An in vivo histopathological comparison of single and double pulsed modes of a fractionated CO(2) laser

Impact of skin hydration on patterns of microthermal injury produced by fractional CO2 laser

OBJECTIVES

The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO2 laser.

METHODS

A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO2 laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs), (2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT).

RESULTS

Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)).

CONCLUSION

Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO2 lasers, although the clinical implication in the context of laser therapy requires further study.

The Effectiveness of Using CO2 Fractional Laser and Mebo Burn Ointment Together in Treating Scars on the Face after Surgery

Background

This study aimed to investigate the efficacy and safety of CO2 fractional laser combined with Mebo burn ointment in treating facial postoperative scars.

Methods

Sixty patients with facial postoperative scars in the department of plastic surgery of Sun Yat-sen Memorial Hospital from January 2020 to June 2022 were divided into a control group (30 cases) and a study group (30 cases). Both groups received CO2 fractional laser treatment, but the study group also received Mebo burn ointment application.

Results

The study found that both methods resulted in a significant decrease in Sawada score and a significant increase in Investigator Global Assessment score after treatment (P < 0.05), with the study group showing a more significant improvement and higher patient satisfaction (P < 0.05). All patients experienced varying degrees of bleeding, swelling, and erythema immediately after treatment, with two cases of pigmentation and two cases of persistent erythema in the control group, and one case of pigmentation and one case of persistent erythema in the study group. Adverse reactions were minimal, with the study group showing better tolerance.

Conclusions

The study suggests that CO2 fractional laser combined with Mebo burn ointment is an effective and safe treatment for facial postoperative scars.

Ex Vivo Human Histology Fractional Treatment with a New CO2 Scanner: A Potential Application on Deep Scarring

Background and Objectives: For many years, fully ablative laser treatments, particularly those performed with a carbon dioxide (CO₂) laser, were regarded as the gold standard for resurfacing. This study's goal is to assess the depth that can be reached by a new CO₂ scanner system, through a skin model with greater dermal thickness, to use in the treatment of deep scarring. Materials and Methods: Male human skin tissue was laser-treated using a CO₂ fractional laser and a new scanning system, and all samples were fixed in 10% neutral buffered formalin, dehydrated using a series of crescent alcohol, embedded in paraffin, sectioned in series (4-5 µm thick), stained with haematoxylin and eosin (H&E), and then analysed under an optical microscope. Results: From the epidermis through the underlying papillary and reticular dermis to various depths of the dermis, microablation columns of damage and coagulated microcolumns of collagen were observed. The reticular dermis was fully penetrated up to 6 mm at higher energy levels (210 mJ/DOT), resulting in deeper tissue injury. Although the laser might penetrate further, the skin stops there, leaving just the fat and muscular tissue. Conclusions: The deep layers of the dermis can be penetrated by the CO₂ laser system throughout the entire dermal thickness when using the new scanning system, suggesting that this laser's potential impact, at the selected settings, covers all skin targets required to perform superficial or deep treatments on any dermatological issue. Finally, patients who have problems, such as morbid scar-deep complications, which affect their quality of life, are more likely to profit from this innovative technique.

Effects of the lower energy and pulse stacking in carbon dioxide laser skin treatment: an objective analysis using second harmonic generation

PURPOSE

To evaluate the effect of fractional carbon dioxide (CO2) laser treatment using lower power associated with pulse stacking within collagen fibers, using second harmonic generation microscopy and computerized image analysis.

METHODS

Twenty male Wistar rats aging eight weeks were used. Each treatment area received a single-pass CO2 fractional laser with different parameters. The 20 animals were divided into two groups and euthanized after 30 and 60 days. Second harmonic generation images were obtained and program ImageJ was utilized to evaluate the collagen organization within all areas. Collagen anisotropy, entropy and optical density were quantified.

RESULTS

Increased anisotropy over time was observed in all four areas, but only reached statistical significance (p = 0.0305) when the mildest parameters were used (area four). Entropy decreased over time in all areas, but without significance(p = 0.1779) in area four. Density showed an overtime increase only in area four, but no statistical significance was reached (p = 0.6534).

