpaired, double-tailed t tests, with the commercially available SAS software package (SAS Inc., Cary, N.C.). All values are presented as mean ± standard error of the mean. Statistical significance was assumed for a p value lessthan 0.05. The animals received humane care in compliancewith 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" prepared by the National Academyof Sciences and published by the National Institutes of Health (NIH Publication No. 80-23, revised 1978). Results The two groups were similar with respect to donor weights (group I, 22.3 ± 1.0 kg; group 11,19.5 ± 1.1 kg), recipient weights (group I, 22.0 ± 0.5 kg; group II, 20.1 ± 0.7 kg), total ischemic time (group 1,18.6 ± 0.1 hours; group II, 18.6 ± 0.08 hours), and implantation time (group I, 60.6 ± 1.2 minutes; group II, 63.3 ± 1.4 minutes). During routine sacrifice on day 3, we found a left lower lobe infarction caused by kinking and thrombosis of the inferior pulmonary vein in one dog in group I. Another dog in group I died of cardiac arrest during induction on day 3, probably because of an anesthetic overdose. The arterial oxygen tension (Pao-) measured on day 0 in this dog when the transplanted lung was perfused was 496 mm Hg. The data from these two animals are not included in the study; therefore the results of six experiments in each group are reported. Flush procedure. The time from PGE 1 bolus to inflow occlusion was similar in the two groups (group I, 36.8 ± 3.8 seconds; group II, 42.3 ± 3.2 seconds; p = 0.30). There was no significant difference in flush pressure (group I, 9.8 ± 0.7 mm Hg; group II, 10.1 ± 1.1 mm Hg; p = 0.8) and flush time (group I, 35.1 ± 2.4 seconds; group II, 35.3 ± 3.0 seconds; p Om;= 0.96) between the groups. The right lung temperatureattheendoftheflush was 15.3° ± 1.1 ° Cin the 4° C group and 19.9° ± 1.9° C in the 10° C group (p = 0.06). Blood gas measurements. The results of day 0 and day 3 blood gas analyses and hemodynamic assessments for the transplanted lungs are shown in Table I. With selective perfusion of the transplanted lung, there was no significant difference in Pao- between the two groups on day o (Fig. 1; P = 0.61). When both lungs were perfused on day 0, the Pao, was 526 ± 71 mm Hg in group I and 589 ± 27 mm Hg in group II (p = 0.48). On day 3, oxygenation generated by the transplanted lung alone had significantly improved in
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Lung preservation at 4 0 and 10 0 e l l 3 9
Pa02 (mmHg) 700 ,.----=---.:.---
-
-
-
-
-
- - - - - - -p-O .034 n
Cay 0
-
-
-----,
p-O .038 ve D.y 0
Day 3
Day 0
TIME
I-
0
4 C (n·S)
_
10
0
C (n·S)
I
Fig. 1. Oxygenation of transplanted lung (4 0 C versus 100 C groups). Inspired oxygen fraction, 1.0; all values are mean ± standard error of the mean.
Table I. Assessment offunction of transplanted lung Day 0 4 0 C group
Paoz (mm Hg) Paco, (mm Hg)
BE
mPAP (rnm Hg)
CO (Lj'min)
451 40 -4.1 26 2.1
Day 3 100 C group
4 0 C group
100 C group
497 ± 37 40 ± 1 -2.5 ± 0.7 25 ± 1.5 2.2 ± 0.2
551 ± 57* 40 ± 2 -3.9 ± 1.1 26 ± 1.5 2.2 ± 0.1
587 41 -4.6 25 2.1
± 82 ± 2 ± 0.4 ± 1.8 ± 0.2
± 19* ± 3 ± 1.0 ± 3.0 ± 0.2
Pa02. Arterial oxygen tension; Pacos, arterial carbon dioxide tension; BE, base excess; mPAP, mean pulmonary artery pressure; CO. cardiac output. All values are mean ± standard error of the mean; n = 6 for each group. •p < 0.05 versus day O.
both groups (group I, p = 0.034; group II, p = 0.038); Pao- was again similar in the two groups (Table I; p = 0.55). Hemodynamics. Cardiac output, mean arterial pressure, and central venous pressure with perfusion of the transplanted lungaloneweresimilarin the twogroupson both day 0 and day 3. Mean PA pressureduring occlusion ofthe right PA did notdifferin the twogroupsonday o(groupI, 26 ± 1.8mm Hg; group II, 25 ± 1.5mm Hg; p = 0.64)and day 3 (group I, 26 ± 1.5mm Hg; groupII, 25 ± 3.0 mm Hg; p = 0.70). Bronchial viability. All donor bronchial specimens taken immediately after 18 hours of preservation were structurallyintact,including the epithelium. On day 3,no sloughing or necrosis of the proximal donorbronchuswas observed macroscopically in any of the dogs. However, histologic examination showed that confluent donorbronchus epithelium within 2 mm distal to the anastomosis wasapparent in onlythree dogsin each group.There was
severe inflammation and lymphocyte infiltration in five of the donor bronchi (two in group I; three in group II). There was no overalldifference in bronchial viability on day 3 between the two study groups. Discussion
Rapid cooling, washout of the vasculature, and hypothermic storage are considered to be basic tenets of lung preservation. Several studies have shown superior heart preservation at moderate (100 to 150C) storage temperatures in comparison with deep hypothermia (4 0 C),18, 19 presumably becauseof a failure of calcium homeostasis at profound hypothermia.!? However, other studies have demonstratedsuperiorpreservation of canine hearts with deep hypothermia (4 0 C).20, 21 Furthermore, myocardial adenosine triphosphate (ATP) levels and an adequate ratio between ATP generatingmechanisms and ATP use are better preserved at lower temperatures.18, 22 These findings may also be important for lung preservation;
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Mayer et al.
