The number of office procedures involving a needle-based approach using botulinum toxins and various fillers is increasing steadily. Other procedures that may induce pain in an office setting can be laser treatments and chemical peelings. However, despite the dramatic results these office-based procedures provide, there are some complaints of pain, which may lead to refusal of repeated sessions.1,2
The purpose of this study was to determine the efficacy of a skin-cooling device against injection-related pain. This prospective study involved a total of 50 patients injected with botulinum toxin on the bilateral periorbital region. The patients were divided into three treatment groups. Group 1 was treated with the topical skin-cooling device (metallic plate constant at –8°C applied on the skin before each injection for a duration of 6 seconds) on one side, and the other side served as a control (n = 15). Group 2 was treated with topical anesthetic cream [EMLA (eutectic mixture of lidocaine and prilocaine) applied 60 minutes before injection] on one side, and the other side served as a control (n = 15). Group 3 was treated with a skin-cooling device on one side, and the other side was treated with anesthetic cream (n = 20). A visual analogue scale was used to measure pain intensity to compare both sides. In group 1, the average pain score on the skin-cooling device was 1.8 compared with 2.8 on the control side (p < 0.005). In group 2, the average pain score on the topical anesthetic side was 2 compared with 3.13 on the control side (p < 0.006). In group 3, the average pain score with the skin-cooling device (CoolSkin; Elbio, Seoul, Korea) was 2.9 compared with 2.4 on the side treated with topical anesthetics, which was not statistically significant (p = 0.213) (Fig. 1).
The skin-cooling device uses the concept of the Peltier effect, resulting in thermoelectric refrigeration. When electric current flows through the Peltier element, one side is heated and the other side becomes cold. The cold plate is maintained at a temperature of –8°C. Contact with the cold surface for 6 seconds leads to a rapid drop in skin temperature at 9 ± 3°C, causing the anesthetic effect (Fig. 2). The effect of CoolSkin when compared with control demonstrated a significant decrease in pain and, when compared with topical EMLA cream, demonstrated similar efficacy. This can be explained by the effect of cold on sensory nociceptors, decreased conduction time, and synaptic activity in peripheral nerves.3 The sensory conduction velocity showed an 18.3 percent decrease after 16 minutes of ice application.3 The alternation of nerve velocity begins at 27°C, and analgesia can be achieved at 13.6°C skin temperature when tested with pin prick.4 It has also been reported that nerve transmission ceases between 9°C and 18°C, and it takes approximately 9 minutes of ice application to achieve this temperature.5 When the temperature of the skin rises back to 15.6°C, the pain returns when pricked with a pin.4
In conclusion, the skin-cooling device, by achieving a sudden and brief temperature of the skin at 9 ± 3°C, significantly decreases injection-related pain.
Dong Wan Seo, M.D.
Joon Pio Hong, M.D., Ph.D., M.M.M.
Department of Plastic Surgery
Asan Medical Center
University of Ulsan College of Medicine
This study was supported, in part, by the Daewoong Pharmaceutical Co.
1. Dutton JJ. Botulinum A toxin in the treatment of craniocervical muscle spasms: Short and long-term, local and systemic effects. Surv Ophthalmol.
2. Grandas F, Elston J, Quinn N, Marsden CD. Blepharospasm: A review of 264 patients. J Neurol Neurosurg Psychiatry
3. Lee JM, Warren MP, Manson SM. Effect of ice on nerve conduction velocity. Physiotherapy
4. Bugaj R. The cooling, analgesic, and rewarming effects of ice massage on localized skin. Phys Ther.
5. Kanlayanaphotporn R, Janwantanakul P. Comparison of skin surface temperature during the application of various cryotherapy modalities. Arch Phys Med Rehabil.
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