Laser Wounds Research Articles

Effects of endogenous absorption in human albumin solder for acute laser wound closure

Background and Objective Human albumin is currently being used as a biological solder in laser tissue welding. Experiments were performed to characterize the effects of differing albumin concentrations on wound closure when a 1.32 μm Nd:YAG laser is used to repair skin incisions. Materials and Methods In vivo comparison of acute tensile strength was made in full thickness porcine skin wounds using different solder concentrations. Histology of the repairs was also completed to evaluate the thermal denaturation of the tissue and solder. Transmission measurements were completed for nondenatured and denatured albumin solders. Finally, the real time denaturation pattern of different solder concentrations during laser irradiation was investigated. Results A tissue solder consisting of 50% albumin provides the greatest tensile strength for acute in vivo skin closure. The transmission measurements verify that the primary absorber of 1.32-μm laser light was the solder solvent (water). A significant decrease in power transmission occurs when the 25% albumin solder was denatured. The real time denaturation profiles demonstrate that 1.32-μm laser light denatures 25% albumin solder from the outer surface, while in 50% albumin solder, denaturation occurs from within the solder bulk. Wound histology corroborates the pattern of denaturation seen in vitro. Conclusion The combination of 1.32-μm laser light and 50% human albumin solder can be used to create a deep tissue weld resulting in higher acute repair tensile strength. This permits a deep to superficial closure of wounds, which may result in an optimal method of acute closure for full-thickness wounds. Lasers Surg. Med. 23: 18–24, 1998. © 1998 Wiley-Liss, Inc.

Effects of endogenous absorption in human albumin solder for acute laser wound closure.

Human albumin is currently being used as a biological solder in laser tissue welding. Experiments were performed to characterize the effects of differing albumin concentrations on wound closure when a 1.32 microm Nd:YAG laser is used to repair skin incisions. In vivo comparison of acute tensile strength was made in full thickness porcine skin wounds using different solder concentrations. Histology of the repairs was also completed to evaluate the thermal denaturation of the tissue and solder. Transmission measurements were completed for nondenatured and denatured albumin solders. Finally, the real time denaturation pattern of different solder concentrations during laser irradiation was investigated. A tissue solder consisting of 50% albumin provides the greatest tensile strength for acute in vivo skin closure. The transmission measurements verify that the primary absorber of 1.32-microm laser light was the solder solvent (water). A significant decrease in power transmission occurs when the 25% albumin solder was denatured. The real time denaturation profiles demonstrate that 1.32-microm laser light denatures 25% albumin solder from the outer surface, while in 50% albumin solder, denaturation occurs from within the solder bulk. Wound histology corroborates the pattern of denaturation seen in vitro. The combination of 1.32-microm laser light and 50% human albumin solder can be used to create a deep tissue weld resulting in higher acute repair tensile strength. This permits a deep to superficial closure of wounds, which may result in an optimal method of acute closure for full-thickness wounds.

Comparisons of wound healing among excisional, laser‐created, and standard thermal burns in porcine wounds of equal depth

The present study was designed to characterize similarities and differences among three wounding modalities in partial-thickness porcine wounds. We hypothesized that inherent differences, such as endogenous cytokine delivery into excisional wounds or ablation of eschar during laser vaporization, should accelerate the magnitude and sequence of reparative events above the delayed repair that is frequently observed in patients with burns. A constant mid-dermal depth of injury was created by a Padgett dermatome, a computer-controlled pulsed CO(2) laser, or a temperature-controlled metal template. Wounds were harvested after 5, 10, or 15 days. After 5 days, significant resurfacing differences were apparent with values of 54% in excisions, 29% in lasers, and 12% in standard thermal burns. Sequences of fibroblastic proliferation were measurably different among the three wound modalities. At day 5 the bromodeoxyuridine labeling index for fibroblasts showed laser wound levels greater than excision wound levels, which were greater than burn wound levels; but by day 10, the proliferative profiles indicated that burn wound levels were greater than excision wound levels, which were greater than laser wound levels. Capillary areas (an assessment of angiogenesis) differed among the three wound types throughout the study. Peak values were observed at day 5 in both excisional and laser injuries; however, standard thermal burns did not peak until day 10. Both the magnitude and sequence of expression of three matrix metalloproteinases (-1, -2, and -9) differed among the three types of injuries. Laser wounds showed the earliest peak in matrix metalloproteinase-1 expression, whereas burns showed the least expression at day 5. In conclusion, although the three types of wounds undergo similar reparative processes such as reepithelialization, fibroblastic proliferation, angiogenesis, and expression of matrix metalloproteinases, the magnitude and temporal sequences are measurably altered among the three wound modalities. A greater understanding of specific differences within wound environments may lead to more insightful design of interventional wound therapies.

