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Liquid Nitrogen may be carefully poured into the bottle (slowly when warm) or by any standard pressure withdrawal device
from a Liquid Nitrogen Storage Dewar.
It is recommended that for a 3 - 6-hour duration of intermittent use that the Cryosurgical Unit be 70% filled. Fill enough
fluid to allow for completion of the cryosurgical procedure.
Before replacing the top, ensure that the rubber gasket is still in place inside the cap. If it is missing the Cryosurgical Unit
may not pressurize correctly and the top may become stuck. In this event the Cryosurgical Unit must be returned to an
Authorized Repair Center for proper removal.
After filling a warm Cryosurgical Unit, allow 30 to 60 seconds for the initial boiling of the Liquid Nitrogen to subside before
attempting to replace the top. If a large number of cryosurgery procedures are scheduled, the reservoir of Liquid Nitrogen
may be topped off after the first boiling, and the unit has cooled off.
Caution - To refill a Cryosurgical Unit after it has been in use you must ensure that the unit is depressurized
before removing the top.
To Depressurize the Cryosurgical Unit, unscrew the top a quarter to half turn only. The pressurized gas inside
will begin to vent from the hole situated in front of the Valve Body. Once the hissing has stopped the top can be
unscrewed and removed.
5. Liquid Nitrogen (LN2)
Liquid Nitrogen is an extremely cold substance, i.e. –196
o
C, and should be treated with extreme caution at all times. For
full details regarding Liquid Nitrogen you should contact your supplier of Liquid Nitrogen and obtain a copy of the Material
Safety Data Sheet (MSDS).
The physician should always maintain a clean supply of Liquid Nitrogen. To help ensure the Liquid Nitrogen remains free
of particulate matter, such as ice crystals, carbon dioxide slush, lint, etc., the storage Dewar used should be completely
emptied at least 4 times a year just prior to having it refilled. This is accomplished by vigorously agitating the residual
amount of Liquid Nitrogen in the Dewar and discarding it in a safe, outdoor area.
6. Suggested Temperature Settings and Freeze Times for Apertures
The tables below provide suggested freeze times to reach a depth of freeze of 1 – 2 mm and a temperature of -
40
o
C when used at a distance of 2.54 cm (1 inch) from the skin.
Depth of Freeze Recommended
Aperture A (0.04 in) 1 mm 3 – 4 seconds
2 mm 4 – 6 seconds
Aperture D (0.0164 in) 1 mm 11 – 14 seconds
2 mm 19 – 25 seconds
The apertures should not be used if there are visible cracks or chips on the surface of the device.
7. Instructions for Use of Probes
Probes are used with Cry-Ac’s which is a Hand-Held Cryosurgical Device for the controlled dispensing of
Liquid Nitrogen.
7.1 Warnings and Cautions:
a. Extreme care must be taken to properly direct the silicone vent tube which is attached to the base of the
probe. This tube will harden after approximately five (5) seconds and remain in a fixed position during
the remainder of the procedure.
b. It is imperative that they be pointed is a safe position away from the patient and the user at the onset of
the procedure.
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