Aims
Saline-immersion therapeutic endoscopy (SITE) enhances visualization andhemostasis, but it alters electrosurgical behavior due to the high conductivity of saline, whichreduces tissue impedance and voltage stability. These effects may vary depending on the knifesize, as electrode diameter influences current density.
Methods
An ex-vivo porcine gastric mucosa model was used to compare three electrosurgicalknives with different sizes, namely one with a thick electrode (HybridKnife® T-Type, 1.5 mm), andtwo with thin electrodes (HYBRIDKnife® flex I-Type, 0.5 mm; DualKnife J-Type, 0.4 mm). This wasperformed in air and under saline across seven electrosurgical modes (2 cutting, 3 coagulation and2 dissection modes). Electrical parameters (impedance, peak voltage, power output), cuttingsuccess, and lateral thermal spread, were measured during 252 standardized incisions. Statisticalanalysis was performed using both univariate and multivariate methods.
Results
The average decrease in impedance when passing from air to saline immersion washigher for thick as compared with thin knives (92% vs. 55%, p<0.001) across multiple modes.Corresponding increase in power was also higher for thick (up to 19-fold) than for thin (up to 5-fold,p<0.001) knives, while peak voltage decreased by 30% for thick knives and increased by 2% forthin knives (p<0.001). Cutting success decreased from 57% (CO 2 ) to 43% (SITE) with the thickknife (p=0.28), but it remained ≥71 % for thin knives. Lateral thermal spread increased from <1 mmin CO 2 to 1.35 mm (256%) in saline for the thick knife, while it was ≤0.8 mm (71%) for thin knives(p<0.001, between thin and thick knives), irrespective of the setting. Electrode diameter and salineimmersion were the strongest independent predictors of lateral spread (β = 0.469 and 0.353,respectively; both p < 0.001).
Conclusions
The effect of saline immersion on impedance and voltage is dramatically higher whenusing thicker compared to thinner knives. This explains the differing tissue effects observed withvarying electrode sizes in third-space endoscopy.