Reliable thirty-hour lung preservation by donor lung hyperinflation

Reliable thirty-hour lung preservation by donor lung hyperinflation We examined the hypothesis that the degree of inflation of the lungs at the time of harvest may have an important role in postpreservation function. Lungs of donor dogs randomly assigned to groups 1 (n = 5) and 2 (n = 5) were ventilated with large tidal volumes (tidal volume, 25 ml/kg; positive end-expiratory pressure, 5 cm H20; respiratory rate, 12 breaths/min, inspired oxygen fraction 1.0) and were inflated to 30 em H20 for 15 seconds before pulmonary artery flush and again immediately before tracheal crossclamping. In group 3 (n = 5) donor lungs were normally ventilated (tidal volume, 12.5 ml/kg, positive end-expiratory pressure 0 cm H20; respiratory rate 12 breaths/min, inspired oxygen fraction, 1.0) and were not hyperinflated before pulmonary artery flushing; the trachea was crossclamped at end-inspiration. In groups 1 and 3 a large bolus (25 ~g/kg) of prostaglandin E 1 was injected into the pulmonary artery before flushing and was also added to the pulmonary artery flush solution (500 ~g/L). A rapid (approximately 50 seconds), high-volume (50 ml/kg), low-pressure (5 to 8 mm Hg), hypothermic (4° C) pulmonary artery flush was performed in all groups with modified Euro-Collins solution. Heart-lung blocks were stored at 4° C for approximately 29 hours before left single lung allografting. An inflatable cuff was placed around the recipient right pulmonary artery, allowing independent study of the transplanted lung. Hyperinflated lungs harvested with or without prostaglandin E 1 provided equivalently excellent early posttransplant function (arterial oxygen tension [mean ± standard deviation]: group 1; 503 ± 45, vs group 2; 529 ± 150 mm Hg; inspired oxygen fraction 1.0). Mean arterial oxygen tension was significantly lower in group 3 (116 ± 78 mm Hg) than in either groups 1 or 2 (p < 0.0002 for either comparison). Copious reperfusion pulmonary edema was a constant feature in group 3 but was not seen in groups 1 and 2. All 10 recipients in groups 1 and 2 survived the 3-day assessment period without difficulty; two of the five recipients in group 3 died during initial unilateral perfusion of the transplanted lung. Donor hyperventilation and inflation to 30 em H20 before hypothermic storage can help provide excellent posttransplantation lung function after 30-hour preservation, with or without prostaglandin E 1 pretreatment. We speculate that this improvement may be due to effects of increased lung volume on pulmonary vascular tone and/or surfactant metabolism. (J THORAC CARDIOVASC SURG 1992;104:1075-83)

John D. Puskas, MD,* Takashi Hirai, MD, Neil Christie, MD, Eckhard Mayer, MD, Arthur S. Slutsky, MD, and G. Alexander Patterson, MD, FRCS(C), Toronto, Ontario, Canada

From the Division of Thoracic Surgery, Department of Surgery, University of Toronto, Toronto General Hospital, Toronto, Ontario, Canada. Supported by Medical Research Council grant No. 10142. Received for publication May 31, 1991. Accepted for publication Jan. 3, 1992. Address for reprints: G. A. Patterson, MD, FRCS(C), Professor of Surgery, Division of Cardiothoracic Surgery, Queeny Tower, Suite 3108, One Barnes Hospital Plaza, St. Louis, MO 63110-1013. "Recipient of the E. D. Churchill Surgical Fellowship from the Massachusetts General Hospital, Harvard Medical School, Boston.

12/1/36286

DeSPite more than a quarter century of research, I no clinical method of lung preservation provides consistently excellent protection beyond 6 to 9 hours of ischemia. Improved techniques for donor lung preservation would extend allowable ischemic times, permit more distant procurement of donor lungs, allow HLA crossmatching, and improve early function of transplanted lungs. The optimal state of inflation of the lungs for pulmonary preservation was the subject of considerable scientific interest 20 years ago but has since been virtually ignored in the literature. Presently lungs are stored atelectatic.' or in various states of semi-inflation by 1075

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Puskas et al.

