Experimental laser-assisted end-to-side microvascular anastomosis

The authors present a new technique of end-to-side microvascular anastomosis in a rat carotid artery model, employing a milliwatt CO2 laser. Both carotid arteries were isolated and approximated in an end-to-side fashion by the placement of four 10-0 nylon stay sutures. The milliwatt CO2 laser was used to effect vessel anastomosis between the sutures, using 70-100 mW of power. Animals were killed 8 weeks postoperatively. Angiography of each anastomosis was performed in all animals. All anastomoses were then harvested, and submitted for histological analysis. Anastomotic patency was 100%, both intraoperatively and angiographically. There was no evidence of intravascular thrombus, anastomotic stenosis, or pseudoaneurysm formation. Early in the experiment, some anastomoses showed localized dilatation at the anastomotic site. The histologic changes at the anastomotic site are described. Laser-assisted microvascular anastomosis is a feasible technique, and a potential alternative to conventional suture techniques.     

Microvenous end-to-side anastomosis: an experimental study comparing the Unilink system and sutures

A method for mechanical microvascular end-to-side anastomosis is presented and compared to conventional suture technique. Twenty rabbits had their facial veins divided from the jugular veins and reanastomosed end-to-side to the jugular veins, 2 cm cranially to the original bifurcation. The anastomoses were performed on one side of the neck with the Unilink system and on the other side with sutures. At sacrifice at two weeks (10 animals) and at 16 weeks (10 animals), all anastomoses were tested for patency and histologically evaluated. All 40 anastomoses were fully patent. The time required for completion of a mechanical anastomosis was on the average one-fourth the time required for suture anastomosis. No thrombus formation was noted in any of the specimens, but a slight narrowing because of intimal hyperplasia was noted in the recipient vessels in two mechanical anastomoses. It was demonstrated that mechanical anastomoses of small veins end-to-side can be performed in a rapid and safe manner with the Unilink system.     

A comparison of CO2 laser-assisted venous anastomoses and conventional suture techniques: patency, aneurysm formation, and histologic differences

The expected patency and the potential complications of CO2 laser-welded end-to-end venous anastomoses have not been well established despite increasing clinical interest in the subject. To further study this relatively new technique we used the internal jugular veins (1.0 to 1.4 mm diameter) of 15 New Zealand White rabbits weighing 2.5 to 3.5 kg. On one randomly selected side, a laser-welded end-to-end anastomosis was performed in all animals by placing three equidistant stay sutures followed by welding the vein edges with a CO2 laser (spot size of 0.27 mm, power of 100 mW, and power density of 175 W/cm2). On the contralateral side, the vein was anastomosed with interrupted 10-0 nylon sutures in 10 animals, and in the remaining five animals a continuous 10-0 nylon suture technique was used. All anastomoses were surgically assessed at 30 days after operation. A significantly lower 30-day patency rate (p less than 0.05, Fisher's Exact Test) was found in anastomoses constructed by use of the continuous technique (20%) compared with either interrupted (90%) or the laser-assisted technique (87%). No significant difference was observed in 30-day patency between laser-assisted and conventional interrupted anastomoses. Anastomoses performed with the continuous and the laser-assisted technique required 12.5 +/- 1.3 and 12.9 +/- 3.0 minutes, respectively, whereas those constructed with interrupted technique required 19.1 +/- 4.5 minutes (p less than 0.05, Student-Neuman-Keuls' Test). No evidence of false or true aneurysm was noted in any of the animals. Histologic evaluation of laser-assisted anastomoses demonstrated early full-thickness coagulation necrosis of the wall with reendothelialization by 7 days and complete healing by 30 days after the procedure. Conventional anastomoses showed reendothelialization and minimal necrosis near the sutures at 7 days, but healing was complete by 30 days after the procedure. The patency rate of vein anastomoses performed with the CO2 laser is excellent and superior to the one obtained with continuous sutures, and except for less operating time, the former technique does not appear to offer any significant advantage over the conventional interrupted suture technique for small vein anastomosis in this animal model up to 1 month of follow-up.     

