Prostaglanding E1 or prostacyclin in euro-collins solution fails to improve lung preservation

Prostaglandin E 1 o r Prostacyclin in Euro-Collins Solution Fails to Improve Lung Preservation Sinikka Kukkonen, MD, Lasse J. Heikkil~i, MD, Kalervo Verkkala, MD, PhD, Severi P. Mattila, MD, PhD, and H a n n u Toivonen, MD, PhD Departments of Anesthesiology and Thoracic and Cardiovascular Surgery, Helsinki University Central Hospital, Helsinki, Finland

Background. In search of the ideal composition of the flush solution for pulmonary preservation, w e studied the effects of prostaglandin E1 (PGE~) and prostacyclin as an additive to Euro-Collins solution (ECS) on pulmonary h e m o d y n a m i c s and gas exchange in a porcine single lung transplantation m o d e l using extracorporeal circulation and right heart bypass. Methods. Twenty-two pigs served as donors. The animals were randomized to receive either modified ECS alone (control group, n = 8), ECS with 100/Lg/L of PGE~ (PGE 1 group, n = 6), or ECS with 200/~g/L of prostacyclin (prostacyclin group, n = 8). Left lung transplantation was

performed in 22 recipients after approximately 4 hours of cold ischemia. Results. Carbon dioxide elimination was significantly depressed in the two prostaglandin groups, and the use of PGE~ was associated with a significant decrease in arterial oxygen tension compared with the control group. Both drugs were inefficient in alleviating the increase in pulmonary vascular resistance after transplantation. Conclusion. The use of prostaglandins as constituents of the flush solution was not followed by any improvement of early graft function after cold ischemia.

ingle flush perfusion with modified Euro-Collins solution (ECS) is a widely accepted technique in clinical lung preservation. To i m p r o v e the uniformity of distribution of the solution t h r o u g h the lungs, prostaglandin E 1 (PGE1) or prostacyclin is often a p p l i e d as an adjunct to the perfusate [1]. These agents are used because of their p u l m o n a r y vasodilatory properties to counteract reflex cold vasoconstriction, and because they also possess a wide variety of biologic effects considered beneficial in organ preservation, ie, inhibition of platelet aggregation and n e u t r o p h i l sequestration, prevention of lysosomal enzyme release, and superoxide anion production b y neutrophils [1-4]. Despite these attributes, several studies have q u e s t i o n e d the value of prostaglandins in lung preservation, a n d PGE 1 has even b e e n found to i m p a i r early graft function [1, 5, 6]. C o m p a r i s o n s a m o n g different investigations are limited because of the wide variety of indices and techniques used to assess lung preservation. W e have previously described a porcine single lung transplantation m o d e l in which we are able to adjust individually the blood flow in each lung and study gas exchange and flow distribution b e t w e e n the native and the t r a n s p l a n t e d lung at equal p u l m o n a r y artery pressures, as well as m e a s u r e p u l m o n a r y vascular resistance (PVR) in both lungs at a constant flow rate without the need for a contralateral p n e u m o n e c t o m y or p u l m o nary artery ligation [7]. The p u r p o s e of this study was to investigate, using this perfusion model, the effects of PGE 1 and prostacyclin (100 a n d 200 ~g/L, respectively) as

an additive to ECS on p u l m o n a r y preservation during the first 3 hours after single-lung transplantation.

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Accepted for publication Aug 3, 1995. Address reprint requests to Dr Kukkonen, Department of Anesthesiology, Helsinki University Central Hospital, Haartmaninkatu 4, SF-00290Helsinki, Finland. © 1995 by The Society of Thoracic Surgeons

(Ann Thorac Surg 1995;60:1617-22)

