Microarterial anastomosis using a noncontact diode laser versus a control study

[Thirty years of laser-assisted microvascular anastomosis (LAMA): what are the clinical perspectives?]

INTRODUCTION

Since the first studies by Jain and Gorisch (1979), laser-assisted anastomoses have been steadily developed to a stage where clinical use is within reach. The laser-assisted vascular microanastomosis (LAMA) procedure is performed more quickly than conventional anastomosis, the surgically induced vessel damage is limited, and reduced bleeding after unclamping is observed.

MATERIAL AND METHODS

A Medline literature search, for the January 1979 to February 2010 period, was performed to review articles focusing on the LAMA technique.

RESULTS

The search yielded a total of 354 publications, of which 87 were relevant: 82 were animal series and five clinical studies. Microsurgical techniques and principal characteristics of LAMA in patients are the focus of the analysis. This study discusses the technological innovations and new orientations in laser welding.

CONCLUSION

The first two clinical series using the 1.9-μm diode laser appear promising. Technical innovation will most likely lead to greater ease of use of the laser handpiece in the operating room.

[Historical review and future orientations of the conventional vascular microanastomoses]

Microvascular surgery has become an important method for reconstructing surgical defects due to trauma, tumors or after burn. The most important factor for successful free flap transfer is a well-executed anastomosis. The time needed to perform the anastomosis and the failure rate are not negligible despite the high level of operator's experience. During the history, many alternatives were tried to help the microsurgeon and to reduce the complications. A Medline literature search was performed to find articles dealing with non-suture methods of microvascular anastomosis. Many historical books were also included. The non-suture techniques can be divided into four groups based on the used mechanism of sutures: double intubation including tubes and stents, intubation-eversion including simple rings, double eversion including staples and double rings, and wall adjustement with adhesives or laser. All these techniques were able to produce a faster and easier microvascular anastomosis. Nevertheless, disadvantages of the suturless techniques include toxicity, high cost, leakage or aneurysm formation. More refinement is needed before their widespread adoption. Thus, laser-assisted microvascular anastomosis using 1,9 μm diode laser appeared to be a safe and reliable help for the microsurgeon and may be further developed in the near future.

Outcomes after 1.9-microm diode laser-assisted anastomosis in reconstructive microsurgery: results in 27 patients

BACKGROUND

Microvascular surgery has become an important method for reconstructing surgical defects resulting from trauma, tumors, or burns. The most important factor for successful free flap transfer is a well-executed anastomosis. This study was performed to review the authors' experience with a 1.9-microm diode laser in microsurgery, with special attention to outcomes and performance of the technique.

METHODS

Between January of 2005 and December of 2007, 27 patients underwent microsurgery with a 1.9-microm diode laser at the authors' institute. The patients had a mean age of 31 years (range, 2 to 59 years); 14 patients were women and 13 patients were men. This technique was used for digital replantations (n = 2) and for free flap transfer (n = 27). Causes of the defects were trauma (n = 14), tumor (n = 9), congenital (n = 2), burn (n = 1), infection (n = 1), arthritis (n = 1), and dog bite (n = 1). Laser-assisted microvascular anastomosis was performed with a 1.9-microm diode laser after placement of equidistant stitches. The following parameters were used: spot size, 400 microm; power, 125 mW; time depending on vessel size (0.8 to 1.8 mm); and fluence varying from 70 to 200 J/cm.

RESULTS

Three surgical revisions following hematoma and one rupture of the arterial anastomosis leading to a free deep inferior epigastric perforator flap necrosis resulting from high-dose radiotherapy before surgery occurred after laser-assisted microvascular anastomosis, accounting for an overall success rate of 96.6 percent.

CONCLUSION

This study reports the numerous benefits of the technique: easier performance of vascular anastomosis with difficult access, decrease of reperfusion bleeding and complications, and a short learning curve.

Microvascular anastomosis using a photochemical tissue bonding technique

BACKGROUND AND OBJECTIVES

Photochemical tissue bonding (PTB) combines photoactive dyes with visible light to create fluid-tight seals between tissue surfaces without causing collateral thermal damage. The potential of PTB to improve outcomes over standard of care microsurgical reanastomoses of blood vessels in ex vivo and in vivo models was evaluated.

