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Successful canine bilateral single-lung transplantation after 21-hour lung preservation
Successful Canine Bilateral Single-Lung Transplantation After 21-Hour Lung Preservation Hiroshi Date, MD, Sadanobu Izumi, MD, Yoshio Miyade, MD, Akio Andou, MD, Nobuyoshi Shirnizu, MD, and Shigeru Teramoto, MD Department of Surgery II, Okayama University Medical School, Okayama, Japan
A canine bilateral single-lung transplantation m o d e l was used to evaluate 21-hour lung preservation with lowpotassium dextran glucose solution. Donor lungs were flushed with low-potassium dextran glucose solution (50 mL/kg), inflated with 100% oxygen (35 mL/kg), and preserved at 8°C. Bilateral single-lung transplantation w a s performed without using cardiopulmonary bypass. The ischemic times to the right and left lungs were designed to be 3 and 6 hours, respectively, in group 1 (n = 5) and 18 and 21 hours in group 2 (n = 6). After bilateral singlequng transplantation, animals were maintained on a ventilator for 12 hours and lung function, including arterial blood gas and pulmonary h e m o d y namics, was measured. All 5 dogs in group 1 and 5 of 6 dogs in group 2 completed bilateral single-lung transplantation successfully and survived for 12 hours with excellent lung function. Arterial oxygen tension and
mean pulmonary artery pressure were stable during the 12-hour assessment period in both groups and did not differ significantly from donor values. T w e l v e hours after reperfusion, mean arterial oxygen tension (inspired oxygen fraction = 1.0) was 590 + 18 m m Hg in group 1 and 604 ± 8 m m Hg in group 2. After the 12-hour assessment period, the animals were extubated and i m m u n o s u p pressed. T w o dogs in group 2 survived for 7 and 8 days, respectively, with a mean arterial oxygen tension of 74 m m Hg on room air at 5 days. These results lead us to conclude that lungs flushed with low-potassium dextran glucose solution, inflated with 100% oxygen, and preserved at 8°C for 21 hours provides excellent lung function in a canine bilateral single-lung transplantation m o d e l in which the animal is totally dependent on the function of transplanted lung tissue.
' u m e r o u s studies on lung preservation have b e e n p u b l i s h e d using ex vivo m o d e l s or in vivo singlelung transplantation models. Most of these m o d e l s are useful to c o m p a r e different p r e s e r v a t i o n conditions. However, the safe preservation time that is applicable for clinical use is difficult to determine. In this study, a canine bilateral single-lung t r a n s p l a n tation (BSLT) m o d e l was u s e d to evaluate 21-hour lung preservation with the m e t h o d that h a d b e e n p r o v e d to provide safe preservation for up to 24 hours in a canine single-lung t r a n s p l a n t a t i o n m o d e l [1]. The postoperative survival of the recipient is totally d e p e n d e n t on the function of t r a n s p l a n t e d lung tissue over the entire postoperative p e r i o d in BSLT a n d therefore attests to the safe p r e s e r v a t i o n time in question.
animals were treated identically except that in group 1, the ischemic times to the right a n d left lungs were d e s i g n e d to be 3 a n d 6 hours, respectively (currently accepted ischemic intervals in h u m a n lung transplantation) [2-4], a n d in group 2, the ischemic times were 18 and 21 hours, respectively. The donors were p r e m e d i c a t e d with s u b c u t a n e o u s atropine sulfate (0.5 rag) a n d ketamine h y d r o c h l o r i d e (20 mg/kg) a n d anesthetized with intravenous thiamylal s o d i u m (15 mg/kg). They t h e n were i n t u b a t e d a n d p l a c e d on a mechanical ventilator using a tidal volume of 20 mL/kg, positive e n d - e x p i r a t o r y pressure of 5 cm H20, a respiratory rate of 15 breaths per minute, a n d an i n s p i r e d oxygen fraction of 1.0. A femoral arterial m o n i toring line was inserted a n d a 5F S w a n - G a n z catheter (Baxter Healthcare Corporation, Edwards Division, Irvine, CA) was p o s i t i o n e d into the m a i n p u l m o n a r y artery t h r o u g h the femoral vein. Systemic, p u l m o n a r y artery, a n d central venous pressures were recorded. Cardiac o u t p u t was d e t e r m i n e d in triplicate b y the t h e r m o d i l u tion method. Arterial b l o o d gas analysis was made. After the a s s e s s m e n t of donor lung a n d cardiac function, m e d i a n s t e r n o t o m y was made. The d o n o r lung excision was p e r f o r m e d b y m e a n s of previously described techniques [5l. Before the excision, the tidal volume was increased to 35 m L / k g and the positive e n d - e x p i r a t o r y p r e s s u r e was decreased to 0 cm H20. Both d o n o r lungs were then flushed in situ with low-
N
Material and Methods Eleven bilateral single-lung allotransplantation procedures were p e r f o r m e d in w e i g h t - m a t c h e d pairs of m o n grel dogs (7.8 to 17.5 kg). The dogs were a s s i g n e d randomly to one of the two study groups. The m e a n weights of donor and recipient were 12.4 ± 0.6 kg and 13.4 ± 1.2 kg, respectively, in group 1 (n - 5) a n d 13.6 + 1.9 kg a n d 13.6 ± 1.7 kg, respectively, in group 2 (n = 6). The Accepted for publication Sep 13, 1994. Address reprint requests to Dr Date, Department of Surgery II, Okayama University Medical School,2-$-1 Shikata cho, Okayama 700, Japan. © 1995 by The Society of Thoracic Surgeons
(Ann Thorac Surg 1995;59:336-41)
0003-4975/95/$9.50 0003-4975(94)00817-Q
A n n Thorac S u r g 1995;59:336-41
p o t a s s i u m dextran glucose solution [1] (4°C, 50 mL/kg) by m e a n s of a cannula placed in the m a i n p u l m o n a r y artery while the flushing pressure was continuously m o n i t o r e d from a side arm of the cannula. Simultaneous topical cooling was achieved by i m m e r s i n g the lungs in cold saline (1 ° to 4°C). At the completion of the flush, the trachea was stapled, leaving the lungs well-inflated with 100% oxygen (35 mL/kg). The d o u b l e - l u n g block was excised and placed in a sterile plastic b a g containing cold l o w - p o t a s s i u m dextran glucose solution, then p r e s e r v e d at 8°C for a d e s i g n e d preservation period. The recipient animals were sedated, anesthetized, intubated, a n d ventilated as were the donors, with the exception that anesthesia was m a i n t a i n e d d u r i n g the s u b s e q u e n t p r o c e d u r e with a 40:60 mixture of nitrous oxide/oxygen and 0.5% to 1.0% halothane. Percutaneous insertion of a femoral artery catheter a n d a p u l m o n a r y artery catheter (5F S w a n - G a n z catheter) t h r o u g h the femoral vein was then p e r f o r m e d for