Comparative In Vitro Study of Tissue Welding Using a 808 nm Diode Laser and a Ho:YAG Laser

In vitro porcine arteries and veins have been welded end-to-end using either a 808 nm diode laser combined with an indocyanine green enhanced albumin solder, or with a continuous-wave (cw) Ho:YAG laser without biological solder. The vascular stumps were approached to each other over a coronary dilatation catheter in order to obtain a precise alignment and good coaptation. Standard histology revealed for both welding techniques lateral tissue damage between 2 and 3 mm caused by laser-induced heat. Good solder attachment to the tissue was observed by the use of a scanning electron microscope. The vessels soldered with the 808 nm diode laser using albumin solder showed considerably higher tensile strength (1 N compared to 0.3 N) than vessels welded exclusively by Ho:YAG laser radiation. In contrast, leaking pressure (350±200 mmHg) and bursting pressure (457±200 mmHg) were found to be independent of the welding technique used. This study demonstrates that fast (total welding time about 2–5 min), stable and tight microvascular anastomosis can be achieved with the use of a dye-enhanced albumin laser soldering technique and an ancillary coronary dilatation catheter. Paper received 10 August 2000; accepted after revision 3 January 2001.     

Laser ureteral anastomosis using intraluminal albumin stent in a porcine model

BACKGROUND AND OBJECTIVES: We compared ureteral anastomosis using a laser and intraluminal albumin stent with both conventional suturing and laser soldering techniques. STUDY DESIGN/MATERIALS AND METHODS: Twelve pigs underwent bilateral ureteral anastomoses (N = 24) using one of the three anastomotic methods: (1) laser welding with intraluminal albumin stent (N = 11); (2) with albumin solder (N = 8); and (3) conventional suturing (N = 5). Operative parameters, leakage rate, intrapelvic perfusion pressure, urography, and histology of the anastomoses were examined. RESULTS: Operative time for ureteral anastomosis in the stent and solder groups were significantly shorter than the suture group (means 370 seconds and 360 vs. 710 seconds, both P = 0.02). Leakage rate of the anastomoses was lower in the stent group (9%, 1/11) as compared to the solder group (25%, 2/8). The Whitaker test showed that the intrapelvic perfusion pressure elevated gradually after anastomosis and significantly increased at 4 weeks postoperatively in all three methods. Various degrees of hydronephrosis were also noticed in three groups after 4 weeks of surgery. CONCLUSIONS: Use of the intraluminal albumin stent increased the reliability of laser welding for ureteral anastomosis. The clinical significance of using this technique should be investigated further.     

Morphological analysis of microarterial media repair after 830 nm diode laser assisted end-to-end anastomosis: Comparison with conventional manual suture

A series of 240 diode laser assisted end-to-end microvascular anastomoses (LAMA) and conventional manual anastomoses (CMA) were performed in the left and right common carotid of Wistar rats, respectively. In comparison with the two anastomotic methods, optic and scanning electron microscopic examinations were achieved from Day 0 to Day 210, in order to clarify the mechanism of media repair after diode laser welding, especially the long-term results. In the LAMA group, the cut vessel edges were welded without obvious thermal necrosis after laser treatment. On Day 10, media repair was underlined by circular bulges corresponding to the folds of cut vessel endings brought together. Inflammatory cells were regularly scattered in the adventitia in the vicinity of the anastomotic site, and were gaining ground intensively in the media by Day 20. At this time, the parallel organization of elastic laminae disappeared while the collagen network developed. On Day 120, irregular elastic fibres aggregated in the anastomotic site. On Day 210, reconstituted elastic lamina was present. In the CMA group, on Day 20, fibrotic repair appeared between cut vessel edges, and the injury incorporated by sutures was important. The elastic laminae were not reconstituted by Day 210 in any case. This microscopic study proves that the long-term repair of diode LAMA facilitates media repair and prevents fibrotic scarring of the media.     

