Microvascular carotid end-to-end anastomosis with the argon laser

Ex vivo proof-of-concept of end-to-end scaffold-enhanced laser-assisted vascular anastomosis of porcine arteries

OBJECTIVE

The low welding strength of laser-assisted vascular anastomosis (LAVA) has hampered the clinical application of LAVA as an alternative to suture anastomosis. To improve welding strength, LAVA in combination with solder and polymeric scaffolds (ssLAVA) has been optimized in vitro. Currently, ssLAVA requires proof-of-concept in a physiologically representative ex vivo model before advancing to in vivo studies. This study therefore investigated the feasibility of ex vivo ssLAVA in medium-sized porcine arteries.

METHODS

Scaffolds composed of poly(ε-caprolactone) (PCL) or poly(lactic-co-glycolic acid) (PLGA) were impregnated with semisolid solder and placed over coapted aortic segments. ssLAVA was performed with a 670-nm diode laser. In the first substudy, the optimum number of laser spots was determined by bursting pressure analysis. The second substudy investigated the resilience of the welds in a Langendorf-type pulsatile pressure setup, monitoring the number of failed vessels. The type of failure (cohesive vs adhesive) was confirmed by electron microscopy, and thermal damage was assessed histologically. The third substudy compared breaking strength of aortic repairs made with PLGA and semisolid genipin solder (ssLAVR) to repairs made with BioGlue.

RESULTS

ssLAVA with 11 lasing spots and PLGA scaffold yielded the highest bursting pressure (923 ± 56 mm Hg vs 703 ± 96 mm Hg with PCL ssLAVA; P = .0002) and exhibited the fewest failures (20% vs 70% for PCL ssLAVA; P = .0218). The two failed PLGA ssLAVA arteries leaked at 19 and 22 hours, whereas the seven failed PCL ssLAVA arteries burst between 12 and 23 hours. PLGA anastomoses broke adhesively, whereas PCL welds failed cohesively. Both modalities exhibited full-thickness thermal damage. Repairs with PLGA scaffold yielded higher breaking strength than BioGlue repairs (323 ± 28 N/cm(2) vs 25 ± 4 N/cm(2), respectively; P = .0003).

CONCLUSIONS

PLGA ssLAVA yields greater anastomotic strength and fewer anastomotic failures than PCL ssLAVA. Aortic repairs with BioGlue were inferior to those produced with PLGA ssLAVR. The results demonstrate the feasibility of ssLAVA/R as an alternative method to suture anastomosis or tissue sealant. Further studies should focus on reducing thermal damage.

[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.

[Blood flow assessment with magnetic resonance imaging after 1.9 μm diode laser assisted arterial micronastomoses]

INTRODUCTION

The most important factor for successful free-flap transfer and replantations is a well-executed anastomosis. The aim of this study is to assess blood flow after laser assisted arterial microanastomosis (LAMA) using a 1.9 μm diode laser.

MATERIALS AND METHODS

LAMA was performed on a series of 10 carotidis on Wistar rats. Two 10/0 stay sutures and a standard laser tissue welding technique (λ: 1.9 μm; power: 120mW) were used. Similarly, a series of 10 conventional arterial anastomosis were performed (CSMA). For the two groups, contralateral non-operated carotidis were used as control. A positioning sequence, an anatomical sequence, an angiographic sequence and a flow sequence were performed 1 day after operation and then after 1, 4 and 8 weeks.

RESULTS

The arterial patency rate was 100% at the time of surgery. The mean clamping time was 7.2 min in the LAMA group compared to 10.7 min in the CSMA group. In the angiographic sequence, there were no aneurysms in both groups for all observation periods. At postoperative day 1, the mean loss of blood flow at the level of anastomosis in the LAMA group was 6% compared with 14% in the CSMA group. After 1, 4 and 8 weeks, there was an unhooking of the blood flow in the CSMA group: the loss of blood flow was 23%, 27% and 31% respectively, compared with 10%, 12% and 13% in the LAMA group. Moreover, one case of thrombosis was observed in the CSMA group after 1 week.

