Laser-assisted vasovasostomy in the rat. Comparison of CO2 and neodymium:YAG laser techniques

A comparative study was undertaken to investigate the Nd:YAG and CO2 laser systems for laser-assisted vasovasostomies (LAVs). In 32 rats 64 vasovasostomies were performed, either conventionally sutured (CSV) or laser-welded (LAV-CO2 and LAV-Nd:YAG). Postoperative investigations included patency tests, gross examination, light and electron microscopy. The highest rate of sperm granulomas (50%) and the lowest patency rate (50%) was seen in the LAV-Nd:YAG group. LAV-CO2 showed the lowest rate of sperm granulomas (12.5%) and had a patency rate (82%) which was comparable to that of CSV (88%). Laser-assisted vas anastomosis is time saving and technically easy to perform. Contrary to microvascular anastomoses, where both laser types offer the same results, vas anastomosis is better done using a CO2 laser system.     

CO2 and Nd:YAG laser-assisted nerve repair: a study of bonding strength and thermal damage

To improve the laser welding procedure, a comparative study was undertaken to investigate the acute bonding strength and the thermal damage following CO2 and Nd:YAG laser-assisted nerve repair, performed with and without the use of blood and/or albumin as a solder. The strongest welds were produced with the CO2 laser using albumin as a solder. Thermal damage was minimal with the CO2 laser, whereas the damage with the Nd:YAG laser was substantial. The high bonding strength combined with minimal thermal damage of the nerve following repair with the CO2 laser with the use of albumin justify further investigations using this technique in in vivo studies.     

Biological effects of laser welding on vascular healing

The feasibility of welding thin-walled microvessels by laser has been established. This report summarizes our experience using laser welding to repair thick-walled, high-pressure, 4 to 8-mm canine arteries using CO2, Nd:YAG, and argon lasers. The CO2 laser did not produce seals that could withstand arterial pressure. Nd:YAG laser welds were initially successful, but the majority failed within 20 to 40 minutes. The argon laser uniformly sealed 2-cm-length arteriotomies that healed rapidly within 4 to 6 weeks and had less foreign body response compared to sutured controls. Laser welding may represent an alternative for repair of small- and large-diameter vessels with several advantages compared to conventional suture techniques.     

Intraoral laser welding: ultrastructural and mechanical analysis to compare laboratory laser and dental laser

The Nd:YAG laser has been used since 1970 in dental laboratories to weld metals on dental prostheses. Recently in several clinical cases, we have suggested that the Nd:YAG laser device commonly utilized in the dental office could be used to repair broken fixed, removable and orthodontic prostheses and to weld metals directly in the mouth. The aim of this work was to evaluate, using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and dynamic mechanical analysis (DMA), the quality of the weld and its mechanical strength, comparing a device normally used in dental laboratory and a device normally used in the dental office for oral surgery, the same as that described for intraoral welding. Metal plates of a Co-Cr-Mo dental alloy and steel orthodontic wires were subjected to four welding procedures: welding without filler metal using the laboratory laser, welding with filler metal using the laboratory laser, welding without filler metal using the office laser, and welding with filler metal using the office laser. The welded materials were then analysed by SEM, EDS and DMA. SEM analysis did not show significant differences between the samples although the plates welded using the office laser without filler metal showed a greater number of fissures than the other samples. EDS microanalysis of the welding zone showed a homogeneous composition of the metals. Mechanical tests showed similar elastic behaviours of the samples, with minimal differences between the samples welded with the two devices. No wire broke even under the maximum force applied by the analyser. This study seems to demonstrate that the welds produced using the office Nd:YAG laser device and the laboratory Nd:YAG laser device, as analysed by SEM, EDS and DMA, showed minimal and nonsignificant differences, although these findings need to be confirmed using a greater number of samples.     

Intra-oral laser welding: an in vitro evaluation of thermal increase

The neodymium:yttrium–aluminium–garnet (Nd:YAG) laser is currently used in dental laboratories to weld metals on dental prostheses. Recently, the use of Nd:YAG has been suggested so that dentists themselves can repair broken fixed, removable and orthodontic prostheses by welding metals directly in the mouth. This work aimed to evaluate, through a four k-type thermocouple system on calf jaws, the thermal increase in the biological structures close to the metal parts during laser welding. We put two hemispherical metal plates onto mandibular molars and then laser welded them at three points with a four k-thermocouple system to determine the thermal rise in the pulp chamber, sulcus, root and bone. This procedure was carried out on 12 samples, and the results were processed. The highest values of thermal increase were found in the pulp chamber, 1.5°C; sulcus, 0.7°C; root, 0.3°C; and bone, 0.3°C. This study showed that thermal increases in pulp chamber, sulcus, root and bone were biologically compatible and that intra-oral laser welding, at the parameters used in this work, seems to be harmless to the biological structures close to the welding and thermally affected zones.     