monitoring d u r i n g the procedure. W i t h the animals in the left decubitus position, the right p n e u m o n e c t o m y was p e r f o r m e d t h r o u g h a lateral thoracotomy in the right fifth intercostal space. The interatrial groove was dissected to create a left atrial cuff for s u b s e q u e n t anastomosis. On a separate surgical table, the right a n d left donor lungs were s e p a r a t e d a n d prep a r e d for implantation. Because the right lung was imp l a n t e d first, the left lung was r e t u r n e d to 8°C storage until it was r e q u i r e d for implantation. The right lung i m p l a n t a t i o n was p e r f o r m e d with the o r d e r of anastomoses as follows: left atrium, p u l m o n a r y artery, bronchus. A chest drain was inserted and the chest was closed. The recipient dog then was t u r n e d from the left to right lateral decubitus position, and the left lung transplantation was p e r f o r m e d in essentially the same fashion as was right lung transplantation. Because c a r d i o p u l m o n a r y b y p a s s was not u s e d in this study, the recipient was totally d e p e n d e n t on the right t r a n s p l a n t e d lung during the left lung implantation. After closure of the left chest, the recipient animals were p l a c e d in the spine position a n d m a i n t a i n e d on a ventilator for 12 hours, during which time arterial b l o o d gas analysis and full h e m o d y namic a s s e s s m e n t (systemic, p u l m o n a r y , a n d central venous pressures, along with cardiac output) were repeatedly m a d e at intervals with the same setting of the ventilator as for the donor assessment. After the 12-hour p e r i o d of p o s t t r a n s p l a n t a t i o n assessment, they were w e a n e d from the ventilator s u p p o r t a n d the chest tubes were removed. Once the animals showed satisfactory s p o n t a n e o u s ventilation, they were extubated. The surviving recipients received FK506 (0.1 mg/kg) intramuscularly a n d p r e d n i s o n e (0.5 mg/kg) orally every day for i m m u n o s u p p r e s s i o n . Penicillin G (1,200,000 U) a n d gentamicin (40 rag) were given intramuscularly every day. Arterial blood gases on r o o m air a n d chest r o e n t g e n o g r a m s were o b t a i n e d daily, a n d suspected rejection was treated with 250 m g of intravenous methylprednisolone. After death of each recipient, the transplanted lungs were examined macroscopically and histologically.
DATE ET AL 2 1 - H O U R L U N G PRESERVATION
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All results are p r e s e n t e d as the m e a n ± 1 s t a n d a r d
error of the mean. O n e - w a y analysis of variance with r e p e a t e d m e a s u r e s was u s e d to d e t e r m i n e w h e t h e r an overall difference existed in lung function b e t w e e n the two groups during the a s s e s s m e n t period. W h e n a difference was obtained, contrast was p e r f o r m e d to determ i n e w h e r e significant differences arose. Paired Stud e n t ' s t test was u s e d to compare the results of donor a n d recipient. Statistical significance was accepted at the 95% confidence level, p less than 0.05. All animals received h u m a n e care in compliance with the "Principles of Laboratory A n i m a l C a r e " f o r m u l a t e d by the National Society for Medical Research, a n d the " G u i d e for the Care a n d Use of Laboratory A n i m a l s " p u b l i s h e d by the National Institutes of Health (NIH Publication 85-23, revised 1985).
Results For the two groups, the flushing time (group 1, 95 + 14; group 2, 92 ± 8 seconds), flushing p r e s s u r e (23.0 - 1.1 a n d 20.8 ± 1.4 m m Hg), excision time (6.6 -- 0.3 a n d 7.6 _+ 0.8 minutes), right lung i m p l a n t a t i o n time (66.6 -- 4.8 a n d 60.8 _+ 2.3 minutes), a n d left lung implantation time (64.6 _+ 4.1 a n d 58.0 ± 2.9 minutes) were similar (p = not significant). In group 1, the m e a n ischemic time of the right lung was 3 hours, 9 minutes ± 28 minutes, and for the left lung it was 6 hours, 2 minutes _+ 33 minutes. In group 2, they were 18 hours, 11 m i n u t e s ± 28 minutes a n d 21 hours, 6 minutes ± 21 minutes, respectively. All 5 dogs (100%) in group 1 h a d successful BSLT without c a r d i o p u l m o n a r y bypass. Five of 6 dogs (83%) in group 2 c o m p l e t e d BSLT successfully; 1 dog d i e d of lung e d e m a during the left lung transplantation. Results from the 5 operative survivors in each group form the basis of this report.
Lung Function During the 12-hour Assessment Period All 5 of the operative survivors in each group c o m p l e t e d the 12-hour a s s e s s m e n t with excellent lung function. The results of gas exchange a n d h e m o d y n a m i c s of the donor animals a n d surviving recipients d u r i n g the 12-hour a s s e s s m e n t p e r i o d are shown in Table 1. Arterial oxygen tension (PaO2) was not different b e t w e e n the two groups except at 6 hours a n d did not differ significantly from the donor value in both groups. Arterial carbon dioxide tension (PaCO2) was stable in group 1, but it increased significantly in group 2 after 2 hours of reperfusion. However, PaCO 2 was not significantly different b e t w e e n the two groups except at 6 hours. M e a n p u l m o n a r y artery p r e s s u r e a n d m e a n central venous p r e s s u r e were stable during the a s s e s s m e n t p e r i o d in both groups and did not differ significantly from the donor values. M e a n arterial pressure a n d cardiac o u t p u t were significantly lower in recipient than in donor; however, both m A P a n d CO were stable d u r i n g the a s s e s s m e n t p e r i o d in b o t h groups.
Results After Extubation All 5 animals in each group s h o w e d satisfactory spontan e o u s ventilation a n d were r e t u r n e d to the cage. Survival
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DATE ET AL 21-HOUR LUNG PRESERVATION
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Table 1. Assessment of Lung and Cardiac Function of Donor and Recipient ~ Function Indicator P a O 2 ( m m Hg) Group 1 Group 2 P a C O 2 ( m m Hg) Group 1 Group 2 m A P (ram Hg) Group 1 Group 2 m P A P (ram Hg) Group 1 Group2 m C V P (ram Hg) Group 1 Group 2 C O (L/rain) Group 1 Group 2
Recipient Donor
1 Hour
2 Hours
4 Hours
6 Hours
611 ÷ 24 629 + 24
538 ± 32 623 ± 32
563 + 35 624 ± 35
559 + 16 605 -+ 16
539 ~ 13 604 Z 13 b
43 + 6 35 ± 6
44 _+ 5 43 ± 5
46 _+ 5 45 _+ 5 c
41 ± 6 51 ± 6 c
39 ± 4 51 z 4 bc
146 _ 9 152 ± 9
112 _+ 4 c 106 + 4 c
120 _+ 6 117 + 6 c
114 ± 10 130 + 10
25 + 3 26+3
27 _+ 4 23+4
27 ~ 3 22_+3
4---1 7±1
4+1 7+1
4±1 5+1
2.4 ± 0.4 2.3 ± 0.4
1.2 + 0.1 c 1.3 -+ 0.1 ~
All values are mean - standard error of the mean.