Patency of laser-assisted anastomoses in small vessels: one-year follow-up

Laser-assisted arterial anastomoses can now be performed with satisfactory short-term patency. This study was undertaken to evaluate patency and aneurysm formation with a 1-year follow-up. A microscopically guided CO2 laser was used to anastomose 1.5 to 2.0 mm carotid arteries in 24 rabbits. Under X6 to X40 magnification, 60 to 70 mW were delivered with a spot size of approximately 0.32 mm. One carotid artery underwent laser anastomosis; the opposite served as a sutured control (10-0 nylon sutures). The 48 end-to-end anastomoses were evaluated for patency and aneurysm formation at 3, 6, and 12 months. Aneurysms were defined as a 1.5 times increase in diameter at the anastomotic site. The vessels underwent microscopic examination. All laser-assisted and sutured anastomoses were patent up to 1 year. At 3 months, one of eight sutured and one of eight laser anastomoses were aneurysmal; stenosis was noted in one laser anastomosis. At 6 months, one of eight laser and 0 of eight sutured anastomoses were aneurysmal. At 12 months, one of eight rabbits had died; of the remaining seven, three of seven laser and zero of seven sutured anastomoses were aneurysmal. In total, five of 23 (21.7%) aneurysms developed with the laser technique and one of 23 (4.3%) with the suture technique (p less than 0.05). Laser-assisted anastomoses are technically feasible, and patency at 1 year is equal to those performed with the suture technique. Aneurysm formation is a consistent problem that demands further investigation.     

Comparison of continuous and interrupted suture techniques in microvascular end-to-side anastomosis

To compare the speed and patency rates of the continuous and interrupted suture techniques in microvascular end-to-side anastomosis, 10 anastomoses utilizing each technique were performed using a femoral artery-superficial epigastric vein bypass model in Sprague-Dawley rats. The continuous suture technique was found to be almost twice as fast as the interrupted technique with no functional compromise. Patency for both techniques was 100 percent. These results are similar to those of several recent reports comparing the two techniques in end-to-end anastomosis and suggest that the continuous suture technique may be the most efficient technique for end-to-side anastomosis as well.     

Long-term effects of extraluminal dilatation with a rigid circle on arteriovenous anastomotic line in venous grafts transposed into arterial defects

Postanastomotic narrowing resulting from subintimal hyperplasia is a well-known phenomenon. In the current study the authors compared a metallic circle and conventional suture technique in anastomoses performed in two ends of external jugular vein grafts interposed in carotid arteries of rabbits. They recorded the patency rates, fluid flow rates, and histological effects of the circle on the anastomotic line and compared them with conventional suture anastomoses. In 16 rabbits (experimental group) a standard suture was used in both ends of the jugular vein graft transposed to the carotid arteries on one side. On the other side, circle anastomoses were performed on both ends of the vein graft. In an additional 8 rabbits (control group), the anterior jugular veins and carotid arteries were dissected on both sides and left. During postoperative week 12, in 8 rabbits of the experimental group, the flow rates of carotid arteries were measured in vitro, and intraluminal silicone casts were prepared. In the remaining 8 experimental rabbits, carotid angiographies were performed and anastomotic segments were harvested for histological examination. Flow rates were also measured in the control group, and artery and vein segments were harvested. The patency rates of the vein grafts with metallic circle anastomoses were 100%, whereas conventional suture patency was 75% at week 12. Flow rates were significantly higher in the metallic circle-anastomosed vein grafts (74 ml per minute vs. 123 ml per minute, mean values; p < 0.05). Histological examination revealed reduced intimal thickness in the metallic circle anastomoses compared with conventional suture anastomoses. Dilatation of the arteriovenous end-to-end anastomotic line by a rigid circle prevents anastomotic narrowing in the long term.     

