Lateral thermal damage along pulsed laser incisions

The damage adjacent to incisions created in dorsal mouse skin by overlapping Er3+ and CO2 laser pulses of a duration of 250 microseconds is investigated histologically. It is compared to injuries induced by long-term heating. We demonstrate how the lateral thermal damage near the laser cuts can be explained by heat conduction. We show that it is necessary to introduce as a heat reservoir a layer of tissue that has been liquified during the cutting process. The width of the thermally damaged region depends mainly on the extension of the liquid material that remains in the cut after the laser-tissue interaction.     

Closure of skin incisions in rabbits by laser soldering: I: Wound healing pattern

BACKGROUND AND OBJECTIVES: Temperature-controlled tissue laser soldering is an innovative sutureless technique awaiting only solid experimental data to become the gold-standard surgical procedure for incision closure. The goals of the current study were: (1) to define the optimal laser soldering conditions, (2) to explore the immediate skin reparative healing events after sealing the wound, and (3) to determine the long-term trajectory of skin wound healing. STUDY DESIGN/MATERIALS AND METHODS: Skin incisions were generated over rabbit dorsa and were closed using different wound-closure interventions, in three groups: (a) closure, using a temperature-controlled infrared fiberoptic CO2 laser system, employing 47% bovine serum albumin as a solder; (b) wound closure by cyanoacrylate glues; and (c) wound closure by sutures. The reparative outcomes were evaluated macroscopically and microscopically, employing semi-quantitative grading indices. RESULTS: Laser soldering of incisions at T = 65 degrees C emerged as the optimal method achieving immediate wound sealing. This in turn induced accelerated reparative events characterized by a reduced inflammatory reaction, followed by minimal scarring and leading to a fine quality healing. CONCLUSIONS: Temperature-controlled laser soldering offers an accelerated wound reparative process with numerous advantages over the conventional methods. Further investigations may reveal additional benefits in the spectrum of advantages that this innovative surgical technology has to offer. This can introduce new scientific insight that will pave the way for clinical use.     

Effects of overlap and pass number in CO2 laser skin resurfacing: a study of residual thermal damage, cell death, and wound healing

BACKGROUND: Newer CO2 laser systems incorporating short pulse and scanning technology have been used effectively to resurface the skin. As the number of resurfacing cases has increased, hypertrophic scarring has been reported more commonly. Previous dermabrasion and continuous wave CO2 studies have suggested that depth of injury and thermal damage are important predictors of scarring for a given anatomic region. To determine whether rapid overlapping of laser pulses/scans significantly altered wound healing, we examined residual thermal damage, cell death, and histologic and clinical wound healing in a farm pig. METHODS AND MATERIALS: Two popular CO2 systems were used, with a range of radiant exposures, degrees of overlap, and numbers of passes. Thermal damage was assessed by histology, and dermal cell viability was measured with nitrotetrazolium blue staining. Presence or absence of clinical scarring was determined by textural change and loss of skin markings. RESULTS: We observed that dermal thermal damage did not increase significantly with pass number when performed as in the normal clinical setting (for 2-4 passes); however, by delivering rapidly overlapping pulses and scans, residual thermal damage and cell death depth were increased as much as 100% over areas without immediate overlap of laser impacts. CONCLUSIONS: Immediate overlapping of CO2 laser pulses and scans is a significant risk factor in increasing thermal damage, cell death, and possibly scarring.     

Wound healing in denervated rat skin

Recently, several reports have suggested that innervation influences wound healing. However, some investigators have reported that nerve injury prevented wound healing while others have suggested it had no influence on full-thickness skin wound healing. We created denervated skin areas on rats by dissection of the spinal hemicord. Subsequently, 15-mm-diameter skin defects were made symmetrically within the denervated area on the right side of the back and the normal innervated area on the left side. Biopsies were performed at 3, 7, and 14 days after wounding. We measured changes of the wound surface area, the rate of wound contraction, and the rate of epithelialization. The differences were not significant at 3 or 7 days after the operation. However, we could observe significantly delayed wound healing of the denervated skin areas compared to the normal areas at 14 days. Both wound contraction and epithelialization were delayed in the denervated groups. Our results suggest that sensory disturbance is a negative factor for skin wound healing.     

Wound healing of laser injured skin with glycerol monooleicate cubic liquid crystal

Laser has found increasingly wider applications in the medical filed, but laser is likely to cause damage to patients’ skin. In this experiment, we were surprised to find that glyceryl monooleate (GMO)-based cubic liquid crystal had excellent healing effect on the skin of guinea pigs damaged by laser. Transepidermal water loss (TEWL), H.E. pathology, Masson trichrome dyeing, interleukin-6 (IL-6) levels and the percutaneous depth of fluorescein isothiocyanate (FITC) dyeing were used to evaluate the therapeutic effect of GMO-based cubic liquid crystals against laser damage of different degrees among guinea pigs. GMO-based cubic liquid crystals had an obvious effect in the treatment of slight and moderate laser damage. This finding may provide a effective medical treatment protocols for laser skin damage.     