Table I. Experimental design Donor tidal volume (nil/kg) Donor PEEP (em H2O) Donor PGEI Bolus into pulmonary artery (,ltg/kg) Added to flush Donor hyperinflation (to 30cm H20, 15 sec) Before flush Before storage

Group 1

Group 2

Group 3

25

25

12.5

5

5

None

25

None

25

25

None

25

Yes Yes

Yes Yes

No No

Note: Fio-, 1.0; respiratory rate, 12 breaths/min throughout donor procedure in all groups; n = 5 in each group.

different clinical and experimental lung transplant programs. 1, 3 Homatas and co-workers" reported that continuous positive-pressure ventilation significantly improved the warm ischemic tolerance of canine lungs. Veith and colleagues' created a canine model of in situ normothermic lung ischemia-reperfusion and reported that deflated lungs preserved for more than 1 hour at normal body temperature could not support life. Lungs statically inflated (the lung volume was not indicated) functioned after 2 to 3 hours of normothermic ischemia (6/10 survivors), but not after 4 hours of ischemia (0/4 survivors). Joseph and Morton" performed left lung autotransplantation and reported that adequate respiratory function could be obtained in baboons after 4 hours of normothermic ischemia with the lung inflated with 100% oxygen." Stevens and co-workers provided further evidence that the prevention of lung collapse improves pulmonary preservation in both canine allotransplantation? and in situ warm ischemia-reperfusion models.'' Recognizing that atelectasis is destructive to the surfactant system, they concluded in 1972 that the prevention of alveolar collapse was a much more critical factor in lung preservation than the duration of lung ischemia.I-f Fonkalsrud and colleagues's 10 reported that static inflation or continuous ventilation with positive end-expiratory pressure (PEEP) provided superior canine pulmonary preservation compared with atelectatic storage or ventilation without PEEP. Of course, none of these earlier investigators combined the techniques of pulmonary artery flush with donor lung hyperinflation, and all employed ischemic times of less than 6 hours. More recently Locke and co-workers' reported that absorption atelectasis and topical cooling to 4 0 C for 6 hours provided very poor lung preservation, with no survivors in a canine left single lung transplant model. By

comparison, lungs perfused with Euro-Collins solution and stored after static inflation with 40% oxygen (tidal volume 15 mljkg) showed significantly superior posttransplant function and 100% survival. These authors concluded only that topical cooling is inferior to cold crystalloid pulmonary perfusion, but their results more clearly demonstrated that atelectasis must be avoided during lung preservation. In a previous study,'! we found that donor pretreatment with prostaglandin El (PGEl) improved the posttransplant function of canine lungs flushed with cold Euro-Collins solution. We concluded that pulmonary vasodilation with a prostanoid before hypothermic pulmonary artery flush with a hyperkalemic preservation solution such as Euro-Collins solution was important because it may allow more complete removal of blood constituents from the pulmonary vasculature and more rapid and uniform cooling of lung parenchyma, and might confer some inherent cytoprotective effect. The purpose of the present study was to determine whether hyperinflation of donor lungs could also improve posttransplant lung function and to compare this intervention with high-dose PGE\ administration in extended 30-hour pulmonary preservation. Materials and methods Donor procedure. Adult mongrel dogs were paired by sex and weight and randomly assigned to three groups. All donor dogs received a standard intravenous anesthetic sequence of 50 mg meperidine and 1mg acepromazine maleate, followedby 0.5 mg atropine, 1 gm cefazolin, and 10 mg/kg sodium thiopental. Donors were then intubated (8.5F catheters) and ventilated (Ventimeter Ventilator, Narco Medical Co., Pa.). In groups 1 and 2 donors were ventilated with large tidal volumes of 25 ml/kg at a rate of 12 breaths/min with PEEP of 5 cm H20 and inspired oxygen fraction (Fio-) of 1.0 (Table I). In group 3 donors were ventilated with more normal tidal volumes of 12.5 ml/kg, Fio 2 1.0, without PEEP. Halothane, 0.5% to 1.5%, was used to maintain anesthesia. Systemic blood pressure was continuously monitored through a right femoral arterial catheter. Arterial blood gases and hematocrit were assayed. After median sternotomy the aorta, main pulmonary artery, and trachea were each encircled with umbilical tapes. Heparin was administered (500 U/kg), and the right atrium was cannulated with a 51F two-stage venous drainage cannula through a purse-string suture of 2-0 silk. The main pulmonary artery was cannulated with an 8 mm aortic arch cannula through a purse-string suture of 3-0 Prolene (Ethicon, Inc., Somerville, N.J.). In groups 1 and 3 only, a large bolus (25 ,ug/kg) of PGE 1 (Prostin VR) was injected into the pulmonary artery before flushing and was also added to the pulmonary artery flush solution (500 ,ug/L). Within 30 seconds of PGE 1 administration systemic systolic blood pressure declined by at least 400/0. The proximal main pulmonary artery was ligated, and the animal was exsanguinated through the RA drainage cannula. After inflowocclusion the left atrial appendage was amputated, and in groups I and

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Lung preservation by donor hyperinflation