Low power CO2 laser-assisted microvascular anastomosis: an experimental study

Low power CO2 laser-assisted microvascular anastomosis (LAMA) was used for saphenous artery autotransplantation in 40 rabbits. Eighty end-to-end anastomoses were performed by three methods (conventional interrupted suture, stay suture + laser, laser without stay suture). The long term patency rate in the three types of anastomosis is 93%, 93%, and 100%, respectively. The time needed for the laser procedure is half to one-third of that required for the interrupted suture method. The tensile strength of the bonding site can withstand up to 250 mm Hg of arterial pressure. We have demonstrated that the CO2 laser can be used in microvascular anastomosis with or without stay sutures. Aneurysm formation is a potential risk of LAMA. Accurate coaptation of the transected vessel, precise control of laser energy, and minimal area exposed to the laser beam are the key points for further improving anastomotic quality.     

A new method of vascular anastomosis by CO2 laser: experimental and clinical study

It is difficult to maintain the long-term patency after conventional anastomosis especially for the small caliber vessels. Since 15 years we have performed aortocoronary bypass with suture materials for the patients with ischemic heart disease. There are some problems in maintaining the long-term patency of the bypass grafts. Low energy CO2 laser was utilized to make vascular anastomosis with a few stay sutures. Vascular anastomoses (side-to-side, end-to-end, end-to-side) were carefully made by CO2 laser in the regions of the femoral arteries and veins, the carotid arteries and jugular veins in dog. A-C bypass was also successfully carried out between the internal mammary artery and the left anterior descending artery under the beating heart in experiment. Outputs of 20-40 mW and irradiation times of 6-12 sec/mm were optimal conditions for anastomosis of the small caliber vessels. There were no problems in the intensity and the healing of the anastomotic sites in comparison with the conventional suture method. On the basis of these excellent experimental results a low energy CO2 laser was employed clinically for vascular anastomosis of the peripheral vessels in 28 patients with angina pectoris or chronic renal failure and cardiac failure. There were no complications such as bleeding and suture line aneurysm after surgery. In conclusion, vascular anastomosis by laser might be recommended in performing with safety and rapidity for small caliber vessels.     

End-to-end versus end-to-side arterial anastomosis patency in microvascular surgery

The patency rates of microsurgical end-to-end and end-to-side anastomosis in the rat carotid artery were studied. Seventy end-to-end and seventy end-to-side arterial anastomoses, using 10-0 nylon interrupted sutures, were performed on 140 Sprague-Dawley rats. Findings indicated 100% patency in end-to-end as well as end-to-side immediately and 1 week post-anastomosis. This investigation suggests that there is no significant advantage between the methods studied based on vessel patency alone. The decision to perform an end-to-end vs. an end-to-side arterial anastomosis should be based upon the clinical circumstances encountered, since no significant difference in patency rates exists. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:125-128 1998     

Animal model to compare the effects of suture technique on cross-sectional compliance on end-to-side anastomoses.

OBJECTIVE: An animal model has been developed to compare the effects of suture technique on the luminal dimensions and compliance of end-to-side vascular anastomoses. METHODS: Carotid and internal mammalian arteries (IMAs) were exposed in three pigs (90 kg). IMAs were sectioned distally to perform end-to-side anastomoses on carotid arteries. One anastomosis was performed with 7/0 polypropylene running suture. The other was performed with the automated suture delivery device (Perclose/Abbott Labs Inc.) that makes a 7/0 polypropylene interrupted suture. Four piezoelectric crystals were sutured on toe, heel and both lateral sides of each anastomosis to measure anastomotic axes. Anastomotic cross-sectional area (CSAA) was calculated with: CSAA = pi x mM/4 where m and M are the minor and major axes of the elliptical anastomosis. Cross-sectional anastomotic compliance (CSAC) was calculated as CSAC=Delta CSAA/Delta P where Delta P is the mean pulse pressure and Delta CSAA is the mean CSAA during cardiac cycle. RESULTS: We collected a total of 1200000 pressure-length data per animal. For running suture we had a mean systolic CSAA of 26.94+/-0.4 mm(2) and a mean CSAA in diastole of 26.30+/-0.5 mm(2) (mean Delta CSAA was 0.64 mm(2)). CSAC for running suture was 4.5 x 10(-6)m(2)/kPa. For interrupted suture we had a mean CSAA in systole of 21.98+/-0.2 mm(2) and a mean CSAA in diastole of 17.38+/-0.3 mm(2) (mean Delta CSAA was 4.6+/-0.1 mm(2)). CSAC for interrupted suture was 11 x 10(-6) m(2)/kPa. CONCLUSIONS: This model, even with some limitations, can be a reliable source of information improving the outcome of vascular anastomoses. The study demonstrates that suture technique has a substantial effect on cross-sectional anastomotic compliance of end-to-side anastomoses. Interrupted suture may maximise the anastomotic lumen and provides a considerably higher CSAC than continuous suture, that reduces flow turbulence, shear stress and intimal hyperplasia. The Heartflo anastomosis device is a reliable instrument that facilitates performance of interrupted suture anastomoses.     

