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An experimental study on direct revascularization of bronchial circulation by microvascular anastomosis
An experimental study on direct revascularization of bronchial circulation by microvascular anastomosis The effects of direct revascularization of the bronchial artery after bronchoplasty were estimated by laser Doppler velocimetry and india ink injection in dogs. Bronchoplastic surgery at the right main bronchus was performed in all dogs, and the bronchial artery was reconstructed using the internal thoracic artery in the reconstruction group. The mucosal blood flow was measured at the distal side of the anastomosis. India ink was injected into the aorta in the nonreconstruction group and into the internal thoracic artery in the reconstruction group. The peripheral blood flow had diminished immediately after surgerys to 59 % of the baseline value and took 14 days to recover to the baseline value in the nonreconstruction group. However, in the reconstruction group, the blood flow recovered at once to 78 % of the baseline value and had returned to that value in 5 days. Statistically significant differences were noted between the groups from just after operation to day 7. India ink data confirmed these findings. In the nonreconstruction group, no ink was observed in the peripheral bronchial vessels on day 3; it was noted in part of the vessels on day 7 and in most on day 14. On the other hand, a relatively large number of vessels were stained just after operation in the reconstruction group. Thus reconstruction of the bronchial artery by means of the anastomosis with the internal thoracic artery can be said to be a useful and effective method for preventing airway ischemia. (J THORAC CARDIOVASC SURG 1992;104:1067-74)
Shozo Fujino, MD,a Shuhei Inoue, MD,b Naoki Yamashita, MD,a and Atsumi Mori, MD,a Otsu, Shiga, Japan
In lung transplantation or surgical creation of the bronchus, successful healing at the site of anastomosis of the bronchus depends largely on the regional blood flowof the bronchus. In lung transplantation especially, the regional blood flow is very important because a rejective response and immunosuppressive agents interfere with the successful healing of the bronchus. It has been reported that in the 38 patients who underwent lung or lobe transplantations from 1963 to 1980, only one patient lived to be discharged and all of the other nine who survived more than 2 weeks died in the third From "the Second Department of Surgery, Shiga University of Medical Science; and "the Department of Thoracic Surgery, National Sanatorium Minami Kyoto Hospital. Supported by a grant-in-aid (No. 02770829) from the Ministry of Education, Science and Culture, Japan. Received for publication May 10, 1991. Accepted for publication Nov. 4, 1991. Address for reprints: Shozo Fujino, MD, Second Department of Surgery. Shiga University of Medical Science Seta. Otsu, Shiga 52021 Japan. 12/1/35724
week. The major cause of death was disruption of the bronchial anastomosis. I. 2 After heart-lung transplantation, airway complications have also been reported.' To facilitate blood flow recovery, many authors have proposed techniques including covering the site of anastomosis with a pedicle flap of the greater omentum from the abdominal cavity." Collateral circulation between omental vessels and bronchial vessels distal to the anastomosis can be accomplished in only 4 days with omental wrapping.v" while it normally takes 2 to 3 weeks for bronchial circulation to be restored by means of vascular growth across the healing bronchial anastomosis after lung transplantation.?'" However, while omental wrapping is certainly effective for preventing ischemia, it is as yet insufficient in the early postoperative stage and there have been abdominal complications with the procedure. From these points of view, we thought it would be more ideal to restore the blood flow of the bronchial artery directly. Thus reconstruction of the artery would appear to be a valuable technique. To that end, we have studied surgical reconstruction of the bronchial artery using the internal 1067
I 06 8
The Journal of Thoracic and Cardiovascular
Fujino et al.
Surgery
Fig. 1. Microscopic view at the time of anastomosis. The ITA is seen on the left and the bronchial artery is seen on the right. In the case of a bronchial artery separating into several branches, anastomosis was found to be more difficult, since the lumen per vessel was smaller. We did, however, successfully achieve anastomosis with all such arteries. ITA, Internal thoracic artery.
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.
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Fig. 2. Schematic presentation of the procedures. The postoperative situation is indicated on the right. The ITA (*) and the bronchial artery (*) are anastomosed as shown.
Volume 104 Number 4 October 1992
Revascularization of bronchial artery I 0 6 9
thoracic artery (ITA), which has ample blood flow, as a less invasive technique that may be clinically applicable. To examine the effects of direct revascularization of bronchial circulation, we performed radical hilar stripping and bronchoplasty in dogs with and without reconstruction of the bronchial artery, and determined the regional mucosal blood flow by laser Doppler velocimetry (LDV).lO, II
Materials and methods Animals. This study was carried out using 23 adult mongrel dogs weighing 10 to 15 kg. Operations were performed under general anesthesia and endotracheal intubation (intravenous administration of 25 mg/kg pentobarbital sodium). Surgical procedures. The dogs were divided into two groups. All dogs were subjected to right fifth intercostal thoracotomy through the posterolateral incision. The connective tissue surrounding the pulmonary artery and vein was detached for the purpose of intercepting as much of the blood flow from systemiccirculation as possible.After that the right main bronchus was severed and then anastomosed by continuous suturing using an absorbable 3-0 polydioxanone suture. The extent of detachment from the surrounding bronchial connective tissues was kept to a minimum. No further bronchial artery surgery was performed in the dogs in group A (the nonreconstruction group, n = 12), whilein those in group B (the reconstruction group, n = II) the bronchial artery was reconstructed using the right ITA. The ITA was detached from its origin to the level of the fifth intercostal region. Detachment up to the fifth intercostal region yielded a sufficient length; with detachment beyond that, anastomosis would be difficult because there is branching and the ITA becomes thin. After the azygos vein was detached and removed,the location of the bronchial artery was confirmed and the intercostal artery, which simultaneously branches off from the bronchial artery in many cases, was ligated. The bronchial artery was then separated and detached anterior to the esophagus. As the bronchial artery is often found to be thin, the common trunk of the bronchial artery and intercostal artery was used for the anastomosis. When several bronchial arteries were found, we used the thickest one. After general heparinization (50 IU/kg), the ITA was severed at the level of the fifth intercostal region under distal ligation and proximal clipping. The bronchial artery was also severed near its origin under proximal ligation and distal clipping. The ends of the arteries were irrigated with heparinized saline. After severing and then anastomosingthe main bronchus, these two arteries were subjected to end-to-end anastomosis with 8 or 10 interrupted sutures of 7-0 or 8-0 polypropylene using magnifying glasses (Fig. I). After release of the clamps, the patency of the anastomosis was confirmed by allowing the empty bronchial artery to fill and feeling its pulsation. Fig. 2 shows a schema of the procedures. All animals were returned to their cages on the day of the operation to receive humane care in compliance with the "Principlesof 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. 86-23, revised 1985). No more anticoagulant was given in group B.