1 07 7

Table II. Donor data Donor weight (kg) Recipient weight (kg) Declinein SBP with PGE 1 bolus (%) PA flush time (sec) Mean PA flush pressure (rnrn Hg) Postflush lung temperature (0 C) Total ischemictime (hr) Arterial Po z* (mm Hg) Arterial Pcoz (rnm Hg) pH

Group 1

Group 2

Group 3

21 ± 3.1 21.3 ± 4.8 51 ± 8

21 ± 3.1 22.5 ± 1.5 O±O

18.8 ± 2.5 20 ± 1.9 42.2 ± 2.3

50 5.8 16 29.1 634 26.9 7.47

51.6 8.4 18.1 29.5 612 37.5 7.34

75.6 8.2 17.1 29.3 617 27.8 7.44

± 44 ± 0.4

± 2.2 ± 0.6 ± 34

± 3.2 ± 0.04

± 11 ± 3.0

± 2.1 ± 0.8 ± 27 ± 3.7 ±

om

± 13 ± 2

± 3.1 ± 0.4 ± 21 ± 3.3 ± 0.04

Note: Values expressed as mean ± standard deviation; n = 5 for each group. Key: PA, Pulmonary artery; SBP, systemic systolic blood pressure. 'During bilateral ventilation; Fio" 1.0.

2 only, the lungs were inflated for IS seconds to a pressure of 30 em H 20, which forced blood from the lungs and eliminated atelectasis. The pulmonary artery was flushed by gravity drainage from a height of 30 ern with 50 ml/kg cold (4 0 C) modified Euro-Collins solution containing 3.25% dextrose and 4 mliq/L magnesium sulfate. The pulmonary artery pressure was continuously recorded during each flush and was carefully maintained at less than 10 mm Hg by adjusting the flow rate with a clamp on the flush tubing. Ventilation of the lungs (tidal volume, 25 ml/kg; PEEP,S cm H20) was continued during the pulmonary artery flush. The cold left atrial effluent was allowed to pool in the chest, to provide additional topical cooling. After the pulmonary artery flush a fine-needle thermistor probe (Shiley, Inc., Irvine, Calif.) was inserted into the parenchyma ofthe right upper, middle, and lower lobes, to calculate an average end-flush lung temperature. Mediastinal dissection of the heart-lung block was expeditiously completed, and the right mainstem bronchus was exposed. The trachea and right mainstem bronchus were crossclamped or stapled (T A 30 stapler, Auto Suture Company Division, United States Surgical Corporation, Norwalk, Conn.) simultaneously to prevent deflation of the left lung during prolonged storage. In groups I and 2 only, this was done during a second hyperinflation of the lungs to 30 ern H20 and the lungs were maintained in a fully inflated state for hypothermic preservation. In group 3 the trachea was clamped at end-inspiration (tidal volume 12.5 ml/kg), and lungs were stored in a semi-inflated state. (Peak inspiratory pressures of donors in groups I and 2 were IS to 20 ern H 20 before hyperinflation; peak inspiratory pressures in group 3 were lower.) The heart-lung block was then placed in a sterile plastic bag containing I L of cold (4 0 C) Euro-Collins solution. A second sterile bag of cold (4 0 C) Ringer's lactate provided further cooling and mechanical cushioning. Finally, the double-bagged specimen was stored for approximately 29 hours in a monitored cold room at 4 0 C. Recipient procedure. Weight-matched recipients received IS mg/kg oral cyclosporine and I rug/kg azathioprine before undergoing general anesthesia as for the donor procedure. All recipients received 1000 mg methylprednisolone intravenously after induction and were ventilated with tidal volume, 25 ml/kg; PEEP,S em H20; Fio-, 1.0; and respiratory rate 12 breaths/ min. These parameters were chosen because they had resulted in near-normal arterial blood gases values during unilateral pulmonary perfusion in recipients during previous studies in our

