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EP185 Relative effects of various factors on ice ball formation and ablation zone during ultrasound-guided percutaneous cryoneurolysis
  1. Engy Said1,
  2. Brennan Marsh-Amstrong2,
  3. Preetham Suresh2,
  4. Matthew Swisher2,
  5. Andrea Trescot3,
  6. J David Prologo4,
  7. Baharin Abdullah2 and
  8. Brian Ilfeld2
  1. 1UC San Diego, San Diego, USA
  2. 2UC San Diego, San Diego, USA
  3. 3Florida Pain Relief Group, Tampa, FL, USA, Tampa, USA
  4. 4Department of Radiology, Emory University, Atlanta, GA, USA, Atlanta, USA


Background and Aims Ultrasound-guided percutaneous cryoneurolysis provides analgesia using cold temperatures to reversibly ablate peripheral nerves. Cryoneurolysis probes pass a gas through a small internal annulus, rapidly lowering pressure and temperature, and forming an ice ball to envelope the target nerve. Analgesia is compromised if a nerve is inadequately frozen, and laboratory studies suggest that pain may be paradoxically induced with a magnitude and duration in proportion with incomplete ablation.

Methods A cryoprobe (PainBlocker, Epimed International, Dallas, Texas) was inserted into a piece of meat, a gas passed through for 2 minutes, and resulting ice ball width (cross-section) and length (parallel axis) measured using ultrasound with temperature evaluated in 9 concentric locations concurrently.

Results Greatest influence on ice ball size was probe gauge: change from 18 to 14 increased ice ball width, length, and volume by up to 70%, 113%, and 512%, respectively, with minimum internal temperature decreasing as much as from -5°C to -32°C. In contrast, alternating the type of meat (chicken, beef, pork) and the shape of the probe tip (straight, Coude) effected ice ball dimensions to a negligible degree. Ice ball dimensions and the zone of adequate temperature drop were not always correlated, and even within a visualized ice ball the temperature was often inadequate to induce Wallerian degeneration.

Abstract EP185 Table 1

Factors and ice ball dimensions as well as minimum temperature. The lowest temperatures at the tip of the probes are presented, with minimum temperatures higher than -20°C denoted in red

Conclusions Percutaneous probe design can significantly influence the effective cryoneurolysis zone; visualizing a nerve fully encompassed in an ice ball does not guarantee adequate treatment to induce desired Wallerian degeneration. How specific temperatures transfer from pieces of meat to the human body remains unknown.

  • cryoneurolysis
  • acute postoperative pain

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