Intraluminal albumin stent assisted laser welding for ureteral anastomosis

BACKGROUND AND OBJECTIVES: The success of laser tissue welding or soldering depends on optimal laser settings, solder material, and tissue type and geometry. To develop a practical laser welding technique for ureteral repair, an intraluminal albumin stent was designed to enhance the welding effects on ureteral end to end anastomosis. STUDY DESIGN/MATERIALS AND METHODS: In vitro porcine ureters were anastomosed using an albumin stent alone, the albumin stent plus a solder, and the solder alone. All welding was performed with an 810-nm diode laser with either a continuous wave (1 W, CW) or two pulse modes (2 W, 3.3 Hz; 1 W, 5 Hz). Laser parameters, tensile strength (TS) and burst pressure (BP) of the ureteral anastomosis, and tissue thermal injury were measured. RESULTS: In the 2-W pulse mode, BP in the albumin stent plus solder group (mean 185 mmHg) and the stent only group (mean 133 mmHg) were significantly higher than the solder only group (mean 77 mmHg, P < 0.05). Laser ureteral anastomosis with the stent plus solder group at 1-W CW and 2-W pulse laser modes yielded the highest TS (mean 97, 82 g) and BP (mean 183, 185 mmHg). Among the three modes, the 1 W pulse delivered the lowest energy and yielded the lowest TS and BP in ureteral anastomosis. There was no significant difference in the thermal damage to the tissue among the modes and groups. CONCLUSIONS: Using the albumin stent increased the reliability of ureter end-to-end laser anastomosis. Further studies will be warranted in vivo and other tubular organs as well.     

Endoluminal laser-assisted vascular anastomosis—an in vivo study in a pig model

Microvascular surgery is time consuming and requires high expertise. Laser-assisted vascular anastomosis (LAVA) is a promising sutureless technique that has the potential to facilitate this procedure. In this study, we evaluate the handling of our soldering material and the 1-week patency rate in a porcine model. Six pigs were subjected to LAVA. For each pig, the saphenous artery on one side was transected while the contralateral side was used as control. A porous polycaprolactone scaffold soaked in 40% (w/w) bovine serum albumin solution in combination with 0.1% (w/w) indocyanine green was wrapped at the anastomosis site and at the control site. Both sides were then soldered with a diode laser coupled into a light diffuser fiber emitting radiation with a wavelength of 808 nm and a power of 2–2.2 W. Vessels were successfully soldered with a 100% immediate patency rate. The 1-week patency rate was 83% for the anastomoses versus 67% for the control side. Vessels irradiated for 80 to 90 s tended to maintain the highest patency rate. Macroscopically, there was no difference between the two sides. The patch was easy to handle provided that the environment could be kept dry. This study shows the potential and the limitations of endoluminal LAVA as a one-step procedure without the use of stay sutures. Further studies are needed to improve the soldering material, the long-term patency rate, and standardized irradiation parameters. The long-term effects of laser soldering on the vessel wall remain to be determined.     

Laser welded vesicourethral anastomosis in an in vivo canine model: a pilot study

PURPOSE: We evaluated laser welding as an alternative method of forming the vesicourethral anastomosis. MATERIALS AND METHODS: Eight dogs underwent open total prostatectomy, including 4 in which the vesicourethral anastomosis was formed by 830 nm. diode laser welding using a chromophore doped albumin solder and 3 or 4 support sutures. The remaining 4 anastomoses were conventionally formed using 8 interrupted sutures. Acute leakage was tested intraoperatively. The anastomosis of 1 animal per group was assessed on postoperative days 3, 5, 7 and 14 by radiography before sacrifice. Each anastomotic specimen was then tested for leak pressure and examined histologically. RESULTS: There were no leaks during intraoperative testing of laser welded or sutured anastomoses. On radiography there were no leaks in the laser welded group. In 1 control there was slight localized leakage. All anastomoses achieved physiological leak pressures of 70 mm. Hg or greater with 3 of the 4 in the laser welded group recording supraphysiological pressures of greater than 200 mm. Hg. While 3 of the 4 laser welded specimens showed evidence of muscle necrosis, there were no other differences in healing in the 2 groups. CONCLUSIONS: These short-term results suggest that diode laser welded vesicourethral anastomosis is feasible. This technique has the potential to simplify anastomotic formation in laparoscopic radical prostatectomy, shortening operative time. Diode laser welding in this small cohort created an immediate and ongoing watertight anastomosis and, therefore, it may also be an alternative in open radical prostatectomy cases. Further study is needed to assess long-term effects on healing.     