laboratory. Right femoral venous Swan-Ganz and arterial catheters were introduced. After 10 minutes of supine ventilation, arterial blood gases, hematocrit, and hemodynamic assessments were recorded. Left single lung allotransplantation was performed as previously described.!? An inflatable silicone rubber cuff was placed around the recipient's proximal right pulmonary artery, allowing independent assessment of transplanted lung function. The injection port connected to the pulmonary artery cuff was implanted subcutaneously. Ringer's lactate was used for volume replacement during the procedure; no pressors or bicarbonate were given at any time. In groups I and 2 dogs were assessed on day 0 and again on day 3. In group 3 all dogs that survived initial assessment (3/5) were killed while under anesthesia after assessment on day 0 because of ethical concerns raised by fulminant pulmonary edema in this group. Each dog in groups 1 and 2 received IS mg/kg cyclosporine orally, I mg/kg azathioprine, I mg/kg prednisone orally, and I gm cefazolin intramuscularly daily. Buprenorphine, 0.3 mg intramuscularly was given daily as necessary for analgesia. Assessment. All recipient dogs were ventilated in the supine position with tidal volume, 25 rnl/kg; PEEP,S em H20; Fio, 1.0; arterial blood gases and systemic and pulmonary hemodynamics were recorded preoperatively and postoperatively. Similar determinations were repeated after a IO-minute occlusion of the right pulmonary artery. Pulmonary vascular resistance was calculated by standard formula. After assessment on day 0, each recipient was administered 40 mg furosemide intravenously and the chest tube was removed. On postoperative day 3, dogs in groups 1 and 2 were anesthetized as described previously, and underwent blood gas and hemodynamic assessment of combined and unilateral lung function as on day O. The dogs were then killed, and all the anastomoses were carefully examined. The bronchial anastomoses in groups I and 2 were preserved in 10% formalin, sectioned, and stained with hematoxylin and eosin. All dogs 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 prepared by the National Academy of Sciences and published by the National Institutes of Health (NIH Publication No. 80-23, revised 1978). Comparisons among groups were made with analysis of variance. Whenever results of the overall F test were significant, pairwise analysis was performed with the commercially available SAS software package (SAS, Cary, N.C.). Ap value less

The Journal of Thoracic and Cardiovascular Surgery

I 07 8 Puskas et al.

LUNG TEMP (~) 40,..-------------------------")

--* Group 1

-D- Group 2

.>.-.

, ...

-+- Group 3

,''-...... <,

10

""

~-----------------

OL.------------------------l

Start Flush

30

60

90

FLUSH TIME (88C) (n-5 In each group)

Fig. 1. End flush lung temperature: Groups 1,2, and 3 after Euro-Collins solution flush, 50 ml/kg, 4° C. Values expressed as mean ± standard deviation; n = 5 for each group; p not significant between groups.

than 0.05 was considered significant. All data are presented as means and standard deviations. Statistical analysis of pH values was performed after conversion to hydrogen ion concentration.

Results Donors. Donor and recipient dogs randomly assigned to the three groups had similar weights (Table II). The decline in systemic arterial blood pressure produced by the PGE\ bolus, used as an index of vasodilation, was similar in the two groups that received PGEI. The mean pulmonary artery flush times and pressures were similar between all groups. Postflush temperature showed no significant intergroup difference (Fig. I). The mean total ischemic times were also similar in all groups. Baseline donor arterial blood gas values (before sternotomy) were similar between groups I and 2, whereas arterial carbon dioxide pressure was significantly higher and pH was significantly lower in group 3 than in either group I or 2

(p < 0.006 for either comparison of each variable). Donor arterial oxygen tension (P02), however, was virtually identical between all groups. Recipients. One recipient that had been randomly assigned to group 1 exsanguinated because of a surgical error before reperfusion. This animal was therefore excluded from the study. All the other 10 recipients in groups I and 2 survived the 3-day assessment period without difficulty. Each tolerated occlusion of the native pulmonary artery for 10 minutes immediately after transplantation on day 0 with good hemodynamic stability. Despite the extended period of hypothermic ischemia in this 30-hour canine lung preservation model, variation in posttransplantation lung function was remarkably small in groups I and 2 (Table III). No significant intergroup differences were shown between the two hyperinflated groups. At the time of immediate assessment, with perfusion to the transplanted lung alone, the arterial P02 values in groups I and 2 were similarly and uniformly

Volume 104 Number 4 October 1992

Lung preservation by donor hyperinflation 1 07 9

Table III. Recipient data Group I Arterial P02 (nun Hg) Arterial Pe02 (mm Hg)

pH mPAP (mm Hg) PVR (dynes. sec . cm ") Pulmonary edema (gross inspection)

Group 2

Day 0

Day 3

Day 0

Day 3

Group 3: Day 0

503 ± 45* 51.5 ± 5.3 7.27 ± 0.05 26.8 ± 3.0 508 ± 130 None

560 ± 71 50 ± 6 7.27 ± 0.06 23.6 ± 6.2 471 ± 159 None

530 ± 150* 46 ± 13 7.33 ± 0.09 28 ± 6 316 ± 165 None

610 ± 27 49 ± 9 7.29 ± 0.07 19.6 ± 3.2 405 ± 183 None

116 ± 78* 49 ± 4 7.21 ± 0.07 24.2 ± 5.8 446 ± 167 Copious

Note: All values are mean ± standard deviation, measured during unilateral perfusion of the transplanted left lung (Fio2, 1.0; tidal volume, 25 ml/kg; PEEP, 5 em H 20 ; respiratory rate, 12 breaths/min; n = 5 for each group).

