Parameters in fractional laser assisted delivery of topical anesthetics: Role of laser type and laser settings

Background and Objectives: Efficacy of topical anesthetics can be enhanced by pretreatment of the skin with ablative fractional lasers. However, little is known about the role of parameters such as laser modality and laser density settings in this technique. Aims of this study were to compare the efficacy of pretreatment with two different ablative fractional laser modalities, a CO2 laser and an Er:YAG laser, and to assess the role of laser density in ablative fractional laser assisted topical anesthesia. Study Design/Materials and Methods: In each of 15 healthy subjects, four 10 × 10 mm test regions on the back were randomized to pretreatment (70–75 μm ablation depth) with CO2 laser at 5% density, CO2 laser at 15% density, Er:YAG laser at 5% density or Er:YAG laser at 15% density. Articaine hydrochloride 40 mg/ml + epinephrine 10 μg/ml solution was applied under occlusion to all four test regions. After 15 minutes, a pass with the CO2 laser (1,500 μm ablation depth) was administered as pain stimulus to each test region. A reference pain stimulus was given on unanesthetized skin. The main outcome parameter, pain, was scored on a 0–10 visual analogue scale (VAS) after each pain stimulus. Results: Median VAS scores were 1.50 [CO2 5%], 0.50 [CO2 15%], 1.50 [Er:YAG 5%], 0.43 [Er:YAG 15%], and 4.50 [unanesthetized reference]. VAS scores for all pretreated test regions were significantly lower compared to the untreated reference region (P < 0.01). We found no significant difference in VAS scores between the CO2 and the Er:YAG laser pretreated regions. However, VAS scores were significantly lower at 15% density compared to 5% density for both for the CO2 laser (P < 0.05) and the Er:YAG laser (P < 0.01). Pretreatment with the CO2 laser was considered slightly more painful than pretreatment with Er:YAG laser by the subjects. Conclusion: Fractional laser assisted topical anesthesia is effective even with very low energy settings and an occlusion time of only 15 minutes. Both the CO2 laser and the Er:YAG laser can be used to assist topical anesthesia although the CO2 laser pretreatment is experienced as more painful. In our study settings, using articaine/epinephrine solution and an occlusion time of 15 minutes, a density of 15% was more effective than 5%. Lasers Surg. Med. 50:813–818, 2018. © 2018 Wiley Periodicals, Inc.