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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.

Clinical observations have suggested that low-energy lasers might stimulate wound healing. To understand the mechanism of the biostimulation, we previously examined the effects of low-energy lasers on collagen production by human skin fibroblasts and reported an increase of collagen synthesis in vitro. To examine the effects of low-energy lasers in vivo, hairless mice were experimentally wounded, sutured, and subjected to laser irradiation by a helium-neon laser with a power output of 1.56 mW and an energy fluence of 1.22 Joules/cm2. Experimental wounds were subjected to laser treatment every other day for 2 months; control wounds remained untreated. Specimens from the wounds were then examined for histological findings, tensile strength, and total collagen content. Results demonstrated a considerable improvement in the tensile strength of the laser-irradiated wounds at 1 and 2 weeks. Furthermore, the total collagen content was significantly increased at 2 months when compared with control wounds. These results suggest a beneficial effect of the helium-neon laser on wound healing in vivo.

Previous studies have indicated that laser can selectively affect the biological functions of cells. In the present study, the role of a thermal component in laser-induced alterations in the biology of human skin fibroblasts was examined. Cells were cultured on 96-well tissue culture plates, subjected to treatment with the Nd:YAG laser (wavelength 1,064 nm), and the temperature of the medium was monitored by a microprobe connected to a telethermometer . For comparison, parallel cultures were heated to the same temperatures by tungsten-halogen lamp. The cell cultures were analyzed for collagen synthesis by incubating the cultures with [3H]proline, and the collagen production was assayed by the synthesis of nondialyzable [3H]hydroxyproline. The rate of DNA replication was also determined by measuring the uptake of [3H]thymidine. A marked decrease of collagen production and thymidine incorporation was noted in the cultures subjected to Nd:YAG laser. No such decreases were noted in cultures heated to the corresponding temperatures by tungsten-halogen lamp. The results thus indicate that the biochemical alteration caused by the Nd:YAG laser in human fibroblast functions cannot be explained on the basis of thermal effects.

Pig skin was treated with the Nd:YAG laser at 1,060 nm or electrocautery, at energy densities of 649 +/- 20 J/cm2 and 612 J/cm2, respectively. Biopsies of treated areas and of normal skin were performed at 7, 14, and 60 days after treatment and processed for histology, electron microscopy and biochemical assays. Wound healing, as shown histologically, was similar in both treated groups. Depth of injury appeared to reach reticular dermis at day 7 in each treated group. However, thermal burn was more destructive of regular collagen, whereas the laser appeared to damage deep dermal blood vessels without destroying surrounding connective tissue. Biochemical assays revealed increased collagen production and increased collagenolytic activity 7 days after laser injury. However, by day 60, there was a reduction in total collagen content in laser treated skin below that of normal skin, which correlated with decreased collagen synthesis and unchanged collagenolytic activity. In burn specimens there was an initial decrease in total collagen content which reverted to normal by day 60. Active collagen degradation occurred at all 3 time points, but a marked increase in synthetic activity occurred as the burn scar was laid down. Laser treatment resulted in reduction of the amount of collagen below that in burn scarred or normal skin, suggesting that classical scar formation may be inhibited. These results indicate that the Nd:YAG laser may be useful for the treatment of keloids and hypertrophic scars.

To determine the effects of laser irradiation upon human coronary atherosclerotic disease, coronary plaques were extracted from fresh human cadaver hearts. Seventy-four diseased artery samples were sectioned either transversely or longitudinally and subjected to laser treatment from argon-ion and carbon dioxide sources. The laser beam affected vaporization and patency in fibrous, lipoid, and calcified plaques as observed histologically. Calcified blockage showed greater extent of charred remnants following controlled thermal injury than did fibrous or lipoid obstructions. The area and depth of penetration varied directly with intensity and duration of photoirradiation and inversely with the density of the atherosclerotic tissue. This study supports further research work on the use of lasers to effect relief of atherosclerotic obstructions.

We report a series of patients with severe radiation injury treated with endoscopic laser photocoagulation. Eight patients with recurrent lower gastrointestinal bleeding secondary to procosigmoiditis were treated with endoscopic Nd:YAG laser therapy. Patients were followed for an average of 21.7 months after the first laser treatment. Average transfusion requirements and hospital admissions per patient-month were 0.93 and 0.27, respectively, in the prelaser period and 0.18 and 0.06, respectively, in the entire period following the first laser treatment. A total of 26 laser treatments were performed. There were three major (prolonged ileus) and one minor (pain) complication. We conclude that endoscopic Nd:YAG laser photocoagulation is a safe, effective, and lasting treatment in severe, symptomatic radiation injury of the lower gastrointestinal tract.