1.3 -+ 0.2 c 1.2 ± 0.2 c
10 H o u r s
12 H o u r s
528 -- 29 612 -+ 29
569 _+ 20 612 -+ 20
590 + 18 604 -+ 17
40 + 4 50 + 4 c
44 + 5 51 + 5 ~
44 ÷ 4 47 ± 4 ¢
109 ± 8 127 ± 8
95 _+ 8 c 122 + 8 ~
94 _+ 11 122 -+ 11 c
90 ÷ 12 120 -+ 12 c
27 _+ 3 22_+3
27 ~ 3 20z3
27 ± 3 21 ± 3
27 ± 3 20_+3
27 + 3 20±3
4±1 5+1
5±1 5±1
5+1 6+1
5+1 6+1
5-~1 6-+1
1.1 + 0.1 ~ 1.1 ± 0.1 c
1.2 ± 0.2 ~ 1.1 -+ 0.2 ~
b p < 0.05 (group l versus group 2).
8 Hours
1.1 -+ 0.1" 1.1 _+ 0.1 ~
Comment
In the present evaluate the
1.3 ± 0.2 ~ 1.3 -+ 0.2 ~
c p < 0.05 (versus Donor).
CO = cardiac output; mAP mean arterial pressure; mCVP = mean central venous pressure; pressure; PaCO2 - arterial carbon dioxide tension; PaO 2 - arterial oxygen tension.
p e r i o d a n d c a u s e s o f d e a t h a r e s h o w n i n T a b l e 2. T w o dogs in group 1 and 3 dogs in group 2 died of unknown causes within 2 days of operation. In these 5 dogs, postmortem examination of the lungs did not reveal any overt signs of lung injury macroscopically or histologic a l l y (Fig 1). T h e l o n g e s t s u r v i v a l t i m e w a s 4 d a y s i n g r o u p I a n d 8 d a y s i n g r o u p 2. T h e 2 d o g s i n g r o u p 2 t h a t survived more than a week showed clear chest roentgeno g r a m s (Fig 2) w i t h o u t p u l m o n a r y i n f i l t r a t i o n o r p l e u r a l e f f u s i o n , a n d g o o d b l o o d g a s e s (Fig 3) f o r 5 d a y s d e s p i t e slightly reduced respiratory rates.
1.2 -+ 0.2 c 1.2 -"- 0.2 ~
mPAP - mean pulmonary arterial
m e t h o d , w h i c h h a s b e e n p r o v e d to p r o v i d e s a f e p r e s e r v a t i o n f o r u p to 24 h o u r s i n a c a n i n e s i n g l e - l u n g t r a n s plantation model. The BSLT model was used for the f o l l o w i n g r e a s o n s . First, B S L T h a s b e c o m e a s t a n d a r d p r o c e d u r e to r e p l a c e b o t h l u n g s a n d i t s a p p l i c a t i o n is b e i n g w i d e n e d to s e v e r a l e n d - s t a g e l u n g d i s e a s e s i n c l u d ing emphysema, obliterative bronchiolitis, infectious lung diseases such as cystic fibrosis, and possibly pulmonary hypertension [2-4, 6-8]. Second, the need for extending the period of safe preservation becomes more important for this procedure because the ischemic time o f t h e l u n g t r a n s p l a n t e d s e c o n d is u s u a l l y 2 to 3 h o u r s l o n g e r t h a n t h a t o f t h e l u n g t r a n s p l a n t e d first. It s h o u l d
s t u d y , a c a n i n e B S L T m o d e l w a s u s e d to already-established lung preservation
Table 2. Survival Period and Cause of Death After Extubation Group/No.
Survival Period
C a u s e of D e a t h
1 (n = 5)
l 2 3 4 5 2 (n - 6) 1 2 3 4 5 6
3 18 2 2 4
h h days days days
0h 6h 12 h 2 days 7 days 8 days
Pneumothorax Pneumothorax Unknown Unknown Rejection Lung edema Unknown Unknown Unknown Rejection Bronchial d e h i s c e n c e
Fig 1. Photomicrograph qf the lung allograft of a dog in group 2 that died of unknown cause 12 hours after extubahon. No overt sign of lung injury was seen. (Hematoxylin and eosin; original magnification, ×100.)
Ann Thorac Surg 1995;59:336-41
Fig 2. Chest roentgenogram of a recipient in group 2 3 days after bilateral single lung transplantation. No signiyicant abnormalities are seen in lungs.
also be noted that BSLT is often required for patients with infectious lung diseases and posttransplantation graft failure; in such cases severe pleural and mediastinal adhesion often prolongs operation time. Third, the transplanted lung function can be measured under physiologic condition in a BLT model, whereas it is measured under unphysiologic conditions in a single-lung transplantation model because some additional manipulation such as contralateral pulmonary artery occlusion becomes necessary to evaluate solely the function of the transplanted graft I1, 5]. Fourth, we think the BSLT model is better than the single-lung transplantation model for determining the safe preservation time of a particular preservation method, because the animal is totally dependent on the function of transplanted lung tissue over the entire postoperative period. In the single-lung transplantation model, with temporary occlusion of the contralateral pulmonary artery for assessment of the transplanted lung the native lung would act as a reservoir protecting the transplanted lung between the assessment. We maintained the animal on a ventilator for 12 hours after BSLT and focused on the immediate graft function, as this period reflects the effects of preservation without any superimposed effects of rejection or infection. Five of 6 dogs (83%) in the 21-hour preservation group survived the BSLT procedure and showed excellent PaO z and stable pulmonary hemodynamics throughout the 12hour assessment period. In particular, mean PaO2 (the gold standard in terms of lung preservation quality) [9] of the 5 survivors was 604 ± 8 m m Hg at 12 hours. We lost 1 dog because of severe lung edema during the left lung implantation. However, none of the other 5 dogs showed
DATE ET AL 21-HOUR LUNG PRESERVATION
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PaO2 levels of less than 550 m m Hg during the entire assessment period. It is difficult to explain why this large difference occurred in the same group. We suspect that we made an undetectable technical mistake in this particular 1 animal experiment. A significant increase of PaCO 2 was observed in the 21-hour preservation group. Because the PaCO 2 was measured with a fixed respiratory setting, the increase in PaCO 2 represented the decrease of transplanted lung compliance. However, the decrease of lung compliance did not seem to be fatal as the survivors showed normal PaCO2 after extubation. Despite the fact that several parameters suggested excellent early graft function, the survival of the animals after extubation was modest. It is well k n o w n that dogs can rarely survive bilateral lung transplantation [10, 11] because of the dependence of their respiratory control on vagal innervation [12]. It is for this reason that primates have been used for heart-lung [13] and bilateral lung [14] experiments. About half of the dogs in this experiment died of u n k n o w n causes in an early postoperative period without any overt signs of lung injury macroscopically or histologically. We suspect that causes of death in these animals were related not to poor lung preservation, but rather to other factors such as extensive magnitude of
Pa02
I00 80 6O -r
E E
40
20 0 40
PaC02
30 -r E E
20 I0 0 2O
E
15
r: oi
I0
E
5 0
I
1
I
I
I
I
I
1
1
2
3
4
5
6
7
8
POST- OP (days) Fig 3. Arterial oxygen tension (PaO 2) on roonl air, arterial carbon dioxide tension (PaCO2), and respiratory rate (RR) of 2 recipients in group 2 after exh~bafion. The 2 dogs survived for 7 and 8 days, respectively.