Wound sterilization: CO2 laser versus iodine

Control of infection in a surgical wound remains a challenge, especially if further surgery in the area is needed. This study was designed to compare the effectiveness of sterilization of a standard experimental infected wound by surgical skin preparation (Betadine) as compared to treatment with the CO2 laser. Standard wounds (5 x 6 cm) were created superficial to the panniculus carnosus on each flank of 37 adult male New Zealand rabbits. Each wound was infected with a standard dose of Pseudomonas aeruginosa. All wounds became grossly infected. On the third day one flank wound was treated with the CO2 laser, the other with the Betadine solution, and a punch biopsy (4 mm) was taken from each wound for quantitative bacterial counts. Less than 10% of the laser-treated wounds grew Pseudomonas, whereas nearly 40% of the iodine-treated wounds remained infected (P less than 0.005). Our early clinical experience using the CO2 laser for the sterilization of infected wounds is also reported.     

Wound healing and physiology of skin flaps

This article focuses on the dynamic process of wound healing, including the three phases of wound healing and the different types of wound healing. The physiology of skin flaps is described, with a focus on the vascular supply and biomechanics of skin flaps. The article reviews older and newer concepts of skin flap design.     

Wound healing in porcine skin following low-output carbon dioxide laser irradiation of the incision

Wound healing of scalpel incisions to the depth of adipose tissue closed with conventional methods was compared with closure by low-output carbon dioxide laser irradiation. In 3 Pitman-Moore minipigs wound healing was evaluated at intervals from 1 to 90 days by the following methods: clinical variables of wound healing; formation of the basement membrane components bullous pemphigoid antigen, laminin, and fibronectin; and histological evaluation of the regeneration of the epidermis, neovascularization, and elastin and collagen formation. There was no significant difference in healing between wounds closed by the various conventional methods and by the low-output carbon dioxide laser.     

Ultraviolet laser ablation of skin: healing studies and a thermal model

We have followed the course of healing of incisions made with the krypton-fluoride excimer laser. Incisions were made in guinea pig skin, in vivo, under identical conditions of irradiation. The progressive healing of these incisions was followed over the course of 3 weeks. We noted excellent healing with re-epithelialization, and the re-formation of collagen fibers with minimal fibrosis. We present a simple thermal model for ablation of tissue by a short pulse of strongly absorbed laser radiation.     

CO2 laser physics and tissue interactions in skin

BACKGROUND AND OBJECTIVES: The theoretical model of CO2 laser tissue interaction appeared to be too simplistic. To explain the reactions seen in skin, a more complex model was needed. We hoped to correlate the clinical-histologic patterns of CO2 laser tissue interactions. STUDY DESIGN/MATERIALS AND METHODS: The Ultrapulse CO2 laser was used on normal and pathologic skin conditions. Clinical observations were correlated with histologic examinations of biopsies. RESULTS: It was possible to demonstrate cavitation at the dermal-epidermal junction 2-3 diameters beyond the actual spot of CO2 laser contact with the skin. Dermal heat damage was seen as homogenization of collagen 1-2 diameters beyond the spot of laser contact. This flow of energy laterally at the dermal-epidermal junction and vertically down the skin follicles was both clinically beneficial and detrimental. Beneficially, superficial skin lesions separated at this junction and were easily removed. The heat coagulation of the dermis facilitated lesion removal without bleeding. The clinician had a better view of the pathology and could find focal zones of deeper pathology that could be easily re-treated. Detrimentally, this extended damage delayed wound healing and led to persistent erythema. CONCLUSION: These clinical-histologic correlations have provided a better understanding of CO2 laser tissue interactions in skin. It has been possible to take advantage of these findings to remove pathologic skin conditions more efficiently.     

Wound healing in radiated skin: pathophysiology and treatment options

Ulcers in radiated skin continue to be a challenge for health care practitioners. Healing impairment in the setting of radiation-damaged tissue will most of the time lead to chronic wounds that reduce the patient's quality of life. In this review, we present an update of the pathophysiology of tissue damage caused by radiation that leads to chronic ulceration. We also explore the evidence available on the different prevention and treatment modalities that have been reported in the literature. The evidence for most preventive measures is inconclusive; however, sucralfate and amifostine seem to be the adequate recommendations for prophylaxis. As for treatment of ulcerated patients, the strongest level of evidence found was for the use of pentoxifylline, but proper trials are still scarce to be considered standard adjuvant therapy. Hyperbaric oxygen, cytokines and other growth factors and surgical interventions have shown some benefit in case reports and case series only. Other therapies show promise based on their mechanism of action but need to be tested in human studies and clinical trials.     

