Argon plasma coagulator: "primum non nocere"

Abstract

More than 10 years ago I wondered whether argon plasma coagulation (APC) would prove revolutionary for therapeutic endoscopy (1). Now, time has settled the question. We now know that APC sources are essential in all endoscopy units around the world, but their use is basically restricted to hemostatic procedures. Ablative applications have been relegated to mere "touch-ups" to finish off other techniques, which today anew seem revolutionary.APC has also evolved, and second-generation sources are now available that provide several application modes: forced, pulsed, and precise, with various coagulation effects (2).The forced modality is characterized by continuous monopolar current, which is delivered to the target tissue through a conductive flow of ionized argon gas (argon plasma), and represents the energy dispensed by present-day sources. In pulsed mode discontinuous current is delivered to provide one of two effects: effect one with higher intensity current and longer pauses, and effect two with a higher number of lower-energy pulses. Finally, with the precise mode argon plasma may be regulated using an electronic setup regardless of system impedance and target distance, provided the latter is shorter than 5 mm (3). The effectiveness of second-generation APC is 50% higher than that of original generators (4).The primary benefit attributed to argon plasma is its capability to cause limited damage in superficial layers, since current moves from treated, dried-up areas with a higher resistance to untreated areas with a lower resistance, with this drift protecting patients from potential perforation by deep burns (5,6). In contrast, more recent studies in experimental models show significant damage to the muscularis propria with severity increasing with dispensed energy amount, pulse duration, and target area; the layer is hit by 86% of 40W shots or 69% of applications longer than 5 seconds using both traditional (7) or second-generation sources (8), the latter requiring greater caution given their increased energetic yield by nearly 50%.Obviously, continuous gas flow during delivery results in gastrointestinal tract distension and patient discomfort, an adverse effect that may be easily countered by repeat aspirations during therapy pauses.The most devastating, feared effect is no doubt a deflagration of inflammable gases within the colon. This is why patients scheduled to undergo argon plasma therapy must be fully prepared in an anterograde manner using a sugar-free solution regardless of the target area for APC. Just because actinic proctitis is the condition to be treated, as is the case with Tormo et al. (9), it does not mean that full preparation (using phosphates in our case) to prevent gases from exploding may be overlooked.Argon plasma coagulator -"primum non nocere"