however, because the complex effects of ischemia, cooling, and reperfusion on the function of different organs are not known,it is possible that different organs require different preservation methods, solutions, and temperatures. The optimal temperature for lung preservation has not been systematicallystudied and 4° C preservationis routinely reported,14,23,24 although it is likely that the current clinical donor lung transportation procedure (lungs in bags ofcoolsolutionon ice) provides lowerpreservation temperatures than 4°C, as reported for hearts stored under the same conditions.P As in preservation for other organs, hypothermic storage of lung grafts at subzero temperatures resulted in poor lung functionduring reperfusion." Storage of canine lungs at 10° C27 and 4° C28 has been shown to provide better preservation than normothermic storage. Hall and coworkers-? demonstrated a significantly higher energy state in degassed rabbit lungs preserved at 4° C in comparison with those preservedat 37° C. In an exvivo rabbit lung preparation, Wang and coworkers'{ demonstrated improved lung preservationand extended preservation times after saline immersionat 10° C compared withlower(4° C) or higher (I5° C) preservation temperatures. A subsequent study in our laboratory with use of a similar rabbit model also showedbetter preservationat 10° C compared with 4° C after low-dose PGEI administration and PA flush with low-potassium dextran solution, but similarlypoorresults at 4° and 10° C whenEuro-Collins solutionwas used." In the present study, gas exchange and hemodynamic function of the transplanted lung on day 0 and day 3 were excellentafter lung preservationfor 18 hours in both the 4° and 10° C groups. In contrast toprevious work in a rabbit model.P:30 there was no improvement in preservation with moderate hypothermia. These differences may be due to differences in species, preservation techniques, solutions, or modelsused (or all of these). Hypothermia induces decreased activity of membrane transport mechanisms, allowing transmembrane diffusion downconcentration gradients." For extracellulartypesof preservationsolutions, this processmay permit the inflow of sodium ion and water into the cellwith subsequentcell swelling," decrease the membrane potentialof the plasma membrane, and deplete cellular potassium." During storage in an extracellular type solution, a higher preservation temperature, with higher activity of the sodium-potassium ATPase pump, could providebetter ion homeostasis. It might be possible that preservation at 4°C with an intracellular typesolutiondoesnot requirethe moreactive membrane transport mechanisms that may accompany higher storage temperature becausethere are no large ion concentration gradients between the extracellular and intracellular spaces. Therefore solutions with different
The Journal of Thoracic and Cardiovascular Surgery
ionic composition may well require different ranges of storage temperature to achieve optimal preservation. Despite all of these theoretical considerations, in the present study function of the transplanted lung was similar after 4° and 10° Cpreservation. Both temperatures seem to lie within an adequate range for reliable 18-hour pulmonary preservation with PA flushwith Euro-Collins solution after high-dose PGE 1 administration. PA flush with modified Euro-Collins solution after prostanoid vasodilator pretreatment of the donor is currentlythe mostcommonlyused techniquefor clinical lung preservation up to 6 to 9 hoursv 13, 14; this technique is thought to be effective for rapid coolingand washout of the pulmonary vasculature.16, 32 Severalstudies reported beneficial effectson lung preservation of donor pretreatment with PGE1 or prostacyclin and emphasize the vasodilation effects of these drugs.P: 33, 34 Previous studies in our laboratory reported inferior lung preservation by PA flush with Euro-Collins solution compared with flushwith a low-potassium dextran solution whenno vasodilator was administered.16, 35 However, using a canine left lung allograft model,Puskas and coworkers'" demonstrated that an intravenous infusion of PGE 1 before Euro-Collins or low-potassium dextran flush produced similar 18-hour4° C preservation.l" In the present study we administereda large bolus (25 ~g/kg) of PGEI to achievecomplete pulmonary vasodilation beforeflush and added 500 ~g PGEI per liter to the Euro-Collins flush solution for vasodilation during flush. We obtained a high-flow, low-pressure flush by these means and observed excellentgas exchangein the transplanted lungs at 4° and 10° C. It is unlikelythat any temperature-induced change in flush viscosity might significantly alter the pulmonary vascular resistanceduring flush sinceflush pressuresand times were similar at 4° and 10° C. BecauseHaverich.F Hooper.F and their coworkers reported distinctlydifferent gradients of flush perfusion in different areas of the lung, we do not consider that our method of measuring lung temperature during flush with only one probe in the contralateral middle lobe is representativeof the cooling profile of the wholelung; however, accurate temperature monitoring of all the parts of the left lung with several needles in each lobe would present potential technical difficulties because of parenchymal air leaks in this survivalmodel.The inaccuracy of the temperature monitoring, the short interaction time betweenflushsolution and lung tissue, and the continued ventilation with a room temperature gas mixture during flush are possible explanations for the moderate initial coolingby the flush procedure (end-flush lung temperature, 15.3° C in group I; 19.9° C in group 11). A higher flush volumecould possibly improve the cooling process.
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The fact that the function ofthe transplanted lungs was excellent after 18 hours of preservation despite moderate initial cooling may reflect the relative importance of the washout of the vasculature of possibly harmful constituents (white blood cells, platelets, erythrocytes, complement) that might cause capillary occlusion or rupture during flush and vascular and alveolar damage during preservation and reperfusion. Complete pulmonary vasodilation with a high dose of PGE r seems to facilitate this washout process, improve pulmonary microcirculation, and diminish ischemia-reperfusion injury. It is also possible that PGE 1 has some direct cytoprotective effect that ameliorates ischemia-reperfusion injury. The large tidal volumes (25 ml/kg) used and the vigorous inflation to 30 em water pressure, eliminating gross atelectasis before PA flushing, may also have contributed to the excellent postpreservation function. Increased lung volume is known to release surfactant from type II cells 38 and acts as a potent pulmonary vasodilator.I? The role of lung volume in pulmonary preservation deserves further study. Ischemic airway complications still create significant problems in clinical lung transplantation.P We have speculated that the quality of lung preservation would correlate with the degree of airway viability after transplantation. The ischemic preservation period alone did not affect gross or histologic airway structure. Three days after transplantation, however, reperfusion injury to donor bronchial structures could be shown histologically with no difference between the two study groups. This occurred in the absence of macroscopic evidence of ischemia. We conclude that excellent 18-hour lung preservation can be achieved by high-flow, low-pressure PA flush with modified Euro-Collins solution after optimal vasodilation with a large bolus ofPGE r• Under these conditions, flush and storage at 10° C offer no preservation benefit over the commonly reported 4°C. We acknowledgethe excellenttechnical assistanceof S. Diamant and J. Mates. We thank Upjohn Canada Ltd., Toronto, Ontario, Canada, for providingthe PGE r (Prostin VR) for this study. REFERENCES I. Cooper JD, Pearson FG, Patterson GA, et al. Technique of successful lung transplantation in humans. J THORAC CARDIOVASC SURG 1987;93:173-81. 2. Patterson GA, Cooper JD, Dark MB, Jones MB, and the Toronto Lung Transplant Group. Experimental and clinical double lung transplantation. J THORAC CARDIOVASC SURG 1988;95:70-4. 3. Grossman RF, Frost A, Zamel N, et al. Results of singlelung transplantation for bilateral pulmonary fibrosis. N Engl J Med 1990;322:727-33.
