Thermal therapy remains a cornerstone in the endoscopic management of gastrointestinal bleeding. The mechanism by which thermal therapy achieves hemostasis is related to multiple factors, including coagulation of tissue protein, contraction of vessels, edema, coaptation, and indirect activation of the coagulation cascade with promotion of intravascular fibrin thrombi.¹ Thermal devices deliver heat to tissues in one of two ways: (1) indirectly by passage of electric current through tissue (i.e., bipolar probe, Fig. 36.1) also called electrosurgery or (2) via direct heat transfer (i.e., heater probe, Fig. 36.2), also called electrocautery.

Bipolar electrosurgery delivers thermal energy by completion of an electrical circuit between two electrodes via nondesiccated tissue. As the bipolar probe contains the ground terminal within the probe, a grounding pad is not needed. As the treated tissue desiccates, the resistance increases, thereby limiting the breadth and depth of tissue injury.² Some versions of the probe come with both irrigation as well as an injection needle for application of epinephrine. Optimal technique employs lower power settings (i.e., 15 W) for longer durations (10 to 12 seconds).³

The heater probe consists of a Teflon-coated hollow aluminum cylinder with an irrigation port, an inner heating coil, and a distal thermal couple, with the latter maintaining a constant temperature.⁴ The Teflon is designed to prevent probe adherence to the developing coagulum. Once treatment is initiated with a foot pedal, the duration of activation cannot be stopped until the entire amount of preselected joules is delivered.⁵

Both bipolar and heater probe require application of pressure to the target tissue to ensure coaptive sealing of the vessel walls to obliterate the lumen.

The argon plasma coagulation (APC) delivery catheter is a monopolar, noncontact probe which both emits inert argon gas and contains an electrode that ionizes this gas flow. When inert argon is ionized, it is converted to argon plasma which is conducted by an “arc” to the nearest tissue, producing coagulation necrosis to a depth of penetration of approximately 2 to 3 mm. The directionality of the argon plasma flow can be axial, circumferential (Fig. 36.3), or perpendicular (“side fire”). In the
application of APC, carbonization (or “char”) should be kept to a minimum. Inadvertent contact with tissue can cause pneumatosis as a result of intramural dissection of argon gas.