Background and Objectives Emphasis has been placed on methods to enlarge monopolar radiofrequency (RF) lesion size for pain management. Ex vivo research has suggested that fluid modulation may be an effective method to enlarge lesion zone. To date, these findings have not been confirmed in vivo. The purpose of this study was to determine the effect of hypertonic saline on in vivo lesion size through both histological and magnetic resonance imaging (MRI) analysis. A secondary purpose was to validate in vivo characterization of RF lesions using contrast-enhanced MRI.
Methods Monopolar RF was performed in an in vivo porcine model in 3 groups: (1) without fluid preinjection, (2) with preinjection of 1% lidocaine, or (3) with preinjection of 1% lidocaine and 8% sodium chloride. Following lesioning, MRI processing with gadolinium-enhanced, T1-weighted imaging and histological analysis was performed.
Results The addition of 8% sodium chloride significantly increased the size of RF lesion in comparison to the addition of 1% lidocaine alone and to the absence of fluid injection, as assessed by histological and MRI analysis. Three distinct histological lesion zones were identified. In comparison to the no-fluid group, the addition of hypertonic saline significantly altered the shape and histological composition of the lesion. There was a significant correlation of lesion volume as assessed by MRI and by histology measurements. Peak power and total energy delivery also correlated with lesion size.
Conclusions This study validates the ability of hypertonic saline to increase in vivo RF lesion size. With further refinement, MRI may be a viable method to assess RF lesion size.
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This study was supported by Medtronic. This study was conducted at the Medtronic Physiological Research Laboratory. Medtronic PLC provided funding for animal acquisition and supplies. No monetary compensation was provided to any of the investigators for their participation in this nonclinical research.
This work was presented in part at the American Academy of Pain Medicine 33th Annual Meeting, Orlando, FL, April 2017; and the American Society of Regional Anesthesia and Pain Medicine 15th Annual Meeting, San Diego, CA, November 2016.
D.A.P. is a consultant for Bioness, Boston Scientific, Halyard, Medtronic, Nevro, Sollis, and Abbott. He receives research support from Medtronic and Abbott. D.A.P. received no funding or reimbursement for his work on this project. J.T.W. is an employee of Medtronic. E.R.C. is an employee of Boston Scientific. Cosman Medical is a wholly owned subsidiary of Boston Scientific.