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4. Calhoon JH, Grover FL, Gibbons WJ, et al. Single lung transplantation: alternative indications and technique. J THORAC CARDIOVASC SURG 1991;101:816-25. 5. Haverich A, Scott WC, Jamieson SW. Twenty years of lung preservation-a review. Heart Transplant 1985; 4:234-40. 6. Belzer FO, Southard JH. Principles of solid-organ preservation by cold storage. Transplantation 1988;45:673-6. 7. Martin DR, Scott DF, Downes GL, Belzer FO. Primary cause of unsuccessful liver and heart preservation: cold sensitivityof the ATPase system. Ann Surg 1972;175:1117.
8. WillisJS. The possiblerole of cellular K for survivalof cells at low temperature. Cryobiology 1972;9:351-66. 9. MacKnight ADC, Leaf A. Regulation of cellular volume. PhysiolRev 1977;57:510-57. 10. Fuhrman GJ, Fuhrman FA. Utilization of glucose by the hypothermic rat. Am J PhysioI1963;205:181-3. II. Kurihara S, Sakai T. Effect of rapid coolingon mechanical and electrical responsesin ventricular muscle of guinea-pig. J PhysioI1985;361:361-78. 12. Wang LS, Yoshikawa K, Miyoschi S, et al. The effect of ischemic time and temperature on lung preservation in a simple ex vivorabbit model used for functional assessment. J THORAC CARDIOVASC SURG 1989;98:333-42. 13. Harjula AU, BaldwinJC, Stinson EB, Oyer PE, Shumway NE. Clinical heart-lung preservation with prostaglandin E[. Transplant Proc 1987;14:4101-2. 14. Pasque MK, Cooper JD, Kaiser LR, Haydock DA, Triantafillou A, Trulock EP. Improved technique for bilateral lung transplantation: rationale and initial clinical experience. Ann Thorac Surg 1990;49:785-91. 15. Jones MT, Hsieh C, Yoshikawa K, Patterson GA, Cooper JD. A new model for assessment of lung preservation. J THORAC CARDIOVASC SURD 1988;96:608-14. 16. Keshavjee SH, Yamazaki F, Cardoso PF, McRitchie OI, Patterson GA, Cooper JD. A method for safe twelve-hour pulmonary preservation. J THORAC CARDIOVASC SURG 1989;98:529-34. 17. Wittnich C, Trudel J, Zidulka A, Chiu RCJ. Misleading "pulmonary wedge pressure" after pneumonectomy: its importance in postoperative fluid therapy. Ann Thorac Surg 1986;42:192-6. 18. Tyers GFO, Williams EH, Hughes HC, Todd GJ. Effect of perfusate temperature on myocardial protection from ischemia. J THORAC CARDIOVASC SURG 1977;73:76671. 19. Keon WJ, Hendry PJ, Taichman GC, Mainwood GW. Cardiac transplantation: the ideal myocardium temperaturefor graft transport. Ann Thorac Surg 1988;46:337-41. 20. Swanson DK, Dufek JH, Kahn DR. Improved myocardial preservation at 4° C. Ann Thorac Surg 1980;30:519-26. 21. Rosenfeldt FL. The relationship between myocardial temperature and recovery after experimental cardioplegic arrest. J THORAC CARDIOVASC SURG 1982;84:656-66. 22. Deslauriers R, Keon WJ, Lareau S, et al. Preservation of high-energy phosphates in human myocardium: a phosphorus 3 l-nuclear magnetic resonance study of the effect
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of temperature on atrial appendages. J THORAC CARDIOVASC SURG 1989;98:402-12. 23. Baldwin JC, Frist WH, Starkey TD, et al. Distant graft procurement for combined heart and lung transplantation using pulmonary artery flush and simple topical hypothermia for graft preservation. Ann Thorac Surg 1987;43: 670-3. 24. Cooper JD, Patterson GA, Grossman R, Maurer J, and the Toronto Lung Transplant Group. Double-lung transplant for advanced chronic obstructive lung disease. Am Rev Respir Dis 89;139:303-7. 25. HendryPJ, WalleyVM, KoshalA,Masters RG,Keon WJ. Are temperatures attained by donor hearts during transport too cold? J THORAC CARDIOVASC SURG 1989;98:517-22. 26. Okaniwa G, Nakada T, Kawakami M, et al. Studies on the preservation of canine lung at subzero temperatures. J THORAC CARDIOVASC SURG 1973;65:180-6. 27. Joseph WL, Morton DL. Influence of ischemia and hypothermia on the ability of the transplanted primate lung to provide immediate and total respiratory support. J THORAC CARDIOVASC SURG 1971;62:752-61. 28. Kondo Y, Turner MD, Cockrell JV. Ischemic tolerance of the canine autotransplanted lung. Surgery 1974;76:447-53. 29. Hall TS, Buescher PC, Borkon AM, Reitz BA, Michael JR, Baumgartner WA. 31p Nuclear magnetic resonance determinations of changes in energy state in lung preservation. Circulation 1988;78 (Pt 2):III958. 30. UenoT, YokomiseH, Oka T, etal. The effect ofPGE 1 and temperature on lung function following preservation. Transplantation (In press). 31. Collins GH, Bravo-Shugarman MB, Terasaki PI. Kidney preservation for transportation: initial perfusion and 30 hour ice storage. Lancet 1969;2:1219-22. 32. Haverich A, Aziz S, Scott WC, Jamieson SW, Shumway
The Journal of Thoracic and Cardiovascular Surgery
NE. Improved lung preservation using Euro-Collins solution for flush-perfusion. Thorac Cardiovasc Surg 1986; 34:368-76. 33. Mulvin D, Jones K, Howard R, Grosso M, Repine J, Johnston M. The effect of prostacyclin as a constituent of a preservation solution in protecting lungs from ischemic injury because of its vasodilatory properties. Transplantation 1990;49:828-30. 34. Hooper TL, Thompson DS, Jones MT, et al. Amelioration of lung ischemic injury with prostacyclin. Transplantation 1990;49:1031-5. 35. Yamazaki F, Yokomise H, Keshavjee SH, et al. The superiority of an extracellular fluid solution over Euro-Collins solution for pulmonary preservation. Transplantation 1990; 49:690-4. 36. Puskas JD, Cardoso PFG, Mayer E, Shi SQ, Slutsky AS, Patterson GA. Equivalent eighteen-hour lung preservation by pulmonary artery flush with low potassium dextran or Euro-Collins solution after prostaglandin E, infusion. J THORAC CARDIOVASC SURG (In press). 37. Hooper TL, Fetherston GJ, -Plecknell PA, Dark JH, McGregor CGA. The use of a prostacyclin analog, Iloprost, as an adjunct to pulmonary preservation with Euro-Collins solution. Transplantation 1990;49:495-9. 38. Nicholas TE, Barr HA. Control of release of surfactant phospholipids in the isolated perfused rat lung. J Appl PhysioI1981;51:90-8. 39. Pirlo AF, Benumof JL, Trousdale FR. Atelectatic lobe blood flow:open vs. closed chest, positive pressure vs. spontaneous ventilation. J Appl Physiol 1981;50:1022-6. 40. Patterson GA, Todd TR, Cooper JD, et al. Airway complications following double lung transplantation. J THORAC CARDIOVASC SURG 1990;99:14-21.
