Closure of rabbit ileum enterotomies with the argon and CO2 lasers: bursting pressures and histology

In this study, we examined short-term strength and histology of experimental argon and CO2 laser-welded and control-sutured enterotomies in a rabbit model. Longitudinal 1.0-cm enterotomies were closed with the argon laser at 0.5 (n = 10) or 1.0 (n = 10) W power and a spot diameter of 2.8 mm resulting in energy fluences of 230 and 450 J/cm2, respectively. Similar enterotomies were closed using the CO2 laser at 0.5 (n = 10) or 1.0 (n = 10) W power and a spot diameter of 1.2 mm, resulting in energy fluences of 1,360 and 2,730 J/cm2. In all closures, continuous wave laser was delivered for 30 seconds. Using a pressure-monitored infusion system with normal saline, the pressure required to burst each weld as well as sutured controls (n = 10) was recorded approximately 1 minute following fusion. Mean bursting pressures for the argon laser at 0.5 W and 1.0 W were 34.1 +/- 19.4 mm Hg (mean +/- SD) and 17.3 +/- 8.3 mm Hg, respectively, and for the CO2 laser were 23.5 +/- 12.0 mm Hg and 31.8 +/- 15.6 mm Hg, respectively. Sutured controls leaked at 45.2 +/- 12.0 mm Hg. With the exception of argon-laser welds at an energy fluence of 450 J/cm2, which were less than sutured repairs, the bursting pressures for welded closures were not significantly different from the sutured controls (Student's t distribution, P less than .05). Histologic examination of both types of welds demonstrated a fibrin and red blood cell coagulum bridging the anastomosis, with some evidence of mild thermal injury at the mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sutureless anastomosis using a biofragmentable anastomosis ring

The biofragmentable anastomosis ring (BAR) is composed of polyglycolic acid and barium sulfate. When used for intestinal anastomosis, the BAR fragments after the anastomosis is established. We used this device in 43 patients. In three patients, the anastomosis with BAR was abandoned due to technical difficulties. A total of 43 anastomoses with BAR were performed in 40 patients. The operations in which BAR was used included right hemicolectomy in 12 patients, transverse colectomy in 7, sigmoidectomy in 11, small bowel resection in 5 and other bowel resections in 8. The time spent for the BAR anastomsis ranged from 7 to 30 min with a mean of 15.2 min, which was significantly shorter than that of conventional hand-sutured anastomosis in 23 cases. The fragmentation and excretion of the BAR occurred from 14 to 49 days later with a mean of 21.8 days. There was only one instance of anastomotic leakage (1/40, 2.5%), which occurred in a patient with a cytomegaloviral infection of the intestine. A postoperative barium enema study in 28 patients showed no passage disturbance through the anastomosis. In conclusion, the anastomosis using BAR is considered to be a simple, safe, and fast method for performing either colonic or small intestinal anastomosis.     

Vasovasostomy in the murine vas deferens: comparison of the Nd:YAG laser at 1.06 microns and 1.318 microns to the CO2 laser

A comparison is made of laser anastomoses of the murine vas deferens at different energies with the neodymium (Nd):YAG laser at 1.06 micron and 1.318 micron and with the CO2 laser. A total of 28 welds were performed with a free-hand technique employing a 600-micron silicon fiber with the Nd:YAG and a hand piece with a 500-micron spot size for the CO2. After 6 weeks, all animals were sacrificed and the vasa evaluated for patency. Fifteen out of 28 controls repaired with microsurgical techniques were found to be patent; 4/10 vasa were patent with use of the Nd:YAG at 1.318 micron at laser energies of 300 mW and 500 mW. At 1.06 micron, only 1/4 anastomoses was patent at a power setting of 1 W. None of the anastomoses performed with the CO2 laser was patent. Histologic study revealed intense fibrosis in all the lasered vasa, with sperm granuloma formation associated with most anastomoses. Although this is a preliminary study, it appears that the Nd:YAG laser at 1.318 micron and a power setting of 300-500 mW provides patency rates superior to the Nd:YAG at 1.06 micron and to the CO2 lasers and is equivalent to standard micro-surgical techniques in the murine vas deferens.     

CO2 laser urethroplasty in the rabbit: a preclinical model.

Our previous work has shown that the CO2 laser can be successfully used in urethral reconstruction in a rat model. This new experiment investigates the use of the CO2 laser to perform a patch graft urethroplasty in the rabbit, as a preclinical model to its use in the repair of hypospadias in humans. Using sterile technique, a patch graft of preputial skin was welded in the repair of a standardized urethral defect in 10 rabbits. In another cohort, the same urethral defect was repaired using standard microsuture technique. In a control group the patch graft was placed with microsuture in a nonwatertight fashion. All animals were followed for 3 weeks. Histologic and radiologic analyses were done in a blinded fashion. Our study showed that CO2 laser repair, when compared to microsuture in urethral reconstruction, required 40% less operative time and produced better graft healing and less intraluminal scarring.     

Laser-assisted microvascular anastomosis using CO2 and KTP/532 lasers.

