Minimally occlusive laser vascular anastomosis (MOLVA): experimental study

Background  Temporary occlusion of an intracranial artery during microvascular anastomosis is a major risk factor in cerebrovascular surgery. A new laser vascular welding technique that minimizes the occlusion time of the recipient vessel has been developed and is described in this report. Method  A new minimally occlusive technique of end-to-side microvascular anastomosis was developed employing a diode laser in association with the application of a chromophore in our experimental model of double end-to-side anastomosis. The implantation of a vein graft on the patent carotid artery was obtained through the application of three interrupted sutures at each anastomotic site; the carotid was then clamped, two arteriotomies were performed, followed by the application of a fourth suture and of the laser welding procedure on each anastomosis. Monitoring of the temperature at the site of the anastomosis was introduced in order to control the welding technique. Findings  The time of the clamping of the carotid artery was 12 min to perform two end-to-side anastomoses (i.e., 6 min for each anastomosis). All bypasses were patent after a follow-up of 90 days and histological study confirmed good preservation of the vascular wall. Conclusions  Our laser-assisted technique of vascular anastomosis reduces the duration of the clamping of the recipient artery down to 6 min. This technique can minimize the risk of cerebral ischemia associated with occlusion of a recipient artery in intracranial bypass procedures, promoting an improved vascular healing process with a lower risk of thrombosis and occlusion.     

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.     

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.     

End-to-side and end-to-end vascular anastomoses with a carbon dioxide laser

This study was designed to compare anastomoses performed with a carbon dioxide laser and conventional anastomoses performed with 7-0 polypropylene suture. In each of 80 rabbits, the divided left carotid artery was anastomosed by a continuous suture technique and the right carotid was anastomosed with a carbon dioxide laser. In each of 40 additional rabbits, both end-to-end and end-to-side laser anastomoses were performed on the same carotid artery. The laser technique involved the placement of three stay sutures (end-to-end technique) or four stay sutures (end-to-side technique) of 7-0 polypropylene and an everting laser seal at a power level of 65 mW. The 1-year overall patency rate was 98% (78/80) in laser anastomoses, 79% (63/80) in suture anastomoses, and 95% (38/40) in combined end-to-end and end-to-side laser anastomoses. Microscopic findings in laser anastomoses demonstrated degeneration of collagen and protein in the adventitia and media, but much less intimal injury than in suture anastomoses, with reendothelialization beginning earlier (within 7 days after anastomosis as compared with 2 to 4 weeks). The tissue tensile strength at 1 hour was less in laser anastomoses than in suture anastomoses, but the laser anastomoses still withstood an intraluminal pressure load of 380 mm Hg. Laser anastomosis improved the microscopic and histologic appearance of the intimal layer, allowing for rapid early reendothelialization and resulting in excellent patency rates.     

The ring technique for end-to-side microvascular anastomosis

The ring technique for end-to-side microvascular anastomosis employs a resorbable polyglycolic acid ring to prevent stenosis and spasm at the anastomotic site. In 20 rats, the ring technique was compared with the conventional technique for constructing end-to-side anastomoses between the femoral (0.9-1.1 mm) and superficial epigastric (0.3-0.4 mm) arteries. The ring technique proved superior to the conventional end-to-side technique both in speed of execution and in patency at 3-4 weeks (100% vs 70%). Grossly and microscopically, the ring was completely resorbed at 3 wk.     

Arterial end-to-side anastomosis with the UNILINK system

A new technique for mechanical end-to-side anastomoses using the UNILINK anastomotic system is presented. The technique, based on the concept of vessel wall eversion over paired ring pins, is described as is a new device for vessel expansion. To evaluate the technique of end-to-side anastomosis, we detached the left renal artery in 18 rabbits and then reanastomosed them end-to-side to the aorta using the UNILINK anastomotic system. Renal blood flow was evaluated before and after anastomoses with a laser Doppler flowmeter. Animals were separated into three groups of 6 and were killed at 24 hours, 2 weeks, and 16 weeks, respectively. To evaluate the acute effects of vessel expansion, 7 additional rabbits underwent expansion of the aorta without subsequent anastomosis. All vessels were evaluated with light and scanning electron microscopy. A patency rate of 100% was achieved in the 18 animals; histological changes at the anastomotic site were comparable to those described previously for this mechanical anastomotic system. The animal model demonstrates that it is both technically possible and efficacious to perform end-to-side anastomoses of arteries with the UNILINK anastomotic system.     