Lng transplantation has been used successfully in the treatment of selected patients with end-stage pulmonary disease. 1-4 Broader application of this procedure is severeFrom the Division of Thoracic Surgery, Department of Surgery, University of Toronto, Toronto General Hospital, Toronto, Ontario, Canada. Supported by Medical Research Council grant 10142. Received for publication Sept. 14, 1990. Accepted for publication March 5, 1991. Address for reprints: G. A. Patterson, MD, One Barnes Hospital Plaza, Suite 3108 Queeny Tower, St. Louis, MO 63110. *Supported by the Department of Cardiothoracic and Vascular Surgery, Johannes Gutenberg-University Clinics, Mainz, FRG, and the Deutsche Forschungsgemeinschaft; present address: Department of Cardiothoracic and Vascular Surgery, Johannes Gutenberg-University Clinics, D-6500 Mainz, FRG. 12/1/30719
I I 36
ly limited by the current shortage of suitable donor lungs. Although lung preservation has been studied extensively for almost 30 years' a reliable clinical technique of lung preservation beyond 6 hours has not been achieved. Better methods oflung preservation would allow an extension of the safe ischemic time and therefore increase the quantity and quality of available lung grafts and facilitate an adequate matching of donor organs and recipients. On the basis of results in solid organ transplantation.? a lung preservation temperature of 4 0 C isconsidered (but not proved) to provide optimal graft function, presumably by slowing down cellular enzyme activity and metabolism. However, there are known detrimental effects of hypothermia on a number of cellular mechanisms, including membrane permeability.?'? glucose use.l'' calcium sequestration, 1I and cellular osmotic homeostasis.?" Wang and colleagues'? have used an ex vivo rabbit lung
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model and found that 10° C storage with simple immersion provided better lung preservation than the universally used 4 ° C. Thus the optimal preservation temperature remains to be investigated in an in vivo survival model with the use of a pulmonary flush preservation technique. Most clinical lung and heart-lung transplantation programs have preserved donor lungs by means of vasosodilator prostanoid pretreatment followed by pulmonary artery (PA) flush with cold (4° C) modified crystalloid solutions.v 13, 14 However, there is no agreement as to the vasodilator or the dose required. Furthermore, it is not known whether P A flush and subsequent preservation could be enhanced by increased pulmonary vasodilation with a higher dose of vasodilator prostanoid. The present study was designed to compare the effects on lung function of 18-hour preservation by P A flush and storage at 4° and 10° C in a canine left lung allotransplantation model after donor pretreatment with a large bolus dose of prostaglandin EI (PGE 1) .
Material and methods Pairs of weight-matched mongrel dogs underwent left lung allotransplantation. Donor lungs were randomly assigned in a blinded fashion to one of two study groups. The flush and storage temperature was 4° C in group I (n = 8) and 10° C in group II (n = 6). Donor operation. After pretreatment with atropine (0.5 mg intravenously) and cefazolin (I gm intravenously) and sedation with meperidine (50 mg intravenously) and acepromazine (I mg intravenously), the donor dogs were anesthetized with thiopental sodium (Pentothal, 10 mg/kg intravenously). The dogs were intubated, and mechanical ventilation (Ventimeter ventilator, Narco Scientific, Pilling Division, Fort Washington, Pa.) was instituted with a tidal volume of 25 ml/kg at a rate of 12 breaths/min and an inspired oxygen fraction of 1.0. Anesthesia was maintained with halothane 1% to 1.5%. A 2Q-gauge catheter "was inserted into the right femoral artery for continuous monitoring of the arterial blood pressure (model 7758 multichannel recorder, Hewlett-Packard Co., Palo Alto, Calif.); arterial blood gases (model 178, Corning Inc., Corning, N.Y.) and hematocrit values were measured. After median sternotomy and ligation of the azygos vein, both venae cavae and the trachea were isolated and encircled. So that the heart would not be dislocated, only the cranial third of the anterior portion of the pericardium was opened, and the ascending aorta and main PA were encircled with umbilical tapes. After systemic heparinization (500 U /kg), a 3-0 Prolene purse-string suture (Ethicon, Inc., Somerville, N.J.) was placed into the proximal anterior wall of the main PA, and the PA was cannulated with an 8 mm aortic arch cannula (Sarns, Inc., Ann Arbor, Mich.) that had a previously inserted 19-9auge catheter (CutDown Catheter, Deseret Medical, Sandy, Utah) for PA pressure monitoring. Care was taken in the handling of the cannula to avoid occlusion of the PA lumen. A needle myocardial temperature probe (Shiley, Inc., Irvine, Calif.) was placed in the right middle lobe at a depth of 10 mm to measure the temperature during flush.