340
DATEET AL 21-HOUR LUNG PRESERVATION
operation, effects of denervation, a n d p r o l o n g e d anesthesia (over 18 hours) because of the postoperative assessment. Survivors after extubation s h o w e d a s t e r e o t y p e d deep a n d slow respiratory p a t t e r n with a forceful expiratory effort due to the absence of reflexes n o r m a l l y originating in the lungs. However, we were fortunate to have 2 animals in the 21-hour preservation group survive m o r e than a week, which allowed us to m e a s u r e the graft function further. These 2 animals s h o w e d good arterial b l o o d gases on r o o m air until death, with a m e a n PaO 2 of 74 m m H g a n d PaCO 2 of 35.9 m m Hg, respectively, at 5 days. Although the survival rate was relatively low, these results s u g g e s t e d that the p r e s e n t preservation m e t h o d could provide good long-term graft function. The lung is the only organ that can be p r e s e r v e d with a r e a d y s u p p l y of oxygen t h r o u g h the airway. It has been d e m o n s t r a t e d that lung cells are able to maintain aerobic m e t a b o l i s m utilizing the oxygen in the alveoli [15]. Based u p o n previous studies, our basic strategy for lung preservation was to maintain a m i n i m u m a n d optimal level of aerobic metabolism. For this reason, the p r e s e n t m e t h o d consisted of three i m p o r t a n t elements: preservation solution (low-potassium dextrose glucose), inflation gas (100% oxygen 35 mL/kg), a n d preservation t e m p e r a t u r e (8°C). L o w - p o t a s s i u m dextran glucose solution is an extracellular fluid-type solution that contains p h o s p h a t e buffer, glucose, a n d dextran. Several investigators have r e p o r t e d extracellular fluid-type solution to be s u p e r i o r to intracellular fluid-type solution for lung preservation [16, 17], although Puskas a n d co-workers [18] r e p o r t e d that there was no difference w h e n p r o s t a g l a n d i n E 1 was administ e r e d before p u l m o n a r y artery flush. A high concentration of p h o s p h a t e buffer w o u l d show effective buffer action for carbon dioxide p r o d u c e d as a p r o d u c t of oxygen consumed. Glucose in the preservation solution is actively m e t a b o l i z e d in the glycolytic p a t h w a y as well as in the citric acid cycle, a n d it improves lung preservation [1]. Dextran w o u l d function as an oncotic agent, t e n d i n g to k e e p water in the intravascular c o m p a r t m e n t , t h e r e b y decreasing interstitial e d e m a formation [19]. The oxygen concentration in the inflation gas a n d the degree of inflation are very important. W e d e r a n d coworkers [20] r e p o r t e d that preservation with 100% oxygen inflation a p p e a r e d superior to inflation with room air a n d much superior to inflation with 100% nitrogen. There is recent evidence that the uses of large tidal volume during harvesting and hyperinflation during preservation provide superior preservation, although the mechanism of the beneficial effect has not been clearly demonstrated yet [21, 22]. Lungs were ventilated and hyperinflated with 100% oxygen at a volume of 35 mL/kg in the present study. O p t i m a l t e m p e r a t u r e for lung preservation has b e e n d e m o n s t r a t e d to be in the vicinity of 10°C [5, 23]. W e p r e s e r v e d lungs at 8°C in the p r e s e n t study because we thought that metabolic rate was too fast at 10°C w h e n the preservation time was m o r e than 24 hours, according to the analysis of metabolites in the p r e s e r v e d lung tissue ( u n p u b l i s h e d data). N a k a m o t o a n d co-workers [24] re-
Ann Thorac Surg 1995;59:336-41
p o r t e d optimal t e m p e r a t u r e to be at 8 ° to 9°C in a rabbit lung model. W e recognize that other m e t h o d s of preservation [16, 21, 25] m a y be able to accomplish the s a m e goal, a n d believe that the importance of this work is the d e m o n stration that consistent, excellent, 21-hour lung preservation is achievable.
We gratefully acknowledge the advice received from Dr Joel D. Cooper, Barnes Hospital, St. Louis, MO. We are grateful to Tetsuo Kawakami for his expert technical assistance.
References 1. Date H, Matsumura A, Manchester JK, et al. Evaluation of lung metabolism during successful twenty-four-hour canine lung preservation. J Thorac Cardiovasc Surg 1993;105: 480 -91. 2. Kaiser LR, Pasque MK, Trulock EP, Low DE, Dresler CM, Cooper JD. Bilateral sequential lung transplantation: the procedure of choice for double-lung replacement. Ann Thorac Surg 1991;52:438-46. 3. Ramirez JC, Patterson GA, Winton TL, et al. Bilateral lung transplantation for cystic fibrosis. J Thorac Cardiovasc Surg 1992;103:287-94. 4. Low DE, Trulock EP, Kaiser LR, et al. Morbidity, mortality, and early results of single versus bilateral lung transplantation for emphysema. J Thorac Cardiovasc Surg 1992;103: 1119 -26. 5. Date H, Lima O, Matsumura A, Tsuji H, d'Avignon DA, Cooper JD. In a canine model, lung preservation at 10°C is superior to that at 4°C: a comparison of two preservation temperatures on lung function and on adenosine triphosphate level measured by phosphorous 31-nuclear magnetic resonance. J Thorac Cardiovasc Surg 1992;103:773-80. 6. 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. 7. Shennib H, Noirclerc M, Ernst P, et al. Double-lung transplantation for cystic fibrosis. Ann Thorac Surg 1992;54:27-32. 8. Bando K, Keenan RJ, Paradis IL, et al. Current results and indications of single, bilateral and heart and lung transplantation for pulmonary hypertension. Presented at the Seventy-third Annual Meeting of the American Association for Thoracic Surgery, Chicago, IL, April 25-28, 1993. 9. Haverich A, Scott WC, Jamieson SW. Twenty years of lung preservation: a review. J Heart Transplant 1985;4:234-40. 10. Alican F, Cayirli M, Isin E, Hardy JD. One-stage replantation of both lungs in the dog. JAMA 1971;215:1301-6. 11. Fujimura S, Parmley WW, Tomoda H, Norman J, Matloff M. Hemodynamic alterations after staged and simultaneous bilateral lung autotransplantation in dogs: follow-up studies. J Thorac Cardiovasc Surg 1972;63:937-44. 12. Nakae S, Webb WR, Theodorides T, Sugg WL. Respiratory function following cardiopulmonary denervation in dogs, cat, and monkey. Surg Gynecol Obstet 1967;25:1285-92. 13. Reitz BA, Burton NA, Jamieson SW, et al. Heart and lung transplantation: autotransplantation and allotransplantation in primates with extended survival. J Thorac Cardiovasc Surg 1980;80:360-72. 14. Sundaresan S, Lima O, Date H, et al. A primate model of sequential bilateral lung transplantation (BLT) to evaluate lung preservation employing low potassium dextran ("LPD") solution. Ann Thorac Surg 1993;56:1129-35. 15. Date H, Matsumura A, Manchester JK, Cooper JM, Lowry OH, Cooper JD. Changes in alveolar oxygen and carbon
Ann Thorac Surg 1995;59:336-41
16.
