A comparative laboratory study of liquid nitrogen and argon gas cryosurgery
Hewitt PM, Zhao J, Akhter J, Morris DL.
Department of Surgery, University of New South Wales,
St. George Hospital, Kogarah, Sydney, Australia.
Cryotherapy can now be applied using a variety of
delivery systems and cryogens. We compared the Cryotech LCS 3000
liquid nitrogen system (Spembly, Andover, UK) with the CRYOcare
argon gas-based system (Irvine, CA, U.S.A.) using three different
3-mm cryoprobes: an old liquid nitrogen probe (N-probe), a new N-probe
featuring gas bypass and an argon gas probe. Each probe was tested
in two models: (i) fresh sheep liver at 20 degrees C--the probe
was inserted to a depth of 1.5 cm; the rate of ice ball formation
was monitored by recording radial temperatures every 15 s at 5,
10, 15, and 20 mm from the cryoprobe, and the ice-ball diameter
was measured every 2.5 min. After 10 min, the probe was warmed and
the time taken until it could be extracted from the liver was recorded.
(ii) Warm water bath--the probe was immersed in warm water (42 degrees
C) for 15 min and the ice-ball diameter was measured at 5-min intervals.
Radial temperatures in liver declined more rapidly (P < 0.001)
and time to probe extraction was less (P < 0.01) when the argon
gas system was used. The new N-probe performed better than its older
counterpart, but was still slower than the argon gas system. In
liver (20 degrees C), ice-ball diameters were similar after 10 min,
but in warm water, they were larger when the new N-probe was used
(P < 0.02). It would appear that the argon gas system is initially
PMID: 9425653 [PubMed - indexed for MEDLINE]