The milliwatt carbon dioxide (CO2) laser has been shown to be an effective device for performing laser-assisted microvascular anastomosis (LAMA) with consistently high patency rates, minimal tissue disruption, and rapid surgical time as well as the potential for reduced inflammation due to fewer foreign bodies (sutures) in the wound. The purpose of this investigation was to determine the feasibility of using the potassium titanyl phosphate (KTP) laser to perform LAMA and to compare it to CO2 LAMA in both arteries and veins. Patency rates, inflammatory response, and course of healing were evaluated through histological analysis. Twenty-eight rats were divided into two groups, which underwent either CO2 or KTP LAMA and then were sacrificed at 3 days, and 1, 2, 4, 8, and 12 weeks postoperatively. Patency rates for arteries and veins were comparable for both wavelengths (CO2: 100% for arteries, 93% for veins; KTP: 93% for arteries, 93% for veins). Histological grading of inflammation and fibrosis showed no significant difference between the two groups. This study demonstrated the efficacy of using the KTP/532 laser in performing LAMA. We found the KTP and CO2 LAMA to have comparable patterns of tissue damage and course of healing. Although this experiment did not investigate the mechanism(s) of tissue welding, our results suggest that successful LAMA may be independent of wavelength.     

Mechanism of tissue fusion in argon laser-welded vein-artery anastomoses

The mechanism of laser vascular tissue welding remains unknown. This study compared the acute tissue response and long-term healing of sutured and laser-welded anastomoses of vein segments used to bypass ligated canine femoral arteries. For each procedure, one anastomosis was formed using running 6-0 polypropylene suture (control), and the other anastomosis was formed using argon laser tissue welding (experimental). The vein grafts were harvested at 4 (n = 2), 8 (n = 1), 12 (n = 1), and 16 (n = 2) weeks, and selected samples were evaluated by histologic examination, electron microscopy, tensile strength testing, and by measuring the formation of [3H]hydroxyproline as an index of collagen synthesis. Examination of successful laser fusions immediately after they were formed showed bonding of collagen to collagen and elastin to collagen. Follow-up evaluations showed that the precision of tissue apposition affected the rate of healing and tensile strength. Laser-welded anastomoses demonstrated a progression of healing similar to sutured repairs, with remodeling of fibrous tissue and collagen being the primary component of weld integrity. This study demonstrates that sutured and argon laser-welded vein-artery anastomoses heal comparably up to 16 weeks postoperatively, and that laser welding is a satisfactory alternative to sutured anastomoses.     

CO2 and argon laser vascular welding: acute histologic and thermodynamic comparison

CO2 and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO2 and argon laser welding of 1-cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of +/-0.2 mm and +/-0.2 degree C, respectively, were analyzed. A HGM argon laser using a 300-microns optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO2 welds were performed with a Sharplan CO2 laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon-n = 20; power = 500 mW; energy fluence = 1,400 J/cm2; Tmax = 48.8 degrees C; T mean +/- S.D. = 45.1 +/- 2.7 degrees C; CO2-n = 20; power = 150 mW; energy fluence = 3,000 J/cm2; Tmax 84.0 degrees C; T mean +/- S.D. = 60.7 +/- 9.8 degrees C. There was a significant difference (P less than .05) in thermal measurements between successful CO2 and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO2 laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bursting strength in CO2 laser-assisted microvascular anastomoses

Iliac artery end-to-end anastomoses were performed in 42 Sprague-Dawley rats, divided into seven groups, to determine the welding effects of CO2 laser radiation in microvascular anastomoses. Conventional suture techniques were performed on right iliac arteries, and left iliac arteries were anastomosed with a laser-assisted technique. Bursting strength and diameters of the anastomotic sites were measured at different intervals (from one day to five weeks) post surgery. The anastomotic patency rate was 100 percent in both groups, and the aneurysm rate was only 2 percent in the laser group. Bursting strength was low at one and three days post surgery in both groups; then, it increased gradually until both groups could withstand higher than physiologic pressures. Results of high patency rates, low aneurysm formation, and the ability to withstand pressures higher than physiologic, suggest that the laser-assisted anastomotic technique can play an important role in microvascular surgery.     

Laser-assisted intestinal anastomosis

Laser-assisted tissue fusion has been investigated as a new technology to enhance the healing of soft tissues. Laser fusion of intestinal anastomoses shows promise as a method to obtain primary healing while eliminating a foreign-body reaction associated with the sutures. This paper reviews the experimental data that are available regarding laser-assisted intestinal anastomoses and summarizes our experience using the CO2, Nd:YAG, and argon lasers to form fusions in small bowel.     