17.
18.
19.
20.
dioxide concentration and oxygen consumption during lung preservation: the maintenance of aerobic metabolism during lung preservation. J Thorac Cardiovasc Surg 1993;105: 492-501. Fujimura S, Handa M, Kondo T, Ichinose T, Shiraishi Y, Nakata T. Successful 48-hour simple hypothermic preservation of canine lung transplants. Transplant Proe 1987;19: 1334-6. Yamazaki F, Yokomise H, Keshavjee SH, et al. The superiority on an extracellular fluid solution over Euro-Collins' solution for pulmonary preservation. Transplantation 1990; 49:690-4. Puskas JD, Cardoso PFG, Mayer E, Shi S, Slutsky AS, Patterson GA. Equivalent eighteen-hour lung preservation with low-potassium dextran or Euro-Collins solution after prostaglandin E~ infusion. J Thorac Cardiovasc Surg 1992; 104:83-9. Keshavjee SH, Yamazaki F, Yokomise H, et al. The role of dextran 40 and potassium in extended hypothermic lung preservation for lung transplantation. J Thorac Cardiovasc Surg 1992;103:314-25. Weder W, Harper B, Shimokawa S, et al. Influence of
DATE ET AL 21-HOUR LUNG PRESERVATION
21.
22.
23.
24. 25.
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intraalveolar oxygen concentration on lung preservation in a rabbit model. J Thorac Cardiovasc Surg 1991;101:1037-43. Puskas JD, Hirai T, Christie N, Mayer E, Slutsky AS, Patterson GA. Reliable thirty-hour lung preservation by donor lung hyperinflation. J Thorac Cardiovasc Surg 1992;104: 1075-83. Aoe M, Trachiotis GD, Park CK, Nakajima S, Cooper JD, Patterson GA. The effects of hyperinflation during storage in lung transplantation. Presented at the International Conference of the American Thoracic Society, Miami Beach, FL, May 17-20, 1992. Wang LS, Yoshikawa K, Miyoshi S, et al. The effect of ischemic time and temperature on lung preservation in a simple ex vivo rabbit model used for functional assessment. J Thorac Cardiovasc Surg 1989;98:333-42. Nakamoto K, Maeda M, Taniguchi K, Tsubota N, Kawashima Y. A study on optimal temperature for isolated lung preservation. Ann Thorac Surg 1992;53:101-8. Shueler S, De Valeria PA, Hatanaka M, et al. Successful twenty-four-hour lung preservation with donor core cooling and leukocyte depletion in an orthotopic double lung transplantation model. J Thorac Cardiovasc Surg 1992;104:73-82.
A canine bilateral single-lung transplantation m o d e l was used to evaluate 21-hour lung preservation with lowpotassium dextran glucose solution. Donor lungs were flushed with low-potassium dextran glucose solution (50 mL/kg), inflated with 100% oxygen (35 mL/kg), and preserved at 8°C. Bilateral single-lung transplantation w a s performed without using cardiopulmonary bypass. The ischemic times to the right and left lungs were designed to be 3 and 6 hours, respectively, in group 1 (n = 5) and 18 and 21 hours in group 2 (n = 6). After bilateral singlequng transplantation, animals were maintained on a ventilator for 12 hours and lung function, including arterial blood gas and pulmonary h e m o d y namics, was measured. All 5 dogs in group 1 and 5 of 6 dogs in group 2 completed bilateral single-lung transplantation successfully and survived for 12 hours with excellent lung function. Arterial oxygen tension and
mean pulmonary artery pressure were stable during the 12-hour assessment period in both groups and did not differ significantly from donor values. T w e l v e hours after reperfusion, mean arterial oxygen tension (inspired oxygen fraction = 1.0) was 590 + 18 m m Hg in group 1 and 604 ± 8 m m Hg in group 2. After the 12-hour assessment period, the animals were extubated and i m m u n o s u p pressed. T w o dogs in group 2 survived for 7 and 8 days, respectively, with a mean arterial oxygen tension of 74 m m Hg on room air at 5 days. These results lead us to conclude that lungs flushed with low-potassium dextran glucose solution, inflated with 100% oxygen, and preserved at 8°C for 21 hours provides excellent lung function in a canine bilateral single-lung transplantation m o d e l in which the animal is totally dependent on the function of transplanted lung tissue.
' u m e r o u s studies on lung preservation have b e e n p u b l i s h e d using ex vivo m o d e l s or in vivo singlelung transplantation models. Most of these m o d e l s are useful to c o m p a r e different p r e s e r v a t i o n conditions. However, the safe preservation time that is applicable for clinical use is difficult to determine. In this study, a canine bilateral single-lung t r a n s p l a n tation (BSLT) m o d e l was u s e d to evaluate 21-hour lung preservation with the m e t h o d that h a d b e e n p r o v e d to provide safe preservation for up to 24 hours in a canine single-lung t r a n s p l a n t a t i o n m o d e l [1]. The postoperative survival of the recipient is totally d e p e n d e n t on the function of t r a n s p l a n t e d lung tissue over the entire postoperative p e r i o d in BSLT a n d therefore attests to the safe p r e s e r v a t i o n time in question.
