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.     

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.     

Low dose ASA (4 mg/kg) peroperatively does not prevent in vivo platelet accumulation at microarterial anastomotic sites. An experimental study in the rabbit

Twenty microarterial end-to-end anastomoses were performed on the central arteries of the ears in 12 rabbits divided into two groups: Group A (10 anastomoses) served as control and Group B (10 anastomoses) was treated with 4 mg ASA per kg b.w. given as a single intraaortical dose 5 min prior to infusion of 32P-labelled platelets. Two hours later blood-flow was reestablished after end-to-end anastomoses. Anastomotic bleeding-times, qualitative and quantitative differences in platelet accumulation and patency were registered. In addition, platelet aggregability and thromboxane production were studied in 3 rabbits. The bleeding-times (median and quartiles) in group A were 3(+0)-2 min and in group B 3(+2)-0 min. In vivo accumulation of 32P-labelled platelets was somewhat increased initially (p less than 0.05) in the ASA group. Poor patency was registered in two vessels, one in each group, all other vessels having good patency. Aspirin peroperatively in low doses (4 mg/kg) did not markedly affect bleeding-times or patency rates in microarterial anastomoses, but platelet accumulation in vivo was initially increased. The radioactivity values decreased with time in all aspirin cases but only in 50% of the control group vessels, suggesting efficient platelet disaggregation/fibrinolysis. This might favour the view that PGI2 production in the endothelium recovers more rapidly than the pro-aggregatory mechanisms affected by ASA. ASA-treatment led to almost complete inhibition of thromboxane production for at least four hours, but, despite this, a moderate decrease in platelet aggregability occurred only when collagen was used as stimulant.     

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.     

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 μm (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. © 1995 Wiley-Liss, Inc.     

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.     

Heat-induced tissue fusion for microvascular anastomosis

Laser tissue welding was compared with a crude method of bipolar coagulator-generated heat application for achieving the same heat-induced welding effect in rat microarterial anastomoses. Rat femoral arteries were anastomosed with three triangulated stay sutures and subsequent laser welding or bipolar coagulator application between each pair of stitches. Control (non-welded) vessels received nine stitches placed circumferentially. Laser-welded vessel patency at 1 or more days postoperatively was 90% (65/72) for vessels treated with 0.1-second laser pulses, not significantly different from controls (100%; 16/16) or coagulator-welded anastomoses (88%; 14/16). Pseudoaneurysm rates were higher in the welded vessels (9% and 14% for laser- and coagulator-treated vessels, respectively) than in controls (0%). Histologic and electron microscopic evaluation revealed good healing with no apparent differences between laser- and coagulator-welded repairs. These findings suggest that laser application for microvascular tissue welding is similar to poorly controlled welding with a bipolar coagulator. © 1997 Wiley-Liss, Inc. MICROSURGERY 17:198–208 1996     

Laser-assisted microsurgical anastomosis

A low power carbon dioxide laser was used to perform 212 end-to-end laser-assisted microvascular anastomoses (LAMA) of femoral arteries (mean diameter, 1.2 mm) in Sprague-Dawley rats. Eighty-two conventional microvascular suture anastomoses (CMSA) utilizing 10-0 monofilament interrupted sutures were done for comparison of techniques and wound healing. The mean duration of each anastomosis procedure was 16 minutes for the LAMA repairs, compared to an average of 27 minutes for the CMSA repairs (P less than 0.05). All anastomoses were patent at the completion of the procedure. Each laser-assisted anastomosis required an average of seven intermittent laser exposures of 0.1 to 0.3 seconds each with approximately 80 mW of CO2 (wavelength = 10.6 micron) radiation at a spot size of 150 micron. A patency rate of 95% was obtained on the LAMA vessels (202 of 212) compared to 96% for the CMSA repairs (79 of 82). A total of 14 aneurysms were noted in the LAMA group (7%) compared to 11 in the CMSA (13%). All aneurysms were in patent vessels. Histological analysis indicates that the progression of wound healing of LAMA and CMSA anastomoses follows similar paths chronologically and morphologically with increased scar tissue formation around the suture. Scanning electron microscopy confirms the comparable luminal healing of the LAMA and CMSA vessels, with complete reendothelialization occurring by 3 weeks postoperatively. The tensile strength of the LAMA repair, although low immediately after operation, is comparable to that of the intact artery at 21 days. These findings suggest that a low energy carbon dioxide microsurgical laser has potential beneficial clinical application for anastomosis of small vessels.     