Albumin-genipin solder for laser tissue repair

BACKGROUND: Laser tissue soldering (LTS) is an alternative technique to suturing for tissue repair that avoids foreign body reaction and provides immediate sealing of the wound. One of the major drawbacks of LTS, however, is the weak tensile strength of the solder welds when compared to sutures. In this study, a crosslinking agent of low cytotoxicity was investigated for its ability to enhance the bond strength of albumin solders with sheep intestine. STUDY DESIGN/MATERIALS AND METHODS: Solder strips were welded onto rectangular sections of sheep small intestine using a diode laser. The laser delivered in continuous mode a power of 170 +/- 10 mW at lambda = 808 nm, through a multimode optical fiber (core size = 200 microm) to achieve a dose of 10.8 +/- 0.5 J/mg. The solder thickness and surface area were kept constant throughout the experiment (thickness = 0.15 +/- 0.01 mm, area = 12 +/- 1.2 mm2). The solder was composed of 62% bovine serum albumin (BSA), 0.38% genipin, 0.25% indocyanin green dye (IG), and water. Tissue welding was also performed with a BSA solder without genipin, as a control group. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were also cultured in extracted media from heat-denatured genipin solder to assess cell growth inhibition in a 48 hours period. RESULTS: The tensile strength of the genipin solder was doubled that of the BSA solder (0.21 +/- 0.04 N and 0.11 +/- 0.04 N, respectively; P = 10(-15) unpaired t-test, N = 30). Media extracted from crosslinked genipin solder showed negligible toxicity to fibroblast cells under the culture conditions examined here. CONCLUSION: Addition of a chemical crosslinking agent, such as genipin, significantly increased the tensile strength of adhesive-tissue bonds. A proposed mechanism for this enhanced bond strength is the synergistic action of mechanical adhesion with chemical crosslinking by genipin.     

Laser soldering of rat skin, using fiberoptic temperature controlled system

BACKGROUND AND OBJECTIVE: Laser soldering of tissues is based on the application of a biological solder on the approximated edges of a cut. Our goal was to use laser soldering for sealing cuts in skin under temperature feedback control and compare the results with ones obtained using standard sutures. STUDY DESIGN/MATERIALS AND METHODS: Albumin solder was applied onto the approximated edges of cuts created in rat skin. A fiberoptic system was used to deliver the radiation of a CO(2) laser, to heat a spot near the cut edges, and to control the temperature. Laser soldering was carried out, spot by spot, where the temperature at each spot was kept at 65-70 degrees C for 10 sec. RESULTS: The tensile strength of laser-soldered cuts was measured after 3-28 days postoperatively and was found comparable to that of sutured cuts. Histopathological studies showed no thermal damage and less inflammatory reaction than that caused by standard sutures (P = 0.04). CONCLUSIONS: Temperature controlled laser soldering of cuts in rat skin gave strong bonding. The cosmetic and histological results were very good, in comparison to those of standard sutures.     