Real-time confocal microscopic observations on human corneal nerves and wound healing after excimer laser photorefractive keratectomy

PURPOSE. Corneal wound healing after excimer laser photore-fractive keratectomy (PRK) passes through a series of characteristic stages which have earlier been defined by means of histological, histochemical, and biochemical approaches. We investigated the potential of confocal microscopy to verify morphological changes in human corneas in vivo after PRK. METHODS. Ten corneas of eight patients that had earlier undergone PRK were examined at different postoperative time points (7 days–34 months). One of the PRK patients was examined sequentially three times. Three additional corneas, which had earlier undergone corneal grafting surgery and then were subjected to excimer laser photoastigmatic keratectomy (PARK), were studied as well. Seven healthy untreated corneas served as controls to define the normal morphology of human cornea. A tandem scanning confocal microscope (TSCM) was used to generate real-time images of the corneas on an S-VHS videotape. The images were either digitized and further processed or the individual video frames were produced with a video printer. RESULTS. Seven days post-PRK in vivo confocal microscopy revealed the presence of morphologically immature surface epithelial cells. Delicate nerves, activated keratocytes and deposition of extracellular light-reflecting scar tissue were perceived. The epithelium appeared normal one month post-PRK. Ongoing activation of the anterior stromal keratocytes along with extracellular scar tissue were detected. We also observed increasing numbers of regenerating subepithelial nerve leashes with somewhat twisted pattern. Highly reflective, presumably activated keratocytes were no longer detected 6–7 months post-PRK. Hypercellularity with scar tissue could still be found up to 30 months post-PRK. Only one cornea examined 34 months post-PRK showed normal keratocyte morphology and recovery of the anterior stroma. However, the morphology of subepithelial nerves was still somewhat abnormal. The two corneal grafts examined 11 or 32 months post-PARK exhibited a normal-appearing epithelium but considerable stromal hypercellularity and extracellular scar deposition. The subepithelial nerves were poorly regenerated in one eye and fairly well detectable in the other. The third graft examined 15 months post-PARK revealed the presence of enlarged surface epithelial cells and dense stromal scarring but no nerves. CONCLUSION. TSCM clinically confirms the earlier histological data on healing of excimer laser wounds. It offers a distinct improvement in the assessment of excimer laser-treated corneas, as it enables cellular details and nerves to be perceived in vivo. In addition the thickness of the stromal scar can be measured for e.g. planning of phototherapeutic keratectomy.

Effects of an erbium, chromium: yttrium, scandium, gallium, garnet laser on mucocutanous soft tissues

Lasers are effective tools for soft tissue surgery. The erbium, chromium: yttrium, scandium, gallium, garnet laser is a new system that incorporates an air-water spray. This study evaluates the cutting margins of this laser and compares healing with laser and conventional scalpel and punch biopsy-induced wounds. New Zealand white rabbits were divided into serial sacrifice groups; the tissues were grossly and microscopically analyzed after laser and convential steel surgical wounding. Wound margins were found to show minimal edge coagulation artifact and were 20 to 40 mm in width. Laser wounds showed minimal to no hemorrhage and re-epithelialization and collagenization were found to occur by day 7 in both laser and conventional groups. The new laser system is an effective soft tissue surgical device; wound healing is comparable to that associated with surgical steel wounds. The minimal edge artifact observed with this laser system should allow for the procurement of diagnostic biopsy specimens.

Scanning electron microscope and immunocytochemical studies of contraction during secondary CO2 laser wound healing in rat tongue mucosa: Evrard L, Nammour S, Dourov N. J Oral Pathol Med 25:72, 1996

Scanning electron microscope and immunocytochemical studies of contraction during secondary CO2 laser wound healing in rat tongue mucosa: Evrard L, Nammour S, Dourov N. J Oral Pathol Med 25:72, 1996

Scanning electron microscopic and immunocytochemical studies of contraction during secondary C02 laser wound healing in rat tongue mucosa

An experimental model was established in which the decrease in surface area of CO2 laser wounds on rat tongues was measured during the healing process. Scanning electron microscopy was used to measure and delineate the outlines of the initial wounds and those of the residual wounds. A 50% decrease in the surface area of the wounds was observed 10 days after surgery during the healing process. At day 30, the scar surface area was less than 10% (7.4%) of the wound surface area at day 2. This contrasts with studies reported elsewhere where only minimal contraction was observed during the healing of CO2 laser wounds. Immunoperoxidase techniques revealed that three different phenotypes of myofibroblasts were present inside the healing area, expressing vimentin, actin and desmin. These persisted until day 30 after CO2 irradiation.

