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Ebook Practical pediatric gastrointestinal endoscopy (2/E): Part 2

(BQ) Part 2 book “Practical pediatric gastrointestinal endoscopy” has contents: Polypectomy, endoscopic application of mitomycin C for intractable strictures, endoscopic retrograde cholangio-pancreatography in children, endoscopic pancreatic cysto-gastrostomy, and other contents. | 8 Polypectomy George Gershman KEY POINTS • Knowledge of the principles of electro-surgery is an essential component of safe polypectomy technique. • Knowledge of snare designs and choosing the appropriate snare are essential parts of a successful polypectomy. • Navigation of the scope to an optimal position and a clean environment create an optimal condition for a safe polypectomy. Basic principles of electrosurgery The cornerstone of electric cutting and coagulation of living tissue is the heating of the restricted area by radio-frequency alternating current (RF) without stimulation of nerves and muscles. When current alternates up to a million times per second it does not stimulate muscle and nerve membranes long enough to induce depolarization before the next alternation occurs. Cutting is produced by rapid and strong heating, which creates evaporation of intra-and extracellular fluids. Coagulation is initiated when the speed and degree of tissue heating is slower and less intense, leading to cellular desiccation. Specific effects of different types of RF currents and heat-related tissue destruction are illustrated in Figures 8.1 and 8.2. Several factors regulate the degree of tissue heating: • The size and the shape of the polyp dictates the choice of the proper technique. • Short distances (less than 2 cm) between the tip of the snare and a polyp, minimal opening of the metal loop and simultaneous advancement of the snare toward the polyp, along with tightening of the loop are the key elements of the technique. • Polypectomy of a large polyp requires additional training in the piece-meal technique. • Voltage (V) is the force required to push current through the tissue. The higher the voltage, the deeper the thermal tissue destruction. • Tissue resistance (R) or impedance (for alternating current) is the force generated by tissue to resist electrical flow. It is directly proportional to the amount of tissue electrolytes. Resistance increases dramatically .