Reinforcement of colonic anastomoses with a laser and dye-enhanced fibrinogen

The incidence of anastomotic leakage in colonic surgery is approximately 10%. We evaluated a technique of laser-fibrinogen reinforcement to strengthen experimental colonic anastomoses. The technique consisted of the topical application of indocyanine green dye-enhanced fibrinogen to the serosal surface of two-layer inverting anastomoses, followed by exposure with an 808-nm diode laser. In the 28 rabbits used for this study, mean bursting pressure at time 0 was 108 +/- 13 mm Hg in the group receiving anastomoses with sutures alone and 173 +/- 20 mm Hg in the group for which the sutured anastomosis was reinforced with laser-fibrinogen. The difference in bursting pressures between the two groups was statistically significant at time 0. However, at 1, 3, 5, and 7 days, the anastomosis became stronger in both groups and the difference in strength was reduced; the sutured group had more exceptionally weak (less than 110 mm Hg) bonds than the group treated by laser. Thus, laser-fibrinogen reinforcement significantly enhances the early strength of sutured colonic anastomoses. This technique may reduce the incidence of leakage during the first postoperative week and the associated complications in a clinical setting.     

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.     

Technical frontiers for the vascular surgeon: laser anastomotic welding and angioscopy-assisted intraluminal instrumentation

Innovations in therapy for peripheral vascular disease include laser vessel welding and angioscopy-assisted intraluminal laser instrumentation. Vascular tissue fusion by laser occurs at energy levels lower than those required to coagulate or vaporize. CO2, argon, and Nd:YAG (1.06 micron) lasers have all been reported to fuse anastomoses in microvessels, but adequate welding of larger veins and arteries (3 to 8 mm in diameter) has only been accomplished with the argon laser. Laser welds heal comparably to sutured wounds but do not have the chronic foreign body reaction and disorientation of elastin and collagen associated with sutures. Preliminary evidence suggests that argon laser-welded anastomoses have less intimal hyperplasia than sutured anastomoses. Laser welding may also be a useful adjunct for sealing intimal flaps during endarterectomy. Additional work is needed to determine the mechanism, optimal parameters, and wavelengths required for vascular tissue fusion by laser. Direct application of laser light intraluminally has thus far been associated with a high incidence of vessel perforation. Angioscopy-assisted delivery of a metal hot-tip probe shows promise for angioplasty of occluded medium-sized arteries and for valvulotomy in in situ vein bypasses.     

Canine colonic anastomoses reinforced with dye-enhanced fibrinogen and a diode laser

Summary Leakage from colonic anastomoses is a common cause of morbidity in patients recovering from bowel surgery. We evaluated a technique of laser-fibrinogen reinforcement to strengthen colonic anastomoses in a canine model. After creation of eight single-layer interrupted suture anastomoses in six dogs, indocyanine green-dye-enhanced fibrinogen was topically applied to the serosal surface and exposed to 808 mm diode laser energy. Immediately following colonic anastomosis, the mean leakage pressure was 137±22 mm Hg in the group (n=8) using sutures alone and 326±67 mm Hg (P<0.001) in the group (n=8) after the sutured anastomosis was reinforced with lasered-fibrinogen. On histological examination, no evidence of thermal injury to the tissue edges was noted and a layer of fibrinogen bridged the anastomotic gap. Laser dye-enhanced fibrinogen reinforcement significantly enhances the strength of sutured colonic anastomoses without causing appreciable thermal injury to the host tissues.     

Methylene blue based protein solder for vascular anastomoses: an in vitro burst pressure study