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.     

End-to-side microvascular anastomosis using an external metal ring.

Enthusiasm for developing safer and faster anastomotic techniques and complementary devices continues. We report on a new microvascular end-to-side anastomosis technique using a silver ring around the anastomotic circumference. The purpose of this study was to compare the effectiveness of this technique with conventional end-to-side vessel anastomosis.Forty Sprague-Dawley rats were divided into two groups. Twenty rats were used to assess the external ring method in end-to-side anastomosis between carotid arteries and anterior jugular veins and the remaining 20 formed the control group with conventional end-to-end anastomosis.The anastomosis time was 26.4 min for standard suture anastomosis and 18.4 min for the external ring technique (P< 0.01). Patency was 95% with standard technique and 100% using the external ring (P> 0.05). The external ring technique of end-to-side microvascular anastomosis is a safe and reliable method and may reduce the operation time. Its clinical applicability should be further evaluated.     

Laser-assisted end-to-side anastomosis

The milliwatt CO2 laser was used to anastomose rat carotid arteries in an end-to-side fashion, and this technique was compared to the standard suture technique. Vessels were studied at two to six weeks. All anastomosis were patient and overall, there was a 78.6 percent rate of aneurysm formation in the laser cohort, compared with 7.1 percent with suture (p less than 0.001 Fisher exact). Vessels and aneurysm histology were similar to those previously reported for the end-to-end technique.     

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.     

Comparative study of microepineurial anastomoses with the use of CO2 laser and suture techniques in rat sciatic nerves: Part 1. Surgical technique, nerve action potentials, and morphological studies

The possibility of utilizing the CO2 laser for neural anastomoses was investigated in a rat sciatic nerve model. One nerve in each animal was acutely divided and anastomosed using 10-0 nylon epineurial sutures, while the opposite side was joined by "welding" the opposed nerve ends together with CO2 laser pulses. The surgical incisions were reexplored 60 days postoperatively, action potentials were recorded across the anastomoses, and the nerves were removed for light and electron microscopy. The operative patency rate in the suture group was 100%, compared to 87% in the laser group. Among those animals with bilaterally intact nerves, action potentials could be recorded across the anastomotic site in 78% of the sutured preparations and in 85% of nerves spot-welded with the CO2 laser. Morphological studies showed a greater degree of scar tissue formation and constriction in the anastomotic zone of the nerves joined by sutures than was present in laser-treated animals. We believe these preliminary observations suggest that the CO2 laser may have a role to play in peripheral nerve surgery. Further study of this technique is warranted.     

Use of vein-patch angioplasty in microvascular tissue transfers

Vein-patch angioplasty is a well-established technique in vascular surgery to reduce the critical narrowing of the arteriotomy site. In microsurgical end-to-side anastomosis, although the arteriotomy is not closed, it is not known if anastomosis through a sclerotic segment contributes to narrowing at the anastomotic site. It is certainly technically difficult to perform a microanastomosis with fine sutures through a sclerotic segment. Two cases are illustrated in which vein-patch angioplasties were successfully used for microsurgical anastomoses.     

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.     

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.     

Compliance in anastomoses with and without vein cuff interposition.

OBJECTIVE: to compare anastomotic compliance in end-to-side anastomoses with and without vein cuff interposition. Materials polytetrafluoroethylene graft to bovine carotid artery without (standard) and with vein interposition (Linton-patch and Miller-cuff). METHODS: zonewise compliance measurement of end-to-side anastomoses in an in-vitro circulation system. The zone most distal to the suture-line served as reference compliance. RESULTS: directly distal to the suture-line the compliance of the Linton-patch (5.6+/-1.6%/100 mmHg) and Miller-cuff anastomosis (5.2+/-1.1%/100 mmHg) more closely approached reference compliance (standard: 5.0+/-1.2, Linton-patch: 4.5+/-1.5, Miller-cuff: 4.9+/-1.0%/100 mmHg) than that of the standard anastomosis (7.9+/-3.0%/100 mmHg). The maximal compliance values of the Linton-patch (9.5+/-2.3%/100 mmHg) and Miller-cuff anastomoses (9.8+/-2.7%/100 mmHg) were significantly higher than that of the standard end-to-side anastomosis (7.9+/-3.0%/100 mmHg). However, maximal compliance was shifted from the zone directly distal to the suture line in the standard end-to-side anastomosis, to the vein cuff interposition in the Linton-patch and Miller-cuff anastomoses. CONCLUSION: the shift in maximal compliance to the wider portion of the anastomosis in the Miller-cuff and Linton-patch anastomoses may obviate reocclusion.     

