title: Optimal freeze cycle length for renal cryotherapy.
abstract: OBJECTIVE
  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.
  
  
  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.
authors: Department of Urology, University of California-Irvine, Orange, California, USA. jlyoung@uci.edu
authors: Jennifer Lee
authors: JL
authors: Young
authors: Elham
authors: E
authors: Khanifar
authors: Navneet
authors: N
authors: Narula
authors: Cervando Gerardo
authors: CG
authors: Ortiz-Vanderdys
authors: Surendra Babu
authors: SB
authors: Kolla
authors: Donald Lowell
authors: DL
authors: Pick
authors: Petros George
authors: PG
authors: Sountoulides
authors: Oskar Grau
authors: OG
authors: Kaufmann
authors: Kathryn Elizabeth
authors: KE
authors: Osann
authors: Victor Buu
authors: VB
authors: Huynh
authors: Adam Geoffrey
authors: AG
authors: Kaplan
authors: Lorena Aurora
authors: LA
authors: Andrade
authors: Michael Ken
authors: MK
authors: Louie
authors: Elspeth Marguerita
authors: EM
authors: McDougall
authors: Ralph Victor
authors: RV
authors: Clayman
references: J Urol. 2005 Jun;173(6):1889-92
references: 15879769
references: Urology. 1996 May;47(5):772-6
references: 8650885
references: J Endourol. 2001 Mar;15(2):193-7
references: 11325092
references: J Urol. 1998 Apr;159(4):1370-4
references: 9507886
references: Int J Urol. 2001 Sep;8(9):473-7
references: 11683965
references: J Urol. 2004 Sep;172(3):863-6
references: 15310984
references: Urology. 1998 Feb;51(2):203-5
references: 9495698
references: Urology. 2004 Jul;64(1):49-52
references: 15245934
references: J Urol. 2006 Dec;176(6 Pt 1):2391-5; discussion 2395-6
references: 17085108
references: J Endourol. 1999 May;13(4):233-9
references: 10405898
references: J Endourol. 2000 Mar;14(2):139-43
references: 10772505
references: Cancer. 2004 Feb 15;100(4):738-45
references: 14770429
references: J Urol. 2006 Aug;176(2):784-6
references: 16813947
references: J Endourol. 2002 Sep;16(7):519-22
references: 12396446
references: J Urol. 2005 Jun;173(6):1903-7
references: 15879772
references: J Urol. 2006 Feb;175(2):425-31
references: 16406965
references: Cryobiology. 1998 Nov;37(3):171-86
references: 9787063
references: Urology. 2002 Jun;59(6):816-20
references: 12031359
references: J Urol. 2008 Apr;179(4):1227-33; discussion 1233-4
references: 18280512
references: J Urol. 2009 Oct;182(4):1271-9
references: 19683266
references: Am Heart J. 1981 May;101(5):593-600
references: 6164281
references: J Endourol. 2006 Dec;20(12):1101-5
references: 17206911
references: J Urol. 2008 Feb;179(2):468-71; discussion 472-3
references: 18076931
references: Urology. 2006 Oct;68(4):737-40
references: 17070344
references: Physiology (Bethesda). 2006 Jun;21:171-80
references: 16714475
references: Br J Urol. 1995 Feb;75(2):132-6; discussion 136-7
references: 7850315
references: Cryobiology. 1999 Feb;38(1):89-93
references: 10079133
references: J Urol. 1999 Dec;162(6):1930-3
references: 10569540