Assessment of tissue blood flow following small artery welding with an intraluminal dissolvable stent

Using the technique of radioactive 51Cr-labeled biological microspheres, this study evaluated arterial blood flow following small vessel anastomosis by CO2 laser welding and a dissolvable stent in the lumen. A total of 30 Sprague-Dawley rats were divided into two groups. Group A: 11 rats had their femoral arteries ligated on one side. The contralateral side served as a control, with the artery transected and repaired using conventional microsuturing. Group B: 19 rats had their femoral arteries transected and repaired using CO2 laser welding and an intraluminal dissolvable stent technique. The contralateral side was again used as a control using conventional microsuturing. At 1 hr postoperatively, 51Cr-labeled biological microspheres were injected centripetally into the left common carotid artery and the legs and thighs immediately harvested for measurement of radioactivity. All repaired arteries were patent (30/30 in the microsuturing group and 19/19 in the stented welding group), with no detectable stenosis or dilation at the repaired site. Statistical analysis showed that tissue radioactivity (cpm/g) in the ligated group (3,972 +/- 384 in thighs and 3,142 +/- 742 in legs) was significantly lower than in the microsuturing group (7,132 +/- 1,723 in thighs and 6,557 +/- 1,469 in legs) (P < 0.01). In the ligated group, a significant reduction of blood flow was seen in the legs when compared with the thighs (P < 0.05). There was no significant difference in radioactivity when comparing the microsuturing control with the stented welding group, in both thighs (7,064 +/- 2,599 and 7,006 +/- 2,406, respectively; P > 0.05) and legs (6,386 +/- 1,703 and 6,288 +/- 1,757, respectively; P > 0.05). This study provided evidence that the dissolvable stent placed intraluminally does not impair blood circulation and that when coupled with CO2 laser welding offers a high-quality alternative to conventional small vessel anastomosis.     

Thermal effects in tissues from combined simultaneous coaxial CO2 and Nd:YAG laser beams.

This study examines the depth of thermal coagulation and charring in swine liver, kidney cortex, tongue (inferior surface), skeletal muscle, inflated lung, and skin resulting from in vivo incision with simultaneous coaxial CO2 and Nd:YAG (1.064 microM) laser beams. At values of 20 w and 40 w, respectively, and at values of 30 w and 60 w, respectively, of combined CO2 and Nd:YAG laser radiation, coagulation depths determined histologically in liver were significantly greater (P less than 0.01) than in the other tissues and were significantly less in inflated lung (P less than 0.05) than in other tissues for the larger laser power settings employed. Coagulation depths achieved at 10 w and 20 w, respectively, and at 20 w and 40 w, respectively, of CO2 and Nd:YAG laser power were comparable to those obtained by other workers in liver and other relatively vascular tissues using a contact Nd:YAG laser tip. Charring depths obtained at power settings of 30 w (CO2) and 60 w (Nd:YAG) were greater in liver (P less than 0.001) than in all other tissues examined. Hemostasis during incision was achieved only for values of the ratio of CO2 to Nd:YAG laser power in the range 2-3 in the more vascular tissues, liver and kidney cortex, whereas hemostasis was achieved also in the lesser vascular tissues at higher values. These results strongly suggest the usefulness of combined simultaneous CO2 and Nd:YAG laser beams in surgery of the more vascular organs and tissues.     

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.     

Sutureless End-to-End bowel anastomosis using Nd:YAG and water-soluble intralurninal stent

Sutureless end-to-end intestinal anastomoses were successfully constructed in 20 rabbits. A water-soluble intraluminal stent was used to approximate the tissue edges, and the anastomotic seam was lased with 1.06 μm neodymium:YAG (Nd:YAG) laser energy supplied through a hand-held 600-μm gas-cooled noncontact optical fiber. A continuous 5-watt wave of power was applied over periods ranging from 46 to 92 seconds to produce the tissue blanching and shrinkage that indicated a satisfactory tissue weld. Integrity, degree of tissue reaction, and bursting pressures of the anastomoses were compared to those of anastomoses constructed using standard sutured techniques. The results of the two methods were equivalent at 1 to 3 days, but the laser-fused enteric anastomoses showed less inflammatory reaction and greater bursting pressures at 7 and 14 days. Application of a variety of proteinaceous solutions including extracellular matrix materials and epidermal growth factors prior to lasing failed to augment wound healing. We conclude that lasers show promise as reconstructive, in addition to ablative, surgical instruments.     

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.     