Wound Healing after Laser Surgery

Compared with scalpel wounds, CO2 laser wounds show delays in inflammation, collagen production, reepithelialization, and tensile strength in the early stages of healing. Some of these delays are similar to those seen with electrocautery and burn wounds. Later stages compensate for these early deficiencies, because scalpel and laser wounds become more similar in epithelialization and wound strength over time. Healed CO2 laser wounds tend to have less scar contraction than scalpel wounds. Débridement of initial laser wound char, tissue cooling techniques during lasering, and pulsed modes of laser delivery all seem to result in more rapid, favorable healing. Similar wound healing trends have been seen with the CO2 laser in bone, with other lasers, and with laser vascular and neural anastomosis. Biostimulation with low-level laser energy is a complex subject of ongoing investigations.

Healing of rat mouth mucosa after irradiation with CO2, Nd:YAG, and CO2-Nd:YAG combination lasers.

The healing process of wounds made by a combination laser was studied in 90 rats. The laser system enabled both separate and combined use of CO2 and Nd:YAG laser irradiations. The laser wounds and the control excision wounds made by alligator forceps appeared on both sides of the tongue. Specimens from the wound sites were taken immediately, 6 h, and 1, 2, 4, 7, 11, 21, 28, and 42 days after surgery. The wound-healing process was studied by macroscopic evaluation before preparing the specimens for light microscopy. Some differences were noted in the wound-healing process among the three groups into which the experimental animals were divided. Tissue coagulation damage was most extensive in the Nd:YAG laser sites, where it was observed in its full extent 4 days after surgery. Epithelial cells were seen to begin to proliferate in all the wounds 6 h after surgery. Re-epithelialization was completed by between 7 (CO2) and 21 days (Nd:YAG) at all the wound sites. The inflammatory cell infiltration was more prominent in the Nd:YAG and the CO2-Nd:YAG combination laser wounds than in the CO2 and excision wounds during healing. Tissue regeneration occurred faster with less contraction in the combination CO2-Nd:YAG wounds than in Nd:YAG wounds. The best macroscopic healing result was seen in the CO2 wound sites. The combination laser was effective both at cutting and at coagulating tissue. Combining the CO2 and Nd:YAG laser irradiation into one beam resulted in a greater incision depth than what could have been expected from using the two lasers separately.

193 nm excimer laser sclerostomy in pseudophakic patients with advanced open angle glaucoma.

A modified open mask system incorporating an en face air jet to dry the target area during ablation and a conjunctival plication mechanism, which allows ab externo delivery of the 193 nm excimer laser without prior conjunctival dissection, has been developed to form small bore sclerostomies accurately and atraumatically. Full thickness sclerostomies, and sclerostomies guarded by a smaller internal ostium can be created. A pilot therapeutic trial was conducted in pseudophakic patients with advanced open angle glaucoma. Six full thickness sclerostomies (200 microns and 400 microns diameter) and three guarded sclerostomies were created in nine patients by 193 nm excimer laser ablation (fluence per pulse 400 mJ/cm2, pulse rate 16 Hz, air jet pressure intraocular pressure +25 mm Hg). After 6 months' follow up, intraocular pressure was controlled (< or = 16 mm Hg) in eight of the nine patients (6/9 without medication). Early postoperative complications included hyphaema (trace--2.5 mm) (6/9), temporary fibrinous sclerostomy occlusion (4/9), profound early hypotony (all patients without fibrinous occlusion), and suprachoroidal haemorrhage in one case. Conjunctival laser wounds were self sealing. Small bore laser sclerostomy procedures are functionally equivalent to conventional full thickness procedures, producing early postoperative hypotony, with an increased risk of suprachoroidal haemorrhage in association with this. Further research is required to improve control over internal guarding in excimer laser sclerostomy before clinical trials of this technique can safely proceed.