Reduction in lateral thermal damage using heat-conducting templates: a comparison of continuous wave and pulsed CO2 lasers

BACKGROUND AND OBJECTIVES: The advantages of the continuous wave (c.w.) CO(2) laser are offset by the delay in laser wound healing secondary to thermal damage. We have developed novel heat-conducting templates to reduce laser thermal damage. Because shortened pulse durations also decrease thermal damage, we tested the effectiveness of heat-conducting templates with a c.w. CO(2) clinical laser and a short-pulsed CO(2) laser to determine the best method and mechanism to minimize thermal damage. STUDY DESIGN/MATERIALS AND METHODS: Comparison of 0.2-second shuttered c.w. and 5-microsecond pulsed CO(2) lasers were made by doing incisions on 150 tissue samples from reduction mammoplasties and abdominoplasties. Copper, aluminum, glass, and Plexiglass heat-conducting templates were tested against no template (air) with both lasers. Histological samples were evaluated using computerized morphometrics analysis. RESULTS: Statistically significant reductions in lateral thermal damage were seen with the copper (50%) and aluminum (39%) templates used with the c.w. CO(2) laser. Only the copper template (39%) significantly reduced thermal damage when used with the pulsed CO(2) laser. Less thermal damage was seen using the pulsed CO(2) laser compared to the c.w. CO(2) laser with each template. CONCLUSIONS: Heat-conducting templates significantly reduced the amount of lateral thermal damage when used with the c.w. CO(2) laser (copper and aluminum) and short-pulsed CO(2) laser (copper). The c.w. CO(2) laser with the copper template compared favorably to the short-pulsed CO(2) laser without a template. Therefore, both heat conductive templates and short-pulse structure provide successful methods for reducing lateral thermal damage, and a combination of the two appears to provide optimal results.     

Wound healing in normal and analbuminemic (NAR) rats

It has been suggested by several investigators that hypoalbuminemia results in impaired wound healing. In most studies, however, hypoalbuminemia is a manifestation of malnutrition or underlying liver disease. In this study, we examined the effect of isolated hypoalbuminemia on wound healing. Analbuminemic (NAR) rats which are Sprague-Dawley mutants with trace levels of plasma albumin due to a defect in albumin synthesis were studied. Adult NAR and Sprague-Dawley rats (n = 10 each) underwent a 7 cm dorsal skin incision and implantation of a polyvinyl alcohol sponge subcutaneously under pentobarbital anesthesia. Seven days postoperatively all rats were killed with ether, the wounds were excised, and breaking strength was measured. Sponge hydroxyproline content was determined colorimetrically. There were no significant differences in wound breaking strength (fresh or formalin fixed) or sponge collagen content between the Sprague-Dawley and analbuminemic rats. We conclude that isolated hypoalbuminemia has no detrimental effect on would healing in rats.     

点阵CO2激光作用小鼠皮肤光老化模型后创面愈合过程中皮肤超微结构的变化

目的:观察点阵CO2激光作用小鼠皮肤光老化模型后创面愈合过程表皮的超微结构的变化规律。方法:将5只昆明小鼠以UVB紫外线照射,制备成皮肤光老化模型,行点阵CO2激光(Deep FX)干预,观察激光创面愈合情况,并且分别于干预前、干预后第1、3、7、15天取材,进行HE染色和电镜观察。结果:点阵CO2激光作用于小鼠皮肤光老化模型后,术后第1天,见激光损伤灶周围变性组织及细胞水肿,成纤维细胞线粒体体积增大;术后第3天见表皮细胞向创底迁移,成纤维细胞出现增生,细胞内线粒体增多,粗面内质网扩张,胶原纤维见周期性横纹;术后第7天激光损伤灶创底见表皮细胞增殖,创面基本愈合,成纤维细胞增生活跃,线粒体、粗面内质网丰富,内质网扩张明显、胶原纤维增多增粗;术后第15天,成纤维细胞趋于稳定,胶原纤维排列密集。结论:点阵CO2激光通过对表皮的线粒体、粗面内质网产生影响,达到对光老化皮肤良好疗效。     

Delayed primary closure: Collagen synthesis and content in healing rat skin incisions

The rate of collagen synthesis was determined by measuring the specific activity of [³H]hydroxyproline 10, 20, and 60 days postoperatively in order to elucidate differences previously found in the mechanical strength of delayed primary closure (DPC) and primary closure (PC) wounds in rat skin. The rate of collagen synthesis was significantly higher in the DPC wounds than in the PC wounds during the time period studied. At the same time, the collagen content was lower in the DPC wounds on the 10th postoperative day. There were no differences in collagen content on the 20th or on the 60th postoperative day. These data suggest that there is more degradation of collagen in DPC wounds, starting at the 20th postoperative day. Differences in the rates of collagen synthesis in DPC and PC wounds are compatible with previously found differences in the gains of mechanical strength. It is suggested that the superior mechanical strength of DPC wounds is a result of a higher remodeling activity of collagen in DPC wounds.     

Periocular skin reshaping by CO2 laser coagulation

When blepharoplasty is performed by transconjunctival route, sometimes the excess of skin created by overlaxness of the lower lid does not retract to achieve the desired cosmetic result. We propose a method for controlled retraction of the eyelid by coagulating the skin using the CO₂ laser. Thanks to this approach, the lower eyelid's tone recovers and the desired cosmetic appearance is achieved. Results of 37 patients that were treated by 10 W CO₂ laser, 5-mm defocused beam diameter, and pulses of 100 ms, are presented. Follow-up shows that periocular skin reshaping by CO₂ laser for laxened eyelid is a safe method and it can be considered a good alternative of treatment for blepharochalasis without skin excision.