Splenic resection with the Contact Nd:YAG laser system

Splenic resection in the dog was proven to have decreased blood loss (52%), decreased operating time (44%), and decreased surgical manipulation using the SLT Contact Nd:YAG Laser System with the synthetic sapphire probe, as compared with the noncontact CO2 laser. Tissue damage and hematologic changes were minimal and equivalent in both laser systems. The overall ease of use and operating technique was subjectively better with the contact Nd:YAG laser, and the danger of scattered and reflective beam damage was eliminated. The contact Nd:YAG laser with the synthetic sapphire probes offers a significant advantage over the noncontact CO2 laser in the resection of splenic tissue. Future applications in pediatric surgery now need to be evaluated.     

1064-nm Nd:YAG皮秒点阵激光与超脉冲CO2点阵激光治疗面部萎缩性痤疮瘢痕的临床比较

目的 探究1064-nm Nd:YAG皮秒点阵激光与超脉冲CO2点阵激光治疗面部萎缩性痤疮瘢痕的疗 效与安全性。方法 选取2021年6月-2023年6月于我院激光科接受治疗的62例面部萎缩性痤疮瘢痕患者作 为研究对象,按照不同的治疗方法分为皮秒点阵激光组和CO2点阵激光组,各31例。皮秒点阵激光组给予 1064-nm Nd:YAG皮秒点阵激光治疗,CO2点阵激光组给予超脉冲CO2点阵激光治疗,比较两组ECCA权 重评分、疗效自评分、满意度评分及术后不良反应发生情况。结果 两组治疗后ECCA权重评分均较治疗 前降低（P ＜0.05）,且皮秒点阵激光组的ECCA权重评分高于CO2点阵激光组（P ＜0.05）;CO2点阵激光 组疗效自评分高于皮秒点阵激光组（P ＜0.05）;皮秒点阵激光组不良反应发生情况低于CO2点阵激光组 （P ＜0.05）;两组满意度比较,差异无统计学意义（P＞0.05）。结论 1064-nm Nd:YAG皮秒点阵激光与 超脉冲CO2点阵激光均能有效改善面部萎缩性痤疮瘢痕,超脉冲CO2点阵激光疗效更好,而皮秒点阵激光 不良反应发生情况更少。     

Effects of Nd:YAG and CO2 lasers on cerebral microvasculature. Study in normal rabbit brain

The effect of Nd:YAG and CO2 laser beams on cerebral microvasculature was examined in experimental animals. Soft x-ray microangiography and histological examination of the brain after Nd:YAG laser exposure revealed broad avascular or oligovascular zones in the irradiated and the surrounding edematous tissue, in which the surviving vessels were narrowed and tapered without significant leakage of blood. After CO2 laser exposure, a wedge-shaped tissue defect surrounded by layers of charring, coagulation, and edema was observed. The main finding in the surrounding coagulation and edematous layers was dilatation of the vessels. Hemorrhage was sometimes observed, mainly in the edematous layer. These findings seem to explain the effective hemostatic capability of the Nd:YAG laser and the occasional hemorrhage following CO2 laser exposure, especially at high energy output.     

Experimental study of single and combined coaxial exposure by high-peaked pulse wave CO2 and Nd:YAG laser on the brain: effect on the brain microvasculature in the subacute stage

The effect of single or combined coaxial exposure by Nd: YAG and CO2 (pulse wave) laser on the brain at the subacute stage was examined in experimental animals. Soft X-ray microangiography and histological examination of the brain were performed 48 hours after laser exposure. The lasers in this study were pulse wave form CO2 of 2, 4 and 8 watts and YAG lasers of 10, 20 and 40 watts, employed separately or simultaneously using 130 YZ of Nihon Infrared Industries Company. Japanese white rabbits were anesthetized with pentobarbital. Bilateral fronto-parietal craniectomy were made, and the dura was removed. After intravenous injection of Evans blue, the lasers were employed to the cerebral cortex using a micromanipulator attached to the operation microscope. The spot size was 0.7 mm in diameter for CO2 laser and 1.2 mm for Nd: YAG laser. Forty-eight hours after exposure, microangiography was performed and brains were prepared for the histological examination. Histological examination and microangiogram of the brain after CO2 laser exposure revealed semilunar avascular area in the edematous layer surrounded with dilated vessels. Histological examination and microangiogram of the brain after Nd: YAG laser exposure revealed broad avascular or oligovascular zones in the surrounding edematous tissue, in which the surviving vessels were narrowed. Edematous zones were also shown in the subcortical portion. The histological examination and microangiogram after combined coaxial exposure of CO2 and Nd: YAG lasers revealed triangular avascular or oligovascular zones in the edematous tissue, in which the surviving vessels were narrowed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of electrocautery, CO2 laser, and contact Nd:YAG laser scalpel on the healing of intestinal incision