Fig. 3. An ITA angiogram in group B on the fourteenth postoperative day. It shows that there is sufficient blood supply to the bronchi from the IT A. (Arrow indicates the anastomotic point.)
Measurement procedures. Before and just after operation and at I, 3, 5, 7, 10, and 14 days after operation, LDY was measured successfully in 7 dogs from each group under general anesthesia (intravenous administration of 25 mg/kg pentobarbital sodium) with an LBF-221 laser Doppler apparatus (780 nm wavelength laser from semiconductor; Biomedical Science, Kanazawa, Japan). The dogs were intubated but the balloon cuff was deflated to avoid the possibility of there being an ischemic change of the tracheal wall. The conditions of the respirator were: inspired oxygen concentration, 0.2; tidal volume, 30 nil/kg; respiratory rate, 25/min; however, the blood flowwas measured after the respirator had been stopped for about 10 seconds. The measurement probe was inserted through the channel of a fiberoptic bronchoscope (BF type 10; Olympus, Tokyo, Japan) to the membranous portion of the trachea and the right bifurcation of the upper lobe bronchus and the truncus intermedius. Measurements were performed five times at each site and the mean value of the intermediate three values was regarded as the measured blood flow value. The postoperative peripheral regional blood flow was expressed as the bronchial mucosal blood flow index (BMBFI) as calculated from (Post b/Post t)/(Pre b/Pre t), where Post b is the value of LDY at each postoperative measurement time in
The Journal of
I 0 7 0 Fujino et al.
Thoracic and Cardiovascular Surgery
BMBFI
1.2
1.0
0.8
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06
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2
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7
8
9
10
11
12
13
14
days after operation
Fig. 4. The recovery processes of BMBFI in group A (n = 7). BMBFI, Bronchial mucosal blood flow index.
the peripheral region, Post t is the postoperative value in the trachea, Pre b is the preoperativevaluein the perpheral region, and Pre t is the pereoperativevalue in the trachea. Other observations. Three, 7, and 14 days after operation, two dogsof group A were put to death after general heparinization (300 IU/kg) to examine the regenerationof the bronchial artery across the anastomotic line.The aorta was ligated at the origin and just above the diaphragm under right thoracotomy, and the pulmonary artery, vein,and ligamentwerecut off.Then warmed physiologic saline (300 to 500 ml) was infusedinto the aorta with exsanguinationfrom the superiorvena cava and pulmonary vein. Successively warmed 10% gelatinized india ink (50 to 100m!) was infusedand immediatelythe heart-lung system wascooledand exciseden block.A cross-sectional specimen of the right main bronchus distal from the anastomosis was made for pathohistologicexamination with light microscopy. In the case of group B, india ink was injected into the ITA of two dogsjust after operation and the same examinationwasdone.12 The state of healingofthe anastomosedsiteswasobservedby endoscopy simultaneously with the blood flow measurements. Results All dogs survived operation. One dog of group A and two dogs of group B died of blood loss or respiratory failure for reasons unrelated to the specifics of the procedure during the immediate postoperative period. In group B, the patency of the ITA-bronchial artery anastomosis was confirmed in five dogs but in the other two dogs the anastomosis was occluded on the fourteenth postoperative day. Postoperative ITA angiography was performed on group B dogs (Fig. 3). Changes in bronchial mucosal blood flow. The recovery processes of the BMBFI in group A are shown
in Fig. 4. The distribution of the BMBFI just after operation was between 0.50 and 0.71 and the BMBFI had increased to over 0.80 at day 10 in all dogs. There was relatively little unevenness of the recovery processes of the BMBFI among these dogs. The BMBFI in group B is shown in Fig. 5. The range of distribution just after operation was from 0.62 to 0.93, and more unevenness was observed in the recovery process than in group A dogs. It is considered that the BMBFI in group B dogs was directly affected by the grade of patency of vessel anastomosis. A tendency toward excessive blood flow was observed in dogs No.3, 5, and 15. Dogs No. II and 12 were found to have occlusion of the anastomosis on the fourteenth day after operation. The average changes of the BMBFI in these two groups are shown in Fig. 6. The blood flow in the peripheral bronchial membrane following surgical formation of the bronchus associated with severing of the bronchial artery diminished to about 60% of the baseline value and took 10 to 14 days to return to that value (the exact values of the BMBFI were 0.59 ± 0.06 just after operation, 0.65 ± 0.15 on day 1,0.71 ± 0.lOonday3,0.70 ± 0.08 on day 5, 0.84 ± 0.08 on day 7,0.93 ± 0.10 on day 10, and 0.99 ± 0.06 on day 14). On the other hand, the BMBFI of group B recovered to about 80% of the baseline value and had returned to that value on day 5 (the exact values were 0.78 ± 0.10 just after operation, 0.95 ± 0.19 on day 1,0.90 ± 0.lOonday3, 1.00 ± 0.18 on day 5, 1.00 ± 0.15 on day 7, 1.20 ± 0.37 on day 10, and 1.03 ± 0.18 on day 14). The initial value just after
Volume 104 Number 4
Revascularization of bronchial artery
October 1992
I07I
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Fig. 6. Average changes of BMBFI in both groups.
