Argon plasma coagulation (APC) is a non-contact thermal method of hemostasis that has generated much attention and excitement in recent years. It was introduced as an alternative to contact thermal coagulation (heater probe and bipolar cautery) and to existing non-contact technologies (primarily laser). The theoretical advantages of APC include its ease of application, speedy treatment of multiple lesions in the case of angiodysplasias or wide areas (the base of resected polyps or tumor bleeding), safety due to reduced depth of penetration, and lower cost compared to laser.
This topic will review argon plasma coagulation, including how it is used and its efficacy. The general management of adult patients with upper and lower gastrointestinal bleeding, as well as a detailed discussion of angiodysplasia of the gastrointestinal tract are discussed elsewhere. (See "Approach to acute upper gastrointestinal bleeding in adults" and "Approach to acute lower gastrointestinal bleeding in adults" and "Angiodysplasia of the gastrointestinal tract".)
WHAT IS APC?
Contrary to a common misconception, argon plasma coagulation (APC) is not a laser. This technology uses argon gas to deliver plasma of evenly distributed thermal energy to a field of tissue adjacent to the probe. A high voltage spark is delivered at the tip of the probe that ionizes the argon gas as it is sprayed from the probe tip in the direction of the target tissue. Argon gas is non-flammable and inexpensive to refill. It is easily ionized by the 6000 volt peak energy delivered by the tungsten wire that terminates just proximal to the probe tip. This ionized gas or plasma then seeks a ground in the nearest tissue, delivering the thermal energy with a depth of penetration of roughly 2 to 3 mm. The plasma coagulates both linearly and tangentially. By delivering energy to all tissue near the probe tip, APC can be used to treat a lesion around a fold and not clearly in view or a lesion that cannot be positioned directly in front of the endoscope.
A similar technology has been used for many years by surgeons in the operating room, particularly during hepatic surgery, as a means of spray coagulation to control superficial, diffuse bleeding. In the early 1990s, special probes were developed by the ERBE Corp. to allow this technology to be applied to flexible endoscopy. The disposable probes are available with diameters of 1.5 mm, 2.3 mm (the most commonly used size), and 3.2 mm. The standard probes are 220 cm long (picture 1); 300 cm probes can be specially ordered for use during push enteroscopy.
In addition to the probe, the equipment consists of an electrosurgical generator that comes on a cart along with the argon plasma coagulator, a foot pedal, and two tanks of argon gas. Both the argon flow rate and the wattage delivered per pulse are easily adjusted by pressing buttons on the control panel. Newer models of this cart will include a water pump.