Carotid artery end-to-end anastomosis in the rat using the argon laser

Microvascular end-to-end anastomoses of rat common carotid arteries measuring 0.6 to 0.7 mm in diameter were performed using an argon surgical laser system. Vascular bonding with the argon laser was accomplished in all cases. The anastomosed carotid artery segments were evaluated both angiographically and histologically at 1 day, 1 week, and 1 month after laser bonding. With increasing time after anastomosis, there was a trend toward increasing angiographically proven stenosis of the anastomotic segment and histologically demonstrated pseudoaneurysm formation of the vessel wall at the bonded site. Pseudoaneurysm formation was associated with a dense inflammatory response in the anastomotic vessel segment. In spite of excellent initial tissue bonding and vessel patency, the delayed results of progressive vessel wall disruption and segmental stenosis indicate that further experience in using the argon laser for vessel welding is needed before this method can be accepted as an alternative to current microvascular suture technique.     

Microvascular anastomoses using an Nd-YAG laser

The authors performed anastomoses of small vessels with the Nd-YAG laser, comparing these with conventional suture anastomoses. Some arteries were sutured with 10-0 nylon with about eight suture sites, and others were held by stay sutures at three points with laser irradiation performed between them. Two surgeons performed the anastomoses in the same way. The first was well-trained and experienced, and the second was technically inexperienced. The authors evaluated clamping time, patency rate, and endoscopic and histologic findings. The patency rate of the first surgeon was 100 percent (30/30) in the suture anastomoses and was 97 percent (29/30) in the laser anastomoses. For the second surgeon, the rates were 60 percent (18/30) in the suture group and 80 percent (24/30) in the laser group. On histologic examination, the suture group showed inflammatory cells around the suture site at the fourth week after the operation. In the laser group, an inflammatory reaction around the suture material was observed, but the other areas recovered. For the experienced surgeon, the patency rate and clamping time of the laser anastomosis provided no statistically significant difference to those of the suture anastomosis. On the other hand, for the inexperienced surgeon, the patency rate of the laser anastomosis was superior to that of the suture anastomosis, and the clamping time of the laser anastomosis was shorter than that of the suture anastomosis. Therefore, the authors concluded that the Nd-YAG laser anastomosis is useful for small vessels.     

Sutureless method of micro-vascular anastomosis using low-energy Nd-YAG laser

Sutureless end-to-end anastomosis of rat common carotid artery was carried out, low energy Nd-YAG laser being used thereby. An intraluminal-intervascular splint, made of water-soluble poval, was used for precise adaptation of the intimas. Neither stay suture nor glue was required. The patency rate of the anastomosed vessels, 24 hours after operation, was as high as 91%. The vessels were confirmed to be likewise patent on the 7th and 30th postoperative day. Complications such as pseudoaneurysm formation or stenotic change, were negligible. The fusion of the anastomosis with Nd-YAG laser was histologically proved to be satisfactory and the result of tensile strength test was excellent. Temperature at the anastomotic site during laser irradiation was measured, optimal energy for anastomosis determined and possible mechanism of vascular fusion by laser beam postulated. The major advantages of the laser technique combined with poval splint, such as rapidity, consistency and no residual foreign body (thread or adhesive), are discussed.     

