Abstract
Background
Thermal damage to the muscle layer of the gastrointestinal wall can occur during mucosal application of argon plasma coagulation (APC). This injury may be mitigated by creating a fluid cushion within the submucosal layer that physically separates the mucosa from the muscle layer and suppresses unwanted tissue temperature elevation. This in turn protects the muscle layer from thermal damage. The coagulative threshold of muscle proteins is known to be about 60°C, but there are no published systematic assessments of the minimum injection volume needed nor the ideal injectate to prevent thermal damage to the muscle layer during mucosal APC ablation.
Aims
Our aims were, firstly, to measure the final temperature inside the fluid cushion after mucosal ablation with APC and then to determine any differences in the final temperature between various injectable solutions. Secondly, we sought to determine the minimum volume of injectate required to protect the muscle layer from thermal damage.
Methods
All experiments were performed in an ex-vivo porcine gastrointestinal tract model. Five different fluids (normal saline, Glyceol, Gelafundin, Voluven and Eleview) of different volumes (range 0 - 5mL) were injected into the submucosa of the esophagus, stomach (fundus) and rectum to create a fluid cushion. APC was applied to the mucosa for a fixed duration (3s) at different power settings (ranging from 30 - 120W). Immediately after APC treatment, the final temperature was measured by placing a contact thermometer inside the fluid cushion, just on top of the muscle layer.
Results
There was no significant difference in the temperature measured at the surface of the muscle layer between elevation with normal saline, Glyceol, Gelafundin, Voluven and Eleview at all 3 tissue locations at equal injection volumes and power settings. The experiments showed that the temperature rose for each injectate with heightened power settings but also decreased with increasing volume of injected fluid. The minimum amount of fluid needed to protect the muscle layer from thermal damage was 2mL for the esophagus, stomach and rectum in the case of a power setting between 30 to 90W and 3mL in the case of 90 to 120W.
Conclusions
Normal saline and four commercially available submucosal injectates possess similar thermoregulatory effects as an insulator of the muscle layer during APC treatment. As opposed to the choice of injectate or anatomic location treated, the volume of fluid injected is the main determinant of the final temperature at the level of the muscularis propria. To reduce the likelihood of thermal damage to deeper layers of the GI tract when APC is applied, a minimum injection volume of 2mL is recommended if <90W of power is utilized.
Funding Agencies
None
Submucosal Injection of Normal Saline can Prevent Unexpected Deep Thermal Injury of Argon Plasma Coagulation in thein vivoPorcine Stomach