Material and Methods

Procedure F o r ~ - f o u r size-matched infant pigs (weight 16 to 23 kg) were u s e d in this study. All animals received h u m a n e care in compliance with the " G u i d e for the Care and 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). The details of the experimental design have been described earlier [7]. In short, after the donor animals (n = 22) were p r e m e d i c a t e d with ketamine h y d r o c h l o r i d e intramuscularly, anesthesia was i n d u c e d and m a i n t a i n e d with pentobarbital a n d fentanyl, a n d muscle relaxation was achieved with p a n c u r o n i u m . After tracheal intubation, the animals were ventilated (tidal volume 20 mL/kg, 20 times/rain) with a volume-controlled ventilator (Servo 900C; Siemens-Elema AB, Solna, Sweden). The fraction of i n s p i r e d oxygen of the gas mixture (O2-N2) was 0.5, a n d a positive end-expiratory pressure of 5 cm H 2 0 was a p p l i e d throughout the operation. After m e d i a n sternotomy, 500 IU/kg of heparin was given, the main p u l m o nary artery was ligated, a n d the left atrium was cut open. The d o n o r animals were r a n d o m i z e d to receive in b l i n d e d fashion either ECS (Fresenius AG, Bad H o m burg, G e r m a n y ) alone (control group, n - 8), ECS to which 100 /~g/L of PGE 1 (Prostivas; Upjohn, Puurs, Belgium) h a d b e e n a d d e d (PGE 1 group, n 6), or ECS with 200 ~zg/L of prostacyclin (Flolan; Wellcome Foundation Ltd., London, UK) (prostacyclin group, n = 8). The prostaglandins were a d d e d to the perfusate just before their use. In all three groups, 1,000 mL of the cold (4°C) 0003-4975/95159.50 SSDI 0003-4975(95)00736-9

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KUKKONEN ET AL PROSTACYCLIN AND PGE~ IN LUNG PRESERVATION

Ann Thorac Surg 1995;60:1617-22

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Fig 1. Pulmonary artery blood flow in the transplanted lung (A) was significantly reduced compared with the native lung (B) (p < 0.001). Data are shown as mean ± standard error of the mean. Prostacyclin or prostaglandin E 1 (PGE~) in Euro-Collins solution diverted blood away from the transplanted lung.

solution was a d m i n i s t e r e d from a pressurized bag into the main p u l m o n a r y artery over 4 minutes. Cooling of the lungs was s u p p l e m e n t e d by irrigation of the chest cavity with cold saline solution. On completion, the ventilation was discontinued and the trachea was c l a m p e d at m a n ual midinflation with room air. The excised h e a r t - l u n g block was stored i m m e r s e d in cold (4°C) saline solution. The recipient operation b e g a n 2 hours later. The premedication and induction of anesthesia of the animals (n = 22) were identical to those in the donor procedure. The intubation tube was introduced into the trachea through a tracheostomy, and the animals were ventilated as described earlier. Anesthesia was m a i n t a i n e d with a continuous infusion of pentobarbital (5 mg • kg 1 . h 1), fentanyl (10 /zg • kg 1 . h 1), and pancuronium (0.2 m g • kg 1 • h 1). The left femoral vein a n d artery were cannulated for intravenous drug administration a n d right atrial p r e s s u r e a n d systemic arterial pressure monitoring, respectively. After m e d i a n sternotomy and administration of heparin (500 IU/kg), the left lung was removed. The

