Background and Objectives: Previous ex vivo studies on monopolar radiofrequency have not incorporated the preinjection of fluid before radiofrequency ablation into study design. The objective of this study was to investigate the effects of the preinjection of small volumes of different fluids on lesion dimensions.

Methods: Monopolar radiofrequency lesioning with temperature control at 80°C for 90 secs in ex vivo chicken samples with 100-mm, 18-gauge cannulas and 10-mm active tips was performed with 1 reference group without fluid injection and 4 comparison groups with 0.5 mL of volumes of sterile water, 0.9% sodium chloride, 1% lidocaine, or 6% hydroxyethyl starch injected before ablation. A fifth comparison group of 3 mL of 0.9% sodium chloride was used to evaluate the influence of increased volume. Lesions were measured in horizontal diameter, vertical diameter, maximal effective radius, and distal radius from the tip of electrode.

Results: Injecting fluid before lesioning led to larger lesion size parameters (P < 0.01) for the 5 comparison groups relative to control; 6% hydroxyethyl starch produced the largest size and shape parameters, which were statistically significant (P ≤ 0.017) for all measurements compared with control and water.

Conclusions: The influence of the composition of the preinjected fluid should be considered for monopolar radiofrequency ablation. This ex vivo study revealed a simple method to increase monopolar radiofrequency lesion size. Future research is needed to determine the degree of influence of the composition of the fluid on thermal and electrical conductivity.