BACKGROUND AND OBJECTIVE: Attempts at sutureless anastomoses have used protein-based solders containing chromophores [Oz et al., J Vasc Surg 1990;11:718; Poppas et al., J Urol 1998150:1052] to enhance the strength of laser anastomoses. Reports have described the use of indocyanine green [Oz et al., Surg Forum 1989;316.], fuschin, and fluorescein isothiocyanate as chromophores [Chuck et al. , Lasers Surg Med 1989;9:471; Vance et al., Lasers Med Sci 1988;3:219]. Methylene blue (MB) is a chromophore with absorption peaks in the 600-700 nm region whose use has not been reported in laser-assisted vascular anastomoses. Therefore, we set out to produce and characterise a MB-containing protein solder. The absorption and burst pressure characteristics have been investigated and described as well as a brief review of the chemical and biological properties of MB. STUDY DESIGN/MATERIALS AND METHODS: The MB and porcine serum albumin (PSA)-based solder was produced and used to form end-to-end anastomoses in porcine splenic arteries. The solder was activated using a laser diode emitting at 670 nm. The burst pressures of the anastomoses were tested, and the results analysed as a function of MB concentration and absorption. In addition, the relationship between MB concentration and absorption was examined. RESULTS: A dose-response relationship was found between the measured absorption of the solder and the burst pressure of the anastomoses formed. Burst pressures exceeding physiological levels were found. Changes in MB concentration revealed a marked negative deviation from Beer's law at 670 nm, owing to the monomer-dimer-trimer equilibria. CONCLUSION: PSA with MB solder is able to form high-quality end-to-end anastomoses, with immediate burst pressure profiles similar to those previously described for sutured [Quigley et al., Microsurgery 1985;6:229], lasered [Quigley et al., Microsurgery 1985;6:229], and soldered anastomoses [Small et al., J Clin Laser Med Surg 1997;15:205]. The relationship between burst pressure strength and chromophore absorption is discussed.     

Laser tissue soldering for hypospadias repair: results of a controlled prospective clinical trial

PURPOSE: Laser tissue soldering has been shown to provide safe and effective tissue closure by creating an immediate leak-free anastomosis with minimal scar formation. We compared the results of laser tissue soldering and conventional suturing for hypospadias repair. MATERIALS AND METHODS: A consecutive group of 138 boys 4 months to 8 years old (mean age 15 months) was divided into a standard suturing (84) and a sutureless laser (54) hypospadias repair group. Urethral repair was defined as simple (Thiersch-Duplay or Snodgrass) and complex (onlay island flap or tube) in 101 and 37 cases, respectively. Laser tissue soldering was performed with 50% human albumin solder doped with 2.5 mg./ml. indocyanine green dye using an 808 nm. diode laser at 0.5 W. In the laser group sutures were used for tissue alignment only. At surgery neourethral and penile length, operative time for neourethral construction and the number of sutures or throws were measured. Postoperatively patients were examined for complications of wound healing, stricture or fistula. RESULTS: Mean patient age, urethral defect severity, type of repair, neourethral length and stenting time plus or minus standard error of mean were not significantly different in the 2 groups. Mean operative time was a fifth as long for laser tissue soldering in simple and complex hypospadias repair compared to controls (1.5 +/- 0.1 and 5.1 +/- 0.3 versus 8.5 +/- 0.8 and 26.7 +/- 1.7 minutes, respectively, p <0.001). The mean number of sutures used for tissue alignment in the laser group for simple and complex repair was significantly less than in controls (3.0 +/- 0.2 and 8.2 +/- 0.6 versus 8.5 +/- 0.8 and 23.2 +/- 1.5, respectively, p <0.001). All patients were followed a mean of 12 months (minimum 6, maximum 22). The complication rate was 4.7% in the laser group and 10.7% in controls with fistula in 2 of 54 cases, and fistula and meatal stenosis in 7 and 2 of 84, respectively. CONCLUSIONS: These preliminary results indicate that laser tissue soldering for hypospadias repair may be performed in almost sutureless fashion and more rapidly than conventional suturing. The ease of the laser technique and the lower complication rate in the laser group indicate that laser tissue soldering is an acceptable means of tissue closure in hypospadias repair.     