Vascular anastomoses with laser energy

Laser-assisted arterial and venous anastomoses are now feasible. A microscope-guided CO2 laser was used to deliver 60 to 100 mW to anastomose end to end 44 rabbit carotid arteries (1.5 to 2.0 mm) and 27 rabbit vena cavae (4 to 6 mm). These were compared with control arteries repaired with interrupted suture technique. Anastomoses were examined from between 24 hours and 19 weeks. Laser carotid anastomoses yielded 93% patency (41 of 44) and 9% aneurysms (4 of 44), whereas hand-sewn carotid anastomoses produced 91% patency (40 of 44) and no aneurysms. In the vena cava, 26 of 27 laser anastomoses were patent (96%) compared with 19 of 20 (95%) sutured controls. Venous aneurysmal dilatation was seen in 2 of 27 laser (7%) and in 3 of 20 (15%) hand-sewn anastomoses. Histologic examination of laser-assisted anastomoses showed local full-thickness thermal injury. Repair was by fibroblast and myofibroblast proliferation, and luminal cell coverage was complete by 14 days in both laser and sutured repairs. Laser arterial and venous anastomoses are attractive because of their simplicity and rapidity of performance. Their patency is comparable to sutured anastomoses, but arterial aneurysms remain a hazard despite use of extremely low laser energy.     

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.     

Intraluminal laser light source and external solder: in vivo evaluation of a new technique for microvascular anastomosis

BACKGROUND AND OBJECTIVES: Current laser-assisted end-to-end anastomoses are performed by irradiating the vessel wall from outside after additional fixation with three to six sutures. These sutures are needed to provide adequate approximation of the vessel stumps. We present a new laser soldering technique that is based on an intraluminal laser light source centered in a balloon catheter, and external application of a solder. This technique was applied in vivo in order to test its feasibility under clinical conditions. STUDY DESIGN/MATERIALS AND METHODS: Seven white pigs were treated with a total of fourteen end-to-end laser-anastomoses of their saphenous arteries having outer diameters of 2 mm. The vessels were stented over an intraluminal balloon catheter, which was maximally dilated and which allowed for a precise approximation of the vascular stumps. An 808 nm diode laser was coupled into a specially designed optical fiber producing a 360 degrees radiation ring inside the balloon catheter. An indocyanine green (ICG) doped liquid albumin solder was applied on the external surface of the vascular stumps. Laser soldering was achieved by irradiating with a 808 nm laser diode for 75 seconds. Tightness of the anastomoses was evaluated by clamping the artery distal to the anastomosis for 1 hour, and patency was tested over an observation period of 3 hours, during which the animals were heparinized. Thereafter, the anastomoses were harvested for histomorphological examination. RESULTS: All anastomoses remained patent over the entire observation period. Some leakage was observed in three anastomoses, which was explained by a deviation of the illumination fiber from the center of the balloon leading to an inhomogeneous irradiation of the vessel wall. Histology revealed perfect adaptation of the vascular stumps. A segment of denaturated vascular collagen was observed, that corresponded to the irradiated, solder-covered zone. CONCLUSION: Patent, maximally dilated and well adapted microvascular anastomoses could be obtained without the need of stay sutures. A well centered laser light source is indispensable for avoiding inhomogenous welding, thus causing leakage.     

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.     

Horizontal mattress technique for anastomosis of size-mismatched vessels

OBJECTIVE:

To evaluate the horizontal mattress technique in microvascular anastomosis for size-mismatched vessels.

METHODS:

The present study involved cadaveric simulation using size-mismatched (1.5:1) Thiel-embalmed cadaveric arteries. The authors performed horizontal mattress anastomoses using 9-0 nylon suture and recorded the procedure. Vessel patency was evaluated by saline infusion. Vessels were cut open and photographed; histological slides were prepared and stained with hematoxylin and eosin.

RESULTS:

Four anastomoses were performed. Vessels were found to be patent in all cases, with grade 0 leaks. Intima-on-intima apposition with no intraluminal exposure of muscularis nor adventitia were observed.