n e w left lung to be t r a n s p l a n t e d was dissected free from the heart-lung block and r e a n a s t o m o s e d with the recipient's left atrium. The new left m a i n bronchus was intubated, and the tubes from both lungs were connected with a Y-piece to the ventilator. A venous type wirereinforced cannula was i n t r o d u c e d into the right atrium to drain the whole venous return by gravity into a cardiotomy reservoir. Separate perfusions of the lungs were achieved with similar cannulas in the right a n d left p u l m o n a r y arteries and two calibrated roller pumps. P u l m o n a r y a r t e r y p r e s s u r e s (PAP) w e r e m o n i t o r e d t h r o u g h catheters located inside the perfusion cannulas a n d a d v a n c e d b e y o n d their tips. Left atrial pressure (LAP) was m e a s u r e d with a cannula introduced directly into the left atrium. All pressures were r e c o r d e d with the zero reference at the level of the left atrium. Once the extracorporeal circulation started, the proximal part of the right p u l m o n a r y artery was ligated. The total b l o o d flow was kept at 2 L/min (100 + 15 mL/kg) a n d divided b e t w e e n the lungs (by adjusting the p u m p flows) to generate equal pressures (mean) in both p u l m o n a r y arteries, while the systemic circulation was m a i n t a i n e d by the a n i m a l ' s own left ventricle. The following h e m o dynamic m e a s u r e m e n t s were r e c o r d e d after a 15-minute stabilization period: systemic arterial pressure, right atrial pressure, LAP, a n d PAP (right/left). Blood s a m p l e s were drawn from the femoral artery for blood gas analysis. End-tidal CO 2 values were registered sequentially with a c a p n o g r a p h (Datex OY, Helsinki, Finland) through separate s a m p l e lines from the right and left intubation tubes as well as from the c o m m o n expiratory limb. For the m e a s u r e m e n t of s t a n d a r d i z e d PVR, the b l o o d flow was a d j u s t e d to be 1 L/min to each lung and the h e m o dynamic recordings were repeated. All these m e a s u r e ments were r e p e a t e d 30, 60, 90, 120, 150, a n d 180 minutes after the initiation of reperfusion. M e a n systemic arterial pressure, m e a n p u l m o n a r y arterial pressure (MPAP), and PVR were calculated using s t a n d a r d formulas. At the end of the experiment, the animals were sacrificed. Statistical Analysis

All results are expressed as m e a n _+ s t a n d a r d error of the m e a n (SEM) unless otherwise stated. The difference b e t w e e n the PGE 1 group or the prostacyclin group and the control group was tested initially using t h r e e - w a y analysis of variance for r e p e a t e d m e a s u r e s (Multivariate General Linear Hypothesis, Systat; Systat Inc, Evanston IL) for the effects of time, drug, a n d lung (native/ transplanted). The effects of time a n d drug on each lung were tested with two-way analysis of variance, w h e n appropriate. Differences were considered significant at p less than 0.05.

Results The m e d i a n duration of ischemia was 270 m i n u t e s (range, 262 to 302 minutes) in the control group, 258 minutes (range, 233 to 284 minutes) in the PGE 1 group, and 253 minutes (range, 228 to 270 minutes) in the prostacyclin group. All animals survived the operation.

Ann Thorac Surg 1995;60:1617-22

K U K K O N E N ET AL PROSTACYCLIN A N D PGE~ IN L U N G PRESERVATION

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Fig 2. Mean pulmonary artery pressure (MPAP). At equal pulmonary artery pressures in the native and in the transplanted lung (A, B), MPAP was significantly higher in the prostaglandin E~ (PGE~) group (p ~ 0.05). When pulmonary blood jlows were equal (C, D), MPAP was significantly higher in the transplanted lung compared with the native lung (p < 0.001). Data are shown as mean ~ standard error of the mean.

Despite normal LAP, fulminant pulmonary edema of the transplanted lung was the cause of two early deaths in the prostacyclin group, occurring immediately at the onset of reperfusion in 1 animal and after 30 minutes of reperfusion in the other. In the control group, 1 animal was excluded from the study because of left heart failure and high LAP. W h e n the pulmonary blood flows were adjusted to maintain equal pressure in each lung, the median flow difference (native/transplanted lung) was 0.8 L/min (range, 1.5 to 0.7 L/min) in the control group, 1.0 L/min (range, 1.4 to 0.7 L/min) in the PGE 1 group, and 1.1 L/min (range, 1.2 to 0.8 L/rain) in the prostacyclin group. In the control group, the pulmonary artery blood flow of the graft increased over time (p < 0.05), but the flow difference between the lungs remained significant throughout the study in all three groups (p < 0.001) (Fig 1). At equal pressures in the native and in the transplanted lung, MPAP was significantly higher in the PGE 1 group than in the control group (p ( 0.05, Fig 2).