Experimental Study on the Healing Process of Tongue Wounds Created by CO2 Laser

The CO2 laser has been used in medicine for nearly three decades. Although it had many advantages in the field of oral and maxillofacial surgery, it had limited applications because of its bulky articulated-arm delivery system and so on. Recent improvements such as new flexible fibers and tiny handpieces, however, now allow easy access to any part of the mouth. Nowadays we pay attention to its excellent hemostasis and non-contact surgery in the management of patients with infectious diseases.For the purpose of progressing clinical applications, open and closed wounds which were intended to mimic those produced in clinical oral surgery were created by CO2 laser at rabbit tongue. Then macroscopic and histopathological observations were performed on the healing process of these wounds. And moreover they were compared with scalpel wounds.The results were as follows. Although laser wounds heal slower than scalpel wounds, there is no essential difference in healing process. There is also no difference in the healing process detween open and closed wounds even if the tissue damage extends to the muscle layer.

Expression of growth factors in early wound healing in rat skin

Growth factors are a group of hormone-like polypeptides that have been shown to play a central role in different phases of wound healing. The expression of these growth factors in early wound healing has not been quantified, and the pattern and distribution of these growth factors in early wound healing has not been described completely. Furthermore the quantity and pattern of distribution of these growth factors have not been investigated in early wounds produced by various methods of surgical incision. Comparison of the rate of healing between the CO2 laser wound and the scalpel wound has produced conflicting results. The present immunohistochemical study uses polyclonal antibodies specific for epidermal growth factor (EGF), platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-beta), and basic fibroblast growth factor (bFGF) to observe the pattern and distribution of these growth factors in rat skin wound and elucidate whether there are differences in the expression of these growth factors which might account for the delayed healing of the CO2 laser wounds compared to the scalpel as has been observed by some authors. Our results indicate that EGF, TGF-beta, PDGF, and bFGF are expressed and distributed in same areas of the early skin wound. The area of expression of these growth factors was associated with presence of wound inflammatory cells and wound fibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of thermal damage in precooled CO 2 laser wounds using biological markers

Precooling of the tissues was investigated as a possible means of reducing the thermal damage during CO 2 laser surgery of the oral mucosa. Standard wounds 5 mm long were created with the CO 2 laser, with and without precooling, or the scalpel on the dorsum of tongues. Tissue damage was evaluated by studying changes in mast cells and in the activity of lactate (LDH) and succinate (SDH) dehydrogenase. Cooled unoperated tongues acted as controls. The area of thermal damage, indicated by loss of SDH activity, was significantly smaller in precooled tissues (p < 0.001). Although a similar pattern was detected using LDH, the difference was not significant. At both 0 and 6 h normal mast cell numbers were significantly different between groups (p < 0.02). Furthermore, at 0 time, there were significant differences in the numbers of degranulated mast cells between surgical treatment groups (p = 0.001), although not at 6 h. Total numbers of mast cells (normal and degranulated) did not differ between treatment groups or between 0 and 6 h sampling times. Positive significant correlations were observed between the cross-sectional areas and widths of non-reactive succinate and lactate dehydrogenase and the number of degranulated mast cells around the laser wounds. Analysis of the data demonstrated that (i) uncooled laser wounds but not precooled laser wounds were associated significantly with greater levels of immediate mast cell degranulation than scalpel wounds (p = 0.03); (ii) areas and widths of non-reactive SDH and LDH were larger in non-cooled laser wounds than in precooled ones; (iii) precooling of tissues prior to laser treatment significantly decreased the level of mast cell degranulation immediately after surgery (p = 0.03). These results indicate that tissue damage in CO 2 laser surgery may be reduced by the precooling of tissue, thus improving the quality and results of treatment.

Distribution of tenascin in healing incision, excision and laser wounds.

The distribution of the extracellular matrix glycoprotein, tenascin, was studied in normal mucosa and during healing of scalpel incised or excised and CO2 laser-wounded rat tongue dorsal mucosa in 51 male Sprague-Dawley rats over a period of 21 days. A polyclonal antibody specific for tenascin was applied in indirect immunofluorescence microscopy. In normal mucosa tenascin was sparsely distributed in a discontinuous manner at the tips of the connective tissue papillae in association with the basement membrane (BM) and in the walls of the capillaries. In all the healing wounds there was a marked increase in the distribution of tenascin, particularly close to the BMs at the wound edges beneath the proliferating and migrating epithelium, and later on during healing in the regenerating connective tissue (CT) area. This expression subsided later on during healing. Laser surgery did not alter the ability of fibroblasts to synthesize tenascin. The transient expression of tenascin in the BMs and CT of the healing wounds suggests that this protein could play an important role in providing ideal conditions for cell movement, and in the deposition and organization of other extracellular matrix (ECM) glycoproteins during tissue repair.