In search of the "perfect" anastomosis

Forty-five end-to-side microvascular anastomoses were completed in rat carotid arteries of 0.7-0.8 mm diameter (anastomosing the distal end of the left common carotid to the side of the right common carotid). For comparison both 10-0 and 11-0 sutures were utilized in different anastomotic techniques: interrupted, direct-continuous, and diagonal-continuous sutures, plus total mural thickness vs. partial mural thickness (piercing only the adventitia and outer media, excluding the intima). Anastomoses were evaluated for patency and scanning electron microscopic appearance after 10 to 12 weeks. The results indicate complete patency in all anastomoses. Ultrastructural observations revealed nearly normal intimal appearance in the partial medial technique and only minimal evidence of intimal injury in the other techniques. It is concluded that 100% patency can be obtained regardless of suture size or anastomotic technique. The most important factor in anastomotic patency is the operator's technical skill.     

Mechanics of end-to-end artery-to-PTFE graft anastomoses

On some occasions vascular surgeons are called upon to construct an end-to-end anastomosis using prosthetic graft material. If a spatulated anastomosis is not fashioned, three important variables that are under the surgeon’s control could affect anastomotic dimensions: (1) selection of graft material, (2) graft size relative to the native vessel, and (3) suture technique. Accordingly, studies were performed on 36 nonspatulated, end-to-end artery-to-polytetrafluoroethylene (PTFE) grafts to evaluate the effects of graft size and suture technique on anastomotic dimensions. Size-matched (3 mm) and slightly oversized (4 mm) grafts were anastomosed end-to-end to 3 mm pig carotid arteries using (1) running polypropylene (Surgilene) sutures, (2) running polybutester (Novafil) sutures, or (3) interrupted sutures. After 30 min the vessels were excised, filled with contrast material, and radiographs were obtained to measure anastomotic dimensions. Results showed that, at every comparable pressure, 4 mm grafts produced larger anastomoses than did 3 mm grafts. In addition 4 mm grafts produced smoother anastomoses without a constricted or “pinched” appearance at the graft-artery junction. Marked compliance mismatch was observed with both sized grafts. There was no significant difference in the dimensions of the anastomoses or compliance mismatch with the three different suture techniques. These studies indicate that, when using PTFE grafts for end-to-end anastomoses, a graft that is slightly larger than the artery is preferable to provide the largest and smoothest anastomosis, and that any of the three suture techniques may be used. PTFE grafts were provided by W. L. Gore, Flagstaff, AZ. Sutures were provided by Davis & Geck, Co., Danbury, CT. No other support, direct or indirect, was provided by any manufacturer.     

Clinical experience with non-penetrating vascular clips in free-flap reconstructions.

To date, the gold standard for performing a microvascular anastomosis has been the penetrating suture with attached needle. During the last two decades, non-penetrating techniques have been introduced, including the Unilink system for end-to-end anastomoses, and the VCS clip-applier system for both end-to-end and end-to-side anastomoses. The aim of this study was to compare the results of different techniques used to create microvascular anastomoses in free-flap reconstructions. Between January 1995 and October 1999, we performed 474 microvascular anastomoses in 216 consecutive free-tissue transfers. The anastomosis techniques included manual sutures (42%), Unilink rings (34%) and VCS clips (24%). Seven combined sutured-clipped anastomoses were excluded from further analysis. The mean anastomotic time when rings were applied was significantly shorter than when using clips (P 0.0001) or sutures (P 0.0001). Venous anastomoses using clips took less time than those using sutures (P 0.05). There were 19 anastomotic failures, all of which lead to early flap failure. Ten flaps were salvaged by early reoperation; nine flaps were lost. Three more flaps were lost as a result of other causes, bringing the flap survival rate down to 94.4%. Early flap failure was caused by failure of the arterial anastomosis in eight cases; all of them were sutured (these represented 5% of all arterial anastomoses with sutures). None of the clipped arterial anastomoses failed. Early flap failure was caused by failure of the venous anastomosis in 11 patients. Three of these anastomoses were sutured (representing 6% of all venous anastomoses with sutures), seven were anastomosed with rings (representing 5% of all venous anastomoses with rings) and one was clipped (representing 2% of all venous anastomoses with clips). Both the VCS clip-applier system and the Unilink system are easy to handle and allow fast microvascular anastomoses without intraluminal penetration. The patency rate of clipped vessels is at least as good as the patency rates of vessels anastomosed using sutures or rings.     