Comparison of laser vascular welding,interrupted sutures,and continuous sutures in growing vascular anastomoses

Background and Objectives: The argon laser-assisted vascular anastomosis may solve the problems of conventional sutured anastomosis, such as vascular stenosis and arrest of growth owing to a foreign-body reaction to suture material. Study Design/Materials and Methods: Twelve argon laser-assisted vascular anastomoses, seven conventional anastomoses with interrupted sutures, and five conventional anastomoses with continuous sutures were performed in 12 young mongrel dogs. Results: Five months later, the external diameter at the anastomosis had increased 70.5% in the laser group, 67.0% in the interrupted suture group, and 22.9% in the continuous suture group. Histological examination of the laser-assisted anastomoses showed almost complete healing, with no granulomatous response around the anastomotic site. In the interrupted suture group, marked scaring and foreign body reactions were observed on the vessel wall at the site of the anastomosis. The continuous suture group showed more remarkable disorientation of the vascular layer and intimal hyperplasia than the interrupted suture group. Conclusion: Vascular anastomosis using the argon laser offers advantages over the conventional procedure in growing vessels.     

Laser-Fused Biologic Vascular Graft Anastomoses

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n;eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance. The technique may provide a method to limit development of anastomotic stenosis by eliminating the foreign body reaction. In addition, the canine arteriovenous model used in these experiments develops aggressive intimal lesions at the venous anastomosis within weeks and may be used to evaluate the effect of anastomotic technique on the development of this lesion.     

Optimal parameters for laser tissue soldering: II. Premixed versus separate dye-solder techniques

BACKGROUND AND OBJECTIVE: Laser tissue soldering by using an indocyanine green (ICG)-doped protein solder applied topically to the tissue surface and denatured with a diode laser was investigated in Part I of this study. The depth of light absorption was predominantly determined by the concentration of the ICG dye added to the solder. This study builds on that work with an in vitro investigation of the effects of limiting the zone of heat generation to the solder-tissue interface to determine whether more stable solder-tissue fusion can be achieved. STUDY DESIGN/MATERIALS AND METHODS: An alternative laser tissue soldering technique was investigated, which increased light absorption at the vital solder-tissue interface. A thin layer of ICG dye was smeared over the surface to be treated, the protein solder was then placed directly on top of the dye, and the solder was denatured with an 808-nm diode laser. Because laser light at approximately 800 nm is absorbed primarily by the ICG dye, this thin layer of ICG solution restricted the heat source to the space between the solder and the tissue surfaces. A tensile strength analysis was conducted to compare the separate dye-solder technique with conventional techniques of laser tissue soldering for which a premixed dye-solder is applied directly to the tissue surface. The effect of hydration on bond stability of repairs formed by using both techniques was also investigated using tensile strength and scanning electron microscopy analysis. RESULTS: Equivalent results in terms of tensile strength were obtained for the premixed dye-solder technique using protein solders containing 0.25 mg/ml ICG (liquid solder, 220 +/- 35 N/cm(2); solid solder, 602 +/- 32 N/cm(2)) and for the separate dye-solder technique (liquid solder, 228 +/- 41 N/cm(2); solid solder, 578 +/- 29 N/cm(2)). The tensile strength of native bovine thoracic aorta was 596 +/- 31 N/cm(2). Repairs created by using the separate dye-solder technique were more stable during hydration than their premixed dye-solder counterparts. The conventional premixed dye-solder was simpler and approximately twice as fast to apply. The separate dye-solder technique, however, increased the shelf-life of the solder, because the dye was mixed at the time of the experiment, thus conserving its spectral absorbency properties. CONCLUSION: Two laser-assisted tissue soldering techniques have been evaluated for repairing aorta incisions in vitro. The advantages and disadvantages of each of these techniques are discussed.     

