Fluid cushion protects against thermal damage during argon plasma coagulation

Abstract

Background: Thermal damage to the muscle layer during mucosal application of argon plasma coagulation (APC) may be avoided by creating a fluid cushion within the submucosal layer, but the minimum injection volume needed or the ideal injection fluid are yet to be established. We conducted a systematic ex vivo study with this aim.

Methods: All experiments were performed in an ex vivo porcine gastrointestinal tract model. Five different fluids (saline, Glyceol, Gelafundin, Voluven, and Eleview) of different volumes were injected into the submucosa of different parts of the gastrointestinal tract. APC was applied to the mucosa at different power settings. Immediately after APC treatment, the temperature was measured through a thermocouple placed inside the fluid cushion, just on top of the muscle layer. The minimum volume of fluid needed to protect the muscle layer from thermal damage was determined.

Results: There was no difference in the temperature measured among the different injection fluids at the surface of the muscle, in all the locations, at equal injection volumes and power settings. The minimum amounts of fluid needed to protect the muscle layer were 2 and 3 mL for power settings of 30-90 W and 90-120 W, respectively.

Conclusions: Normal saline and 4 commercially available submucosal injection fluids possess similar thermal protective effects. To reduce the likelihood of thermal damage to deeper layers when APC is applied, a minimum injection volume of 3 mL is recommended if less than 90 W power will be utilized over 3 sec.

Keywords: Argon plasma coagulation; ablation; endoscopy; submucosal injection.

Figure 1

Injection of NaCl 0.9% vs. Glyceol in stomach (fundus). Injected with 23-G cannula. Volume 5 mL each APC, argon plasma coagulation

Figure 2

Argon plasma coagulation (APC): Top view (A) and sectional view (B): Stomach (corpus); Injection solution: Gelafundin, 5 mL; APC: Forced APC, 50 W, Flow (Ar) 1 L/min; t=2 sec, Distance 3 mm

Figure 3

Experimental setup for measurement of temperature inside the protective fluid cushion on top of the muscle layer

Figure 4

Comparison of the final temperature of the fluid cushion in stomach (A), rectum (B) and esophagus (C), using normal saline as injection fluid with different initial tissue temperatures (blue 25°C, red 37°C) at different settings of electrical power (30, 60 and 90 W). The temperatures shown are mean values from measurements with injection volumes of 0, 1 and 2 mL

Figure 5

Esophagus temperature inside the fluid cushion after 3 sec of PULSED argon plasma coagulation E2 using power settings 30, 60, 90 and 120 W and different injection volumes (0-5 mL). The initial temperature of the tissue was 25°C

Figure 6

Stomach temperature inside the fluid cushion after 3 sec of PULSED argon plasma coagulation E2 using power settings 30, 60, 90 and 120 W and different injection volumes (0-5 mL). The initial temperature of the tissue was 25°C

Figure 7

Rectum temperature inside the fluid cushion after 3 sec of PULSED argon plasma coagulation E2 using power settings 30, 60, 90 and 120 W and different injection volumes (0-5 mL). The initial temperature of the tissue was 25°C