Skin incisions 6 mm in length were made on the backs of hairless mice. Control wounds were closed with interrupted 5-0 Prolene sutures, and experimental wounds were approximated and closed by laser welding using a Nd: YAG laser. The wounds were examined daily, and specimens were excised at weekly intervals for histopathologic study, transmission electron microscopy, tensile strength determination, and type I collagen-specific messenger ribonucleic acid measurements. The laser-welded wounds demonstrated rapid healing. Histologic study showed a functional scar tissue at day 7 and a minimal residue of the original wound at day 14. Tensile strength of the control and experimental wounds was similar at all time points. The levels of collagen-specific messenger ribonucleic acid were significantly higher in the sutured group in comparison with the laser group or with normal control skin. This study suggests that laser welding might have advantages over suturing, since the former is sterile and nontactile, does not require introduction of foreign material into the wound, and provides subjectively improved cosmetic results.

The use of lasers in medicine and surgery has increased slowly-its effectiveness based on trial-and-error clinical experience. Very little comprehensive data has been published that scientifically presents dosage, energy, absorption, and comparisons between types of lasers. Our laboratory has developed a method for taking the guesswork out of laser dosage using scientific data to optimize therapy and give reproducible responses. Experiments were conducted using an argon laser, a neodymium: YAG laser, and a broad-band infrared light source. This preliminary study uses a beam scan technique, which for the first time permits accurate measurement of the laser intensity incident on tissue. Therefore, this protocol allows the standardization of dosage measurements with good experimental reproducibility in biological models. By using this accurate method of measuring the intensity delivered to pigskin, we are able to reproduce for the first time similar histological damage with the different energy sources.

This study compared the histology, biochemistry, tensile strength, and extensibility of Nd:YAG laser-welded and sutured venotomies. Two-centimenter-length bilateral canine femoral or jugular venotomies were evaluated with one vessel (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral vessel (experimental) welded with the Nd:YAG laser (1 W power and 30- to 40-sec exposure). Specimens were removed and examined immediately after fashioning (t0) and at 1, 4, or 5 weeks post-operatively to compare the progression of healing. Histologic examination of the 4- and 5-week sutured wounds had granulomatous reaction around the sutures with areas of excessive collagen accumulation. In contrast, the laser-welded wounds had minimal inflammatory response, near normal collagen content, and minimal residual disorientation and break in the elastic fiber continuity. The rate of collagen synthesis in laser-welded wounds was approximately twice that of sutured wounds at 1, 4, and 5 weeks, and correlated with increased tensile strengths of lasered wounds. The extensibility of the 5-week specimens was 0.19 for sutured and 0.29 for laser-welded wounds as compared to 0.29 for normal vein. These preliminary data suggest that laser welding of venotomies may have several advantages over conventional suture techniques.

• We investigated the histologic and biochemical effects of carbon dioxide and neodymium (Nd)-YAG laser welding on the healing of venotomies. Ten canine femoral venotomies 2 cm in length were approximated and welded with 10 600-nm wavelength, 1-W power over 20 to 25 s for CO 2 laser, and 1060-nm wavelength, 1-W power over 30 to 40 s for Nd-YAG laser. On removal at one to three weeks, all veins (4/4 welded by CO 2 and 6/6 by Nd-YAG) were patent without hematomas. Histologic and biochemical analyses of the venous tissues demonstrated active healing at the venotomy sites. We conclude that the CO 2 and Nd-YAG lasers can be used successfully to weld venotomies and may provide an alternative to conventional suture techniques for repair of vascular lesions. ( Arch Surg 1986;121:905-907)

In 1971, a surgeon named Goodale at the University of Minnesota described the first application of a laser to the gastrointestinal tract.1 He performed open surgery and using a CO2 laser to coagulate diffuse bleeding from the stomach in an attempt to avoid gastric resection. This article inspired other people in the world to look to the possibility of the endoscopic delivery of laser energy for coagulation.