Lung preservation at 4° and 10° C
I I 37
Under stable hemodynamic conditions (systolic arterial pressure ~IOO mm Hg), 251Lg/kg PGEI (Prostin VR), diluted in 5 ml of saline, was given as a bolus via the PA pressure line into the proximal P A. The systemic blood pressure was carefully monitored, and cardiac inflow was occluded by ligation of both venae cavae when the systolic arterial pressure decreased to 50 mm Hg. The time between PGE I bolus and inflowocclusion was recorded. After amputation of the left atrial appendage and a single hyperinflation (to 30 ern water pressure) of the lungs, the PA was flushed with a 50 mljkg infusion of 4 ° C (group I) or 10° C (group II) modified (4 mEq Mg++ /L and 65 ml of 50% dextrose/L) Euro-Collins solution containing 500 1Lg/LPGE!. The solution was infused by gravity drainage from a height of 40 ern, The surgeons were blinded to the temperature of the flush solution and the lung temperature at the end of the flush. Blinding was reliably maintained since the thick flush tubing used prevented the surgeons from determining the real flush temperature. PA flush pressure was continuously monitored and maintained below 12 mm Hg by adjusting the flow rate with a clamp on the flush tubing. The left atrial effluent was allowed to pool in the chest to provide further topical cooling. The flush time was recorded, the defect in the cannula insertion site of the PA was closed after removal of the cannula, and the proximal PA was ligated. The temperature probe was removed. Ventilation was discontinued, and the trachea was divided between two clamps with the lungs in a semiinflated state. After ligation, the aorta was divided distally to the left subclavian artery and the entire heart-lung block was excised by blunt and sharp dissection with the anterior wall of the esophagus as the posterior limit of dissection and with minimal handling of both lungs. The heart-lung block was then placed in a sterile bag with 1 L of 4 ° C (group I) or 10° C (group II) modified Euro-Collins solution prepared by a technician. The closed bag was put into a second sterile bag containing 1 L of 4 ° or 10° C Ringer's lactate solution. Finally, the double-bagged heart-lung block was stored for 18 hours immersed in a water-filled container in a monitored cold room at 4° C (group I) or 10° C (group 11). Recipient operation. Before anesthesia, the dogs received cyclosporine (IS rug/kg) and azathioprine (I rug/kg) orally. Then exactly the same anesthetic procedure as described for the donor was performed, followed by administration of methylprednisolone (I gm intravenously). Before intubation, a No.8 Fogarty venous occlusion catheter (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.) was positioned in the left main-stem bronchus for occlusion during implantation of the lung. Anesthesia was maintained with a 40:60 mixture of nitrous oxide/oxygen and halothane 1% to 1.5%. Ringer's lactate solution (1.2 to 1.8 L) was infused for volume replacement during the surgical procedure. After insertion of a Swan-Ganz catheter (Baxter) in the right femoral vein and insertion of an arterial line, and after 10 minutes of ventilation in the supine position, the hematocrit value and arterial blood gases were assayed and systemic and pulmonary hemodynamics were recorded. Left lung allografts were performed in a similar fashion, as we have previously described.P: 16 After a thoracotomy in the left fifth intercostal space and intrapericardial isolation of both PAs, an inflatable silicone rubber cuff was placed around the proximal right PA to allow exclusive perfusion of the left lung after transplantation. A left pneumonectomy was then performed. The left lung was trimmed from the preserved heartlung block while floating in a bag filled with cold (4 ° to 8° C) Euro-Collins solution in a basin with sterile saline and ice cubes.
1138
The Journal of Thoracic and Cardiovascular Surgery
Mayeretal.
The PA stump was left as long as possible, and the donor bronchus was trimmed back to a singlecartilaginous ring above the first bifurcation; a sample of the trimmed donor bronchus was fixedin a 95% methanol/5% acetic acid solution for hjstologic assessment.During implantation, the left lung wascoveredwith cold,wet gauze. The left atrial anastomosiswas performedfirst, with use of a 5-0 Prolene everting,running, horizontal mattress suture. The PA anastomosis was performed with two running 6-0 Prolene sutures and was left untied. The bronchial anastomosis was performed with three running 4-0 Vicryl sutures (Ethicon, Inc., Somerville, N.J.) in a triangular fashion. After the transplanted lung was reinflated by hyperinflation to a pressure of 30 cm of water, the atrial clamp was removed. When back-bleedingoccurred at the PA anastomosis, the PA clamp was releasedand the PA suture was tied after the restorationof antegrade blood flow. A second inflatable silicone rubber cuff was positioned around the left proximal PA, and the injection ports connected to each cuff were implanted subcutaneously. The chest was closed in a standard fashion after intercostal neural blockade with 0.5% bupivacaine hydrochloride (10m!) and insertion of a No. 20 chest tube. Each dog was treated dai-, ly with cyclosporine (15 mg/kg orally), azathioprine (1 rug/kg orally), prednisone (l mg/kg orally), and cefazolin (l gm intravenously). Oxymorphone hydrochloride (l mg intramuscularly) was given daily, if necessary. Assessment and postoperative treatment. Routine assessments with the dog in a supine positionwere performed preoperatively and