operation in group B corresponds to the level on postoperative day 5 or 7 in group A. Statistically significant differences were noted between groups A and B just after operation (p < 0.01), on day I (p < 0.01), day 3 (p < O.01),day 5 (p < 0.01),andday7 (p < 0.05). There wereno significant differences on the tenth and fourteenth postoperative days.
Regeneration of bronchial blood flow across the site of anastomosis. Fig. 7, A shows a cross section of a bronchial specimen of an untreated control dog prepared by the infusion of gelatinized india ink into the bronchial artery. Ink was observed extensively in large and small vessels. In group A 3 days after operation, lymphocyte infil-
The Journal of Thoracic and Cardiovascular
I 0 7 2 Fujino et at.
Surgery
A
-.. .'
Fig. 7. A, Microscopic findings in an untreated controldog. The india ink that was infusedinto the bronchialartery is extensively observed in all vessels. B, Three days after operation in group A. No india ink is observed. C, Seven days after operation in group A. India ink can be observedin small amounts. D, Fourteen days after operation in group A. India ink is observedin most of the vessels. E, Immediately after operation in group B. India ink that was infused into the ITA can be seen in a relativelylarge number of vessels. tration and hemorrhaging were noted in the submucosa, but red blood cells remained and no india ink was observed in the vessels (Fig. 7, B), showing that the vessels across the site of anastomosis had not been repaired at this stage. Seven days after operation, india ink was noted in part of the vessels, although in small amounts, indicating the presence of blood flow across the site of
anastomosis (Fig. 7, C). On the fourteenth day, india ink was found in most of the vessels and suggested a considerable advance in the reconstruction of blood flow across the site (Fig. 7, D). However, india ink was observed in a relatively large number of vessels in group B, even immediately after operation (Fig. 7, E).
Endoscopic observation of the site of anastomosis.
Volume 104 Number 4 October 1992
There were no airway complications in any of the dogs in either group. The healing states of anastomosis were good and no significant differences were observed between the two groups. There was a little more bleeding at the anastomotic site in group B than in group A dogs, but it was easily controllable.
Discussion In experimental lung transplantation, the first attempt to preserve bronchial circulation by direct revascularization was performed by Metrasl-' in 1950. Nettleblad and colleagues" reported successful revascularization of the bronchial artery in canine left lower lobe transplantation in 1964. They anastomosed the donor's aortic pouch including the origin of the bronchial arteries to the recipient's descending aorta in a side-to-side fashion. In 1970, Mills and colleagues'f reported canine left lung allotransplantation with reconstitution of the bronchial artery supply. They reimplanted a donor's aortic button in the recipient's descending aorta. In clinical lung transplantation, Haglin and colleagues'? reported a case in 1973 in which they performed a direct left bronchial artery revascularization with a method almost the same as that of Mills. However, none of the above attempted to estimate the bronchial mucosal blood flow. In this study, we used the IT A for revascularization ofthe bronchial artery and estimated the effects by LDV. With this method it is not necessary to confirm the origin of the donor's bronchial artery or to injure the recipient's aorta. Anastomosing the IT A and the bronchial artery is also not very difficult, even when using direct suturing. Isolating and anastomosing the two took only about 25 to 30 minutes. Use of stents, tissue adhesive, and laser would facilitate the anastomosis. As our main purpose was the estimation of the effects of direct revascularization of the bronchial artery, we used a bronchoplasty model with radical hilar stripping to eliminate any confounding effects. The anatomy of the canine bronchial arteries is considerably different from that of the human, 15,17,18 so we could not be certain that our technique would be as simple to do as it was in dogs. We therefore, subsequently performed a few right lung transplantations in cadavers and confirmed that our technique could be done easily in humans. Although no india ink was observed just after operation and on day 3 in group A dogs, the BMBFI was kept at about 0.6 just after operation and had already increased significantly by the third day (p < 0.05). The histologic findings and results of blood flow measurement suggest that the increase in the blood flow observed early after bronchoplasty without reconstruction of the bronchial artery is caused by a shift of the desaturated blood flow from the peripheral pulmonary artery, and that the blood
Revascularization of bronchial artery
10 7 3
supply from the proximal side through newly developed vessels is added to this after about 7 or more days. 19 After reconstruction of the bronchial artery, the BMBFI in group B immediately recovered to 0.78, which value corresponds to the level on postoperative day 5 or 7 in group A dogs. This early recovery may be considerably helpful for successful anastomosis of the bronchus, because early ischemia in the absence of systemic arterial reconstitution in the initial I 0 days after operation may be a major cause of poor bronchial healing." Furthermore, it is conceivable that bronchial artery reconstruction might have some long-term effects on preventing atrophy of submucosal elements or subsequent development of chronic airway diseases, for example, bronchiolitis obliterans. 2o LDV was used for the measurement of bronchial mucosal blood flow in this study. One ofthe problems with LDV is that the blood flow evaluated by it is expressed as a relative value in terms of voltage. With respect to this problem, we have been studying the recovery process of the bronchial blood flow after bronchoplasty by the H 2 clearance method, by which bronchial blood flow can be expressed in an absolute value (rnl/rnin/ 100 gm), and our results with both methods of examination have been almost identical." Thus it seems that a relative evaluation is sufficient for serial examination of the effects of a surgical procedure such as in this study. Because the bronchial mucosal blood flow is thought to be dependent on certain conditions of dogs, there is a danger of being incorrect in using the percentage of the preoperative value as the method of expression. That is the reason we expressed the peripheral regional blood flow as the percentage of the tracheal flow and compared the proportions between the preoperative and postoperative values. Our prior experiments? have shown that the blood flow ofthe mid-trachea can be considered to be unaffected by operation and to change according to systemic conditions.