CONCLUSIONS

When combined, the results obtained in this study regarding anisotropy, entropy and density tend to demonstrate that it is possible to achieve collagen remodeling with the use of lower power levels associated with stacked pulses.

A Comparison of Efficacy and Safety of Fractional Carbon Dioxide Laser and Fractional Er:YAG Laser for the Treatment of Xanthelasma Palpebrarum: A Two-Center Randomized Split-Face Controlled Trial

Background: Xanthelasma palpebrarum (XP) is a form of cutaneous xanthoma that presents as collections of yellowish papules or plaques around the eyelids or canthus, affecting patients cosmetically. Objective: This study aimed to compare the efficacy and safety of fractional carbon dioxide (CO₂) laser to that of fractional Er:YAG laser for the treatment of XP. Methods: Two centers recruited patients diagnosed with XP of bilaterally symmetrical lesions. The lesion on one side was randomly assigned to be treated with fractional CO₂ laser while the lesion on the other side was treated with fractional Er:YAG laser. All subjects received up to five treatments, with a 4-week interval between each treatment. Results: Thirty-nine patients completed the study and a total of 82 lesions were available for final assessment. The percentage of "Excellent Improvement" on third and fourth visit was 60.98% versus 39.02% and 90.24% versus 63.41%, respectively, p < 0.05. In a follow-up for 12 to 25 months, the number of lesions recurred on the side treated with fractional CO₂ laser and fractional Er:YAG laser are 9 (22%) and 10 (24%), respectively. Conclusions: In this study, fractional CO₂ laser therapy appears superior since a fewer treatments are required for patients to show significant clinical improvement.

Fundamentals of fractional laser-assisted drug delivery: An in-depth guide to experimental methodology and data interpretation

In the decade since their advent, ablative fractional lasers have emerged as powerful tools to enhance drug delivery to and through the skin. Effective and highly customizable, laser-assisted drug delivery (LADD) has led to improved therapeutic outcomes for several medical indications. However, for LADD to reach maturity as a standard treatment technique, a greater appreciation of its underlying science is needed. This work aims to provide an in-depth guide to the technology's fundamental principles, experimental methodology and unique aspects of LADD data interpretation. We show that drug's physicochemical properties including solubility, molecular weight and tissue binding behavior, are crucial determinants of how laser channel morphology influences topical delivery. Furthermore, we identify strengths and limitations of experimental models and drug detection techniques, interrogating the usefulness of in vitro data in predicting LADD in vivo. By compiling insights from over 75 studies, we ultimately devise an approach for intelligent application of LADD, supporting its implementation in the clinical setting.

Inflammatory responses, matrix remodeling, and re-epithelialization after fractional CO2 laser treatment of scars

BACKGROUND AND OBJECTIVE

Fractional CO₂ laser therapy has been used to improve scar pliability and appearance; however, a variety of treatment protocols have been utilized with varied outcomes. Understanding the relationship between laser power and extent of initial tissue ablation and time frame for remodeling could help determine an optimum power and frequency for laser treatment. The characteristics of initial injury caused by fractional CO₂ laser treatment, the rates of dermal remodeling and re-epithelialization, and the extent of inflammation as a function of laser stacking were assessed in this study in a porcine scar model.

MATERIALS AND METHODS

Full-thickness burn wounds were created on female Red Duroc pigs followed by immediate excision of the eschar and split-thickness autografting. Three months after injury, the resultant scars were treated with a fractional CO₂ laser with 70 mJ of energy delivered as either a single pulse or stacked for three consecutive pulses. Immediately prior to laser treatment and at 1, 24, 96, and 168 hours post-laser treatment, transepidermal water loss (TEWL), erythema, and microscopic characteristics of laser injury were measured. In addition, markers for inflammatory cytokines, extracellular matrix proteins, and re-epithelialization were quantified at all time points using qRT-PCR.