animals were treated identically except that in group 1, the ischemic times to the right a n d left lungs were d e s i g n e d to be 3 a n d 6 hours, respectively (currently accepted ischemic intervals in h u m a n lung transplantation) [2-4], a n d in group 2, the ischemic times were 18 and 21 hours, respectively. The donors were p r e m e d i c a t e d with s u b c u t a n e o u s atropine sulfate (0.5 rag) a n d ketamine h y d r o c h l o r i d e (20 mg/kg) a n d anesthetized with intravenous thiamylal s o d i u m (15 mg/kg). They t h e n were i n t u b a t e d a n d p l a c e d on a mechanical ventilator using a tidal volume of 20 mL/kg, positive e n d - e x p i r a t o r y pressure of 5 cm H20, a respiratory rate of 15 breaths per minute, a n d an i n s p i r e d oxygen fraction of 1.0. A femoral arterial m o n i toring line was inserted a n d a 5F S w a n - G a n z catheter (Baxter Healthcare Corporation, Edwards Division, Irvine, CA) was p o s i t i o n e d into the m a i n p u l m o n a r y artery t h r o u g h the femoral vein. Systemic, p u l m o n a r y artery, a n d central venous pressures were recorded. Cardiac o u t p u t was d e t e r m i n e d in triplicate b y the t h e r m o d i l u tion method. Arterial b l o o d gas analysis was made. After the a s s e s s m e n t of donor lung a n d cardiac function, m e d i a n s t e r n o t o m y was made. The d o n o r lung excision was p e r f o r m e d b y m e a n s of previously described techniques [5l. Before the excision, the tidal volume was increased to 35 m L / k g and the positive e n d - e x p i r a t o r y p r e s s u r e was decreased to 0 cm H20. Both d o n o r lungs were then flushed in situ with low-
N
Material and Methods Eleven bilateral single-lung allotransplantation procedures were p e r f o r m e d in w e i g h t - m a t c h e d pairs of m o n grel dogs (7.8 to 17.5 kg). The dogs were a s s i g n e d randomly to one of the two study groups. The m e a n weights of donor and recipient were 12.4 ± 0.6 kg and 13.4 ± 1.2 kg, respectively, in group 1 (n - 5) a n d 13.6 + 1.9 kg a n d 13.6 ± 1.7 kg, respectively, in group 2 (n = 6). The Accepted for publication Sep 13, 1994. Address reprint requests to Dr Date, Department of Surgery II, Okayama University Medical School,2-$-1 Shikata cho, Okayama 700, Japan. © 1995 by The Society of Thoracic Surgeons
(Ann Thorac Surg 1995;59:336-41)
0003-4975/95/$9.50 0003-4975(94)00817-Q
A n n Thorac S u r g 1995;59:336-41
p o t a s s i u m dextran glucose solution [1] (4°C, 50 mL/kg) by m e a n s of a cannula placed in the m a i n p u l m o n a r y artery while the flushing pressure was continuously m o n i t o r e d from a side arm of the cannula. Simultaneous topical cooling was achieved by i m m e r s i n g the lungs in cold saline (1 ° to 4°C). At the completion of the flush, the trachea was stapled, leaving the lungs well-inflated with 100% oxygen (35 mL/kg). The d o u b l e - l u n g block was excised and placed in a sterile plastic b a g containing cold l o w - p o t a s s i u m dextran glucose solution, then p r e s e r v e d at 8°C for a d e s i g n e d preservation period. The recipient animals were sedated, anesthetized, intubated, a n d ventilated as were the donors, with the exception that anesthesia was m a i n t a i n e d d u r i n g the s u b s e q u e n t p r o c e d u r e with a 40:60 mixture of nitrous oxide/oxygen and 0.5% to 1.0% halothane. Percutaneous insertion of a femoral artery catheter a n d a p u l m o n a r y artery catheter (5F S w a n - G a n z catheter) t h r o u g h the femoral vein was then p e r f o r m e d for monitoring d u r i n g the procedure. W i t h the animals in the left decubitus position, the right p n e u m o n e c t o m y was p e r f o r m e d t h r o u g h a lateral thoracotomy in the right fifth intercostal space. The interatrial groove was dissected to create a left atrial cuff for s u b s e q u e n t anastomosis. On a separate surgical table, the right a n d left donor lungs were s e p a r a t e d a n d prep a r e d for implantation. Because the right lung was imp l a n t e d first, the left lung was r e t u r n e d to 8°C storage until it was r e q u i r e d for implantation. The right lung i m p l a n t a t i o n was p e r f o r m e d with the o r d e r of anastomoses as follows: left atrium, p u l m o n a r y artery, bronchus. A chest drain was inserted and the chest was closed. The recipient dog then was t u r n e d from the left to right lateral decubitus position, and the left lung transplantation was p e r f o r m e d in essentially the same fashion as was right lung transplantation. Because c a r d i o p u l m o n a r y b y p a s s was not u s e d in this study, the recipient was totally d e p e n d e n t on the right t r a n s p l a n t e d lung during the left lung implantation. After closure of the left chest, the recipient animals were p l a c e d in the spine position a n d m a i n t a i n e d on a ventilator for 12 hours, during which time arterial b l o o d gas analysis and full h e m o d y namic a s s e s s m e n t (systemic, p u l m o n a r y , a n d central venous pressures, along with cardiac output) were repeatedly m a d e at intervals with the same setting of the ventilator as for the donor assessment. After the 12-hour p e r i o d of p o s t t r a n s p l a n t a t i o n assessment, they were w e a n e d from the ventilator s u p p o r t a n d the chest tubes were removed. Once the animals showed satisfactory s p o n t a n e o u s ventilation, they were extubated. The surviving recipients received FK506 (0.1 mg/kg) intramuscularly a n d p r e d n i s o n e (0.5 mg/kg) orally every day for i m m u n o s u p p r e s s i o n . Penicillin G (1,200,000 U) a n d gentamicin (40 rag) were given intramuscularly every day. Arterial blood gases on r o o m air a n d chest r o e n t g e n o g r a m s were o b t a i n e d daily, a n d suspected rejection was treated with 250 m g of intravenous methylprednisolone. After death of each recipient, the transplanted lungs were examined macroscopically and histologically.
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All results are p r e s e n t e d as the m e a n ± 1 s t a n d a r d
error of the mean. O n e - w a y analysis of variance with r e p e a t e d m e a s u r e s was u s e d to d e t e r m i n e w h e t h e r an overall difference existed in lung function b e t w e e n the two groups during the a s s e s s m e n t period. W h e n a difference was obtained, contrast was p e r f o r m e d to determ i n e w h e r e significant differences arose. Paired Stud e n t ' s t test was u s e d to compare the results of donor a n d recipient. Statistical significance was accepted at the 95% confidence level, p less than 0.05. All animals received h u m a n e care in compliance with the "Principles of Laboratory A n i m a l C a r e " f o r m u l a t e d by the National Society for Medical Research, a n d the " G u i d e for the Care a n d Use of Laboratory A n i m a l s " p u b l i s h e d by the National Institutes of Health (NIH Publication 85-23, revised 1985).
Results For the two groups, the flushing time (group 1, 95 + 14; group 2, 92 ± 8 seconds), flushing p r e s s u r e (23.0 - 1.1 a n d 20.8 ± 1.4 m m Hg), excision time (6.6 -- 0.3 a n d 7.6 _+ 0.8 minutes), right lung i m p l a n t a t i o n time (66.6 -- 4.8 a n d 60.8 _+ 2.3 minutes), a n d left lung implantation time (64.6 _+ 4.1 a n d 58.0 ± 2.9 minutes) were similar (p = not significant). In group 1, the m e a n ischemic time of the right lung was 3 hours, 9 minutes ± 28 minutes, and for the left lung it was 6 hours, 2 minutes _+ 33 minutes. In group 2, they were 18 hours, 11 m i n u t e s ± 28 minutes a n d 21 hours, 6 minutes ± 21 minutes, respectively. All 5 dogs (100%) in group 1 h a d successful BSLT without c a r d i o p u l m o n a r y bypass. Five of 6 dogs (83%) in group 2 c o m p l e t e d BSLT successfully; 1 dog d i e d of lung e d e m a during the left lung transplantation. Results from the 5 operative survivors in each group form the basis of this report.