Key: mPAP, Mean pulmonary artery. pressure; PVR, pulmonary vascular resistance [(mPAP - PCWP)/COj X 80 dynes· sec· cm? • p < 0.0002; group 3 versus either group I or group 2.

excellent (group 1; 503 ± 45 mm Hg; group 2; 530 ± 150 mm Hg; p value not significant). Oxygenation in both groups improved slightly from day 0 to day 3, as we previously reported in this model.l'' but this improvement did not reach statistical significance in either group. On day 3 arterial P02 generated by the transplanted lung alone was similar in groups 1 and 2 (560 ± 7 i mm Hg vs 610 ± 27 mm Hg, respectively; p not significant). Arterial P0 2 values in both hyperinflated groups were significantly higher than in the "normally" inflated group 30ndayO(arteriaIPo2116 ± 78mmHg;p < O.OOO2for either comparison) (Fig. 2). On day 0, with flow to the transplanted lung alone, the mean pulmonary artery pressure and calculated pulmonary vascular resistance were similar in all groups. All recipients in groups I and 2 were hemodynamically stable. However, all recipients in group 3 were hemodynamically unstable when the transplanted lung alone was perfused, and two of the five recipients in group 3 died of hypoxemia and right-sided heart failure during the initial assessment on day 0, after 8 and 10 minutes of unilateral perfusion of the transplanted lung. Premorbidity hemodynamic and oxygenation data for these dogs are included in Table III. In groups 1 and 2 no pulmonary edema was visible by bronchoscopy in any dog. In group 3 severe pulmonary edema in the transplanted lung was a constant feature in every recipient, beginning 5 to 45 minutes after reperfusion and frothing from the endotracheal tube during unilateral perfusion of the transplanted lung in several animals. All dogs in group 3 that survived initial assessment were killed while under anesthesia on day O. There were no anastomotic technical problems in any dog. In all IO dogs in groups 1 and 2 the transplanted bronchial mucosa appeared grossly pink and healthy, without necrosis or sloughing on day 3. Histologic study after hematoxylineosin staining demonstrated normal-appearing ciliated

.

epithelium in each transplanted bronchus on day 3. The implications of these excellent early histologic results for subsequent long-term bronchial healing remain to be studied.

Discussion Despite several early reports of a significant benefit of inflation of the lungs during pulmonary preservation,4-8, 10, 12-14 this fundamental technical detail received remarkably little attention in the past 15 years. The purpose of this study was to determine whether hyperinflation of donor lungs could improve posttransplant function and to compare this intervention with high-dose PGE, pretreatment of canine pulmonary donors before extended 30-hour hypothermic preservation. Present results with donor hyperinflation. The most dramatic finding in our study is that canine lungs in groups 1 and 2 that were hyperventilated with twice-normal tidal volumes (tidal volume, 25 mIjkg; PEEP, 5 em H20) and were hyperinflated to 30 cm H20 pressure with 100% oxygen before pulmonary artery flush and again before hypothermic storage demonstrated uniformly excellent posttransplant function after a 30-hour preservation period. Lungs in group 3, which were extracted under more routine conditions of ventilation and inflation (tidal volume, 12.5 mIjkg; PEEP, 0 em H20; no hyperinflation; tracheal crossclamping at end-inspiration), functioned poorly after 30-hour storage and allotransplantation, despite high-dose PGE, donor pretreatment. We speculate that our protocol of donor hyperinflation may have improved posttransplant lung function in three possible ways: by facilitating a more effective pulmonary artery flush, by stimulating release of pulmonary surfactant during harvest, and/or by preventing damaging effects of alveolar collapse during prolonged hypothermic storage. Effects of inflation and PGE-l pretreatment on P A

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1 0 8 0 Puskas et at.

ASSESSMENT (TIME) _Group 2

_Group 3

(Fi02 -to; n-5 for each group) Fig. 2. P0 2 of donor and transplanted lungs (p < 0.0002, group 3 vs either group 1 or 2 on day 0). Values are mean ± standard deviation; n = 5 foreach group; Pao2, Arterial oxygen tension during isolated perfusion of transplanted lung alone; Fiaz = 1.0).