Microvascular anastomosis using a new diode laser system with a contact probe

The aim of the present study was to demonstrate the usefulness of our newly produced diode laser device (an 830-nm output of 190 mW CW) for microvascular end-to-end anastomoses. In the device, diode laser energy is delivered to a contact ceramic tip with a 200-microns diameter output end. Its wavelength is 830 nm and its power 60 mW. This device is small (30 x 25 x 10 cm), lightweight (gross weight 3kg), and easy to manipulate. Compared with conventional microvascular suture anastomosis (CMSA), the time required for the laser-assisted vascular anastomoses (LAVA) was reduced by almost half. Anastomosed portions of both methods were examined 1, 2, 4, 12, and 24 weeks later for patency and aneurysm formation. The patency rate and incidence of aneurysmal formation were the same in both groups. Histological examination revealed that LAVA is superior to CMSA in the smoothness of the inner surface, less inflammatory reaction, and normal collagen and elastic reorientation. The tensile strength and bursting pressure measured immediately after anastomosis demonstrated no significant difference between the two groups. It was concluded that this diode laser contact method may be clinically useful for microvascular surgery.     

Methylene blue soldered microvascular anastomoses in vivo.

OBJECTIVES: solders containing chromophores and proteins enhance the strength of lasered anastomoses. Methylene blue (MB) solder anastomoses in vitro are strong but no in vivo work has been reported. We used an MB solder in vivo and studied the effects of two laser powers on patency and histological appearance. DESIGN, MATERIALS AND METHODS: two groups of 15 rabbits had unilateral end-to-end carotid anastomoses (1.5-2.0 mm) formed using three stay sutures and MB solder. Group 1 anastomoses were formed at 5.7 Wcm(-1) and Group 2 at 2.8 Wcm(-1). The vessels were examined at various points by necropsy for patency and gross macroscopic appearance, with subsequent histological examination. RESULTS: group 2 showed patency of 93.3% v 0% ( p<0.001) endothelialisation of 100% v 26.6% ( p<0.001), giant cell formation 0% v 40.0% ( p<0.01), but stenosis was not significantly different (0% v 13.3% p=0.06). Group 2 showed a higher rate of intimal hyperplasia (IH) (66.6% v 20.0% p<0.05) but neither group exhibited thermal injury or aneurysm formation. CONCLUSIONS: laser soldered microvascular anastomoses were formed in vessels of 1.5-2.0 mm with a high degree of patency. A relationship appears to exist between laser power and anastomotic patency. Methylene blue fading has the potential to act as a switch against over exposure and a visual indicator of solder activation.     

A comparison of para-anastomotic compliance profiles after vascular anastomosis: nonpenetrating clips versus standard sutures

PURPOSE: Anastomotic compliance is an important predictive factor for long-term patency of small diameter vascular reconstruction. In this experimental study we compare the compliance of continuous and interrupted sutured vascular anastomoses with those using nonpenetrating clips. METHODS: Both common carotid arteries in nine goats (average weight, 57 +/- 5.7 kg) were transected, and end-to-end anastomoses were constructed with nonpenetrating clips or polypropylene sutures. The latter were applied with both interrupted and continuous techniques. Intraluminal pressure was measured with a Millar Mikro-tip transducer, and vessel wall motion was determined with duplex ultrasound equipped with an echo-locked wall-tracking system. Diametrical compliance was determined. Environmental scanning electron microscopy was performed on explanted anastomoses. RESULTS: There was a reduction in anastomotic compliance and associated proximal and distal para-anastomotic hypercompliant zones with the use of all techniques. However, compliance loss was significantly less in those anastomoses with clips and interrupted sutures when compared with continuous suture (P <.001). Furthermore, the total compliance mismatch across anastomoses with continuous sutures was significantly greater than those with clips or interrupted sutures (P <.05). The mean time for constructing clipped anastomoses was 5.7 +/- 1.4 minutes, which was significantly less than either continuous (P <.0001) or interrupted sutures (P <.0001). Furthermore, environmental scanning electron microscopy demonstrated minimal intimal damage with good intimal apposition in the clip group. CONCLUSION: Anastomoses performed with nonpenetrating clips resulted in improved para-anastomotic compliance profiles and reduced intimal damage when compared with those with polypropylene sutures. These benefits may enhance long-term graft patency by reducing the risk of anastomotic intimal hyperplasia.