CONCLUSION

The flow-MRI emphasizes that 1.9 μm diode laser assisted microvascular anastomosis appears to be a consistent and reliable technique. These results show that 1.9 μm diode laser assisted microvascular anastomosis has potential for further development in the near future.

[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.

Carotid artery anastomosis with albumin solder and near infrared lasers: a comparative study

BACKGROUND AND OBJECTIVE

Laser tissue-welding has been used for anastomosis of carotid arteries. During welding, thermal injury sustained by the vessel walls should be minimized to prevent thrombosis. Two different types of lasers were used and effects on tissue damage were studied in vitro and in vivo.

STUDY DESIGN/MATERIALS AND METHODS

End-to-end anastomosis of dog carotid arteries (n = 10) was performed by using a human albumin solder (HAS) in conjunction with Nd:YAG or diode lasers (lambda = 1.32 microm and 1.9 microm, respectively). The arteries were evaluated for patency and evidence of histologic injury after 21 days. Another group of arteries was laser soldered in vitro to measure the intimal and adventitial temperatures by using thermocouples.

RESULTS

The arteries repaired with the diode laser sustained significantly less thermal damage than those repaired with Nd:YAG laser, both in vitro and in vivo. In particular, the intimal temperature was significantly lower (P < 0.05) for the diode than for the Nd:YAG repairs (approximately 35 degrees C and approximately 50 degrees C, respectively). In the latter group, the patency rate was 75%, but thrombosis occurred in 75% of the specimens at 21 days. All diode anastomoses were patent and thrombosis developed in only 17% of the arteries.

CONCLUSION

Use of the diode laser and albumin solders may provide a means to successfully repair carotid arteries with minimal thermal damage.

Laser welding for vascular anastomosis using albumin solder: an approach for MID-CAB

BACKGROUND AND OBJECTIVES

To improve minimally invasive direct coronary artery bypass surgery (MID-CAB), new techniques of vascular anastomosis that are faster and more reliable need to be developed.

STUDY DESIGN/MATERIALS AND METHODS

Common carotids in a canine model were transected and an end-to-end anastomosis was performed by using one of four techniques (1) continuous 6-0 polypropylene closure (suture; n=6), (2) vascular clip (VCS; n=6), laser welding using 50% albumin solder with (3) a 1.32-micro laser (1.32las; n=6), and (4) a 1.9-micro diode laser (1.9las; n=4). Times for anastomosis (TA) were compared between groups by t-test. Pressures at which anastomosis failed (leak point pressure, LPP) were determined and compared by analysis of variance.

RESULTS

TA was faster for 1.32las and 1.9las at 8.4+/-0.7 and 7.8+/-0.3 min, respectively, when compared with suture at 13.8+/-1.0 min (P=0.001, confidence interval [CI]-8.1, -2.6 for 1.32las and CI -8.9, -3.1 for 1.9las). There was no statistical difference between VCS (8.3+/-3.3 min) and any other group (P > 0.17). LPPs (mm Hg) were similar for all groups: 350+/-37 for 1.32las, 280+/-31 for 1.9las, 347+/-46 for suture, and 358+/-53 for VCS, P=0.68.

CONCLUSIONS

In this study, laser welding using 50% human albumin solder resulted in faster anastomotic times. Anastomoses were equivalent to conventional sutured anastomoses in failing at similar pressures. Laser welding using human albumin solder may be advantageous in improving coronary anastomoses during MID-CAB, but long-term anastomotic strength and histologic evaluation need to be investigated.