flush. The state of lung inflationhas long been known to have a profound influence on pulmonary vascular tone.15, 16 Canine pulmonary lobes perfused ex vivo with hypothermic Euro-Collinssolutionhave a higher pulmonary vascular compliance and significantly lower vascular closure pressure when statically inflated with oxygen than when atelectatic.17 Thus there is theoretical support for the belief that elimination of donor lung atelectasis with large tidal volumes and PEEP and hyperinflation with 100% oxygen before pulmonary artery flush (squeezing blood from the pulmonary vasculature and avoidinghypoxicpulmonaryvasoconstriction) might contribute to a more uniform and thorough pulmonary washout, thus improving pulmonary preservation. However, our present results did not demonstrate reduced pulmonary artery flush pressures, times, or temperatures in the hyperinflated groups. Although there are isolatedreportsto the contrary,18-20 the current consensus in the literature is that prostanoid vasodilation before pulmonary artery flushing is an important component of pulmonary preservation techniques.21-26 PGE I and prostacyclin are believed to

improvelung preservation largely but perhaps not exclusively by their vasodilatory effects.P They also inhibit leukocyte adhesion.F suppress endothelial permeability,28 preventplatelet aggregation.P and havea varietyof poorly understood immunosuppressive and "cytoprotective" effects.l"It is therefore somewhatsurprisingto note that in the present study high-doseboluspretreatment of donors with PGEI did not improve PA flush pressures, times, or end-flush lung temperatures. Furthermore, hyperinflatedlungs in group 1 that were pretreated with PGE t showed no benefitin either PA flush or posttransplant lung functioncompared with hyperinflated lungsin group 2, which received no PGE I. Semi-inflated lungsin group 3 demonstrated uniformly poor preservation, despite PGE I pretreatment of donors in this group and pulmonary artery flush parameters that were similar to those in the hyperinflatedgroups. Thus it seemsthat the principal influence of donor hyperinflation is not reflected in the parameters of pulmonaryartery flushmeasured here and indeed may not be related to improved pulmonary artery flush. Furthermore, the state of inflation ofthe donor lung is so fundamentally important to posttrans-

Volume 104 Number 4 October 1992

plant lung function that the lesser benefit of prostaglandin administration is not demonstrated in the present study. Effect of inflation on pulmonary surfactant. Pulmonary surfactant performs its vital function by decreasing surface tension, promoting alveolar stability, and protecting against pulmonary edema." Release of surfactant from type II pneumonocytes is known to be strongly and rapidly stimulated by hyperinflation of dog.P rabbit,32 and rat 33 lungs and by mechanical stretch of isolated pneumonocytes in culture.l" In addition, even mild respiratory or metabolic alkalosis imposed on excised canine or rat lungs induces secretion of surfactant.35 Thus the effectsof hyperventilation with increased tidal volumes on surfactant release may be due to both alveolar distention and intracellular alkalosis. The former is strongly and the latter is mildly induced in the hyperinflated donors of groups 1 and 2 but not in group 3. It is therefore reasonable to speculate that donor lungs in groups 1 and 2 may have had significantly higher levels of surfactant at the time of extraction than those in group 3, although no measurements of surfactant or surfactant activity were made in any group in the present study. Benefit of hyperinflation during prolonged storage. Alveolar surfactant activity is known to be reduced in the atelectatic lung." and it is possible that apposition of alveolar membranes may inactivate surfactant. Thus maintenance of alveolar volume is a key mechanism in the prevention oflung injury during mechanical ventilation'? and ischemic preservation.v''- 8, 14 Yakeishi and co-workers" first reported an inverse relationship between the surface activity of canine pulmonary extracts and the duration of graft ischemia before transplantation. More recently, Klepetko and colleagues'? reported that the dipalmitoyl-phosphatidylcholine portion of total phosphatidylcholine progressively decreased during ischemic injury to canine lungs. It is reasonable to suppose that preservation techniques that conserve pulmonary surfactant and pulmonary surfactant synthetic capability are likely to provide better posttransplant lung function than those which deplete surfactant or impair surfactant synthesis. High tidal volumes and 5 em H20 PEEP in groups 1 and 2 during open chest ventilationof the donors may significantly avoid repeated alveolarcollapse at end-expiration, thus preserving donor surfactant activity in these groups. Elimination of atelectasis by hyperinflation to 30 em H20 before tracheal crossclamping may significantly conserve pulmonary surfactant during prolonged hypothermic storage. In addition, hyperinflation with 100% oxygen during prolongedischemia may be beneficial by providing oxygen as