CONCLUSION:

The present cadaveric study supports the technical feasibility of using horizontal mattress sutures in size-mismatched end-toend anastomoses.     

Laser-assisted vascular end to end anastomosis of elastin heterograft to carotid artery with an albumin stent: a preliminary in vivo study

BACKGROUND AND OBJECTIVES: Laser-assisted end to end vascular anastomosis of an elastin heterograft to native artery may prevent problems associated with currently available vascular synthetic grafts and conventional suture anastomosis. STUDY DESIGN/MATERIALS AND METHODS: A total of 21 anastomoses in the carotid arteries of 7 domestic swine were performed with an 800 nm laser and an albumin stent plus solder. There were 5 artery to artery and 16 elastin heterograft to native artery anastomoses. Operative parameters, vascular patency, and histology of the anastomoses were evaluated. RESULTS: Out of 21 anastomoses, 16 were patent for 3 hours. One artery to artery anastomosis was thrombosed and four elastin heterograft to artery anastomoses were excluded from the study due to heterograft burst. The average amount of applied energy was 212 J for artery to artery anastomosis and 273 J for elastin heterograft to native artery. Histology shows coagulative necrosis of the adventitia, hypereosinophilic contraction band in the media of native arteries and no changes in elastin heterografts. CONCLUSIONS: Laser-assisted vascular anastomosis (LAVA) of elastin heterograft to medium size vessel using an albumin stent is feasible. Chronic studies are warranted to determine long-term patency and histology of the LAVA.     

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.     

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.     

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.     

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.     

Technique and proof of patency of microsurgical lympho‐lymphonodular anastomoses: A study in the rat model

Background: Lymphedemas due to local lymphatic blocks can be treated by microsurgical transplantation or transposition of lymphatic vessels. Here, the anastomoses are usually made end‐to‐end between lymphatics, but occasionally appropriate lymphatic recipient vessels are missing. In such cases, reconstructing lymph drainage by connection to a lymph node could be another technical option. The purpose of this study was to examine the patency rate of such lympho‐lymphonodular anastomoses in an experimental animal model. Methods: Male Sprague–Dawley rats were anesthetized, and the retroperitoneum was exposed. Patent blue dye was injected into the left foot to stain lymphatic structures. In group A (n = 8), the left lumbar trunk was cut centrally, the distal part was turned over to the right lumbar lymph node, and a microsurgical lympho‐lymphonodular anastomosis was performed. In group B (n = 8), the left lumbar trunk was cut. After 8 weeks, the lumbar region was surgically re‐explored, and the lymphatic drainage was examined by injection of Patent blue dye into the left lumbar lymph node. Results: In 8/8 animals of group A, patent transposed lymphatics were found. The patency of the anastomosis was proven directly by observation of blue dye transit and indirectly by observation of blue staining of the right lumbar lymph node. In 6/8 animals of group B, no lymphatic connection to the right lumbar lymphatic system was observed. Conclusions: This is the first report of the microsurgical technique and the proof of patency of lympho‐lymphonodular anastomoses. The novel animal model for testing the patency of transposed lymphatics is discussed. © 2009 Wiley‐Liss, Inc. Microsurgery, 2009.     

Improved microvessel repair: laser welding with an anti-thrombotic solder

BACKGROUND AND OBJECTIVES: Concentrated protein solutions can be used as thermally polymerized solders in laser welding. Solders supplemented with biologically active chemicals may provide in situ drug delivery for localized therapeutics. These studies characterize a serum albumin (SA) solder containing heparin, designed to reduce microvascular thrombosis rates. STUDY DESIGN/MATERIALS AND METHODS: Samples of heparin added to 30% SA to obtain heparin-to-albumin molar ratios (HAMR) of 4:1 and 2:1 were thermally polymerized, and heparin release into saline was measured. Using a rat thrombosis model, patency was determined for suture, and 0 U/ml (control), 2.5 U/ml, 50 U/ml heparin solder repairs. RESULTS: Heparin release was five times higher for 4:1 than 2:1 HAMR solder acutely, but was equivalent after 2 days. Animal patency rates were: 50% suture, 0% control, 50% low heparin, 66% high heparin (P < 0.05 vs. control). CONCLUSIONS: Solders incorporating heparin should provide in situ anti-thrombotic therapy reducing the risk of microvascular thromboses.