RESULTS

Both treatments produced erythema in the scar that peaked 24 hours after treatment then decreased to basal levels by 168 hours. TEWL increased after laser treatment and returned to normal levels between 24 and 96 hours later. Stacking of the pulses did not significantly increase the depth of ablated wells or extend the presence of erythema. Interleukin 6 and monocyte chemoattractant protein-1 were found to increase significantly 1 hour after treatment but returned to baseline by 24 hours post laser. In contrast, expression of transforming growth factor β1 and transforming growth factor β3 increased slowly after treatment with a more modest increase than interleukin 6 and monocyte chemoattractant protein-1.

CONCLUSIONS

In the current study, the properties of the ablative zones were not directly proportional to the total amount of energy applied to the porcine scars with the use of triple stacking, resulting in only minor increases to microthermal zone (MTZ) depth and width versus a single pulse. Re-epithelialization and re-establishment of epidermal barrier function were observed in laser treated scars by 48 hours post therapy. Finally, many of the inflammatory genes up-regulated by the laser ablation returned to baseline within 1 week. As a whole, these results suggest that microthermal zones created by FXCO₂ treatment re-epithelialize rapidly with the inflammatory response to the laser induced injury largely resolved within 1 week post treatment. Further study is needed to understand the relationship between laser stacking and MTZ properties in human scars in order to evaluate the clinical applicability of the stacking technique. Lasers Surg. Med. 49:675-685, 2017. © 2017 Wiley Periodicals, Inc.

Lower energy and pulse stacking. A safer alternative for skin tightening using fractional CO2 laser

PURPOSE

To evaluate the effect of different energies and stacking in skin shrinkage.

METHODS

Three decreasing settings of a fractional CO2 laser were applied to the abdomen of Twenty five Wistar rats divided into three groups. Group I (n=5) was histologically evaluated for microthermal zones dimensions. Groups II and III (n=10 each) were macroscopic evaluated with freeware ImageJ for area contraction immediately and after 30 and 60 days.

RESULTS

No statistical significance was found within microthermal zone histological dimensions (Group I) in all settings studied. (Ablation depth: 76.90 to 97.18µm; Coagulation depth: 186.01 to 219.84 µm). In Group II, macroscopic evaluation showed that all settings cause significant immediate skin contraction. The highest setting cause significant more intense tightening effect initially, contracting skin area from 258.65 to 179.09 mm2. The same pattern was observed in Group III. At 30 and 60 days, the lowest setting significantly sustained contraction.

CONCLUSION

Lower fractional CO2 laser energies associated to pulse stacking could cause consistent and long lasting tissue contraction in rats.

The Efficacy and Safety of Fractional CO₂ Laser Combined with Topical Type A Botulinum Toxin for Facial Rejuvenation: A Randomized Controlled Split-Face Study

Objective. We evaluated synergistic efficacy and safety of combined topical application of Botulinum Toxin Type A (BTX-A) with fractional CO₂ laser for facial rejuvenation. Methods. Twenty female subjects were included for this split-face comparative study. One side of each subject's cheek was treated with fractional CO₂ plus saline solution, and the other side was treated with fractional CO₂ laser plus topical application of BTX-A. Patients received one session of treatment and evaluations were done at baseline, one, four, and twelve weeks after treatment. The outcome assessments included subjective satisfaction scale; blinded clinical assessment; and the biophysical parameters of roughness, elasticity, skin hydration, transepidermal water loss (TEWL), and the erythema and melanin index. Results. BTX-A combined with fractional CO₂ laser sides showed higher physician's global assessment score, subject satisfaction score, roughness, skin hydration, and skin elasticity compared to that of fractional CO₂ plus saline solution side at 12 weeks after treatment. TEWL and erythema and melanin index showed no significant differences between two sides at baseline, one, four, and twelve weeks after treatment. Conclusion. Topical application of BTX-A could enhance the rejuvenation effect of fractional CO₂ laser.