Leakage after intestinal resection is a serious complication with a high mortality rate. A recent study claims that cutting the intestine with the CO2 laser improves the healing of intestinal anastomoses (Ferulano et al: Eur Surg Res 16:127-130, 1984). The present study was undertaken to analyze the effects of electrocautery, CO2 laser, and contact Nd:YAG laser on the healing of intestinal incisions. Fifteen piglets were used and the cutting and reanastomosing were performed by using all cutting methods in each animal in randomized order. Resection sites were 50 cm, 100 cm, and 150 cm distal to the ligament of Treitz. On the seventh day the bursting pressures were measured for each anastomosis. They were 172 +/- 17 mmHg for normal bowel segment and 133 +/- 12, 135 +/- 40, and 139 +/- 17 mmHg for electrocautery, CO2 laser, and Nd:YAG laser, respectively. There were no mortality, no anastomotic leaks, and no statistically significant differences in the bursting pressures, in histology, or in the healing of anastomotic sites, indicating that electrocautery, CO2 laser, and contact Nd:YAG laser scalpel can safely be used in the surgery of small intestine.     

The potentials of CO2 laser in the surgery of the liver, biliary tract and pancreas.

The Nd:YAG and CO2 laser can be used with benefit in the surgery of the liver, biliary tract and pancreas. The Nd:YAG laser is most suitable for cutting parenchymatous organs, as e.g. the liver. In biliary surgery the CO2 laser can be recommended. Based on their 12 cases, authors discuss the applicability of CO2 laser.     

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.     

可调脉宽倍频Nd：YAG激光和点阵CO_2激光综合治疗瘢痕的临床应用

目的：探讨综合应用可调脉宽倍频Nd：YAG532nm激光和点阵CO2激光分别治疗面颈部早期红色瘢痕和晚期浅表性瘢痕的临床效果。方法：采用可调脉宽倍频Nd：YAG 532nm波长激光治疗面颈部红色增生期瘢痕,采用点阵CO2激光治疗面颈部浅表性瘢痕,并且根据疗效评定标准对治疗效果进行评价。结果：98个早期红色增生期瘢痕每次经激光治疗后症状和体征都减轻,4次治疗后手术切口条形瘢痕的总有效率为100%,显效率为96%,挫伤及烧烫伤后片状瘢痕的总有效率为91%,显效率为70%。80例浅表性瘢痕一次治疗后的总显效率为65%。结论：综合应用可调脉宽倍频Nd：YAG532nm激光和点阵CO2激光分别治疗面颈部早期增生性瘢痕和晚期浅表性瘢痕的治疗方案可行,值得临床推广应用。     

Histologic Evaluation of a Q-Switched Nd:YAG Laser in the Nonablative Treatment of Wrinkles

BACKGROUND: A variety of nonablative dermal remodeling techniques are currently available. The Q-switched Nd:YAG laser, in addition to its role in tattoo removal, hair removal, and vascular and pigmented lesion treatment, may also play a role in dermal remodeling for the treatment of wrinkles. The histologic changes seen in human skin after Q-switched Nd:YAG laser exposure have yet to be evaluated. OBJECTIVE: To study histologic changes after the use of a Q-switched Nd:YAG laser in the nonablative treatment of photoaged skin. METHODS: Sun-damaged infrauricular skin from six female subjects was exposed to a Q-switched Nd:YAG laser at fluences of 7 J/cm2 with two laser passes. Histologic examinations were performed before laser treatment and 3 months later. RESULTS: Biopsy specimens showed slight fibrosis in the superficial papillary dermis with unremarkable epidermal changes. CONCLUSION: The Q-switched Nd:YAG laser produced morphologic changes similar to, but lesser in degree, than those seen with both CO2 and Er:YAG laser resurfacing.     

Endoscopic transgastric drainage of pancreatic pseudocyst with the use of Nd:YAG laser

Pancreatic pseudocysts have been successfully managed with endoscopic drainage recently. This report describes a case of endoscopic transgastric drainage using endoscopic ultrasonography (EUS) and an Nd:YAG laser. EUS was used to detect an optimal puncture site of the pseudocyst and to reduce the risk of bleeding and perforation. An Nd:YAG laser was used to minimize the risk of bleeding and to penetrate the thick wall of the pseudocyst. After transgastric cystgastrostomy was performed, an internal stent was placed between the pseudocyst and the stomach. There were no complications associated with endoscopic interventions. Complete resolution of the pseudocyst was observed. Endoscopic transgastric drainage of pancreatic pseudocysts is a recommended approach for selected patients with pancreatic pseudocysts that are uncomplicated and are located adjacent to the stomach. Safe and effective drainage can be achieved without hemorrhage and perforation with the use of EUS, an Nd:YAG laser, and a stent. Furthermore, the Nd:YAG laser facilitated passage through a markedly indurated pseudocyst wall and it seemed to be an effective instrument, especially for pseudocysts with a thick wall.