To measure standardized PVR, ie, at equal and constant flow rate, we adjusted the pulmonary blood flow to be 1 Llmin to each lung. The increased flow to the transplanted lung was associated with an augmentation in the MPAP of the graft in all three groups (see Fig 2). Both MPAP and PVR of the transplanted lung were significantly higher than those in the native lung (p < 0.001). The drug treatment had no effect on the increased PVR of the transplanted lung compared with the control group. The interaction of time and drug on PVR was significant in the native lung (p < 0.05, Fig 3). There were no significant differences in LAP between the PGE 1 and the prostacyclin group in comparison with the control group. In the systemic circulation, mean arterial pressure and systemic vascular resistance increased toward the end of the study, but there were no significant differences between the groups. Systemic arterial oxygenation remained satisfactory in all the survivors during the 3-hour study. The arterial oxygen tension was significantly lower in the PGE 1 group

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KUKKONENET AL PROSTACYCLIN AND PGEI IN LUNG PRESERVATION

Ann Thorac Surg 1995;60:1617-22

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Fig 3. Pulmonary vascular resistance (PVR) was significantly higher in the transplanted lung (A) compared with the native lung (B) (p < 0.001). Data are shown as mean +~ standard error of the mean. In the transplanted lung, PVR decreased during the first study hour in all three groups. In the native lung, the decrease of PVR over time was signi~'cant in the prostacyclin group (p ~, 0.05). (PGE1 - prostaglandin Ep)

than in the control group (p ~ 0.05, Fig 4). Carbon dioxide elimination was significantly d e p r e s s e d in both prostaglandin groups c o m p a r e d with the control group (p 0.005, Fig 5). The arterial to end-tidal CO 2 gradient was of the same m a g n i t u d e as r e p o r t e d in previous studies, ie, ranging from 10 to 17 m m Hg in all three groups [7, 8].

Comment Our study d e m o n s t r a t e s that despite the theoretic advantages of PGE 1 and prostacyclin, their use as an additive to ECS did not result in i m p r o v e d lung preservation a n d early graft function c o m p a r e d with the control group. Even the high doses of these agents used in the present experiment were unable to counteract the increase in PVR after transplantation and h a d a detrimental effect on carbon dioxide elimination during the first 3 hours of reperfusion. The use of PGE 1 was also followed by a significantly decreased systemic arterial oxygen tension.

In most of the single lung transplantation studies, it has b e e n possible to investigate the changes in the t r a n s p l a n t e d lung only after a contralateral p n e u m o n e c t o m y or after ligation of the native lung's p u l m o n a r y artery a n d bronchus. O u r study design using extracorporeal circulation, right heart bypass, a n d separate, controlled perfusions of the native a n d the t r a n s p l a n t e d lung eliminates the h e m o d y n a m i c c o n s e q u e n c e s of these techniques. W e were also able to m e a s u r e MPAP, pulm o n a r y blood flow, a n d PVR individually in each lung a n d to compare the responses of the t r a n s p l a n t e d lung to those of the native lung. Because of extracorporeal circulation, the study p e r i o d was limited to the first few hours after transplantation. The e q u a l - p r e s s u r e m o d e l is comparable to the clinical situation during operation, while constant flow rate is a prerequisite for the reliable calculation of PVR a n d eliminates the impact of changes in cardiac output a n d blood flow distribution on p u l m o n a r y hemodynamic measurements. At equal PAP, prostaglandin treatment did not decrease the resistance to blood flow in the t r a n s p l a n t e d lung. Our previous report s h o w e d that PGE 1 infusion during reperfusion also h a d no effect on the b l o o d flow distribution b e t w e e n the lungs [7]. Earlier p u l m o n a r y preservation studies have not m e a s u r e d the individual flow to each lung. The significantly higher MPAP of the PGE~ group c o m p a r e d with the control group reflects the pressure/flow relation in the graft, where even the red u c e d blood flow is able to generate high PAP. The lower MPAP level in the prostacyclin group m a y be an overestimate because of the early deaths of the 2 animals with initially high MPAP values. O u r results are in a g r e e m e n t with a previous investigation, in which the use of PGE 1 in ECS resulted in high PAP [9]. The s t a n d a r d i z e d PVR of the t r a n s p l a n t e d lung was significantly higher than that in the native lung in all three study groups. In our experiment, the use of prostaglandins did not prevent this elevation of PVR. This is in contrast to an earlier study, in which prostacyclin

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Fig 4. Systemic arterial oxygen tension (pO 2) was significantly lower in the prostaglandin E~ (PGE~) group than in the control group (p < 0.05). Data are shown as mean ± standard error of the mean.