Various laser modalities are currently in extensive use in dermatology and plastic surgery, particularly for treatment of vascular and pigmented lesions. A relatively new area of laser utilization involves the possible biologic effects of the lasers. In this overview, we are summarizing our recent studies, which indicate that lasers at specific wavelengths and energy densities modulate the connective tissue metabolism by skin fibroblasts both in vitro and in vivo. Specifically, the neodymium-yttrium-aluminum-garnet (Nd: YAG) laser was shown to selectively suppress collagen production both in fibroblast cultures and in normal skin in vivo, thus suggesting that this laser modality may be useful for the treatment of fibrotic conditions such as keloids and hypertrophic scars. Furthermore, two low-energy lasers, helium-neon (He-Ne) and gallium-arsenide (Ga-As), were shown to stimulate collagen production in human skin fibroblast cultures, suggesting that these lasers could be used for enhancement of wound healing processes. These experimental approaches illustrate the future possibilities for applying lasers for the modulation of various biologic functions of cells in tissues and attest to the potential role of lasers in the treatment of cutaneous disorders.

CO2, neodymium:yttrium -aluminum- garnet (Nd:YAG), and argonlaser welding of vascular. tissueRodney A. White, R. Patrick Abergel *, Richard Lyons *, Stanley R. Klein,George Kopchok, Richard M. Dwyer *, Jouni Uitto*Departments of Surgery and Medicine *, Harbor -UCLA Medical Center1000 W. Carson Street, Torrance, California 90509AbstractTne feasibility of welding thin- walled microvessels by laser has been established.This report summarizes our experience using laser welding to repair thick -walled, large-diameter, 4 to 8 mm canine veins and arteries using CO2, Nd:YAG and argon lasers. Weldingof venotomies is uniformly successful using CO2 and Nd:YAG lasers, and Nd:YAG venotomiesappear to heal more rapidly than sutured controls. Arterial welding has been accomplishedwitn the Nd:YAG and argon laser. Our preliminary experience shows promise for weldingboth large diameter veins and arteries using lasers. Laser welding may represent analternative for repair of small and large diameter vessels with several advantagescompared to conventional suture techniques.IntroductionVascular surgery has rapidly developed as a specialized field over the past 30 years.Many of the advances have relied on development of blood compatible synthetic polymers foruse as suture and prosthetic materials. Current areas of development in the repair ofvascular lesions require miniaturization of sutures, needles, prosthetic materials andinstruments to yield continued satisfactory results. Development of an expedientnonsuture technique for repairing arterial lesions and making anastomoses would be costand time effective, would reduce the technical difficulty of procedures and would improvethe quality of patient care.Several new techniques have been evaluated for repairing vessels. Automated suturingand stapling devices show some promise for increasing the speed and precision ofprocedures. Biologic adhesives, in particular fibrin glue, show encouraging results forrepair of arteriotomies and are useful adjuncts in forming anastomoses. Recentindications in the literature and preliminary experiments in our laboratory suggest thatlasers are applicable to vascular repair and may have several advantages over conventionaltechniques.This paper reviews our experience using CO2, Nd:YAG and argon lasers to repair otomiesin 4 to 8 mm canine arteries and veins. Previous studj,es "pave established the ability to

Clinical observations have suggested that low energy lasers might stimulate wound healing. To understand the mechanism of the biostimulation, we have previously examined the effects of low energy lasers on collagen production by human skin fibroblasts and reported an increase of collagen synthesis in vitro (J. Am. Acad. Derm. 11:1142-1150, 1980. To examine the effects of low energy lasers in vivo, hairless mice were experimentally wounded, sutured and subjected to laser irradiation by He-Ne laser with a power output of 1.56 mW, and an energy fluence of 1.22 J/cm2. Experimental wounds were subjected to laser treatment every other day, for a total duration of 2 months; control wounds remained untreated. Specimens from the wounds were then examined for histology, tensile strength and total collagen content. Results demonstrated a considerable improvement of the tensile strength of the laser-irradiated wounds at 1 and 2 weeks. Furthermore, the total collagen content was significantly increased at 2 months when compared to control wounds. These results suggest a beneficial effect of He-Ne laser on wound healing in vivo.© (1986) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

LASER energy has previously been shown to control bleeding from superficial gastric erosions in the dog. In the initial report by Goodale et al, 1 carbon dioxide laser energy was transmitted through a rigid, hollow endoscope. Subsequently, Nath et al 2 described a flexible fiberoptic delivery system through which argon laser energy could be transmitted. In 1975, Dwyer et al 3 reported the successful use of such a system to treat hemorrhage from superficial gastric erosions in dogs. This communication describes the use of argon ion laser phototherapy for the treatment of acute upper-gastrointestinal bleeding in man. Materials and Methods An argon ion retinal photocoagulator with a flexible fiberoptic delivery system was attached to the outside of an endoscope as previously reported. 3 The tip of the fiberoptic cable was covered by a protective cap, and the cap was equipped with two channels, one for water to wash the quartz

