Wart Removal and RF Ablation

Introduction

Radiofrequency ablation (radiosurgery, high frequency electrosurgery) is a dermatosurgical procedure that aims at the surgical management of benign and malignant skin conditions by using various forms of alternating current at ultra high frequency (500-4000 kHz). It is also popularly known as “poor man’s laser” or “cold cautery”. The most common form of radiofrequency ablation used in dermatology involves the application of high-voltage electromagnetic energy in the form of a damped sine wave. This form of current may be applied by electrofulguration, electrodessication or electrocoagulation. Radiofrequency ablation (RFA) has gained importance in the recent years as it is highly effective in the cutting of the skin lesions with adequate hemostasis at the same time because of good coagulation. Radiofrequency can be used for incisional techniques that produce full-thickness excision of nevi, shave techniques that produce partial-thickness removal of superficial lesions and removing vascular lesions such as hemangiomas or pyogenic granulomas.

How Radio Frequency Ablation Works

Radiofrequency works on the principle of increasing the frequency and voltage while simultaneously decreasing the amperage of alternating current so as to generate oscillating radiowaves. These radiowaves are further modified to produce different waveforms that are passed into the lesion. Modern high-frequency radiosurgical devices transfer electrical energy to human tissue via a treatment electrode that remains cool. The electrical resistance of human tissue helps in converting this electrical energy into molecular energy; this causes the denaturation of intracellular and extracellular proteins, thereby resulting in coagulation or desiccation effects. Increasing the temperature of the intracellular water above the boiling point (400-600ºC) causes the cell membrane to rupture, thereby producing a cutting effect. The lateral spread of heat results in the residual thermal damage by causing dehydration and coagulation necrosis of the tissue proteins and carbonization.

  Radiofrequency Equipment and Tissue Effects

The basic equipment comprises a radiosurgical unit with a ground plate (dispersive electrode), foot switch and hand piece. It is provided with tungsten electrodes of various shapes and sizes with bendable shafts that are fitted into hand piece. A suction device for the evacuation of smoke in extensive surgery is also attached to the equipment. Radiofrequency uses various waveforms with the following tissue effects. 

a. Electrosection: The fully filtered and rectified waveform applied to the tissues in biterminal fashion provides a smooth cutting current resulting in elecrosection. An electrode tip in the shape of a fine needle, wire loop, diamond, ellipse or triangle is advanced slowly through the tissue, causing a steam envelope to advance around the tip and producing a smooth cutting effect. The fully rectified current simultaneously produces cutting and coagulation. This waveform produces least amount of lateral heat spread with minimum tissue destruction.

b. Deep tissue destruction (electrocoagulation): The partially rectified waveform applied to the tissues in a biterminal fashion causes electrocoagulation. It gives instant homeostasis and is used in the treatment of the vascular lesions in which coagulation is primarily required.

c. Superficial tissue destruction (electrodessication and electrofulguration): This is achieved by the application of markedly dampened current to tissues in monoterminal or biterminal fashion. Fulguration causes the greatest amount of lateral heat spread and has a potential dehydrating effect. It causes the superficial tissue destruction through dehydration and surface carbonization. The electrode is held at a distance from the skin lesion in fulguration, while the tissue is touched with the electrode in desiccation.

Anesthesia

Local anesthetic, i.e., lignocaine is administered before most radiosurgical techniques. The use of lignocaine with epinephrine further reduces blood loss, but the use of epinephrine at the tips of digits and the nose should be avoided. Another alternative is to use a eutectic mixture of local anesthetics (EMLA) cream that contains 2.5% lidocaine and 2.5% prilocaine. It is applied under occlusion to skin at least 1 h before the procedure to achieve topical anesthesia. Anesthesia may not be necessary for the electrosurgery of small lesions such as telangiectasias and small skin tags.