Background The effect of preinjected fluid on bipolar radiofrequency (RF) lesion characteristics has not been investigated with conventional pain medicine equipment. The purpose of the present study was to determine the effect of preinjected fluid composition on lesion parameters.

Methods Bipolar RF lesioning was performed in ex vivo chicken samples without fluid preinjection or with 0.7 mL of fluid injected through the 2 RF cannulas (total volume, 1.4 mL). The preinjected fluids were sterile water, 0.9% NaCl, 3% NaCl, 1% lidocaine, and 6% hydroxyethyl starch (HES). For each condition, RF electrodes were incrementally separated, and the number of trials producing successful lesions was recorded. Maximum and minimum height, length, and depth of the lesions were measured, and volumes of the lesions were calculated.

Results The preinjection of any fluid increased the odds of consistently achieving a continuous lesion between the electrodes that was at least 75% of the maximal height of tissue damaged; 3% NaCl increased the odds of achieving at least 75% maximum height significantly more than any other fluid except for HES. Injection of any fluid containing NaCl (including lidocaine and HES) significantly increased the mean volume of tissue lesioned over that observed with injection of water.

Conclusions Fluid composition influences success, alters lesion size, and could be an appropriate consideration when selecting treatment parameters for bipolar RF. The enhanced lesion size and improved odds of producing a successful lesion with increasing NaCl concentration suggest a method to enlarge lesion size in a controlled manner.