Lungpreservation by donor hyperinflation

1 08 1

a metabolic substrate and by limiting the localized hypoxia associated with atelectasis, thereby avoiding both its attendant injury to type II pneumonocytes and hypoxic vasoconstriction. It is interesting to note that in the only previous report of successful 24-hour lung preservation including a vigorous unilateral assessment, Detterbeck and co-workers'f flushed canine lungs with Euro-Collins solution during continuous ventilation with room air (tidal volume not indicated) and then hyperinflated the lungs to 23 to 30 em H 20 pressure with 100% nitrogen gas before storage at 4 0 C for 24 hours. Eight of 12 recipients survived the 12-hour posttransplant assessment in this previous study. Although the authors' conclusions are restricted to the role of oxygen radicals in ischemia-reperfusion injury, their data suggest that static hyperinflation, even with nitrogen gas, is highly beneficial to lung preservation. Presently our clinical lung preservation technique includes donor ventilation with large tidal volumes (20 to 25 nil/kg) and PEEP 5 cm H20. High-dose PGE\ (1000 /-Lg bolus) is administered and lungs are hyperinflated with 100% oxygen to 30 em H20 before pulmonary artery flush with modified Euro-Collins solution and again before hypothermic storage. Posttransplant lung function has generally been excellent. Conclusions. All 10 randomly assigned recipients of hyperinflated canine donor lungs survived the 3-day assessment period; we were able to demonstrate reliably excellent posttransplant function of canine lungs preserved for approximately 30 hours by donor hyperinflation and hypothermic pulmonary artery flush with or without high-dose PGE\ pretreatment. Lungs in the semi-inflated group showed uniformly poor function despite PGE\ administration. We speculate that the beneficial influence of donor hyperinflation may be exerted through a more efficacious pulmonary artery flush as a result of pulmonary vasodilation and avoidance of atelectasis, by increased surfactant release and conservation in donor lungs, and/or by prevention of damaging alveolar collapse during hypothermic storage. We acknowledge the superb technical assistance of J. Mates, S. Diamant, and Y. Wang. Dr. T. K. Waddell provided assistance in statistical analysis. We thank Ethicon Canada Ltd., Peterborough, for supplying the suture material, and Upjohn Canada Ltd., Willowdale,for providingthe PGE 1 for this study. REFERENCES 1. Haverich A, Scott WC, Jamieson SW. Twenty years of lung preservation: a review.Heart Transplantation 1985;4: 234-40. 2. Calhoon JH, Grover FL, Gibbons WJ, et al, Single lung

1 08 2

3.

4.

5.

6.

7.

8.

9.

10.

II.

12. 13. 14.

15.

16.

17.

18.

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transplantation: alternative indications and technique. J THORAC CARDIOVASC SURG 1991;101(5):816-25. Locke TJ, Hooper TL, Flecknell PA, McGregor CGA. Preservation of the lung: comparison of topical cooling and cold crystalloid pulmonary perfusion. J THORAC CARDIOVASC SURG 1988;96:789-95. Homatas J, Bryant L, Eiseman B. Time limits of cadaver lung viability. J THORAC CARDIOVASC SURG 1968;56: 13240. Veith FJ, Sinha SBP, Graves JS, BoleySJ, Dougherty JC. Ischemic tolerance of the lung: the effect of ventilation and inflation. J THORAC CARDIOVASC SURG 1971;61:804-10. 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;62:752-62. Stevens GH, Sanchez MM, Chappell G, Bennett LR, Gyepes MT, Fonkalsrud EW. Prolonged lung-allograft preservation using inbred beagles. J Surg Res 1972;12:24653. Stevens GH, Sanchez MM, Chappell GL. Enhancement of lung preservation by prevention oflung collapse. J Surg Res 1973;14:400-5. Fonkalsrud EW, Sanchez M, Lassaletta L, Smeesters C, Higashijima 1. Extended preservation of the ischemic canine lung by ventilation with PEEP. J Surg Res 1975;18: 437-45. Fonkalsrud E, Sanchez M, Higashijima I, Gyepes M, Arirna E. Evaluation of pulmonary function in the ischemic expanded canine lung. Surg Gynecol Obstet 1976;142:5737. Puskas JD, Cardoso PFG, Mayer E, Shi S-Q, Slutsky AS, Patterson GA. Equivalent eighteen-hour lung preservation with low-potassium dextran or Euro-Collins solution after prostaglandin E, infusion. J THORAC CARDIOVASC SURG 1992;104:83-9. Faridy EE, N aimark A. Effect of distension on metabolism of excised dog lung. J Appl Physiol 1971;31:31-7. Faridy EE. Effect of distension on release of surfactant in excised dogs' lungs. Respir PhysioI1976;27:99-114. Stevens GH, Rangel DM, Yakeishi R, Sanchez MM, Fonkalsrud EW. The relationship of ventilation to preservation of the ischemic canine lung graft. Curr Topics Surg Res 1969;1:51-66. Burton AC, Patel DJ. Effect on pulmonary vascular resistance of inflation of the rabbit lungs. J Appl Physiol 1958;12:239-46. Enjeti S, Terry PB, Menkes HA, Traystman RJ. Mechanical factors and the regulation of perfusion through atelectatic lung in pigs. J Appl Physiol 1982;52:647-54. Unruh H, Hoppensack M, Oppenheimer L. Vascular properties of canine lungs perfused with Euro-collins solution and prostacyclin, Ann Thorac Surg 1990;49:292-8. Bonser RS, Fragomeni LS, Jamieson SW, Kaye MP. Deleterious effects of prostaglandin E, in 12-hour lung preservation. Proc Br Cardiac Soc 1989;61:463.