Conclusions Changes of bronchial mucosal blood flow after canine bronchoplasty were estimated by LDV and india ink injection in two groups of dogs, a bronchial artery reconstruction group and a nonreconstruction group. The following results were obtained: I. The peripheral bronchial mucosal blood flow in the nonreconstruction group diminished to 59% of the baseline value just after operation and took 14 days to return to that value. 2. The peripheral bronchial mucosal blood flow in the reconstruction group recovered to 78% of the baseline value just after operation and had returned to that value in 5 days. 3. No india ink was observed in the peripheral bron-
1 07 4
Fujino et al.
chial vessels on day 3 in the nonreconstruction group. Ink was noted in part of the vessels on day 7 and in most on day 14. 4. A relatively large number of vessels were stained just after operation in the reconstruction group. 5. Reconstruction of the bronchial artery by means of anastomosis to the ITA is a useful and effective method for preventing airway ischemia. Although early airway complications have generally decreased with the improvement of lung preservation and immunosuppressants, direct restoration of the airway circulation may assume importance in preventing early and late airway complications. We thank Ms. Minori Kamuro for technical assistance and Hirofumi Kato, MD, for organizational assistance. REFERENCES
I. Cooper JD. Lung transplantation. Ann Thorac Surg 1989;47:28-44. 2. Veith FJ, Kamholz SL, Mollenkopf FP, Montefusco CM. Lung transplantation 1983. Transplantation 1983;35: 271-8. 3. Griffith BP, Hardesty RL, Trento A, et al. Heart-lung transplantation: lessons learned and future hopes. Ann Thorac Surg 1987;43:6-16. 4. Virkkula L, Eerola S. Use of omental pedicle for treatment of bronchial fistula after lower lobectomy. Scand J Thorac Cardiovasc Surg 1975;9:287-90. 5. Lima 0, Goldberg M, Peters WJ, Ayabe H, Townsend E, Cooper JD. Bronchial omentopexy in canine lung transplantation. J THORAC CARDIOVASC SURG 1982;83:418-21. 6. Morgan E, Lima 0, Goldberg M, Ferdman A, Luk SK, Cooper JD. Successful revascularization of totally ischemic bronchial autografts with omental pedicle flaps in dogs. J THORAC CARDIOVASC SURG 1982;84:204-10. 7. Rabinovich JJ. Re-establishment of bronchial arteries after experimental lung lobe autotransplantation. J THORAC CARDIOVASC SURG 1972;64:119-26. 8. Siegelman SS, Hagstrom JC, Koerner SK, Veith FJ. Res-
The Journal of Thoracic and Cardiovascular Surgery
toration of bronchial artery circulation after canine lung allotransplantation. J THORAC CARDIOVASC SURG 1977; 73:792-5. 9. Fujino S, Inoue S, Matsumoto T, Takahashi K, Yamanaka A, Kato H. Analysis of bronchial mucosal hemodynamics by electrochemically generated hydrogen gas clearance method. J Jpn Soc Bronchol 1986;8:606-12. 10. Stern MD. In vivoevaluation of microcirculation by coherent light scattering. Nature 1975;254:56-8. II. Inui K, Wada H, Yokomise H, et al. Evaluation of a bronchial anastomosis by laser Doppler velocimetry. J THORAC CARDIOVASC SURG 1990;99:614-9. 12. Okada M, Mihashi S, Ito T, Hirano M. Distribution and direction of the blood vessel in the canine vocal cord-histological investigation with india ink injection method. Oto Fukuoka 1978;24:225-32. 13. Metras H. Note preliminaire sur la greffe totale du poumon chez Ie chien. C R Acad Sci 1950;231:1176-7. 14. Nettleblad SC, Soroff HS, Sachs BF, et al. Experimental studies of the response to homotransplantation of pulmonary tissues. Ann NY Acad Sci 1964;120:689-709. 15. Mills NL, Boyd AD, Gheranpong C. The significance of bronchial circulation in lung transplantation. J THORAC CARDIOVASC SURG 1970;60:866-74. 16. Haglin JJ, Ruiz E, Baker RC, Anderson WR. Histologic studies of human lung allotransplantation. In: Wildevuur C, ed. Morphology in lung transplantation. Basel: S Karger,1973:13-22. 17. Schreinemakers HHJ, Weder W, Miyoshi S, et al. Direct revascularization of bronchial arteries for lung transplantation: an anatomical study. Ann Thorac Surg 1990;49:4454. 18. Kasai T. Anatomical findings of the bronchial arteries. J Jpn Soc Bronchol 1989;11:530-40. 19. Kato R. Evaluation of bronchial circulation and wound healing after sleeve lobectomy- a study on tissue oxygen tension and hydroxyproline concentration of the anastomotic site. J Jpn Assoc Thorac Surg 1988;36:923-30. 20. Yousem SA, Dauber JH, Griffith BP. Bronchial cartilage alterations in lung transplantation. Chest 1990;98:1121-4.
