Optimal Freeze Cycle Length for Renal Cryotherapy

• Published in: The Journal of urology Vol. 186; no. 1; pp. 283 - 288
• Main Authors: Young, Jennifer Lee, Khanifar, Elham, Narula, Navneet, Ortiz-Vanderdys, Cervando Gerardo, Kolla, Surendra Babu, Pick, Donald Lowell, Sountoulides, Petros George, Kaufmann, Oskar Grau, Osann, Kathryn Elizabeth, Huynh, Victor Buu, Kaplan, Adam Geoffrey, Andrade, Lorena Aurora, Louie, Michael Ken, McDougall, Elspeth Marguerita, Clayman, Ralph Victor
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.07.2011; Elsevier
• Subjects: Animals; Biological and medical sciences; cryosurgery; Cryosurgery - methods; Female; kidney; laparoscopy; Medical sciences; necrosis; Nephrectomy - methods; Nephrology. Urinary tract diseases; Swine; Time Factors; Urology; laparoscopy; swine; kidney; TTC; triphenyl tetrazolium chloride; necrosis; cryosurgery; Nephrology; Cryosurgery; Laparoscopy; Freezing; Cycle; Kidney; Urology; Necrosis; Vertebrata; Mammalia; Treatment; Urinary system; Length; Swine; Surgery; Animal; Artiodactyla; Endoscopy; Cryotherapy; Ungulata; Freeze
• ISSN: 0022-5347; 1527-3792
• DOI: 10.1016/j.juro.2011.03.034

Purpose To our knowledge the optimal freeze cycle length in renal cryotherapy is unknown. Ten-minute time based freeze cycles were compared to temperature based freeze cycles to −20C. Materials and Methods Laparoscopic renal cryotherapy was performed on 16 swine. Time based trials consisted of a double 10-minute freeze separated by a 5-minute thaw. Temperature based trials were double cycles of 1, 5 or 10-minute freeze initiated after 1 of 4 sensors indicated −20C. A 5-minute active thaw was used between freeze cycles. Control trials consisted of cryoneedle placement for 25 minutes without freeze or thaw. Viability staining and histological analysis were done. Results There was no difference in cellular necrosis between any of the temperature based freeze cycles (p = 0.1). Time based freeze cycles showed more nuclear pyknosis, indicative of necrosis, than the 3 experimental freeze cycles for the renal cortex (p = 0.05) but not for the renal medulla (p = 0.61). Mean time to −20C for freeze cycle 1 was 19 minutes 10 seconds (range 9 to 46 minutes). In 4 of 21 trials (19%) −20C was never attained despite freezing for 25 to 63 minutes. Conclusions There was no difference in immediate cellular necrosis among double 1, 5 or 10-minute freeze cycles. Cellular necrosis was evident on histological analysis for trials in which −20C was attained and in freeze cycles based on time alone. With a standard 10-minute cryoablation period most treated parenchyma 1 cm from the probe never attained −20C. Cell death appeared to occur at temperatures warmer than −20C during renal cryotherapy.