Ann Thorac Surg 1995;60:1617-22

KUKKONEN ET AL PROSTACYCLIN AND PGE 1 IN LUNG PRESERVATION

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Fig 5. Arterial carbon dioxide tension (pCO 2) was significantly higher in the prostacyclin and the prostaglandin E 7 (PGE~) groups than in the control group (p < 0.05). Data art" shown as mean ± standard error of the mean.

administered both in donor pretreatment and in the pulmonary perfusate ameliorated the increase in PVR index after 60 minutes of warm ischemia and after ligation of the pulmonary artery of the native lung [10]. Endothelial dysfunction after flush solution (with or without high potassium content), ischemia and cold storage, and reperfusion has been advocated as a possible explanation for this enhanced vasoconstriction [11, 12]. In the native lung, PVR decreased in the prostacyclin group during the first 60 minutes of extracorporeal circulation and remained at this lower level during the rest of the study, suggesting a possible residual effect of the drug due to the large dose and prolongation of half-life in the cold ECS. Increasing the flow to the transplanted lung for the measurement of PVR was followed by a distinct elevation of MPAP. At the same time, decreasing the flow to the native lung resulted in alterations of the pressure level of a much smaller magnitude. This is indicative of an impaired recruitment response of the transplanted lung. Two animals in the prostacyclin group died of pulmonary edema shortly after the onset of reperfusion despite normal LAP. We were unable to identi~ any technical reasons for these early deaths, but because pulmonary venous pressures were not measured, these cannot be completely excluded. In a previous study on isolated blood-perfused lungs, prostacyclin, either alone or after thromboxane A 2 analogue-induced vasoconstriction, increased fluid filtration by increasing vascular surface area and pulmonary microvascular permeability to protein [13]. In another investigation, PGEj as a constituent of flush solution (ECS 30 mL/kg, after removal of the left lung) was found to increase the wet/dry lung weight ratio compared with a control group [6]. On the other hand, the use of Wallwork's solution containing 20% blood, Ringer's lactate (potassium content 4 mmol/L), and prostacyclin for flushing at a rate of 40 mL/kg resulted in reduced pulmonary weight gain after 30 minutes of reperfusion [14]. When suboptimal amounts of ECS (20 mL/kg) were administered together with Iloprost, the

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synthetic analogue of prostacyclin, both in donor pretreatment and as a constituent of the perfusate, there was no difference in the lung water content between the control and the prostaglandin group [15]. Compared with earlier studies, our prostacyclin dose was in the upper range, and it is possible that the use of a high dose of a potent pulmonary vasodilator in ECS during hydrostatic stress (high volume, high flow) and vasoconstriction induced by the high potassium content of the solution may have rendered the lungs more prone to edema formation. Many investigators consider oxygenation to be perhaps the most sensitive indicator of lung preservation. In our study, the arterial oxygen tension was significantly lower in the PGE~ group compared with the control group. Most studies do not support the concept that donor treatment with PGE~ is helpful in improving oxygenation during the early reperfusion period [3, 5, 10, 16]. Even deleterious effects have been reported [6]. The use of prostacyclin either in pretreatment or in ECS has been found to improve pulmonary oxygen transfer in experimental designs, where the contralateral pulmonary artery is ligated [3, 10, 171. Our results of the effect of prostacyclin on oxygenation may be too optimistic, because of the two nonsurvivors, but no improvement was detected compared with the control group. The use of prostaglandins was followed by significantly depressed CO 2 elimination, which has not been reported previously in the literature. Adding PGE~ or prostacyclin to the pulmonary flush solution therefore seems to be associated with deterioration of gas exchange of varying degree because of an increased ventilation-perfusion mismatch. We conclude that PGE 1 and prostacyclin as constituents of modified ECS are inefficient in counteracting the mechanism responsible for the elevation of PVR after transplantation. The changes in the alveolar-capillary network after high-flow, high-volume crystalloid flush solution containing a powerful pulmonary vasodilator and followed by ischemia and cold storage and reperfusion are associated with untoward changes in gas exchange after single-lung transplantation. This study was supported by the Finnish Academy. We thank Dr Klaus Olkkola for his statistical advice and Mrs Pirkko Uhlb/ick for her excellent technical assistance.