Shozo Fujino, MD,a Shuhei Inoue, MD,b Naoki Yamashita, MD,a and Atsumi Mori, MD,a Otsu, Shiga, Japan
In lung transplantation or surgical creation of the bronchus, successful healing at the site of anastomosis of the bronchus depends largely on the regional blood flowof the bronchus. In lung transplantation especially, the regional blood flow is very important because a rejective response and immunosuppressive agents interfere with the successful healing of the bronchus. It has been reported that in the 38 patients who underwent lung or lobe transplantations from 1963 to 1980, only one patient lived to be discharged and all of the other nine who survived more than 2 weeks died in the third From "the Second Department of Surgery, Shiga University of Medical Science; and "the Department of Thoracic Surgery, National Sanatorium Minami Kyoto Hospital. Supported by a grant-in-aid (No. 02770829) from the Ministry of Education, Science and Culture, Japan. Received for publication May 10, 1991. Accepted for publication Nov. 4, 1991. Address for reprints: Shozo Fujino, MD, Second Department of Surgery. Shiga University of Medical Science Seta. Otsu, Shiga 52021 Japan. 12/1/35724
week. The major cause of death was disruption of the bronchial anastomosis. I. 2 After heart-lung transplantation, airway complications have also been reported.' To facilitate blood flow recovery, many authors have proposed techniques including covering the site of anastomosis with a pedicle flap of the greater omentum from the abdominal cavity." Collateral circulation between omental vessels and bronchial vessels distal to the anastomosis can be accomplished in only 4 days with omental wrapping.v" while it normally takes 2 to 3 weeks for bronchial circulation to be restored by means of vascular growth across the healing bronchial anastomosis after lung transplantation.?'" However, while omental wrapping is certainly effective for preventing ischemia, it is as yet insufficient in the early postoperative stage and there have been abdominal complications with the procedure. From these points of view, we thought it would be more ideal to restore the blood flow of the bronchial artery directly. Thus reconstruction of the artery would appear to be a valuable technique. To that end, we have studied surgical reconstruction of the bronchial artery using the internal 1067
I 06 8
The Journal of Thoracic and Cardiovascular
Fujino et al.
Surgery
Fig. 1. Microscopic view at the time of anastomosis. The ITA is seen on the left and the bronchial artery is seen on the right. In the case of a bronchial artery separating into several branches, anastomosis was found to be more difficult, since the lumen per vessel was smaller. We did, however, successfully achieve anastomosis with all such arteries. ITA, Internal thoracic artery.
\~{ ' ['1
\I ~
\I '·.(A .:c, "''
\\.
.
'~<~_
....•. ..•.. ..•... .•.
II, .
/'
ITA
anastomosis
-A
Fig. 2. Schematic presentation of the procedures. The postoperative situation is indicated on the right. The ITA (*) and the bronchial artery (*) are anastomosed as shown.
Volume 104 Number 4 October 1992
Revascularization of bronchial artery I 0 6 9
thoracic artery (ITA), which has ample blood flow, as a less invasive technique that may be clinically applicable. To examine the effects of direct revascularization of bronchial circulation, we performed radical hilar stripping and bronchoplasty in dogs with and without reconstruction of the bronchial artery, and determined the regional mucosal blood flow by laser Doppler velocimetry (LDV).lO, II
Materials and methods Animals. This study was carried out using 23 adult mongrel dogs weighing 10 to 15 kg. Operations were performed under general anesthesia and endotracheal intubation (intravenous administration of 25 mg/kg pentobarbital sodium). Surgical procedures. The dogs were divided into two groups. All dogs were subjected to right fifth intercostal thoracotomy through the posterolateral incision. The connective tissue surrounding the pulmonary artery and vein was detached for the purpose of intercepting as much of the blood flow from systemiccirculation as possible.After that the right main bronchus was severed and then anastomosed by continuous suturing using an absorbable 3-0 polydioxanone suture. The extent of detachment from the surrounding bronchial connective tissues was kept to a minimum. No further bronchial artery surgery was performed in the dogs in group A (the nonreconstruction group, n = 12), whilein those in group B (the reconstruction group, n = II) the bronchial artery was reconstructed using the right ITA. The ITA was detached from its origin to the level of the fifth intercostal region. Detachment up to the fifth intercostal region yielded a sufficient length; with detachment beyond that, anastomosis would be difficult because there is branching and the ITA becomes thin. After the azygos vein was detached and removed,the location of the bronchial artery was confirmed and the intercostal artery, which simultaneously branches off from the bronchial artery in many cases, was ligated. The bronchial artery was then separated and detached anterior to the esophagus. As the bronchial artery is often found to be thin, the common trunk of the bronchial artery and intercostal artery was used for the anastomosis. When several bronchial arteries were found, we used the thickest one. After general heparinization (50 IU/kg), the ITA was severed at the level of the fifth intercostal region under distal ligation and proximal clipping. The bronchial artery was also severed near its origin under proximal ligation and distal clipping. The ends of the arteries were irrigated with heparinized saline. After severing and then anastomosingthe main bronchus, these two arteries were subjected to end-to-end anastomosis with 8 or 10 interrupted sutures of 7-0 or 8-0 polypropylene using magnifying glasses (Fig. I). After release of the clamps, the patency of the anastomosis was confirmed by allowing the empty bronchial artery to fill and feeling its pulsation. Fig. 2 shows a schema of the procedures. All animals were returned to their cages on the day of the operation to receive humane care in compliance with the "Principlesof 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. 86-23, revised 1985). No more anticoagulant was given in group B.