Laser-assisted end-to-end BioWeld anastomosis in an ovine model

The BioWeld tube, an albumin-based exovascular stent, has been used for microsurgical anastomoses and compared to conventional sutures. The study presented investigated the potential of the BioWeld tube for vascular anastomosis in larger vessels. Laser-assisted BioWeld anastomoses were compared to conventional-sutured anatomoses of the carotid artery of Merino-x ewes. The BioWeld procedure resulted in 100% survival and 100% patency at 1 and 6 week post-operative periods, with no noticeable foreign body response. Sutured animals showed 100% survival and patency. The ischemic time for BioWeld anastomosis averaged 15 minutes compared with 10 minutes for sutures. This study indicates that the BioWeld tube is an easy to use anastomotic technique with equivalent success rates and comparable anastomotic times.     

Microvascular end-to-side arterial anastomosis using the Nd: YAG laser

End-to-side, laser-assisted vascular anastomosis (LAVA) using a Nd: YAG laser was successfully performed on rat carotid arteries. A midline neck incision allowed isolation and approximation of both carotid arteries in an end-to-side fashion using four 10-0 nylon stay sutures. The laser parameters used for vessel fusion were 0.3-second 5-W pulses at a spot size of 600 microns. Anastomoses were analyzed at various time intervals from 1 day to 6 months by angiogram and histological examination. The anastomotic patency was 86%. Aneurysm formation occurred in 23%. Histological examination revealed an acute/subacute transmural injury both at the anastomotic site and several hundred microns away, with delayed re-endothelialization and some attempt at muscular and elastic regeneration. Histological assessment of the aneurysms demonstrated a total loss of the internal elastic lamina and muscularis. A brief discussion comparing Nd: YAG LAVA to other LAVA techniques follows.     

Anastomosis of bypass grafts using a low-powered CO2 laser

The purpose of this study was to evaluate the feasibility of using a low-powered CO2 laser to perform end-to-side anastomoses of bypass grafts. The internal jugular veins of 13 domestic swine were removed and used as grafts to bypass their ligated carotid arteries. Each end of the vein graft was apposed to the artery with four to six temporary stay sutures, and a waveguide delivery CO2 laser with a power density of 900 mW/mm2 was used to perform the anastomoses, after which the sutures were removed. The animals were sacrificed postoperatively at five time intervals: 2 to 4 hours, 5 days, 1 month, 3 months, and 5 months. Of the 10 anastomoses studied at 2 to 4 hours, 70% were fully patent, none thrombosed, and 30% disrupted. Of the 16 anastomoses studied between 5 days and 5 months postoperatively, 88% were patent, 12% thrombosed, and none disrupted. None of the animals developed aneurysms at any stage of this investigation. Histologic analysis of acute studies revealed thermal damage such as charring of tissue, unraveling of the collagen fibrils, and the formation of microvacuoles. Within 3 months, the anastomotic sites showed localized healing with intimal fibromuscular proliferation and dense fibrous tissue. Good apposition of tissue was found to be of great importance in achieving patency of vessels in this procedure.     

Laser assisted microvascular anastomosis of arteries and veins: laser tissue welding

Using a milliwatt CO2 laser, a series of 160 arteries and 105 veins have been anastomosed in Wistar rats. Three stay sutures and a laser tissue welding technique were used. These were compared with a series of conventionally sutured vessels in terms of patency, speed and ease of procedure, and aneurysm formation. Patency rates of successful first time anastomoses are comparable with conventional suturing methods but the aneurysm rate is higher. Laser assisted anastomosis is faster to learn and perform than conventional suturing, but microsurgical skills are still needed. Despite the large number of variables the laser assisted technique has a high success rate, and work to minimise variables and optimise the laser parameters may improve these results.     

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