Influence of NaCl concentrations on coagulation, temperature, and electrical conductivity using a perfusion radiofrequency ablation system: an ex vivo experimental study.

Purpose: To determine, by means of an ex vivo study, the effect of different NaCl concentrations on the extent of coagulation obtained during radiofrequency (RF) ablation performed using a digitally controlled perfusion device.

Method: Twenty-eight RF ablations were performed with 40 W for 10 min using continuous NaCl infusion in fresh excised bovine liver. For perfusion, NaCl concentrations ranging from 0 (demineralized water) to 25% were used. Temperature, the amount of energy, and the dimensions of thermal-induced white coagulation were assessed for each ablation. These parameters were compared using the nonparametric Mann-Whitney test. Correlations were calculated according to the Spearman test.

Results: RF ablation performed with 0.9% to 25% concentrations of NaCl produced a mean volume of coagulation of 30.7 +/- 3.8 cm(3), with a mean short-axis diameter of 3.6 +/- 0.2 cm. The mean amount of energy was 21,895 +/- 1,674 W and the mean temperature was 85.4 +/- 12.8 degrees C. Volume of coagulation, short-axis diameter, and amount of energy did not differ significantly among NaCl concentrations (p > 0.5). A correlation was found between the NaCl concentration and the short-axis diameter of coagulation (r = 0.64) and between the NaCl concentration and the mean temperature (r = 0.67), but not between the NaCl concentration and volume of coagulation.

Conclusion: In an ex vivo model, continuous perfusion with high NaCl concentrations does not significantly improve the volume of thermal-induced coagulation. This may be because the use of a low-power generator cannot sufficiently exploit the potential advantage of better tissue conductivity provided by NaCl perfusion.