STUDY DESIGN

The mechanical strength and integrity of PTB and standard microsurgical suture repairs in ex vivo porcine brachial arteries (n = 10) were compared using hydrostatic testing of leak point pressure (LPP). Femoral artery repair in vivo was measured in Sprague-Dawley rats using either standard microvascular sutures (n = 20) or PTB (n = 20). Patency was evaluated at 6 hours (n = 10) and 8 weeks post-repair (n = 10) for each group.

RESULTS

PTB produced significantly higher LPPs (1,100+/- 150 mmHg) than suture repair (350+/-40 mmHg, P<0.001) in an ex vivo study. In an in vivo study all femoral arteries in both suture and PTB repair groups were patent at 6 hours post-repair. At 8 weeks post-repair the patency rate was 80% for both groups. No evidence of aneurysm formation was seen in either group and bleeding was absent from the repair site in the PTB-treated vessels, in contrast to the suture repair group.

CONCLUSION

PTB is a feasible microvascular repair technique that results in an immediate, mechanically robust bond with short- and long-term patency rates equal to those for standard suture repair.

25 Years of Laser Assisted Vascular Anastomosis (LAVA): What Have We Learned?

OBJECTIVES

Laser assisted vascular anastomosis (LAVA) has been developed to a stage where clinical use is within reach. Advantages of LAVA are minimal vessel damage, faster operation and the potential for minimally invasive application.

DESIGN

A Medline literature search was performed on vessel welding combined with cross-referencing.

RESULTS

Four different lasers have mostly been used for LAVA, always in combination with stay sutures. The CO(2) laser has only been used in the early period. Without solder, mean leaking point pressures (LPP) of 754 mmHg (n=75) were obtained, only slightly lower than in suture controls (LPP=915 mmHg, n=82). At follow-up the percentage of aneurysms was high (overall 12% in n=486). Although Argon LAVA showed moderate success (LPP=146 mmHg, n=125), the first clinical application has been successfully performed. Diode LAVA in combination with solder and dye resulted in an acceptable LPP of 409 mmHg (n=163) in larger vessels, with a low incidence of aneurysm formation (1% in n=107).

CONCLUSION

At present the diode laser is the most popular. Solder developments resulted in stronger welds and might make stay sutures redundant. The combination of CO(2) laser and solders has not been evaluated and deserves further investigation.

Morphologic changes in collagen fibers after 830 nm diode laser welding

BACKGROUND AND OBJECTIVE

The mechanism of laser tissue welding is elusive, but collagen transitions are somehow involved. Collagen fiber modifications observed after 830 nm diode laser welding are presented in this study.

STUDY DESIGN/MATERIALS AND METHODS

A 830 nm diode laser assisted longitudinal aortorrhaphy was performed on 37 Wistar rats, with shots of 0.5 W in power, 8 sec in duration and 250 W/cm2 in irradiance. Energy utilized ranged from 400-550 J/ mm2 for 1 cm-length of anastomosis. After laser welding, histological modifications in collagen fibers were observed through optic, scanning electron, and electron microscopic examination.

RESULTS

After laser welding, collagen fibers lost a proportion of birefringence. Under electron microscope, the different changes in collagen fibers were visualized being either fused, "roped," swollen, or dissolved, surrounded by normal ones situated in the same zone.

CONCLUSION

These data suggest that diode laser heating denatured part of the collagenic fibers, and that these morphologic changes play an important role in laser welding.

Quantitative changes in collagen levels following 830-nm diode laser welding

BACKGROUND AND OBJECTIVE

The actual mechanism by which laser irradiation welds tissue is presently unknown; however, collagen is a major constituent of tissue welded by laser irradiation.

STUDY DESIGN/MATERIALS AND METHODS

Collagen was extracted from the abdominal aorta of Wistar rats by acetic acid extraction and repeated pepsin digestion after tissue welding (254 W/cm2) by using an 830-nm diode laser. The collagen levels were determined by using the Sircol Collagen Assay (Biocolor, Northern Ireland).