Lung Function During the 12-hour Assessment Period All 5 of the operative survivors in each group c o m p l e t e d the 12-hour a s s e s s m e n t with excellent lung function. The results of gas exchange a n d h e m o d y n a m i c s of the donor animals a n d surviving recipients d u r i n g the 12-hour a s s e s s m e n t p e r i o d are shown in Table 1. Arterial oxygen tension (PaO2) was not different b e t w e e n the two groups except at 6 hours a n d did not differ significantly from the donor value in both groups. Arterial carbon dioxide tension (PaCO2) was stable in group 1, but it increased significantly in group 2 after 2 hours of reperfusion. However, PaCO 2 was not significantly different b e t w e e n the two groups except at 6 hours. M e a n p u l m o n a r y artery p r e s s u r e a n d m e a n central venous p r e s s u r e were stable during the a s s e s s m e n t p e r i o d in both groups and did not differ significantly from the donor values. M e a n arterial pressure a n d cardiac o u t p u t were significantly lower in recipient than in donor; however, both m A P a n d CO were stable d u r i n g the a s s e s s m e n t p e r i o d in b o t h groups.
Results After Extubation All 5 animals in each group s h o w e d satisfactory spontan e o u s ventilation a n d were r e t u r n e d to the cage. Survival
338
DATE ET AL 21-HOUR LUNG PRESERVATION
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Table 1. Assessment of Lung and Cardiac Function of Donor and Recipient ~ Function Indicator P a O 2 ( m m Hg) Group 1 Group 2 P a C O 2 ( m m Hg) Group 1 Group 2 m A P (ram Hg) Group 1 Group 2 m P A P (ram Hg) Group 1 Group2 m C V P (ram Hg) Group 1 Group 2 C O (L/rain) Group 1 Group 2
Recipient Donor
1 Hour
2 Hours
4 Hours
6 Hours
611 ÷ 24 629 + 24
538 ± 32 623 ± 32
563 + 35 624 ± 35
559 + 16 605 -+ 16
539 ~ 13 604 Z 13 b
43 + 6 35 ± 6
44 _+ 5 43 ± 5
46 _+ 5 45 _+ 5 c
41 ± 6 51 ± 6 c
39 ± 4 51 z 4 bc
146 _ 9 152 ± 9
112 _+ 4 c 106 + 4 c
120 _+ 6 117 + 6 c
114 ± 10 130 + 10
25 + 3 26+3
27 _+ 4 23+4
27 ~ 3 22_+3
4---1 7±1
4+1 7+1
4±1 5+1
2.4 ± 0.4 2.3 ± 0.4
1.2 + 0.1 c 1.3 -+ 0.1 ~
All values are mean - standard error of the mean.
1.3 -+ 0.2 c 1.2 ± 0.2 c
10 H o u r s
12 H o u r s
528 -- 29 612 -+ 29
569 _+ 20 612 -+ 20
590 + 18 604 -+ 17
40 + 4 50 + 4 c
44 + 5 51 + 5 ~
44 ÷ 4 47 ± 4 ¢
109 ± 8 127 ± 8
95 _+ 8 c 122 + 8 ~
94 _+ 11 122 -+ 11 c
90 ÷ 12 120 -+ 12 c
27 _+ 3 22_+3
27 ~ 3 20z3
27 ± 3 21 ± 3
27 ± 3 20_+3
27 + 3 20±3
4±1 5+1
5±1 5±1
5+1 6+1
5+1 6+1
5-~1 6-+1
1.1 + 0.1 ~ 1.1 ± 0.1 c
1.2 ± 0.2 ~ 1.1 -+ 0.2 ~
b p < 0.05 (group l versus group 2).
8 Hours
1.1 -+ 0.1" 1.1 _+ 0.1 ~
Comment
In the present evaluate the
1.3 ± 0.2 ~ 1.3 -+ 0.2 ~
c p < 0.05 (versus Donor).
CO = cardiac output; mAP mean arterial pressure; mCVP = mean central venous pressure; pressure; PaCO2 - arterial carbon dioxide tension; PaO 2 - arterial oxygen tension.
p e r i o d a n d c a u s e s o f d e a t h a r e s h o w n i n T a b l e 2. T w o dogs in group 1 and 3 dogs in group 2 died of unknown causes within 2 days of operation. In these 5 dogs, postmortem examination of the lungs did not reveal any overt signs of lung injury macroscopically or histologic a l l y (Fig 1). T h e l o n g e s t s u r v i v a l t i m e w a s 4 d a y s i n g r o u p I a n d 8 d a y s i n g r o u p 2. T h e 2 d o g s i n g r o u p 2 t h a t survived more than a week showed clear chest roentgeno g r a m s (Fig 2) w i t h o u t p u l m o n a r y i n f i l t r a t i o n o r p l e u r a l e f f u s i o n , a n d g o o d b l o o d g a s e s (Fig 3) f o r 5 d a y s d e s p i t e slightly reduced respiratory rates.
1.2 -+ 0.2 c 1.2 -"- 0.2 ~
mPAP - mean pulmonary arterial
m e t h o d , w h i c h h a s b e e n p r o v e d to p r o v i d e s a f e p r e s e r v a t i o n f o r u p to 24 h o u r s i n a c a n i n e s i n g l e - l u n g t r a n s plantation model. The BSLT model was used for the f o l l o w i n g r e a s o n s . First, B S L T h a s b e c o m e a s t a n d a r d p r o c e d u r e to r e p l a c e b o t h l u n g s a n d i t s a p p l i c a t i o n is b e i n g w i d e n e d to s e v e r a l e n d - s t a g e l u n g d i s e a s e s i n c l u d ing emphysema, obliterative bronchiolitis, infectious lung diseases such as cystic fibrosis, and possibly pulmonary hypertension [2-4, 6-8]. Second, the need for extending the period of safe preservation becomes more important for this procedure because the ischemic time o f t h e l u n g t r a n s p l a n t e d s e c o n d is u s u a l l y 2 to 3 h o u r s l o n g e r t h a n t h a t o f t h e l u n g t r a n s p l a n t e d first. It s h o u l d
s t u d y , a c a n i n e B S L T m o d e l w a s u s e d to already-established lung preservation
Table 2. Survival Period and Cause of Death After Extubation Group/No.
Survival Period
C a u s e of D e a t h
1 (n = 5)
l 2 3 4 5 2 (n - 6) 1 2 3 4 5 6
3 18 2 2 4
h h days days days
0h 6h 12 h 2 days 7 days 8 days
Pneumothorax Pneumothorax Unknown Unknown Rejection Lung edema Unknown Unknown Unknown Rejection Bronchial d e h i s c e n c e
Fig 1. Photomicrograph qf the lung allograft of a dog in group 2 that died of unknown cause 12 hours after extubahon. No overt sign of lung injury was seen. (Hematoxylin and eosin; original magnification, ×100.)