Applications of lasers in dermatologyGary Lask, R. Patrick Abergel, Richard M. Dwyer and Jouni UittoDepartment of Medicine, Division of DermatologyHarbor -UCLA Medical Center1000 West Carson Street, Torrance, California 90509AbstractLasers have gained considerable use in the field of dermatology for treatment of avariety of cutaneous lesions. In this overview, we are discussing the current applicationsof argon, CO2 and Nd:YAG lasers in dermatology. We are also exploring the future prospectsof laser research in the field of cutaneous biology.IntroductionAlthough lasers were introduced to medicine several years ago, only recently has amultidiciplinary usage been applied to the full spectrum of the clinical medicine.

In this study, we have developed a concept of wound closure by laser welding and studied the wound healing process. In the first set of experiments, six-millimeter long, full-thickness incisions were made in the skin on the back of hairless mice. Control wounds were closed with interrupted 5-0 prolene suture. The experimental wounds were approximated and closed by laser welding using a Nd:YAG (1.06 μm) laser. Selected wounds were excised for histopathology, transmission electron microscopy, tensile strength determination and assay of type I collagen specific messenger-RNA. The laser welded wounds demonstrated rapid healing with good cosmetic results. The tensile strength was identical both for laser welded and sutured wounds at 7, 16, and 21 days. A significant increase of type I collagen specific mRNA was noted in both specimens at 4, 10 and 16 days, but a higher level was recorded in the sutured specimens at day 16 (2652 vs. 911 U/pg total RNA). We further initiated a comparative study to identify the laser which would be most suitable for skin welding. For this purpose argon, Nd:YAG (1.06 μm and 1.32 μm) and CO 2 lasers were used to weld skin. Wound healing, tensile strength and collagen analyses were performed. The results indicated that both argon and Nd:YAG (1.32 μm) lasers achieved the most effective closure. These results suggest that laser welding provides an efficient method for closing skin wounds. The laser welding has clear advantages over conventional suturing techniques, being sterile, non-tactile, not requiring introduction of foreign materials into the wound, and providing improved cosmetic results.

Reprint requests: Garrett 1,~. M.D., Cardiovascular Medicine, Suite 202. LICD Professional Bldg.. 4301 S St., Sacramento, CA 95817. therapy” of heart and circulatory disorders is virtually unexplored. To determine the in vivo feasibility of transmitting laser energy intravascularly for the purposes of visualizing and treating peripheral artery pathoanatomy, a flexible fiberopticscope (Trimedyne, Inc., Arlington Heights, Ill.), equipped with a quartz fiber, was inserted via the left subclavian artery to the aortoiliac bifurcation in open-chest dogs (Fig. 1, A). For improved viewing, blood was diverted by normal saline infusion through the flushing channel of t,he fiberopticscope (Fig. 2, A). In addition, an area within the origin of the right iliac artery was then photoirradiated by a neodymium-YAG laser (five 2 to 3 second bursts of 60 W) (Fig. 2, B). Following these studies, the intervened vessels were removed, thereby verifying that the photoirradiation had indeed produced a lesion of coagulation necrosis (Fig. 1, A and B). Thus this investigation provides the initial demonstration of the practicality of conducting laser energy into living blood vessels and related structures as a new modality in the management of cardiovascular diseases.

• We compared the histologic features, tensile strength, and collagen synthesis of laser-welded and sutured arteriotomies. Four bilateral canine femoral or carotid arteries, 2 cm long, were studied at one through four weeks postoperatively, with one vessel (control) closed with interrupted 6-0 polypropylene sutures and the contralateral vessel (experimental) welded with an argon laser (0.5 W [1417 J/cm 2 ], four-minute exposure per 1-cm length of incision). Histologic examination revealed that laser-welded arteriotomies had less inflammatory reaction, more normal collagen and elastin reorientation, and similar endothelial continuity when compared with the control, sutured wounds. The tensile strength of the one- and two-week laser-welded specimens was less than that of sutured wounds and became approximately equal to sutured repairs at three and four weeks. There were no significant differences in the rate of collagen synthesis. There was no evidence of abnormal healing in the laser-welded specimens, suggesting that argon laser welding may be an alternative to suture repair of arteriotomies. ( Arch Surg 1986;121:1133-1135)