Fractional carbon dioxide laser resurfacing

Currently available ablative fractional CO2 lasers provide excellent results and diminish down time with fewer complications than previous generation CO2 lasers. Mechanisms of action, treatment parameters, as well as pre- and postoperative care will be discussed.

Topical lidocaine enhanced by laser pretreatment: a safe and effective method of analgesia for facial rejuvenation

BACKGROUND

Injectable forms of anesthesia for nonsurgical facial rejuvenation, although efficacious, are uncomfortable for the patient. Preclinical studies have demonstrated that laser pretreatment at low energies enhances absorption of topical lidocaine.

OBJECTIVES

The authors assess the safety and efficacy of laser-assisted transdermal delivery of topical anesthetic.

METHOD

Ten patients were split into 2 groups (A and B). All patients received 15 g of BLT (20% benzocaine, 6% lidocaine, and 4% tetracaine triple anesthetic cream) for 20 minutes with no occlusion. Then the cream was removed and the first blood draw taken. Group A patients were pretreated with the full ablative laser and group B patients with a fractional ablative laser to the full face. A further 15 g BLT was applied for another 20 minutes. Group A patients then underwent full ablative laser treatment, and group B received fractionated ablative laser treatment. Blood draws were taken at 60, 90, 120, 180, and 240 minutes after the initial topical anesthetic application, and the serum was analyzed for lidocaine and monoethylglycinexylidide (MEGX) levels. Patients were asked to rate the pain felt at intervals during the procedure.

RESULTS

No patient required supplemental nerve blocks. Pain scores were equivalent at the end of the first pass for both groups (P = .436). Group A patients had significantly lower pain scores at the start of the second laser treatment (P = .045), but pain scores became equivalent by the end (P = .323). Combined serum lidocaine and MEGX levels were significantly higher in group A patients up to 90 minutes (peak average of 0.61 µg/mL for group A and 0.533 µg/mL for group B; P = .0253), which corresponded to greater initial analgesic effect.

CONCLUSIONS

Data from this study demonstrate that topical anesthetic for facial rejuvenation can be enhanced with laser pretreatment while maintaining safe blood serum levels. Further studies should examine optimal application amount and time to allow safe multipass facial rejuvenation without the need for invasive nerve blocks.

Efficacy and Safety of 10,600-nm Carbon Dioxide Fractional Laser on Facial Skin with Previous Volume Injections

Background:

Fractionated carbon dioxide (CO₂) lasers are a new treatment modality for skin resurfacing. The cosmetic rejuvenation market abounds with various injectable devices (poly-L-lactic acid, polymethyl-methacrylate, collagens, hyaluronic acids, silicone). The objective of this study is to examine the efficacy and safety of 10,600-nm CO₂ fractional laser on facial skin with previous volume injections.

Materials and Methods:

This is a retrospective study including 14 patients treated with fractional CO₂ laser and who have had previous facial volume restoration. The indication for the laser therapy, the age of the patients, previous facial volume restoration, and side effects were all recorded from their medical files. Objective assessments were made through clinical physician global assessment records and improvement scores records. Patients’ satisfaction rates were also recorded.

Results:

Review of medical records of the 14 patients show that five patients had polylactic acid injection prior to the laser session. Eight patients had hyaluronic acid injection prior to the laser session. Two patients had fat injection, two had silicone injection and one patient had facial thread lift. Side effects included pain during the laser treatment, post-treatment scaling, post-treatment erythema, hyperpigmentation which spontaneously resolved within a month. Concerning the previous facial volume restoration, no granulomatous reactions were noted, no facial shape deformation and no asymmetry were encountered whatever the facial volume product was.

Conclusion:

CO₂ fractional laser treatments do not seem to affect facial skin which had previous facial volume restoration with polylactic acid for more than 6 years, hyaluronic acid for more than 0.5 year, silicone for more than 6 years, or fat for more than 1.4 year. Prospective larger studies focusing on many other variables (skin phototype, injected device type) are required to achieve better conclusions.