Comparison of argon-laser welded and sutured repair of inferior vena cava in a canine model

BACKGROUND AND OBJECTIVE: Advantages of laser-welded microarterial anastomoses have been reported. However, whether laser repair of large veins is advantageous is not yet known. Argon-laser welding of inferior vena cava was therefore compared with conventional-sutured repair. STUDY DESIGN/MATERIALS AND METHODS: Twenty-four adult mongrel dogs were used. Twelve inferior vena cavas were repaired using an argon laser and the rest using continuous sutures. Specimens were removed at 2, 8, 16, and 24 weeks after repair. Technical characteristics, cavographical findings, and results of histopathological study using light and transmission electron microscopy were compared. RESULTS: Procedure time did not significantly differ between the two groups. The sutured repair sites were narrower than those repaired by laser immediately after and at 2 and 24 weeks. Histologically, laser welding resulted from denaturation of collagen and mild healing occurred simultaneously with the disappearance of denatured collagen. By contrast, there was strong fibrotic reaction at sutured repair sites. CONCLUSIONS: These findings suggest that argon-laser repair of large veins is superior to continuous suturing.     

Sutureless anastomosis of blood vessels using cyanoacrylate adhesives

On the assumption that the remaining suture threads of the anastomotic line play an important role in the progression of anastomotic neointimal hyperplasia, we performed an experimental study on the sutureless anastomosis of blood vessels. An expanded polytetrafluoroethylene graft, 5 mm in diameter and 2 cm in length, was implanted on the abdominal aorta of mongrel adult using one of three methods of anastomosis, namely; a continuous suture, a stay suture, or sutureless anastomosis. Overall patency rates were 83.3 per cent, 91.7 per cent and 75.0 per cent respectively. The thickness of the pannus in the distal anastomotic line after 12 months was 107 m in one graft in the continuous suture group, 106 m and 222 m in 2 grafts each in the stay suture group, and 41 m and 117 m in 2 grafts each in the sutureless group. Because there were cases of patency even after 12 months with a very small pannus thickness, sutureless anastomosis is considered to be a useful method of preventing anastomotic neointimal hyperplasia.     

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.     

Primary closure of choledochotomy using CO2 laser: Comparison with suture closure

This study was designed to compare laser welding to suture closure of the common bile duct (CBD). A 12 mm linear choledochotomy was closed in 12 mongrel dogs using tissue welding lowenergy CO₂ laser. Tissue welding was accomplished at 5.0 w/cm² for 120 sec. Twelve similar mongrel dogs (control) were treated with CBD closure using 5/0 Vicryl (polyglactin 910, Ethicon, Inc., Somerville, NJ) interrupted simple stitches. All animals were sacrificed at six weeks. Gross and histologic evaluation of the choledochotomy site were performed. There were no statistical differences in parameters of comparison in the two groups. These parameters were pre- and post-treatment measurements of liver function tests, stenosis, and dehiscence. However, it must be noted that there was a 33% (4/12) incidence of dehiscence and death in the CO₂ laser welded choledochorrhaphy. This result, although not statistically significant, is clinically significant. We conclude that the tensile strength of CO₂ laser welded CBDs must be optimized and that these results are preliminary and still unreliable to recommend for clinical adaptability. © 1993 Wiley-Liss, Inc.     

Argon laser vascular fusion: venous and arterial bursting pressures

This study was designed to determine the optimal laser power (watts) for maximal strength of argon laser vascular fusions by measuring bursting pressures of repairs. Longitudinal incisions (n = 105) measuring either 2.5 or 5 mm in length were performed in canine femoral, carotid, and jugular veins and arteries and were fused with the argon laser at 0.3, 0.5, 0.7, or 0.9 W power. Total exposure time for each repair (50 to 80 sec/0.5 cm) was adjusted to yield identical energy fluences of 1,100 J/cm2. Bursting pressure of the fusions was determined by monitored infusion of anticoagulated blood into an isolated segment of the vessel that contained the fusion. Mean bursting pressures for venous and arterial repairs were significantly higher in the 2.5 mm incisions compared with the 5 mm incisions (P less than 0.05). Venous and arterial repairs of equal length performed at each power resulted in equivalent bursting strengths, except that 5 mm venous segments fused with 0.9 W withstood lower pressures than all other venous repairs (P less than 0.05), and 5 mm arterial segments were in turn significantly weaker at 0.3 W (P less than 0.02). We conclude that argon laser fusion is equally suitable for repair of medium-sized veins and arteries and that immediate strength decreases with increasing length of repair. To maximize strength of longer repairs, venotomies should be welded at power settings between 0.3 and 0.7 W while arteriotomies should be fused at power settings between 0.5 and 0.9 W. The differences in optimal power may be explained by variable wall composition and thickness between veins and arteries.     

Low-energy CO2 laser intestinal anastomosis: an experimental study

Intestinal anastomosis was performed in 17 Wistar rats via tissue welding by the low-energy CO2 laser. The postoperative course in the animals studied was uneventful. The integrity of the anastomosis was investigated manometrically, immediately upon completion of the anastomosis as well as 20 days later. Ten additional Wistar rats served as controls in which conventional interrupted one-layer anastomosis was performed. The results show a significant superiority of the intestinal anastomoses that were constructed by means of laser tissue welding. The time to complete the anastomosis was also significantly shorter when laser rather than manual suturing was used. Serial histological examinations for up to 90 days following surgery revealed complete healing and epithelization of the anastomotic site.