A new technique for anastomosing veins to small-caliber arteries

A new technique of arteriovenous anastomosis is presented which lessens the complication of intravascular turbulence and thrombosis seen with elongated and narrow anastomotic segments. The axillary artery and jugular vein were anastomosed in 10 ZBZ-Cara rats using microsurgical techniques. The jugular vein was prepared as a tubular structure facilitating two end-to-end anastomoses rather than the customary end-to-side technique. Angiographic patency was demonstrated at 3 weeks in 10/10 rats. Two of ten anastomotic segments were considered quite narrow; however, angiographic demonstration of flow was excellent.     

A new microvascular "sleeve" anastomosis

A new technique for performing a microvascular end-in-end or "sleeve" anastomosis is described. The new method utilizes two asymmetrically placed, looped sutures that do not enter the active lumen or breach the active intima. It has advantages over previous methods because it consistently saves time and because of the decrease in the number of possible technical complications. In 77 anastomoses performed in white rats by different surgeons, including a few inexperienced students of microsurgery, there was only one failure (24-hr patency). After eight practice anastomoses, the average time taken from vessel division to final clamp release in 30 procedures was 7 min 33 sec, with a standard deviation of 1 min 45 sec. The sleeve anastomosis performed by this method has shown itself to be as reliable as a conventional end-to-end suture method and has the advantages of significant time saving and minimization of intimal trauma. The anastomosis of vessels of differing sizes is facilitated by the conformation of this new method and the technique has clinical potential in the anastomoses of interposition vein grafts and in human intravenous anastomoses.     

Argon laser-assisted anastomoses in medium-size vessels: one-year follow-up

Laser-assisted anastomosis of medium-size vessels can be performed with satisfactory short-term patency. This study was undertaken to evaluate patency and structural integrity up to 1 year. An argon laser was used to make bilateral femoral arteriovenous anastomoses in 12 dogs compared to conventional suture method in another 8 dogs. These anastomoses were evaluated for patency and aneurysm formation at 1 hour; 1, 2, 4, and 8 weeks; and 12 months after surgery. All anastomotic sites were patent and without aneurysmal change or luminal narrowing at all harvesting intervals. Histologic examination revealed that within 1 month laser anastomotic sites were almost completely healed and without intimal hyperplasia. In suture anastomoses, foreign-body reaction remained evident up to 1 year. Use of the argon laser for medium size vessel anastomoses resulted in excellent patency without aneurysm formation or intimal hyperplasia even in the long term. These data suggest promising clinical applications.     

Combined carotid arteries-aortic arch transplantation in rats: development of a new microsurgical model.

A new microsurgical model of combined carotid arteries-aortic arch transplantation in the rat is described. In this model, the combined carotid arteries-aortic arch were harvested and end-to-end anastomosed to the recipient's right carotid artery using a sleeve anastomosis technique. The total graft ischemia time and in particular the time required to perform the arterial anastomoses was significantly reduced. No surgical failure was encountered. Ten-day graft patency was 100% (15/15). Our study results demonstrated that the sleeve anastomosis technique for combined carotid arteries-aortic arch transplantation in the rat is fast and easy to perform and has a high rate of success.