References

1. Kirk AJ, Colquhoun IW, Dark JH. Lung preservation: a review of current practice and future directions. Ann Thorac Surg 1993;56:990-1000. 2. Moncada S, Flower RJ, Vane JR. Prostaglandins, prostacyclin, thromboxane A2, and leukotrienes. In: Gilman AG, Goodman LS, Rall TW, Murad F, eds. The pharmacologic basis of therapeutics. New York: Macmillan, 1985:660-74. 3. 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. 4. Fantone JC, Marasco WA, Elgas LJ, Ward PA. Stimulus specificity of prostaglandin inhibition of rabbit polymorpho-

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KUKKONENET AL PROSTACYCLIN AND PGE~ |N LUNG PRESERVATION

nuclear leukocyte lysosomal enzyme release and superoxide anion production. Am J Pathol 1984;115:9-16. Bonser RS, Fragomeni LS, Jamieson SW, et al. Effects of prostaglandin E~ in twelve-hour lung preservation. J Heart Lung Transplant 1991;10:310-6. Bonser RS, Fragomeni LS, Edwards BJ, et al. Allopurinol and deferroxamine improve canine lung preservation. Transplant Proc 1990;22:557-8. Kukkonen S, Heikkil~i L, Verkkala K, Mattila S, Toivonen H. The pulmonary vasodilatory properties of PGE 1 are blunted after experimental single lung transplantation. J Heart Lung Transplant 1995;3:280-8. Jellinek H, Hiesmayr M, Simon P, Klepetko W, Haider W. Arterial to end-tidal CO2 tension difference after bilateral lung transplantation. Crit Care Med 1993;21:1035-40. Ueno T, Yokomise H, Oka T, et al. The effect of PGE 1 and temperature on lung function following preservation. Transplantation 1991;52:626-30. Hooper TL, Thomson DS, Jones MT, et al. Amelioration of lung ischemic injury with prostacyclin. Transplantation 1990; 49:1031-5. Kimblad PO, Sj6berg T, Massa G, Solem J-O, Steen S. High potassium contents in organ preservation solutions cause strong pulmonary vasoconstriction. Ann Thorac Surg 1991; 52:523-8.

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12. Kimblad PO, Sj6berg T, Steen S. Pulmonary vascular resistance related to endothelial function after lung transplantation. Ann Thorac Surg 1994;58:416-20. 13. Yoshimura K, Tod ML, Pier KG, Rubin LJ. Effects of thromboxane A 2 analogue and prostacyclin on lung fluid balance in newborn lambs. Circ Res 1989;65:1409-16. 14. 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. 15. Hooper TL, Fetherston GJ, Flecknell PA, Dark JH, McGregor CG. The use of a prostacyclin analog Iloprost, as an adjunct to pulmonary preservation with Euro-Collins solution. Transplantation 1990;49:495-9. 16. Puskas JD, Cardoso PF, Mayer E, Shi S, Slutsky AS, Patterson GA. Equivalent eighteen-hour lung preservation with low-potassium dextran or Euro-Collins solution after prostaglandin E 1 infusion. J Thorac Cardiovasc Surg 1992;104: 83-9. 17. Klepetko W, Mfiller MR, Khiinl-Brady G, et al. Beneficial effects of Iloprost on early pulmonary function after lung preservation with modified Euro-Collins solution. Thorac Cardiovasc Surg 1989;37:174-9.

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