postoperatively on the day of the transplant (day 0) and 3 days later (day 3). After routine bronchoscopic examination and 10 minutes of ventilationwith 99%inspiredoxygenfraction and 1%halothane (preoperative ventilator settings, no positive end-expiratory pressure), arterial blood gases, hematocrit values,and systemic and pulmonary hemodynamics (arterial pressure, central venouspressure, PA pressure, pulmonary capillary wedgepressure [PCWPj, and cardiac output) were recorded. The same assessmentwas repeated after a 1O-minute occlusion of the left PA and again after occludingthe right PA and selectively perfusing the transplanted lung. PCWP was not measured when only one lung was perfused. During perfusionof only the transplanted lung, inflationof the balloonat the tip of the Swan-Ganz catheter in the main PA or a major branch of the PA sharply increases right ventricular afterload and significantly reduces pulmonary venousreturn to the left side of the heart, thereby causing a decrease in cardiac output and severe arterial hypotension. Measurements of PCWP and calculationsof pulmonaryvascularresistanceunder these conditions are unreliable.l" No inotropic drugs or bicarbonate infusions were givenduring the operation or assessment of the dogs. At the end of the assessment, anesthesiawasdiscontinued,each recipientreceived 20 mg furosemide (Lasix) intravenously and 1.5 mg oxymorphone hydrochloride intramuscularly, and the chest tube was removed. On the third postoperative day, the dogs were anesthetized and the same blood gas and hemodynamic assessments were repeated. After systemic heparinization, the dogs were killed and all the anastomoseswere carefully examined.The bronchial anastomosis was excised and fixed in a 95% methanol/5% acetic acid solution for histopathologicassessment. After being embedded in paraffin, longitudinal sections of the specimens were cut 4 ~m thick, stained with hematoxylin and eosin, and
examinedwitha lightmicroscope, withthe investigatorunaware of the study group, to assessthe viabilityof the proximaldonor bronchus. The same procedure was followed for the preserved donor bronchus specimens. Statistical analysis of the data was performed by paired and unpaired, double-tailed t tests, with the commercially available SAS software package (SAS Inc., Cary, N.C.). All values are presented as mean ± standard error of the mean. Statistical significance was assumed for a p value lessthan 0.05. The animals received humane care in compliancewith 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" prepared by the National Academyof Sciences and published by the National Institutes of Health (NIH Publication No. 80-23, revised 1978). Results The two groups were similar with respect to donor weights (group I, 22.3 ± 1.0 kg; group 11,19.5 ± 1.1 kg), recipient weights (group I, 22.0 ± 0.5 kg; group II, 20.1 ± 0.7 kg), total ischemic time (group 1,18.6 ± 0.1 hours; group II, 18.6 ± 0.08 hours), and implantation time (group I, 60.6 ± 1.2 minutes; group II, 63.3 ± 1.4 minutes). During routine sacrifice on day 3, we found a left lower lobe infarction caused by kinking and thrombosis of the inferior pulmonary vein in one dog in group I. Another dog in group I died of cardiac arrest during induction on day 3, probably because of an anesthetic overdose. The arterial oxygen tension (Pao-) measured on day 0 in this dog when the transplanted lung was perfused was 496 mm Hg. The data from these two animals are not included in the study; therefore the results of six experiments in each group are reported. Flush procedure. The time from PGE 1 bolus to inflow occlusion was similar in the two groups (group I, 36.8 ± 3.8 seconds; group II, 42.3 ± 3.2 seconds; p = 0.30). There was no significant difference in flush pressure (group I, 9.8 ± 0.7 mm Hg; group II, 10.1 ± 1.1 mm Hg; p = 0.8) and flush time (group I, 35.1 ± 2.4 seconds; group II, 35.3 ± 3.0 seconds; p Om;= 0.96) between the groups. The right lung temperatureattheendoftheflush was 15.3° ± 1.1 ° Cin the 4° C group and 19.9° ± 1.9° C in the 10° C group (p = 0.06). Blood gas measurements. The results of day 0 and day 3 blood gas analyses and hemodynamic assessments for the transplanted lungs are shown in Table I. With selective perfusion of the transplanted lung, there was no significant difference in Pao- between the two groups on day o (Fig. 1; P = 0.61). When both lungs were perfused on day 0, the Pao, was 526 ± 71 mm Hg in group I and 589 ± 27 mm Hg in group II (p = 0.48). On day 3, oxygenation generated by the transplanted lung alone had significantly improved in
Volume 103 Number 6 June 1992
Lung preservation at 4 0 and 10 0 e l l 3 9
Pa02 (mmHg) 700 ,.----=---.:.---
-
-
-
-
-
- - - - - - -p-O .034 n
Cay 0
-
-
-----,
p-O .038 ve D.y 0
Day 3
Day 0
TIME
I-
0
4 C (n·S)
_
10
0
C (n·S)
I
Fig. 1. Oxygenation of transplanted lung (4 0 C versus 100 C groups). Inspired oxygen fraction, 1.0; all values are mean ± standard error of the mean.
Table I. Assessment offunction of transplanted lung Day 0 4 0 C group
Paoz (mm Hg) Paco, (mm Hg)
BE
mPAP (rnm Hg)
CO (Lj'min)
451 40 -4.1 26 2.1
Day 3 100 C group
4 0 C group
100 C group
497 ± 37 40 ± 1 -2.5 ± 0.7 25 ± 1.5 2.2 ± 0.2
551 ± 57* 40 ± 2 -3.9 ± 1.1 26 ± 1.5 2.2 ± 0.1
587 41 -4.6 25 2.1
± 82 ± 2 ± 0.4 ± 1.8 ± 0.2
± 19* ± 3 ± 1.0 ± 3.0 ± 0.2
Pa02. Arterial oxygen tension; Pacos, arterial carbon dioxide tension; BE, base excess; mPAP, mean pulmonary artery pressure; CO. cardiac output. All values are mean ± standard error of the mean; n = 6 for each group. •p < 0.05 versus day O.