Early response of canine temporomandibular joint tissues to arthroscopically guided neodymium: YAG laser wounds

A neodymium yttrium aluminum garnet (Nd:YAG) laser inserted through an operating arthroscope was used to introduce applied energy to synovial tissues, articular discs, and bone in the temporomandibular joint of mongrel dogs. Arthroscopic inspection of the wounds was performed at 1 and 2 weeks postoperatively. The animals were killed and the temporomandibular joints were examined grossly and histologically to determine the extent of injury and healing. The results show that laser wounds of bone and articular disc undergo no repair, whereas laser wounds of synovium show rapid repair. Laser damage to condylar marrow under an articular disc wound was unexpectedly found.

Middermal Wound Healing

Continuous-wave carbon dioxide lasers are not widely used for the surgical removal of most skin lesions because it is difficult to control laser ablation and the extensive laser-induced thermal damage slows healing. Pulsed lasers provide means to reduce thermal damage produced during laser ablation and permit precise control of tissue removed during ablation. Using a swine model, we compared on a gross and microscopic level the healing of middermal wounds of similar depth and area created by a dermatome and a focused pulsed CO2 laser.Pulsed CO2 laser ablation removed skin precisely and bloodlessly with 85 +/- 15 microns (mean +/- SD) of residual thermal damage covering the surface of the wound. Compared with the dermatome, tissue reepithelialization was delayed in the laser wounds at day 3. By day 7, epithelial coverage of the laser-created wounds was not significantly different from the dermatome-created wounds. No significant difference in the appearance of the two wounds was noted at 42 days.We conclude that the focused pulsed CO2 laser is capable of precisely and bloodlessly ablating skin with conservation of residual subjacent adnexal elements, minimal early interference with epibolic epithelial outgrowth, and no pathologic effects on the wound healing process. Pulsed CO2 lasers may be a valuable instrument for the conservative ablation of skin and skin lesions.

Bowenoid Papulosis: Treatment with Carbon Dioxide Laser Vaporization

Two cases of extensive bowenoid papulosis, a unique human papilloma virus infection of genitalia which initially were diagnosed as Bowen disease are reported. Both were treated with CO2 laser vaporization (15 W, continuous wave, power density 1909 watts/cm2) with 1 cm peripheral zone vaporization (15 W, continuous wave, power density 477 W/cm2). The laser wounds healed nicely with no visible scarring. There was no evidence of recurrence after 12 and 18 months follow up, respectively.

Time course of healing of experimental laser and scalpel wounds of the skin

Time course of healing of experimental laser and scalpel wounds of the skin

Fibronectins in healing incision, excision and laser wounds

The distribution of extracellular matrix (ECM) glycoproteins, fibronectins (FNs), was studied in healing scalpel incision, excision and laser wounds of rat tongue dorsal mucosa over a healing period of 42 days by indirect immunofluorescence microscopy using mono- and polyclonal antibodies. A monoclonal antibody (Mab) DH1 was used to detect extradomain-A containing cellular fibronectin (ED-AcFN), and a polyclonal antiserum was utilized to recognize all forms of FNs. In normal tissue ED-AcFN was confined only to the endothelia of larger blood vessels whereas in healing wounds abundant immunoreactive deposits were found in regenerating connective tissue and endothelia of capillaries. The increased content of FNs revealed with both antibodies subsided later on during healing. The results suggest that the locally produced ED-AcFN is essential for tissue regeneration and plays a distinct functional role during wound healing. Laser treatment did not affect the ability of wound fibroblasts to synthesize and deposit cFN. The results provide further evidence that certain embryonic characteristics are seen in regenerating tissue.

A comparison of carbon dioxide laser, liquid nitrogen cryosurgery, and scalpel wounds in healing

With the carbon dioxide surgical laser, the liquid nitrogen cryoprobe, and the scalpel, wounds were created on the shaved abdomen of 24 rats, and the patterns of healing were studied. The laser wounds were the first to epithelialize, followed by the scalpel wounds, with the cryosurgery wounds the slowest to epithelialize. The results were confirmed histologically.