Sixty argon laser-assisted anastomoses in rats: macroscopic and histological studies

The present in vivo study was undertaken to evaluate the patency rate and histological appearance of 30 venous anastomoses and 30 carotid anastomoses in Wistar rats using a laser. An argon laser was used with the following parameters: power, 100 mW; time, 3 seconds; continuous mode; spot, 200 microns (fluence, 950 J/cm2; irradiance. 320 W/cm2). The macroscopic appearance and patency rate were evaluated at different postoperative intervals (30 days and 60 days). In the venous group, the patency rate was 100% with no saccular pseudo-aneurysm. In the arterial group, the patency rate was 93% with three saccular pseudo-aneurysms and two thromboses. Histological studies noted slight and transitory modifications of the media in the arterial group. In the venous group, the modifications appeared under the endothelium. Since the procedure was similar in both groups, the lack of pseudo-aneurysm formation in the venous group can be explained by a lower intravascular pressure.

Microarterial anastomosis using a noncontact diode laser versus a control study

A series of direct carotid end-to-end laser anastomosis vs. direct manual suture was carried out on a series of 70 Wistar rats (mean weight 260 g). Both common carotids (0.8-1.2 mm) were sectioned and repaired. The left side (n = 70) was submitted to laser-assisted microvascular anastomosis (LAMA) performed by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave) without chromophore. The right side (n = 70) underwent a control manual suture (CMA). The diode laser energy was delivered into a micromanipulator coupled to a Zeiss operating microscope with a focused spot of 300 microns in diameter. After placement of three 10.0 stitches for edge coaptation, the LAMA was achieved using laser shots (average 3) of 500 mW power, 4.5 s duration, and 700 W/cm2 irradiance each. The CMA was performed by means of six 10.0 stitches. The good vascular flow was confirmed by Doppler spectral analysis (n = 466) carried out from day 0 to day 90. Light and scanning electron microscopy (n = 82) showed that re-endothelialization after LAMA was gaining ground on day 3, whereas collagenous network developed in the media scar by day 10. In contrast, after CMA the arterial repair was delayed on day 20, inducing a media fibrotic scar. The patency rate was 93% in both anastomoses. The shorter operating time (13 min for LAMA vs. 22 min for CMA) and the noncontact laser technique are the main intraoperative advantages. The technical benefits of the diode laser are pointed out.

Determination of efficient parameters for argon laser-assisted anastomoses in rats: macroscopic, thermal, and histological evaluation

The aim of this study was to determine efficient parameters for an argon laser (spot diameter = 200 microns) to obtain and reproduce vessel anastomoses. It was performed in two groups of Wistar rats. In the first group (89 Laser impacts on 10 carotids), the fluence was continuously adjusted from 30 to 3,000 J/cm2 in order to determine efficient sets of parameters (power from 90-200 mW, pulse duration from 0.1 to 5 seconds, pulsed or continuous mode). In the second group, 30 end-to-end carotid anastomoses were performed. The results were evaluated by macroscopic thermal, and histological studies. The second group proved the efficiency of the selected parameters. Vessel welding was obtained with 100 mW, 3 seconds, continuous mode (fluence = 950 J/cm2, irradiance = 320 W/cm2) for a mean temperature of 77 degrees C corresponding to collagen denaturation. In the second group the patency rate was 93% (28/30) with three pseudo-aneurisms and two thromboses. Histological studies noted slight modifications of the media.

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.

Ultrastructural study of arterial wall repair after argon laser micro-anastomosis

A carotid end-to-end anastomosis was performed in 50 Wistar rats by means of a Coherent 900 argon laser. The vessel sealing was obtained with laser shots (average 19) of 300 mW power and 5-second duration, the beam being focused in a spot of 150 micron diameter (1,700 W/cm2). From day 0 to day 120, 25 specimens underwent semithin and electron microscopic examinations. The results showed the immediate sealing effect of the argon laser owing to protein denaturation and collagen fusion of the media and adventitia 100 micron in width. Re-endothelialization of the anastomotic line began by day 3, while myofibroblast proliferation was observed in the media by day 10. By day 20 media scar was still occupied by numerous myofibroblasts and surrounded by abundant collagen and elastic fibres. At long term the endothelial repair was complete and the anastomotic strength was assured by medial collagenous network.