both groups (group I, p = 0.034; group II, p = 0.038); Pao- was again similar in the two groups (Table I; p = 0.55). Hemodynamics. Cardiac output, mean arterial pressure, and central venous pressure with perfusion of the transplanted lungaloneweresimilarin the twogroupson both day 0 and day 3. Mean PA pressureduring occlusion ofthe right PA did notdifferin the twogroupsonday o(groupI, 26 ± 1.8mm Hg; group II, 25 ± 1.5mm Hg; p = 0.64)and day 3 (group I, 26 ± 1.5mm Hg; groupII, 25 ± 3.0 mm Hg; p = 0.70). Bronchial viability. All donor bronchial specimens taken immediately after 18 hours of preservation were structurallyintact,including the epithelium. On day 3,no sloughing or necrosis of the proximal donorbronchuswas observed macroscopically in any of the dogs. However, histologic examination showed that confluent donorbronchus epithelium within 2 mm distal to the anastomosis wasapparent in onlythree dogsin each group.There was
severe inflammation and lymphocyte infiltration in five of the donor bronchi (two in group I; three in group II). There was no overalldifference in bronchial viability on day 3 between the two study groups. Discussion
Rapid cooling, washout of the vasculature, and hypothermic storage are considered to be basic tenets of lung preservation. Several studies have shown superior heart preservation at moderate (100 to 150C) storage temperatures in comparison with deep hypothermia (4 0 C),18, 19 presumably becauseof a failure of calcium homeostasis at profound hypothermia.!? However, other studies have demonstratedsuperiorpreservation of canine hearts with deep hypothermia (4 0 C).20, 21 Furthermore, myocardial adenosine triphosphate (ATP) levels and an adequate ratio between ATP generatingmechanisms and ATP use are better preserved at lower temperatures.18, 22 These findings may also be important for lung preservation;
1 14 0
Mayer et al.
however, because the complex effects of ischemia, cooling, and reperfusion on the function of different organs are not known,it is possible that different organs require different preservation methods, solutions, and temperatures. The optimal temperature for lung preservation has not been systematicallystudied and 4° C preservationis routinely reported,14,23,24 although it is likely that the current clinical donor lung transportation procedure (lungs in bags ofcoolsolutionon ice) provides lowerpreservation temperatures than 4°C, as reported for hearts stored under the same conditions.P As in preservation for other organs, hypothermic storage of lung grafts at subzero temperatures resulted in poor lung functionduring reperfusion." Storage of canine lungs at 10° C27 and 4° C28 has been shown to provide better preservation than normothermic storage. Hall and coworkers-? demonstrated a significantly higher energy state in degassed rabbit lungs preserved at 4° C in comparison with those preservedat 37° C. In an exvivo rabbit lung preparation, Wang and coworkers'{ demonstrated improved lung preservationand extended preservation times after saline immersionat 10° C compared withlower(4° C) or higher (I5° C) preservation temperatures. A subsequent study in our laboratory with use of a similar rabbit model also showedbetter preservationat 10° C compared with 4° C after low-dose PGEI administration and PA flush with low-potassium dextran solution, but similarlypoorresults at 4° and 10° C whenEuro-Collins solutionwas used." In the present study, gas exchange and hemodynamic function of the transplanted lung on day 0 and day 3 were excellentafter lung preservationfor 18 hours in both the 4° and 10° C groups. In contrast toprevious work in a rabbit model.P:30 there was no improvement in preservation with moderate hypothermia. These differences may be due to differences in species, preservation techniques, solutions, or modelsused (or all of these). Hypothermia induces decreased activity of membrane transport mechanisms, allowing transmembrane diffusion downconcentration gradients." For extracellulartypesof preservationsolutions, this processmay permit the inflow of sodium ion and water into the cellwith subsequentcell swelling," decrease the membrane potentialof the plasma membrane, and deplete cellular potassium." During storage in an extracellular type solution, a higher preservation temperature, with higher activity of the sodium-potassium ATPase pump, could providebetter ion homeostasis. It might be possible that preservation at 4°C with an intracellular typesolutiondoesnot requirethe moreactive membrane transport mechanisms that may accompany higher storage temperature becausethere are no large ion concentration gradients between the extracellular and intracellular spaces. Therefore solutions with different
The Journal of Thoracic and Cardiovascular Surgery
ionic composition may well require different ranges of storage temperature to achieve optimal preservation. Despite all of these theoretical considerations, in the present study function of the transplanted lung was similar after 4° and 10° Cpreservation. Both temperatures seem to lie within an adequate range for reliable 18-hour pulmonary preservation with PA flushwith Euro-Collins solution after high-dose PGE 1 administration. PA flush with modified Euro-Collins solution after prostanoid vasodilator pretreatment of the donor is currentlythe mostcommonlyused techniquefor clinical lung preservation up to 6 to 9 hoursv 13, 14; this technique is thought to be effective for rapid coolingand washout of the pulmonary vasculature.16, 32 Severalstudies reported beneficial effectson lung preservation of donor pretreatment with PGE1 or prostacyclin and emphasize the vasodilation effects of these drugs.P: 33, 34 Previous studies in our laboratory reported inferior lung preservation by PA flush with Euro-Collins solution compared with flushwith a low-potassium dextran solution whenno vasodilator was administered.16, 35 However, using a canine left lung allograft model,Puskas and coworkers'" demonstrated that an intravenous infusion of PGE 1 before Euro-Collins or low-potassium dextran flush produced similar 18-hour4° C preservation.l" In the present study we administereda large bolus (25 ~g/kg) of PGEI to achievecomplete pulmonary vasodilation beforeflush and added 500 ~g PGEI per liter to the Euro-Collins flush solution for vasodilation during flush. We obtained a high-flow, low-pressure flush by these means and observed excellentgas exchangein the transplanted lungs at 4° and 10° C. It is unlikelythat any temperature-induced change in flush viscosity might significantly alter the pulmonary vascular resistanceduring flush sinceflush pressuresand times were similar at 4° and 10° C. BecauseHaverich.F Hooper.F and their coworkers reported distinctlydifferent gradients of flush perfusion in different areas of the lung, we do not consider that our method of measuring lung temperature during flush with only one probe in the contralateral middle lobe is representativeof the cooling profile of the wholelung; however, accurate temperature monitoring of all the parts of the left lung with several needles in each lobe would present potential technical difficulties because of parenchymal air leaks in this survivalmodel.The inaccuracy of the temperature monitoring, the short interaction time betweenflushsolution and lung tissue, and the continued ventilation with a room temperature gas mixture during flush are possible explanations for the moderate initial coolingby the flush procedure (end-flush lung temperature, 15.3° C in group I; 19.9° C in group 11). A higher flush volumecould possibly improve the cooling process.