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19. Hooper TL, Fetherston GJ, Flecknell 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. 20. Novick RJ, Reid KR, Denning L, Duplan J, Menkis AH, McKenzie FN. Prolonged preservation of canine lung allografts: the role of prostaglandins. Ann Thorac Surg 1991;51:853-9. 21. Klepetko W, Muller MR, Khunl-Brady G, et al. Beneficial effect of Iloprost on early pulmonary function after lung preservation with modified Eurocollins solution. Thorac Cardiovasc Surgeon 1989;37:174-9. 22. Hooper TL, Thomson DS, Jones MT, et al. Amelioration of lung ischemic injury with prostacyclin. Transplantation 1990;49:1031-5. 23. Mulvin D, Jones K, Howard R, Grosso M, Repine J. The effect of prostacyclin as a constituent of a preservation solution in protecting lungs from ischemic injury because of its vasodilatory properties. Transplantation 1990;49:82830. 24. Mayer E, Puskas JD, Cardoso PFG, Shi S-Q, Slutsky AS, Patterson GA. Reliable eighteen-hour lung preservation at 4 and 10° C by pulmonary artery flush after high-dose prostaglandin E 1 administration. J THORAC CARDIOVASC SURG 1992;103:1136-42. 25. Jurmann MJ, Dammenhayn L, Schafers H-J, Wahlers T, Fieguth H-G, Haverich A. Prostacyclin as an additive to single crystalloid flush: improved pulmonary preservation in heart-lung transplantation. Transplant Proc 1987;19:41034. 26. Harjula A, Baldwin JC, Shumway NE. Donor deep hypothermia or donor pretreatment with prostaglandin E1 and single pulmonary artery flush for heart-lung graft preservation: an experimental primate study. Ann Thorac Surg 1988;46:553-5. 27. Jones G, Hurley JV. The effect of prostacyclin on the adhesion of leucocytes to injured vascular endothelium. J Pathol1984;142:51-9. 28. Fantone JC, Kunkel SL, Ward PA, Zurier RB. Suppression by prostaglandin E1 of vascular permeability induced by vasoactive inflammatory mediators. J Immunol 1980; 125:2591-6. 29. Moncada S, Flower RJ, Vane JR. Prostaglandins, prostacyclin, and thromboxane A2. In: Goodman AG, Gilman LS, eds. The pharmacological basis of therapeutics. 7th ed. New York: Macmillan, 1985:660-73. 30. Robert A. Cytoprotection by prostaglandins. Gastroenterology 1979;77:761-7. 31. Rooney SA. The surfactant system and lung phospholipid biochemistry. Am Rev Respir Dis 1985;131:439-60. 32. Oyarzun MJ, Clements JA. Control of lung surfactant by ventilation, adrenergic mediators, and prostaglandins in the rabbit. Am Rev Respir Dis 1978;117:879-91. 33. Nicholas TE, Barr HA. Control of release of surfactant phospholipids in the isolated perfused rat lung. J Appl Physiol 1981;51:90-8.

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34. Wirtz HRW, Dobbs LG. Calcium mobilization and exocytosis after one mechanical stretch of lung epithelial cells. Science 1990;250:1260-9. 35. Chander A, Fisher AB. Regulation of lung surfactant secretion. Am J PhysioI1990;258:L241-53. 36. Oyarzun MJ, Stevens P, Clements JA. Effect of lung collapse on alveolar surfactant in rabbits subjected to unilateral pneumothorax. Exp Lung Res 1989;15:909-24. 37. Wyszogrodski I, Kyei-Aboagye K, Taeusch HW Jr, Avery ME. Surfactant inactivation by hyperventilation: conservation by end-expiratory pressure. J Appl PhysioI1975;38: 461-6.

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38. Yakeishi Y, Nozaki M, Randel DM, Stevens GH, Adams FH, Fonkalsrud EW. Effect of allotransplantation of the canine lung on pulmonary surfactant. Surg Gynecol Obstet 1969;128:1264-8. 39. Klepetko W, Lohninger A, Wisser W, et al. Pulmonary surfactant in bronchoalveolar lavage after canine lung transplantation: effect of L-carnitine application. J THORAC CARDIOVASC SURG 1990;99:I048-58. 40. Detterbeck FC, Keagy BA, Paull DE, Wilcox BR. Oxygen free radical scavengers decrease reperfusion injury in lung transplantation. Ann Thorac Surg 1990;50:204-10.