Fig. 3. An ITA angiogram in group B on the fourteenth postoperative day. It shows that there is sufficient blood supply to the bronchi from the IT A. (Arrow indicates the anastomotic point.)
Measurement procedures. Before and just after operation and at I, 3, 5, 7, 10, and 14 days after operation, LDY was measured successfully in 7 dogs from each group under general anesthesia (intravenous administration of 25 mg/kg pentobarbital sodium) with an LBF-221 laser Doppler apparatus (780 nm wavelength laser from semiconductor; Biomedical Science, Kanazawa, Japan). The dogs were intubated but the balloon cuff was deflated to avoid the possibility of there being an ischemic change of the tracheal wall. The conditions of the respirator were: inspired oxygen concentration, 0.2; tidal volume, 30 nil/kg; respiratory rate, 25/min; however, the blood flowwas measured after the respirator had been stopped for about 10 seconds. The measurement probe was inserted through the channel of a fiberoptic bronchoscope (BF type 10; Olympus, Tokyo, Japan) to the membranous portion of the trachea and the right bifurcation of the upper lobe bronchus and the truncus intermedius. Measurements were performed five times at each site and the mean value of the intermediate three values was regarded as the measured blood flow value. The postoperative peripheral regional blood flow was expressed as the bronchial mucosal blood flow index (BMBFI) as calculated from (Post b/Post t)/(Pre b/Pre t), where Post b is the value of LDY at each postoperative measurement time in
The Journal of
I 0 7 0 Fujino et al.
Thoracic and Cardiovascular Surgery
BMBFI
1.2
1.0
0.8
No.
06
•
•
0----0 Group A
1
2
. -----. D-----O
67 9 .l:r----/:,. 13
...----.
0.4
X------------X 16
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2
3
4
5
6
7
8
9
10
11
12
13
14
days after operation
Fig. 4. The recovery processes of BMBFI in group A (n = 7). BMBFI, Bronchial mucosal blood flow index.
the peripheral region, Post t is the postoperative value in the trachea, Pre b is the preoperativevaluein the perpheral region, and Pre t is the pereoperativevalue in the trachea. Other observations. Three, 7, and 14 days after operation, two dogsof group A were put to death after general heparinization (300 IU/kg) to examine the regenerationof the bronchial artery across the anastomotic line.The aorta was ligated at the origin and just above the diaphragm under right thoracotomy, and the pulmonary artery, vein,and ligamentwerecut off.Then warmed physiologic saline (300 to 500 ml) was infusedinto the aorta with exsanguinationfrom the superiorvena cava and pulmonary vein. Successively warmed 10% gelatinized india ink (50 to 100m!) was infusedand immediatelythe heart-lung system wascooledand exciseden block.A cross-sectional specimen of the right main bronchus distal from the anastomosis was made for pathohistologicexamination with light microscopy. In the case of group B, india ink was injected into the ITA of two dogsjust after operation and the same examinationwasdone.12 The state of healingofthe anastomosedsiteswasobservedby endoscopy simultaneously with the blood flow measurements. Results All dogs survived operation. One dog of group A and two dogs of group B died of blood loss or respiratory failure for reasons unrelated to the specifics of the procedure during the immediate postoperative period. In group B, the patency of the ITA-bronchial artery anastomosis was confirmed in five dogs but in the other two dogs the anastomosis was occluded on the fourteenth postoperative day. Postoperative ITA angiography was performed on group B dogs (Fig. 3). Changes in bronchial mucosal blood flow. The recovery processes of the BMBFI in group A are shown
in Fig. 4. The distribution of the BMBFI just after operation was between 0.50 and 0.71 and the BMBFI had increased to over 0.80 at day 10 in all dogs. There was relatively little unevenness of the recovery processes of the BMBFI among these dogs. The BMBFI in group B is shown in Fig. 5. The range of distribution just after operation was from 0.62 to 0.93, and more unevenness was observed in the recovery process than in group A dogs. It is considered that the BMBFI in group B dogs was directly affected by the grade of patency of vessel anastomosis. A tendency toward excessive blood flow was observed in dogs No.3, 5, and 15. Dogs No. II and 12 were found to have occlusion of the anastomosis on the fourteenth day after operation. The average changes of the BMBFI in these two groups are shown in Fig. 6. The blood flow in the peripheral bronchial membrane following surgical formation of the bronchus associated with severing of the bronchial artery diminished to about 60% of the baseline value and took 10 to 14 days to return to that value (the exact values of the BMBFI were 0.59 ± 0.06 just after operation, 0.65 ± 0.15 on day 1,0.71 ± 0.lOonday3,0.70 ± 0.08 on day 5, 0.84 ± 0.08 on day 7,0.93 ± 0.10 on day 10, and 0.99 ± 0.06 on day 14). On the other hand, the BMBFI of group B recovered to about 80% of the baseline value and had returned to that value on day 5 (the exact values were 0.78 ± 0.10 just after operation, 0.95 ± 0.19 on day 1,0.90 ± 0.lOonday3, 1.00 ± 0.18 on day 5, 1.00 ± 0.15 on day 7, 1.20 ± 0.37 on day 10, and 1.03 ± 0.18 on day 14). The initial value just after
Volume 104 Number 4
Revascularization of bronchial artery
October 1992
I07I
BMBFI No. • •
1.8
3
0----0 5
GroupB 16
. - - - - - . 11 8 D-----O .......- - · . 1 2 ~.-.t:. 14 x·····x 15
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,
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oTL...----ri- ---,-r---r---r--r----r----r-.---r---r--r----r----r-.--=_ days before just 2 4 7 3 5 6 8 9 10 11 12 13 14 after after operation Fig. 5. The recovery processes of BMBFI in group B (n
= 7).