Volume 103 Number 6 June 1992
The fact that the function ofthe transplanted lungs was excellent after 18 hours of preservation despite moderate initial cooling may reflect the relative importance of the washout of the vasculature of possibly harmful constituents (white blood cells, platelets, erythrocytes, complement) that might cause capillary occlusion or rupture during flush and vascular and alveolar damage during preservation and reperfusion. Complete pulmonary vasodilation with a high dose of PGE r seems to facilitate this washout process, improve pulmonary microcirculation, and diminish ischemia-reperfusion injury. It is also possible that PGE 1 has some direct cytoprotective effect that ameliorates ischemia-reperfusion injury. The large tidal volumes (25 ml/kg) used and the vigorous inflation to 30 em water pressure, eliminating gross atelectasis before PA flushing, may also have contributed to the excellent postpreservation function. Increased lung volume is known to release surfactant from type II cells 38 and acts as a potent pulmonary vasodilator.I? The role of lung volume in pulmonary preservation deserves further study. Ischemic airway complications still create significant problems in clinical lung transplantation.P We have speculated that the quality of lung preservation would correlate with the degree of airway viability after transplantation. The ischemic preservation period alone did not affect gross or histologic airway structure. Three days after transplantation, however, reperfusion injury to donor bronchial structures could be shown histologically with no difference between the two study groups. This occurred in the absence of macroscopic evidence of ischemia. We conclude that excellent 18-hour lung preservation can be achieved by high-flow, low-pressure PA flush with modified Euro-Collins solution after optimal vasodilation with a large bolus ofPGE r• Under these conditions, flush and storage at 10° C offer no preservation benefit over the commonly reported 4°C. We acknowledgethe excellenttechnical assistanceof S. Diamant and J. Mates. We thank Upjohn Canada Ltd., Toronto, Ontario, Canada, for providingthe PGE r (Prostin VR) for this study. REFERENCES I. Cooper JD, Pearson FG, Patterson GA, et al. Technique of successful lung transplantation in humans. J THORAC CARDIOVASC SURG 1987;93:173-81. 2. Patterson GA, Cooper JD, Dark MB, Jones MB, and the Toronto Lung Transplant Group. Experimental and clinical double lung transplantation. J THORAC CARDIOVASC SURG 1988;95:70-4. 3. Grossman RF, Frost A, Zamel N, et al. Results of singlelung transplantation for bilateral pulmonary fibrosis. N Engl J Med 1990;322:727-33.
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4. Calhoon JH, Grover FL, Gibbons WJ, et al. Single lung transplantation: alternative indications and technique. J THORAC CARDIOVASC SURG 1991;101:816-25. 5. Haverich A, Scott WC, Jamieson SW. Twenty years of lung preservation-a review. Heart Transplant 1985; 4:234-40. 6. Belzer FO, Southard JH. Principles of solid-organ preservation by cold storage. Transplantation 1988;45:673-6. 7. Martin DR, Scott DF, Downes GL, Belzer FO. Primary cause of unsuccessful liver and heart preservation: cold sensitivityof the ATPase system. Ann Surg 1972;175:1117.
8. WillisJS. The possiblerole of cellular K for survivalof cells at low temperature. Cryobiology 1972;9:351-66. 9. MacKnight ADC, Leaf A. Regulation of cellular volume. PhysiolRev 1977;57:510-57. 10. Fuhrman GJ, Fuhrman FA. Utilization of glucose by the hypothermic rat. Am J PhysioI1963;205:181-3. II. Kurihara S, Sakai T. Effect of rapid coolingon mechanical and electrical responsesin ventricular muscle of guinea-pig. J PhysioI1985;361:361-78. 12. Wang LS, Yoshikawa K, Miyoschi S, et al. The effect of ischemic time and temperature on lung preservation in a simple ex vivorabbit model used for functional assessment. J THORAC CARDIOVASC SURG 1989;98:333-42. 13. Harjula AU, BaldwinJC, Stinson EB, Oyer PE, Shumway NE. Clinical heart-lung preservation with prostaglandin E[. Transplant Proc 1987;14:4101-2. 14. Pasque MK, Cooper JD, Kaiser LR, Haydock DA, Triantafillou A, Trulock EP. Improved technique for bilateral lung transplantation: rationale and initial clinical experience. Ann Thorac Surg 1990;49:785-91. 15. Jones MT, Hsieh C, Yoshikawa K, Patterson GA, Cooper JD. A new model for assessment of lung preservation. J THORAC CARDIOVASC SURD 1988;96:608-14. 16. Keshavjee SH, Yamazaki F, Cardoso PF, McRitchie OI, Patterson GA, Cooper JD. A method for safe twelve-hour pulmonary preservation. J THORAC CARDIOVASC SURG 1989;98:529-34. 17. Wittnich C, Trudel J, Zidulka A, Chiu RCJ. Misleading "pulmonary wedge pressure" after pneumonectomy: its importance in postoperative fluid therapy. Ann Thorac Surg 1986;42:192-6. 18. Tyers GFO, Williams EH, Hughes HC, Todd GJ. Effect of perfusate temperature on myocardial protection from ischemia. J THORAC CARDIOVASC SURG 1977;73:76671. 19. Keon WJ, Hendry PJ, Taichman GC, Mainwood GW. Cardiac transplantation: the ideal myocardium temperaturefor graft transport. Ann Thorac Surg 1988;46:337-41. 20. Swanson DK, Dufek JH, Kahn DR. Improved myocardial preservation at 4° C. Ann Thorac Surg 1980;30:519-26. 21. Rosenfeldt FL. The relationship between myocardial temperature and recovery after experimental cardioplegic arrest. J THORAC CARDIOVASC SURG 1982;84:656-66. 22. Deslauriers R, Keon WJ, Lareau S, et al. Preservation of high-energy phosphates in human myocardium: a phosphorus 3 l-nuclear magnetic resonance study of the effect
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