Elsevier

Urology

Volume 79, Issue 2, February 2012, Pages 484.e1-484.e6
Urology

Basic and Translational Science
Are Multiple Cryoprobes Additive or Synergistic in Renal Cryotherapy?

https://doi.org/10.1016/j.urology.2011.10.042Get rights and content

Objective

To investigate the relationship between multiple cryoprobes was investigated to determine whether they work in an additive or synergistic fashion in an in vivo animal model because 1.47 mm (17-gauge) cryoprobes have been introduced to the armamentarium for renal cryotherapy.

Methods

Laparoscopic-guided percutaneous cryoablation was performed in both renal poles of 3 pigs using 3 IceRod cryoprobes. These 12 cryolesions were compared with 12 cryolesions using a single IceRod cryoprobe. Each cycle consisted of two 10-minute freeze cycles separated by a 5-minute thaw. The iceball volume was measured using intraoperative ultrasonography. The kidneys were harvested, and cryolesion surface area was calculated. The lesions were fixed and excised to obtain a volume measurement. Statistical analysis was used to compare the single probe results multiplied by 3 to the multiple probe group for iceball volume, cryolesion surface area, and cryolesion volume.

Results

The iceball volume for the first freeze cycle for the single cryoprobe multiplied by 3 was 8.55 cm3 compared with 9.79 cm3 for the multiple cryoprobe group (P = .44) and 10.01 cm3 versus 16.58 cm3 for the second freeze (P = .03). The cryolesion volume for the single cryoprobe multiplied by 3 was 11.29 cm3 versus 14.75 cm3 for the multiple cyroprobe group (P = .06). The gross cryolesion surface area for the single cryoprobe multiplied by 3 was 13.14 cm2 versus 13.89 cm2 for the multiple probe group (P = .52).

Conclusion

The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be larger than that of an additive effect. The lesions were significantly larger as measured by ultrasonography and nearly so (P = .06) as measured by the gross cryolesion volume.

Section snippets

Material and Methods

Three female Yorkshire farm pigs weighing 39-42 kg were used in the present study, which was approved by the institutional animal care and use committee. After premedication with intramuscular 0.05 mg/kg atropine, anesthesia was induced with intramuscular 6 mg/kg telazol and 2 mg/kg xylazine. An ear vein cannula was placed and the pig intubated. Anesthesia was induced with 4%-5% isoflurane and maintained at 1%-2%. The pigs were placed in the left lateral decubitus position and insufflated with

Results

Cryolesions were created in the upper and lower pole of both kidneys in all 3 pigs. No intraoperative complications or deaths occurred. The mean operating time was 3.6 hours for the single probe group and 3.3 hours for the multiple probe group. Each single probe trial was multiplied by 3 to compare the results of a single probe multiplied by 3 (additive arm) with the results for the 3 probes activated simultaneously (synergistic arm). In the single probe group multiplied by 3, the average

Comment

Three-dimensional numeric simulations of multiple 1.47 mm (17-gauge) cryoprobes were matched with experimental data in a phase-changing gel by Magalov et al.13 They found additional cryoprobes resulted in an increased expansion of the isotherm in all 3 directions and cited this as clear evidence of the synergistic effect of multiple cryoprobes. They found the effect of different placement decreased as the density of the probes increased. They cautioned against placing the probes too close

Conclusions

The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be synergistic rather than additive. The lesions created by 3 simultaneously activated cryoprobes 1-cm apart were significantly larger as measured by ultrasonography. Moreover, the gross cryolesion volume showed a trend for being larger (P = .06).

References (25)

Cited by (16)

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Financial Disclosure: BK Medical provided the use of an ultrasound machine and laparoscopic ultrasound probe for the study. Department of Urology, University of California, Irvine, provided the use of the Atellas Education Center as a study site, including laparoscopic surgical equipment, preoperative animal housing, and animal disposal.

Funding Support: Galil Medical, Inc. provided financial support and the use of a PresIce cryotherapy machine and IceRods for the study.

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