Ann Thorac Surg 1995;59:336-41
Fig 2. Chest roentgenogram of a recipient in group 2 3 days after bilateral single lung transplantation. No signiyicant abnormalities are seen in lungs.
also be noted that BSLT is often required for patients with infectious lung diseases and posttransplantation graft failure; in such cases severe pleural and mediastinal adhesion often prolongs operation time. Third, the transplanted lung function can be measured under physiologic condition in a BLT model, whereas it is measured under unphysiologic conditions in a single-lung transplantation model because some additional manipulation such as contralateral pulmonary artery occlusion becomes necessary to evaluate solely the function of the transplanted graft I1, 5]. Fourth, we think the BSLT model is better than the single-lung transplantation model for determining the safe preservation time of a particular preservation method, because the animal is totally dependent on the function of transplanted lung tissue over the entire postoperative period. In the single-lung transplantation model, with temporary occlusion of the contralateral pulmonary artery for assessment of the transplanted lung the native lung would act as a reservoir protecting the transplanted lung between the assessment. We maintained the animal on a ventilator for 12 hours after BSLT and focused on the immediate graft function, as this period reflects the effects of preservation without any superimposed effects of rejection or infection. Five of 6 dogs (83%) in the 21-hour preservation group survived the BSLT procedure and showed excellent PaO z and stable pulmonary hemodynamics throughout the 12hour assessment period. In particular, mean PaO2 (the gold standard in terms of lung preservation quality) [9] of the 5 survivors was 604 ± 8 m m Hg at 12 hours. We lost 1 dog because of severe lung edema during the left lung implantation. However, none of the other 5 dogs showed
DATE ET AL 21-HOUR LUNG PRESERVATION
339
PaO2 levels of less than 550 m m Hg during the entire assessment period. It is difficult to explain why this large difference occurred in the same group. We suspect that we made an undetectable technical mistake in this particular 1 animal experiment. A significant increase of PaCO 2 was observed in the 21-hour preservation group. Because the PaCO 2 was measured with a fixed respiratory setting, the increase in PaCO 2 represented the decrease of transplanted lung compliance. However, the decrease of lung compliance did not seem to be fatal as the survivors showed normal PaCO2 after extubation. Despite the fact that several parameters suggested excellent early graft function, the survival of the animals after extubation was modest. It is well k n o w n that dogs can rarely survive bilateral lung transplantation [10, 11] because of the dependence of their respiratory control on vagal innervation [12]. It is for this reason that primates have been used for heart-lung [13] and bilateral lung [14] experiments. About half of the dogs in this experiment died of u n k n o w n causes in an early postoperative period without any overt signs of lung injury macroscopically or histologically. We suspect that causes of death in these animals were related not to poor lung preservation, but rather to other factors such as extensive magnitude of
Pa02
I00 80 6O -r
E E
40
20 0 40
PaC02
30 -r E E
20 I0 0 2O
E
15
r: oi
I0
E
5 0
I
1
I
I
I
I
I
1
1
2
3
4
5
6
7
8
POST- OP (days) Fig 3. Arterial oxygen tension (PaO 2) on roonl air, arterial carbon dioxide tension (PaCO2), and respiratory rate (RR) of 2 recipients in group 2 after exh~bafion. The 2 dogs survived for 7 and 8 days, respectively.
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DATEET AL 21-HOUR LUNG PRESERVATION
operation, effects of denervation, a n d p r o l o n g e d anesthesia (over 18 hours) because of the postoperative assessment. Survivors after extubation s h o w e d a s t e r e o t y p e d deep a n d slow respiratory p a t t e r n with a forceful expiratory effort due to the absence of reflexes n o r m a l l y originating in the lungs. However, we were fortunate to have 2 animals in the 21-hour preservation group survive m o r e than a week, which allowed us to m e a s u r e the graft function further. These 2 animals s h o w e d good arterial b l o o d gases on r o o m air until death, with a m e a n PaO 2 of 74 m m H g a n d PaCO 2 of 35.9 m m Hg, respectively, at 5 days. Although the survival rate was relatively low, these results s u g g e s t e d that the p r e s e n t preservation m e t h o d could provide good long-term graft function. The lung is the only organ that can be p r e s e r v e d with a r e a d y s u p p l y of oxygen t h r o u g h the airway. It has been d e m o n s t r a t e d that lung cells are able to maintain aerobic m e t a b o l i s m utilizing the oxygen in the alveoli [15]. Based u p o n previous studies, our basic strategy for lung preservation was to maintain a m i n i m u m a n d optimal level of aerobic metabolism. For this reason, the p r e s e n t m e t h o d consisted of three i m p o r t a n t elements: preservation solution (low-potassium dextrose glucose), inflation gas (100% oxygen 35 mL/kg), a n d preservation t e m p e r a t u r e (8°C). L o w - p o t a s s i u m dextran glucose solution is an extracellular fluid-type solution that contains p h o s p h a t e buffer, glucose, a n d dextran. Several investigators have r e p o r t e d extracellular fluid-type solution to be s u p e r i o r to intracellular fluid-type solution for lung preservation [16, 17], although Puskas a n d co-workers [18] r e p o r t e d that there was no difference w h e n p r o s t a g l a n d i n E 1 was administ e r e d before p u l m o n a r y artery flush. A high concentration of p h o s p h a t e buffer w o u l d show effective buffer action for carbon dioxide p r o d u c e d as a p r o d u c t of oxygen consumed. Glucose in the preservation solution is actively m e t a b o l i z e d in the glycolytic p a t h w a y as well as in the citric acid cycle, a n d it improves lung preservation [1]. Dextran w o u l d function as an oncotic agent, t e n d i n g to k e e p water in the intravascular c o m p a r t m e n t , t h e r e b y decreasing interstitial e d e m a formation [19]. The oxygen concentration in the inflation gas a n d the degree of inflation are very important. W e d e r a n d coworkers [20] r e p o r t e d that preservation with 100% oxygen inflation a p p e a r e d superior to inflation with room air a n d much superior to inflation with 100% nitrogen. There is recent evidence that the uses of large tidal volume during harvesting and hyperinflation during preservation provide superior preservation, although the mechanism of the beneficial effect has not been clearly demonstrated yet [21, 22]. Lungs were ventilated and hyperinflated with 100% oxygen at a volume of 35 mL/kg in the present study. O p t i m a l t e m p e r a t u r e for lung preservation has b e e n d e m o n s t r a t e d to be in the vicinity of 10°C [5, 23]. W e p r e s e r v e d lungs at 8°C in the p r e s e n t study because we thought that metabolic rate was too fast at 10°C w h e n the preservation time was m o r e than 24 hours, according to the analysis of metabolites in the p r e s e r v e d lung tissue ( u n p u b l i s h e d data). N a k a m o t o a n d co-workers [24] re-
Ann Thorac Surg 1995;59:336-41
p o r t e d optimal t e m p e r a t u r e to be at 8 ° to 9°C in a rabbit lung model. W e recognize that other m e t h o d s of preservation [16, 21, 25] m a y be able to accomplish the s a m e goal, a n d believe that the importance of this work is the d e m o n stration that consistent, excellent, 21-hour lung preservation is achievable.
We gratefully acknowledge the advice received from Dr Joel D. Cooper, Barnes Hospital, St. Louis, MO. We are grateful to Tetsuo Kawakami for his expert technical assistance.
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