BMBFI
14
0--0
Group A IN = 7)
•
Group B IN = 7)
•
1.2 N.5. 1 0 ...--+----;----:. .--.:....-----I+-----__+!-__~__
08
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06
04
o before
Just 1 after
2
3
4
5
6
7
8
9
10
11
12
13
14
days after operation
Fig. 6. Average changes of BMBFI in both groups.
operation in group B corresponds to the level on postoperative day 5 or 7 in group A. Statistically significant differences were noted between groups A and B just after operation (p < 0.01), on day I (p < 0.01), day 3 (p < O.01),day 5 (p < 0.01),andday7 (p < 0.05). There wereno significant differences on the tenth and fourteenth postoperative days.
Regeneration of bronchial blood flow across the site of anastomosis. Fig. 7, A shows a cross section of a bronchial specimen of an untreated control dog prepared by the infusion of gelatinized india ink into the bronchial artery. Ink was observed extensively in large and small vessels. In group A 3 days after operation, lymphocyte infil-
The Journal of Thoracic and Cardiovascular
I 0 7 2 Fujino et at.
Surgery
A
-.. .'
Fig. 7. A, Microscopic findings in an untreated controldog. The india ink that was infusedinto the bronchialartery is extensively observed in all vessels. B, Three days after operation in group A. No india ink is observed. C, Seven days after operation in group A. India ink can be observedin small amounts. D, Fourteen days after operation in group A. India ink is observedin most of the vessels. E, Immediately after operation in group B. India ink that was infused into the ITA can be seen in a relativelylarge number of vessels. tration and hemorrhaging were noted in the submucosa, but red blood cells remained and no india ink was observed in the vessels (Fig. 7, B), showing that the vessels across the site of anastomosis had not been repaired at this stage. Seven days after operation, india ink was noted in part of the vessels, although in small amounts, indicating the presence of blood flow across the site of
anastomosis (Fig. 7, C). On the fourteenth day, india ink was found in most of the vessels and suggested a considerable advance in the reconstruction of blood flow across the site (Fig. 7, D). However, india ink was observed in a relatively large number of vessels in group B, even immediately after operation (Fig. 7, E).
Endoscopic observation of the site of anastomosis.
Volume 104 Number 4 October 1992
There were no airway complications in any of the dogs in either group. The healing states of anastomosis were good and no significant differences were observed between the two groups. There was a little more bleeding at the anastomotic site in group B than in group A dogs, but it was easily controllable.
Discussion In experimental lung transplantation, the first attempt to preserve bronchial circulation by direct revascularization was performed by Metrasl-' in 1950. Nettleblad and colleagues" reported successful revascularization of the bronchial artery in canine left lower lobe transplantation in 1964. They anastomosed the donor's aortic pouch including the origin of the bronchial arteries to the recipient's descending aorta in a side-to-side fashion. In 1970, Mills and colleagues'f reported canine left lung allotransplantation with reconstitution of the bronchial artery supply. They reimplanted a donor's aortic button in the recipient's descending aorta. In clinical lung transplantation, Haglin and colleagues'? reported a case in 1973 in which they performed a direct left bronchial artery revascularization with a method almost the same as that of Mills. However, none of the above attempted to estimate the bronchial mucosal blood flow. In this study, we used the IT A for revascularization ofthe bronchial artery and estimated the effects by LDV. With this method it is not necessary to confirm the origin of the donor's bronchial artery or to injure the recipient's aorta. Anastomosing the IT A and the bronchial artery is also not very difficult, even when using direct suturing. Isolating and anastomosing the two took only about 25 to 30 minutes. Use of stents, tissue adhesive, and laser would facilitate the anastomosis. As our main purpose was the estimation of the effects of direct revascularization of the bronchial artery, we used a bronchoplasty model with radical hilar stripping to eliminate any confounding effects. The anatomy of the canine bronchial arteries is considerably different from that of the human, 15,17,18 so we could not be certain that our technique would be as simple to do as it was in dogs. We therefore, subsequently performed a few right lung transplantations in cadavers and confirmed that our technique could be done easily in humans. Although no india ink was observed just after operation and on day 3 in group A dogs, the BMBFI was kept at about 0.6 just after operation and had already increased significantly by the third day (p < 0.05). The histologic findings and results of blood flow measurement suggest that the increase in the blood flow observed early after bronchoplasty without reconstruction of the bronchial artery is caused by a shift of the desaturated blood flow from the peripheral pulmonary artery, and that the blood
Revascularization of bronchial artery
10 7 3
supply from the proximal side through newly developed vessels is added to this after about 7 or more days. 19 After reconstruction of the bronchial artery, the BMBFI in group B immediately recovered to 0.78, which value corresponds to the level on postoperative day 5 or 7 in group A dogs. This early recovery may be considerably helpful for successful anastomosis of the bronchus, because early ischemia in the absence of systemic arterial reconstitution in the initial I 0 days after operation may be a major cause of poor bronchial healing." Furthermore, it is conceivable that bronchial artery reconstruction might have some long-term effects on preventing atrophy of submucosal elements or subsequent development of chronic airway diseases, for example, bronchiolitis obliterans. 2o LDV was used for the measurement of bronchial mucosal blood flow in this study. One ofthe problems with LDV is that the blood flow evaluated by it is expressed as a relative value in terms of voltage. With respect to this problem, we have been studying the recovery process of the bronchial blood flow after bronchoplasty by the H 2 clearance method, by which bronchial blood flow can be expressed in an absolute value (rnl/rnin/ 100 gm), and our results with both methods of examination have been almost identical." Thus it seems that a relative evaluation is sufficient for serial examination of the effects of a surgical procedure such as in this study. Because the bronchial mucosal blood flow is thought to be dependent on certain conditions of dogs, there is a danger of being incorrect in using the percentage of the preoperative value as the method of expression. That is the reason we expressed the peripheral regional blood flow as the percentage of the tracheal flow and compared the proportions between the preoperative and postoperative values. Our prior experiments? have shown that the blood flow ofthe mid-trachea can be considered to be unaffected by operation and to change according to systemic conditions.
