Superficial Electrosurgery: To Numb or Not to Numb?

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Sebaceous hyperplasia is a common condition for which many patients seek treatment. Therapy principally entails physical flattening and diminution of the overactive sebaceous glands, and modalities include electrodesiccation, excision, and laser therapy, although systemic retinoids have been reported to be effective as well.1 In our practice, superficial very low-power electrodesiccation is the mainstay of the treatment of sebaceous hyperplasia. Depending on the patient's pain tolerance, when lesions are numerous, 30% topical lidocaine in an ointment base may be applied for at least 30 minutes before the procedure to make the treatment more comfortable. Interestingly, we have noted that regardless of discomfort or pain tolerance, some patients have declined the use of topical anesthesia, citing that they noted less pain when topical anesthetics had been applied but also less effect of the treatment so much so that they preferred the more effective, more uncomfortable approach. After similar requests from several patients, we wondered why topical lidocaine would affect the perceived efficacy of superficial electrodessication.
To answer this question, an understanding of the basic principles of electrosurgery is essential. In electrosurgery, an electrical current is generated and concentrated at the active electrode. Once the current comes in contact with the skin, the impedance (resistance) of the tissue to the current generates heat, and therefore localized tissue injury.2 The greater the resistance, the more heat that is generated, and the greater the tissue destruction. What happens to cutaneous resistance when a topical ointment is applied to the skin? Even with just 1 hour of application, topical petrolatum increases skin hydration by forming an occlusive barrier that prevents transepidermal water loss.3 Well-hydrated skin is 14-fold less resistant than dehydrated skin.4 This hydration decreases resistance and thereby decreases heat generated when in contact with a passing current. This dampening of heat superficially, although may be protective in other procedures such as ablative laser therapy, may explain why patients have noted less than desirable results after electrodessication which has been preceded by topical anesthetic application.
This observation is of potential use to the practitioner as it delineates the possibility that topical numbing applications may have an effect on superficial electrosurgical procedures, and technique may need to be adjusted to achieve the desired outcome. This simple reflection highlights that no matter how minute or routine a procedure or preparatory technique may be, an understanding of the basic mechanisms, principles, and effects of those techniques is of utmost importance to maximize results and achieve patient satisfaction.
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