RESULTS

Compared with untreated aorta, the collagen content of the treated vessel was obvious decreased (P < 0.001) immediately after laser irradiation. Levels then increased by day 3, with a peak at day 10 (P < 0.002). The collagen content returned to normal levels on day 30 and remained at this level throughout the rest of the experimental period.

CONCLUSION

These results suggest that a proportion of the collagen molecules in the vessel are denatured by the heat of the laser. Collagen synthesis is stimulated during the healing process after laser welding with the parameters used in the present study.

A comparison of Cunyite and Fosterite NIR tunable laser tissue welding using native collagen fluorescence imaging

OBJECTIVE

To evaluate the technique of native collagen fluorescence imaging for assessing the extent of welded areas for tissues exposed to different near-infrared (NIR) laser wavelengths.

BACKGROUND

Native fluorescence imaging may be used to identify the distribution of collagen and elastin in tissues. Our past work demonstrated that different welding strengths were obtained under the same laser power conditions using different NIR wavelengths. The role of collagen in tissue welding experiments is not well understood.

METHODS

Two new NIR tunable lasers were used to weld canine skin. The welded areas on the surface and in cross sections were analyzed by measuring the spatial distribution of native collagen fluorescence at 380 nm excited by 340 nm radiation.

RESULTS

The results show that native collagen fluorescence imaging is a useful technique for analyzing the extent of tissue welds produced under a range of laser exposures. Fluorescence imaging reveals the depth of laser interaction with the tissue as well as evaluating collateral damage to the tissue surface. The welded volume obtained in skin using Cunyite laser exposure at 1,430 nm is deeper than that produced with Forsterite laser exposure at 1,250 nm. The post welded tensile strength for the same power density is greater for the Cunyite lasers. Ablated tissue on the surface is more prevalent with Forsterite laser welding at 1,250 nm than with Cunyite at 1,430 nm.

CONCLUSION

Native collagen fluorescence can distinguish between tissue welds that have been produced by different NIR wavelengths. Tissue welding using 1,430 nm radiation is more effective than that using 1,250 nm.

Fluorescence spectroscopic imaging to detect changes in collagen and elastin following laser tissue welding

OBJECTIVE

A study was performed to evaluate the use of native fluorescence imaging to detect in situ molecular changes.

SUMMARY BACKGROUND DATA

There is no ideal noninvasive method to monitor molecular changes in a local region at a laser weld joint without removing a section of tissue for histological examination.

METHODS

Two sections of animal skin were welded together border to border using a Ti:sapphire laser beam (800 nm). Fluorescence imaging was performed on the cross section of the welded site at specific emission wavelengths (lambda c) for collagen at 380 nm and for elastin at 450 nm using excitation wavelengths (lambda e) of 340 nm, and 380 nm, respectively.

RESULTS

A reduction of the collagen and elastin emission was observed in the fluorescence images of the welded region. These results were confirmed with histology using picrosirius red F3BA under polarized light and orcein stains.

CONCLUSION

Optical spectroscopic imaging offers a new noninvasive detecting method for microscopic evaluation of laser tissue welding.

Mechanism of aneurysm formation after 830-nm diode-laser-assisted microarterial anastomosis

OBJECTIVE

The process of aneurysm formation after laser welding is described.

SUMMARY BACKGROUND DATA

The mechanism of aneurysm formation after laser-assisted microarterial anastomosis is presently unclear.

METHODS

A series of 830-nm diode-laser-assisted longitudinal aortorrhophy with a condition of 400 to 500 J/mm2 for 1 cm length of anastomosis versus conventional manual anastomoses were performed in 90 Wistar rats. To compare this technique with normal media process, a histologic examination of aneurysm formation was conducted.

RESULTS AND CONCLUSIONS

The results show that there are two important factors that cause aneurysm formation after laser-assisted anastomosis: 1) the vessel wall is damaged by laser heating; 2) proliferation of collagen fiber at the adventitia is absent during media reconstruction.

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.