The necrotizing effect of pulse cryocycling on liver tissue.
OBJECTIVE
Repeated cycles of freezing improve the necrotizing effect of cryosurgery. We investigated whether multiple, very short periods of freezing and thawing (pulse cryocycling) enlarged the area of cell cryonecrosis within the iceball, compared with the standard method of cryocycling.


METHODS
Liver cryonecrosis was produced in 3 groups of rabbits by means of 2 cycles of 5-minute freezing processes, each followed by 5 minutes of spontaneous thawing. In the control group (group 1), the freezing periods were uninterrupted. In the pulse cryocycling groups, the freezing periods consisted of repeated episodes of freezing and active thawing of 15 seconds (group 2) or 30 seconds (group 3) each. The edges of all lesions were visually marked. The correlation between marking and borders of the cryolesion were examined ultrasonographically. All animals were killed on the following day, and the liver was harvested and examined histologically.


METHODS
Animal experimental laboratory.


RESULTS
Complete liver cell demise was observed up to the edge of the cryolesions in all 3 groups of animals. However, a thin, sharply bounded intermediate zone of incomplete tissue destruction was observed at the border of the cryolesions, which was relatively thicker in group 2.


CONCLUSIONS
In our study, pulse cryocycling had no advantage compared with regular cryocycling, which obtained optimal results in normal liver tissue. However, compared with the 30-second cycles, the 15-second pulse cycling yielded poorer results.
Department of Surgery B, Haemek Medical Center, Haifa, Israel.
Doron
D
Kopelman
Gregory
G
Shpoliansky
Ofer
O
Ben-Izhak
Assaf
A
Zaretzki
Rona
R
Shofti
Diana
D
Gaitini
Moshe
M
Hashmonai
D000818:Animals; D003452:Cryosurgery / Q000009:adverse effects*; D005260:Female; D008099:Liver / Q000473:pathology* / Q000601:surgery*; D009336:Necrosis; D011817:Rabbits