Conclusions Changes of bronchial mucosal blood flow after canine bronchoplasty were estimated by LDV and india ink injection in two groups of dogs, a bronchial artery reconstruction group and a nonreconstruction group. The following results were obtained: I. The peripheral bronchial mucosal blood flow in the nonreconstruction group diminished to 59% of the baseline value just after operation and took 14 days to return to that value. 2. The peripheral bronchial mucosal blood flow in the reconstruction group recovered to 78% of the baseline value just after operation and had returned to that value in 5 days. 3. No india ink was observed in the peripheral bron-
1 07 4
Fujino et al.
chial vessels on day 3 in the nonreconstruction group. Ink was noted in part of the vessels on day 7 and in most on day 14. 4. A relatively large number of vessels were stained just after operation in the reconstruction group. 5. Reconstruction of the bronchial artery by means of anastomosis to the ITA is a useful and effective method for preventing airway ischemia. Although early airway complications have generally decreased with the improvement of lung preservation and immunosuppressants, direct restoration of the airway circulation may assume importance in preventing early and late airway complications. We thank Ms. Minori Kamuro for technical assistance and Hirofumi Kato, MD, for organizational assistance. REFERENCES
I. Cooper JD. Lung transplantation. Ann Thorac Surg 1989;47:28-44. 2. Veith FJ, Kamholz SL, Mollenkopf FP, Montefusco CM. Lung transplantation 1983. Transplantation 1983;35: 271-8. 3. Griffith BP, Hardesty RL, Trento A, et al. Heart-lung transplantation: lessons learned and future hopes. Ann Thorac Surg 1987;43:6-16. 4. Virkkula L, Eerola S. Use of omental pedicle for treatment of bronchial fistula after lower lobectomy. Scand J Thorac Cardiovasc Surg 1975;9:287-90. 5. Lima 0, Goldberg M, Peters WJ, Ayabe H, Townsend E, Cooper JD. Bronchial omentopexy in canine lung transplantation. J THORAC CARDIOVASC SURG 1982;83:418-21. 6. Morgan E, Lima 0, Goldberg M, Ferdman A, Luk SK, Cooper JD. Successful revascularization of totally ischemic bronchial autografts with omental pedicle flaps in dogs. J THORAC CARDIOVASC SURG 1982;84:204-10. 7. Rabinovich JJ. Re-establishment of bronchial arteries after experimental lung lobe autotransplantation. J THORAC CARDIOVASC SURG 1972;64:119-26. 8. Siegelman SS, Hagstrom JC, Koerner SK, Veith FJ. Res-
The Journal of Thoracic and Cardiovascular Surgery
toration of bronchial artery circulation after canine lung allotransplantation. J THORAC CARDIOVASC SURG 1977; 73:792-5. 9. Fujino S, Inoue S, Matsumoto T, Takahashi K, Yamanaka A, Kato H. Analysis of bronchial mucosal hemodynamics by electrochemically generated hydrogen gas clearance method. J Jpn Soc Bronchol 1986;8:606-12. 10. Stern MD. In vivoevaluation of microcirculation by coherent light scattering. Nature 1975;254:56-8. II. Inui K, Wada H, Yokomise H, et al. Evaluation of a bronchial anastomosis by laser Doppler velocimetry. J THORAC CARDIOVASC SURG 1990;99:614-9. 12. Okada M, Mihashi S, Ito T, Hirano M. Distribution and direction of the blood vessel in the canine vocal cord-histological investigation with india ink injection method. Oto Fukuoka 1978;24:225-32. 13. Metras H. Note preliminaire sur la greffe totale du poumon chez Ie chien. C R Acad Sci 1950;231:1176-7. 14. Nettleblad SC, Soroff HS, Sachs BF, et al. Experimental studies of the response to homotransplantation of pulmonary tissues. Ann NY Acad Sci 1964;120:689-709. 15. Mills NL, Boyd AD, Gheranpong C. The significance of bronchial circulation in lung transplantation. J THORAC CARDIOVASC SURG 1970;60:866-74. 16. Haglin JJ, Ruiz E, Baker RC, Anderson WR. Histologic studies of human lung allotransplantation. In: Wildevuur C, ed. Morphology in lung transplantation. Basel: S Karger,1973:13-22. 17. Schreinemakers HHJ, Weder W, Miyoshi S, et al. Direct revascularization of bronchial arteries for lung transplantation: an anatomical study. Ann Thorac Surg 1990;49:4454. 18. Kasai T. Anatomical findings of the bronchial arteries. J Jpn Soc Bronchol 1989;11:530-40. 19. Kato R. Evaluation of bronchial circulation and wound healing after sleeve lobectomy- a study on tissue oxygen tension and hydroxyproline concentration of the anastomotic site. J Jpn Assoc Thorac Surg 1988;36:923-30. 20. Yousem SA, Dauber JH, Griffith BP. Bronchial cartilage alterations in lung transplantation. Chest 1990;98:1121-4.